The Effect Of Slag And Sludge Artificial Aggregate On The Performance Of Asphalt Mixture Instead Of Natural Stone

With the rapid development of road construction in China,natural stone,as a non renewable resource,is decreasing,which increases the cost of road construction to a certain extent.As the main product of municipal solid waste incineration,the slag aggregate prepared by pretreatment has certain mechanical strength and cementitious activity,which has the potential to replace the natural stone in asphalt mixture;Sludge aggregate can be prepared from domestic sludge by sintering,which also has the potential to replace natural stone.Therefore,in order to improve the resource utilization value of slag aggregate and sludge aggregate in road engineering,this paper studies slag aggregate and sludge artificial aggregate,and explores the key technical problems of their application in asphalt mixture,so as to provide reference for the design and application of slag and sludge aggregate asphalt mixture.The composition characteristics,particle size distribution,physical and mechanical properties,main chemical components and micro morphology of slag aggregate were studied by screening test,X-ray fluorescence spectrometry(XRF)and scanning electron microscopy(SEM).The results show that the proportion of slag aggregate in the range of1.18 mm ～ 9.5mm is the highest;Compared with limestone aggregate,slag aggregate has lower density and higher water absorption.Through Marshall design method,the optimal asphalt aggregate ratio of slag asphalt mixture with different particle size and different replacement rate is determined.The research results show that the optimal asphalt aggregate ratio of slag asphalt mixture will gradually increase with the increase of replacement rate for slag aggregate with any particle size range.Through immersion Marshall test,freeze-thaw splitting test,rutting test and low-temperature bending test,the road performance of slag asphalt mixture with different particle size and substitution rate was tested.The results show that the use of slag aggregate with particle size greater than 4.75 mm instead of natural stone will have adverse effects on the road performance of the mixture;The results show that the residual stability and the maximum bending strain of the mixture can be improved by using slag aggregate with particle size range of 1.18 mm ～ 2.36 mm and 2.36 mm ～ 4.75 mm,but the increase range will gradually decrease with the increase of slag aggregate replacement rate,and the larger the particle size is,the greater the decrease range will be;The leaching test of heavy metals in slag aggregate shows that the leaching concentration of heavy metals is far lower than the standard,which can be regarded as harmless waste.When it is used as asphalt mixture instead of natural stone,it has good environmental safety.Thermogravimetric analysis(TGA)was used to analyze the thermal properties of domestic sludge,and the quality changes during heating were obtained.The pretreatment temperature(650 ℃)was determined;The orthogonal experiment with four levels and three factors was designed to study the effects of raw material ratio,sintering temperature,sintering time and boric acid content on the performance of sludge aggregate.The results show that sintering temperature is the most important process parameter affecting the performance of sludge aggregate.The heavy metal leaching toxicity test of sludge aggregate shows that it has good environmental safety;The results show that under the same conditions,the dynamic stability of the sludge aggregate asphalt mixture is higher than that of the slag asphalt mixture,the maximum bending strain is basically the same as that of the control group and the slag asphalt mixture,while the residual stability and TSR are slightly lower than that of the slag asphalt mixture,but still meet the requirements of the specification..