Civil Engineering - Aggregates

Flashcards covering terms and definitions from lecture notes on Soil Density, Abrasion Tests, Aggregate Testing, Specific Gravity, and Organic Impurities.

Density of soil

Defined as the weight/mass per unit volume. FDT is widely used as a control test in embankment construction to ensure adequate compaction.

FDT % Degree of Compaction

95 min. (Item No. 104), 100 min. (Item No. 200), 100 min. (Item No. 201), 100 min. (Item No. 202), 100 min. (Item No. 300), 100 min. (Item No. 105)

Los Angeles Abrasion Test

Test carried out to test the hardness property of aggregates. The principle is to find the percentage wear due to relative rubbing action between the aggregate and steel balls used as abrasive charge.

Item 200 Aggregate Sub-base Course Abrasion Requirement

50% maximum

Item 201 Aggregate Base Course Abrasion Requirement

Same as Item 200

Item 202 Crushed Aggregate Base Course Abrasion Requirement

45% maximum

Item 203 Lime Stabilized Road Mix Base Course Abrasion Requirement

50% maximum

Item 204 Portland Cement Stabilized Road Mix Base Course Abrasion Requirement

Same as Item 203

Item 300 Aggregate Surface Course Abrasion Requirement

45% maximum

Item 310 Bituminous Concrete Surface Course

40% maximum

Item 311 Portland Cement Concrete Pavement Abrasion Requirement

40% maximum

Item 405 Structural Concrete Abrasion Requirement

Same as Item 311

Aggregate Subbase Course (Item 200)

Furnishing, placing and compacting an aggregate subbase course on a prepared subgrade. The coarse portion, retained on a 2.00 mm (No. 10) sieve, shall have a mass percent of wear not exceeding 50 by the Los Angeles Abrasion Tests as determined by AASHTO T 96.

Los Angeles Abrasion Machine

Apparatus used for abrasion test. Must have a hollow steel cylinder, with a wall thickness of not less than 12.4 mm closed at both ends, having an inside diameter of 711 +5 mm (28. +0.2 in.), and an inside length of 508 +5 mm (20 + 0.2 in.).

Scalf

Balance or scale accurate within 0.1 % of test load over the range required for this test.

Abrasive Charges

Steel spheres averaging approximately 46.8 mm (127/32 in.) in diameter and each having a mass of between 400 and 440 g.

Thermostatically Controlled Oven

Regularly cycles the mechanism's heating elements on and off to maintain the correct temperature. Typically set to 110+5 degree Celsius for oven-drying.

Abrasion Test Specimen Preparation

Obtain the field sample in accordance with Practice D75, and reduce the field sample to adequate sample size in accordance with Practice C702. Wash the reduced sample and oven dry at 110 +/-5°C to a constant mass, separate into individual size fractions, and recombine. Record the mass of the sample prior to test to the nearest 1 g.

Soil Aggregate Sample Preparation

Select oven-dried sample amounting to 5kg all retained on No. 10 Sieve.

Abrasive Charges for Soil Sample

12 abrasive charges will be used for soil aggregate sample

Los Angeles Abrasion Machine Operation

Place the test sample and the charges in the Los Angeles Abrasion machine and start the machine at a speed of 30 to 33 r/min for 500 rotations. After the prescribed number of rotations, discharge the material from the machine and make a preliminary separation of the sample on a sieve coarser than the 1.70-mm (No. 12) sieve. Sieve the finer portion on a 1.70-mm (No. 12) sieve in a manner conforming to Test Method C136

Aggregates

Inert materials mixed with binding material such as cement or lime for manufacturing of mortar or concrete. Used as filler in mortar and concrete and also to reduce their cost.

Natural Aggregates

Aggregates from river beds, river sand, and ex-mines. Normally rounded in shape and have smooth surface texture.

Manufactured Aggregates / Crushed Aggregates

Aggregates obtained by mechanically crushing rocks, boulders, or cobbles. Normally angular in shape and have rough surface texture.

Coarse Aggregates

Those aggregates passing through 75mm sieve (3 in) and entirely retained on 4.75mm sieve (No. 4).

Fine Aggregates

Those aggregates which pass through 4.75mm sieve.

Sieve Analysis

Determination of the proportions of the particles within certain ranges in an aggregate by separation on various sieves of different size openings.

Specific Gravity and Absorption

Tests to measure the strength or quality of the material and the water-holding capacity of the aggregates.

Unit Weight & Voids in Aggregate

Determination of bulk density ("unit weight") of aggregate in a compacted or loose condition, and calculated voids between particles in fine, coarse, or mixed aggregates.

Abrasion (Aggregate Testing)

Hardness of aggregates, or the ability to withstand wear or load or applied pressure. The test that can obtain the hardness is the abrasion test.

Soundness (Aggregate Testing)

Determines an aggregate's resistance to disintegration by weathering.

Fineness Modulus (FM)

An empirical number relating to the fineness of the aggregate. The higher the FM the coarser the aggregate. ASTM C 33 requires the FM of fine aggregate to be between 2.3 and 3.1.

Fineness Modulus Formula

F.M. = (Cumulative percentage retained on specified sieves) / 100. Specified sieves include No. 100, No. 50, No. 30, No. 16, No. 8, No. 4, 3/8", ", 1 ½ and larger increasing at a ratio of 2:1

Specific Gravity (Coarse Aggregate)

Expressed as bulk specific gravity, bulk specific gravity (saturated surface-dry (SSD)), or apparent specific gravity. Based on aggregate after 15-19 h of soaking in water.

Specific Gravity Balance

Conforming to the requirements of M 231, Class G 5. Equipped with suitable apparatus for suspending the sample container in water from the center of the weighing platform or pan of the balance.

Specific Gravity Frame

Used in conjunction with a suitable electronic balance for specific gravity determination of fresh and hardened concrete and aggregates. Consisting of a purpose-built robust frame designed to support the electronic balance a wire basket and plastic water tank.

Water tank for Specific Gravity test

A watertight tank into which the sample and container are placed for complete immersion while suspended below the balance, equipped with an overflow outlet for maintaining a constant water level

Specific Gravity of Coarse Aggregates Sample Prep

Dry sample in a suitable pan or vessel to constant mass at a temperature of 110 ± 5°C (2309°F). Allow it to cool to comfortable handling temperature, cover with water, either by immersion or by the addition of at least 6 percent moisture to the fine aggregate and permit to stand for 15 to 19 h.

Fine Aggregate Specific Gravity

This method determines (after 15-19 h of soaking in water) the bulk specific gravity and the apparent specific gravity, the bulk specific gravity on the basis of mass of saturated surface-dry (SSD) aggregate, and the absorption.

Cone Test

Hold the mold firmly on a smooth nonabsorbent surface with the large diameter down.Place a portion of the partially dried fine aggregate loosely in the mold by filling until overflow occurs and heaping additional material above the top of the mold. Lightly tamp the fine aggregate into the mold with 25 light drops of the tamper.

Organic Impurities Test

Determination of the presence of injurious organic compounds in fine aggregates that are to be used in hydraulic cement mortar or concrete.

Bottles for Organic Impurities

Colorless glass graduated bottles, approximately 240- to 470-mL (8- to 16-oz) nominal capacity, equipped with watertight stoppers or caps, not soluble in the specified reagents.

Sodium Hydroxide Solution for Organic Impurities Test

Chemical powder reagent for test on Organic Impurities

Gardner's Color Chart

Standard color guide used in the determination of the presence of impurities in the fine aggregate.

Supernatant liquid darker than organic plate No. 3

Considered to possibly contain injurious organic compounds, and further tests should be made before approving the fine aggregate for use in concrete