ABSTRACT
Portland cement is an active hydraulic binder, i.e. a ‘binder that sets and hardens by chemical interaction with water and is capable of doing so under water without the addition of an activator such as lime’ (BS 6100, section 6.1, 1984). It is obtained by burning, at a clinkering temperature (about 1450°C), a homogeneous predetermined mixture of materials comprising lime (CaO), silica (SiO2), a small proportion of alumina (Al2O3), and generally iron oxide (Fe2O3). The resulting clinker is finely ground (i.e. average particle size of 10 µm) together with a few percent of gypsum to give, what is commonly known as, Portland cement. This is, however, a generic term for various forms (types) of Portland cement which include, in addition to ordinary Portland cement (OPC), rapid-hardening Portland cement (RHPC), low-heat Portland cement (LHPC), sulphate-resisting Portland cement (SRPC) and several others.
