Material Testing Flashcards

Which ASTM standard covers the Standard Specification for Concrete Aggregates?

Answer: ASTM C 33

ASTM C 33 specifies requirements for fine and coarse aggregates for use in portland cement concrete.

A compaction test result shows 94% relative compaction. The project specification requires 95%. What should the inspector do?

Answer: Require the contractor to recompact and retest the failing area

When a compaction test fails specification requirements, the contractor must recompact the failing area and pass a retest before work can proceed.

What characteristic does the California Bearing Ratio (CBR) test measure?

Answer: The load-bearing strength of subgrade relative to a standard crushed rock

CBR measures the load-bearing capacity of a subgrade soil by comparing the force required to penetrate it with the force required to penetrate standard crushed California limestone.

Viscosity grading of asphalt binders was largely replaced by which modern grading system?

Answer: Superpave Performance Grading (PG) system

The Superpave Performance Grading system replaced AC and AR viscosity grades, specifying asphalt binder performance over the actual temperature range at the project location.

What does a 'plastic limit' value represent in soil classification?

Answer: The moisture content below which soil crumbles when rolled into 1/8-inch threads

The plastic limit is the moisture content below which a soil behaves as a semi-solid and crumbles when attempting to roll it into 1/8-inch diameter threads.

When testing freshly mixed concrete, the air content measured by the pressure meter method (ASTM C 231) is applicable to:

Answer: Normal weight concrete only — not lightweight aggregate concrete

ASTM C 231 (pressure method) applies only to normal weight concrete; porous lightweight aggregates absorb pressure and give inaccurate readings requiring the volumetric method (ASTM C 173).

A pipe joint leakage test requires maintaining 4.0 psi for 15 minutes with no drop. The gauge reads 4.0 psi at start and 3.6 psi at 15 minutes. The correct conclusion is:

Answer: The joint fails and must be repaired and retested

Any pressure drop below the specified minimum during the required hold time constitutes a failure; the joint must be repaired and retested until it maintains pressure.