ML102871145

7.8 Excessive Water Jet Pressure Part 1

ML102871145
Person / Time
Site:	Crystal River
Issue date:	02/18/2010
From:	- No Known Affiliation
To:	Office of Information Services
References
FOIA/PA-2010-0116
Download: ML102871145 (34)

Text

A 7.8 Excessive Water Jet Pressure

==

Description:==

During hydro-blasting, a high-pressure water jet impacts the concrete to be removed (FM 7.8 Exhibit 1 is a September 2004 International Concrete Repair Institute.(ICRI) Technical Guideline "Guide for the Preparation of Concrete Surfaces for Repair Using Hydro-demolition Methods" and FM 7.8 Exhibit 2 is the ACI 546R-04 Concrete Repair Guide). The water jet pressure that is used is nominally 20,000 psi (FM 7.8 Exhibit 3 is the Work Plan agreed by Mac & Mac, the hydro-blasting company used for this project, and Progress Energy, the owner) although in practice it can vary somewhat (FM 7.8 Exhibit 4 is an interview with Dave McNeill, co-owner of Mac & Mac and FM 7.8 Exhibit 5 is an interview of Robert Nittinger, President of American Hydro). The pressure is obtained by means of a plunger positive displacement pump. The water nozzles rotate at 500 rpm. The jet flow rate per nozzle is around 50 gallons per minute.

The intent of hydro-demolition as applied here is to damage and remove the concrete section of interest. This is indeed the point of using this technology in this particular application where concrete HAS to be removed. This FM is looking at if and how the hydro pressure might cause damage beyond the application area via force or pressure buildup.

Damage to underlying or surrounding concrete (outside the targeted removal area) may occur if water jet pressure and flow is not maintained within a controllable range.

Note that issues associated with resonant frequency are analyzed separately in FM 7.2.

Data to be collected and Analyzed:

1. Determine impulse force associated with the hydro-blasting technology (FM 7.8 Exhibit 7 is a vibration analysis performed by P11, and FM 7.8 Exhibit 8 is a calculation performed by American Hydro);

2. Observations of phenomena that may be related to impact from the water jets (FM 7.8 Exhibit 9 describes observations made at 2/18/10 P1 , fidential, 2u09 Page 1 of 3 Dr asston

the CR3 containment near the liner);

3. Review of the Turkey Point liner issues during its concrete containment opening (FM 7.8 Exhibit 10 is a report summary of the issues observed at Turkey Point during concrete containment hydro-blasting).

Verified Supporting Evidence:

I a. The hydro-blasting water jets appear to be responsible for some damage to the surrounding concrete close to the liner plate (FM 7.8 Exhibit 9). This occurred late in the hydro-blasting process when the thickness of concrete left in front of the liner plate was low; Verified Refuting Evidence:

a. The force and pressure applied by the hydro-blasting water jet were within the expected range for the intended operation, and within a controllable range to prevent/limit unintended concrete removal or damage to surrounding concrete or structures (FM 7.8 Exhibit 7);

b. The PII calculation (FM 7.8 Exhibit 7) agrees with a calculation done by American Hydro (FM 7.8 Exhibit 8). They also conclude that the force from the water jet to the containment is minimal;

c. There are no indication that Mac & Mac operated the equipment at a higher pressure than expected (FM 7.8 Exhibit 3 and FM 7.8 Exhibit 4);

d. The first time the hydro-blasting equipment was turned on, a mock-up operation was performed. This consisted of a small 8ft wide by 6ft high area to be hydro-blasted about 10 inches deep. There are strong indications that the crack was present very early while this mock-up was being performed (FM 7.8 Exhibit 11 is a summary of observation of cracks very early in the hydro-blasting process). This would indicate that the delamination may have been present before the hydro-blasting operation started; Discussion:

Interviews with engineers at Mac & Mac and at American Hydro demonstrated that the two systems are mostly similar. PII calculations and American Hydro calculation confirm that in both cases the force from the water jet tothe concrete is not sufficiently high to 2/18/10 P -rtry r Cui *-fi*I, Page 2 of 3 Draft 1

generate damage by itself. The principle of hydro-blasting confirms that hydro-blasting takes advantage of pre-existing cracks (FM 7.8 Exhibit 12 is chapter 5 "Waterjets in Civil Engineering Applications" from Professor David Summers book on water jets and their applications).

American Hydro has performed eight SGR openings into post-tensioned reactor building containments (seven were performed when we started this investigation in October 2009 and one more was done since at TMI). All were successful, demonstrating capability and process effectiveness for hydro-blasting SGR openings without unacceptable collateral damage to surrounding concrete or structures.

Additionally, all the literature we found on comparing the various means to perform concrete removal agree that hydro-blasting is the least damaging to the underlying structure. Pressures and forces generated during hydro-blasting are limited by the equipment and water requirements. When providing sufficient control for confining concrete removal to the desired area and depth, no damage is expected to occur in adjacent areas. Also, hydro-blasting does not result in mechanical impact per-se, but rather in rapid erosion/disintegration of the paste/aggregate sub-components (FM 7.8 Exhibit 12).

The analysis of cracked features in the concrete on the outside of containment, close to the liner plate, concluded that the water jet had enough force to push the liner (FM 7.8 Exhibit 11). This can be explained because the water at that stage in the hydro-blasting is impacting on a thin (3/8 in) long (25 ft x 27 ft) plate of steel, loosely bonded on the four sides (mostly through mechanical locking due to the plate stiffeners).

An important caveat to add is that although the forces generated by the water jet are not sufficient to initiate the delamination, it is possible they could have been instrumental in propagating it. Once the crack started in the plane of the tendon sleeves, it is "active" because it is in an area of local tensile stresses. Therefore it can be propagating with minimal forces serving as an "activation energy" force just pushing the local tensile stress above the tensile strength of the concrete.

==

Conclusion:==

Excessive water jet pressure was not a factor in creating the delamination.

It could have been a factor in the propagation of the delamination.

-2/18/10 rI-P-r -5..~....

TOO9 Page 3 of 3 Draft l-k- to th-d par1 wtho i

FM 7.8 Exhibit 1 page 1 of 16 TECHNICAL GUIDELINES Prepared by the International Concrete Repair Institute September 2004 Guide for the Preparation of Concrete Surfaces for Repair Using Hydrodemolition Methods Guideline No. 03737 Copyright © 2004 International Concrete Repair Institute All rights reserved.

International Concrete Repair Institute 3166 S. River Road, Suite 132, Des Plaines, IL 60018 Phone: 847-827-0830 Fax: 847-827-0832 Web: www.icri.org E-mail: info@icri.org 925

926 FM 7.8 Exhibit 1 CONCRETE REPAIR MANUAL page 2 of 16 About ICRI Guidelines The InternationalConcrete Repair Institute (ICRI) literature on concrete repairmethods and materials was founded to improve the durability of concrete as they have been developed and refined. Neverthe-repairandenhance its valuefor structureowners. The less, it has been difficult to find critically reviewed identification,development, andpromotionof thenmost information on the state of the art condensed into promising methods andmaterialsis aprimaryvehicle easy-to-useformats.

for accelerating advances in repair technology. To that end, ICRI guidelines are prepared by Working through a variety offorums, ICRI members sanctionedtask groups and approved by the ICRI have the opportunity to address these issues and Technical Activities Committee. Each guideline to directly contribute to improving the practice of is designed to address a specific area of practice concrete repair recognized as essential to the achievement of A principal component of this effort is to make durable repairs. All ICRI guideline documents carefully selected information on important repair are subject to continual review by the membership subjects readilyaccessible to decision makers. During and may be revised as approved by the Technical the past several decades, much has been reportedin Activities Committee.

Technical Activities Committee Producers of this Guideline Rick Edelson, Chair Subcommittee Members David Akers Pat Winkler, Chair Paul Carter Don Caple Bruce Collins Bruce Collins William "Bud" Earley Eric Edelson Garth Fallis Ken Lozen Tim Gillespie Bob Nittinger Fred Goodwin Steve Toms Scott Greenhaus Robert Johnson Kevin Michols Contributors Allen Roth Scott Greenhaus Joe Solomon Rick Toman Mike Woodward Synopsis Keywords This guideline is intended to provide an Bond, bonding surface, bruising, chipping introduction to hydrodemolition for concrete hammer, coating, concrete, delamination, removal and surface preparation, the benefits deterioration, full depth repair, hand lance, and limitations of using hydrodemolition, high-pressure water, hydrodemolition, impact and an understanding of other aspects to be removal, mechanical removal, micro-fracture, addressed when incorporating hydrodemolition post-tensioning, rebar, reinforced concrete, into a repair project. This guideline provides reinforcing steel, robot, rotomill, safety, sound a description of the equipment, applications, concrete, surface preparation, surface profile, safety procedures, and methods of water surface repair, tendon, vibration, wastewater, control and cleanup. and water jet.

This document is intended as a voluntary guideline for the owner, design professional, and concrete repair contractor. It is not intended to relieve the professional engineer or designer of any responsibility for the specification of concrete repair methods, materials, or practices. While we believe the information contained herein represents the proper means to achieve quality results, the International Concrete Repair Institute must disclaim any liability or responsibility to those who may choose to rely on all or any part of this guideline.

FM 7.8 EXI*AI*RI,1ATION OF CONCRETE SURFACES FOR REPAIR USING HYDRODEMOLITION MErI.I 3 of 16 927 Purpose Hydrodemolition has been used on the following types of structures:

" Bridge decks and substructures This guideline is intended to provide owners, design professionals, contractors, and other " Parking structures interested parties with a detailed description of

• Dams and spillways the hydrodemolition process; a list of the benefits " Water treatment facilities and limitations of using hydrodemolition for " Tunnels and aqueducts concrete removal and surface preparation; and an

• Nuclear power plants understanding of other aspects to be addressed " Piers and docks when incorporating hydrodemolition into a repair " Stadiums project. The guideline provides a description of " Warehouses the equipment, applications, safety procedures, " Retaining walls and methods of water control and cleanup. This guideline is not intended as an operating manual for hydrodemolition equipment as that information The Effects of is specific to each equipment manufacturer.

The scope of this guideline includes the use of hydrodemolition for the removal of Mechanical deteriorated and sound concrete in preparation for a concrete surface repair. In addition, the use Impact Techniques Mechanical methods such as chipping hammers, of hydrodemolition for the removal of coatings rotomills, scabblers, and scarifiers remove concrete is discussed. by impacting the surface. These procedures crush While the procedures outlined herein have (bruise) the surface, fracture and split the coarse been found to work on many projects, the aggregate, and create micro-fractures in the requirements for each project will vary due to substrate (Fig. 1 and 2). As a result, the ability of many different factors. Each project should be the fractured substrate to provide a durable evaluated individually to ascertain the applica-bility and cost-effectiveness of the procedures described herein. Other methods of surface preparation are discussed in ICRI Technical Guideline No. 03732, "Selecting and Specifying Concrete Surface Preparation for Sealers, Coatings, and Polymer Overlays."

Introduction Hydrodemolition is a concrete removal technique which utilizes high-pressure water to remove deteriorated and sound concrete. This process provides an excellent bonding surface for repair material. First developed in Europe in the 1970s, Fig. 1: Damage createdby chipping hammer this technology has become widely accepted for concrete removal and surface preparation throughout Europe and North America.

Hydrodemolition can be used for horizontal, vertical, and overhead concrete removals and surface preparation on reinforced and non-reinforced structures. It is effective in removing concrete from around embedded metal elements such as reinforcing steel, expansion joints, anchorages, conduits, shear connectors, and shear studs. Hydrodemolition can be used for localized removals where deterioration is confined to small areas and for large area removals in preparation M~owou for a bonded overlay. This technology can also be Im~

used to remove existing coatings from concrete. Fig.2: Damage createdby rotomilling

928 FM 7.8 Exhibit 1 CONCRETE REPAIR MANUAL page 4 of 16 bond with the repair material is compromised, requiring a second step of surface preparation to remove the damaged region.

Furthermore, impact methods may damage the reinforcing steel and embedded items such as conduit, shear studs and connectors, and expansion joint hardware. Impact methods transmit vibrations through the reinforcing steel, which may cause further cracking, delamination, and loss of bond between the reinforcing steel and the existing concrete. Vibration and noise created by the mechanical impact will travel through the structure, disturbing the occupants. During repair of thin Fig. 3.: Surface preparedby hydrodemolition has a slabs and precast tees, chipping hammers may rough irregularprofile with protrudingaggregateand shatter the substrate resulting in unanticipated full is excellent for creatinga mechanicalbond depth repairs.

