Cements and Binders
- Cements are mostly used adhesive compounds used in construction industry.
Lime can be used as a binder material.All lime shall be freshly burnt and slaked and screened before use, the slaking should be done at site of work. Lime for works including roof terracing shall be Bisra, Satna or other approved stone lime.
(a) Quick-lime shall mean a calcined material, the major part of which is calcium oxide in natural association with a relatively small amount of magnesium oxide and capable of slaking with water.
(b) Fat lime shall mean the lime which has high calcium oxide content (between 95 and 100 percent) and is dependent for setting and hardening on the absorption of carbon dioxide from the atmosphere. This is defined as class—C which is used for finishing coat in plastering, white washing etc. and with addition of pozzolanic materials (surki) for masonry mortar.
(c) Hydraulic lime shall mean the lime which contains small quantities of silica and alumina and I or iron oxide which are in chemical combination with some of the calcium oxide content, giving a putty of mortar that has the property of setting and hardening under water.
(d) Hydrated lime shall mean a dry powder resulting from treatment of quick-lime with water enough to satisfy its chemical affinity for water under the conditions of hydration.
Classification of Lime
Class A: Eminently hydraulic lime (containing 25% to 30% of clay) used for foundations and other hydraulic structures, shall be supplied as hydrated lime only and should be used particularly
in any masonry work below G.L. It should be noted that no masonry work below G.L. should be taken up with the use of any lime, other than specified hydraulic lime. In case of doubt if any in respect of hydraulic lime being used in work below G.L., it is preferable not to use lime mortar at all below G.L.
Class C: Fat lime is used mainly for lime punning, white washing and with suitable admixture, such as surki or any other pozzolanic material to produce artificial hydraulic mortar.
Cement is the building material of concrete.from a word of Latin origin -based on hydraulic cement that is a material which hardens under water.Ancient Romans were probably the first to use concrete.But the Roman cement become obsolete and it was only in 1824 , that the modern cement known as Portland Cement was invented and patented by Joseph Aspidin, a Leeds builder and Brick Layer.Aspidin fancied to name it Portland cement because of the resemblance of the hardened cement to the natural stone occurring at Portland in England.But prior to Aspidin L.J Vicat prepared an artificial hydraulic lime by calcining an intimate mixture of lime stone and clay.This process was regarded as the leading knowledge to the manufacturer of Portland Cement.
Definition of Cement
Portland cement is the name given to a cement obtained by intimately mixing together calcareous and argillaceous or other silica – alumina and iron -oxide bearing materials, and burning them at a clinkering temperatureof 1400 degree C and grinding the resulting clinker together with 2% to 3% of Gypsum. No material other than gypsum ,water and grinding aids are added after burning.Gypsum also called Plaster of Paris is added to retard flash or immediate setting of the cement paste.
Portland Cement is therefore an extremely ground,that is,pulverized material having both adhesive and cohesive properties to provide a binding medium for the discrete ingredients such as sand and stone chips when mixed with water.