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Aggregates for Concrete. Fine Aggregate n Sand and/or crushed stone n < 5 mm (0.2 in.) n F.A. content usually 35% to 45% by mass or volume of total aggregate.

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Presentation on theme: "Aggregates for Concrete. Fine Aggregate n Sand and/or crushed stone n < 5 mm (0.2 in.) n F.A. content usually 35% to 45% by mass or volume of total aggregate."— Presentation transcript:

1 Aggregates for Concrete

2 Fine Aggregate n Sand and/or crushed stone n < 5 mm (0.2 in.) n F.A. content usually 35% to 45% by mass or volume of total aggregate

3 Aggregates for Concrete Coarse Aggregate n Gravel and crushed stone n  5 mm (0.2 in.) n typically between 9.5 and 37.5 mm (3/8 and 1½ in.)

4 Aggregates for Concrete Rock and Mineral Constituents in Aggregates 1.Minerals 2.Igneous rocks 3.Metamorphic rocks 4.Sedimentary rocks

5 Aggregates for Concrete Rock and Mineral Constituents in Aggregates n Silica u Quartz, Opal n Silicates u Feldspar, Clay n Carbonate u Calcite, Dolomite 1. Minerals

6 Aggregates for Concrete Rock and Mineral Constituents in Aggregates n Sulfate u Gypsum, Anhydrite n Iron sulfide u Pyrite, Marcasite n Iron oxide u Magnetite, Hematite 1. Minerals

7 Aggregates for Concrete Rock and Mineral Constituents in Aggregates n Granite n Syenite n Diorite n Gabbro n Peridotite n Pegmatite n Volcanic glass n Felsite n Basalt 2. Igneous rocks

8 Aggregates for Concrete Rock and Mineral Constituents in Aggregates n Conglomerate n Sandstone n Claystone, siltstone, argillite, and shale n Carbonates n Chert 3. Sedimentary rocks

9 Aggregates for Concrete Rock and Mineral Constituents in Aggregates n Marble n Metaquartzite n Slate n Phyllite n Schist 4. Metamorphic rocks n Amphibolite n Hornfels n Gneiss n Serpentinite

10 Aggregates for Concrete Normal-Weight Aggregate Most common aggregates n Sand n Gravel n Crushed stone ASTM C 33 Produce normal-weight concrete 2200 to 2400 kg/m 3 (140 to 150 lb/ft 3 )

11 Aggregates for Concrete Lightweight Aggregate (1) Expanded u Shale u Clay u Slate u Slag ASTM C 330 Produce structural lightweight concrete 1350 to 1850 kg/m 3 (90 to 120 lb/ft 3 )

12 Aggregates for Concrete Lightweight Aggregate (2)  Pumice  Scoria  Perlite  Vermiculite  Diatomite Produce lightweight insulating concrete— 250 to 1450 kg/m 3 (15 to 90 lb/ft 3 )

13 Aggregates for Concrete Heavyweight Aggregate n Barite n Limonite n Magnetite n Ilmenite n Hematite n Iron n Steel punchings or shot ASTM C 637, C 638 (Radiation Shielding) Produce high-density concrete up to 6400 kg/m 3 (400 lb/ft 3 )

14 Aggregates for Concrete Aggregate Characteristics and Tests (1) CharacteristicTest Abrasion resistance ASTM C 131 (AASHTO T 96), ASTM C 535, ASTM C 779 Freeze-thaw resistance ASTM C 666 (AASHTO T 161), ASTM C 682, AASHTO T 103 Sulfate resistanceASTM C 88 (AASHTO T 104) Particle shape and surface texture ASTM C 295, ASTM D 3398 Grading ASTM C 117 (AASHTO T 11), ASTM C 136 (AASHTO T 27) Fine aggregate degradation ASTM C 1137 Void contentASTM C 1252 (AASHTO T 304) Bulk density ASTM C 29 (AASHTO T 19)

15 Aggregates for Concrete Aggregate Characteristics and Tests (2) CharacteristicTest Relative density ASTM C 127 (AASHTO T 85)—fine aggregate ASTM C 128 (AASHTO T 84)—coarse aggregate Absorption and surface moisture ASTM C 70, ASTM C 127 (AASHTO T 85), ASTM C 128 (AASHTO T 84), ASTM C 566 (AASHTO T 255) Strength ASTM C 39 (AASHTO T 22), ASTM C 78 (AASHTO T 97) Def. of constituents ASTM C 125, ASTM C 294 Aggregate constituents ASTM C 40 (AASHTO T 21), ASTM C 87 (AASHTO T 71), ASTM C 117 (AASHTO T 11), ASTM C 123 (AASHTO T 113), ASTM C 142 (AASHTO T 112), ASTM C 295 Alkali Resistance ASTM C 227, ASTM C 289, ASTM C 295, ASTM C 342, ASTM C 586, ASTM C 1260 (AASHTO T 303), ASTM C 1293

