Alkali-activated cements - Opportunities and challenges

Alkali-activated cements as discussed here are those with compositions fall ing in the Me2O-MeO-Me2O3-SiO2-H2O system. This paper reviews their history of development and discusses their present status. Currently, there are ma jor opportunities for such cements based upon (a) substantial knowledge of properties and mechanisms; (b) good track record of field performance in va rious applications and; (c) future orientation as environmentally friendly materials in accord with making use of substantial amounts of by-product an d waste materials, thereby consuming less energy and generating less waste. The equivalent performance to Portland cement materials is one target for these cements, but, in many cases, the properties of alkali-activated cemen ts actually are superior. It is important for assuring long-term durability to characterize more fully the complex solid phases, including determining the combined state of alkali in the solid hydration products, and of the r esidual soluble species in the pore fluids as a function of time. (C) 1999 Elsevier Science Ltd. All rights reserved.