Preparation And Properties Research Of Phase-changing Energy-storing Concrete

Concrete can be employed as a matrix for embedment of phase change materials(PCM),and the phase-changing energy-storing concrete(PCESC)can be obtained by this way.The energy storage performance and energy efficiency of PCESC can be achieved by PCM absorbing or releasing heat as it undergoes a phase transition.Butyl stearate was impregnated into pores of expanded perlite,and limestone powder wrapped up it to prepare phase-changing energy-storing aggregates(PCESA).PCESC was prepared by PCESA replacing some sand and silica fume replacing a part of cement.Experiments of compressive strength and splitting tensile strength were carried out for PCESC.The effects of PCESA content on fracture toughness and fracture energy of PCESC were investigated based on three-point bending beam test.The micro-morphology of PCESC was characterized by using SEM.The thermal properties of PCESC were characterized by DSC technique.The thermal cycling test was used to determine the thermal reliability of PCESC.The compressive strength and splitting tensile strength test results show that: the strength of PCESC reduced due to the addition of PCESA,while the addition of silica fume increased the strength of PCESC.When PCESA content is 20% and the silica fume content is 5%,PCESC compressive strength and splitting tensile strength are 48.34 MPa and 3.35 MPa,respectively.These are same as the common concreteResults indicated that PCESC exhibit ductile failure and the development of crack in PCESC can be defined into three stages: crack producing stage,crack stable propagation and crack unstable fracture.The influence of PCESA on fracture toughness of PCESC is insignificant,and the fracture energy decrease with the increase of PCESA volume fraction.From the SEM images of PCESC,it can be concluded that the addition of silica fume leads to a dense hydrated cement paste.The PCESA remain intact in PCESC,and interfacial transition zone(ITZ)between hydrated cement paste and PCESA has a good integrity.The hydrated cement paste of ITZ are C-S-H and AFt.Based on DSC measurements and the blank runs,it revealed that the specific heat capacity of PCESC increases with the increase of PCESA content,whether it is in heating or cooling process.When the PCESA volume fraction is from 0% up to 20%,the specific heat capacity is increased by 75%.The specific heat capacity and energy storage of PC-20 have a significant improvement.After repeated 100 thermal cycling,the PC-20 compressive strength decreased by 9%,equivalent specific heat capacity decreased by 11% and equivalent energy storage decreased by 16% than that of PC-20 without thermal cycling,respectively.So it can be concluded that PC-20 has good thermal reliability.