ML092610651
| ML092610651 | |
| Person / Time | |
|---|---|
| Site: | 07000925 |
| Issue date: | 06/15/1998 |
| From: | Jim Larsen Cimarron Corp |
| To: | Kenneth Kalman NRC/NMSS/DWM |
| References | |
| NUDOCS 9806220255 | |
| Download: ML092610651 (37) | |
Text
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CIMARRON CORPORATION P.O. BOX 25861 OKLAHOMA CITY, OKLAHOMA 73125 S.J. Larsen Vice President June 15, 1998 Mr. Ken Kalman, Project Manager Facilities Decommissioning Section Low Level Waste & Decom. Project Branch Div. Of Waste Management Office of Nuclear Mat'l Safety & Safeguards U.S. Nuclear Regulatory Commission Washington, D.C.
20555-0001 RE:
Docket No.70-925; License No. SNM-928 Response to NRC Comments on the Final Status Survey Report for Concrete Rubble in Sub-Area "F"
Dear Mr. Kalman:
Attached please find our responses to NRC Comments on the FSSR for concrete rubble in sub-area "F", that were transmitted to us via your letter dated May 20, 1998. The other issues raised in your May 2 0 th letter will be addressed via separate submittals. I trust that our responses are satisfactory and that you will be able to approve the release of the concrete rubble shortly after review of the attached responses.
Please feel free to contact me if there are any additional questions or concerns.
Sincerely,
'1'sen Vice President tl\\
SJL /Ills
-A SUBSIDIARY OF KERR-MCGEE CORPORATION
CIMARRON CARPORATION LET#R OF TRANSMITTAL TO:
M r. Ken Kalman, Project Manager Low Level Waste & Decommissioning Project Branch Division of Waste Management Office of Nuclear Material Safety and Safeguards U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 MAIL DROP T2F27 FROM:
Mickey Hodo, Quality Assurance Manager Cimarron Corporation P.O. Box 315 Crescent, OK 73028 El First Class Mail El Overnight--Fed Ex U Second Day--Fed Ex El Internal El UniShippers El Other El Overnight--UPS El Second Day Air--UPS These are transmitted as checked below:
El For Approval El Approved as submitted El As requested El Returned for corrections El Disapproved El For review and comment
- For your use El Return corrected prints El Controlled Copy REMARKS The above items are for your use. Please sign and return transmittal letter to me.
NOTE:
SIGNATURE ACKNOWLEDGEMENT OF RECEIPT PLEASE RETURN ONE SIGNED COPY TO SENDER I HAVE RECEIVED THE DOCUMENTS IDENTIFIED ABOVE AND THE PRIOR REVISIONS OF THESE HAVE BEEN
- DESTROYED NIA VOIDED N/A PRINTED NAME OF RECIPIENT:
- 4)
Z SIGNATURE OF RECIPIENT:
DATE RECEIVED:
C NY If enclosures are not noted, kindly notify Cimarron Corporation
Responses to Questions Raised by the U.S. NRC in Telephone Conversations with Cimarron Corporation Staff Questions Regarding the FSSR for Concrete Rubble in Sub-Area "F" (April 16, 1998)
Introduction Cimarron submitted the "Final Status Survey Report for Concrete Rubble in Sub-Area
'F"' to the NRC on March 10, 1998. NRC staff reviewed the Report and a telephone conference was held between Cimarron and NRC 'staff on April 16, 1998 to address questions pertaining to the Report. By letter dated May 20, 1998, the NRC sent Cimarron the seven questions concerning the Report, as well as questions pertaining to other submittals, and asked for a written response. The seven NRC comments concerning the Report are presented below with Cimarron's responses.
NRC Comment No. 1:
The last paragraph of page 11 states: "The random sample plan also contained those accessible areas known or suspected to have the highest gross beta-gamma surface contamination." How were the known or suspected sampling locations incorporated into the random sampling plan?
Cimarron Response:
Special efforts were not made to include known or suspected elevated areas in the random sample plan.
Cimarron had already completed the non-random survey of the supplemental grids (i.e., grids #1 through #29 and grids #31 through #35) prior to performance of the random survey.
Preliminary surveys indicated that the concrete rubble with the highest gross beta-gamma surface contamination were in the areas below the spillway and near Burial Area #1.
Based on this information, random samples were collected from those areas below the spillway and near Burial Area #1 in 5m x 5m grid areas that contained greater than or equal to 85% accessible concrete surface area. With this initial bias,, no other special efforts were incorporated to include specific elevated areas of rubble in the random sample. The statement in the report that the random sample plan includes locations "known or suspected to have the highest beta-gamma surface contamination" stems from the preliminary survey information available at the time that the random sample design was developed. Cimarron is confident that any similar random sample taken from the concrete would result in calculated total uranium concentrations that are similar or less than those indicated by the random sampling data presented in Appendix II, Table 3.
Responses to NRC Staff Questions on the FSSR for Concrete in Sub-Area "F" Page 1
Drawing No. 98FCONC-0 shows that supplemental non-random samples were collected from grids #1 through #29 and grids #31 through 35. The data from these supplemental samples are included, along with the random sample data, in Appendix II, Table 4.
Comparison of the data indicates that the supplemental grids contain lower total uranium
.concentrations.
This additional information provides some quantitative basis for our statement that the random sampling data represents, on average, a conservative upper bound for calculated total uranium activity.
NRC Comment No. 2:
Please present an explanation of the headings in Table 3 of Appendix II, and a discussion of the data used to generate the "Average Concentration" columns (i.e., whether "weighted average or "average" data were utilized).
Cimarron Response:
The following explanations are provided for the headings (from left to right) in Table 3 of Appendix II:
"GRID #": Designates the 5m x 5 meter grid as shown on Drawing No. 98CONC-0.
REPRESENTATIVE AREA NET READING (dpm/1OOcm 2)
"AVE":
Average gross beta-gamma reading (dpm/1OOcm 2) for the Im x Im representative area.
Instrument background has been subtracted, but not concrete background.
"MAX": Maximum gross beta-gamma reading (dpm/100cm 2) in the lm x 1m representative area. Instrument background has been subtracted, but not concrete background.
"% CONCRETE": Estimated percentage of the accessible concrete surface area within the 5m x 5m grid.
"TOTAL # OF HOT SPOTS": Number of Im x lm areas within the applicable 5m x 5m grid that contained elevated gross beta-gamma activity at or exceeding 5,000 dpm/1OOcm 2 (with instrument background subtracted).
HOT SPOT DATA (net reading)
"#": Hot Spot number (as recorded on Cimarron survey forms).
"AVE": Average gross beta-gamma reading (dpm/100cm') for the Im x Im area surrounding the hot spot. Instrument background has been subtracted, but not concrete background.
Responses to NRC Staff Questions on the Page 2 FSSR for Concrete in Sub-Area "F"
"MAX": Maximum gross beta-gamma reading (dpm/100cm2) within the lm x lm area surrounding the hot spot. Instrument background has been subtracted, but not concrete background.
HOT SPOT DATA (background subtracted)
"#": Hot Spot number (as recorded on Cimarron survey forms).
"AVE": Average gross beta-gamma reading (dpm/100cm2) for the lm x Im area surrounding the hot spot. Instrument background and concrete background has been subtracted.
"MAX": Maximum gross beta-gamma reading (dpm/100cm2) within the lm x lm area surrounding the hot spot. Instrument background and concrete background has been subtracted.
5m x 5m GRID (dpm!100cm2)
"AVE": Average gross beta gamma surface activity within each 5m x 5m grid. The calculation to determine the average was performed as follows:
Using Grid # 105 as an example:
- 1. Calculate the average hot spot activity (background subtracted) for the grid.
Example: 4,200 + 2,277 + 3,382 + 3,450 + 4,200 + 2,343 + 8,121 + 7,129 + 5,015 +
3,117 + 3,561 + 4,283 +/- 4,200 + 4,800 = 60,078.
60,078 + 14 = 4291.3 dpm/1OOcm 2
- 2. Calculate the background subtracted representative area activity for the grid.
Example: 1,129 - 800 = 329 dpm/1OOcm 2 Note: Concrete background = 800 dpm/1OOcm 2.
- 3. Calculate the area of the concrete within the grid by multiplying the "%
CONCRETE" by the grid area (25m 2).