For a discussion on surface bruising and the mechanical bond and composite action between mechanics of concrete removal by impact methods, the substrate and the repair material.

refer to ICRI Technical Guideline No. 03732, The rough, irregular surface profile provided "Selecting and Specifying Concrete Surface Preparation by hydrodemolition can result in bond strengths for Sealers, Coatings and Polymer Overlays." that equal or exceed the tensile strength of the existing concrete. The concrete surface profile Hydrodemolition can exceed CSP-9 (very rough) as defined in ICRI Technical Guideline No. 03732.

Benefits Rotomills and scarifiers remove concrete to a uniform depth and may leave deteriorated concrete below the specified depth. Altema-and Limitations tively, the waterjet moves in a consistent pattern The benefits of hydrodemolition can be placed into over the surface and will remove unsound two groups: structural benefits that improve the concrete even if it is below the specified depth.

quality of the repair, and environmental benefits Since the water jet does not create mechanical that improve the quality of the work place. impact, vibration is not transmitted into the structure Hydrodemolition also has limitations, which need from the hydrodemolition operation. Delami-to be considered. nation beyond the repair area caused by vibration of the reinforcing steel is greatly reduced.

Structural Benefits During hydrodemolition, sand and cement

" A rough, irregular surface profile is created particles mix with the waterjet. The abrasive action to provide an excellent mechanical bond for of theses particles is usually sufficient to clean repair materials; uncoated reinforcing bar and embedded metal

" Surface micro-fracturing (bruising) is eliminated; items without damaging them. Corrosion material

" Exposed aggregates are not fractured or split; is removed from the reinforcing bar and metal

" Lower strength and deteriorated concrete is items, allowing for easy inspection and identifi-selectively removed; cation of cross-sectional area loss. The reinforcing

" Vibration is minimal; bar is cleaned without any loss of deformations.

" Reinforcement is cleaned, eliminating the need Cleaning of the entire reinforcing bar, however, for a second step of surface preparation; and will not occur if the reinforcing bar has not been

• Reinforcing and other embedded metal elements completely exposed during hydrodemolition.

are undamaged.

During concrete removal, the waterjet is directed Environmental Benefits at the surface, causing high-speed erosion of the " Minimizes disruptions to users of occupied cement, sand, and aggregate. The water jet does space by significantly reducing transmitted not cut normal weight aggregate which remains sound through the structure; intact and embedded as part of the rough, irregular " Increased speed of concrete removal can surface profile (Fig. 3). The aggregate interlocks reduce construction time; with the repair material to assist in developing a " Minimizes dust; and

FM 7.8 ExRIOA1WATION OF CONCRETE SURFACES FOR REPAIR USING HYDRODEMOLITION MEPj-W 5 of 16 929

• Robotic units reduce labor and minimize " The waterjet will remove the sheathing from injuries as compared to chipping hammers. post-tensioning tendons and may drive water Concrete removal by hydrodemolition can take into the tendon; place inside an occupied structure, such as a hotel, " The hydrodemolition robot may be too large to apartment building, office building or hospital access small or confined areas of the structure; with minimal noise disruption to the occupants. " The water jet can damage coatings on reinforcing Hydrodemolition can quickly remove concrete. steel and other embedded items; As such, project duration can be reduced, mini- " The waterjet can introduce water into electrical mizing the impact on the users of the structure. system components, especially if embedded During demolition, cleanup, and final wash in the concrete and already deteriorated or not down, the concrete debris and repair surface remain properly sealed; and wet, minimizing dust in the work area. Since hydro- " If cleanup is not properly performed in a demolition cleans the reinforcing steel, the need timely manner, further surface preparation to sandblast is eliminated unless additional concrete may be required.

removal is required using chipping hammers. As such, silica dust in the work area is reduced, thereby providing a safer work environment. The Hydrodemolition The use of chipping hammers and other impact methods are labor intensive and physically demanding, which can cause injury to the employee.

System The hydrodemolition system consists of a Robotic hydrodemolition equipment reduces the support trailer or vehicle, high-pressure use of these tools and the possibility of injury. pump(s), a robotic unit to perform the demolition, and high-pressure hoses to connect the pump (s)

Limitations to the robot. Hand lances are also available

" The hydrodemolition process consumes a to remove concrete in areas inaccessible to significant amount of water (6 to 100 gpm the robot.

125 to 380 lpm]). A potable water source must be available. The cost of the water should Support Trailer be considered; Hydrodemolition units are typically transported

" Wastewater containing sand and cement fines on 40 to 50 ft trailers (Fig. 4). The robot may (slurry) must be collected, treated, and returned to the environment. Wastewater disposal may require a permit;

" Projects requiring total demolition can be done faster and more economically with crushers and similar equipment; prp-

• Water can leak through cracks in the concrete and damage occupied space below the repair area. Hydrodemolition should not be used over Wwtr Fflkr Task, occupied areas due to the risk of blow-through Fucl Tanks (unanticipated full-depth removal); 0 VAWk Ares SPMVparts

" Repair areas of varying strength will result in non-uniform removal. Areas of high strength may need to be removed using hand lances or Fig. 4: Hydrodemolitionsupport trailerA self-chipping hammers; containedunit transportspumps, robot,hoses,

" The water jet is blocked by reinforcing steel and spareparts resulting in concrete shadows under the reinforcing bar that may need to be removed be transported on the same trailer or separately using hand lances or chipping hammers; on a smaller trailer. The support trailer usually

" Since the waterjet of a robotic unit is contained contains a supply of spare parts, tools, maintenance in a metal shroud, some robots are unable to area, fuel and water storage, supply water completely remove concrete up to a vertical hoses, and filters. These units are designed surface such as a curb, wall or column. The to be self-sufficient on the job site with adequate remaining concrete may have to be removed spare parts to perform routine maintenance using hand lances or chipping hammers; and repairs.

930 FM 7.8 Exhibit 1 CONCRETE REPAIR MANUAL page 6 of 16 High Pressure Pumps The high-pressure pumps used for hydrodemolition are capable of generating pressures from 10,000 psi to 40,000 psi (70 to 275 MPa) with flow rates from 6 to 100 gpm (25 to 380 1pm).

The pumps are driven by a diesel or electric motor, typically operating between 100 and 700 horsepower. The engine size will vary based on the flow and pressure rating of the pump. The pumps operate most efficiently at their design pressure and flow. High-pressure hoses connect the pumps to the robot. The pumps may be located a significant distance (500 ft [150 in])

Fig.6: Nozzle is mounted on a traversebeam from the actual removal area. However, due to a drop in pressure and flow through the high-pressure hoses, the pumps should be located as close as possible to the removal area, typically within 300 ft (100 m).

Robotic Removal Unit- Rotationgo Oscillation Horizontal Surfaces The force created by the high-pressure pump(s) is controlled using a robotic removal unit (Fig. 5).

The robot is a diesel or electric powered, self-propelled, wheeled or tracked vehicle. It is used to uniformly move and advance the waterjet over Fig. 7: Rotating or oscillatingnozzles the surface during concrete removal.

8., Rotating nozzles are angled from center Fig. 5: Typical hydrodemolition robot The water jet is mounted on a trolley that traverses over the removal area along a cross feed A09W Noz*

or traverse beam (Fig. 6) perpendicular to the aSJ

. I'M00 rp a - 30" advance of the robot. The water-jet nozzle may Wmah htWoW1 either oscillate or rotate (Fig. 7). The oscillating nozzle is angled forward in the direction of the traverse. Rotating nozzles are angled from the center, creating a cone effect while rotating (Fig. 8 and 9).

The nozzle assembly is enclosed within a steel shroud with rubber seals around the perimeter to contain the debris during demolition (Fig. 10). Fig.9: Rotation of the anglednozzle creates a water cone

FM 7.8 EXAfKMItiIA1TION OF CONCRETE SURFACES FOR REPAIR USING HYDRODEMOLITION METPW* 7 of 16 931 3 seconds and the waterjet may traverse only one time before the robot advances 2 to 4 in. (50 to 100 mm).

The depth of concrete removal is controlled at the robot. Since the pumps are designed to operate at a specific pressure and flow rate, it is unusual to reduce the pressure (and subsequently the flow rate) to adjust the depth of removal.

Narrow areas may be removed by adjusting sensors that limit the movement of the water jet along the traverse beam. The traverse and advance functions limit the removal to a rectangular area along the advance path of the robot. Because the Fig. 10: Nozzle is enclosed within a steel shroud water jet is contained within a steel shroud, most robots are unable to remove concrete within 3 to The rotation/oscillation of the nozzle combined 6 in. (75 to 150 mm) of vertical surfaces.

with the traverse and advance of the robot provide a uniform and continuous motion of the waterjet over the removal area (Fig. 11). Each of Specialized Robotic Equipment-these functions is fully adjustable. The depth of Vertical and Overhead Surfaces concrete removal is determined by the length of Various types of robotic equipment are available time the waterjet is directed at the removal area. to perform removals on walls, soffits, substructures, beams, columns, and tunnels. These robots are often built on wheeled or tracked vehicles and have the ability to lift the traverse beam into the vertical or overhead position. The primary functions of traverse and advance are utilized in order to provide uniform concrete removal during vertical and overhead repairs.

As an alternative to the robot, the waterjet may also be attached to a frame that allows the jet to move in a two dimensional "X-Y" plane. The X-Y movement of traverse and advance are present in these units to provide uniform concrete removal.

The X-Y frames can be lifted and positioned over Fig. 11: The waterjet traversesback andforth perpen- the removal area using a crane, backhoe, all-dicularto the forward advance of the robot terrain forklift or other similar equipment.

Adjusting the following parameters will increase Hand Lance or decrease the depth of removal: Hand lances operate at pressures of 10,000 to

a. Total traverse time (time of each traverse x 40,000 psi (70 to 275 MPa) while delivering number of traverses); and approximately 2 to 12 gpm (8 to 45 lpm) of water.

b. Distance of the advance. Hand lances are not as fast or as precise for Once these parameters are set, the robot will concrete removal as a programmed robot and are reproduce the settings in a programmed sequence slower than chipping hammers. Hand lances are to provide consistent removal of the concrete. For effective in performing light scarification and example, during deep removal to expose the coating removals. It should be noted that the reinforcing bar 3 to 4 in. (75 to 100 mm), the water jets on hand lances may not be shrouded, traverse speed may be 8 seconds (the time increasing the risk of debris becoming airborne.

required for the waterjet to move from one side of Hand lances can be used for removal of:

the traverse beam to the other) and the waterjet " Concrete shadows below reinforcing bar; may traverse 3 times before the robot advances " Concrete adjacent to walls, columns, curbs, forward i to 2 in. (25 to 50 mm). On the other hand, and in tight and confined areas not accessible for light scarification 1/4 to 1/2 in. (6 to 13 mm) to the robotic equipment; and or coating removal, the traverse speed may be " Coatings.

932 FM 7.8 Exhibit 1 CONCRETE REPAIR MANUAL page 8 of 16 Safety Hydrodemolition involves the use of potentially dangerous specialized equipment. At all times, the manufacturer's instructions for the safe operation of the equipment and personal protective equipment should be followed, as well as all local, state, and federal regulations. Hydrodemolition units should be supervised and operated by qualified personnel certified by the equipment manufacturer.

Hydrodemolition employs high-velocity water jets to demolish concrete and perform surface preparation. Even though the waterjet is shrouded Fig. 12: Scarifiedsurface with 1 in. aggregate on robotic units, debris can be propelled from beneath the shroud with sufficient velocity to cause serious injury. Serious injury or death can also occur if struck by the water jet. Hand lances are typically not shrouded and care must be exercised to avoid injury when using these tools.

Workers, equipment operators, and any indi-viduals entering the work area are required to wear hard hats, safety glasses, hearing protection, safety shoes, gloves, long pants and long-sleeve shirts, and must be trained in the proper use of personal protective equipment. When using a hand lance, the operator should wear a full-face shield, rain suit, and metatarsal and shin guards.

