Cementitious material production from hot mixing of ironmaking and steelmaking slags

Abstract

A cementitious material has been produced using ironmaking and steelmaking slags. The slags in liquid condition were hot mixed with limestone addition. The mixture obtained were then slowly cooled and finally crushed. Chemical and mineralogical characterisation were carried out by X-ray flourescense spectroscopy (XRF) and X-ray diffraction (XRD). The slag based cementitious material was used as an additive to replace with ordinary Portland clinker (OPC) in production of cement. Compressive strength of concretes prepared using test cements with different compositions was measured and fragments of the concrete specimens were evaluated with scanning electron microscopy (SEM). It is concluded that a vitreous material was obtained at a temperature nearly 180°C lower than that of the clinkerisation process for traditional raw materials. The compressive strength of water cured specimens of the concretes produced from the slags and OPC cement showed that early strengths of the slag based cementitious material and its mixtures with Portland clinker were lower compared with OPC cement concrete. The slag based cementitious material (DC0) did not show any significant cementing properties owing to major content of gehlenite mineral via slowly cooled blast furnace (BF) slag. On the other hand, the compressive strength of OPC cement concrete decreased with increasing slag based cementitious material of the mixture. Replacement of OPC clinker with 30 wt-% slag based cementitious material in the cement is possible and it confirms a successful production from the ironmaking and the steelmaking slags, when compared with compressive strength of concrete for type I Portland cement according to ASTM C150-86. SEM studies showed characteristics of intergranular fracture in whole matrix for composition of 30 wt-% slag based clinker additive OPC concrete.