Effect of temperature on bond characteristics of geopolymer concrete

This paper presents experimental results on the bond behavior between geopolymer concrete and rebar. Pull-out tests on geopolymer concrete specimens embedded with plain and ribbed rebars were carried out at ambient temperature and after exposure to 100, 300, 500 and 700 °C. Two batches of geopolymer concrete with compressive strength of 48 and 64 MPa respectively, and five rebar diameters (of 10, 12, 14, 18 and 25 mm) were used for preparing the test specimens. Comparative benchmark tests were also conducted on ordinary Portland cement (OPC) concrete specimens. Results from these tests show that geopolymer concrete exhibits insignificant reduction in bond strength till exposure to 300 °C, but undergoes significant degradation beyond 300 °C. Data from the tests indicate that rate of bond strength degradation in geopolymer concrete is close to that of splitting tensile strength, but higher than that of compressive strength. Also, results infer that geopolymer concrete exhibits similar or better bond properties than OPC concrete, both at ambient temperature and after exposure to elevated temperatures. Thus geopolymer concrete can be a practical alternative to OPC concrete in reinforced concrete structures when fire resistance is one of the main design considerations.