Study On The Performance Of Stabilized Recycled Crushed-stones With Cement-Fly Ash

With the development of urbanization in China,a large number of construction waste is produced from construction,demolition and other projects,meanwhile a great quantity of gravel resources are used to the highway construction.As the road engineering has the characteristics of multi-structure level,multi-level,some natural sand and gravel can be replaced by construction waste which is processed.In 2017 NPC&CPPCC,the government once again stressed the green development,and thermal power plant emissions---fly ash is one of the main environmental pollutants,as a commonly used semi-rigid base mixture---cement fly ash stabilized crushed stones consumption of large amounts of fly ash.Based on the requirement of green development and energy conservation,this paper studies the effect of recycled aggregate on the design of cement fly ash stabilized crushed stone and the influence of road performance.It is related to the development of cemented fly ash stabilized crushed stones Technical requirements to provide reference.According to the research of Guangdong province recycled aggregate manufacturers,analysis of different manufacturers of recycled aggregate technical indicators.The results show that the recycled aggregate density is small,the water absorption is large and the mechanical performance index is poor when compared with the natural aggregate.However,reasonable classification and post-treatment process can effectively improve its performance.Considering the representation of aggregate properties and the ease of material extraction,the recycled aggregate of GuanggangXincheng was selected as the raw material of cement-fly ash stabilizes recycled crushed stones to study the effects of different recycled aggregates contents(0%,20%,40% 60%,80%,100%)to mixture's road performance.The experimental results show that with recycled aggregates contents increased,mixture's unconfined compressive strength,splitting strength and bending strength of different ages(7d,28 d,90d)had the trend of increasing first and then decreasing and reached the peak at 80% recycled aggregate content.Recycled fine aggregate can further enhance the strength of the mixture.Besides,the effect of recycled coarse aggregate source and composition on the strength of the mixture is significant.In this way,it is suggested to strengthen the classification and sorting of recycled aggregate.The shrinkage test results show that the shrinkage strain and water loss rate increase with the increase of recycled aggregate content.The full recycled aggregate mixture is about 54% higher in shrinkage strain than that of the 100% recycled coarse aggregate mixture.Therefore,a special compound additive is prepared to improve shrinkage strain by 58%.Static compaction molding is quite different with field compaction conditions,and the specimen compaction is difficult to meet the requirements of 98%.gyratory compaction makes the aggregate distribution and more consistent with the scene,simultaneously compact degree is controllable.according to the results of the study,it is suggested that the strength of cement and fly ash stabilized gravel material should be replaced by 105 times of rotary compaction method instead of traditional hydrostatic molding method.