16 Aggregates for Concrete Grading of Aggregate ―Grading is the particle-size distribution of an aggregate as determined by a sieve analysis using wire mesh sieves with square openings. ASTM C 33 Fine aggregate―7 standard sieves with openings from 150 μm to 9.5 mm (No. 100 to 3/8 in.) Coarse aggregate―13 sieves with openings from 1.18 mm to 100 mm (0.046 in. to 4 in.)

17 Aggregates for Concrete Range of Particle Sizes

18 Aggregates for Concrete Fine-Aggregate Grading Limits Sieve sizePercent passing by mass 9.5 mm(3/8 in.) mm(No. 4)95 to mm(No. 8)80 to mm(No. 16)50 to µm(No. 30)25 to µm(No. 50)5 to 30(AASHTO 10 to 30) 150 µm(No. 100)0 to 10(AASHTO 2 to 10)

19 Aggregates for Concrete Maximum Size vs. Nominal Maximum Size of Aggregate n Maximum size ― is the smallest sieve that all of a particular aggregate must pass through. n Nominal maximum size ― is the standard sieve opening immediately smaller than the smallest through which all of the aggregate must pass. n The nominal maximum-size sieve may retain 5% to 15%

20 Aggregates for Concrete Nominal Maximum Size of Aggregate  1/5 then narrowest dimension between sides of forms  3/4 clear spacing between rebars and between rebars and the form  1/3 depth of slabs Size should not exceed ―

21 Aggregates for Concrete Coarse Aggregate Grading Sieve size Percent passing by mass 37.5 mm(1½ in.) mm(1 in.)95 to mm(½ in.)25 to mm(No. 4)0 to mm(No. 8)0 to 5 Size No to 4.75 mm [1 in. to No. 4]

22 Aggregates for Concrete Grading Limits

23 Aggregates for Concrete Reduction of Voids

24 Aggregates for Concrete Dispersion of Aggregates

25 Aggregates for Concrete Fineness Modulus (FM) n Obtained by adding the sum of the cumulative percentages by mass of a sample aggregate retained on each of a specified series of sieves and dividing the sum by 100. n The specified sieves are: 150 µm (No. 100), 300 µm (No. 50), 600 µm (No. 30), 1.18 mm (No. 16), 2.36 mm (No. 8), 4.75 mm (No. 4), 9.5 mm (3/8 in.), 19.0 mm (3/4 in.), 37.5 mm (1½ in.), 75 mm (3 in.), and 150 mm (6 in.).

26 Aggregates for Concrete Sieve Analysis and FM of Sand Sieve size Percentage of individual fraction retained, by mass Percentage passing, by mass Cumulative percentage re- tained, by mass 9.5 mm(3/8 in.) mm(No. 4) mm(No. 8) mm(No. 16) µm(No. 30) µm(No. 50) µm(No. 100) Pan 3 0— Total Fineness modulus = 283 ÷ 100 = 2.83

27 Aggregates for Concrete Maximum Aggregate Size and Water Requirement

28 Aggregates for Concrete Maximum Aggregate Size and Cement Requirement

29 Aggregates for Concrete Combined Aggregate Grading

30 Aggregates for Concrete Videograder

31 Aggregates for Concrete Moisture Conditions

32 Aggregates for Concrete Bulking of Sand

33 Aggregates for Concrete

34 D-Cracking

35 Aggregates for Concrete Drying Shrinkage

36 Aggregates for Concrete Harmful Materials (1) SubstancesEffect on concreteTest designation Organic impurities Affects setting and hardening, may cause deterioration ASTM C 40 ASTM C 87 (AASHTO T 21) (AASHTO T 71) Materials finer than the 75-µm (No. 200) sieve Affects bond, increases water requirement ASTM C 117(AASHTO T 11) Coal, lignite, or other lightweight materials Affects durability, may cause stains and popouts ASTM C 123(AASHTO T 113) Soft particlesAffects durabilityASTM C 235

