Concrete Materials & Mix Proportioning Flashcards

What ASTM standard governs the specification requirements for normal Portland cement used in concrete?

Answer: ASTM C150

ASTM C150 is the Standard Specification for Portland Cement, covering all five types (I through V).

In mix design, the 'fineness modulus' is a property of which concrete ingredient?

Answer: Aggregate

Fineness modulus is an index number derived from sieve analysis of fine or coarse aggregate, indicating the average size of particles.

Which admixture type is classified under ASTM C494 Type A?

Answer: Water-reducing admixture

ASTM C494 Type A admixtures are water reducers that reduce the water requirement of concrete without changing set time.

What effect does increasing the nominal maximum aggregate size have on the water requirement of a concrete mix?

Answer: Water requirement decreases

Larger maximum aggregate size reduces the total surface area of aggregate, requiring less water (and cement) to achieve the same workability.

Ground granulated blast-furnace slag (GGBFS) is classified as which type of supplementary cementitious material?

Answer: Latent hydraulic binder

GGBFS is a latent hydraulic binder that reacts with water in the presence of an alkali activator (calcium hydroxide from cement hydration) to form cementitious products.

ACI 211.1 recommends selecting the water-cement ratio based primarily on which two criteria?

Answer: Required strength and durability exposure conditions

ACI 211.1 selects w/c ratio based on the required compressive strength and the durability demands of the exposure environment, using the more restrictive value.

What does 'absolute volume method' mean in ACI concrete mix design?

Answer: Calculating the volume each ingredient occupies in a unit volume of concrete

The absolute volume method calculates the solid volume each material (cement, water, aggregates, air) contributes so they sum to exactly 1 cubic yard or cubic meter of concrete.