CGN3501C Test 1 Study Guide

What percentage of volume in concrete is filled by aggregate?

60-80%

What are the functions of aggregate in concrete?

Economy, strength, reduction in shrinkage and expansion.

What are the desirable characteristics of aggregates?

Hard, strong, durable, free of organic impurities, low alkali reactivity with cement, and proper gradation.

How is aggregate gradation defined?

Size distribution of aggregate particles.

What is the size of coarse aggregate?

Particles retained on No. 4 sieve (4.75 mm or 3/16 in).

What is the difference between coarse and fine aggregate?

Coarse aggregate retains on No. 4 sieve, fine aggregate passes through No. 4 sieve.

What are natural mineral aggregates?

Sand, gravel, crushed stone - majority of aggregates.

What are examples of artificial aggregates?

Blast furnace slag, expanded clay, and expanded shale.

What characterizes intrusive igneous rock?

Formed by slow cooling beneath earth’s surface; coarser grain.

What is the purpose of the L.A. Abrasion Test?

To determine hardness or resistance to abrasion of an aggregate.

What is the maximum allowable L.A. loss according to FDOT specifications?

Less than 45%.

What does the Aggregate Soundness Test measure?

Resistance of an aggregate to weathering.

What is the desirable soundness loss percentage according to FDOT specifications?

Less than 12%.

What classifies a lightweight aggregate?

An aggregate with specific gravity less than 2.0.

What is a typical maximum allowed percentage of lightweight particles for coal and lignite?

0.5–1%.

What does sieve analysis determine?

The gradation (size distribution) of aggregates.

How is the fineness modulus calculated?

Sum of cumulative percentages retained on standard sieves divided by 100.

What does it mean for an aggregate to be well-graded?

Well distributed in various sizes, resulting in low air voids and high density when compacted.

What does maximum density gradation refer to?

A method to calculate the maximum density of aggregates.

How is bulk density defined?

Mass of aggregate divided by (volume of solids + voids).

What is the formula for specific gravity for an impermeable solid?

Specific Gravity = Wt. in air / (wt. in air - wt. in water).