Improving Thermal and Mechanical Property of Lightweight Concrete Using N-Butyl Stearate/Expanded Clay Aggregate with Alccofine۱۲۰۳

Phase change material (PCM) as n-butyl stearate (n-BS) was immersed in expanded clay aggregate (ECA) by two methods, direct immersion at room temperature and immersion at elevated temperature (۳۰oC, ۴۰oC and ۵۰oC). ECA after ۹۰min of immersion with n-BS at ۴۰oC came to standby in its weight proportion (increased by ۲۴%). After immersion, these aggregates (۴۰oC) were mixed in cement slurry for preventing leakage and homogenous mixture with concrete. Oozing circle a leakage test was conducted on all the ECA with and without cement slury coating (room and elevated temperatures). ECA with cement slurry coating gave a reduction in leakage of ECA-PCM by ۴۵%. Alccofine۱۲۰۳ was partially replaced (۱۰% and ۲۰%) by cement to improve mechanical properties in lightweight aggregate concrete. Compressive, flexural, thermal conductivity, DSC analysis and leakage test on aggregate and concrete specimens were conducted on all the mixes. Compressive strength for ۱۰% replacement gave ۳۱.۷ kN/m۲ and ۳۲.۸ kN/m۲ for ۷th day and ۲۸th day, respectively. Similarly, flexural strength gave ۶.۱۲ kN/m۲ for ۲۸ days. DSC analysis of pure PCM (n-BS) gave ۳۰.۴۲oC and ۲۳.۲۵ oC for its melting and freezing temperature with ۱۳۴.۲ J/g and ۱۲۹.۳J/g as enthalpy for its melting and freezing points, respectively. Thermal conductivity for mix-۳ (۱۰%PCM-ECA +۱۰% alccofine۱۲۰۳) gave the lowest value of all the mixes i.e, ۱۳% less than the reference mix. There was no leakage or any stain marks were observed on the filter paper till ۱۰% incorporation.

Keywords:

Phase change material , Expanded clay aggregate , Immersion , Oozing circle , Alccofine۱۲۰۳ , Thermal conductivity