Additional protective clothing may also be required Fig. 13: Scarifiedsurface with 3/4 in. aggregate for use with hand lances. Everyone involved with the hydrodemolition operation should receive a concrete overlay. If the surface was previously specific training outlining the dangers associated rotomilled, the minimum removal depth using with the use of high-pressure water. hydrodemolition should equal the size of the Prior to starting demolition, an inspection of coarse aggregate to remove all concrete micro the area should be performed including the area fractures and damaged or crushed aggregate.

under the work area. All barricades, partitions, Scarification may not remove all unsound shielding, and shoring must be installed and concrete due to the rapid rate at which the waterjet warning signs posted to prevent unauthorized moves over the surface. It may be necessary to entry into the work area. The area below the work resurvey the scarified surface and identify delami-area must be closed off and clearly marked nated or deteriorated areas for further removal.

"Danger- Do Not Enter." Electrical conduits or other electrical equipment in the work area should Partial Depth Removal be deenergized to avoid electrical shock. Partial depth removal is commonly required if Special precautions are required for post- chloride contamination has reached the top mat tensioned structures as referred to in the section of reinforcing steel or deterioration, delamination "Considerations for Hydrodemolition Use." or spalling occurs within the top mat of reinforcing steel. Partial depth concrete removal can expose Hydrodemolition the top mat of reinforcing steel and provide clearance, typically a minimum of 3/4 in. (19 mm),

Applications below the bottom reinforcing bar of the top mat (Fig. 14 and 15). Determining the reinforcing bar size and concrete cover are critical to determine Scarification the required removal depth.

Scarification is performed to remove the surface Concrete removal using hand lances or chipping concrete and provide a rough profile (Fig. 12 and hammers may be required to remove shadows 13). Scarification is often used in preparation for under the reinforcing bar, previously repaired areas

FM 7.8 ExIROiMIA1LATION OF CONCRETE SURFACES FOR REPAIR USING HYDRODEMOLITION ME#W 9 of 16 933 used. Other structural elements such as shear connectors, shear studs, and steel beam flanges can be exposed without damage.

During full depth removal, the removal rate slows as the depth increases because the water jet stream dissipates as it moves away from the nozzle and the water jet must push more water and debris from its path prior to contacting the surface to be removed.

Full depth removal is often necessary on waffle or pan joist slab systems (Fig. 16).

Pig.14., Partialdepth removal Fig. 16: Full depth removal-waffle slab Fig. 15: Partialdepth removal on a retainingwall Coating Removal or high areas resulting from variations in the Hydrodemolition can be used for the removal strength of the concrete. In addition, concrete of epoxy, urethane, hot applied membrane, and removal may be necessary adjacent to vertical other coatings from concrete surfaces (Fig. 17).

surfaces such as curbs, walls and columns. Saw When performing coating removal, a multiple cutting of the perimeter of the repair area, if jet nozzle is used. The multiple jets allow the required, should be performed after hydro- water to penetrate the coating without damaging demolition to prevent damage to the saw cut. This the concrete. However, if the concrete below the will require additional concrete removal along coating is deteriorated, it may be removed along the repair perimeter with hand lances or chipping with the coating.

hammers. If the saw cut is made first, the area outside the saw cut should be protected using a steel plate. The steel plate will allow the waterjet to slightly over run the saw cut without damaging the surface outside the saw cut while completely removing the concrete within the repair area.

Full Depth Removal Hydrodemolition can be used for full depth removal where delamination has occurred in the lower mat of reinforcing or chloride contami-nation exists throughout the entire thickness of the slab. Full depth removal can be performed along expansion joints and other areas where there is a high concentration of reinforcing steel that may Fig. 17: Coating removal using a spinning, multi-nozzle be damaged if conventional removal methods are spray head

934 FM 7.8 Exhibit 1 CONCRETE REPAIR MANUAL page 10 of 16 The Hydrodemolition If the strength of the concrete increases or a high-strength repair area is encountered during hydrodemolition, the removal depth will Process decrease (Fig. 19). The decrease in depth may not be immediately detected by the operator, resulting Concrete removal by hydrodemolition is impacted by the following factors: in an area of shallow removal (Fig. 20). To obtain

" Size and density of the aggregate; the required depth in higher strength concrete,

" Concrete strength; the total traverse time is increased and the

" Uniformity of concrete strength; advance of the robot is decreased. If the high-

" Extent of cracking; strength repair area is large enough, it may be

" Deterioration and delamination; possible to set up the hydrodemolition robot over

" Surface hardeners; the area and remove to the specified depth. This

" Previous repairs with dissimilar strength material; and

" Size and spacing of reinforcing steel or other embedded items. D~wConf -

In sound concrete, the variation in the depth 6,0001~30900 P" I Hnod DwkCvcr of removal will generally equal the size of the 3.$Wto A s _

coarse aggregate (Fig. 18). For example, if the coarse aggregate is 1 in. (25 mm), D = 1 in. 9 (25 mm) and the specified depth of removal is 2 in. (50 mm), the range of removal will be 2 in.

(50mm) +/- D1/2 (1/2 in. or 13 mm), or 1-1/2 in.

(38 mm) to 2-1/2 in. (63 mm).

^e* R.M rwp  : ....

Fig. 18: The depth of removal depends on the size of the course aggregate During hydrodemolition, a high-pressure water jet is uniformly moved over the surface and, provided the concrete is sound and the strength does not change significantly, the removal depth will remain consistent. Depth variations occur when the concrete strength changes, cracking or delamination is present, the concrete is deteriorated or the surface has been previously repaired using a different type and strength of material. In comparison, rotomilling or dry-milling equipment can be set to a specific depth and the milling drum will mill the surface Fig. 19.: High-strength concrete is removed at a slower to that depth regardless of any variations in the rate than normal concrete, which can result in a non-concrete strength, quality or level of deterioration. uniform removal

FM 7.8 ExARMJlAfRATION OF CONCRETE SURFACES FOR REPAIR USING HYDRODEMOLITION MOJBY1 1 of 16 935 Fig.20: High-strengthrepairarea within the hydro-demolition area procedure can be problematic for two reasons.

First, if the water jet overruns the high-strength repair area, it may result in a blow-through or full depth removal at the perimeter of the high-strength repair area. Second, since the water jet must be slowed significantly, it may cause excessive removal below the high-strength area once it is removed and the softer base concrete is exposed.

For these reasons, it is often preferable to use chipping hammers in high-strength repair areas.

The opposite effect is encountered if the concrete strength decreases or there is cracking, deterioration or delaminations (Fig. 21). Concrete that is deteriorated, low strength or delaminated is removed faster than the surrounding sound concrete by the water jet. For example, if the average removal depth is 2 in. (50 mm) and there is a delamination that is 2 in. (50 mm) deep, the actual removal within the delaminated area could be 3 to 4 in. (75 to 100 mm) deep. For this reason, removal in an area that is seriously deteriorated and delaminated may not be consistent.

This effect is often described as "selective removal of deteriorated concrete." While the water Fig.21: Delaminatedor deterioratedconcrete is jet is traversing and advancing uniformly over removed at a faster rateleading to non-uniform removal the surface, it is removing unsound, delaminated, deteriorated, cracked, and low strength concrete is most difficult at reinforcing bar intersections.

selectively below the specified removal depth. Increasing the specified depth of removal will Selective removal is not without limitations. minimize the amount of shadowing.

For example, if the robot is traversing and advancing Pointing the water jet under the reinforcing rapidly as during scarification, it may not remove bar can reduce concrete shadows. This can be deeper delaminations. accomplished by using a rotating or oscillating Size and spacing of the reinforcing steel will nozzle (refer to Fig. 7-9). Rotating nozzles are also influence the removal depth. The reinforcing typically angled 100 and 300 from center. The steel blocks the waterjet and shields the concrete nozzle rotates between 100 and 1800 rpm, creating below, creating concrete "shadows" (Fig. 22 and a demolition cone that will undercut both the 23). Removal of concrete shadows becomes more transverse and parallel reinforcing bar provided difficult as the reinforcing bar size increases and the specified removal depth is greater than the

936 FM 7.8 Exhibit 1 CONCRETE REPAIR MANUAL page 12 of 16 Fig. 23.: "Shadow" under the rebar (note tie wire undamagedand in excellent condition) removal may result in the removal of sound concrete, it will minimize the need for concrete removal under the reinforcing bar with chipping hammers or hand lances.

Considerations for Hydrodemolition Use Issues that should be considered when evalu-ating the use of hydrodemolition for a repair project include:

Limited quantity of repair:Mobilization and set up of the hydrodemolition equipment can be expensive. If there are only minor repairs or a limited quantity of repairs, the mobilization cost may make the process uneconomical.

Increase in repairquantity: The traverse and advance function of the hydrodemolition robot results in removal areas that are rectangular. The removal areas may have to be "squared up" in order for the hydrodemolition equipment to efficiently remove the concrete. "Squaring up" the repair areas may lead to an increase in the Fig.22: Reinforcing steel blocks the waterjet leaving a removal quantity and the cost of the project.

concrete "shadow" under the reinforcing.Increasingthe Reinforcing barsize and concrete cover:

removal depth will decrease the amount of shadowing Partial-depth removal normally requires clearance below the bottom reinforcing bar of the top mat depth of the reinforcing bar. Similarly, the oscil- of reinforcing. The size and quantity of the lating nozzle moves from side to side as it traverses, reinforcing bar and the concrete cover over the directing the water jet at an angle to the surface, reinforcing bar should be determined in order to cutting under the reinforcing bar. The nozzle is specify the correct removal depth to achieve the angled forward as it traverses left, and at the end required clearance.

of the traverse, flips to face forward as it traverses Potentialfor full-depth blow-throughs:Hydro-right. To minimize concrete shadows, the required demolition of severely deteriorated structures depth of removal should be at least 3/4 in. (19 mm) may result in full-depth blow-throughs. Blow-below a #5 reinforcing bar. Larger reinforcing throughs may take place where full depth slab bars will require a greater removal depth to cracks occur, especially if deterioration is evident minimize shadowing. While this additional on the slab underside. Shielding may be required

FM 7.8 ExIRUARATION OF CONCRETE SURFACES FOR REPAIR USING HYDRODEMOLITION MOJR )I 3 of 16 937 to protect the area below from damage. Shoring of the structure. Temporary shoring may be below the blow-through may be damaged or needed to move the pumps into the structure.

destroyed. When the water jet is in the open air, Available water sources: Pumps used for as will happen when the waterjet blows through hydrodemolition require a steady supply of clean the deck, it is extremely noisy (may exceed water at a sufficient volume to perform the work.

