Abstract
It is a concerned question that the Portland cement concrete has poor performance in durability and stability. So, to develop a new binder to replace Portland cement has become an urgent issue. Alkali-activated cementing material (ACM), based on industrial waste residue (slag, fly ash and oil shale wastes), is an alternative to Portland cement which had better durability and high strength. However, the management of the water soluble alkali content, the inhibition of the long-term strength reduction and how to avoid the alkali-aggregate reaction are still under study because of the high content alkali in the ACM production. In this paper, we calculate and regulate the R/Al ratio when the content of Ca, Mg, Si and Al in raw materials appeared major difference. Then, theoretically analyze the influence of R/Al ratio on ACM product, and give explanation to the long-term strength reduction of the ACM. In our study, the R/Al control index shows two applicable formulas, (Na+K)/Al=1.0[when (Ca+Mg)/(Si-Na-Al) <0.8] and (Ca+Mg)/(Si-Na-K) =1.5[when (Ca+Mg)/(Si-Na-Al) =0.8]. The less the R/Al ratio in the formulas, the better the controllability of the water soluble alkali content and the stability of ACM product.
