Properties of concrete with recycled aggregates as coarse aggregate and as-received/surface-modified rubber particles as fine aggregate

This research demonstrates that rubber particle size affects concrete workability and water permeability to a greater extent than fresh density and strength. Concrete with rubber particles of larger size tends to have a higher workability and fresh density than that with smaller particle sizes. However, rubber aggregates with smaller or continuously graded particle sizes are shown to have higher strengths and water permeability resistance. Influence of recycled aggregate and rubber aggregate as part substitutions for natural aggregates on concrete compressive strength was investigated and four equations were proposed to predict compressive strength of the designed concrete. Besides, it is experimentally shown that silane coupling agent (SCA) has a positive effect on reducing the loss of strength of rubber concrete, especially when concrete is weak. This effect becomes more significant with the increase of mass fraction of SCA solution. Experiment results also show a better performance of concrete with SCA-treated rubber than with as-received or sodium hydroxide solution (NaOH)-treated rubber. A brief cost analysis suggests that this approach of surface modification is economically viable. Referring to a provided fatigue load spectrum and fatigue failure mechanism, this method is potentially to be used for rubber concrete in high-cycle fatigue condition