Practice Test Geeks(ACI) American Concrete Institute Concrete Finisher Practice Test
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Concrete Materials & Mix Proportioning Flashcards

7 cards from real ACI practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. Aggregate that is in 'saturated surface dry' (SSD) condition means:

    Answer: Internal pores are full but the surface is dry with no free water

    SSD condition means all internal pores are saturated with water but the aggregate surface is dry, so it neither absorbs water from nor contributes water to the mix.

  2. Which chemical compound in Portland cement is primarily responsible for early strength gain (1-3 days)?

    Answer: Tricalcium silicate (C3S)

    Tricalcium silicate (C3S or alite) hydrates rapidly and is primarily responsible for early strength development in Portland cement concrete.

  3. An air-entraining admixture is added to concrete primarily to improve:

    Answer: Resistance to freeze-thaw cycles

    Entrained air bubbles provide relief spaces for water expansion during freezing, dramatically improving freeze-thaw durability.

  4. What is the typical range of air content specified for concrete exposed to severe freeze-thaw conditions with 3/4-inch maximum aggregate?

    Answer: 4–7%

    ACI 318 and ACI 211.1 recommend 4–7% total air content for concrete with 3/4-inch maximum aggregate in severe freeze-thaw and deicing salt exposure.

  5. What is the primary reason coarse aggregate gradation is important in mix design?

    Answer: It affects workability, paste content, and strength

    Well-graded coarse aggregate minimizes void content, reducing the paste needed to fill voids, which improves economy, workability, and strength.

  6. When designing a concrete mix for a pumped placement, which adjustment is commonly made?

    Answer: Increase the fine aggregate content or use a smaller maximum aggregate size

    Pumpable mixes typically require higher fine aggregate content or smaller maximum aggregate size to ensure cohesion and prevent blockages in the pump line.

  7. Accelerating admixtures (ASTM C494 Type C) are used primarily to:

    Answer: Speed up setting and early strength development

    Type C accelerators speed up cement hydration, increasing the rate of setting and early strength gain, which is useful in cold weather concreting.