130 db) and dangerous. Sound resistant partitions Generally, local municipal water is used for should be installed to contain the noise within the hydrodem0lition. Sources close to the work area, structure if blow-throughs are expected. such as a nearby fire hydrant or water line feeding Extent of previous repairs: Repair materials the structure, should be adequate. Specific water may have a different compressive strength than requirements will vary, depending on the hydro-the original concrete. Since the hydrodemolition demolition unit used for the project and the jet is set to move at a uniform rate, the presence method of cleanup. Cleanup performed using a of dissimilar strengths of material will result in a fire hose operating at 100 to 200 gpm (380 lpm variation in the depth of removal. Higher strength to 760 1pm) will use substantially more water areas may require further concrete removals using than an 8000 to 10,000-psi (55 to 70 MPa) water chipping hammers or hand lances to achieve the blaster operating at 8 to 12 gpm (30 to 45 lpm).

specified depth of removal. Lower strength areas In remote areas, water can be drawn from wells, may result in deeper removals and possibly full- fresh water lakes, rivers, or streams. This water depth blow-throughs. must be pre-filtered to remove any suspended Occupiedareasadjacentto or underthe repair solids to avoid damage to the high-pressure area: Occupied spaces such as stores or offices pumps. Recycled water has been used for hydro-may occur in the structure. It may not be practical demolition, however, it can add substantially to perform hydrodemolition adjacent to or over to the cost of the project due to collection and these areas. Water from the hydrodemolition may filtration of the water and the added wear to leak to the occupied level below. As such, the the equipment caused by dissolved minerals in repair area should be protected to prevent water the recycled water. When available, potable from entering the occupied area. water is used. Water may have to be trucked into Shoring requirements: During structural remote locations.

repairs, concrete may be removed from around Post-tensionedstructures: The use of hydro-the top reinforcing. An analysis of the structural demolition on post-tensioned structures has capacity of the remaining slab section should be potentially severe risks and must be carefully made by a qualified engineer to determine if evaluated to maintain a safe working environment, shoring will be required. The weight of the maintain structural integrity, and to preserve the hydrodemolition robot should be considered long-term durability of the structure. Sudden when determining shoring requirements. release of anchorages can result in dangerous Equipment location. The hydrodemolition explosive energy and flying debris capable of equipment is transported on a trailer. If possible, causing damage to equipment and serious injury the pumps should be located within 300 ft of or death to workers. Tendons should be de-tensioned the repair area. A suitable location next to the prior to removing concrete from around anchorages structure must be selected. Pump units that are to prevent the sudden release of the anchorages powered by diesels engines should not be located and loss of pre-stress forces. The loss of pre-stress next to the air intake of adjacent buildings. In forces may result in the loss of structural integrity congested metropolitan areas, the pumps may be and result in the need for shoring. Careful eval-removed from the trailer and placed within the uation must also be exercised when removing structure. Diesel powered pumps will need to be concrete around post-tensioning tendons. Removal located close to an exhaust shaft and the exhaust of concrete around tendons can result in a change from the pumps piped to this location. A fuel tank of tendon profile, which may also result in the will also have to be placed in the pump area and loss of prestressing force and structural integrity.

provisions made to fill the tank as required. The wires or strands of post-tensioning tendons Although electric pumps may be used inside the are usually undamaged during hydrodemolition, structure eliminating the fueling and exhaust however the sheathing and protective grease will concerns, they have a substantial power requirement be removed from unbonded tendons. In bonded and will need an electrical service installed. Due post-tensioning tendons, the waterjet may penetrate to the weight of the pumps, they may need to be the duct and remove the grout inside. In either placed on the slab on ground or in a shored area case, the hydrodemolition water may enter the

938 FM 7.8 Exhibit 1 CONCRETE REPAIR MANUAL page 14 of 16 tendon at the edge of the repair area and can be and stored and temporary lighting installed.

driven into the tendon outside the work area. Sprinkler heads may need to be protected. Mist and Water remaining in the tendon can cause future high humidity in the work area could damage corrosion affecting the long-term durability of the electrical panels and other services. Items remaining post-tensioning system. Each tendon must be in the work area should be protected.

carefully examined and any water that has entered Temperature: When the temperature falls the tendon removed. Both the grease and the below freezing, the structure must be heated or protective sheathing must be restored. the hydrodemolition stopped to prevent water It may not be possible to remove moisture that from freezing in the work area.

has entered the post-tensioning system during the hydrodemolition process. In addition, verification of the presence of moisture is difficult and Test Area may not be possible. Refer to ICRI Technical A test area should be designated to establish the Guideline No. 03736, "Guide for the Evaluation operating parameters and to demonstrate that the of Unbonded Post-Tensioned Concrete Structures," equipment, personnel, and methods of operation for suggested procedures to detect water in post- are capable of producing satisfactory concrete tensioning tendons. Long term monitoring for removal results. The test should include sound future corrosion may also be prudent. and deteriorated concrete areas, each a minimum Conduitand embeddedmetal items: Embedded of 50 ft2 (5 m2 ). First the robot is set to remove aluminum and steel conduit will not be damaged sound concrete to the specified depth. Once the by hydrodemolition if they are in good condition. operating parameters have been determined, However, deteriorated portions of aluminum and the equipment is moved to the deteriorated area steel conduit will be damaged and water will and a second test is performed using the same enter the conduit system. PVC conduit will be operating parameters. If satisfactory results are damaged during hydrodemolition. As a safety achieved, the quality and depth of removal precaution, all conduits should be deenergized will become the standard for the project. If hand during demolition. Other metal items within lances are to be used to perform concrete the removal area such as shear connectors, shear removals, they should also be demonstrated to studs, and anchorages will not be damaged show satisfactory results.

by hydrodemolition. It is noted that the hydrodemolition robot will Noise limitations: Hydrodemolition does not move the water jet over the surface in a constant produce sound that is transmitted through a motion and if the concrete is of uniform strength, structure, however, the noise from the hydro- the removal depth will be consistent. However, demolition unit in the work area is sufficiently since concrete is seldom uniform, there will be loud to be objectionable to the public. Further- variations in the removal depth on the project.

more, noise can be excessive during full-depth Other factors affecting the removal depth include repairs or blow-throughs. Sound reducing partition the extent and depth of deterioration, the size and walls that separate the public from the work area quantity of reinforcing bar, the concrete cover may be required. Acoustical studies indicate that over the reinforcing bar, and the presence of the sound waves created by hydrodemolition are surface hardeners. As the equipment is used, low frequency and are best controlled using dense nozzles will wear, changing the force created material such as sheet rock or concrete board. by the water jet. As such, the hydrodemolition There are a variety of sound deadening materials equipment operator must monitor the depth and supplied by various vendors that have proven quality of removal and adjust the parameters of effective in controlling noise. Partition walls the robot to provide consistent removal through-should be protected from moisture. If properly out the project.

sealed at the base, a water resistant sound reducing partition wall will also assist in containing the water within the work area. Wastewater Control Protection of lighting, sprinklers, and other Controlling the wastewater has often been viewed services: Light fixtures, fire protection systems, as one of the more difficult tasks associated with and other services may be damaged by airborne the use of hydrodemolition. However, with pre-debris from the hydrodemolition or clean up planning and proper installation of a wastewater operation. If full depth removal or blow-throughs control system, the water can be properly managed are anticipated, light fixtures may need to be removed (Fig. 24). Hydrodemolition wastewater should be

FM 7.8 EXIfAiIATION OF CONCRETE SURFACES FOR REPAIR USING HYDRODEMOLITION MP'JI 5 of 16 939 Water containment and collection systems will vary depending on the structure. Where possible, it is best to take advantage of gravity to move the water to the treatment area. In many structures, the slab on ground can be used to collect and treat the water. The water may be allowed to flow through the structure to the lowest level or through the existing drains, which have been disconnected just below the underside of the first supported level. All slab-on-ground drains should be plugged and water should not be allowed to enter the drainage system prior to treatment. Once the water is clear and the pH adjusted, it can be Fig. 24: Typical wastewaterhandlingsystem pumped directly to the discharge point. Additional treatment capacity may be necessary if rainwater discharged to the storm or sanitary sewer or to cannot be separated from the wastewater.

the ground for absorption and/or evaporation Floor slabs and decks are commonly crowned under permit from the controlling authority. or sloped to provide drainage. Since water will Discharge into an existing storm or sanitary line run to the low area, a simple method of water may occur in the structure or to a nearby storm control involves the use of hay bales or aggregate or sanitary line accessed through a manhole. A dams, which can be set up along curb lines or the 4-in. (100 mm) connection should be adequate. perimeter of the work area. As the water ponds Wastewater may not be discharged directly to a in front of the hay bales or aggregate dams, the wetland, stream, river or lake. suspended solids will settle out. In areas where Hydrodemolition wastewater contains suspended the drains are plugged, the water is forced to pass particles and typically has a pH of 11 to 12.5. The through the hay bales or aggregate dams. Retention wastewater is initially placed in settling tanks ponds can be built at the end of the structure and or ponds to reduce the suspended solids. The the water directed or pumped to these ponds.

particles are heavy and settle out quickly as Settling tanks can also be used and the water the water is allowed to stand. This can also be pumped from the structure to the tanks.

accomplished by allowing the water to pass through a series of berms that are lined with filter fabric or hay bales. Debris Cleanup The controlling authorities for discharge have varying requirements for the level of suspended and Disposal solids and the range of pH for discharge into their Hydrodemolition debris consists of wet sand, system. Typically the water should be clear and aggregate, chips or chunks of concrete, and slurry the pH range between 5 and 10. Ponding the water. Slurry contains cement particles and ranges water will clarify it, however, the pH of the from muddy water to a thick paste. Removal of the wastewater may have to be reduced prior to debris should occur as soon as possible to prevent discharge. This can be accomplished by the the debris from solidifying and adhering to the introduction of acid, CO 2 or other pH reducing surface, making cleanup more difficult.

materials into the wastewater. Adding flocculants Tools used for cleanup include: fire hoses, can assist in reducing suspended solids. A location pressure washers, compressed air, sweepers, skid for settling ponds or tanks and pH reducing steer loaders, vacuum trucks, and manual labor.

equipment should be determined. The types of cleanup will vary based on the The cost to discharge wastewater ranges from type of removal performed as follows:

the cost of a discharge permit to charges for the 1. Above the reinforcingbar-any removal depth actual water consumed and discharged. The cost above the top reinforcing bar of the top mat of of water consumed is generally that of commercial reinforcing and the reinforcing bar remains water usage within the community. The controlling supported by the concrete; authority may require monitoring and testing of 2. Below the reinforcingbar-any removal depth the wastewater. Local ordinance requirements must below the top mat of reinforcing bar in be reviewed and met prior to discharge, including which the top reinforcing bar mat becomes the obtaining of proper permits. unsupported by the original concrete; and

940 FM 7.8 Exhibit 1 CONCRETE REPAIR MANUAL page 16 of 16

3. Full-depthremoval.

During above the reinforcing bar clean up, equipment such as skid steer loaders, sweepers, and vacuum trucks may be driven over the surface to assist with the cleanup (providing they meet the weight requirements of the structure). The debris can be swept, pressure washed or air blown into piles where it is picked up by a loader. A vacuum truck may be used to vacuum the debris from the surface. In all cases, the surface must be pressure washed to remove any remaining cement slurry.

If the removal is below the reinforcingbarand the reinforcing bar is unsupported, it is difficult Fig: 25: Measuringdepth ofremoval using a and possibly unsafe to drive equipment into the straightedge removal area. The debris can be removed by washing with a fire hose (large water consumption), The most common practice of measuring the pressure washing or blowing it onto the adjacent depth of removal is to place a straightedge on top original surface where it can be picked up with a of the original surface and extend it over the loader. A pressure washer operating at 8000 to removal area. Measurements are taken from the 10,000 psi (55 to 70 MPa) and 8 to 12 gpm bottom of the straightedge to determine the depth (30 to 45 lpm) is effective. Vacuuming has proven of removal. This quick and simple technique can very effective in removing debris from around only be used during the removal process and is the reinforcing steel, however, the surface will not applicable for final measurements in large require pressure washing to remove the cement removal areas.

slurry and paste. A string line may be pulled over the removal During full-depth removal, the debris simply area and measurements taken below the string.

falls to the floor below where it can be picked up However, this method could provide incorrect with a loader. results if slopes or crowns occur in the original The debris, which consists of wet sand, surface. Surveying equipment may be used and aggregate, chips or chunks of concrete, and is very accurate; however, to account for slopes, slurry is placed in dumpsters or hauled away in pitches and crowns in the original surface, a detailed trucks and may be recycled or placed in a landfill survey must be made of the original surface in accordance with the requirements of the prior to removal and measurements taken at the controlling authority. same locations after removal for comparison and determination of the actual removal depth.

Removal Depth Measurements Summary Effective concrete removal and proper surface Following hydrodemolition, the surface profile preparation are key elements to a successful repair is very rough and three depth measurements are project. A surface prepared using hydrodemolition possible (Fig. 25): is rough, irregular, and is excellent in creating a

1. Minimum removal-original surface to the mechanical bond with the repair material.

shallowest removal point. Hydrodemolition eliminates micro-fractures and

2. Maximum removal-original surface to the damage to reinforcing steel, minimizes transmitted deepest removal point. noise and dust, and cleans the reinforcing steel.

