ML12153A332

1500 - E117 - Concrete Technology and Codes - 04 - Aggregate Geology and Classification

ML12153A332
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Issue date:	06/01/2012
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Concrette Tech C hnolog gy and Codes s

Aggregate Geology and Classification

Aggregate Geology and Classification Brief concrete overview Aggregate mineralogy and geology Aggregate production Physical properties of aggregates

Cement Water Air Fine Aggregate 60 - 75% off volume l

is stone & sand Coarse Aggregate

ACI 221R Guide for Use of Normal Weight and Heavyweight Aggregates in Concrete Aggregates, the major constituent of concrete, influence the properties and performance of both freshly mixed and hardened concrete. In addition to serving as an inexpensive filler, they impart certain positive benefits b f that h are d described b d in this h guide. d When they perform below expectation, unsatisfactory concrete mayy result. Their important p role is ffrequently q y over-looked because of their relatively low cost as compared to that of cementitious materials.

Aggregate in Concrete Coarse Aggregate (stone or gravel)

> 5 mm (0.2 in.)

Largest particles may range from 0.5 mm ( in.) to 37.5 mm (11/2 in.) or more Fine Aggregate (sand)

< 5 mm (0.2 in.)

Influence of Aggregate on Fresh h Concrete Properties Aggregate Property Concrete Property Particle size distribution Workability (grading) Water demand Particle shape Paste content Particle texture Presence of fine material (silt & clay)

Organic impurities Setting behavior

Influence of Aggregate on Hardened Concrete Properties Aggregate Property Concrete Property Size and shape Mechanical behaviour Strength Strength Stiffness Modulus of elasticity Organic Shrinkage impurities Coefficient of thermal expansion Coefficient of thermal expansion Thermal conductivity Thermal conductivity Specific heat Specific heat Thermal diffusivity Thermal diffusivity

Influence of Aggregate on Hardened Concrete Properties Aggregate Property Concrete Property Soundness Resistance to freezing and thawing Frost resistance Particle size Presence of alkali-reactive Resistance to alkali-aggregate minerals reaction Density Abrasion resistance Porosity Frictional properties (pavements)

Volume l stability bl Aesthetics h

Mineral composition Economics

Aggregate Geology Aggregate Geology Mineral-Mi l solid lid crystalline t lli substance, bt formed by natural, and usually inorganic, processes Homogeneous physical properties Distinctive chemical composition Distinct crystal structure Rock-Rock - natural assemblage of one or more minerals

Mineral Classification C t ll Crystallographyh Physical properties Crystal habit Density Cleavage Optical properties Hardness Electrical properties Color Magnetic properties Chemical composition

Mineral Classification by Chemical Composition Systematic Mineralogy Nitrates Phosphates Native Organic Halides Carbonates Arsenates elements Substances Borates Vanadates Sulfates Oxides Chromates Sulfides Silicates Hydroxides Tungstates Molybdates

Mineral Classification by Chemical Composition Systematic Mineralogy Nitrates Phosphates Native Organic Halides Carbonates Arsenates elements Substances Borates Vanadates Sulfates Oxides Chromates Sulfides Silicates Hydroxides Tungstates Molybdates

Rock Classification R k classified Rocks l ifi d b by mode d off fformation ti Igneous Sedimentary Metamorphic

Igneous Rocks FFormed dbby solidification lidifi ti andd crystallization t lli ti off cooling magma (intrusive) or lava (extrusive)

Igneous Rocks I t i iigneous rocks Intrusive k form slowly have h a coarse-grained i d ttexture t

Extrusive igneous rocks solidify l d f more rapidly dl have a fine-grained texture

Igneous Rocks Intrusive Extrusive Major Minerals Minor Minerals Quartz, K-feldspar, Na- Muscovite, biotite, Granite Rhyolite p

feldspar amphibole p

K-feldspar, Quartz, muscovite, Syenite Trachyte Na-feldspar biotite, amphibole Quartz, Q t Na-feldspar, N f ld K-feldspar, K f ld C Ca-Granodiorite Dacite amphibole feldspar, biotite Na-feldspar, Ca-Diorite Andesite Pyroxene, y , biotite f ld feldspar, amphibole hib l Gabbro/ Ca-feldspar, pyroxene, Na-feldspar, Basalt Diabase olivine amphibole

