| Traditional asphalt pavement has affected road traffic and urban eco-system due to its poor air and water permeability.Meanwhile,the output of municipal solid waste incinerated bottom ash?MSWI-BA?is increasing annually,but the disposal technology is not matched with modern city development.Thus,the innovation of"environment-friendly”building materials has become a research hotspot in the field of road construction,by the background of"Sponge City"struction project and the eco-environmental protection policy of"13th Five-Year Plan".In this study,the utilization of MSWI-BA was combined with porous asphalt concrete?PAC?.The technical feasibility,optimal implementation and environmental safety of recycling MSWI-BA as aggregate?MSWI-BAA?in PAC were investigated.As a result,the PAC with MSWI-BAA and MSWI-BA disposal technology could be innovated.Herein,the physicochemical properties and microstructures of MSWI-BA with different particle sizes were firstly studied,so that the particle size and replacement rate of using MSWI-BA in PAC were determined.Secondly,a type of PAC,PAC-13 containing MSWI-BAA was designed based on the PAC design method.The optimum asphalt content of PAC was determined using MSWI-BAA with three particle-sizes of 4.75-9.5 mm,2.36-4.75 mm and0.075-2.36 mm at various replacement rates of 10%,20%,30%,50%and 70%,respectively.The performance including water stability,high-and low-temperature stability and water permeability of PAC-13 with different particle-sizes and replacement rates of MAWI-BAA was then tested through standard methods.The optimum replacement rate of using MAWI-BAA with certain particle size was determined by comparing the experimental data and technical requirements of"Technical Specification for Construction Technology of Highway Asphalt Pavements"?JTG F40-2004?for OGFC and“Technical Specification for Permeable Asphalt Pavement”?CJJ/T190-2012?for PAC.Finally,the environmental safety of using PAC with MSWI-BAA at the optimal implementation was evaluated by investigating the influence of major heavy metals leaching behavior from MSWI-BAA.The main conclusions are as follows:?1?The size distribution of MSWI-BA used in this study was matched with the technical requirement.The element and mineral composition of MSWI-BA were similar to those of natural aggregates.Moreover,the leaching concentrations of Cr,Cu,Zn and Pb from MSWI-BA with different particle sizes were lower than the limit values of"Hazardous Waste Identification Standard"?GB 5085?.As a result,MSWI-BA was identified as harmless solid waste and satisfied with the basic conditions for being used as aggregate in road construction.?2?The optimum mix ratio of PAC-13 was determined as follows:13.2 mm?10%?,9.5 mm?27%?,4.75 mm?45.8%?,2.36 mm?2.2%?,1.18 mm?3%?,0.6 mm?2%?,0.3 mm?2%?,0.15mm?2%?and 0.075 mm?2.5%??weight of screen residue?,3.5%of mineral powder,0.3%of polypropylene fiber and 4.9%of asphalt content.?3?The optimum asphalt content of PAC-13 containing MSWI-BAA showed a positive correlation with the replacement rate of MSWI-BAA.Specifically,the optimum asphalt content increased by 0.15%0.39%with every 10%increase of the replacement rate;and for each replacement rate,the larger the MSWI-BAA particle size was,the higher the optimum asphalt content would be.?4?The best replacement rates of using 4.759.5 mm,2.364.75 mm and 0.0752.36 mm MSWI-BAA for PAC were 30%,20%and 30%,respectively,considering the road performance and stormwater permeability.?5?The leaching of selected heavy metals in PAC with MSWI-BAA was relatively stable during the whole experimental period,and the leaching concentrations were far below the limit values of?GB 5085?.The results indicate that PAC with MSWI-BAA is friendly to the environment. |
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