Experimental Study On Properties Of Cement/RHA Stabilized Base Materials

With the development of national economy and society,China produces a huge amount of construction waste every year.Improper treatment of construction waste will pollute the air,soil and groundwater.The main components of construction waste are waste concrete blocks and bricks.The recycled aggregate formed after crushing can be reused in engineering construction.In addition,China is a big country of rice production,and the annual output of rice husk ash（RHA）is up to 40 million tons.Because of its high content of Si O₂,RHA has a good utilization prospect.China’s road network construction needs to consume a lot of mineral resources and cement.The utilization of construction waste and RHA can reduce the use of mineral resources and cement to a certain extent,and play the role of energy conservation and environmental protection.This paper studies the influence of different RHA content on the road performance of cement stabilized base materials from strength performance,freeze-thaw resistance and shrinkage performance.The rice husk ash content is respectively 0%,20%,40%,60%and 80%of the cement quality.On this basis,the road performance of cement rice husk ash stabilized base material containing recycled aggregate was further studied by using construction waste recycled aggregate instead of 40%natural aggregate.The main conclusions are as follows.The unconfined compressive strength and splitting strength of cement stabilized macadam decrease with the increase of RHA content,and increase with the increase of curing time.The higher the content of RHA,the greater the increase range of the later strength of cement stabilized macadam.When the content of RHA is 20%,the 7d unconfined compressive strength and 90d splitting strength of cement RHA stabilized macadam can meet the specification requirements,and the dry shrinkage performance is improved.With the increase of RHA content,the flexural strength,compressive modulus of resilience,freeze-thaw resistance and temperature shrinkage of the mixture decrease to varying degrees.When the RHA content is less than 40%,the flexural strength,compressive modulus of resilience and residual compressive strength ratio（BDR）can meet the requirements of the specification.In order to meet the requirements of road performance,it is suggested that the RHA content of water stabilized RHA stabilized macadam should not exceed 20%.When 40%natural aggregate is replaced by recycled aggregate,the unconfined compressive strength and splitting strength of cement RHA stabilized mixture with recycled aggregate decrease with the increase of RHA content,and increase with the increase of curing time.Compared with the mixture without recycled aggregate,the compressive strength and splitting strength of the mixture with recycled aggregate increase about 15%.When the content of RHA is 20%,the unconfined compressive strength of 7d can meet the specification requirements,and the splitting strength of 90d can meet the specification requirements when the content of RHA is 40%.When the content of RHA is 40%,the compressive modulus of resilience and freeze-thaw resistance can meet the specification requirements.When the content of RHA is 60%,the flexural strength can meet the specification requirements.After adding recycled aggregate,the dry shrinkage coefficient and temperature shrinkage coefficient of the mixture increase linearly with the increase of RHA content.Compared with the mixture of pure natural aggregate,the dry shrinkage performance is improved,but the temperature shrinkage performance becomes worse.For the mixture with recycled aggregate,it is suggested that RHA content should not exceed 40%.