CONCRETE IN HOT ENVIRONMENTS - CHAPTER 1 ppsx

Chapter 1

Portland Cement

1.1. INTRODUCTION

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. It will

be shown later that the different forms of the cement are produced by

changing the proportions of the raw materials, and thereby, also, the

mineralogical composition of the resulting cements (see section 1.5).

Copyright 1993 E & FN Spon