Reaction kinetics, microstructure and strength behavior of alkali activated silico-manganese (SiMn) slag - Fly ash blends

Two industrial waste namely air cooled silico-manganese (SiMn) slag and fly ash has been used synergistically to develop alkali activated cement at ambient temperature. Isothermal conduction calorimetric studies (ICC) revealed that addition of SiMn slag resulted in an increase in reactivity. A new hump in ICC after 1.4 h of reaction is appeared in blends rich with SiMn slag, which is due to the formation of primary C-(A)-S-H gel. The shift in band corresponding to Si-O-Si/AI at similar to 1000 cm(-1) towards lower frequency in Fourier transform infrared spectrum with slag inclusion suggest the structural reorganizations and formation of a new calcium rich gel. The main reaction product is detected as (N) A -S-H and C-(A)-S-H (where, N = Na2O, A = Al(2)o(3), C = CaO, S = SiO2, H = H2O) based heterogeneous hydrated gel with varying Si/Al, and Na/Ca ratios. Both Si/Al ratio (obtained in EDX analysis) of gel phases and compressive strength increases with slag introduction. The improvement of mechanical strength with increasing slag is associated with more reactive CaO content of the slag, and co-existence of C-A-S -H and N-(C)-A-S-H type gel in the reacted matrix. (C) 2017 Elsevier Ltd. All rights reserved.