Flexural behaviour of geopolymer concrete beams exposed to elevated temperatures

Flexural behaviour of fly ash based geopolymer concrete beams exposed to elevated temperatures (200 °C, 400 °C, 600 °C and 800 °C) has been discussed in this paper. Beams of size 150 mm (W) × 200 mm (D) × 1100 mm (L) were cast with 0.52% reinforcing steel. Cover to the reinforcement has been varied (20 mm, 30 mm and 40 mm) and the geopolymer concrete used had a cube compressive strength of 57 MPa. The deformation characteristics, moment-curvature relationship and cracking behaviour were observed. It could be concluded that, the deformation characteristics of reinforced geopolymer concrete beams at ambient temperature is similar to that of the reinforced cement concrete beams and could be predicted using strain compatibility approach. However, when they are exposed to elevated temperatures, the strain compatibility approach underestimates the deformation behaviour of reinforced geopolymer concrete beams. Further, ductility of the geopolymer concrete beams reduces rapidly with the increase in exposure temperature. Approximate equation has been proposed to predict the service load crack width of geopolymer concrete beams after exposure to elevated temperatures.