The Study On Preparation And Properties Of Composite Phase Change Material For Temperature Control Of Mass Concrete

The country's economic and social development is always accompanied by various large-scale infrastructure construction.Mass concrete is often used in large infrastructure projects.Therefore,in order to meet the needs of social and economic development,it is vital to provide high-quality concrete.However,the temperature crack caused by hydration heat in the curing process of mass concrete has been troubling engineers and technicians.This paper thus had summarized the commonly used manners to solve the temperature crack of mass concrete,analyzed the advantages and disadvantages,and finally put forward the scheme for temperature control of concrete by using phase change materials.According to the selection principle of phase change material(PCM)and the temperature control requirement of mass concrete,the composite PCM with polyethylene glycol(PEG)as core material and inorganic porous material as carrier was selected as the candidate of final PCM.In the preparation process of composite PCM,when PEG was directly immobilized to inorganic porous materials,the heat storage capacity would be greatly reduced,which resulted in the reduction of effect for temperature control.Aiming at this problem,a new composite PCM was prepared by using dopamine modified silica fume as carrier to fix PEG,and compared with unmodified composite PCM,which proved that dopamine modification in composite PCM achieved the regulation of PEG phase change behavior,the mechanism of dopamine biomimetic modification was analyzed,and the heat storage capacity of composite PCM was improved.In addition,the low thermal conductivity of phase change concrete would lead to the decrease of its heat dissipation rate,which was harm to the temperature control of mass concrete.In this paper,a composite PCM with high phase change enthalpy and high thermal conductivity was prepared by adsorption and reduction of copper ions by activated carbon(AC)and jujube pit biochar(JPB),inspired by the fact that carbon-based adsorbent could be used as both PCM carrier and adsorbent for metal ion in waste water.It was found that JPB was more suitable for fixed PCM than AC.Finally,based on the new PCM prepared,combined with previous studies,the adiabatic temperature rise was proposed as a scale to measure the effect of the PCM on the temperature control of concrete with different in content of PCM.The results showed that the temperature control performance of concrete increased with the incorporation of PCM.In this paper,by incorporating phase change materials into concrete,the feasibility of controlling the temperature crack caused by hydration heat in the initial stage of concrete curing was studied.Three new composite PCM were prepared and developed.Moreover,two methods,improved properties of composite PCM,were proposed and verified,which provided more theoretical basis of the study of composite PCM.It also provided a broader basis for the application of PCM in the field of temperature control of mass concrete.