Properties of alinite cement produced by using soda sludge

A production route of alinite cement clinker using the waste material of the Solvay process of the soda industry as the main raw material was searched. Soda sludge (73·5 wt%), clay (26·3 wt%) and minor amounts of iron ore (0·2 wt%) were mixed to obtain a raw mix that is later burned at nine different burning schemes. Four different burning temperatures (1050, 1100, 1150 and 1200°C) and three different burning durations (60, 90 and 180 min) were applied for clinkerisation. The clinkers obtained were investigated by chemical, mineralogical and scanning electron microscopy analyses. The analyses confirmed the formation of the alinite phase [Ca₁₀Mg_0·8[(SiO₄)_3·4(AlO₄)_0·6O₂Cl]] in the clinkers. Results revealed that increasing burning temperature and duration did not cause a significant change in the phases developed, but caused an increase in the crystal size of the phases. Compressive strength tests were also performed on the produced alinite cements to determine the appropriateness of these cements for structural purposes. It is envisaged that the alinite cement produced at a substantially lower temperature than normal Portland cement clinker will lead to benefits not only in terms of economy and ecology but also sustainability of the cement production.