37 Aggregates for Concrete Harmful Materials (2) SubstancesEffect on concreteTest designation Clay lumps and friable particles Affects workability and durability, may cause popouts ASTM C 142(AASHTO T 112) Chert of less than 2.40 relative density Affects durability, may cause popouts ASTM C 123 ASTM C 295 (AASHTO T 113) Alkali-reactive aggregates Causes abnormal expansion, map cracking, and popouts ASTM C 227, C 289, C 295, C 342, C 586 C 1260, C 1293 (AASHTO T 303)

38 Aggregates for Concrete Harmful Reactive Substances Alkali-silica reactive substances Alkali-carbonate reactive substances Andesites Argillites Certain siliceous limestones and dolomites Chalcedonic cherts Chalcedony Cristobalite Dacites Glassy or crypto- crystalline volcanics Granite gneiss Graywackes Metagray- wackes Opal Opaline shales Phylites Quartzites Quartzoses Cherts Rhyolites Schists Siliceous shales Strained quartz and certain other forms of quartz Synthetic and natural silicious glass Tridymite Calcitic dolomites Dolomitic limestones Fine-grained dolomites

39 Aggregates for Concrete Popouts

40 Aggregates for Concrete Iron Particles in Aggregates

41 Aggregates for Concrete Alkali- Aggregate Reactivity ( AAR ) n — is a reaction between the active mineral constituents of some aggregates and the sodium and potassium alkali hydroxides and calcium hydroxide in the concrete. u Alkali-Silica Reaction (ASR) u Alkali-Carbonate Reaction (ACR )

42 Aggregates for Concrete Alkali-Silica Reaction (ASR) n Visual Symptoms u Network of cracks u Closed or spalled joints u Relative displacements

43 Aggregates for Concrete n Visual Symptoms (cont.) u Fragments breaking out of the surface (popouts) n Mechanism 1.Alkali hydroxide + reactive silica gel  reaction product (alkali-silica gel) 2.Gel reaction product + moisture  expansion Alkali-Silica Reaction (ASR)

44 Aggregates for Concrete n Influencing Factors u Reactive forms of silica in the aggregate, u High-alkali (pH) pore solution u Sufficient moisture If one of these conditions is absent ― ASR cannot occur. Alkali-Silica Reaction (ASR)

45 Aggregates for Concrete n Test Methods u Mortar-Bar Method (ASTM 227) u Chemical Method (ASTM C 289) u Petrographic Examination (ASTM C 295) u Rapid Mortar-Bar Test (ASTM C 1260 or AASHTO T 303) u Concrete Prism Test (ASTM C 1293 ) Alkali-Silica Reaction (ASR)

46 Aggregates for Concrete n Controlling ASR u Non-reactive aggregates u Supplementary cementing materials or blended cements u Limit alkali loading u Lithium-based admixtures u Limestone sweetening (~30% replacement of reactive aggregate with crushed limestone Alkali-Silica Reaction (ASR)

47 Aggregates for Concrete Effect of Supplementary Cementing Materials on ASR

48 Aggregates for Concrete Alkali-Carbonate Reaction (ACR) n Influencing factors u Clay content, or insoluble residue content, in the range of 5% to 25% u Calcite-to-dolomite ratio of approximately 1:1 u Increase in the dolomite volume u Small size of the discrete dolomite crystals (rhombs) suspended in a clay matrix

49 Aggregates for Concrete Alkali-Carbonate Reaction n Test methods u Petrographic examination (ASTM C 295) u Rock cylinder method (ASTM C 586) u Concrete prism test (ASTM C 1105)

50 Aggregates for Concrete Alkali-Carbonate Reaction n Controlling ACR u Selective quarrying to avoid reactive aggregate u Blend aggregate according to Appendix in ASTM C 1105 u Limit aggregate size to smallest practical

51 Aggregates for Concrete Handling and Storing Aggregates

52 Aggregates for Concrete Recycled-Concrete Aggregate

53 Aggregates for Concrete

54 Water Absorption

55 Aggregates for Concrete Videos 1/6 AggregatesGrading curves

56 Aggregates for Concrete Videos 2/6 Void contentFineness modulus

57 Aggregates for Concrete Videos 3/6 Gap graded aggregate Particle shape

58 Aggregates for Concrete Videos 4/6 Bulk Density (Unit Weight)Specific Gravity

59 Aggregates for Concrete Videos 5/6 Absorption Beneficiation

60 Aggregates for Concrete Videos 6/6 Handling and Storing


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