Sedimentary Rocks D t it l sedimentary Detrital di t rocks k

Chemical sedimentary rocks

Sedimentary Rocks D t it l sedimentary Detrital di t rocks k

Formed by deposition and lithification of rockk andd mineral i l ffragmentst Deposition results from weathering and t

transport t off existing i ti rocks k Lithification occurs through compaction and/or d/ cementationt ti Classified mainly by particle size

Sedimentary Rocks Particle l Name Size (mm)

( )

Boulder > 256 Cobbles64-256 Pebble 4-64 Granule 2-4 Sand 0.062-2 Silt 0.004-0.062 Clay < 0.004

Sedimentary Rocks Sediment Particle Name Size (mm) Detrital Rock Name Boulder > 256 Conglomerate Cobbles64-256 (rounded particles)

Gravel Pebble 4-64 Breccia

(

(angular l particles) i l )

Granule 2-4 Sand 0.062-2 Sand Sandstone Silt 0.004-0.062 Siltstone Claystone Mud Mudstone Clay <00.004 004 g Argillite Shale

Sedimentary Rocks Sandstones classified by:

Particle sorting Particle P ti l shape h

Particle mineralogy Cementing materiall calcite silica iron oxide

Sedimentary Rocks D t it l sedimentary Detrital di t rocks k

Chemical sedimentary rocks Inorganic Organic

Sedimentary Rocks Chemical sedimentary rocks Inorganic Precipitation of dissolved material from solution (calm lakes and seas) limestone- travertine, oolitic limestone dolostone chert rock salt (halite) rock gypsum

Sedimentary Rocks Chemical sedimentary rocks Organic Biochemical Biochemical sediment sediment formed by skeletons of marine organisms coquina chalk coral reefs chert Coal peat anthracite

Metamorphic Rocks FFormeddb by ttransformation f ti off preexisting i ti rocks exposed to immense heat and/or pressure Original rock undergoes mineralogical and textural changes Granite Gneiss

Rock Classification Rocks Igneous Sedimentary Metamorphic Intrusive Extrusive Detrital Chemical Inorganic Organic

The Rock Cycle Magma Cooling and solidification Melting (Crystallization)

Metamorphic Heat and pressure Igneous R k Rock Rock Weathering, ttransportation, t ti Heat and pressure and deposition (Metamorphism)

Sedimentary Weathering, transportation, deposition Sediment Rock Cementation and compaction (Lithification)

Rocks Rocks for Use in Concrete ASTM C294 C294: StStandard d dD Descriptive i ti Nomenclature for Constituents of Concrete Aggregates Common, naturally occurring rock types granite, diorite granite diorite, gabbro limestone fine-grained volcanic rocks chert basalt (traprock) marble conglomerate, l sandstone, d (

(meta)quartzite

)

(ortho)quartzite, arkose gneiss graywacke slate, phyllite, schist siltstone, claystone, shale

Rocks Rocks for Use in Concrete ASTM C295:

C295 Standard St d d G Guide id ffor Petrographic Examination of Aggregates for Concrete X-ray diffraction X

X-ray fl fluorescence

Potentially Deleterious Constituents Chalcedonic Ch l d i chert h t (ASR)

Argillaceous dolomitic limestone (ACR)

Aggregate Production Aggregate Production N t l sand Natural d and d gravell Crushed rock

Aggregate Production N t l sand Natural d and d gravell usually dug or dredged from pits, rivers, lakes or seabeds often require minimal processing tend to be smooth and rounded

Aggregate Production C h d rockk Crushed typically produced by crushing quarried rock or cobbles and boulders tend to be sharp and angular

Aggregate Production Crushed Rock Initial processing to obtain suitable grading, uniformity and cleanliness

1. Crushing 2 Screening 2.

3. Washing Aggregate A t beneficiation

Aggregate Production Crushed Rock

1. Crushing

Aggregate Production Crushed Rock

1. Crushing

Aggregate Production Crushed Rock

1. Crushing

Aggregate Production Crushed Rock

2. Screening- Vibrating screens

Aggregate Production Crushed Rock

2. Screening- Cylindrical revolving screens

Aggregate Production Crushed Rock

3. Washing

Aggregate Production Crushed Rock Aggregate beneficiation applying l i processingi methods h d to upgrade d

the quality of the aggregates typically involves removal of undesirable or deleterious particles

