Aggregates for Concrete

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

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

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

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

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

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

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

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

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

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

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

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

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

15 Aggregate Characteristics and Tests (2) Characteristic Relative density Absorption and surface moisture Strength Def. of constituents Aggregate constituents Alkali Resistance ASTM C 70, ASTM C 127 (AASHTO T 85), ASTM C 128 (AASHTO T 84), ASTM C 566 (AASHTO T 255) ASTM C 39 (AASHTO T 22), ASTM C 78 (AASHTO T 97) ASTM C 125, ASTM C 294 Test ASTM C 127 (AASHTO T 85) fine aggregate ASTM C 128 (AASHTO T 84) coarse aggregate 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 ASTM C 227, ASTM C 289, ASTM C 295, ASTM C 342, ASTM C 586, ASTM C 1260 (AASHTO T 303), ASTM C 1293 Aggregates for

16 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 Aggregates for 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 Range of Particle Sizes

18 Fine-Aggregate Grading Limits Sieve size Percent 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 Maximum Size vs. Nominal Maximum Size of Aggregate Aggregates for Maximum size is the smallest sieve that all of a particular aggregate must pass through. Nominal maximum size is the standard sieve opening immediately smaller than the smallest through which all of the aggregate must pass. The nominal maximum-size sieve may retain 5% to 15%

20 Nominal Maximum Size of Aggregate Size should not exceed 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 Aggregates for

Coarse Aggregate Grading Size No. 57 25 to 4.75 mm [1 in. to No. 4] Sieve size 37.5 mm (1½ in.

21 Coarse Aggregate Grading Size No to 4.75 mm [1 in. to No. 4] Sieve size 37.5 mm (1½ in.) Percent passing by mass mm 12.5 mm 4.75 mm 2.36 mm (1 in.) (½ in.) (No. 4) (No. 8) 95 to to 60 0 to 10 0 to 5 Aggregates for

22 Grading Limits

23 Reduction of Voids

24 Dispersion of Aggregates

25 Fineness Modulus (FM) Aggregates for 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. 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 Sieve Analysis and FM of Sand Sieve size 9.5 mm (3/8 in.) 4.75 mm (No. 4) 2.36 mm (No. 8) 1.18 mm (No. 16) 600 µm (No. 30) 300 µm (No. 50) 150 µm (No. 100) Pan Total Aggregates for Percentage of individual fraction retained, by mass Percentage passing, by mass Cumulative percentage retained, by mass Fineness modulus = = 2.83

27 Maximum Aggregate Size and Water Requirement

28 Maximum Aggregate Size and Cement Requirement

29 Combined Aggregate Grading

30 Videograder

31 Moisture Conditions

32 Bulking of Sand

34 D-Cracking

35 Drying Shrinkage

36 Harmful Materials (1) Substances Organic impurities Materials finer than the 75-µm (No. 200) sieve Coal, lignite, or other lightweight materials Soft particles Effect on concrete Affects setting and hardening, may cause deterioration Affects bond, increases water requirement Affects durability, may cause stains and popouts Affects durability Test designation 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 235 Aggregates for

37 Harmful Materials (2) Substances Effect on concrete Test 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 C1260, C1293 (AASHTO T 303) Aggregates for

38 Harmful Reactive Substances Andesites Argillites Certain siliceous limestones and dolomites Chalcedonic cherts Chalcedony Cristobalite Dacites Aggregates for Alkali-silica reactive substances Glassy or cryptocrystalline volcanics Granite gneiss Graywackes Metagraywackes 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 Alkali-carbonate reactive substances Calcitic dolomites Dolomitic limestones Fine-grained dolomites

39 Popouts

40 Iron Particles in Aggregates

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

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

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

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

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

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

47 Effect of Supplementary Cementing Materials on ASR

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

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

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

51 Handling and Storing Aggregates

52 Recycled- Aggregate

54 Water Absorption

55 Videos 1/6 Aggregates Grading curves

56 Videos 2/6 Void content Fineness modulus

57 Videos 3/6 Gap graded aggregate Particle shape

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

59 Videos 5/6 Absorption Beneficiation

60 Videos 6/6 Handling and Storing

Engineering materials

1 Engineering materials Lecture 9 Aggregates 2 Composition and structure Natural aggregates are derived from rocks. Classification: Igneous( 火成岩 ), sedimentary ( 沉積岩 ) and metamorphic ( 變質岩 ) Fine or coarse