To eliminate the unfavorable effect of the accumulation of end-of-life car tires on the environment, many studies have been conducted to recycle those tires in concrete as a partial or full replacement of its natural aggregates. However, the produced rubberized concrete suffers from low compressive strength due to low adhesion at the rubber/cement interface. Pre-treating of rubber surfaces before use in concrete is the most effective way to overcome this adverse effect on the concrete strength. Several studies introduced different methods to enhance rubberized-concrete strength through pre-treating rubber particles, especially when using a high content of rubber in concrete. This study presents the results of experimental work on the effect of heat treatment on crumb-rubber–concrete mechanical performance. Rubber contents of 40%, 60% and 80% of sand volume were the variables in this study. Workability, density, compressive strength, and impact resistance were the measurements in this experimental work. The results showed that using saturated-surface dry (SSD) rubber can eliminate the adverse effect on concrete slump when using a high rubber volume or the heat-treated rubber. Using heat-treated rubber at 200 °C for 2 h as 40%, 60%, and 80% displayed compressive strength recoveries of 14.9%, 10.4% and 9.7%, respectively. Heat treatment of 40%, 60%, and 80% rubber contents increased the impact resistance for ultimate failure by 57%, 28%, and 7%, respectively, compared with those of the control mix. The thermal treatment enhanced the impact resistance at ultimate failure by 37%, 28%, and 15%, respectively, for mixes containing 40%, 60%, and 80% rubber contents compared with those of as-received rubber.