Studies on adhesive bond strength of steel reinforcing bars with fly ash based-ambient cured geopolymer concrete

Geopolymers are inorganic amorphous alumina-silicate binders formed by Alkali Activation of Geoploymer Source of Materials. Concrete made using Geopolymer binders are excellent alternative to Ordinary Portland Cement(OPC) concretes from strength, durability and ecological considerations. Considerable investigations have been carried out on the usage of Geopolymer Concrete(GPC) for the use as Concrete suitable for construction. The investigation of the bond behaviour of reinforcing bars used in the GPC concrete as a new binding material is very important. Studies on reinforced GPC members are limited especially on bond behaviour of reinforcing bars with GPC concrete. The bond stress transfer between steel and concrete depends on chemical adhesion, sliding friction and mechanical interactions. This paper describes the “adhesive bond behavior” of machine polished 12,16 and 20mm diameter bars embedded in Geopolymer concretes. The specimens were investigated using the pull-out tests as per Indian Standard Code of IS:2770, the adhesive bond stresses and slips were found out and compared with bond stress values due to adhesion of OPC concrete of similar compressive strengths levels. The Geopolymer concretes possess higher adhesive bond strength compared to the OPC cement concretes. The adhesive bond stress increased with increase in compressive strength of GPC. Differing from the adhesive bond stress-slip curve of OPC concrete, maximum stress plateau is observed in the adhesive bond stress-slip curve of GPC. GPC with compressive strength 39MPa exhibit a strain softening stage in bond transfer after the peak bond stress, whereas GPC with 59MPa compressive strength exhibit a strain hardening stage in bond stress-slip curve. Maximum adhesive bond stress of GPC mixes are 30 to 80% higher than the average maximum adhesive bond stress of OPC concretes.