ACI Aggregate Properties and Testing Questions and Answers

Question 1

According to ASTM C136/C136M, what is the primary reason for performing a sieve analysis on fine and coarse aggregates?

Accepted Answer

To determine the particle size distribution (grading) of the aggregate

Answer

ASTM C136/C136M is the standard test method for determining the particle size distribution, also known as grading, of fine and coarse aggregates. The results are used to check for compliance with specification requirements and for quality control in the production of aggregates and concrete.

Question 2

A technician is tasked with determining the bulk density (unit weight) of a coarse aggregate sample by rodding, in accordance with ASTM C29/C29M. The procedure involves placing the aggregate into a calibrated measure in how many approximately equal layers?

Accepted Answer

Three layers

Answer

The rodding procedure described in ASTM C29/C29M requires the calibrated measure to be filled in three approximately equal layers. Each layer is then rodded 25 times with a tamping rod to achieve a standard compacted state before the next layer is added.

Question 3

Which of the following properties is determined using the Los Angeles (L.A.) abrasion test (ASTM C131)?

Accepted Answer

The resistance of coarse aggregate to degradation by abrasion and impact

Answer

The L.A. abrasion test (ASTM C131) is used to measure the toughness of coarse aggregate, specifically its resistance to degradation from a combination of abrasion, impact, and grinding in a rotating steel drum with a specified charge of steel spheres.

Question 4

A laboratory is testing a coarse aggregate sample for specific gravity and absorption according to ASTM C127. The aggregate is soaked for a prescribed period and then dried to a saturated-surface-dry (SSD) condition. What does the SSD condition signify?

Accepted Answer

The aggregate's permeable pores are filled with water, but the surfaces of the particles are dry.

Answer

The saturated-surface-dry (SSD) condition, as defined in ASTM C127, is a state where the aggregate's internal pores are filled with water, but the outer surfaces are dry. This is a critical reference point for calculating bulk specific gravity (SSD) and absorption.

Question 5

When an accurate determination of the material finer than the 75-µm (No. 200) sieve is required for an aggregate sample, ASTM C136 states that dry sieving alone is insufficient. Which test method should be performed prior to the dry sieve analysis?

Accepted Answer

ASTM C117 (Materials Finer than 75-µm Sieve by Washing)

Answer

ASTM C136 explicitly states that for an accurate determination of material finer than the 75-µm (No. 200) sieve, Test Method C117 should be used. This method uses washing to separate fine particles more completely than dry sieving alone can achieve. The results from C117 are then used in the C136 calculations.

ACI (American Concrete Institute Certification) Practice Test

ACI (American Concrete Institute Certification) Practice Test

ACI Aggregate Properties and Testing Questions and Answers