Development of Eco-Friendly and High Performance Construction Materials and Technologies

Abstract

Because of global environmental concerns for concrete and waste materials and increased awareness of non-renewable natural resources, there is an urgent need to find ways to develop eco-friendly concretes. This is reflected in the large number of recent studies undertaken toward this end. However, the existing studies lack some of main parameters and points, such as the influence of the quality of recycled aggregates, influence of the full replacement of dry constituents with waste-based alternatives, influence of high performance graphene nanomaterials, and influence of the lateral confinement at the material level on the properties of concretes. This thesis contains a series of journal papers focused on the development of eco-friendly and high performance construction materials. In this research the behaviour of different types of concretes and mortars, including recycled aggregate concrete (RAC), geopolymer mortar, waste-based concrete and mortar, and graphene-based cement mortar, is studied. In addition, this thesis presents the behaviour of geopolymer concrete and steel fibre-reinforced concrete (SFRC) under active confinement and high-strength concrete (HSC) under shape memory alloy (SMA) confinement. The experimental study on time-dependent and long-term mechanical properties of RACs shows that high-strength RACs, prepared with full replacement of natural aggregates with recycled concrete aggregates having a high parent concrete strength (110 MPa), exhibit the properties similar to or better than those of companion natural aggregate concretes. Using gene expression programming (GEP) technique, new empirical models are developed to accurately predict mechanical properties of RACs. In addition, analytical studies on RACs reveal that multivariate adaptive regression splines (MARS), M5 model tree (M5Tree), and least squares support vector regression (LSSVR) models provide close predictions of mechanical properties of RACs by accurately capturing influences of key parameters. The experimental study on waste-based concrete reveals that concretes containing ground granulated blast furnace slag (GGBS) at up to 90% cement replacement exhibit nearly similar mechanical properties to the conventional concrete after 28 days of curing age. The experimental studies on geopolymer and waste-based mortars show that mortars with full replacement of sand with lead smelter slag (LSS) and glass sand (GS) and up to 80% replacement of cement with GGBS exhibit nearly similar mechanical properties to the conventional mortar. The study on the influence of graphene oxide (GO) dosage on physiochemical and mechanical properties of cement mortars shows considerable dosage dependence with the optimum dosage of 0.1% GO (by weight of cement) that increases 28-day tensile and compressive strength of the composite by 37.5% and 77.7%, respectively. The study on the influence of oxygen functional groups of graphene on the properties of cement mortars reveals that an addition of 0.1% reduced GO (rGO) prepared by 15 min reduction and 0.2% (wt%) hydrazine results in a maximum enhancement of 45.0% and 83.7% in the 28-day tensile and compressive strengths compared to the plain cement mortar, respectively. The experimental study on the behaviour of ambient- and oven-cured geopolymer concretes under active confinement reveals that oven-cured geopolymers exhibit a less ductile behaviour and lateral dilation than their ambient-cured counterparts. The experimental study on the compressive behaviour of SMA-confined HSCs shows that confinement of HSC by 9.5% prestrained SMA spirals leads to 23.6% higher peak axial stress and 346% higher corresponding axial strain than that of unconfined HSC. The experimental study on the compressive behaviour of actively confined SFRC reveals that an increase in the steel fibre volume fraction leads to an increase in ductility of SFRCs. A finite element (FE) model is also developed to accurately predict the compressive behaviour of fibre-reinforced polymer (FRP)-confined SFRCs. The promising findings of this research point to the possibility of the development of eco-friendly and high performance composite members for structural applications in the construction industry.