Composition Design And Performance Study Of Composite Shaped PCM Recycled Pavement Brick

The recycling of construction waste is of great significance to energy conservation and environmental protection.The preparation of composite shaped PCM recycled aggregate pavement brick could not only improve the utilization rate of construction waste,meet the basic requirements of the road,but also make it have the ability of anti-freezing,thus reducing the potential risk of the road.In view of the lack of research on recycled aggregate pavement bricks with composite shaped PCM,this paper designed and prepared two kinds of composite shaped PCM（PEG-400/Si O₂,Tet/Si O₂）,analyzed their microstructure,phase change temperature,phase change enthalpy,thermal stability,and systematically studied the effects of different recycled aggregate proportions（60%,70%）and composite shaped PCM contents（3%,5%,7%,10%）on the volume,mechanics,skid resistance,thermal conductivity,temperature regulation and other properties of recycled aggregate pavement bricks.The main research results were as follows:（1）The micro-performance of composite shaped PCM was characterized.The SEM analysis of the two composite shaped PCMs showed that the shaping effect of PEG-400/Si O₂ composite shaped PCM was better than that of Tet/Si O₂ composite shaped PCM.The differential scanning calorimetry analysis of the two composite shaped PCMs showed that the two composite shaped PCMs meet the requirements of the phase change temperature（1℃-5℃）of the composite shaped PCM recycled aggregate pavement brick.The thermogravimetric analysis of two kinds of composite shaped PCM showed that the loss of composite shaped PCM was small,the physical and chemical properties were stable,and the thermal stability was good under the TGA test temperature range.（2）The mechanical properties and anti-skid performance of composite shaped PCM recycled aggregate pavement brick were expounded.When the proportion of recycled aggregate was 60%,the 28-day compressive strength and flexural strength of recycled aggregate pavement brick specimens with different composite shaped PCM contents（3%,5%,7%,10%）were greater than those of composite shaped PCM recycled aggregate pavement brick with the recycled aggregate proportion of 70%.When the proportion of recycled aggregate was 60%and the contents of phase change material were 3%and 5%,the strength of the test specimen meet the requirements of MU20 strength grade specified by the state.After 25 phase change cycles,the 28d compressive strength and flexural strength of the test piece could meet the requirements of the MU15 strength grade specified by the state.And the phase change material didn’t leak during the phase change cycle test.The phase change performance of the composite shaped PCM recycled aggregate pavement brick was proven to have long-term stability.Using BM-VI digital display pendulum friction coefficient tester,the anti-skid performance of the cured benchmark recycled aggregate pavement brick specimens and two kinds of composite shaped PCM recycled aggregate pavement brick specimens were tested.The results showed that the test specimens could meet the requirements of the existing standards for the anti-skid performance of recycled aggregate pavement brick BPN≥60,indicating that the recycled aggregate pavement brick mixed with composite shaped PCM could be used to pave pavements such as sidewalks,parks,residential areas,etc.（3）The thermal conductivity of composite shaped PCM recycled aggregate pavement brick was revealed.The test results of the thermal conductivity on the composite shaped PCM recycled aggregate pavement brick showed that the thermal conductivity of the composite shaped PCM recycled aggregate pavement brick was lower than the thermal conductivity of the reference recycled aggregate pavement brick,and the incorporation of the composite shaped PCM could lead to the increase of the internal porosity of the pavement brick,which could lead to the reduction of the thermal conductivity,and with the increase of the content of the composite shaped PCM,the thermal conductivity of the two composite shaped PCM recycled aggregate pavement bricks could gradually decreased.Under the same content,the thermal conductivity of Tet/Si O₂ composite shaped PCM was greater than that of PEG-400/Si O₂ composite shaped PCM,indicating that Tet/Si O₂ composite shaped PCM could play a higher thermal efficiency.（4）The temperature-regulating performance of composite shaped PCM recycled aggregate pavement brick was analyzed,and the optimum content of composite shaped PCM was determined.The temperature distribution and change of the recycled aggregate pavement brick specimen during the ice melting test were studied by infrared thermal imaging technology,and it was verified that the addition of two kinds of composite shaped PCM could delay the cooling process of the recycled aggregate pavement brick specimen,and the greater the content of PCM,the more obvious the effect.The temperature-regulating performance,mechanical performance and economic cost of the composite shaped PCM recycled aggregate pavement brick were comprehensively considered.It was suggested that the proportion of recycled aggregate in the composite shaped PCM recycled aggregate pavement brick was 60%,and the optimum content of composite shaped PCM was 5%.