This paper reports on the development of a new type of low cost artificial aggregates based on granulated reactive silica (AAGS) for application in lightweight concrete. The functional principle of AAGS is based on the formation of polysilicate solutions under heat treatment (up to 80 °C) and migration of these solutions into the porous space of concrete under the thermal gradients, resulting in strengthening of inter-porous space. Developed AAGSs are based on low cost local raw materials, which may contain different amounts of amorphous silica. The activity coefficient (AC) and amorphous silica content are used to evaluate the performance of raw materials by suggested accelerated method.
Silica components with different genesis are investigated and ranked according to their AC. It is found out that chemogenic and biogenic siliceous rocks with a low degree of diagenetic transformations, which are mostly represented by CT-opals (a low-temperature nanoscale modification of tridymite and crystobalite, such as diatomite, tripoli and opoka) are the most highly active raw materials for AAGS. All tested siliceous materials including natural and artificial components are divided into three groups: highly active (with AC of 51–100%), active (with AC of 21–50 %) and low-active (with AC of 5–20 %). Based on theoretical and experimental studies, the requirements for AAGS raw materials are developed.