A Sustainable Lightweight Pumice Concrete Slab for Underground Utility Protection: Experimental Validation and Finite-Element Analysis

This study presents a failure-mitigation-oriented investigation into the use of pumice aggregate concrete slabs as lightweight, thermally insulating, and cost-effective alternatives to traditional concrete barriers for the protection of underground natural gas pipelines and electrical power lines in urban environments. A comprehensive methodology combining mechanical strength testing, thermal conductivity assessment, and hydrocarbon fire resistance evaluation was employed, supported by transient thermal finite-element analysis (FEA) to model material behavior under extreme conditions. Experimental results revealed that the pumice slabs achieved a 61% reduction in weight, an 88% decrease in thermal conductivity, and a 41% increase in cost efficiency relative to C30/37 concrete. Critically, under hydrocarbon fire exposure up to 1,200°C for 2 h, the slabs maintained structural integrity while limiting backside temperatures to about 55°C–76°C, nearly one-fourth that of conventional concrete, which reached 214°C. This substantially reduces thermal-induced failure risks. FEA simulations closely matched test data, with conservative deviations aligned with safety design margins. Mechanical tests further confirmed the slabs’ resistance to combined soil and vehicular loading, validating their robustness under adverse geotechnical conditions. Field implementation within Istanbul’s gas distribution infrastructure highlighted additional advantages such as ease of handling and rapid deployment, which collectively reduce the likelihood of installation-related failures and operational delays. These findings establish pumice-based concrete as a resilient, sustainable, and failure-resistant solution for urban subsurface infrastructure. Future research is recommended to explore fiber reinforcement strategies, long-term durability under cyclic loading, and comparative failure modes against other lightweight protective systems.