Determination and enhancement of mechanical and thermo-physical behaviour of crumb rubber-modified structural concrete

This study aims are to i) understand and improve the bonding characteristics between crumb rubber and cement paste, and ii) scale-up the use of the material from lab to full-sized reinforced sections. Firstly a parametric investigation was conducted to determine the effect of crumb rubber replacement on the fresh, mechanical and thermo-physical properties of Plain Rubberised Concrete (PRC) and Self-compacting Rubberised Concrete (SCRC) at different w/c ratios. Secondly, the relative effects of different pre-coating/ treating methodologies were evaluated in terms of ITZ porosity, interfacial bonding, and mix air entrapment. These micro structural characteristics were compared to the resultant macro- scale mechanical and dynamic properties in order to evaluate the effectiveness of each treatment method. Thirdly, the large-scale serviceability of steel-reinforced PRC and SCRC was experimentally measured and assessed in terms of mechanical structural behaviour, steel reinforcement bond-slip strength, and material durability including chloride ion diffusion and water penetration. It was found that although crumb rubber incorporation decreases the workability/flowability, compactible mixes could be achieved even with zero-slump. Mortar pre-coating was found to be the most effective surface treatment method in improving both the mechanical behaviour and toughness of PRC and SCRC. It caused an elongation in the micro-crack path length at the rubber/ cement interface due to roughening of the surface morphology, leading to increased fracture energy dissipation! stress relaxation. Crumb rubber incorporation led to unusual thermo-physical properties as thermal conductivity decreased whilst volumetric heat capacity increased, with a pronounced moisture-dependency caused by air entrapment. Consequently, the concrete elements were found to store more heat energy, whilst increasing their resistance to heat exchange with the ambient environment. Interestingly, incorporating crumb rubber offers a significant reduction in interior air temperature fluctuations, which is important in terms of building thermal efficiency and comfort. It was found that both PRC and SCRC could be promising structural materials, with preference to SRCR, to be used for casting indoor-use structural members, especially for domestic buildings.EThOS - Electronic Theses Online ServiceGBUnited Kingdo