Study On Performance Of Cold Reclaimed Mixture Of Emulsified Asphalt Mixed With Rice Husk Ash

High activity rice husk ash is a kind of biological ash produced by the combustion of ordinary rice husk under the condition of medium and high temperature and saturated oxygen.Rice husk ash can be used as filler or auxiliary cementitious material to improve the performance of ordinary cement concrete and asphalt mixes due to its high pozzolanic activity and better filling effect of micro-aggregate.In this paper,high activity rice husk ash was proposed to be added into cold recycled emulsified asphalt mixture,and two research routes were developed,namely rice husk ash instead of cement(RRC)and rice husk ash instead of mineral powder(RRL).The content of rice husk ash and cement was controlled from 0% to 2%,and that of rice husk ash and mineral powder was controlled from 1% to 5%,respectively,and various properties of the mixture were tested.Firstly,the mixture ratio of the two groups of mixtures was designed,and the optimal water content and emulsified asphalt content of the two groups of mixtures were determined by using the geo-compaction method and the dry-wet splitting strength ratio,and the grading range of the mixtures was determined according to the regeneration specification.20% new limestone aggregate was added to the mixture to solve the problem of less coarse aggregate in the recycled material and to improve the friction resistance between the skeleton.Then,the main elements and microstructure of rice husk ash were obtained by SEM scanning and EDX energy spectrum analysis,and the microscopic images of rice husk ash under different multiples were compared.According to the analysis of element peak spectrum,the content of silicon element in rice husk ash in this experiment is about 40%,mainly in the form of silica,and the microscopic images show that the rice husk ash has a very large specific surface area and a high porosity.Finally,the laboratory performance of the two groups of mixtures was evaluated by conventional laboratory experiments.The results show that the substitution of rice husk ash for cement improves the low temperature and mechanical properties of the mixture,but does not significantly improve the high temperature strength of the specimen,and reduces the water stability to some extent.Replacing the mineral powder with rice husk ash can slightly improve the high temperature and mechanical properties of the mixture,but slightly reduce the low temperature properties and water stability.According to the experimental results,the substitution of rice husk ash for mineral powder into the mixture should not exceed 3% of the aggregate and other fillers,and the substitution of rice husk ash for cement should not exceed 1.5%.Due to the low temperature performance and water stability of the mixture,rice husk ash is more suitable to be added into the emulsified asphalt cold regenerated mixture in non-cold and arid areas with little rainfall.