Example: 25m 2 x 0.97 = 24.25m 2
- 4. Weight the averages by their respective areas and sum.
Example: 329 dpm/1OOcm 2 x (24.25 - 14) = 3,372 dpm/1OOcm 2 Responses to NRC Staff Questions on the FSSR for Concrete in Sub-Area "F" Page 3
4,291.3 dpm/lOOcm 2 x 14 = 60,078 dpm/100cm 2 3,372 + 60,078 = 63,450 dpm/1OOcm 2
- 5. Calculate the average gross beta-gamma surface activity within the grid by dividing by the total surface area of the concrete in the 5m x 5m grid.
Example: 63,450 dpm/1OOcm 2 + 24.25m2 = 2,617 dpm/100cm2 "MAX": Maximum gross beta-gamma surface activity within each 5m x 5m grid.
"WT. AVG.": This value is presented for informational purposes only and represents the "5m x 5m GRID, AVE" multiplied by the "% CONCRETE".
The "WT. AVG."
calculation was not utilized to determine average concentrations.
AVE. CONC (pCi/g)
"3"": Average concentration of total uranium in the concrete over a 3 inch depth. This calculation was determined as follows, using Grid #105 as an example:
Example: 2,617 dpm/1OOcm 2 + 350 dpm/1OOcm 2 per pCi/g total U = 7.5 pCi/g Note: the conversion factor for a 3 inch concrete depth is 350 dpmr/100cm2 per pCi/g total U. This conversion factor was calculated in the same manner as the conversion factor for 6 inch concrete depth, except that only 24, 1/8 inch layers were used in the calculations. The reader is directed to Section 8.6.2 of the Report (page 27) for additional explanation.
"6"": Average concentration of total uranium in the concrete over a 6 inch depth.
Example: 2,617 dpm/1OOcm 2 + 661 dpm/1OOcm 2 per pCi/g total U = 4.0 pCi/g Note: the conversion factor for a 6 inch concrete depth is 661 dpm/1OOcm 2 per pCi/g total U.
"Data Summary" Section Note:
This section contains data showing the beta-gamma surface activity (dpm/100cm2) and the total uranium concentration (pCi/g).
Responses to NRC Staff Questions on the FSSR for Concrete in Sub-Area "F" Page 4
Representative Areas (background subtracted)
"1 m2 Minimum": The lowest background subtracted gross beta-gamma activity and associated 6 inch average concentration for all representative areas in grids within the sample.
"Maximum":
The maximum background subtracted gross beta-gamma activity and associated 6 inch average concentration for all representative areas in grids within the sample.
"Overall Ave.": The average gross beta-gamma activity and associated 6 inch-average concentration for all representative areas in grids within the sample.
Hot Spots (background Subtracted)
"Total #": The total number of hot spots in the sample.
"Ave. #/grid": The average number of hot spots per grid area.
"1 m2 Ave. Min.": The lowest average gross beta-gamma surface activity and 6 inch average concentration calculated for any Im x Im hot spot.
"l m2 Ave. Max.": The maximum average gross beta-gamma surface activity and 6 inch average concentration found within any Im x Im hot spot.
"1 m2 Ave.":
The, average gross beta-gamma surface activity and 6 inch average concentration for all hot spots in the random sample.
Maximum pCi/g "3"": Maximum concentration of total uranium calculated for any 3 inch thick layer of concrete.
"6"": Maximum concentration of total uranium calculated for any 6 inch thick layer of concrete.
5m x 5m Grids (background subtracted)
"# of Grids": The total number of 5m x 5m grid areas in the sample.
"Area(m^2)": The total surface area of the concrete in the sample.
"Ave. Minimum":
The lowest gross beta-gamma surface activity and total uranium concentration calculated for any 5m x 5m grid area.
"Ave. Maximum": The maximum gross beta-gamma surface activity and total uranium concentration calculated for any 5m x 5m grid area.
Responses to NRC Staff Questions on the Page 5 FSSR for Concrete in Sub-Area "F"
"Overall Ave.":
The average gross beta-gamma surface activity and total uranium concentration calculated for all grids in the sample.
NRC Comment No. 3:
Is the 5,000 dpm/100cm2 "cut-off value" noted in the first paragraph of page 12 the proposed release criteria for the concrete? Please explain why this value was chosen.
Cimarron Response:
The release criterion which is appropriate for the concrete is the BTP Option #1 volumetric concentration limit for enriched uranium (i.e., 30 pCi/g average). The 5,000 dpm/1OOcm 2 gross beta surface activity criteria was used only as a "cut-off' value for documentation of elevated surface activity on field survey forms to denote areas for additional surveys. The 5,000 dpm/1OOcm 2 value was selected based upon health physics considerations due to the fact that it represents the upper limit for enriched uranium surface activity (average) that can be unconditionally released in accordance with the USNRC "'Guidelines for Decontamination of Facilities and Equipment Prior to Release for Unrestricted Use or Termination of License for By-Product, Source, or Special Nuclear Material." This "cut-off' value was considered to be reasonably conservative due to the fact that the NRC Guidelines apply to the release of buildings and equipment (averaged over lm2), and are not applicable as a release criteria for the concrete removed and placed in open land areas.
No averaging was performed by Cimarron prior to documentation of the areas exceeding 5,000 dpm/1OOcm 2, gross beta-gamma activity.
NRC Comment No. 4:
Why is the data in Appendix II, Table 3, "HOT SPOT DATA MAX" presented in some cases using 5 significant places, while in other cases, only 2 significant places are used?
For example, grid #11 has up to 5 significant places, while the data presented for grid #57 appears to have been rounded to two significant places.
Cimarron Response:
Cimarron used a conservative approach and rounded some of the survey data presented in the report upwards. When a fixed measurement was taken, at times the documented data was rounded upwards to reflect a conservative number.
For example, a maximum reading of 14,723 dpm/l00cm 2 can be recorded as 15,000 dpm/1OOcm 2. This practice of rounding upwards is commonly used throughout the nuclear industry.
NRC Comment No. 5:
How was the data in Appendix III developed and where did it originate?
Cimarron Response:
Cimarron staff used site construction drawings and staff knowledge of decommissioning history to estimate concrete volumes, The volume estimate includes all concrete rubble Responses to NRC Staff Questions on the FSSR for Concrete in Sub-Area "F" Page 6
removed from the Uranium Plant, and includes upward volume revisions that were made based upon "as-found" conditions during the decommissioning process. The volume estimate also includes all concrete rubble that was removed from the MOFF facility, even though much of this material left the facility as waste or was released for unconditional use. The volume estimate does not include any of the concrete that was placed into the drainage area by the State of Oklahoma during Highway #74 reconstruction.
NRC Comment No. 6:
There appears to be a typographical. error in the first paragraph, second.sentence of Section 8.6.3. Should the reference to Tables 5 and 6 be changed to Tables 3 and 4?
Cimarron Response:
This was a typographical error. The sentence is corrected to read as follows:
"These calculations, which are summarized in Appendix II (Tables 3 and 4), resulted in average total uranium concentrations (after background subtraction) ranging from -0.8 pCi/g to 7.4 pCi/g."
NRC Comment No. 7:
Please provide information and calculations to indicate the potential dose from inhalation of re-suspended materials from the concrete.
Cimarron Response:
Cimarron investigated available literature to determine appropriate resuspension factors for concrete and was unable to find specific citations.
When determining potential exposures due to building occupancy, the resuspension of airborne particulates from concrete surfaces is normally dealt with from the standpoint of non-fixed materials which are suspended due to mechanical or physical interactions such as scraping. In the case of the concrete rubble in the drainage areas, the residual activity is known to be fixed and mechanical scraping is not applicable. Therefore, resuspension of the concrete would be the result of environmental factors such as wind and water acting upon the concrete.
Since our review did not reveal any data relating to physical means of resuspension for our scenario, Cimarron investigated the deterioration of concrete and similar materials by weathering. The amount of material that is removed by weathering will include materials removed by the actions of water, wind, chemical interactions, pH, temperature, and other factors acting upon the surfaces. Much of the weathered materials will not be available for resuspension in the immediate area of the concrete due to the washing effects of rain that will carry the materials to other locations, as well as other factors such as particle sizes that are not easily suspended. Therefore, the use of the weathering estimate as an indicator of material that is resuspended is very conservative and should greatly overestimate the actual amount of resuspension that occurs.
