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Concrete Mix Design Flashcards

7 cards from real ACI Certification 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. What does the fineness modulus (FM) of fine aggregate indicate?

    Answer: An index of the overall coarseness or fineness of the aggregate

    FM is computed by summing cumulative percentages retained on a specified series of sieves and dividing by 100; higher values denote coarser material.

  2. According to ACI 211.1, as the fineness modulus (FM) of fine aggregate increases, the recommended bulk volume of coarse aggregate per unit volume of concrete:

    Answer: Increases

    Coarser fine aggregate (higher FM) has fewer small particles, allowing a greater volume of coarse aggregate while still maintaining adequate workability.

  3. What is the primary purpose of preparing trial batches during concrete mix design?

    Answer: To verify that the calculated mix proportions meet specified requirements under actual conditions

    Trial batches confirm that calculated proportions achieve required fresh properties (slump, air content) and hardened strength before full-scale production.

  4. Which ACI document provides the standard practice for selecting proportions for normal, heavyweight, and mass concrete?

    Answer: ACI 211.1

    ACI 211.1, 'Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete,' provides the absolute volume method for mix design.

  5. The saturated surface-dry (SSD) condition of aggregate is used as the reference state in mix design because:

    Answer: It requires no moisture correction to batch water calculations

    Aggregate at SSD neither absorbs water from nor contributes free water to the mix, making it the ideal baseline for calculating batch proportions.

  6. In concrete production, 'batch weights' refer to:

    Answer: The actual quantities of all ingredients loaded into the mixer for one production batch

    Batch weights are the plant-ready quantities of cement, water, aggregates, and admixtures used to produce one mixer load of concrete.

  7. According to ACI 318, the maximum w/cm ratio for concrete subjected to deicing chemicals (severe freezing-and-thawing exposure) is:

    Answer: 0.40

    ACI 318 limits w/cm to 0.40 for severe freezing-and-thawing exposure involving deicing chemicals to minimize concrete permeability and deterioration.