Hydraulic Cements Flashcards
Main components of concrete (%)
- Air 6%
- portland cement 11%
- course agg. 41%
- Fine agg. 26%
- Water 16%
What is the difference between hydraulic cements and nonhydraulic cements?
Hydraulic cements are stable under water, hydration products of nonhydrolic cements are not water resistant.
Short hand notation for cement chemical composition
- C (CaO, calcium oxide)
- A (Al2O3, alumina)
- S (SiO, silica)
- S_ (SO3, Sulfate)
- H (H2O, water)
What are the reactive compounds of cement?
- C3S (tricalsium silicate)
- C2S (dicalcium silicate)
- C3A (tricalsium aluminate)
- CS_H2 (gypsm)
- C4AF (tetra-calcium alumino ferrite)
Composition of cement compounds
- C3S = 3CaO * SiO2
- C2S = 2Cao * SiO2
- C3A = 3CaO * Al2O3
- C4AF = 4CaO * Al2O3 * Fe2O3
- C4A3S_ = 4CaO * 3Al2O3 * SO3
The chemical products of hydration are
- C3S2H3 (C-S-H gel)
- Ca(OH)2 (CH Calcium hydroxide)
- C6AS_3H32 (ettringite)
- C4ASH12 (monosulfate)
What is the morphology and amount of CSH in Hydrated concrete?
Poorly crystalline, high surface area: strong bonding energy. (50-60%)
What is the morphology and amount of CH in concrete?
Large hexagonal crystals, low surface area: poor bonding energy (20-25%)
What is the morphology and amount of CAS_H in concrete?
C6AS_H32 = Long well crystalized needles
C4AS_H12-18 = Hexagonal - small crystals
(15-20%)
Whats the correlation between cement strength and cement fineness?
The finer the cement, the stronger it is. The cement will react more rapidly.
What is Type 1 cement used for?
General purpose. use when special properties are not specified.
What is type 2 cement used for?
For general use yet more specified towards moderate sulfate resistance or if moderate heat of hydration is desired.
What is type 3 cement used for?
Used for high early strength cement (limit the C3A content of the cement to a max of 15%).
What is type 4 cement used for?
For use when low heat of hydration is desired.
What is type 5 cement used for?
Used for high sulfate resistance. (max limit of 5% C3A).
