Assessment of pozzolanic/hydraulic reactivity of vitreous calcium aluminosilicate (VCAS)

Abstract

The aim of this paper is to assess the possibility of using vitreous calcium aluminosilicate (VCAS) as a supplementary cementitious material in the production of Portland cement mortars. The calcium hydroxide consumption by VCAS is assessed by two different methods: firstly, a classical method based on thermogravimetric analysis (TGA) and, secondly, pH and electrical conductivity measurements of calcium hydroxide/VCAS suspensions with excess calcium hydroxide. Evidence of pozzolanic reactivity of VCAS is revealed in hydrated lime pastes, and low reactivity was observed in aqueous suspensions. The reactivity of VCAS is also assessed by means of TGA of VCAS/OPC pastes and by means of the mechanical strength development of Portland cement mortars, with VCAS replacement percentages in the range of 10-30%. The results obtained show that pozzolanic and hydraulic reactions take place in OPC systems. VCAS can be used as a supplementary cementitious material by replacing OPC at levels of 10-30% by mass.