Responses to NRC Staff Questions on the FSSR for Concrete in Sub-Area "F" Page 7
Seymour and Wonneberger' (Attachment 1) performed evaluations of building stone weathering and reported data for the natural weathering of granite, marble, limestone, and sandstone. Of the stones studied, limestone is most likely to share its characteristics with concrete, and would be expected to have similar or greater weathering characteristics.
Table 1 of Seymour and Wonnebergers' paper indicates that the mean lifetime of 1 mm (1/32 inch) of unweathered stone ranges from decades to hundreds of years 2. Seymour and Wonneberger also cite work performed by Winkler2 indicating that 10 mm (13/32 inch) of a limestone surface,has been, lost over-a 300 year period of natural-weathering; with about the same loss of a marble surface over a 150 year period.
For purposes of our analysis, we assumed that the concrete has a resuspension rate-that is equal to the weathering rate for marble (i.e., 10 mm is lost from the surface every 150 years). This weathering rate is the highest reported in the referenced document for any of the materials investigated'. This highest weathering rate will significantly overestimate the airborne concentrations of concrete particulates, since a significant portion of the weathering will occur as the result of forces that would not cause airborne particulates. In addition to assuming that all of the weathered material is resuspended, the analysis further assumes that all of the airborne material is respirable. Several other conservative factors have also been incorporated into the analysis as described later.
With the surface loss factors set, Cimarron evaluated two scenarios: a resident farmer (Scenario #1, and a Trespasser (Scenario #2). Scenario #1, the resident farmer scenario, assumes that reference man breathes airborne radioactive materials resuspended from the concrete. This scenario further assumed that the individual is in the plume centerline 25 percent of the time, and that the wind constantly blows toward the individual during the given time period.
Assumptions
- 1. The average concentration of total uranium in the uppermost 1/8 inch layer of concrete is 140 pCi/g.
This is equivalent to the average concentration previously calculated for the 6 inch layer of concrete rubble based upon the random sample results (i.e., 2.9 pCi/g) multiplied by a factor of 48 to account for the fact that all of the activity is being concentrated in the uppermost layer.
- 2. The concrete weathers at a rate equivalent to marble, or 10 mm in 150 years.
The weathering rate is assumed to be independent of time.
- 3. The estimated surface area of the concrete in Sub-Area "F" is 3,350 in 2, based upon 134 grid areas with 25 m2 of surface area.
- 4. All of the weathered material is respirable and becomes airborne.
- 5. The density of the concrete rubble is assumed to be 1.8 g/cm3.
- 6. The Stability Class is Class D, based upon given average weather conditions.
- 7. The average wind speed, u, is 5.6 m/s based upon Cimarron wind rose data from Oklahoma City WSFO Airport, Station ID 723530, 1945-1990 (Attachment 2).
- 8. The farmer is assumed to be in the plume centerline, directly downwind of the point source, with an occupancy of 25 percent.
Responses to NRC Staff Questions on the FSSR for Concrete in Sub-Area "F" Page 8
- 9. Farmer occupancy is at 100 m downwind from the point source in the plume centerline.
- 10. The emission is from a point source. This is more conservative than the actual conditions, which would be multiple point sources, thus resulting in additional plume dispersion.
- 11. Dose Conversion Factor (DCF) for total uranium
- DCF 238s DCF 235 P DCF234
= 3.58 E-05 Sv/Bq (Class Y). 3
- 12. The breathing rate is assumed at 9.6. m 3/day for the resident farmer and for the!
trespasser.
The volume of concrete that is removed by weathering from the surface of the rubble, each year, is estimated as:
3,350 m2 (10mmi150y) (m/1000mm) = 0.22 m3/y.
The total uranium source term activity that is assumed to become airborne each second, due to resuspension from weathering, is:
Q = 0.22 m3/y (1.8g/cm 3) (106 cm 3/m3) (140 pCi/g) (y/365d) (d/24h) (h/3600s)
= 1.8 pCi/s, or 1.8 E-12 Ci/s.
Scenario #1: Resident Farmer Dose Calculation The basic atmospheric dispersion equation for a ground level source at the plume centerline is:
X = Q +(27)(cy)(cT7)(u).
Sigma y and sigma z were picked from Figures 3-2 and 3-3 in Turner4 (Attachments 3 and 4), using Class D atmospheric stability curves.
The concentration of airborne total uranium, X, is calculated:
x = 1.8 E-12 Ci/s - (27t)(6m)(4.6m)(5.6m) = 1.9 E-15 Ci/m 3 The effective dose can be calculated using the dose conversion factors from EPA Federal Radiation Guidance Report No. 11'. The dose conversion factors for U-234, U-235, and U-238 are similar. Therefore, simplification of the problem can be achieved through the use of the dose conversion factor for U-234, which is the most conservative. Inhalation Responses to NRC Staff Questions on the FSSR for Concrete in Sub-Area "F" Page 9
Class Y is assumed for the resuspended material. The breathing rate is assumed to be 9.6 m 3/day.
Effective Dose to the Resident Farmer = (1.9 E-15 Ci/m3) (9.6 m3/d) (365 d/y) (0.25)
(3.58 E-05 Sv/Bq) (3.7 E9 mrem/ýtCi per Sv/Bq) (106 PCi/Ci)
= 0.2 mrem/y.
The upper estimate of dose to the resident farmer is 0.2 mrem/y, which is insignificant.
Scenario #2: Trespasser Dose Calculation The trespasser scenario assumes a shorter period of time is spent per year in the vicinity of the concrete. The trespasser, however, is closer to the point source emission. The trespasser is assumed to spend one 8-hour day per month (or 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> per year) directly downwind of the point source emission in the plume centerline. This has the effect of minimizing the atmospheric dispersion, which is represented by the denominator in the basic atmospheric dispersion equation given for the resident farmer scenario.
Under normal circumstances, the concentration of total uranium due to the resuspension of material from the concrete rubble will increase up to a certain distance from the source, followed by a decrease.
The resuspension forces (e.g., wind, etc.) will cause the respirable material to be carried from the surface of the concrete rubble to the breathing zone of the trespasser. This movement of residual activity requires that the individual be situated at a far enough distance from the source so that the resuspension forces can significantly affect the airborne concentrations in the individuals' breathing zone.
The model selected for this evaluation utilizes a single point source.
In reality, the concrete rubble can be thought of as an infinite number of point sources, each with its' own applicable atmospheric dispersion factors.
One can readily see that the dose estimates performed using the single point source model will result in extremely conservative estimates.
Estimates of a and cy, were obtained using the equations from Table 11.3.4 of "The Health Physics and Radiological Health Handbook"5. The power functions given in the table were used to provide estimates using neutral stability at distances of 10 to 100 meters from the assumed point source. The dose equations are identical to those given for the resident farmer. Attachment 5 provides a summary of the calculations for various point source to trespasser distances.
The single point source model estimated a maximum effective dose of 0.7 mrem per year at a distance of 10 meters from the Responses to NRC Staff Questions on the FSSR for Concrete in Sub-Area "F" Page 10
single point source, and a maximum effective dose of 0.02 mrem at a distance of 100 meters from the point source. The dose to the trespasser under this scenario is therefore negligible.
In summary, the potential for inhalation dose from the concrete rubble placed in Sub-Area "F" drainage areas is negligible.
References
- 1. Seymour, A. B., and Wonneberger, B., "Laboratory Evaluation of Building Stone Weathering," Journal of the American Society of Civil Engineers, 1977, pages85-104.
- 2. Winkler, E. M., "Important Agents of Weathering for Building and Monumental Stone," Engineering Geology I, 1966, pages 381-400.
- 3. Environmental Protection Agency, "Limiting Values of Radionuclide Intake and Air Concentration and Dose Conversion Factors for Inhalation, Submersion, and Ingestion," EPA-520/1-88-020, Federal Guidance Report No. 11, September, 1988.
- 4. Turner, D. B., "Workbook of Atmospheric Dispersion Estimates," U. S. Department of Health, Education, and Welfare, Cincinnati, OH, 1969.
- 5. Schlein, B. (Editor), "The Health Physics and Radiological Health Handbook,"
Scinta, Inc., 1992.
