Performance assessment of capric acid-ethyl alcohol/expanded vermiculite phase change material incorporated cement mortar for thermal insulation in buildings

Due to global warming, the construction sector is looking for newer materials that can be incorporated into buildings to improve occupant thermal comfort while reducing energy consumption. The ability of construction materials to store thermal energy can be enhanced by incorporating phase change materials (PCM). A PCM is a substance that releases and absorbs energy at phase transition temperatures to offer useful heating or cooling. The addition of PCM in construction materials for thermal insulation has been proven beneficial by many researchers. The current study explores the feasibility of the incorporation of an organic PCM composite, which is developed by impregnating expanded vermiculite (EV) with capric acid (CA) using ethyl alcohol (EA) under vacuum conditions in cement mortar. Cement mortar mixes with EV, CA-EA/EV based PCMs, and PCMs with partially added nano silica and coir fiber combinations (PSC) were prepared by replacing fine aggregate in varied weights. Initially, the study on the primary characteristics of the developed PCM was introduced based on mechanical behavior, microstructure observations, and thermal effects. To estimate the field exposure capacity, PCM composite mortar boards were developed and tested for their physical and mechanical characteristics. Based on the findings of these tests, it was concluded that the presence of PCM improves the thermal characteristics of the mortar boards and the addition of nano silica and coir fiber enhances the physical and mechanical strength of the mortar boards. With regard to the characterization of the mortar, there was an increase in flexural strength by 8.06 % and a decrease in chloride diffusivity by 10.24 %, in water absorption by 17 %, the capillary water absorption coefficient by 8.56 % and the ultrasonic pulse velocity by 18.48 % relative to the control sample after addition of PSC into the mortar. Apart from the strength and durability studies, differential scanning calorimetry (DSC), energy-dispersive X-ray spectroscopy (EDS), thermogravimetry analysis (TGA) and scanning electron microscopy (SEM) tests were also carried out to characterize the thermal, chemical and morphological effects of the developed cementitious composite boards. As per the SEM and EDS test results, the fine aggregate replaced with 5 % of PCM in addition to nano silica and coir fiber (PSC-5 %) possesses better compatibility with the mortar by effectively penetrating through the pores. The DSC test results showed the melting and freezing point of PSC-5 % integrated mortar as 32.47 °C and 20.91 °C, respectively. A thermal conductivity value of 0.129 W/m·K also demonstrated the efficiency of PSC-5 % mortar board for maintaining better thermal comfort in buildings. The TGA assessment reported that the proposed PCM composite cement mortar board has excellent thermal durability.