Mechanical and deformational properties, and shrinkage cracking behaviour of lightweight concretes

Abstract

This thesis studies theoretically and experimentally the role of constituent materials of different lightweight concrete (LWC) on the mechanical and deformational properties, and shrinkage cracking behaviour of both foamed concrete with and without aggregate and lightweight aggregate concrete (LWAC). The main constituent materials of LWC considered in the study include filler volume (air and aggregate), filler type or density, fibers, and mineral admixtures. The first part of the study focused on understanding the role of the constituents on mechanical properties such as compressive strength, tensile strength, modulus of elasticity, fracture toughness and stress-strain behaviour. Particular emphasis has been placed to study the effect of w/c ratio on air-void system of foamed concrete and their effects on mechanical properties through experimental and numerical analysis. The second part of the study focused on understanding the role of the constituents on deformational properties such as drying shrinkage and creep of concrete. Since foamed concrete of higher strengths are relatively new, autogenous shrinkage of the foamed concrete was compared with that of LWAC and normal weight concrete (NWC), and the variation was analysed. Different prediction models found in literatures were used to verify the shrinkage and creep of foamed concrete with and without aggregates. Finally, shrinkage cracking behaviour of LWCs was evaluated through experimental and theoretical analysis. The restrained ring test was adopted to evaluate the cracking potential of LWC with and without aggregates. The mechanical and deformational properties, and shrinkage cracking behaviour of LWC with and without aggregate have been verified and discussed in relation to NWC. The results of these tests are presented and discussed, and the implications on the selection of constituent materials, and their influence on potential risk of shrinkage cracking have been addressed. Both experimental and theoretical analysis collectively shows that it is essential to control the shrinkage rates of concrete to control the shrinkage cracking problem. The shrinkage cracking behaviour of foamed concrete with and without aggregates in comparison with LWAC has been evaluated. The key parameters and constituents needed to control or mitigate the shrinkage cracking of LWC for the given geometry have been suggested.