3. Average depth of removal-The difference The use of hydrodemolition may not be appro-between the minimum and maximum removal priate for every structure and a careful review of at the same location. the benefits and limitations of the process relative Measuring the depth of removal can be to each structure should be undertaken. Proper accomplished using: safety procedures must be observed at all times

1. A straight-edge placed on the original surface; when using hydrodemolition.

2. A string-line pulled over the removal area; and

3. A surveyor's level.

FM 7.8 Exhibit 2 ,-.....page1p9. A...:

.ACI 546R-04:

Concrete Repair Guide Reported by ACI Committee 546 Jay H. Paul Paul E. Gaudette Chair Secretary James P. Barlow Yclena S. Golod Kevin A. Michols Joe Solomon Paul D. Carter Harald G. Greve Richard Montani Michael M. Sprinkel Michael M. Chehab Robert F. Joyce Myles A. Murray Ronald R. Stankic Marwan A. Daye Lawrence F. Kahn Thomas J. Pasko George I. Taylor Floyd E. Dimmick Brian F. Keane Don T. Pyle Alexander Vaysburd Peter H. Emmons Benjamin Lavon Richard C. Reed D. Gerald Walters Michael J. Garlich Kenneth M. Lozen Johan L. Silfwcrbrand Patrick M. Watson Steven H. Gebler James E. McDonald W. Glenn Smoak Mark V. Ziegler I. Leon Glassgold This document provides guidance on the selection and application of CONTENTS materials andmethods for the repairprotection, andstrengtheningof concrete Chapter 1-Introduction, p. 546R-2 structures. An overview of materials and methods is presented as a guidefor 1.1-Use of this document making a selectionfor a particularapplication. References are providedfor 1.2-Definitions obtainingin-depth informationon the selected materialsor methods.

1.3-Repair methodology Keywords: anchorage; cementitious; coating; concrete; joint sealant; 1.4-Design considerations placement; polymer; reinforcement; repair. 1.5-Format and organization Chapter 2-Concrete removal, preparation, and repair techniques, p. 546R-6

2. 1-Introduction and general considerations ACI Committee Reports, Guides, Standard Practices, and 2.2-Concrete removal Commentaries are intended for guidance in planning, designing, executing, and inspecting construction. This 2.3-Surface preparation document is intended for the use of individuals who are 2.4-Reinforcement repair competent to evaluate the significance and limitations of its content and recommendations and who will accept 2.5-Anchorage methods and materials responsibility for the application of the material it contains. 2.6-Materials placement for various repair techniques The American Concrete Institute disclaims any and all 2.7-Bonding methods responsibility for the stated principles. The Institute shall not be liable for any loss or damage arising therefrom.

Reference to this document shall not be made in contract Chapter 3-Repair materials, p. 546R-20 documents. If items found in this document are desired by the 3.1-Introduction Architect/Engineer to be a part of the contract documents, they shall be restated in mandatory language for incorporation by 3.2-Cementitious materials the Architect/Engineer. 3.3-Polymer materials 3.4-Bonding materials It is the responsibility of the user of this document to 3.5-Coatings on reinforcement establish health and safety practices appropriate to the specific 3.6-Reinforcement circumstances involved with its use. ACI does not make any representations with regard to health and safety issues and the 3.7-Material selection use of this document. The user must determine the applicability of all regulatory limitations before applying the AC1 546R-04 supersedes ACI 546R-96 and became effective September 23, 2004.

document and must comply with all applicable laws and Copyright © 2004, American Concrete Institute.

regulations, including but not limited to, United States All rights reserved including rights of reproduction and use in any form or by any means, including the making of copies by any photo process, or by electronic or Occupational Safety and Health Administration (OSHA) mechanical device, printed, written, or oral, or recording for sound or visual reproduc-health and safety standards. tion or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors.

663

664 FM 7.8 Exhibit 2 CONCRETE REPAIR MANUAL page 2 of 8 Chapter 4-Protective systems, p. 546R-30 protection-the procedure of shielding the concrete struc-

4. 1-Introduction and selection factors ture from environmental and other damage for the purpose of 4.2-Concrete surface preparation and installation preserving the structure or prolonging its useful life.

requirements repair-to replace or correct deteriorated, damaged, or 4.3-Typical selection problems faulty materials, components, or elements of a structure.

4.4-Systems concept repair systems-the combination of materials and 4.5-Surface treatments techniques used in the repair of a structure.

4.6-Joint sealants strengthening-the process of restoring the capacity of 4.7-Cathodic protection damaged components of structural concrete to its original 4.8--Chloride extraction design capacity, or increasing the 'strength of structural 4.9-Realkalization concrete.

structural repair-a repair that re-establishes or Chapter 5-Strengthening techniques, p. 546R-41 enhances the structural capacity of a member.

5.1--General surface preparation-steps taken after removal of 5.2-Internal structural repair (restoration to original deteriorated concrete, including conditioning of the surface of member strength) substrate at bond line and the cleaning of existing reinforcing 5.3-Interior reinforcement steel.

5.4-Exterior reinforcement (encased and exposed) waterproofing-prevention of the passage of water, in 5.5-Exterior post-tensioning liquid form, under hydrostatic pressure.

5.6-Jackets and collars 5.7-Supplemental members 1.3-Repair methodology 5.8-Repair of concrete columns A basic understanding of the causes of concrete deficiencies 5.9-Column repair parameters is essential to perform meaningful evaluations and successful repairs. If the cause of a deficiency is understood, Chapter 6-References, p. 546R-48 it is much more likely that an appropriate repair system will be 6.1--Referenced standards and reports selected and, consequently, that the repair will be successful 6.2--Cited references and the maximum life of the repair will be obtained.

Symptoms or observations of a deficiency should be CHAPTER 1-INTRODUCTION differentiated from the actual cause of the deficiency, and it 1.1-Use of this document This document provides guidance on selection of materials is imperative that causes and not symptoms be dealt with and application methods for the repair, protection, and wherever possible or practical. For example, cracking can be strengthening of concrete structures. The information is a symptom of distress that may have a variety of causes such applicable to repiiring damaged or deteriorated concrete as drying shrinkage, thermal cycling, accidental over-structures, correcting design or construction deficiencies, or loading, corrosion of embedded metal, or inadequate design upgrading a structure for new uses or to meet more restrictive or construction. Only after the cause or causes of deficiency building codes. are determined can rational decisions be made regarding the This guide summarizes current practices in concrete repair selection of a proper repair system and the implementation and provides sufficient information for the initial planning of of the repair process (Fig. 1.1).

repair work and for selecting suitable repair materials and 1.3.1 Condition evaluation-The first step in concrete application 'methods for specific conditions. Many of the repair is to evaluate .the current condition of the concrete topics covered in this guide are more extensively covered in structure. This evaluation may include a review of available other ACI committee documents. Readers of this guide should design and construction documents, structural analysis of the refer to the appropriate documents of other ACI committees structure in its deteriorated condition, a review of available and other industry resources for additional infornation. test data, a review of records of any previous repair work, review of maintenance records, a visual inspection of the 1.2-Definitions structure, an evaluation of corrosion activity, destructive and corrosion-destruction of metal by chemical, electro- nondestructive testing, and review of laboratory results from chemical, or electrolytic reaction within its environment. chemical and petrographic analysis of concrete samples.

dampproofing-treatment of concrete or mortar to retard Upon completion of this evaluation step, the personnel the passage or absorption of water, or water vapor, either by responsible for the evaluation should have a thorough under-application of a suitable admixture or treated cement, or by standing of the condition of the concrete structure and be use of preformed film, such as polyethylene sheets, placed able to provide insights into the causes of the observed on grade before placing a slab. deterioration or distress. Additional information on excavation-steps taken to remove.deteriorated concrete, conducting surveys can be found in ACI 201.1R, 222R, sound concrete, or both, designated for removal. 224.1R, 228.2R, 364.1R, and 437R.

nonstructural repair-a repair that addresses local 1.3.2 Determination of causes of deterioration or deterioration and is not intended to affect the structural capacity distress-After the condition evaluation of a structure has of a member. been completed, the deterioration mechanism that caused the

668 FM 7.8 Exhibit 2 CONCRETE REPAIR MANUAL page 3 of 8 "behavior to evaluate and design a structural repair, strength- section. For example, if a beam's steel reinforcement has ening procedure, or both. Some design considerations follow corroded extensively and lost part of its load-carrying and are discussed throughout this guide. capacity, the steel reinforcement may be replaced by carbon 1.4.1 Current load distribution-In a deteriorated state, a fiber-reinforced polymer (CFRP) applied to the external structural member or system distributes dead and live loads bottom face of the beam. The original yielding behavior of the differently than first assumed when the structure was new. steel bar is replaced by FRP that is stronger, but has a more Cracking, deteriorated concrete and corroded reinforcement elastic and brittle behavior. The behavior assumptions of alter the stiffness of members, which leads to changes in codes like ACI 318 are no longer valid. The engineer should shear, moment, and axial load distribution. As concrete and consider the behavior and performance of the new repair reinforcement are removed and replaced during the repair under the actual service and ultimate load, and design the operation, these redistributed forces are further modified. To repair to provide at least an equivalent level of safety to the understand the final behavior of the structural system, the original design. Such a design is outside the scope ofACI 318.

engineer should evaluate the redistribution of the forces. To fully re-establish the original load distribution, a member 1.5-Format and organization should be relieved of the load by jacking or other means. The Chapter 2 discusses removal of deteriorated concrete, repaired member and the repair itself supports the loads differ- preparation of surfaces to receive repair materials, general ently than would be assumed in the original or a new structure. methods for concrete repair, and repair techniques for 1.4.2 Compatibility of materials-If a repair and the reinforcing and prestressing steel. Chapter 3 discusses member have the same stiffness-for example, modulus of various types of repair materials that may be used. The elasticity-the analysis of the repaired member may be the reader is urged to use Chapters 2 and 3 in combination same as a new section. If the stiffness varies, however, then when selecting the repair material and method for a given the composite nature of the repaired system should be situation. Chapter 4 describes materials and systems that considered. A mismatch of other material characteristics may be used to protect repaired or unrepaired concrete further exacerbates the effects of thermal changes, vibra- from deterioration. Chapter 5 provides methods for tions, and long-term creep and shrinkage effects. Different strengthening an existing structure when repairing deficiencies, coefficients of thermal expansion of the repair and original improving load-carrying capabilities, or both. Chapter 6 material results in different dimensional changes. The engineer provides, references, including other appropriate ACI should design for the different movements, or the repair documents and industry resources.

system should be similar to the thermal and dimensional characteristics of the original material. CHAPTER 2-CONCRETE REMOVAL, PREPARATION, AND REPAIR TECHNIQUES 1.4.3 Creep, shrinkage, or both-Reduction in length, 2.1-Introduction and general considerations area, or volume of both the repair and original materials due This chapter covers removal, excavation, or demolition of to creep, shrinkage, or both, affect the structures service- existing deteriorated concrete, preparation of the concrete ability and durability. As an example, compared with the surface to receive new material, preparation and repair of original material, high creep or shrinkage of repair materials reinforcement, methods for anchoring repair materials to the results in loss of stiffness of the repair, redistributed forces, existing concrete, and various methods that are available to and increased deformations. The engineer should consider place repair materials. The care that is exercised during the these effects in the design. removal and preparation phases of a repair project can be the 1.4.4 Vibration-When the installed repair material is in a most important factor in determining the longevity of the plastic state or until adequate strength has been developed, repair, regardless of the material or technique used.

vibration of a structure can result in reduced bonding of the Specific attention should be given to the removal of repair material. Isolating the repairs or eliminating the concrete around prestress strands, both bonded and vibration may be a design consideration. unbonded. The high-energy-impact tools, such as chipping 1.4.5 Water and vapormigration-Wateror vapor migration hammers, should avoid contact with the strand because this through a concrete structure can degrade a repair. Under- will reduce the strands' load-carrying capacity and may standing the cause of the migration and controlling it should cause the wire(s) to rupture, which may lead to strand failure.

be part of a repair design consideration.

1.4.6 Safety- The contractor is responsible for construction a2.2-Concrete removalI safety. Nevertheless, as the engineer considers a repair A" reTW ýodecl T*o alrli mvolves removal of deteriorated, design, which may involve substantial concrete removal, damaged, or defective concrete. In most concrete repair steel reinforcing cutting, or both, he or she should notify the projects, the zones of damaged concrete are not well defined.

contractor of the need and extent of shoring and bracing. The Most references state that all damaged or deteriorated material local repair of one small section can affect a much larger should be removed, but it is not always easy to determine area, of which the contractor may not be aware. when all such material has been removed or when too much 1.4.7 Material behavior characteristics-Whennew and good material has been removed. A common recommendation innovative materials and systems are used for repair and. is to remove sound concrete for a defined distance beyond strengthening, the structural behavior of the repaired section the delaminated area; thereby, exposing the reinforcing steel can differ substantially from the behavior of the original beyond the point of corroded steel.

