# Mechanical Properties of Cement Concrete with Waste Rubber Powder
## 4 Conclusions  
This study used response surface methodology to design the mix proportion of waste rubber powder cement concrete. Subsequently, this study investigated the mechanical properties of waste rubber powder cement concrete using traditional mechanical property tests and impact resistance tests. It also explored its noise reduction performance through rubber ball impact and ultrasonic methods. Moreover, the durability properties of waste rubber powder cement concrete were examined through shrinkage performance tests, chloride ion flux tests, and freeze-thaw resistance tests. The following conclusions are presented:  
1. Among the three influencing factors--the water-cement ratio, sand ratio, and waste rubber powder content--the optimization design results indicate that when the water-cement ratio was held constant and the sand ratio was maintained between 33% and 36%, the waste rubber powder content should not exceed 10%. Additionally, it was observed that the water-cement ratio exerted the most significant influence on the flexural strength of cement concrete, whereas the sand ratio had the least impact. 2. Both the particle size and content of waste rubber powder significantly influenced the mechanical properties of cement concrete. Specifically, under consistent mesh sizes, increasing content led to a decline in compressive strength, flexural strength, and dynamic elastic modulus; conversely, at constant content levels, larger mesh sizes corresponded to lower compressive strength, flexural strength, and dynamic elastic modulus. Furthermore, impact resistance tests revealed that higher content and smaller particle sizes of waste rubber powder enhanced the concrete's crack resistance. Statistical analysis utilizing the two-parameter Weibull distribution can be employed to assess the initial crack impact number (N\({}_{1}\)) and final crack impact number (N\({}_{2}\)) of waste rubber powder cement concrete. 3. Among the waste rubber powders, the 10-mesh variant exhibited the most pronounced noise reduction effect, whereas the 20-mesh, 30-mesh, and 60-mesh varieties showed comparable noise reduction effects in concrete. Moreover, an increase in waste rubber powder content correlated with improved noise reduction capability. 4. Waste rubber powder addition resulted in decreased drying shrinkage of cement concrete. Moreover, larger content and mesh size led to reduced drying shrinkage. Conversely, under constant content, impermeability increased with higher mesh  
Figure 26: The results of the drying shrinkage test **(a)** the mass loss rate of 10-mesh waste rubber powder cement, **(b)** the mass loss rate of 20-mesh waste rubber powder cement, **(c)** the mass loss rate of 30-mesh waste rubber powder cement, and **(d)** the mass loss rate of 10-mesh waste rubber powder cement. sizes of waste rubber powder; meanwhile, with consistent mesh size, impermeability rose with increasing content, although the impact on concrete impermeability was more pronounced. Additionally, the mass loss rate of waste rubber powder cement concrete decreased with greater mesh size of waste rubber powder, and higher content correlated with lower mass loss rates. This study delivers a thorough examination of the mechanical properties of waste rubber powder cement concrete, offering a fresh perspective for concrete research and application. It can not only decrease waste rubber pollution of the environment, while also increasing the recycling rate of raw materials, but also potentially broaden the application scope of cement concrete and alleviate its limitations. Conceptualization, S.M. ; data curation, Y.X. ; formal analysis, S.M. ; funding acquisition, J.L. ([PERSON]); investigation, J.L. ([PERSON]); methodology, Y.X. ; project administration, J.L. ([PERSON]); resources, J.L. ([PERSON]); software, Y.X. ; supervision, S.M. ; validation, J.L. ([PERSON]); writing--original draft, [PERSON] ([PERSON]); writing--review & editing, S.M. All authors have read and agreed to the published version of the manuscript.