Aggregate Production Crushed Rock Aggregate beneficiation Treatment Objective Crushing Remove friable particles Heavy media separation Remove lightweight particles Reverse air or water flow Remove lightweight particles Hydraulic jigging Remove lightweight particles Elastic fractionation (bounce) Remove lightweight and soft particles Washing and scrubbing Remove coating and fines Blending Control deleterious components Screening Control gradation

Aggregate Production Crushed Rock Aggregate beneficiation

Aggregate Storage and Handlingg Build stockpiles in thin layers of uniform thickness

Aggregate Storage and Handlingg Retrieve samples from edges of pile, bottom to top

Aggregate Storage and Handlingg Stockpiling separate size fractions can minimize segregation of coarse aggregates

Aggregate Storage and Handlingg Damp sand segregates less than dry sand

Aggregate Storage and Handlingg Crushed aggregate segregates less than rounded aggregate

Aggregate Storage and Handlingg Bulkheads or dividers minimize cross-contamination of stockpiles

Aggregate Physical Properties

Aggregate Physical Properties p

Particle shape and surface texture Bulk density and relative density Absorption and surface moisture Shrinkageg Strength and hardness Thermal properties Grading Resistance to freezing and thawing Volume stability Abrasion and skid resistance Resistance to corrosive substances

Particle Shape Cl ifi i Classifications Rounded Irregular Angular g

Flat Elongated Flat and elongated

Particle Shape Particle Shape Discoidal Sub-Sub Spherical Sub-Sub Prismoidal discoidal prismoidal FLAT ELONGATED

Particle Shape Fl and Flat d elongated l d particles i l Significantly affect workability and pumpability May trap bleedwater and contribute to mortar flaking Limited to less than 15% of total aggregate mass

Surface Texture Cl ifi i Classifications Glassy Smooth Granular Rough Crystalline Honeycomb

Surface Texture Smooth Surface

Surface Texture Rough Surface

Particle Shape & Surface Texture Can significantly affect fresh concrete properties R

Rough, h angular l particles:

ti l Have more interparticle interaction and greater resistance to movement Require more lubrication (paste & water)

Have larger surface-to-volume ratio R

Requires i more paste t tto coatt aggregate t

Generally achieve improved bond with cement paste Generally provide greater flexural strength

Particle Shape & Surface Texture ASTM D4791: Standard Test Method for Flat Particles Elongated Particles Particles, Particles, or Flat and Elongated Particles in Coarse Aggregate

Particle Shape & Surface Texture ASTM C1252: Standard Test Method for Uncompacted Void Content of Fine Aggregate (as Influenced by P ti l Sh Particle Shape, SSurface f

Texture, and Grading)

Bulk Density Al called Also ll d unit it weight i ht Mass or weight of aggregate t per unit it volume l

Volume occupied by both aggregate particles ti l and d voids id b between t particles ti l Void content:

30 to 45% for coarse aggregate 40 to 50% for fine aggregate

Bulk Density A

Angularity l it iincreases voidid content t t Large top size, even gradation decreases voids, id iincreases b bulk lk d density it Normal-weight: 1200 to 1700 kg/m3 (75 tto 110 lb/ft3)

ASTM C29: Standard Test Method for Bulk D it (U Density (Unit it W Weight) i ht) anddVVoids id iin Aggregate

Bulk Density Relative Density Al called Also ll d specific ifi gravity it Ratio of mass of aggregate to equal volume off water t

Used in absolute volume method of mix d i design Normal-weight: 2.4 to 2.9

Relative Density (Mass Density)

Mass density is product of specific gravity and densityy of water Densityagg = S.G. x DensityH2O Densityagg = 2.5 x 1000 kg m3 = 2500 kg m3 = 156 lb ft 3 Normal-weight: 2400 to 2900 kg/m3 (150 to 181 lb/ft3)

Mass density does not account for volume of voids between particles

Relative Density ASTM C127:

C127 Standard St d d TTestt MMethod th d ffor Density, Relative Density (Specific Gravity),

and Absorption of Coarse Aggregate ASTM C128: Standard Test Method for Density Relative Density (Specific Gravity)

