Bond stress between reinforcement bars and fly ash-based geopolymer concrete

Abstract

Geopolymer concrete is an innovative construction material that utilises industrial by-product materials, such as fly ash and slags to form a cement replacement for concrete manufacture. In order to simulate the behaviour of all types of reinforced concrete at all load levels, an understanding of the bond between the reinforcement and the concrete is required. This study involves 102 pullout test specimens with bar diameters of 12 to 16mm, concrete cover-to-diameter (Cc/db) ratios of 2, 3, 5.8 and 7.8, compressive strength of 33, 38 and 43MPa and a reinforcement corrosion level ranging from 0 to 85% in mass loss. The results show that the bond between the reinforcement and the geopolymer concrete is stronger than the bond that exists between the reinforcement and ordinary Portland cement (OPC)-based concrete. Hence, existing models for OPC can be used as a lower-bounds estimate for analysis and design. Alternatively, new predictive models for the local bond properties and the bond strength variation with corrosion are presented for geopolymer concrete. The results also show that the influence of the Cc/db ratio on the bond strength reduces as the Cc/db ratio increases, while the influence of the compressive strength on the bond strength remains virtual. This is because increasing the compressive strength leads to an increase in the bond strength.