High-ductility strain-hardening cementitious composites at subzero temperatures by recycling waste crumb rubber: Air entrainment and flaw distribution optimization

The ductility of strain-hardening cementitious composites (SHCC) is known to degrade when exposed to subzero temperatures, compromising the resilience and sustainability of civil infrastructures. To address this issue, a preliminary attempt is conducted to explore the potential of employing an air-entraining agent (AEA) or waste crumb rubber to weaken the SHCC matrix and enhance the ductility of SHCC. The effects of incorporating AEA and crumb rubber (fine crumb rubber and coarse crumb rubber, referred to as FR and CR) on the fresh, physical, and mechanical properties of SHCC at various subzero temperatures are thoroughly examined and compared. The experimental results demonstrate that the air-entraining effect of incorporating waste crumb rubbers is similar to that of AEA, resulting in an approximate 9 % air content within the SHCC. Furthermore, the incorporation of crumb rubber significantly improves both the tensile strength and ductility of SHCC at subzero temperatures. Remarkably, the CR-modified SHCC exhibits a tensile strength of up to 10.50 MPa and a strain capacity of 4.30 % at −60 °C. The addition of crumb rubbers introduces uniformly distributed spherical bubbles, optimizing the size and distribution of flaws within the SHCC matrix and enhancing the strain potential of SHCC. This study proposes a cost-effective and environmentally friendly SHCC formulation by recycling waste crumb rubber and proposes a promising approach for developing high-ductility and sustainable SHCC in cold regions. By leveraging the potential of solid waste, this research contributes to the advancement of durable and resilient infrastructure solutions.