Bond Behavior of Reinforcing Steel Bar and Geopolymer Concrete

Abstract

The study investigated the bond behavior of reinforcing bar and geopolymer concrete as a function of rebar diameter, embedment length, concrete cover and compressive strength. The effect of rebar surface (plain and ribbed) and coating on bond performance of geopolymer concrete also was studied. The pull-out behavior under monotonic loading, ultimate bond stress, slip, and load at failure were evaluated. Embedment length to bar diameter (L/ϕ) ratio was optimized and found to be 5. The L/ϕ ratio of 5 was used to study the pull-out behavior. The specimens were reinforced with helixes to avoid splitting of concrete before attaining the ultimate strength. The ultimate bond stress of ribbed bars was 234% higher than that of plain bars. The rebars were coated with fusion-bonded epoxy and zinc alum spray coating to study the effect of coating on bond behavior. The coated bars slipped more than uncoated bars due to the reduction in the coefficient of friction. The bond performance of geopolymer concrete was effective compared with that of the control cement concrete. The bond strength of geopolymer concrete exposed to elevated temperatures increased with an increase of temperature up to 400°C and then decreased. The decrease in bond strength was about 69% at 800°C. The accelerated corrosion test was carried out using the impressed voltage method at 65 V in 5% saturated sodium chloride (NaCl) solution. It was observed that increasing corrosion levels from 0.2%–0.69% decreased the ultimate bond strength from 16 to 9.5 MPa.