Search Results (2)

Polypropylene (EPP) concrete offers advantages such as low density and good thermal insulation properties, but its relatively low strength limits its engineering applications. Waste steel fibers (WSFs) obtained during the sorting and processing of machining residues can be incorporated into EPP concrete (EC) to enhance its strength and toughness. Using the volume fractions of EPP and WSF as variables, specimens of EPP concrete (EC) and waste steel fiber-reinforced EPP concrete (WSFREC) were prepared and subjected to cube compressive strength tests, splitting tensile strength tests, and four-point flexural strength tests. The results indicate that EPP particles significantly improve the toughness of concrete but inevitably lead to a considerable reduction in strength. The incorporation of WSF substantially enhanced the splitting tensile strength and flexural strength of EC, with increases of at least 37.7% and 34.5%, respectively, while the improvement in cube compressive strength was relatively lower at only 23.6%. Scanning electron microscopy (SEM) observations of the interfacial transition zone (ITZ) and WSF surface morphology in WSFREC revealed that the addition of EPP particles introduces more defects in the concrete matrix. However, the inclusion of WSF promotes the formation of abundant hydration products on the fiber surface, mitigating matrix defects, improving the bond between WSF and the concrete matrix, effectively inhibiting crack propagation, and enhancing both the strength and toughness of the concrete. Full article

Creep stress is a detrimental stress generated by the surrounding rock during the operation of the secondary lining of the supporting structure used for high-stress soft rock tunnels in railways, highways and other projects. Therefore, the present study aims to investigate and provide solutions for damages such as cracking and deformation caused by creep stress. For this purpose, research methods used in the literature and experimental studies, as well as the theoretical, data and numerical simulation analyses, were used. Accordingly, the mix proportion design, specimen production and the tests of physical and mechanical properties of EPP foam concrete were carried out. Moreover, the EPP(polypropylene foam) concrete was used as the buffer layer of the supporting structure, the practical application of which was verified through numerical analyses. The findings of the study revealed the effective compression performance of the mix proportion design method. Furthermore, the EPP foam concrete was found to be able to absorb the energy generated by the creep of the surrounding rock, consequently reducing the surrounding rock pressure acting on the secondary lining structure, which, in turn, ensures the safety of the operation. The findings of the study can be used as a reference for designing similar projects. Full article