Studies on flexural behaviour of reinforced geopolymer concrete beams with lightweight aggregates

Portland cement (PC) is widely used as binder material for concrete in a wide variety of constructions. However, this cement is proving to be ecologically hazardous material due to its inherent high internal energy content besides occurrence of emission of large quantities of carbon dioxide during its production. Therefore, there has been intense search for alternative binder material. Geopolymer is a type of binder that can be obtained by activating silicon dioxide and aluminium oxide present in industrial wastes such as blast furnace slag powder and fly ash, to form inorganic polymer binder system. This paper describes experimental investigation on flexural behaviour of reinforced geopolymer concrete (GPC) incorporating synthetic light weight aggregate (sintered). GPC mixes with sintered FA aggregate were designed following the guidelines laid down by ACI committee 211.2 -1998. The compressive strength ranged from 23 to 30 MPa. Four sets of reinforced GPC beams (two specimens each) having different mix composition (25 and 50% FA in the binder system) incorporating fly ash aggregate and having reinforcement equal to 1.33 and 2.17 percentage of balanced section were tested for flexural behaviour under two point loading up to failure. The deflection, cracking load, failure load, and crack pattern at failure load were recorded. The ultimate load capacities ranged from 53.3 to 64.85 kN for 100% reinforcement and 24 to 32.6 kN for 50% reinforcement and about 10% difference was observed due to mix variations. The ratio of experimental to theoretical moment capacity ranged from 0.92 to 1.0. The ultimate moment carrying capacity of beams tested was calculated from the first principles using strain compatibility methods and provisions of IS: 456–2000.