Study On Material Composition Design And Pavement Performance Of Cement Stabilized Coral Sand Subbase

With the continuous development of the "the belt and road" strategy,Countries around the world have gradually increased the development and construction of marine reefs.When people construct on islands,they lack gravel materials for road construction.Generally,they need to collect transportation from ports,which not only consumes time and energy,but also affects the normal construction.There are abundant coral sand resources on the island,which can be used to fill the road base.However,due to the brittleness and high water absorption of coral sand,there are some problems in road engineering application,such as cracking of road base and insufficient strength.Therefore,according to the characteristics of reef coral sands engineering demand,the study of cement stabilized coral sands mix design,mechanical properties and micro-structure,shrinkage performance and road performance,on the one hand,will make rational use of coral sands,on the other hand,protect the ecological environment,reduce the cost of construction,with significant social and economic benefits.Firstly,the mineral composition and microstructures of coral sands are studied and analyzed.Then through laboratory tests,the mix proportion of cement-stabilized coral sand mixture is determined,the crushing form of coral sand is analyzed,and the compressive failure mechanism of cement-stabilized coral sand mixture is grasped.;Secondly,the cement stabilized coral sand mixture is mixed with seawater and maintained in fresh water,and then the performance is studied.The hydration products,micro-pore and micro-structure characteristics of grain interface of cement stabilized coral sand mixture are analyzed to clarify the relationship between macro-performance and micro-structure.Finally,the influence of concrete expansive agent on shrinkage characteristics of cement stabilized coral sand mixture is studied,and the pavement performance of cement stabilized coral sand mixture is evaluated from mechanical properties,water stability and scouring performance.The results show that the strength of coral sand mixtures with 7% cement content meets the design requirements of 3MPa~5MPa.At this time,the mixtures show brittle failure characteristics and cracks penetrate through coral particles.Seawater mixing and curing can improve the early strength of cement-stabilized coral sand,delay the development of intermediate strength,but have little influence on the later strength.The cement-stabilized coral sand mixture designed according to the dosage of 6% cement and 8% FQY expansive agent meets the design requirements,has good crack resistance,and the average shrinkage coefficient is 32.3% lower than that of 7% cement without early strength agent.The strength and stiffness of cement-stabilized coral sand mixture gradually increase with the increase of curing age,and the softening coefficient is greater than 0.9.The cement-stabilized coral sand mixture has good water stability,which meets the performance requirements of the pavement base on the island.