Mechanical, thermal and structural investigations of one-part geopolymer concrete

Abstract

Geopolymeric materials have recently attracted increasing research due to the need to reduce global CO2 emission as well as the growing desire for utilisation of waste and by-products in construction materials. Furthermore, geopolymers are well-known for their excellent behaviour in terms of fire performance which is a matter of great concern in structural design. This thesis presents a study on the development of one part geopolymer concrete (OGC) and hybrid OPC-geopolymer concrete (HGC) mixes and their behaviour at both ambient and elevated temperatures and their application in reinforced concrete columns. The intention for development of one part geopolymer concrete is to improve the commercial viability of geopolymers in building industry. The previous studies mainly emphasized on the investigation of geopolymeric material properties at ambient and elevated temperatures and only a few experimental studies have been devoted to explore the fire performance of reinforced geopolymer concrete members. Thus, this research aims to address this research gaps. In this study, material properties such as slump, density, compressive strength, modulus of elasticity, tensile strength and stress-strain behaviour of OGC and HGC mixes are compared with those of reference Ordinary Portland Cement concrete (CC) mix. Furthermore, the hot compressive strength and thermal properties of the mentioned mixes were measured. Microstructural characterisation was also performed on OGC, HGC and CC samples using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) to provide better insight into microstructure of materials with distinct properties. Two kinds of structural tests were performed on the reinforced geopolymer concrete columns. Two reinforced columns made of OGC and HGC were loaded axially at ambient temperature. The effects of concrete type on the failure modes, development of axial and lateral strains and ultimate load capacity of reinforced columns are examined. In addition, the test results are compared with finite element (FE) analysis for HGC and OGC compared with CC columns. Another ten columns including 3 OGC, 3 HGC and 4 CC columns were tested in fire in which each column was exposed to a given constant load level at ambient temperature, then heated until the column failed. The effects of concrete type (OGC, HGC and CC) and load level (0.3- 0.45 of ultimate) were studied in the test program. The experimental results demonstrated that the use of geopolymer concrete has the potential to enhance the fire resistance of reinforced columns. Furthermore, the achieved data from the experiments such as temperature development, axial and lateral deformation, fire resistance time and failure modes have improved the understanding of the performance of reinforced OGC and HGC columns subjected to fire condition. The test data was also used to verify the proposed finite element (FE) modelling approach in which a finite element model, using ABAQUS commercial software, simulates the behaviour of reinforced OGC, HGC and CC columns. A reasonable agreement was observed by comparing the results obtained from experiments and FE analyses. This research confirms the practicality of employing sustainable one-part geopolymer concrete in structural members and its benefits to improve the thermal insulation or fire performance of reinforced concrete members.

Date of Award	2019
Original language	English