Effect of Binder Content and Solution/Binder Ratio on Alkali-Activated Slag Concrete Activated with Neutral Grade Water Glass

Use of alkali-activated slag concrete (AASC) in replacing conventional concrete has become an environmentally friendly alternative construction technique. Alkali activation of fly ash and ground granulated blast furnace slag (GGBFS) using NaOH and Na₂SiO₃ is well documented in the literature. GGBFS activated with alkaline solution produces less workable concrete with quick setting behaviour. In this investigation, GGBFS was used for preparing AASC using sodium silicate solution (neutral grade) with silica modulus (M_s) of 2.92 to assess the ability of this solution in arresting the quick setting aspect of GGBFS; setting time studies have been conducted to check the viability. The results indicated that neutral grade sodium silicate solution increases the setting time and hence can be used in the preparation of AASC. An experimental program was carried out to evaluate the workability and strength of concrete for different solution/binder ratios (0.55, 0.6, 0.65, 0.7, 0.75 and 0.8) and different binder quantities (400, 500 and 600 kg/m³). Results obtained indicated that the range of compressive strength for these binder contents varied from 60 to 80 MPa. Workability of these mixes ranged from 80 to 110 mm. The results of the present investigation show that alkali-activated concretes can be activated with neutral grade sodium silicate solution under ambient curing, which is more suitable for application in construction industry.