Experimental study on mechanical and waterproof performance of lightweight foamed concrete mixed with crumb rubber

•The crumb rubber content of 3% can improve the waterproof performance of foamed concrete.•The water absorption and compressive strength of foamed concrete are closely related to each other.•Foam content is the prime factor affecting the performance of foamed concrete.•Micro-characterization was used to verify the effect of crumb rubber on the microstructure of paste. This paper represented a lightweight foamed concrete prepared from the raw materials included a self-made compound foaming agent, cement, fly ash, waste crumb rubber, etc. The effects of foam content, crumb rubber content, fly ash content and water/binder ratio on the physical, mechanical and waterproof properties were studied by the single-factor and orthogonal tests. The main parameter that affect the mechanical and waterproof performance of foamed concrete was determined. In addition, the microscopic mechanism performance of foamed concrete was studied by means of scanning electron microscopy (SEM). This study found that the small amount (3 wt%) of crumb rubber can improve the waterproof performance of foamed concrete, and the foam content is the prime factor affecting the performance of foamed concrete. Moreover, there is a strong correlation between the permeability and mechanical properties of foamed concrete.