STRENGTH AND SULPHATE RESISTANCE OF CEMENT MORTARS CONTAINING NEUTRALISED BAUXITE REFINERY RESIDUE (BAUXSOLTM)

Bauxite refinery residue (BRR) is a major disposal problem in the aluminium industry due to its causticity. BRR can be neutralised using seawater or by artificial brines, which converts the soluble alkalinity into low soluble minerals; artificiallyneutralised BRR (Bauxsol™) is currently marketed by Virotec International plc. The reduced causticity and sodicity, metal binding and acid neutralising capacity of Bauxsol™, suggests that there is potential to use it in cementitious materials (e.g. concretes) with the possibility to improve their physical properties. On this basis, a comprehensive research programme was carried out to establish if the use of Bauxsol™ in concrete production could provide benefit without any adverse detrimental affects. Consequently, one of the main concerns was the effect of Bauxsol™ inclusion in concrete on its sulphate resistance, due to the high alumina content. Therefore, an investigation into the strength and sulphate resistance of cement mortar where Bauxsol™ was used as a partial sand replacement material at 0%, 5%, 10%, 15% and 20% by cement mass was conducted. Results of these investigations indicated that BauxsolTM may replace the natural sand up to 10% by cement mass, to improve the compressive strength of cement mortar without affecting the sulphate resistance. Similar investigations had shown that the Bauxsol™ may replace the natural sand up to 15% by cement mass without detrimentally affecting strength, modulus of elasticity and alkali-aggregate reactivity of the resultant concrete. Consequently, it is believed that Bauxsol™ use in concrete could provide an environmentally sustainable way of consuming large volumes of BRR.