Application Of Phase Change Insulation Technology In Winter Concrete Maintenance

With the state’s great investment in infrastructure,the state council and the provincial and municipal governments have approved a large number of infrastructure projects,many of which have to be constructed in low temperature environment in winter due to large amount of construction work and long construction period.Concrete is a widely used engineering material in engineering construction.However,the low temperature environment will seriously affect the development process of concrete and weaken the compressive strength,tensile strength,impermeability and durability of concrete.Therefore,the maintenance of concrete at low temperature is very important..In the traditional winter construction,people adopt the addition of antifreeze,material pre-heating method,heat storage and curing method,electric heating method,steam insulation method,or combination and collocation according to different needs.These maintenance methods are very effective and can meet the temperature environment needed for the development of concrete in winter,especially at lower temperatures,can use electric energy and steam to provide external heat source for concrete and ensure the temperature of concrete development,but this will also bring large maintenance expenses to construction enterprises,resulting in construction costs will be greatly increased.The traditional maintenance methods are high in cost,complex in operation,high in electric load and low in safety due to the need of heat source,such as excessive can reduce the heat source the cost of heat source,will greatly improve the profits of engineering enterprises.As an excellent energy storage material,the phase change material after energy storage can become a temporary heat source in a certain period of time,heat preservation and heating for concrete when the temperature is most needed;at the same time,depending on the phase change reversibility of the phase change material,recharge after cooling,realize recycling and reduce the maintenance cost.This paper first proposes the concept of using phase change materials for concrete curing,using capillary force to achieve the uniform distribution of phase change materials;then,different phase change materials,porous media are compared and selected to find the most suitable phase change materials and dielectric materials;the size of phase change heat preservation module ——11 cm×11 cm×2 is determined by height method experiment cm,and the uniform distribution is better realized by splicing the jointing method.Through the dynamic height experiment,the capillary force of different viscosity paraffin wax in different particle size and different material fabric was compared.The lower the viscosity of paraffin wax,the higher the rise height and capillary force in porous medium,the higher the temperature of paraffin wax,the higher the rise height and capillary force in porous medium,and the smaller the particle size,the higher the rise height of paraffin wax init.and the fiber fabric due to the temperature loss of paraffin wax too fast to cause too fast solidification,so the rising height is very low.Three phase change heat preservation modules,one is sand + paraffin,the other is fabric + paraffin,the other is paraffin bleached beads microcapsules.The paraffin microcapsules were filled into the bleached beads by vacuum saturation experiment.The mass of paraffin in sand + paraffin module,fabric + paraffin module was 50 g,medium to fill the insulation module as the principle,and the packaging material of the module was aluminum foil + polyethylene composite material.The thermal experiments of phase change heat preservation unit are carried out,including heat storage performance experiment,thermal uniformity verification,influence of wind speed.Through thermocouple,analog input module,analog output module,PC end using vb programming,the change of temperature on the inside and outside of phase change insulation module after energy storage is measured,and the insulation effect of different phase change insulation modules is compared.Sand particles + paraffin insulation unit have the best insulation effect.Thermal uniformity of different parts of paraffin + sand particles is verified.The results show that the thermal uniformity is good,and the capillary force can realize the thermal uniformity of phase change insulation module.Use fan and air duct for insulation module under wind speed performance test,the results show that the wind speed will greatly affect the thermal insulation performance of the phase change insulation module,and the external thermal insulation maintenance structure is very necessary.