Investigation on thermal and mechanical characteristics of concrete mixed with shape stabilized phase change material for mix design

Abstract

This paper aims at evaluating thermal and mechanical behaviors of concrete mixed with shape stabilized phase change material (SSPCM) in order to apply the concrete mixed with SSPCM for structural members. Toward that goal, material tests are performed on cylindrically shaped specimens having different water to cement ratios, SSPCM content, and temperature conditions. In addition, two different mixture methods are tested; the first is to add SSPCM to the concrete mixture, and the second is to replace the fine aggregate with the same amount of SSPCM. From the tests for thermal behaviors, it is observed that the thermal conductivity decreases and specific heat increases as SSPCM content increases. Regarding mechanical behaviors, the compressive strength and elastic modulus of concrete mixed with SSPCM decrease with SSPCM content, and the reduction rate is linearly proportional to the mass fraction of SSPCM to concrete. When the specimens are exposed to temperature higher than the melting point of the SSPCM, the compressive strength of the concrete is decreased. However, full recovery of the decreased strength is also observed when the heated specimens are cooled down to room temperature. Based on the experimental findings, an equation for calculating strength of concrete mixture is proposed and used to design mix proportions of concrete mixed with SSPCM. The material tests show that the specimens fabricated according to the proposed method satisfy the target strength.