Experimental Study On Cement And Rha Stabilized RAP Base Material

As a result of the rapid development of the construction industry,more and more construction waste is produced.At present,construction waste is mainly processed by stacking and landfilling,which not only takes up limited land resources,but also has a huge impact on the natural environment.Meanwhile,cement stabilized macadam is widely used in road construction due to its excellent performance.However,shortage of aggregates occurs in China due to the large demand for limited natural aggregates.Furthermore,as a by-product of crops,rice husk can be utilized in the field of road engineering,which has a high output and good development prospect.Therefore,construction waste may be recycled as aggregates,and Rice Husk Ash（RHA）may be utilized as cement in cement stabilized macadam,which can on one hand save land resources,and on the other hand hold the stance with green and sustainable development by utilizing waste resources.In this paper,the phase composition and micromorphology of RHA were first analyzed.It was found that RHA mainly includes O,C,Si and a small amount of metal elements,and the high content of amorphous Si O₂is the main reason for the pozzolanic activity of RHA.Then,the aggregate properties of Recycled Asphalt Pavement（RAP）and Recycled Concrete Aggregate（RCA）were measured by conducting strength tests,compressive rebound tests,shrinkage tests and freeze-thaw tests,with natural aggregates in traditional cement stabilized macadam partly replaced by recycled aggregates and cement replaced with RHA in different content.The results show that:With the extension of curing time,the mechanical properties of cement stabilized RAP material are improved when RHA added.However,the strength and frost resistance of the base material decrease,but the appropriate amount of RHA（20%）can improve the shrinkage performance of the base material.When RHA was added with 40%,compressive strength,splitting strength,bending strength and compressive modulus of RAP base material all met the requirements of the pavement base specification for the corresponding curing age.Therefore,it is recommended that the maximum ratio of RHA to replace cement in cement stabilized RAP base materials is 40%.As natural aggregates partly replaced with RCA,the strength and modulus of the base material can be lifted.By replacing 40%natural aggregate with RCA,the compressive strength,splitting strength,flexural strength and compressive modulus of resilience of the base material are improved,but the shrinkage and frost resistance of the base material are adversely affected.The influence of different RHA content on cement RHA stabilized RAP/RCA base material is consistent with that of the base material without RCA.Therefore,it is also recommended that 40%RHA be used as the maximum content of cement stabilized RAP/RCA base material.