binding materials

binding materials

1. lime= generally cao , calcination of limestone

   • quick lime = calcination of pure limestone
   • slaked (hydrated) lime = absorption of water by quick lime, link between the lime and required qty of water
   • fat lime or rich lime = it has 95% of cao only, becomes hard only in the presence of Co2, white color, releases more heat in presence of slaking and volume increases two to three time of its original qty
   • hydraulic lime = can set in the water(in absence of carbn dioxide), it has small qty of silica-alumina-iron oxide
   • poor or lean lime = contains more impurties, so used for small works

2. cement

   • cement= lime 63%+ alumina 6% + iron oxide 3% + magnesium oxide 2.5% + sulphur trioxide 1.5% + loss ignition 1.5% + alkalies 0.5%,,, burnt in 1500c,,,, gypsum(1 to 3%),, after mixing everything and the output clinker has tricalcium sulphate(4%), dicalcium silicate(32%), tricalcium aluminate(10.5%) and trtra calcium alumino ferrite(9%)
     • lime, silica and iron oxide provides good strength,,,alumina gives quick setting,, excess of alkalies causes efflorescence,,mgo and so3 aren't desirable
     • tricalcium silicate is more then the better will be the cement---- tricalcium aluminate and tetra calcium alumino ferrite are responsible for the initial setting time of cement
   • testing of portland cement= fineness test--(sieve method or air permeability) shouldn't exceed 10% in 90 micron in sieve and in air permeability test a good portland cement shouldn't hav specific surface less than 2250 cm2/g of cement, consistency test--water reqd for preparng for cement pastes of std consistency by vicat app (initial, final and normal consistency),,,soundness test, tensile strength test, compressive strength test

3. mortar and concrete