Abstract

Portland cements (PC) and blended PCs are the most commonly used binders in Stabilisation/Solidification (S/S) applications. However, such systems have found limited suitability with organic contaminants and the high alkalinity associated with PC militates against the soil microbes and hence, the natural attenuation of the organics. Furthermore, the production of PC is not only an extremely resource and energy intensive process but also has significant negative environmental impacts. This research has thus been focused on addressing these issues by the development and application of two novel binders; viz. low pH magnesia phosphate cement and reactive magnesia cement respectively. A range of binder formulations based on those two cements were investigated in the S/S treatment of model contaminated soils.

This study was successful in formulating magnesia phosphate cement mixes which could have the potential to facilitate biodegradation of organic contaminants in parallel to the S/S of heavy metals. Not only did those mixes develop low-pH ranges favourable to soil microbes but also more effectively immobilised heavy metals than PC-based binders. The reactive magnesia cements also displayed an advantage over PC-based binders especially in terms heavy metal immobilisation highlighting their potential as a sustainable alternative to PC in S/S applications. This presentation will mainly focus on the variables involved in magnesia phosphate cement formulations and heavy metals related S/S performance of the two binder mixes. These aspects will be elucidated through a range of physical, mechanical, chemical and microstructural properties.