Research On The Impacts Of NH₄Al（SO₄）₂·12H₂O/SiO₂Form-Stable Phase-Changing Energy-Storage Material On The Fire Resistance Of Concrete Structure

With the development of social urban construction, concrete structures has been become the main type of building structures for a long time, and its fire resistance performance has been a hot research topic. In order to improve the fire resistance of concrete structures with the heat inertia of the concrete, phase-changing energy-storage material of NH4A1(SO4)2·12H2O encapsulated by SiO2[NH4Al(SO4)2·12H2O/SiO2] was prepared by sol-gel method. NH4A1(SO4)2·12H2O was coated by the method that three-dimensional network structure formed by hydrolysis of SiC14.Then Phase-changing energy-storage concrete was prepared by means of the fine aggregate of concrete substituted by it., expected to reduce the heating rate with it to achieve the purpose of it, that improved the fire resistance of concrete structural. In order to research on the impacts of NH4A1(S04)2·12H2O/SiO2form-stable phase-changing energy-storage material on the fire resistance of concrete structure, preparation and characterization of NH4Al(SO4)2-12H2O/SiO2, preparation and performance testing of phase-changing energy-storage concrete, finite element analysis on temperature and stress field of it were completed. The results show that:The storage performance on phase-changing energy-storage material with different energy density was tested by DSC. The results showed that the energy density of,which the content on NH4A1(SO4)2-12H2O was70%,was202J/g,and the higher content of the NH4A1(SO4)2·12H2O,the higher the energy density of it; The thermal stability on it was tested by TG. The results showed that the phase-changing energy-storage material had good heat resistant performance below100℃, and no chemical reaction occurs between SiO2and NH4A1(SO4)2-·2H2O.Phase-changing energy-storage concrete was prepared with the PCMs and modifyed PCMs by the means of the fine aggregate of concrete substituted by them. Preparation, mechanical properties and thermal performance were researched, the results showed that the mixture workability of phase-changing energy-storage concrete was better than ordinary concrete, and the maintenance cycle on it was2.5times of ordinary concrete; When content of PCMs decreasesd from10.7%to4.6%, compressive strength of concrete increased from8.62Mpa to18.85Mpa, and the lower content of PCMs, the higher the compressive strength of it; The Energy density and the specific heat capacity were becomes larger with the higher content of the PCMs, but the thermal conductivity was opposite.Making finite element analysis on the fire behavior of phase-changing energy-storage concrete structure by ANSYS, the results showed that the heating rate was reduced with the content of PCMs increased, and the opposite side temperature of it was reduced by77%; Constitutive relation of concrete structures was improved by form-stable PCMs, and the thermal inertia and the mechanical roperties was also increased; From the results of the stress field analysis and the temperature field analysis see that with the addition of form-stable PCMs, slowing the heating rate of concrete structures, improving the thermal inertia of concrete, making concrete structure to maintain stability and integrity for longer, so as to improve the fire resistance of concrete structures.