FM 7.8 Exhibit 2 CONCRETE REPAIR GUIDE page 4 of 8 669 Removal of concrete using explosives or other aggressive 2.2.1 General considerations-Concrete removal methods can damage the concrete that is intended to remain addresses deteriorated and damaged material. Some sound in place. For example, blasting with explosives or the use of concrete, however, may be removed to permit structural some impact tools heavier than 12 kg (30 lb) can result in modifications and to ensure that all unsound material is additional delamination or cracking. Delaminated areas can removed. The effectiveness of various removal techniques be identified by using a hammer to take soundings. In most can differ for deteriorated and sound concrete. Some techniques cases, such delaminations should be removed before repair may be more effective in sound concrete, while others may materials are placed. work better for deteriorated concrete.

, ~'cwncreteY no a zie'r'vM using mac tools 'may Tsreutin Concrete removal techniques selected should be effective, small-scale microcracking damage (termed bruising) to the: safe, economical, environmentally friendly, and minimize surface j .ofthe concrete left in pce Unless this damaed damage to the concrete left in place. The removal technique layer is removed, a weakened plane may occur in the parent chosen may have a significant effect on the length of time concrete below the repair material bondline. This condition that a structure will be out of service. Some techniques can result in a low tensile rupture (bond) strength between permit a significant portion of the work to be accomplished the parent concrete and repair material. Thus, a perfectly without removing the structure from service. The same sound and acceptable replacement material may fail due to removal technique, however, may not be suitable for all improper surface preparation. All damaged or delaminated portions of a given structure. In some instances, a combination concrete, including bruising, at the interface of the repair and of removal techniques may be more appropriate to speed the parent concrete should be removed before placing the removal and limit damage to the remaining sound concrete.

repair material. This may require one type of aggressive Trial field testing various removal techniques can help removal for gross removal followed by another type of confirm the best procedures.

removal for bruising. In general, the engineer responsible for the design of the a 'N~e~iZF concrsts'1~ ef;fjlm a: repair should specify the objectives to be achieved by the structure by primary means such as blasting or aggressive. concrete removal, and the repair contractor should be a impact methods, the concrete left in place should be prepared allowed to select the most economical removal method,

by using a secondary method,---ch-as-chipping, abrasive :

subject to the engineer's acceptance. In special circum-blasting, or ah.igh-pressure water jetting,'

to remove any0 stances, the engineer may also need to specify the removal oremaining damaged surface material. Careful visual inspections techniques to be used and those that are prohibited.

of the prepared surfaces should be conducted before placing The mechanical properties of the concrete and the type and repair materials. Wetting the surface may help to identify the size of aggregate to be removed provide important information presence of cracking. Determination of the tensile strength to determine the method and cost of concrete removal. The (ACI 503R, Appendix A) by pull-off testing is advisable on mechanical properties include compressive and tensile prepared surfaces to determine the suitability of the surface strengths. This information is also necessary for the engineer to receive repair material. to specify the prepared surface condition and select the repair Removal of limited areas of concrete in a slab, wall, or material, and it should be made available to contractors for column surface requires saw-cutting the perimeter of the bidding purposes.

removal area, providing an adequate minimum thickness of 2.2.2 Monitoring and shoring during removal opera-repair material at the edge of the repaired area, and mitigating tions-It is essential to evaluate the removal operations to the advancement of undetected incipient cracking. Feathering limit the extent of damage to the structure and to the concrete of repair materials generally should be avoided. The prep- that remains. Structural elements may require shoring, aration for shotcreting is an exception. ACI 506R recom- removal of applied loads, or both, before concrete removal to mends tapered edges around the perimeter of such patches. prevent structural deformations, possible collapse, buckling, Saw cutting can also improve the appearance of the repaired or slippage of reinforcement. Care should be used during area. The general shape of the repaired areas should be as removal of concrete to avoid cutting and damaging rein-symmetrical as possible (ICRI 03730). Reentrant comers forcing steel. Because reinforcement is often misplaced, should be avoided. Large variations in the depth of removal unanticipated damage may occur when saw cutting, in short distances should also be avoided. The texture of the impacting, or removing concrete.

prepared surface should be appropriate for the intended Careful monitoring is required throughout the concrete repair material (ICRI 03732). removal operation. This can be accomplished by visual Every precaution should be made to avoid cutting under- inspection, sounding, use of a covermeter, or other means to lying reinforcement. Reviewing design drawings and using a locate reinforcement. The project specifications should assign covenreter or similar device provides data as to the location responsibilities for the inspection of the prepared concrete.

and depth of reinforcement. In addition, the removal of small Sounding is an excellent means to detect delaminated areas of concrete is commonly used to confirm the location concrete adjacent to the outermost layers of reinforcing steel.

and depth of bars before saw cutting. Subsurface cracks, the extent of deterioration, or other Sections 2.2.1 through 2.2.18 present descriptions of many internal defects, however, may not be identified by this of the commonly used concrete removal techniques to help method alone. Other means of evaluation should be used to in the selection process. properly identify the extent of concrete to be removed. In

670 FM 7.8 Exhibit 2 CONCRETE REPAIR MANUAL page 5 of 8 addition, sounding usually does not indicate near-surface remains after blasting. One such technique, cushion blasting, microcracking or bruising. Only microscopic examination or involves drilling a line of 75 mnm (3 in.) diameter or smaller bond testing may disclose near-surface damage. bore holes parallel to the removal face, loading each hole with Subsurface evaluation (examination of the substrate) can light charges of explosive (usually detonating cord) distributed provide valuable information about the condition of the along its length, cushioning the charges by stemming each concrete. This information may be obtained by the hole completely or in the collar with wet sand, and detonating following methods before, during, or after concrete removal the explosive with electric blasting caps. The "Uniform (ACI 228.2R): distribution and cushioning of the light charges produce a a) Taking cores for visual examination, microscopic relatively sound surface with little overbreak.

examination, compressive strength tests, and splitting- Blasting machines and electrical blasting-cap delay series tensile strength tests; are also used for controlled demolition and employ proper b) Pulse-velocity tests; timing sequences to provide greater control in reducing c) Impact-echo tests; ground vibration. Controlled blasting has been used success-d) Bond tests (pull-off testing, ACI 503R Appendix A); fully on numerous repair projects. The selection of proper e) Coverneter or similar equipment to locate reinforce- charge weight, borehole diameter, and borehole spacing for ment and determine its depth below the surface; a repair project depends on the location of the structure, the f) Infrared thermography; and acceptable degree of vibration and damage, and the quantity g) Ground-penetrating radar (GPR). and quality of concrete to be removed. If at all possible, a Many of these methods are discussed in ACI 228.2R. pilot test program should be implemented to determine the 2.2.3 Quantity of concrete to be removed-In most repair optimum parameters. Because of the inherent dangers in the projects, all damaged or deteriorated concrete should be handling and usage of explosives, all phases of the blasting removed; however, the quantity of concrete to be removed is project should be performed by qualified, appropriately directly related to the elapsed time between preparation of licensed personnel with proven experience and ability.

the estimate and actual removal. Substantial overruns are 2.2.6 Cutting methods-Cutting methods generally common. Estimating inaccuracies can be minimized by a employ mechanical sawing, intense heat, or high-pressure thorough condition survey as close as possible to the time the water jets to cut around the perimeter of concrete sections to repair work is executed. Potential quantity overruns, based permit their removal. The size of the sections that are cut free on field-measured quantities, should be taken into account. is governed by the available lifting and transporting When, by necessity, the condition survey is done far in equipment. The cutting methods include high-pressure advance of the repair work, the estimated quantities should water jets, saw cutting, diamond wire cutting, mechanical be increased to account for continued deterioration. Because shearing, stitch drilling, and thermal cuttin..

most concrete repair projects are based on unit prices, repair a)High-pressure waterjet (without abrasives)-A high-areas should be accurately measured before forms are a pressure water jet uses a small jet of water driven at high installed. This is usually done jointly by the engineer and the velocities, commonly producing pressures of 69 to 310 MPa contractor. It is not uncommon for estimated quantities to (10,000 to 45,000 psi). A number of different types of water:

increase significantly between the detectable quantities and jets are currently being used. The most promising are the:

the actual quantity removed. ICRI 03735 provides guidelines ultra high-pressure jet and the cavitating jet. Section 2.2.10 for methods of measurement for concrete repair work. describes using a water jet as a primary removal method. a 2.2.4 Classification of concrete removal methods- Water jets used with abrasives are described in Section a Removal and excavation methods can be categorized by the a 2.2.11. a way in which the process acts on the concrete. These categories b) Saw cutting-Diamond or carbide saws are available in are blasting, cutting, impacting, milling, hydrodemolition, sizes ranging from small (capable of being hand-held) to presplitting, and abrading. Table 2.1 provides a general large (capable of cutting depths of up to 1.3 m [52 in.]).

description of these categories, lists the specific removal c) Diamond wire cutting-Diamond wire cutting is techniques within each category, and provides a summary of accomplished with a wire containing nodules impregnated information on each technique. The techniques are discussed with diamonds. The wire is wrapped around the concrete in detail in the following sections. mass to be cut and reconnected with the power pack to form 2.2.5 Blasting methods-Blasting methods generally a continuous loop. The loop is spun in the plane of the cut employ rapidly expanding gas confined within a series of while being drawn through the concrete member. This bore holes to produce controlled fracture and removal of the system can be used to cut a structure of any size as long as concrete. The only blasting method addressed in this report the wire can be wrapped around the concrete. The limits of is explosive blasting. the power source deternmines the size of the concrete structure Explosive blasting is the most cost-effective and expedient that can be cut. This system provides an efficient method for means for removing large quantities of concrete-for cutting up and dismantling large or small concrete structures.

example, portions of large mass concrete foundations or walls. d) Mechanicalshearing-The mechanical shearing method This method involves drilling bore holes, placing an explosive employs hydraulically powered jaws to cut concrete and in each hole, and detonating the explosive. Controlled- reinforcing steel. This method is applicable for making blasting techniques minimize damage to the material that cutouts through slabs, decks, and other thin concrete

FM 7.8 Exhibit 2 CONCRETE REPAIR GUIDE page 6 of 8 671 Table 2.1- Summary of features and considerationsllimitations for concrete removal methods Category Features Considerations/Limitations 2.2.5 Blasting Explosives Uses rapidly expanding gas confined within a series of Most expedient method for removing large volumes Requires highly skilled personnel for design and execution.

boreholes to produce controlled fracture and removal of where concrete section is 10 in. (250 mm) thick or more. Stringent safety regulations must be complied with regarding concrete. Produces good fragmentation of concrete debris for easy the transportation, storage, and use of explosives due to removal, their inherent dangers.

Blast energy must be controlled to avoid damage to surrounding improvements resulting from air blast

2.2.6 Cutting High-pressure waterjet (without abrasives) 0 Uses perimeter cuts to remove large pieces of concrete. Applicable for making cutouts through slabs, decks, and Cutouts for removal limited to thin sections.

O other thin concrete members. Cutting is typically slower and more costly than diamond Cuts irregular and curved shapes, blade sawing.

O Makes ctouts without overcutting comers. Moderate levels of noise may be produced. -eI Cuts flush with intersecting surfaces. Controlling flow of waste water may be required.

o I'ro Meat,*VýbVlooXr uso is troduccde a- Additional safety precautions are required due to the high Handling of debris is efficient because bulk of concrete is water pressure produced by the system.

removed in large pieces.

o 2.2.6 curtin(eontined2.. . .. . Diantondsaw , . . .

Applicable for making cutouts through slabs, decks, and Cutouts for removal limited to thin sections.

other thin concrete members. Performance is affected by type of diamonds and the dia-Makes precision cuts. mond-to-metal bond in blade segments (segment sclec-No dust or vibration is produced. tion is based on aggregate hardness).

Handling of debris is efficient because bulk of concrete is The higher the percentage of steel reinforcement in cuts, removed in large pieces, the slower and more costly the cutting.

The harder the aggregate, the slower and more costly the cutting.

Controlling flow of waste water may be required.

2.2.6 Cutting(continued) Diamond wire cutting Applicable for cutting large and/or thick pieces of concrete. The cutting chain must be continuous.

The diamond wire chain can be infinitely long. Access to drill holes through the concrete must be available.

No dust or vibration is produced. Water must be available to the chain.

