Shear Behaviour of Hybrid Fibre Reinforced Geopolymer Concrete Beams

Abstract

Concrete is the most common material for construction. The demand for concrete as a construction material leads to the increase of demand for Portland cement. Concrete is known as a significant contributor to the emission of greenhouse gases. The cement industry is the second largest producer of the greenhouse gas. The environmental problems caused by cement production can be reduced by finding an alternate material. One of potential material to substitute for conventional concrete is geopolymer concrete. Geopolymer concrete is an inorganic alumino-silicate polymer synthesized from predominantly silicon, aluminium and by product materials such as fly ash, GGBS (ground granulated blast furnace slag). Geopolymer concrete does not contain cement. Hybrid fibres were used in this study. Hybrid fibre is the combination of steel fibre and basalt fibre with different volume fractions. When these fibres are added to this special concrete it improves the ductile behaviour and energy absorption capacity. This is due to the property of steel and basalt fibre to bridge the crack development inside the concrete. The main objective of the study is to look into the shear behaviour of hybrid fibre reinforced geopolymer concrete beams.

Test specimens of 1200×150×100 mm size were used for the study. 20-30% of Fly ash by the mass was replaced by GGBS. The variable used were percentage of steel fibre volume fraction viz. 0.0%, 0.5%, and 1%, and basalt fibre volume fraction viz. 0.0%, 0.15%,and 0.3%. The concentration of sodium hydroxide was 12Molar and 14 Molar in geopolymer concrete. For curing, temperature was fixed as 60⁰ C for 24 hours. The geopolymer specimens were cured by using steam curing chamber. The specimens were cured after the rest period of three days. A trail and error process was used to obtain proper mixture proportion for geopoymer concrete. The specimens were tested after the age of 7 days. The obtained results of Fly ash and GGBS -based hybrid fibre geopolymer concrete (F&GHGPC) specimens were compared with the only Fly ash-based hybrid fibre geopolymer concrete (FHGPC) specimens.

Test results shows that first crack load, ultimate load, energy absorption capacity, experimental shear strength and ductile characteristic of F&GHGPC geopolymer concrete specimens were higher than the FHGPC geopolymer concrete specimens.