Thermal and mechanical properties of concrete incorporating pumice containing form-stable phase change materials and silica fume

Abstract

Due to the sharp rise in global energy consumption within the construction sector in recent decades, researchers have increasingly advocated for integrating phase change materials (PCMs) in concrete to mitigate energy usage in this domain. While previous studies have explored various types of PCM and additives in concrete mixes, this research represents a pioneering investigation into the concurrent utilization of PCMs using pumice containing polyethylene glycol (PEG) 1000, paraffin, and silica fume. Paraffin as an organic PCM was selected for this research due to its low cost and wide availability. Since the primary objective was to increase the volume of the PCM while minimizing any leakage within the concrete matrix, a particular ratio of silica fume was incorporated into the pumice to prevent PCM leakage. In pursuit of concrete with optimal thermal performance, pumice aggregates containing PEG 1000 replaced 10 %, 20 %, and 30 % of the sand in the target concrete. Similarly, pumice aggregates containing paraffin replacements at the same levels were also prepared and used. The evaluation entailed rigorous tests, including compressive and flexural strengths, water absorption, thermal conductivity, simulation of sunlight & humidity, and thermal performance tests. The results indicated that replacing 10 % of pumice with PEG 1000 in concrete specimens resulted in a reduction of thermal conductivity by 44 % (from 1.548 to 0.866 W/mK) and average surface temperature by 24 %, compared to the reference specimens, though it reduced the compressive strength by 35 % (from 30.9 to 20.2 MPa) and increased the water absorption by 18 %. Also, substituting PEG 1000 with paraffin reduced the thermal conductivity by 56 % (from 1.548 to 0.678 W/mK) and average surface temperature by 42 % while decreasing the compressive strength by 37 % (from 30.9 to 19.4 MPa) and increasing the water absorption by 26 %. Both PEG 1000 and paraffin improved the thermal performance of concrete, resulting in reduced overall energy consumption in concrete buildings. This comprehensive study pushes the boundaries of PCM applications, offering valuable insights for optimizing concrete formulations to achieve enhanced energy-efficient building materials.