Thermal energy storage cement mortar with direct incorporation of organic and inorganic phase change materials

Abstract

Direct incorporation of phase change materials (PCMs) in the mortar matrix increases the effective thermal mass of a structure without increasing the size or significantly changing its weight; thereby reduces the energy consumption and brings comfort/well-being throughout the various seasons. Hence, the effect of direct incorporation of various types of PCMs in a mortar matrix needs to be addressed to optimize PCM addition and its type. In the present study, five different PCMs, two in-organic, and three organics were directly incorporated into the cement matrix from 5 to 15% as partial replacement of cement. Various studies such as compressive strength, flexural strength, acid and sulphate attack, Differential scanning calorimetry (DSC) analysis, Fourier transform infrared spectroscopy, thermal conductivity, stability of PCM (1000 thermal cycle test), thermal performance, and leakage test were conducted. Organic (n-BS, PEG-600, and OM29) PCMs have significantly decreased the strength of cement mortar with a peak reduction of 74% for HS24 (15%); whereas inorganic (HS24 and HS29) PCMs gave considerably equal strength of conventional mortar up to 10 wt%. A statistical technique using Minitab was used to validate the actual experimental values (compressive strength of HS24) with predicted values, and it was observed that the error in experimental values and the predicted values is less than 5% for 28 and 60 days curing thereby showing a confidence level of 95%. Acid attack tests on mortar specimens with PCMs gave a drastic reduction in compressive strength at 90 days. DSC analysis was conducted on all pure PCM materials and found that its temperature range and enthalpy exist in the human comfort zone. The stability for HS24 gave an enthalpy of 145.8 J/g and 122.6 J/g for melting and freezing point after 1000 cycles. The temperature variation of organic PCMs was nearly the same as normal cement mortar, and the maximum reduction of 5 °C was attained with inorganic PCMs. No leakage was observed for HS24, n-BS, and HS29 PCMs.