Characterization of alkali-activated binders using the maturity method

Abstract

Presently, the development of innovative eco-efficient cementitious materials is a widespread concern to assure the sustainability of the built environment. In this scope, alkali-activated binders, in which ordinary Portland cement (OPC) is totally or at least partially replaced by industrial by-products, is a promising solution. The alkaline activation of aluminosilicate materials, such as fly ash, consists in adding an alkaline solution to the latter and then submitting it to curing at prescribed temperature, thus promoting the transition from fresh to hardened state. Given the fact that the needed curing temperature is considerably high, presently these new bindings are mainly interesting for the precast industry. Moreover, due to the significant influence of this parameter, the maturity method, if applicable, can represent a most valuable tool, since it allows monitoring and forecast the compressive strength evolution as a function of time and temperature, according to Arrhenius equation.The study herein described aimed at applying the maturity method to alkali-activated binders and at establishing the strength-maturity relationship through laboratorial tests. First, different mixtures of alkali-activated mortars and a selected alkali activated concrete mixture were produced, varying the type and concentration of the alkaline activator. The influence of OPC as addition was also studied. Afterwards, the maturity method was applied to the production of precast alkali activated concrete façade panels. Results are presented and discussed and most relevant conclusions are drawn. It was proved that the maturity method can be used for monitoring both alkali activated mortars (AAM) and alkali activated concrete (AAC).