Minimum flexural reinforcement of fly ash and GGBS based geopolymer concrete members

Abstract

Geopolymer concrete is a relatively new binder material that can replace cement in concrete. Fly ash is activated in the presence of alkali activator (combination of alkali Silicate and alkali hydroxide) that binds the fine aggregate and coarse aggregate in geopolymer concrete. These concretes need temperature curing to the extent of 60 °C for about 24 h. The temperature curing to this extent is difficult in conventional construction practices. Many researchers have reported that fly ash and ground granulated blast furnace slag (GGBFS) based geopolymer concrete can be cured in the room temperature and can develop desired strength. With this advent, research in the direction of geopolymer concrete in respect of mechanical strength characteristics like tensile strength, compressive strength and modulus of elasticity, mix design and confinement aspects of geopolymer concrete, is increasing. This paper presents the behavioural aspects of reinforced geopolymer concrete members subjected to flexural loading. Three different proportions of geopolymer concrete with target 28-day compressive strength of 30 MPa, 45 MPa and 60 MPa were developed. The test results indicated that minimum flexural reinforcement is needed in geopolymer concrete beams to avoid brittle failure and controls the cracking. Minimum flexural reinforcement is needed to maintain the integrity of the reinforced concrete members even after the tensile resistance of concrete is exhausted. Thus, an expression for the minimum flexural reinforcement needed in beams is proposed.