Material Testing Flashcards

What does the term 'water-cement ratio' directly influence in concrete mix design?

Answer: Strength and durability

The water-cement ratio is the primary factor controlling concrete strength and durability — lower ratios produce stronger, more durable concrete.

When performing a sieve analysis on fine aggregate, which sieve size defines the boundary between fine and coarse aggregate?

Answer: No. 4 (4.75 mm)

The No. 4 (4.75 mm) sieve is the standard dividing line between fine aggregate (passing) and coarse aggregate (retained).

A field density test using the sand cone method yields a wet density of 126 pcf and a field moisture of 8.5%. What is the dry density?

Answer: 116.1 pcf

Dry density = wet density / (1 + moisture fraction) = 126 / 1.085 ≈ 116.1 pcf.

What ASTM standard covers sampling freshly mixed concrete?

Answer: ASTM C 172

ASTM C 172 is the standard practice for sampling freshly mixed concrete from a truck or batch plant discharge.

Which test determines the soundness of aggregate when exposed to freeze-thaw or wetting-and-drying cycles?

Answer: Sodium or magnesium sulfate soundness test

The sodium or magnesium sulfate soundness test simulates the deterioration effects of freeze-thaw cycles on aggregate by cycling immersion and oven drying.

What is the minimum number of concrete cylinders typically cast per test set for standard acceptance testing?

Answer: 2

A minimum of two cylinders are cast per test set — one is broken at 28 days and one serves as a hold or early-break specimen.

For asphalt pavement, the term 'voids in the mineral aggregate' (VMA) refers to:

Answer: Total void space between aggregate particles including air voids and asphalt binder

VMA is the intergranular void space among the aggregate particles in a compacted paving mixture, including spaces filled with air and asphalt binder.