Cement

# Cement is pulverized material that develops the bending force dur to the reaction with water.

# cement may be two types
       ● hydraulic cement :  cement are not only hardens by reacted with water but also forms water resistance product. ( stable under water )
        ● Non hydraulic cement : not produce water resistance product.

# portland cement is hydraulic cement.

# Manufacture of portlant cement

Primary consituent : calcium silicate
Raw material : calcium - limestone, chalks ( CaO+CO2)
                           Silica- clays and shales (SiO2 + Al2O3 + Fe2O3 + H20)
   ( 2/3 rd of calcium + 1/3rd of clay)

# cement contained C3S or C2S, if the cement having C3S is good because it dried early and rapid hydration start that cause more strength. Where C2S dried slowly and low hydration cause less hardening.

# C3A caused fast reacting with water and may lead immediate stiffing of paste called flash set. Gypson used on it to prolong the reaction with water.

# high silica on cement prolongs the setting time gives more strength.

# high lime also increase the setting time.
# iron oxide presence on the cement is in the form of catalyst result burning process.

# Hydration of cement :
The hydration of cement is the reaction of cement with water, actually it continues for long period. Due to this heat is generate and the strucure made with the cement is hardening. It also depend upon the calcium sulphate present in the cement where C2S takes hydration in slow rate cause of not as much hardening as C3S. C3s, if presented in the cement it react faster and consequently becomes hardening.
The hydration is classified into two types :
1. Calcium silicate hydrates 
2. Tri calcium aluminate hydrates.
Calcium silicate hydrates :
2C3S+6H --------> C3S2H3 + 3 Ca (OH)2

2C2s + 4H --------> C3S2H3 + Ca (OH)2

Where, C = CaO
              S = SiO2
             H = H20
• C3S2H3 is the calcium silicate hydrate is gel.

# components present in portland cement.
CaO --> calcium oxide (C)
Al2O3 --> Alumina (A)
SiO2 --> silica (S)
SO3 --> Sulphate (S)
H2O --> water (H)
Similarly, Reactive compounds present are :
C3S - Tricalcium silicate
C2S - Dicalcium silicate
C3A - Tricalcium aluminate
C4AF- Tetra calcium alumino ferrite.
Due to mixing of above compounents a complex is formed which is called Bogue's compound.
C3S : 4.07 (C)-7.60 (S)-6.72 (A)-1.43 (F)-2.85 (š)
C2S : 2.87 (S)-0.754 (C3S)
C3A : 2.65 (A)-1.69 (F)
C4AF : 3.04 (F)
Here, terms C, S, A, F, Š and C3S etc to be represented by %.