Large blocks of concrete can be easily lifted out by a Controlling the flow of waste water may be required.

crane or other mechanical methods. The harder the aggregate and/or concrete, the slower and The cutting operation can be equally efficient in any more costly the cutting.

direction. Performance is affected by the quality, type, and number of diamonds as well as the diamond-to-metal bond in the chain.

2.2.6 Cutting (continued) Mechanicalshearing Applicable for making cutouts through slabs, decks, and Limited to thin sections where an edge is available or other thin concrete members, a hole can be made to start the cut.

Steel reinforcement can be cut. Exposed reinforcing steel is damaged beyond reuse.

Limited noise and vibration are produced. Remaining concrete is damaged.

Handling of debris is efficient because bulk of concrete is Extremely rugged profile is produced at the cut edge.

removed in large pieces. Ragged feather edges remain after removal.

2.2.6 Cutting (continued) Stitch drilling Applicable for making cutouts through concrete members Rotary-percussion drilling is significantly more expedient where access to only one face is feasible. -and economical than diamond core drilling; however, it Handling of debris is more efficient because bulk of results in more damage to the concrete that remains, concrete is removed in large pieces, especially at the point of exit from the concrete.

Depth of cuts is dependent on accuracy of drilling equip-ment in maintaining overlap between holes with depth and diameter of the boreholes drilled. The deeper the cut, the greater borehole diameter required to maintain over-lap between adjacent holes and the greater the cost.

Uncut portions between adjacent boreholes will hamper or prevent the removal.

Cutting reinforced concrete increases the cutting time and increases the cost. Aggregate toughness for percussion drilling and aggregate hardness for diamond coring will affect cutting cost and rate.

Personnel must wear hearing protection due to high noise levels.

members. It is especially applicable where total demolition of the drilling equipment, so that uncut concrete remains of the member is desired. The major limitation of this method between adjacent holes.

is that cuts should be started from free edges or from holes f) Thermal cutting-This method requires powder torch, made by hand-held breakers or other means.

thermal lance, and powder lance, which develop intense heat e) Stitch drilling-The stitch-drilling method employs the generated by the reaction between oxygen and powdered use of overlapping boreholes along the removal perimeter to metals to melt a slot into concrete. The thermal device's ability cut out sections for removal. This method is applicable for making cutouts through concrete members where access to for removing concrete from structures mainly depends on the only one.face is possible, and the depth of cut is greater than rate at which the resulting slag can flow from the slot. These can be economically cut by the diamond-blade method. The devices use intense heat and are especially effective for cutting primary drawback of stitch drilling is the potential for costly reinforced concrete; however, they are considered slow, removal complications if the cutting depth exceeds the accuracy relatively expensive, and are not widely used.

672 FM 7.8 Exhibit 2 CONCRETE REPAIR MANUAL page 7 of 8 Table 2.1 (cont.)-Summary of features and considerationsllimitations for concrete removal methods Category Features Considerations/Limitations 2.2.6 Cutting(continued) Thermal cutting Applicable for making cutouts through heavily reinforced Limited availability commercially.

decks, beams, walls, and other thin to medium concrete Not applicable for cuts where slag flow is restricted.

members. Remaining concrete has thermal damage with more extensive An effective means of cutting reinforced concrete, damage occurring around steel reinforcement.

Cuts irregular shapes. Produces smoke and fumes.

Produces minimal noise, vibrations, and dust. Personnel must be protected from heat and hot slag produced by cutting operation.

2.2.7 Impacting Hand-held breakers Uses repeated striking of the surface with a mass to fracture Applicable for limited volumes of concrete removal. Performance is a function of concrete soundness and and spall the concrete. Applicable where blow energy must be limited, aggregate toughness.

Widely available commercially. Significant action is other of productivity occurs when breaking lossthan Can be used in areas of limited work space. acini*te ta downward.

onad Removal boundaries will likely require saw cutting to Produces relatively small and easily handled debris, avoid feathered edges.

Concrete that remains may be damaged (microcracking).

Produces high levels of noise, dust, and vibration.

Boomn-mounted breakers Applicable for full-depth removal from slabs, decks, and Blow energy delivered to the concrete may have to be other thin concrete members and for surface removal limited to protect the structure being repaired and the from more massive concrete structures. surrounding structures from damage due to high cyclic Can be used for vertical and overhead surfaces, energy generated.

Widely available commercially. Performance is a function of concrete soundness and Produces easily handled debris, aggregate toughness.

Damages remaining concrete.

Damages reinforcing steel' Produces feathered edges.

Produces high level of noise and dust.

2.2.7 Impacting(continued) Scabblers Low initial cost. High cyclic energy applied to a structure will produce Can be operated by unskilled labor. fractures in the remaining concrete surface area.

Can be used in areas of limited work space. Produces high level of noise and dust.

Removes deteriorated concrete from wall or floor surfaces Limited depth removal.

efficiently.

Readily available commercially.

2.2.8 Milling Scarifier Uses scarifiers to remove concrete surfaces. Applicable for removing deteriorated concrete surfaces Removal is limited to concrete without steel reinforcement.

from slabs, decks, and mass concrete. Sound concrete significantly reduces the'rate of removal.

Boom-mounted cutters are applicable for removal from Can damage concrete that remains (microcracking).

wall and ceiling surfaces. Noise, vibration, and dust are produced.

Removal profile can be controlled.

I . . . . . . . . . ..... . . . . . . . . . . . . ... WstbcW pr ca,'.ia v lsanlaasi~y dI idobri ..

a ........................ _._ .. . a 2.2.9 Hydrodentolition Applicable for removal of deteriorated concrete from Productivity is significantly reduced when soand concrete is Uses high-pressure water to remove concrete, surfaces of bridges and parking decks and other deteriorated being removed.

surfaces where removal depth is 6 in. (150 mm) or less. Removal profile will vary with changes in depth of SDoes n o7 Xamage t e concr*tes taTt rmains,. a deterioration. a Steel reinforcing is left clean and undamaged for reuse. Method requires large source of potable water to meet a Method produces easily handled, aggregate-sized debris, water demand.

Waste water may have to be controlled. a An environmental impact statement may be required if a waste water is to enter a waterwa". a a Personnel must wear hearing protection due to the high a a Flying debris is produced. a Additional safety requirements are required due to the a high pressures produced by these systems. a 2.2.7 Impacting methods-Impacting methods are the sive blasting, and water blasting, may be required to remove most commonly used concrete removal systems. They excessive microcracking.

repeatedly strike a concrete surface with a high-energy tool a) Hand-heldbreakers-The hand-held breaker or chipping or a large mass to fracture and spall the concrete. The use of hammer is probably the best known of all concrete removal these methods in partial-depth concrete removal can result in devices. Hand-held breakers are available in various sizes microcracking on the surface of the concrete left in place. with different levels of energy and efficiency. These tools Extensive microcracking results in a weakened plane below are generally defined by weight and vary in size from 3.5 to the bond line. Currently, the committee is unable to provide 41 kg (8 to 90 lb). (Note: the larger the hammer, such as 14 kg definitive guidelines to prevent such damage when using [30 lb] and larger,, the greater the potential for microc-impact methods; however, factors such as the weight and racking.) The smaller hand-held breakers, such as 7 kg (15 lb) size of the equipment should be considered to minimize and smaller, are used in partial removal of unsound concrete microcracking. Determination of the tensile strength by pull- or concrete around reinforcing steel because they do little off testing is recormnended to determine the suitability of the damage to surrounding concrete. Larger breakers are used surface to receive repair materials. Additionally, after for complete removal of large volumes of concrete or delam-impacting secondary methods, such as sandblasting, abra- inations. Care should be exercised when selecting the size of

ý74 FM 7.8 Exhibit 2 CONCRETE REP)AIR MANUAL page 8 of 8 (0.1 to 4 in.). Milling operations usually leave a sound into sections. This method has potential as a primary means surface with less microfractures than impact methods for removal of large volumes of material from mass concrete (Virginia Transportation Research Council 2001). structures. Secondary means of separating and handling the 2.2.9 Scarifler-A scarifier is a concrete cutting tool that concrete, however, may be required where reinforcing steel employs the rotary action and mass of its cutter bits to rout is involved.

cuts into concrete surfaces. It removes loose concrete b) Water-pulse splitter-Thewater-pressure pulse method fragments (scale) from freshly blasted surfaces and removes requires that the boreholes be filled with water. A device, or concrete that is cracked and weakened by an expansive devices, containing a very small explosive charge is placed agent. It also is the sole method of removing deteriorated and into one or more holes, and the explosive is detonated. The sound concrete in which some of the concrete contains form explosion creates a high-pressure pulse that is transmitted ties and wire mesh. Scarifiers are available in a range of through the water to the structure, cracking the concrete.

sizes. The scarifier is an effective tool for removing deteriorated Secondary means may be required to complete the removal concrete on vertical and horizontal surfaces. Other advantages of reinforced concrete. This method does not work if the include well-defined limits of concrete removal, relatively concrete is so badly cracked or deteriorated that it does not small and easily handled concrete debris, and simplicity hold water in the drill holes.

of operation. c) Expansive product agents-Commercially available

- '2'.2.10 7y;d&Y;e Toii5-Rgl'hýpress~u-r-vrew ti'n-g _: cementitious expansive product agents, such as those jte~

,(hydrodemolition) can be used to remove concrete to containing aluminum powder, when correctly mixed with preserve and clean the steel reinforcement for reuse and to water, exhibit a large increase in volume over a short period

, a minlnmize mlcrocracklnuto thle remainin in-nrace concrele of time. By placing the expansive agent in boreholes located The method also has a high efficiency. Hydrodemolition' a in a predetermined pattern within a concrete structure, the disintegrates concrete, returning it to sand and gravel-sized a concrete can be split in a controlled manner for removal.

pieces. This process works on sound or deteriorated concrete a This technique has potential as a primary means of removing and leaves a rough profile. Hydrodemolition punches through a large volumes of material from concrete structures and is the full depth of slabs in small areas when the concrete is a best suited for use in holes of significant depth. Secondary unsound or when full-depth patches are inadequately bonded a means may be required to complete the separation and Uo to !srteM *al*. f'lyJr~ ýitellon sM"urd' not U:ed*in removal of concrete from the reinforcement. A key advantage

%structures with unbonded tendons, except under the direct aa to the use of expansive agents is the relatively nonviolent

%sunervision of a structural engineer. 0 nature of the process and the reduced tendency to disturb the High-pressure water jets in the 70 MPa (10,000 psi) range adjacent concrete.

require 130 to 150 L/min (35 to 40 gal./min). As the pressure a 2.2.12 Abrading blasting-Abrading blasting removes increases to 100 to 140 MPa (15,000 to 20,000 psi), the water a concrete by propelling an abrasive medium at high velocity demand varies from 75 to 150 L/min (20 to 40 gal./min)a against the concrete surface to abrade it. Abrasive blasting is (Nittenger 1997). The equipment manufacturer should be a typically used to remove surface contaminants and as a final consulted to confirm the water demand. Ultra-high-pressure a surface preparation. Commonly used methods include sand-equipment operating at 170 to 240 MPa (25,000 to 35,000 psi) a blasting, shotblasting, and high-pressure water blasting.

has the capability of milling concrete to depths of 3 to 150 mim a 2.2.13 Sandblasting-Sandblastingis the most colnmonly (0.1 to 6 in.). Containment and subsequent disposal of the a used method of cleaning concrete and reinforcing steel in the water are requirements of the hydrodemolition process. a construction industry. The process uses common sands, Many localities require this water to be filtered and then a silica sands, or metallic sands as the primary abrading tool.

treated to reduce the alkalinity and particulates before the a The process may be executed in one of three methods.

water can be released into a storm or wastewater system. a 2.2.14 Dry sandblasting-Sands are projected at the Water jet lances operating at pressures of 70 to 140 MPa a concrete or steel in a stream of high-pressure air in the open (10,000 to 20,000 psi) and having a water demand of 75 toa atmosphere. The sand particles are usually angular and may 150 L/min (20 to 40 gal./min) are available. They are capable a range in size from passing a 212 to a 4.75 mm (No. 70 to a of cutting sections of concrete or selectively removinga No. 4) sieve. The rougher the required surface condition, the surface concrete in areas that are difficult to reach with larger a larger the sand particle size.

a ecuinment (ICR10373 7)* a The sand particles are propelled at the surface in a stream 2.2.11 Presplitting rnethods-Presplitting methods use of compressed air at a minimum pressure of 860 kPa (125 psi).

hydraulic splitters, water pressure pulses, or expansive chem- The compressor size varies, depending on the size of the sand-icals used in boreholes drilled at points along a predetermined blasting pot. Finer sands are used for removing contaminants line to induce a crack plane for the removal of concrete. The and laitance from the -concrete and loose scale from rein-pattern, spacing, and depth of the boreholes affect the forcing steel. Coarser sands are commonly used to expose fine direction and extent of the crack planes that propagate. and coarse aggregates in the concrete by removing the paste or Presplitting is generally used in mass concrete structures or tightly bonded corrosion products from reinforcing steel.

unreinforced concrete. Although sandblasting has the ability to cut quite deeply into a) Hydraulicsplitter-The hydraulic splitter is a wedging concrete, it is not economically practical to remove more device that is used in predrilled boreholes to split concrete than 6 mm (0.25 in.) from the concrete surface.