Responses to NRC Staff Questions on the FSSR for Concrete in Sub-Area "F" Page 11
04/22; e 398s E2: 01 2rn.20216 EECTNIC El T PAGE 02 ATTACHMENT 1 311
.3, Laboratory Evaluation of Building Stone Weathering Seymour A. Bortz' Bernhard Wonncberger 2 Dimension stone is among the most durable materiaLs, but the prcess of weathering has shown that some types of stone, even of the same variety, are more durable than others.At presenttherm is little information available about the durability of dimension stone on a building facade. Designers generally select a particular stone for its. asthetic qualities, with casual refereacc to basic parameter such as porosity, pore size, moistur absorption, and other critical physical and chemical pa'ameters.
Generally, when there is reference to weathering, the recommendation is to inspect another building with the same variety of stone. The recommendationdoes not consider the fact that stone, being a ncatal material, can vary considerably, evenfrom one plac=
in a quarry to another. Thus, in addition to observing weathering history in the field, we must determine how rock weathering can be recreated in the laboratory.
This paper attempts to provide background regarding the enviromento.
processes that cause stone weathering in the field, such as acid rain (chemical), thermal (temperaturechange)- and feezc-thaw of absorbed water. We compare laboratory to field dam that indicates accelerated durability testing can provide relabl informbatio to long-term behavior of dimension stone.
Introduction Naturl building stones are subj ecztedto a variety ofweathering conditions, both natural and man-made. Under these conditions, durability depends upon the stone's physical and chemical natrm.
Weathering of natural building stone consists of the reaction to environmental conditions vithin the body of the stone. It is the surf= of, lScnier Consultant, Wiss, Janney, Elstncr Associates., Inc., 330 Pfingsten Road.,
NorthbVrook, IL 60062-2095 2 Senior Architect, Wiss, Janncy, ELstner Associates., Inc., 330 Pfingsten Roacd, Northbrook, IL 60062-2095
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-20121680 PAG 03 86 DEGRADATION OF NATURAL BUILDING STONE the stone that is subjected to wafer and atmospheric gases. Weathering reactions are controlled by water and the natural gases dissolved in it (mainly O% and CO, and the human produced gases S07 and NO) that may penetrate the stone under various condition& Weathering rates are influenced by temperature, moisture, organic acids, and dissolved carbon dioxide. The average rainfall is a major controlling factor of the weathering rate. The rain presents the dynamic for attack of the structure of the stone.
This factor, in combination with the effects of our contemporary industrial society, accelerates natural weathering processes through elevated pollutant concentrations orX the stone surface. Acid pollutants, in both air and rainfall, are recognized as serious hazards to carbonaterocks, such as limestone and marble, that are used in construction of major buildings. Silicate rocks and granite are affected by these acid pollutants to a lesser degree. However, even silicate rocks may be seriously affected by some acids ard by 'alkal". Elevated temperati=, or rapid temperaturc cycles, not necessarily cyclic freezing, affect differential volume changes of mineral grains. Temperature will accelerate solution of the carbonate minerals, while frost will cause damage to both carbonate and silicate stones.
Damage from frost is due to expansion of the freezing water. The structure of stone contains connected pores that can trafisfer water through the stone unit. Water entering the structure of the stone is an important consideration in this process. Rain, high humidity, and condensationare important factors in this weathering procew. TIh water-filled pores exert forces against the pore walls by expanding water from ice crystallization during freezing. These pores may also contain clays, some ofwhich may expand when wet. The swelling of expansive clay minerals when wet or by osmotic forces due to differential concentrationsof dissolved material will put pressure against the pore walls. The outward forces of the expansion produce tensile stresses in the stone structure. Therefore, the tensile strength of the stone is of greater importance than the compressivestrengthwithregafdto freeze-thawdurability. For brittlematerial such as stone, the compressive strength is generally 10 to 15 times greater than the tensile strength-Variation of Dimension Stone Used for Building Facades This section will give some background regarding the natural weathering of granite, marble, limestone, and sandstone. It is important to understand the differing characteristics of the various types of stone that are available. These characteristics affect the behavior of the stone material under natural weathering conditions.
Limestone is a rock of sedimentary origin, composed principally of calcium carbonate (calcite) or the double carbonate of calcium and magnesium (dolomite).
Mlany limestones are formed of shells or altered shell fragments. Oolitic limestone, a popular building stone, consists of cemented rounded grains of calcite, generally less than 2 mm (5/64 in.) in diameter. Some limestones have varying amotmts of other material, such as quartz sand or clay. These materials arm mixed with the carbonate
042/19 2:01
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ELECTRONIC EI E PAGE 04 BUILDING STONE WEATHERING 87ii sare Minerals. The carbonate materials will dissolve when exposed to acidic water or to
- I d the water undersaturated with calcium.
rious.
.cids, Travertine is a varie-ty of limestone usually precpitatedfrom solution in ground.
if the "
waters and sutrface waters. When traertine occurs in bard, compact, extensive beds, tone.
it can be quarried and used as an attractive building stone. It is generally variegated
- iety, gray, white, or buff, with-inregularly-sbaped pores distributed throughout.
ious.Geologically, marble is a metamorphic rock formed by the recrystallization of
'tio11 the limestone or dolomite when sujected to high heat and pressure. Commercial s to" marble includes all crystalline.rocks composed predominantly of calcite and dolomite that can be polished to a reflective suface It also includesserpentinite, which i not arily.. "
a carbonate rock. Thus, in addition to geological marble, commercial marble includes willn many crystalline limestones, travertine and serpenfinite. In the metamorphic process, both original sedimentary features, such as fossils, are usually destroyed, and the bedding planes are replaced, by compositional layering (veins). The original calcite is reerystalized in an tlockng*osaic ex that provides the beamty a designer seeks re of *'
for interior or exterior 6nishes.
Sandstone is a consolidated cemented sana sedimentary rock deposit It has a distinctly granular textuxe with various cementing materials, including silica, iron oxides, and calcite. Enough voids generally remain in the rock to give it considerable may.j-permeability and porosity. (Commercially used sandstone is usually a sediment iotic consisting almost entirely of quartz grains, 1 to 2 mm (IM2 to 5/64 in.) in diameter with finst various types of cementing material.) This allows the stone to readily absorb and i the -*.
confine water where it can freeze in colder weather.
than Much1 Slate is a metamorphosed rock-derived from argillaceous (clay) sediments Ufse-l*
consisting of extremely fine-grained quartz, mica, and other platy minerals. Slate possesses an excellent parallel cleavage that allows the rock to be split into thin, s
smooth-surifaedslabs with relative ease. The color of slate is generally determined by the oxidation state of pyrite (iron) or the presence of graphite. The cleavage planes are relatively weak in tension parallel to the planes. Water can enter and travel along thmse g of ;
planes and late freeze in colder weather.
ring tics Commercial granite includes most rocks of igneous origin formed by solidification from molten rock beneath the earth's crust True granites consist of 1?
feldspars and quartz, with varying amounts of other minerals such as mica and um~
homblende. These minerals are in an interlocking and granular texture with locked-in ite). 7 stresses. Each variety of mineral behaves differently when subjected to the saeno e, a enviro'nmental conditions Le. differential thermal stresses.
less
04/22/1998 02401 E
ZCTRONIC El TED PAGE 85 88 DEGRADATION OF NAMhRAL BUILDJNG STONE Rgle pf Chsmical Weaathring Rainfall which enters the pores in the rock is a controlling hictor of the weathering raUte Material can be dissolved by. percolating water solutions or by the chemical decomposition of the stone. The amount of CO2 in the water causes the aggressiveness of the water that can dissolve the stone. Weatring reactions also depend on tempemature Higher temperatres increase tbermal agitatio.. Hence, such reactions are more magnified in the tropical areas than in colder temperatre zones. in desert areas, the stone is hot but not subject to the ints action of liquid water weathering, so chemical weathering dos not develop.
Table I shows the mean lifetime of 1 mm (1/32 iz.) ofuiweathered stote when it issubjected to environmental weathering. These results show that in a cold, timperate, or tropical humid climate, the average rainffll (i.e., water rising) probably controls the rate Qfweabaing.
Table 1. Mean liMetime of 1 mm (M'2 in.) of unweathered stone (1)
Stone Type climate Lifetime Acid tropical semi-arid 65 to 200 years (Light-colored igneous granite) tropical humid 20 to 70 years temperate humid 41 to 250 years cold humid 35 years Metamorp~c temperate humid 33 years (darble, slate, etc.)
