ADMIXTURES
1. What is the definition of "Admixture" according to ASTM C125?
2. What does an air-entraining admixture typically consist of? How does it usually work in
entraining air in a concrete?
3. What are the effects of an air-entraining admixture on (A) the workability of fresh concrete,
(B) the strength of hardened concrete, (C) the density of hardened concrete, and (D) the
durability of hardened concrete, if the proportioning of the other mix ingredients are kept the
same? Explain why air entrainment in concrete can improve its durability.
4. What does a water-reducing admixture typically consist of? How does it usually work in
improving the workability of a fresh concrete?
5. What are the differences between (a) a water-reducing admixture, (b) a high-range water-
reducing admixture, and (c) a plasticizing admixture? What are the possible benefits from the
use of these admixtures?
6. How do set-control admixtures usually work in retarding or accelerating the hydration rate of
cement in concrete?
7. What are the possible applications of a retarding admixture?
8. What are the possible applications of an accelerating admixture?
9. What are the effects of addition of calcium chloride on properties of fresh and hardened
concrete?
10. Describe the three classes of pozzolanic materials as defined in ASTM C 618.
11. Describe the particle shape, size, fineness, specific gravity and composition of fly ash.
12. Describe the three different grades of ground granulated blast-furnace slag as defined in
ASTM C989.
13. Describe the particle shape, size, fineness, specific gravity and composition of silica fume.
Why is silica fume a more effective pozzolanic material than fly ash or ground blast-furnace
slag?
14. Describe the applications of fly ash, blast-furnace slag and silica fume admixtures in
concrete.
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