Specific Gravity of Aggregates Quiz
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Questions and Answers

What does a lesser abrasion in LA Abrasion Test indicate for aggregate quality?

  • Low quality aggregate
  • High quality aggregate (correct)
  • No relationship to aggregate quality
  • Neutral impact on aggregate quality

    • Why is resistance to weathering action an important factor in choosing aggregate?

  • To improve the economy of the mixture
  • To increase potential strength and stability of the hardened mass
  • To ensure durability of concrete structures (correct)
  • To reduce impurities in aggregate

    • According to the rules of thumb, why do graded aggregates pack more densely than one-sized aggregates?

  • Because graded aggregates have higher abrasion levels
  • As one-sized aggregates have fewer voids naturally
  • Due to the decrease in voids with compaction effort (correct)
  • Because graded aggregates have round particles

    • How is the grading of aggregate determined in ASTM C136 Sieve Analysis?

    <p>By arranging sieves based on decreasing opening size</p> Signup and view all the answers

    What effect does using smooth and rounded aggregate have on concrete workability?

    <p>Increases workability</p> Signup and view all the answers

    How does a rough surface on aggregates impact the bond strength between cement paste and aggregate?

    <p>Increases bond strength</p> Signup and view all the answers

    Why is it important to measure the moisture states of aggregates before mixing them with water and cement?

    <p>To ensure the right concrete properties</p> Signup and view all the answers

    What does the Apparent Specific Gravity (Gsa) measure?

    <p>Ratio of weight in air of an impermeable portion of aggregate to weight in air of water</p> Signup and view all the answers

    How is the Apparent Specific Gravity (Gsa) calculated?

    <p>A / (A - C)</p> Signup and view all the answers

    What does Bulk Specific Gravity, SSD basis measure?

    <p>Mass of saturated surface-dry sample in air</p> Signup and view all the answers

    How is the specific gravity of fine aggregates measured?

    <p>Using a pycnometer</p> Signup and view all the answers

    What does the term 'Voids' refer to in the context of aggregates?

    <p>The amount of air space in the aggregate or space between the particles</p> Signup and view all the answers

    How is void content expressed?

    <p>As a percent of gross volume which is solid volume plus volume of voids</p> Signup and view all the answers

    Why is the unit weight of aggregate important in designing concrete mix proportions?

    <p>To predict the density of concrete made with the aggregate</p> Signup and view all the answers

    What does a bulk density range of 95-105 pcf indicate for normal-weight aggregates?

    <p>High density compared to lightweight aggregates</p> Signup and view all the answers

    Study Notes

    Aggregate Quality

    • A lesser abrasion in LA Abrasion Test indicates higher quality aggregate.

    Aggregate Selection

    • Resistance to weathering action is an important factor in choosing aggregate because it affects the durability of the concrete.

    Grading of Aggregates

    • Graded aggregates pack more densely than one-sized aggregates because smaller particles fill in the gaps between larger particles.
    • The grading of aggregate is determined in ASTM C136 Sieve Analysis by separating the aggregate into different sizes using a series of sieves with different mesh sizes.

    Aggregate Surface Texture and Concrete Workability

    • Using smooth and rounded aggregate improves concrete workability because it reduces the friction between the aggregate and the cement paste.
    • A rough surface on aggregates improves the bond strength between the cement paste and aggregate because it provides a better mechanical bond.

    Moisture States of Aggregates

    • It is important to measure the moisture states of aggregates before mixing them with water and cement because it affects the workability and strength of the concrete.

    Density of Aggregates

    • The Apparent Specific Gravity (Gsa) measures the ratio of the mass of a volume of aggregate to the mass of an equal volume of water.
    • The Apparent Specific Gravity (Gsa) is calculated by dividing the mass of the oven-dried aggregate by the mass of an equal volume of water.
    • The Bulk Specific Gravity, SSD basis measures the ratio of the mass of a volume of aggregate, including the absorbed and surface moisture, to the mass of an equal volume of water.
    • The specific gravity of fine aggregates is measured using a pyknometer or a gas jar.
    • Voids refer to the empty spaces between aggregate particles.
    • Void content is expressed as a percentage of the total volume of the aggregate.

    Unit Weight of Aggregates

    • The unit weight of aggregate is important in designing concrete mix proportions because it affects the volume of the concrete.
    • A bulk density range of 95-105 pcf indicates that the aggregate is normal-weight.

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    Description

    Test your knowledge on specific gravity of aggregates, including the concept of apparent specific gravity and the calculation formula. Understand the difference between specific gravity and apparent specific gravity for coarse aggregates.

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