Basic eperafte hurid 68 years*
(Dark-colored igneous granite) tropical humid 40 years Ultrabasic tropical humid 21.to 35 years Sedimentary arid-semiard 50 to 100 all others highly variable Rates of silicate wedatring are more difficult to evaluate because too many factors are involved which may influence the process. Stone exposed to pollted air may show signs of incipient wcathering by undesirable discoloring, loss of polish and hardness of feldspars and ferro-magnesium silicates. There are estimates that th= is t 2 to 2 V. times increase of the weatherifig rate by solubilizatijn and hydrolysis with each temperattre increase of 10°C (500F). The weathedug rate can increase nearly 20 to 40 times in tropical moist areasP
.1.
04e22/1998 qr 84/2/198 82 81 201216810 ELECTRONIC EI E PAG 85 02: 01 BUILDING STONE WEATHEMIG 89 or of the
)r by the
,uses the.
ons also ice, such mnes. Iii id waer t le when
,robably many~
tedaiMr sh and kmis Swithl2' ily2 0
.I There halve been observationsthat 10 mm (13/32 in.) of a limestone surface bta been lost aver a 300-year period of natral weather* g with about the same loss of a narble surface over a I 50-year period. Sandstone with feldspar and mica as impuriti*s will Iose about 2.5 mm (5/64 in.) over 200 years, while almost pure quartz sandstone will remain sbazp and clear over the same period.0.
_Temp
=ue Effcts on Weathering Weathering can also be caused by the difference of thenmal expansion of the minerals that constitute the various stones. Votumetric or linart expansion of the differemnmmnrmateria.l that compnise the some stone mass can cause mi-crcing of the stone when heated in direct sunlight. Terpemtures a~s high as. 2°C to 88°C (180OF to 190T) have been measured on dark stone surfaces All mierals expand with increasing temperature, however, they expand to dIfferent degrees.
Quartz expands about four times more than feldspars and twice as much as hombleade. Quartz is considered the-most critical mineral under conditions of heating of granites and quartzitic sandstunmes. When quar expands during heating, it exerts pressure against the surrounding crystals. These sosses can caume i c
in the granite, lowering the strngth and allowing Other weathering phenomena, both chemical and fivezing, to accelemte the disintegration processes. Figure 1 indicates the loss in compressive strength of granite who heated up to a tmperau= of 93 QC (2000P).
a Ccmpaem. frwlb, 5"10 Figure I. Loss in compressi-ve strength of granite when heated.0 Individual stone crystals will have diffbrent expansion properties for each axis orientation, as shown in Figure 2. Calcite exhibits linear thermal expansion parallel to the 0-axis of about 0.2 percent, but cogtracts about 0. percent perpendicular to the C-axis. The differingexpasiveratesof calcite*
umicrocracngin the strtur ofthe stone. This disruption is manifested s increased volume and absorption of the am duing headn and cooling phases plus loss in strength. Stone that is low in quartz and carbonate minerals wil expand v0ry le with icrases n temperatu.
'I I
II 1i
04/'22ý1998 02:01
.2012150 84/22/998 0281 28116*
ELECTRONIC El P~8 PAGE a7 90 DEGRADATlON OF NATURAL BUILDING STONE Another cause of stone disruption due to tcmpcntr changes is the diffieetial expausion of trapped salts in the pores of the stone. Trapped salt can result flora natural exposure due to high salt content in precipitation along coasW regions or from dissolved materials, (pollutants) in the environment. Figure 3 presents the thermal expansion of calcite, quartz, granite, and "rocxk" salt (halite). As the temperature inreases from O°C to 70-C(32 to 180°F), halite expands.(5 percent compared with 02 percent for granite and about 0.1 percent for calcite. Small as these differences may appear, it is believedthat expansion of absorbed salts combined with other factors can lead to stone decay.
C A
Figure 2. Calcite crystal.
w w
Figure 3. Thermal expansion of calcite, quart; ranite, and "rack" salt e)P
'04/22L 8
02.01
.2012160 ELECTRONIC El T*PAGE 08 BUILD[ING STONE WEATHERING 91 erential Effect of Freezing on Stone I natura
)r ftoal' Damage to stoneresults when temperatures axe belowfree2ingand any absorbed thermal water forms ice crystals. The expansive crystallization pressure is very important as it rature.:
produces tensile forces on the stone structure.
ed with t.;.
Z"es May.In addition to the expansion of the ice crystals, water itself expands just before rs, cat, it reaches a solid stat. The ice volumne is at a maximum and the density at a mi imn of 4°C (39°1F) (from 1,000 kglm3 (§2.4 lb/fIP) in an unfrozen state to 916 kgWm 3 (57.2 lb/ft) in a frozen state). However, the density of water also increases with increasing outward pressure when it is in a confined space. This increase in density is similar to that of 'inconfined ice, but somewhat greater.
Need for Laboratory Evaliation The introductory sections of this paperwere presented to provide a background for the design of a durability test procedure. This laboratory procedure has been used
.to develop information presented in the latter sections of this paper.
In the past, people have claimed that ston is "as hard as rock" and, therefore, durability testingis not necessary. IJowever, as we have already shown, differet types I.'*..
of stone will have varied behavioral characteriscs when subjected to natural weathering. The long-tern behavior can also be determined by using an accelerated test. The designer needs to know whether large blocks or thin slabs are to be used.
Structual considerations for large blocks are mainly compressive strengtb Because of the large mass of the stone units, mitior loses of thickness and property changes due to weathering have a negligible effect on the structural capabilities of massive stone.
However, structural considerations foz thin stone include panel size, flexural strength, and weatherability. Loss of strength and small chanjes in thickness can have a major effect on the long-term behavior of thin stone facades.
3.*
A good laboratory test must consider environmenMtal factors, such as temperatur, air pollution, and rain. In addition, the designer must consider not only wind loads, but the fact that the stone can vary from quarry to qumry, from one area within a single quarry to another, and possibly within a single quarry block Therefore, it is important to test the specific supply of stone for a large building project. Stone used successfully on a similar project in the past may not have the same physical or Smechanical properties for the current project.
Based on previously discussed en cmntal e:cts on the properties of stone, we have developed a procedure that considers the following environmentalfactors: acid rain, temperature change, and fireez-thaw cycling. The test procedure consists of placing a stone specimen with minimum dimensions of 32 mm (11/4 in.) thick, 102 mm P(4 in. ) wide and 381 mm (15 in.) long in a 4 pH sulfurous acid solution. nT specim=3
.1
84/22/19958 82:81
- 28.1215' ELECTRFNIC El PAG 89 92 DEGRADATION OF NATURAL BUILDING STONE are immersmd 6 mm (1/4 in.) to 10 mm (3/s in.) deep in the solution in a stainless steal pan. Each specimen is also set on 6 mm (tij in.) diameter rollers to ass= the stone face is subjected to the action of the bath solution. A fresh solution is used after each 25 cycle interval The speimens are then sbjected to 100 cycles between -23*C to
+770C (-100 to +170°F). Before the tc~t procedure is stared the test specimens are evaluated for dynamic Young's Modulus of Elasticity (sonic modulus) using ASTM Procedure C 215, "Test Method for Fnmdmental Transversce orhidinl and Torsional Frequenciesof Concrete Specime" Th1 sonic modulus testing is repeated after very 25 freeze-thaw cycles to provide a nondestructivemethod of monitoringthe changes in s-iength of the specimens. Figure 4 shows the relationship of sonic modulus to flexural strength developed from marble specimens. Thee is a good correlation at each neasured cycle bewee strength and *onic modulus.
nail Tak frot blo.
San
.~.
13 S.
1*-
11.
10-S S
U U
a S
U U
- 1 g
II
/v 9.
a1-S.
5, UWM NREMLW 4 VPW.
5pZ0 a
1 V
4-a-
2-0- ; 9 a ML a
- O~. w~aI Cam..
