| With the rapid development of urban population and the increasing of city scale,the mainly developing situation of our society is the transition of villages and small towns to city.The change makes the original green plants,water-based underlayer replaced by the dense concrete.The urban heat island has become increasingly prominent.It effects not only reduces the comfort level of urban residents,but also endangers human health and economic development.It is expected that the urban thermal environment can be improved by finding the suitable water-cement ratio or displacement ratio to improve the reflectance of building surface or pavement to improve urban macroscopic reflectance,achieve the effect of energy conservation,emission reduction.According to this concept,40 groups of cement sample surface reflectance were tested for different water-cement ratio,different mixture replacement ratio and different curing methods through 350 days,and the following conclusions were obtained through analysis based on data results.(1)In the spectrum(250nm～2500nm),the reflection capacity of indoor curing blocks in the early stage of ultraviolet and visible bands is stronger than that of wet curing blocks.However,with the progress of hydration reaction,the growth rate of wet curing blocks is higher than that of indoor curing blocks.(2)To analyze the influence of reflectance of water-cement ratio,reflectance spectra of different water-cement ratio blocks were detected.The results showed that the reflectivity of the block with higher water-cement ratio was higher,and in the preexperimental period the reflectivity of the cement block with W/C of 0.51 was higher than 23.9%that W/C of 0.30,while the moisture one was 88.2%(3)When the water-cement ratio are the same(ordinary Portland cement)in the same curing conditions,and the unique variable is mixed content(fly ash or blast furnace slag),the whole process of 6 kinds of replacement ratio is divided into three levels(high,middle and low replacement ratio).The block reflectivity for high replacement ratio has higher reflectivity than cement block of middle replacement ratio;the middle replacement ratio has higher albedo than the low one.In each layer’s replacement ratio,the two kinds of replacement ratio just have slightly different.(4)When the block is tested in the same water-cement ratio,and raw materials are the same,the only variable for curing conditions makes tested block into three groups(the first group of ordinary Portland cement block,a second group of a certain proportion for replacement of fly ash cement block and a third group as a percentage of the blast furnace slag cement replacement block)found that wet curing test blocks have deeper hydration and greater reflectivity degree of increase than indoor curing test block,and its reflectance increases more than 10%in all.In order to verify the relationship between the surface temperature of cement test block and reflectance,the surface temperature of cement test block was measured by relevant instruments.It is found that the outdoor temperature and solar radiation are the most important factors that cause the surface temperature change of the test block by integrating meteorological factors.When the fluctuation of outdoor temperature and solar radiation is small,the measured surface temperature data of the test block are analyzed,and it is found that the higher the reflectance of the test block surface,the lower the upper surface temperature of the test block.By improving the reflectance of the upper surface,the increase of the upper surface temperature can be reduced,and the indoor temperature can be reduced as well.The expected effect of energy saving and emission reduction can be achieved. |