Density, Gravity),

and Absorption of Fine Aggregate

Absorption and Surface Moisture Oven dry Saturated surface Aggregate gg g contains dry (SSD) no moisture (pores Aggregate is saturated are empty) (pores are filled), but Fully absorbent there is no free water on the th surface f

At equilibrium Air dry Damp or wet Aggregate contains Aggregate is saturated some moisture, but is (pores are filled), and nott saturated t t d (pores

( th there iis an excess off are partially filled) water on the surface Somewhat absorbent Contributing free water

Absorption and Surface Moisture Moisture conditions Mix water ASTM C127 and C128 Absorption mass % of water to reach SSD Coarse aggregate: 0.2 to 4%

Fine aggregate: 0.2 to 2%

Free water content of moist aggregates Coarse aggregate: 0.5 to 2%

Fine aggregate: 2 to 6%

Absorption and Surface Moisture Bulking Increase in total volume of fine aggregate when moist compared d to same mass when dry Stockpile Stockpile Stockpile dry partially saturated saturated

Absorption and Surface Moisture Bulking Can cause batching errors Effect more prominent with fi finer gradations d i

Shrinkage- Aggregates Often related to absorption characteristics High absorption high shrinkage Low shrinkage aggregates Quartz Limestone Feldspar Dolomite Granite High shrinkage aggregates Sandstone Shale Slate Graywacke Hornblende

Shrinkage- Concrete Shrinkage- Concrete I fl Influenced dbby many aggregate t characteristics h t i ti Stiffness, compressibility, modulus of elasticity G di particle Grading, ti l shape, h aggregate t ttop size i

Paste-aggregate bond (texture, porosity)

Presence of clay on or within aggregate

Aggregate Strength Compressive:

C i 65 tto 270 Mpa M (10,000 (10 000 to t

40,000 psi)

T il 2 tto 15 M Tensile: Mpa (300 tto 2 2,300 300 psi) i)

Does not usually influence normal-strength concrete t

Rarely tested directly Paste hardness and paste-aggregate bond more critical

Aggregate Hardness Mohs scale for minerals Relative Scale Mineral Common Object Hardest 10 Diamond 9 Corundum 8 Topaz 7 Quartz 6 Potassium feldspar Glass, pocket knife (5.5) 5 Apatite 4 Fluorite 3 Calcite Copper penny (3) 2 Gypsum Fingernail (2.5)

Softest 1 Talc

Aggregate Hardness H d tto quantify Hard tif ffor rocks k

Varies with rock type Soft and friable particles Prone to crumbling Increase fines content ASTM C33 limits mass %

Will affect abrasion resistance

Aggregate Thermal Properties p

Coefficient of thermal expansion (CTE)

~1 1 to 16 x1010-66/°C ((~2 10-66/°F) 2 to 29 x10 /° )

CTE of paste and aggregate vary greatly St Stronglyl iinfluences fl CTE off concretet Conductivity Diffusivity Properties depend somewhat on aggregate mineralogy

Aggregate and Fire Resistance Manufactured and lightweight aggregates have better insulating properties provide greater fire resistance Quartz expands 0.85%

at ~570°C 570 C (1060°F)

(1060 F) concrete with calcareous coarse aggregate often exhibits less damage after fire than concrete with siliceous aggregate

Summary Aggregates A t comprisei 60 tot 75% off concrete t

volume Aggregates A t influence i fl ffresh h and dhhardened d d concrete properties

Summary Rocks R k are naturally t ll occurring i assemblages bl of one or more minerals R k grouped Rocks d by b mode d off fformation ti Igneous Sedimentary S di t Metamorphic

Summary Aggregates A t mostt often ft natural t l sand d and d

gravel, or crushed rock Aggregate A t is i often ft processed d tto achieve hi desired quality, uniformity, and gradation

Summary Ph i l properties Physical ti off aggregatet iinclude:

l d Particle shape and surface texture Bulk B lk d density it andd relative l ti d density it Absorption and surface moisture Shrinkage Strength and hardness Thermal properties

Summary Physical Ph i l properties ti off aggregate t may influence mix design process and overall properties of concrete