~
q am.~m~w utmam am a~ac
& u~~t
~
-~
~ua~
a ohm& OWL m
W "boo~m M I-.I r I
ION I
MODILL3 OF M~rnm 0"SI Figure4. Relatlonshpof sonic modulus to fiexmU strength deveoped from marble specimens.(')
Table 2 provides stone durability test data obtined using the test procedure decribed above at tbc Wi*. TauncyEltacrAssociatesInc. (WM) test loatory over a period often years. Rclts from gran1, marbl, ad limestone ae preseted Note how stone types of the same classification vary, including stnes of te same area and
'134/22/1998 02:01
,201216*
SELECTRRHIC El TEO PA*GE 10 BUI.DING STONE WEATHERING 93 less steel the Stone Lfter each"
-23°C to mens are.
g ASTM inal an4 repeated
=Drtgthe modulh.
slatlon at S...
S.,..*
S.%
.=.
4.'
-t
° name. Most of the stones indicate strength changes during the durability testing.
Table 3 shows how stones from differentblocks of the same quarry can vary. Material from one quarry block withstands the duration of the test while material from another block does not. These results show the need for testing several different blocks of the same quarry for use on a single building project.
Table 2. Summary of Durability Test Results of Varioua Dimension Stones I*rrXAL FLPCRCE m
fr FM2 AND EXURAL STnRM G WSB OF STONK-TSmhE MaNGCTH AFT TrSrING STIMN*TH I ____
_Man ku/ems fn 30 am:
]Pink Glranite (I116 in.)
94.6 wet 1ampc Fs rc IOWA Thczma (1,345)
Finish 115.3 88.6 23%
Unidc"ti "cd Graite (1,640)
(1h
).
115.3 109.1 5,%
(1,640)
(1,552)
(_
74.5twet 66.0 wet 11.4%
33 a=(1,060)3 Moon(1& am (I I n.)
80.5 dry 70.4 dry 12.6%
aThrnal (1,145)
(1,001)
Finish 74.5 wet 5"86 wet 21.3%
(1.060)
(834)
Stoney Creek Granite 30 mm o--
(13116 in.)
79.4 wet 44.6 wet 43.8%
(Pink Ganite *om Light Therzi (1,130)
(635)
Bramiforo CI)
Finish 81.1 wet 17.3%
Mount Airy Ganite 51 n=
(1,154)
C2 iL) 98.4 wet 8&O wea 173%
(Fiunc-galnd. white r
(1.400)
(1,223) dora=mesi grunite" 89.3 wet 9.0%
(1,270) 30 mm 69.4 dry 54.1 dry 1 21%
Venetian 102.8 dty.z.
100.7 dry.9").
2%
honed (1,462)
(1,433) 30 mm
.95A dry I 76.3 dry 1 20%
Baltic DBrwnGran (1316in.)
1122 (I,
9,0dy honed 112.2 dry.
98.9 Ma hoe
.4
-fi.59 f l.40" ocedure
- L over LNote I.
L
'a4/22/1998 02;1a4
.2012160 F7 CTRONIC ElTO PAGE 11 94 DEGRADATION QF NATURAL BULLDING STONE Table 2. Sumnmy of Durbility Test Results of Various Dimension Stones (continuccL.)
MIITIAL FLEXURAL PERCE1NT SAMI FLEXUNAL STRENGTH LOSS OF STONE TECIRESSj STRENGTH AFT TESTG S3RENGTH US8.4 dry I IL 16%
(1,257) 10S-2 dry I
- b. 84.4 dry I b.2-PS 30 mm (1,4901)
Rock'vl1 Beige Gmite (1/6 in.)
(.49dy) hmed (1,398 )
- a. 83.8 dry.L S. 15%
(1.399)(1,192)
- b. 76.6 dzy.
b.22%
_(1,089) 12&3 dry1 111.5 dy i 12%
0-=
(L600) 30mm 190.3 dry+/-
15.I dry.a.
30/
(I" Mi fzL )
(2,7o07 (7,619)
Cahlbd ramitc PolsMed 133.0 dxy 1 136.8 dry 1 3% pin Thermal (1,891)
(1.,46) 176.5 dy.L.
173.1 dry.L 2%
.(2,10)
(Z462) 112.0 dry 95.5 dry 15%
(14593)
(1,359) 51 Umm 79.0 dry j.
71.1 dry.
10%
(14(2 i%)
(,1)
(1.012) 69.7 dry, 54-3 dry 22%
___(992)
(773)
Chan o'L 3usm 51imm 149.1 dxy.i 125.8 d&yi.
16%
(2.)
(2,21)
(1,790) 68.8 dry.-
51.9 dry a.
25%
ValndctoL n
51
( (979)
(738)
(2i a.)
51.0 dry1 83.7 dry 1 3% smng 1(1,152)
(1.1"(
65.9 dry.
0 dryj.
100%
Lupt Limcou 51 min (938)
(2hz,)
5&. dryl.
0 y!
100%
Limd 31 mm s1.5 dr y.
0 dry/
100%
Ram!
L~mo ~
(2 Ciu.)
(1.159)_
109.0 dryi.
122.3 dry.-
13Aga* n Valde Buffl l
5mm (1,551)
(1,746)
(Z in-)
126.7 dry 1 10s.1 dzy 1 15%
147.2 dry.L 126.4, do"
- 14%*
Vald o"
Dv White 51 mm (2.094)
(1,17M)
LImesone (2 in.)
125.4 dry 1 100.2 dfy I 200 (1.,.7.3)
(1.426')
17.2 dry -L 161_S dtyx 9%
C2 in.)
14".6 dry 1 115.9 dryl1 22%
'a
'04/22/ V98 02: 01
'201216810 ELECTRONIC El TEX.
PAGE 12 BUILDING STONE WEATHERMNG 95 L NT OF QTH i.
<..w
- 1.
- 4'*
I'".
A Table 2. Summary of Durability Test Results of Various Dimension Stones (Connwued...)
INITAL IFLEXURAL n
NT FINISHAM F
STREGT" LOSS OF STONE L
WM lC S
STRMCMr
- MT:SM STREG-M 1563 120.9 23%
Dolomitic Lknww 32 xw (2223)
(1,719) flrom Fmce (1I /4 in.)
612 38.8 37*%
(80)
(552)
IndiaaLimeswna 64rim 65.6 59.3 9.K
_-____L_
C(2
% in.)
(933)
(843)
Vald= DWlomUi 30 mm 14L.0 153.3 4% gi L, estow (1I 36 in.)
(2,105)
(2180) 99.5 dry.i 6L.1 dry.L 24%
Pierre tie Lasme s
mm (1,7=)
(969)
.k (2 b-)
593 dr 1 45.5 dry 1 23%
(M43)
(647) 38.0 we 41%
(540)
Mika64.0
&a 41.4 w32 "m
Cairns. Italy an=ar 15 (1 114 i1.)
691.0 (5891.)wr 5
yeams of =crior ivW==
polished C911)
(589) 59.7 wet 7%
(849)
- a. 74.6 dryI a.6%
(1,G61) m 79.0 dry I
- b. 764 dry I
- b. 3Y9 MWO0hL 0.3 dry I L0*'
honed (1L4S
- 8. 96.6 dry _L
.'Y (1.3t4)
- b. 97.3 day..
- b. 7%
(1,394) 306m
- 0.5 *y1 54.1 &y1l 11%
M Gquis Gray Danby (I mm f,,)
(861)
(769)
Vamant Martble (ow 99.5 dry L 46.1 day.i 5%6 hoed(1,415)
(65!2 25mm 112.0 4
27%
Wl~ Camm~db* (I n.)
154.4 dlry (1,593)
Whito aMUmb(e (V in-)
(2,196) 90.6 dry 41%
hooed (W2M9 In in 1.
Tested prallel to the bedding plane or rift Tested perpendicular to the bedding plane or rift
e4/2n.~802:01.
201.228*
F1 ECTRONIC ElTE PAG 1.3 96 DEGRADATION OF NATURAL BUILDING STONE Table 3. Sunumnary of Durability Test Results for Limestone Removt4 from the Same Quatry Block A Tested Perpendicular to Bedding Plane Cycles 0
100 Change Dry 81.5 kg/cm2 Unable to test
-100%
Wt 43.2 kg/cm2 Unable to teat
-100%
Block B Tested Perpendicular to Bedding Plane
~l1, Dry 117.2 162.8 kg/cm2
-90/%
WetI12 t
147. kg:/cm I 5.