FM 7.8 Exhibit 3 page 1 of 5 MAC & MAC HYDRODEMOLITION SERVICES INC.

Suite D-13, 301 West Holly Street, Bellingham, WA 98225 Tel: 1 800665.7772 9 Fax: 1 800 661.1178 Email: info@macandmac.com State of Washington Contractor License #MACMAHS996NB State of California Contractor License #80 PROGRESS ENERGY SERVICE COMPANY, LLC CRYSTAL RIVER THREE (CR3) NUCLEAR PLANT CRYSTAL RIVER, FLORIDA HYDRODEMOLITION WORK PLAN PROJECT Create a temporary opening in the CTMT wall removing all concrete using high pressure Hydrodemolition technology.

HYDRODEMOLITION EQUIPMENT 2 - 2000HP diesel pumping unit power packs. Each power pack contains 3 high pressure pumping units delivering 50 gpm @ 20,000 psi per pump to a Hydrodemolition nozzle mounted on the Hydrodemolition concrete removal track.

HYDRODEMOLITION CONCRETE REMOVAL TRACK Stationed on access platform at temporary opening location. Track frame mounted on CTMT wall exterior outline of concrete to be removed 28' wide x 24' high.

Frame has two Hydrodemolition concrete manipulators mounted side by side, each covering 14' wide x 24' high Each manipulator contains three Hydrodemolition nozzles. Each nozzle is connected to a high pressure pump in the power pack.

HYDRODEMOLITION PROCESS Each manipulator passes over the surface removing concrete as it travels width wise one pass then index up 2 inches repeating the process until it reaches the top of the track (24' level). To prevent over cutting steel stops are installed at the 24' level.

When rebar is exposed manipulator is locked in place above the top (24') level while crews remove the rebar below. (Approx. 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />)

When rebar is removed Hydrodemolition resumes until Tendons are exposed. When tendons are exposed manipulators are locked in place above the top (24') level while crews remove and plug the tendons below. (Approx. 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />)

FM 7.8 Exhibit 3 page 2 of 5 MAC & MAC HYDRODEMOLITION SERVICES INC.

Suite D-13, 301 West Holly Street, Bellingham, WA 98225 Tel: 1 800 665.7772 9 Fax: 1 800661,1178 Email: info@macandmac.com State of Washington Contractor License #MACMAHS996NB State of California Contractor License #800844 When tendons are removed Hydrodemolition resumes until Liner plate is completely exposed.

When Liner plate is completely exposed Manipulators are locked in place until clear access is available to dismantle Frame.

RUBBLE CONTROL As Hydrodemolition is in progress the water and concrete rubble will fall down to the platform into a chute running down to rubble and wastewater containers located on the ground.

To prevent rubble from escaping the immediate area a screen hoarding will be erected around the Hydrodemolition track.

HYDRODEMOLITION EQUIPMENT STAGING 2 active Hydrodemolition power packs to be setup approx. 400' from reactor opening location.

Three hoses will run from each power pack to the Hydrodemolition Track. =

2 - power packs = 6 hoses supplying two 3 nozzle manipulators mounted on the Hydrodemolition track.

1 backup power pack ready to operate less high pressure hoses will be staged also.

WATER CONTROL Wastewater will be pumped from bins at the CTMT to wastewater treatment location in the staging area approx.400' away.

Discharged waste water will be:

• 6.0-9.0 PH

• Total suspended solids, 30ppm

• Oil in water, daily maximum of 18.4 ppm with a monthly average below 13.8 ppm

• List of all fluids, lubricants will be submitted for approval ACTIVITIES

FM 7.8 Exhibit 3 page 3 of 5 MAC & MAC HYDRODEMOLITION SERVICES INC.

Suite D-13, 301 West Holly Street, Bellingham, WA 98225 Tel: 1 800 665.7772 9 Fax: 1 800 661.1178 Email: info@macandmac.com State of Washington Contractor License #MACMAHS996NB State of California Contractor License #800844 0 6 months prior to commencing Hydrodemolition submit superintendent name for security clearance

• 2-3 months (to be determined) prior to commencing Hydrodemolition Mac & Mac superintendent arrives onsite a 2 -3 months prior to commencing Hydrodemolition submit crew names for security clearance a 3 weeks prior to commencing Hydrodemolition crew arrives for Security, Fitness-For-Duty, Health Physics, Badging, Setup equipment,

• 3 weeks prior to commencing Hydrodemolition, Hydrodemolition power packs, tracks, manipulators/robots, all accessories and supplies arrive on site.

• 3 weeks prior to commencing Hydrodemolition all wastewater equipment, tanks, pumps arrive on site

• 3 weeks prior to commencing Hydrodemolition all vacuum truck units arrive on site THIRD WEEK BEFORE COMMENCING HYDRODEMOLITION

• Crew clearance completed (4 days)

• Stage Hydrodemolition power packs in Staging area approx. 400' from CTMT

• Stage and Assemble wastewater treatment facility in Staging area approx. 400' from CTMT SECOND WEEK BEFORE COMMENCING HYDRODEMOLITION

• Run High Pressure lines to CTMT location

• Run Wastewater lines from CTMT to Staging area approx. 400' from CTMT

• Run fresh water line from source to Hydrodemolition power packs in staging area approx. 400' from CTMT

• Install trash pump at containment bin to pump water to treatment facility approx.

400' from CTMT

• Install piping from treatment center to settling pond

• Build berm around equipment in staging area

FM 7.8 Exhibit 3 page 4 of 5 MAC & MAC HYDRODEMOLITION SERVICES INC.

Suite D-13, 301 West Holly Street, Bellingham, WA 98225 Tel: 1 800 665.7772 9 Fax: 1 800 661.1178 Email: info@macandmac.com State of Washington Contractor License #MACMAHS996NB State of California Contractor License #800844 ASSEMBLE HYDRODEMOLITION TOWER

• Assemble Tower on the ground outside of compound - small (60 ton) crane required for 3 days and a 8,0001b forklift

• Lift Assembled Tower onto chipping platform - crane required

• Bolt Tower Guide Legs onto chipping platform

• Run all hydraulic (water soluble oil), electrical, and pressure lines from Power Pack located outside of compound to Tower. (run lines under fence)

• Hookup high pressure hoses, hydraulic and electrical lines to Hydrodemolition manipulators (Manipulators are attached to the track. Track is attached to Tower)

" Place 125 ft. manlift in position

• Mount Hydrodemolition Control box in 125 ft. manlift bucket (Operator/Technician location / station)

• Test High pressure lines, electrical and hydraulic lines and controls

• Place 8' x 20' (2-8x1 0) sheets of steel on platform against reactor wall for testing system

• Test: Tower / Track system, High pressure system, hydraulic and electrical controls ONE WEEK BEFORE COMMENCING HYDRODEMOLITION

• Complete projects (if any) not completed in week 2

• Fine tune all equipment

• Standby ready to begin Hydrodemolition 3 days prior to commencement date and time.

HYDRODEMOLITION COMMENCED

• Cutting Concrete removing 13% (13% of total) 4 Hours

• Remove rebar 12 Hours by others

• Cutting Concrete removing 17% (30% of total) 6 Hours

• Remove and plug tendons 12 Hours by others

• Cutting Concrete removing 23% (53% of total) 8 Hours

• Cutting Concrete removing 24% (77% of total) 8 Hours

• Cutting Concrete removing 13% (90% of total) 4 Hours

• Cutting Concrete removing 10% (100% of total) 4 Hours

FM 7.8 Exhibit 3 page 5 of 5 MAC & MAC HYDRODEMOLITION SERVICES INC.

Suite D-13, 301 West Holly Street, Bellingham, WA 98225 Tel: 1 800 665.7772

• Fax: 1 800 661.1178 Email: info@macandmac.com State of Washington Contractor License #MACMAHS996NB State of California Contractor License #800844

" Cutting concrete perimeter clean up allowance 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />

• Hydrodemolition Equipment Demob 2 Days

• Water Treatment Demob 4 Days At all times Mac & Mac's project superintendent will keep Progress Energy representatives aware of our project progress and status.

FM 7.8 Exhibit 4 page 1 of 1 10/28/2009 Interview Dave McNeilt on phone Present: Dave McNeill (Mac&Mac, Vancouver), Craig Miller, Chong Chiu, Patrick Berbon Hydrolazing uses high-pressure pumps (triplex) with plungers (3 cylinders per pump).

Have X-Y machine on the platform.

Using 6 pressure pumps (1 pump per nozzle).

17,000-17,500 psi water pressure.

Flow rate 40-45 gallons/minute/nozzle.

Running 2 x 3 nozzles at the same time (3 nozzles per head, 2 heads).

Nozzle rotates at 500 rpm and projects water at a 5 degrees angle around the axis of rotation. Spin rate can be adjusted from 250 to 1,000 rpm. Was fixed at 500 rpm here.

Cut about 4 feet wide per head (total width of cut about 8' per pass).

Travels 1 ft/s along the beam, then move up 1.5 in, travels back 1 ft/s.

Each pass cuts 1in to 1.5in deep.

Nozzles are 7 inches apart.

Water is taken from Progress large holding tank. It is pumped up from the tank and filtered to 1 micron.

It is recovered and re-filtered at the end (not recycled, dumped in settling pond after use).

Supply water is usually around 60 F. it was 85 F in this case. The pumping added an additional 25 F so that the water exited the nozzle around 110 F.

Mac&Mac works on many bridge decks. First nuclear project for the company.

Their in-house calculations for 17,000 psi, 500 rpm rotation, 40 gal/min water, lft/s travel, shows a force on the wall of 100 psi.

Nozzle is 1/8 inch.

First nozzle is 2-4 in from the wall, second nozzle is 3-5 in, third nozzle is 4-6 in (nozzles are in same plane, but distance increases as material is removed by each nozzle).

Takes approximately 35 min for one pass.

Pump is diesel powered (1,800 rpm), runs at 500 rpm.

Pistons are 1.5 in diameter, and move back-and-forth at 500 rpm.

FM 7.8 Exhibit 5 page 1 of 1 10/29/2009 Interview Bob Nettinger at American Hydro Present: Chong Chiu, Dan Fiorello (Exelon), Partha Ghosal (Southern Company), Patrick Berbon Bob Nettinger is with American Hydro. They are a competitor company to Mac & Mac, who performed the hydro-blasting for the CR3 containment.

They have done 7 post-tensioned containments.

They use 6 HP pumps, 2 robots.

Rotating jets lead to a better cut.

20,000 psi water, 150 gal/min/nozzle.

Use a plunger pump.

Wayne Younger (also works at American Hydro) would know the numbers for vibration and rpm.

Tower is 5Oft high, can move on the platform, 4-wheel vehicle, 6ft wide cut top to bottom and back, 25ft from the wall.

1.5 inches deep cut per nozzle.

Nozzle is 6 inches from the wall.

They use nozzle extensions to get closer to the wall as they hydro-blast.

Use potable water as input into the pumps.

They are starting at TMI on Sunday, 11/1. John Piazza, structural engineer, senior design engineer on SG replacement at TMI.

Wayne Younger and Bob Nettinger called back later. They require PII to sign a NDA before giving additional information. It seems there is a lawsuit going on between American Hydro and Mac & Mac.