An investigation into the development of high performance geopolymer concrete

Abstract

This thesis investigates the manufacture and material properties of some high performance geopolymer concrete. In particular the following is studied: design of high strength geopolymer concrete mix, structural performance of steel fibre reinforced geopolymer concrete and properties and application of lightweight geopolymer mortar. In the first part of this thesis, the development of high performance geopolymer mortars and concrete is presented. The mechanical properties of geopolymer mortars and concrete were measured and compressive strengths in excess of 80 MPa achieved. Based on the developmental studies, a framework for designing high performance geopolymer composites is proposed. In the second part, the material behaviour of steel fibre reinforced geopolymer composite is investigated. Discrete fibre pullout tests for Mode I and Mode II fracture and randomly distributed steel fibre tests on "dog-bone" shape specimens were undertaken to provide an insight of the fibre behaviour in geopolymer composite. A constitutive tensile model for steel fibre reinforced cementitious composite is then developed. The model was validated against data from the literature and within this study, and a good correlation was observed. This study further investigates the shear carrying capacity of steel fibre reinforced geopolymer concrete beams without stirrups. The results indicate that an increase in fibre volumetric content enhanced the shear capacity of the beam. A shear design model is developed based on the constitutive tensile model developed previously and shown to provide a good correlation against the test data. In the final part of this study, some high performance lightweight geopolymer mortars are developed. The mortar has a similar strength to that of a conventional concrete at one-half of its density! Following, lightweight geopolymer mortar beams reinforced with steel fibres and aramid fibre reinforced polymer reinforcement were manufactured and tested. The results show that steel fibres and aramid fibre reinforced polymer core increase the flexural stiffness and shear capacity of the beam. The shear design model was revised to account for the lower elastic modulus and larger strain capacity of the aramid fibre reinforced polymer reinforcement.