Research on physical and mechanical properties of alkaline-modified self-compacting rubber concrete

This paper presents an alkaline-modified method to enhance the performance of self-compacting rubber concrete (SCRC). Physical and mechanical properties of modified SCRC are analyzed. The results show that after limestone immersion, improved the surface properties of the rubber particles and attached alkaline-excited Ca(OH)₂, which induced an earlier volcanic ash reaction in the cementitious and auxiliary cementitious materials. This resulted in the generation of hydrated calcium-silica hydrate (CSH) between the rubber particle and the matrix, enhancing the adhesion and interfacial strength between them. And the generation of hydrated CSH fill the pores, resulting in a reduction of the SCRC connecting pores. The modified SCRC density increases and water absorption decreases. The rate of charge exchange slows down in a chloride ion environment. The resistivity of the modified SCRC increased by approximately 20 %. When the rubber content is 5 %, 10 % and 15 %, the compressive strength of the modified SCRC is enhanced by 6.9 %, 8.1 % and 11.7 %, and the flexural tensile strength by 9.0 %, 16.8 % and 23.1 % respectively. The modulus of elasticity is enhanced by 9.8 %, 9.2 % and 13.5 %, and threshold stress levels at the point of elasticity are improved by 10.5 %, 4.5 % and 6.1 % respectively. During compression, the fracture activity and the energy released reduced. And the fatigue life is significantly increased for the same compression fatigue strength. However, after modification, the pre-peak compressive toughness index decreased by 24.1 %, 24.6 % and 9.2 %, and the pre-peak bending and tensile toughness index decreased by 34.4 %, 15.4 % and 25.8 %, respectively. Consequently, it can be found that the modified SCRC durability and strength are improved, but the SCR toughness is reduced.