Author: Haroon Khalil

Tar is the viscous liquid produced when natural organic materials such as coal, petroleum, wood, etc., are carbonised. Depending on the material from which tar is obtained, it is called as wood tar or coal tar. Coal tar is used mostly for road work because of its superior quality. Road tar is produced by undergoing…

Bitumen is a hydrocarbon material of either natural or pyrogenous origin, found in gaseous, liquid, semi-solid or solid form. It is a complex organic material which is completely soluble in carbon disulphide. It occurs either naturally or may be obtained during the distillation of petroleum. Bitumen consists of colloidal hydrocarbon materials of asphalte nets, resins…

Bituminous materials may be broadly classified as bitumen and tar.

Following are the properties of gypsum plaster:

Gypsum is hydrated sulphate of calcium (CaSO4 · 2H2O). It is not available in nature in pure form but contains impurities such as alumina, calcium carbonate, magnesium carbonate and silica. It is a white crystalline substance less soluble in water but soluble in hydrochloric acid. As a binding material, it sets and hardens quickly. Gypsum heated between…

Fly ash is most widely used in many profitable applications such as the following: 1. Application in Concrete as Admixture Fly ash is the widely used pozzolanic material all over the world. Addition of fly ash, apart from playing the role of an admixture, imparts the following properties to concrete: The importance and use of…

Main constituents of fly ash are: Silicon dioxide (SiO2) = 30–60% Aluminium oxide (Al2O3) = 15–30% Unburnt fuel (carbon) = up to 30% Calcium oxide (CaO) = 1–7% Magnesium oxide (MgO) = small amount Sulphur trioxide (SO3) = small amount The chemical composition of fly ash varies with the type of fuel burnt, load on…

Fly ash is a fine grained residue resulting from the combustion of pulverised coal or lignite in boilers. As it is in ash form it is easily transported by the flue gases and collected by mechanical or electrostatic separators. Mainly it consists of spherical glassy particles ranging from 1 to 150 µ m in diameter…

Some of the products of asbestos which are manufactured are discussed below. 1. Asbestos Boards Asbestos fibres and Portland cement are mixed and moulded under hydraulic pressures. These are available in board and sheet forms. Some of the commercial forms are claddings, roofing and decking units. Asbestos boards are available in natural mottled grey colour…