3501-2 - Aggregates for Concrete Aggregate ( 60 - 80 % by...

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1 Aggregates for Concrete Aggregate ( 60 - 80 % by volume ) FUNCTIONS OF AGGREGATE IN CONCRETE 1. _________________________________ 2. _________________________________ 3. _________________________________ DESIRABLE CHARACTERISTICS OF AGGREGATES 1. _________________________ 2. _________________________ 3. _________________________ 4. ______________________________ _ ___________________________
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2 Classifications of Aggregate •By S i z e – Coarse aggregate - particles retained on No.4 sieve (4.75mm or 3/16 in.) – Fine aggregate - particles passing No. 4 sieve. • By Source – Natural mineral aggregate - sand, gravel , crushed stone. – Artificial or synthetic aggregate - blast-furnace slag, expanded clay, expanded shale. Classifications of Aggregate (continued) • By Types of Rock 1. Igneous rock - formed on cooling of the magma. • Intrusive igneous - formed by slow cooling beneath earth’s surface. Characteristics: completely crystalline minerals, coarser grain. Examples: granite, trap rock. • Extrusive igneous - formed by more rapid cooling at or near earth’s surface. Characteristics: finer grain, minerals with smaller crystals or glassy structures. Examples: basalt, perlite. Classifications of Aggregate (continued) 2. Sedimentary Rock - formed from disintegration of other rocks and deposited as sediments. Examples: limestone, sandstone, shale 3. Metamorphic Rock - Igneous or sedimentary rocks that have changed its structure due to heat and pressure. Usually harder and denser. Examples: marble, slate.
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3 Prediction of Behavior of Aggregates in Service • From past performance record - The best basis for prediction of performance. • From mineral composition. For example: the minerals amorphous opal, chalcedony & tridymite are known to cause alkali-silica reaction. • From results of tests - This method is most commonly used. L.A. Abrasion Test Purpose: _________________________ _________________________________ Los Angeles Abrasion Machine ASTM C 131 -For aggregates smaller than 37.5 mm (1.5 in.) ASTM C 535 aggregates larger than 19.0 mm (3/4 in.) L.A. Abrasion Machine
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4 L.A. Abrasion Machine L.A. Abrasion Test Procedures 1. Run sieve analysis on test sample to determine weight retained on #12 sieve (1.7 mm or 0.067 in.). Place test sample in L.A. testing machine (rotating drum with metal balls inside) C131 - 5,000 g sample, 6 to 12 metal balls (depending on aggregate size) C535 - 10,000 g sample, 12 metal balls 2. The L.A. machine is rotated at a speed of 30 to 33-rpm for 500 revs. L.A. Abrasion Test Procedures (Continued) 3. Run sieve analysis on test sample after the test. 4. L.A. loss is computed as: FDOT Specs: L.A. Loss should be less than 45%
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5 L.A. Abrasion Test Result Example Weight of sample retained on #12 before test = 5,000 g Weight of sample retained on #12 after test = 3,254 g Result reported: L.A. Loss = = Aggregate Soundness Test
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3501-2 - Aggregates for Concrete Aggregate ( 60 - 80 % by...

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