Research on dynamic mechanical properties of polypropylene fiber-modified rubber foamed concrete

To investigate the dynamic properties of polypropylene fiber-modified rubber foamed concrete (PPR-FC), foamed concrete (FC), and foamed concrete with recycled rubber granules (R-FC) specimens with wet densities of 700 kg/m3, 800 kg/m3, and 900 kg/m3 were prepared for evaluation of dynamic performance (including dynamic elastic modulus and impact resistance) and unconfined compressive strength. The test results showed that PPRFC was density-dependent. The polypropylene fiber (PP fiber) was helpful in improving the toughness of the material. In particular, the improvement of the unconfined compressive strength and impact performance based on the destructive test was more obvious, with a maximum increase of 18.15% and 78.34%, respectively. The impact performance was determined by the maximum number of impacts that can be withstood. The rubber granules increased the specimen's ductility, which is positive to impact resistance with the maximum improvement of 470.41%, meanwhile increasing the wet density that can effectively remedy the decrease of the unconfined compressive strength and dynamic elastic modulus. Moreover, the dynamic elastic modulus was positively related to the frequency as a whole due to the strain rate effect. Then, the microscope test showed that fiber can connect the bubble structure, making the bubble structure more stable, but also increasing the number of irregular and large-diameter bubbles. The rubber granules changed the shape of bubbles around the granules, and increased the number of large-size bubbles, while decreasing the overall number of bubbles. Finally, according to the test results, the prediction formula of dynamic elastic modulus and impact resistance based on multiple factors was established. As a result, this paper can provide a reference for the application of PPR-FC in engineering practice.