The crumb rubber cement mortar is prepared by the crumb rubber aggregates in 60 mesh which are modified by 1% polyvinyl alcohol (PVA) solution. Some mechanical properties of cement mortar with different crumb rubber aggregate amounts are researched including compressive strength, flexural strength, the ratio of compressive strength to flexural strength, impact resistance, and dry contraction percentage. In our tests, we consider six kinds of the rubber contents, 0%, 7.5%, 15%, 19%, 22.5%, and 30%, respectively. The optimal mixing amount of crumb rubber is determined by measuring three indices, the ratio of compressive strength to flexural strength, impact resistance, and dry contraction percentage. It is shown by test that the ratio of compressive strength to flexural strength is the smallest when the mixing amount of rubber is 19%; meanwhile high impact resistance and rational drying shrinkage are observed. The optimal mixing amount of the rubber particles is 19% determined by this test.

In the present study, the impact resistance of rubber concrete at low temperatures (−30°C) was examined. The initial and ultimate crack impact times and the ductility indexes were evaluated. This study’s specimens were prepared by adding two different sizes of rubber particles (20 mesh and 50 mesh) in different ratios (0%, 5%, 10%, 15%, and 20%) at both 25°C and −30°C. The concrete specimens were evaluated using a drop hammer weight test method. The results showed that the initial and ultimate crack impact times and ductility indexes of the rubber concrete specimens had decreased at −30°C. Also, the decrease amplitudes were determined to be lower than those of the reference concrete specimens. Consideration was given in this study to the large variations in the impact values, and a two-parameter Weibull distribution method was adopted in order to analyze the obtained experimental data. The results had demonstrated that the impact times of the rubber concrete specimens could be described using the two-parameter Weibull distribution method results.

The disposal of waste rubber has attracted a great deal attention because of the serious environmental problems caused by the growing overuse of rubber products. A feasible alternative that has caused concern is the incorporation of recycled materials into cementitious composites in civil construction. The performance of such materials at ambient temperature has been fully reported in the literature. However, limited data is available on the behaviors of crumb rubber concrete (CRC) at low temperature. This article studies the features of the cubic compressive strength, splitting tensile strength, and tension-compression ratio of CRC specimens at ambient temperature of 20°C and low temperatures of 0°C and −30°C. By experimental tests, the effects of the rubber content and water-binder ratio on the mechanical properties were analyzed. It was shown that the compressive strength and splitting tensile strength of CRC are significantly enhanced with the decrease of temperature, which is similar to the case of conventional concrete, but the trend of strength growth at low temperatures differs from the trend of strength growth at the ambient temperature of 20°C. The tension-compression ratio of CRC increases gradually with the temperature decrement, indicating that the CRC still exhibits excellent ductility at low temperature. As comparative analysis, it is known that when the water-binder ratio is 0.40, and the volume replacement rate of rubber substituted for fine aggregate is 20 %, the CRC presents optimal mechanical properties at a low temperature of −30°C. The assessment of the strengths of CRC at low temperatures may support the necessary experimental data for the application of CRC at low temperatures.

The uniaxial compression tests were carried out on the prism specimens of plastic fiber–reinforced rubber concrete with three water-binder ratios and six kinds of plastic fiber contents, and the stress-strain curves were monitored. According to the uniaxial compression test, the change rule of the rising and falling of the stress-strain curve and the change of the peak strain were analyzed. Based on the features of the stress-strain curves, the uniaxial compressive constitutive model for plastic fiber–reinforced rubber concrete is proposed containing constitutive parameters A and B. By using the regressive analysis with the least squares principle method for the experimental data, we propose the mathematical expression of the constitutive parameters “a” and “b” of the rubber concrete, which demonstrates the specific relationship between the constitutive parameters A and B. Thus, the constitutive equation for plastic fiber–reinforced rubber concrete was obtained.