Figure 5 shows the change in sonic modulus that occmred when granimt was subjectedto the 4 pH sulfuhrus acid bath. Exposure to acid bath cycles apparmtly has little or no effect on the granite. However, the temperatur change does appear to cause differential expanston that breaks the bond between the mineral crystats and, by that, lowers the strength. Figure 6 is a similar curve for marble. The change in property is due to differential expansion and ntraction of the ididual calcite czystals,and some dissolving of the calcite. Although some calcite dissolves in the acid solution, this S ssentially neutralizes the acid. Figure 7 consists of curves for differet limestones.
The Massangi and Valdcrs dolomitic limestones show no basic effectwhile the Indiana Limestone has a slight downturn at the end of 100 cycles indicating dissolving of the calcite.
Accelerated Durability Data Rockvile Be*ge Granite 43 2
7 -1a
~
A i
M*
U 40 a
78 a
0 Figure 5. Accelerated durability test results for Rockville Bcige Granite.
l
"4/22*:Q8 82: al 28121680 ELECTROCHC El T PAG 14 BUILDING STItNE WEATHEMING.
97 Acc.lera$ted Durability Data Marquis Gray Dauby Marble
- -I-
-T r-" -I r-I" -I-7"
~
~~-I-
-* i T-r- 7
- .I I
I I
I I
I I
is~~~~i w'*
- 7o*
.*~~*
Sigure 6 Accelerated dumbility tes esults fr w:
Mwaqiis Gzay Danby Matble.
usanf Umestone (Rech) lie y
es of l
imestone x
=a~
4.0, he W
bilaaU~astlma
-~2.0 Ac"tletlW -d Wethedrng ofUnumbofnv Figure 7. Acceleratd durbi ity test results or td=
diffeent types of limestone.
The durabilitytest allows orie to make between stones. Hrowever, ther has beert criticism thatthic duraiblty test procedure has no IeldloTJ~p to natual weteing. Argurnents also state that the test has no mneaing W"%
bLdgrjetl%
are in warmer climates. To coupntemct these commot we have compae sonic modulus test results from stone subjected to na l weote=g to sonic modulu test results d.termind fm fore subjected to the durability tast prced
. For wamn climats, the test procedure can be modfiedto cycle betwen +SC and +77C-(+41 F and +170-f.
04/2 1/199 a 2
1 2 1 1 W L C R N C E TEOPAGE52:
1 98 DEGRADATION OF NATURAL BUILDING STONE Thirty-five years ago, twelve domestic marbles were placed on the roof of a building located immuediately south of the main business district in Chicago. The marbles wer monitored quarterly over 8 years using sonic modulus testing. Figure 8 is a chart showing the results of this work, including the results for.Danby marble, indicated as 'I" on the chart. Recently, we had an opportunity to perform dumrblity tests on a second set of Danby marble. The previously shown Figure 6 presents the change in sonic modulus determined during these tests. Figure 9 presents the natural weathering and durability test curves shown in Figs. 6 and 8. These curves show 100 freeze-thaw cycles of durability testing can be considered equivalent to 6 or 8 years of natural weathering. Therefore, 12 to 16 freeze-thaw cycles would be equivalent to one year of naftra weathering in a northern temperature envionmnt. Our data from this work and similar additional work using naturallyweathred stone from a building was compared with data obtained from durability testing of atic stock stone, (stone kept in reserve, but not e=posed to weathering). This work indicated that real-time effects could be estimated from labortoy tests.
Evaluationof a 10-year-oldmarble-cadhigh-rise offce building in Rochester, New York permittede-valuationof actual strengthdegadation from naturalweathering.
Many panels from the building fade, and panels that had not been exposed to natural weathering, were provided for durability tess. This provided a large statistical population for data analysis. The data is summarized in the chart previously shown in Figure 4. The chart shows a correlation between modulus of elasticity and flexural strength. A weathering chart was plotted using the modulus of elasticity and flexural strength daM, Figure 10.
In this figure, the flexural strength chart has -beea superimposed over the latic modulus chart.
The process of obtaining the mrves shown is empiricaL To provide guidance regarding the meaning of accelerated weatring, the data from weathered and unweathered stone had to be related in some manner. Data was plotted for lastic modulus vs. acclerated aging cycles for both the unweathered and weathered stone.
They were analyzed such that the original elastic modulus and stength for the building weathered stone are dose to being a tangent to the curve for elastic modulus and strength of attic stock subjected to the durability test This occurred at appm*n ately 160 cycles. Using these relationships, the conclusion was drawn that 160 cycles of acceleratedweathering appearto be equivalentto 10 years of naturalweatheing on the building. Thus, 16 cycles were determined to be equivalent to one year of service lf in.upper tawte New York. While this cannot be considereda 4igorous proof of the time relation ofnatural aging to accelera*ed aging, the empiricaldata from the laboratory and field observations indicate this is a reasonable approximation of what the designer can expect regarding changes in strength properties from natural weatherngm.
£.4
. 201216*
~4,'z/1gs882:~1 2a121~
ELECTRCNIC EI Teo 1
PAGE 16 BUILDING $TO&EWEAnIERING 99 of a The Mre8
- rble, ility
- the 100
's of one this was
)tin Octr 9ing N.
8 ii
~
V un.i Ural ural and
- Stic,
)ne.
ling and tely
- of the life icm and can
- 8.
~:TW.Oi jP EYJ RIVWARS Figure S. Chrt showing natural weathering test results for twelve different domestic marbles.
Estimated Life of Marquis Gray Danby Marble 2
4 1
14 1a 18 20 Trne in Yom Figure 9. Natural weatrng test results for Marqis Gray Danby Marble.
Using this temhique, two other marble-clad buildings were also studied. A corelation between elastic modulus and strength was also determind, Figure 11.
Composite curves for building weathered and attic stock were developed, Figs. 12 and
- 13. For the marble in Figure 12, 12 1/2 cycles of accelerated weadt=ern wexe found equivalent to one year of natural weathering on a building in Kansas City. For the marble in Figure 13,13 cycles of accelerated weathering wc msee to be equivaleat to one year of natural wpab*ering, The plot in Figure 13 is based on actual flex-ral I.
r4
.9.
I ~.
-i
.4 I.
I.
4.
I I.
'1
082:-1 -2812168@
MFCTRONIC EI TEX*
PAG 17 100 DEGRADATION OF NATURAL BUILDING STONE strength of the stone, not sonic modulus. Note the curves for sonic modulus arc similar to the curves for flexural strength.
The three marbles tested indicate approximately 15 cycles of accelerated weathering is equal to one year of natural weathering on the buildings All the data correlates with the rooftop test and laboratory accelerated weathering of the Danby marble previously discussed. The Danby data showed that changes in properties due to natural weathering and acceleratedweathering are similar. Curves from testing stone from the buildings and laboratory accelerated weathering can be tied together so as to predict. the number of cycles that will constitute one year of weathering.
Limited data has also been obtained for granie and limestone. The results of these tests have been similar to those obtained from.the more extensive marble data.
Figur6 14 presents a summary of all the data we have for granite, marble, and limestne In this figure, changes in properties of granite were plotted for 300 cycles. 500 cycl for marble and 200 cycles for limestone. Based on the data, aproximaty 13 cycles represent one year of natural weathering for granite, 12 % cycles repmsent one year for marble, and 12 cycles represent one year for limestone.
4r 2600 MaWM~l
~
crv 2"600 u*w nt CUJRVE USED ON AMM R
2 2400 A -M*IRALST'ENGM 12
/U 2
1000 1:-100 cv w7 A-a-l ogo.
4 400"
-GUROASI O
40 MODUI* usO 1Cr 4001 2030 10 20 30 KOVA.EHT TIM IN YFJIMC Figure 10. Relation of number of durability test cycles to years of natural weathering for Bianca White Carrara marble.
n-number of specimens.
O4!22/1998 02:01.
2012157~C~I lT A~1 ELECTRONIC EI To PAG 18 BUILDING M7NE WEATHERING 101 ilr Lted lata niby
. 11 dt 34 at
)n4 rl to
,V.
Al 45I J `
A IA a..,
0*
0*'
OA.
.4, U..,
0.1' a
f.
U._0 A
4 IL (109 ps G
Figure 11. Modubu of *asdtity (E) vs. flexural stength determined, from marble specimen&.
I 13 12.
