Cement is an essential material in today’s society because, as a major constituent of concrete, it forms a fundamental element of any housing or infrastructure development. The chemical process of making cement clinker produces CO2, a major greenhouse gas contributing to climate change. This makes it imperative for us to find ways of using this resource more efficiently. Using waste from other industries, as a raw material is a huge opportunity for the cement industry to reduce its environmental impact. Cement extenders are used as a substitute for some of the Portland cement in concrete. The reasons for the use of extenders, is a growing awareness of the engineering, economical and ecological benefits and the variety of useful enhancements, which they give to the concrete properties. The aim of the research is to determine whether a gasification ash can be used as a cement extender in concrete. In this study the properties of cement and concrete containing gasification ash was compared to the properties of cement and concrete containing fly ash. The physical, chemical and mineralogical composition of a gasification ash sample was investigated, and it was found that gasification ash has an angular shape and a similar chemical composition as fly ash. The chemical requirements of the gasification ash meet the majority of the requirements specified for cement extenders. Where limits are exceeded it is by a very narrow margin. The effect of a gasification ash on the short and long term properties of concrete of both interblending and intergrinding was investigated. The experimental work revealed that gasification ash improves the compressive and tensile strength of concrete in both interblending and intergrinding. Gasification ash does not have a detrimental effect on stiffness of concrete, and did not creep significantly more than concrete containing fly ash. The porosity and permeability does not increase when gasification ash is used as a cement extender. Gasification ash should therefore not decrease the durability of concrete. The use of gasification ash as a cement extender has advantages to both the cement industry and the environment.
Dissertation (MEng(Structural))--University of Pretoria, 2007.