The Mechanism of Alkali-silica Reaction in Alkali Activated Slag Cement Concretes Using Active Aggregates and its Control by Al-ion Based Admixtures

The problem of the alkali-silica reaction is one of the top problems in the modern concrete science. The appearance of such reaction in the hardened cement and concrete stone results in the crack appearance and destruction of material. The present study discloses the results of a study on structure formation processes in the interfacial transition zone “cement stone - aggregate” of the alkali-activated cement concretes. The results indicate the influence of Al2O3 content in the cement composition on alkali-silica reaction gain in alkali activated materials. Introduction of additional source of Al into the system leads to the constructive gain of the alkali-silica reaction process in the system. This constructive effect is caused by incorporating the corrosion products into alkaline alumina silicate compounds, thus retarding the internal corrosion of the concrete and providing the higher durability even in case of alkali-activated cements and alkali-susceptible aggregates with relatively high alkali content. Also there are shown variations of the pH values in different alkali activated cement systems depending from type of alkaline component and additional source of alumina.