1'I*
U.
0 a
0 W!N)SW uma 1.1 3
I 4Gb WAR wr GVei Figure 12. Number o4du bilte cycles v& moduus of lasdtiity (E) dctermined fom Georgia Golden Vein marble s.
We are cuzTrly cposing grnite, marble and limetone specimens to naftall weatluming on the roofaof a WIE budinginNarthbrook, l1inoisFiguz 1S. Figure 16 shows the sonic modulus curves detepwnedafier 1 years ofexposur The curves can be compamdwith the data platted in fig 5 tbxougb.7 for --- d.hng Note the snimlarity of the 'curs obtained during ealier accelezated weateriag and the naturally weathmtd stone. These twts will be etndad ove a tea-yer pe*iod.
a4/22/19913 2:01 28121sf ELECTRCNIC El T*
PAGE 19 102 DEGRADATION OF NATURAL BUDING STONE I
"Imo 1109.
10106 SOl fog
$000 20-0 CAmest=
a 0
Pan"S. rt~m WLV 1%
I ___________________________ I MMAMuT WOO" Of WAN OF MWoCWU 00
'S Figu= 3.
t Cs W. YUAM 0
'maumI*m Compaisou of duntbility test cy*es to yea=
of imtumi weethedog &etenincd from Whitm Cam ra mrble spccini~s.
14004 1200 1000 Sao FLEXURAL STRENGTH (peI)
GRANr'E
_ * -M-,BW I
too 400 200 n
a EQUIU.%LMT NUMBER OF YEARS OF EXPOSURE 40 Figr= 14.
xral strength vs. yc= of nat,.za ý,euftbii*
for marble, grnie, and Iimestmre I,
04122/'1998 02:01 "qqr ELECTRONIC El TD PAGE 20 "BUULDING STONE WEATHERING 103 4
1'7-4.
Figure 15. Stone test specinens =xpos'ed to natural weathering on roof.
Conclusions The efforts described in this paper include the results from several years of durability (accelerated eathring) testing. These tests were performed to dete=xiu the long-term durability of thin stone to natural weathering. The acceleratedwcathering test procedure described in this paper will distinguish between a durable and less durable stone under natural weathering conditions. The procedure will also provide an indication of strength loss due to weathering. This data can affect the structural design for long-term reliability of thin stone panels on high-rise buildings.
The data obtained showed useful information can be obtained from thin stone specimens less than 50 mm (2 in.) subjected to the described accelerated aging test for at least 100 cycles. If comparison tests can be made using naturally weathered stone and unweatheredstone, a relationship can be determined between number of cycles and time. The design can then be optimized by either increasing the thickness of the panel or reducing the unsupported span. These options will reduce load stresses and increase the service life of the stone.
8V2 2/1998 02:01 1
. 20121
- 84/221998 2:~2 281247 ECTRONIC EI PAT*2 PAGý:
21 104 DEGRADATION OF NATURAL BUILDING STONE Natural Weathering Study Tc3t Resulb t.I*Rel i
7.
Tmmrinkqinýj__
GAOMG4 Ca"
~Mazbl.2 Lmdmil__
-FmfT L3OG 6 AiG4ft J____
____________________I____
4.,
as5 1
rumburo(Ycau 2
2.5 3
V,.
4 Figure 16. Number of yeats of natmral weatering vs. modulus of elasticity (M) determincd from various stone specimens on roof.
The weahring curves provided can be used for design by dtermining where the allowable working stress crosses the strength loss curve for the stone. When data for naturally weathered stone is not available, an estimated cycle per year can be used fiom the data in this paper. -Assmue 12 to 15 freeze-thaw cycles of the durability test procedure is equivalent to one year of natural weathering in a temperate cimate.
We would like to acknowledge Mr. W'llam G. Hme Senior Consultant with Erfin, Miznc Associates, PEMA) and Mr. Ross A. MmmmInk Senior Petrographer with EHA, for their helpful review and c.mcnbts in the prepartion of this paper.
Nation, Daniel B. Intro&ution to the Petrology of Soils and Chemical Weathering. NewYo&c John WIley & Sons, In., 1991.
O-t1I-I-Sb L -
Ibid., page 6.
S iW'mklr, E.M. 'Import=tAgents of WeatheringforBuilding'and Monumental Stone," Engineering Geology, 1966, pages 381-400.
WiuAdir, E. M. Stone: Properties; Durability in Mm'Is Enviromnet. Second, revised edition, Wien, New York: Springer-Verlag, 1975.
(5 Ibid., page 125.
(6)
WJE in-house testing.
j
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AITFACtMEN' 2 FREQUENCY DISTRIBUTION SPEED Totai Mean Wind Speed 1.3 4-6 7-10 11-16 17-21
> 21 N
.2 1.3 2.9 3.5 1.6
.9 9.9 G.3 NNE
.1
.6 1.7 1.9
.5
.2 5,3 5.9 NE
.1
.8 1.6 1.1
.2 0
3.9 5.2 ENE
.1
.7 1.3
.6
.1 U
2.9 4.5 E
.2
.8 1.3
.6
.1 0
2.8 3.9 ESE
.1 1.0 15
.7
-1 0
3,5 4,3 SE
.2 1.8 3.5 2.1 A4
.1 8.6 4.8 SSE
.2 2.4 6.5 6.5 1.6
.5 18.1 5.7 S
t3 2.3 5.4 6"5 2.4 1.0 17.3 G,1 SSW
.2
.9 1.8 2.7 1.2
.6 7.7 6.6 SW
.2
.6 1.0 1.0
.3
.1 3.3 5.9 WSW
.1
.4
.5
.4
.1 1.8 5.0 W
1
.5
.4
.3
.1 0
1.4 4,1 WNW
.1
.6
.4
.1
.1 1.8 5,2 NW
.2
,8 1.1
.9
.5
.4 3.7 6,1 NNW 9
1.6 1-9 1.0
.6 6,5 6,6 VA 0
0 0
0 0
0 0
CLM 0
0 0
0 0
0 1.7 ALL 2.6 16.4 33.1 31.1 10.4 4.7 100
.O6 FREQUENCY OF CALMS.017 = 1.7%
ml L1 N3 0V 0
N CD C
z x
-- I
~0 m
z z
1>3 r-STATION ID:
723530 YEARS:
1945-1990 WIND ROSE-OKLAHOMA CITY WSFO AP. OK, US
0 9
S ATTACHMENT 3 I0,00(
1,000 b*" 100 Q
0.1 1
10 100 DISTANCE DOWNWIND, km Figure 3-2. Horizontal dispersion coefficient as a function of downwind distance from the source.
ATMOSPHERIC DISPERSION ESTIMATES
ATTACHMENT 4 1, 00 e
b 1.0 o-1 0.1 10 DISTANCE DOWNWIND, km Figure 3-3.
Vertical dispersion coefficient as a function of downwind distance from the source.
Estimates S3I-sOi 0 - 6a - 2 9
ATTACHMENT 5 Distancej sigma y I sigma z Q
I Chi I
Dose (meters)
(meters)
(meters)
(Ci/s)
(Ci/mA3)
(mrem/y) 10 20 30 40 50 60 70 80 90 100 0.50 0.94 1.37 1.79 2.19 2.59 2.99 3.38 3.77 4.15 0.75 1.22 1.62 1.98 2.32 2.64 2.94 3.22 3.50 3.77 1.8E-12 1.8E-12 1.8E-12 1.8E-12 1.8E-12 1.8E-12 1.8E-12 1.8E-12 1.8E-12 1.8E-12 1.36E-13 4.44E-14 2.30E-14 1.44E-14 1.01E-14 7.48E-15 5.83E-1 5 4.70E-1 5 3.88E-1 5 3.27E-1 5 0.656742 0.213661 0.110779 0.069512 0.048424 0.03604 0.028076 0.022615 0.018686 0.015754 Notes:
- 1) Sigma y = 0.06xA(O.92) per "The Health Physics and Radiological Health Handbook", page 440.
- 2) Sigma z = 0.15xA(0.70) per "The Health Physics and Radiological Health Handbook", page 440. *<
- 3) Dose = Trespasser dose per year, assumes trespasser spends 12 8-hour days per year in the plume centerline.
- 4) Q is assumed to be a point source.
- 5) Distance is downwind from the point souce in plume centerline.