Cementitious Composites of Pulverized Fly Ash and Blast Furnace Slag Activated by Sodium Silicate: Effect of Na2O Concentration and Modulus
J.I. Escalante-García; K. Campos-Venegas; A. Gorokhovsky; A.F. Fuentes. Cementitious Composites of Pulverized Fly Ash and Blast Furnace Slag Activated by Sodium Silicate: Effect of Na2O Concentration and Modulus. Advances in Applied Ceramics (ISSN: 1743-6753). 2006, Vol. 105, p. 201-2006.
Pastes of pulverised fly ash (PFA) and blast furnace slag (BFS) in proportions of 100–0, 75–25,
50–50, 25–75 and 0–100 (wt-%) were chemically activated using sodium silicate with modulus
(SiO2/Na2O) of 0, 0.75, 1, 1.5 and 2; the %Na2O was added at 4, 6 and 8% relative to the binder
weight. The pastes were cured for 24 h at 75uC and then 28 days at 20uC. For 100%PFA pastes,
the higher %Na2O, the better the strength; 4%Na2O was ineffective, whereas the highest strength of 25 MPa was reached using modulus 1. For 100%BFS pastes, the highest strengths were for 4%Na2O (80–85 MPa); the optimum modulus was 1.5. The addition of BFS to PFA rich pastes was favourable; for 50% blends, the strengths were between the above mentioned figures and the best modulus was 1–1.5 (45–48 MPa). The lower glass content of PFA (70%) compared with the BFS (.90%), together with the porous nature of the PFA, were considered to have reduced
the strength in PFA blends.
Pastes of pulverised fly ash (PFA) and blast furnace slag (BFS) in proportions of 100–0, 75–25,
50–50, 25–75 and 0–100 (wt-%) were chemically activated using sodium silicate with modulus
(SiO2/Na2O) of 0, 0.75, 1, 1.5 and 2; the %Na2O was added at 4, 6 and 8% relative to the binder
weight. The pastes were cured for 24 h at 75uC and then 28 days at 20uC. For 100%PFA pastes,
the higher %Na2O, the better the strength; 4%Na2O was ineffective, whereas the highest strength of 25 MPa was reached using modulus 1. For 100%BFS pastes, the highest strengths were for 4%Na2O (80–85 MPa); the optimum modulus was 1.5. The addition of BFS to PFA rich pastes was favourable; for 50% blends, the strengths were between the above mentioned figures and the best modulus was 1–1.5 (45–48 MPa). The lower glass content of PFA (70%) compared with the BFS (.90%), together with the porous nature of the PFA, were considered to have reduced
the strength in PFA blends.