Mechanical Properties And The Phase-Change Stability Of Fiber Reinforced Concrete With Micro-Encapsulated Phase Change Materials

With the rapid development of the world economy and the construction industry,the proportion of building energy consumption in the total social energy consumption is increasing dramatically.Currently,in China,building energy consumption accounts for about 30% of the total social energy consumption,and failure to focus on building energy efficiency will directly constrain the sustainable development of the economy.The development and application of energy-saving materials for buildings has become a hot research topic in the world.In recent years,the application of PCM(Phase Change Materials)in the field of construction has gradually emerged as a green and environmentally friendly way to save energy in buildings.PCM phase change concrete is a new type of energy-saving building material made by mixing PCM phase change material with concrete matrix material,which is mainly used in the field of construction by using phase change material to absorb and release latent heat when phase change occurs and keep the characteristics of its own temperature change not much,so as to play the effect of energy saving and temperature regulation.Compared with ordinary concrete,PCM concrete has the advantages of higher specific heat capacity,better heat storage performance,and lower self-weight,etc.PCM applied to bulk concrete can also effectively reduce the internal temperature rise rate of concrete,improve the temperature field of the concrete matrix,with the effect of cutting peaks and filling valleys,which is conducive to reducing the generation of early cracks in concrete and improving the durability of concrete.Therefore,PCM concrete applied to the building envelope can regulate indoor temperature changes and reduce indoor temperature fluctuations,thus improving the comfort of human living environment.In order to better promote the application of PCM phase change concrete in the field of building energy efficiency,the basic mechanical properties,phase change cycling performance and its stability of fiber-reinforced microencapsulated phase change(MPCM,Micro-encapsulated Phase Change Materials)concrete are studied experimentally and analyzed numerically in this paper.Based on the experimental study of the mechanical properties and phase change cycle stability of MPCM microencapsulated phase change concrete incorporated with(1%)hook steel fibers and(0.1%)short-cut basalt fibers,the temperature regulation properties and phase change cycle structural stresses of fiber-reinforced MPCM concrete were numerically simulated by ANSYS finite elements.The results show that:(1)With the increase of MPCM admixture(volume admixture: 5%,7%,10%),the28 d cubic compressive strength and tensile strength of fiber-reinforced MPCM concrete showed a gradual decrease.However,the strength of fiber-reinforced MPCM concrete is higher(or close to)than that of ordinary concrete with the same water-cement ratio at the appropriate MPCM admixture level.(2)The effect of short-term phase change cycles(small number)on the compressive and tensile strength of MPCM concrete is not significant,while the density of fiber-reinforced MPCM concrete decreases to a lesser extent as the number of phase change cycles(n)increases.(3)The results of ANSYS finite element numerical simulation of the temperature field of fiber-reinforced MPCM phase change concrete wall show that the three indexes of thermal storage coefficient,temperature decay multiplier and delay time of MPCM phase change wall are better than those of ordinary concrete,which indicates that MPCM concrete has better thermal performance and can effectively regulate the fluctuation of indoor temperature and improve the indoor thermal comfort.(4)The results of ANSYS numerical simulation of the temperature stress of fiber-reinforced MPCM concrete walls show that the temperature stress and displacement deformation of the fiber-reinforced MPCM concrete matrix gradually decrease with the increase of MPCM admixture(and both are smaller than the displacement deformation of ordinary concrete).Therefore,the temperature control effect of MPCM is more and more obvious as the amount of MPCM increases,and the mechanical properties of the phase change cycle of fiber-reinforced MPCM concrete are more stable.