Low heat high performance concrete for glass fiber reinforced polymer reinforcement
Low heat high performance concrete (LHHPC) is concrete with low cement content, a consequent low heat of hydration and a relatively low alkalinity. The research program described in this thesis was designed to study LHHPC in terms of mechanical properties, structural behaviour and durability under freezing and thawing. The durability of reinforcement (steel and GFRP) in the low alkaline environment of LHHPC is also investigated. Use of glass fiber reinforced polymer (GFRP) as a replacement for conventional steel reinforcement has increased rapidly for the last ten years. The non-corrosive characteristics and high strength-to-weight ratio of GFRP might significantly increase the service life of structures. However, the chemical composition of glass is known to be unstable in the high alkaline environment of concrete pore water. The low alkalinity of LHHPC might have beneficial effects in the use of GFRP as reinforcement for this new concrete. The low alkalinity might, on the other hand accelerate corrosion of steel reinforcement. Over sixty standard size cylinders were cast and tested to study the mechanical properties of LHHPC and the results indicate compressive strengths of over 70 MPa at 28 days for LHHPC. Eight beams of rectangular section were cast and tested to study the behaviour of the reinforced LHHPC. The results indicate a higher strength and ductility for LHHPC than the control normal conventional concrete (NCC) beams. The results from the air-entrained concrete indicate that LHHPC has an excellent durability factor against freezing and thawing while maintaining high compressive strengths for an air content of 4.6 percent. The tensile strength of GFRP bars embedded in both LHHPC and NCC, at 60$\sp\circ$C, are identical after one month.