The Studyon Pavement Performance Of Cement-Emulsified Asphalt And Reef Sand Solidification

At present, the development and utilization of the south China sea is an important link in our country’s economic and national defense construction. Marine islets are our base for the activities, and it is imperative to construct the islets.But islets are away from the mainland and lack of building materials, ocean shipping costing too much, which greatly restricts the development of the islets.In order to reduce the cost of building materials and protect the Marine ecosystem, using local materials, the coralcays rockand calcareous sand that is richin the sea view as aggregate construction, which can make up for the inadequate materials to maximum.This paper is using the cement and emulsified asphalt as the main binder, and adopting gradation of coral reef rock and calcareous sand act as coarse and fine aggregate, studies the basic mechanical properties、road performance and the fine micro structure. It proved the feasibility of roads or at the airport’subgrade using the cement-emulsified asphalt and reef sand solidification. The following conclusions were drawn:(1) According to the theory of maximum density curve, combined with control of the largest aggregate diameter, Taylor "n" method was used to design the five kinds of coral reef sand grading, called SHJS1～SHJS5.By calculating each gradation of non-uniform coefficient and coefficient of curvature, combined with "bailey method" to evaluate the grading, the results showed that:in addition to the grading SHJS5 was difficult to evaluate, other four grading was good.The skeleton effect was more noticeable, and fine material filling effect was good.(2) The experiment designed three factors with different dosage of cement、emulsified asphalt and the outside water by uniform experiment. It was determined different7groups designed mixtureof maximum dry density and optimum moisture content by the compaction test.It also determinedthe specimen of cement-emulsified asphalt and reef sand solidification’s waterdosage and quality control.Using 150 mm×150 mm cylindrical sample and taking theaction of static pressure to mold, mixture of different? groups design was conducted 7d unconfined compressive strength test. The test showed that the grading SHJS1 and grading SHJS2 strength difference was very small, and gradingSHJS 3 to 5’strength was significantly lower than the above two.After optimizing, we made the decision to choose gradingSHJS2 as a final graded mixture.(3) The base materials of the cement-emulsified asphalt and reef sand solidification’s 7 d unconfined compressive strength value was low. With the increase of time and water discharge, the strength of the mixtureincreased.Considering thefeatures of reef sand particle breaking and moisture of the mixture out slowly, the 7 d strength was viewed as standard strength of base materia of the cement-emulsified asphalt and reef sand solidification.(4) Regardless of 28d or 7d strength of the cement-emulsified asphalt and reef sand solidificationwas less than the cement stabilized sand reef.The 90d compressive modulus of resilience of cement-emulsified asphalt and reef sand solidification was significantly lower than the same age stage of cement stabilized sand reef.The more dosage of emulsified asphalt use, the less strength and modulus of the mixture. However, just the splitting strength, cement stabilized sand reef and cement-emulsified asphalt and reef sand solidification were small under the same age.Immersion strength test showed that the strength of mixture obvious declined in the condition of the rain. Special attention at the grass-roots level of humidity condition was needed in practical engineering. Filtration rate of thecement-emulsified asphalt and reef sand solidification appeared to increase sharply, then gradual growth as time goes, and gradually stabilized finally.Incorporation of emulsified asphalt can effectively reduce the drying shrinkage strain of the mixture. After the cement content was more than 6%, adding of the emulsified asphalt was not improved drying shrinkage properties of the mixture. Temperature shrinkage strain curve of thecement-emulsified asphalt and reef sand solidification and cement sand and cement stabilized sand reef was roughly same.In spite of the mixture of emulsified asphalt, temperature shrinkage performance of the mix had a little impact.Cement dosage and temperature shrinkage performance were linked with each other.(5) Through the grass-roots strength, shrinkage test and water stability test, material on the base of thecement-emulsified asphalt and reef sand solidification was recommend. The optionof the ratio about the mixture was 6% dosage of cement and emulsified asphalt content of 2.5%.(6) Coral rock andreef sandwere easy to broken.In sample molding process,a massive ground broken appeared incoral rock andreef sand. The broken rate Bg=37.64.The fragment of aggregate which grain size was greater than 4.75 mm was more serious, especially range in 19.5 mm～19.5 mm, with its percentage suddenly increase about 10%.(7) The emulsified asphalt was thermodynamic instability system. Demulsification process is the process of oil-water separation.The mixed cement will accelerate the emulsion rate of emulsified asphalt.Coral sand was a kind of alkali aggregate and has good adhesion with cationic emulsified asphalt. Hydration reaction of coral sand, asphalt and cement occurred in the slurry interface of the mixture.Intertwined with emulsified asphalt, cement hydration products have formed a bulge of needle cylindrical three-dimensional structure, which canmake loose aggregate unit glue into a whole, played an important role of geotextiles, and enhanced the ability of resistance to deformation of the mixture.Cement filled the pore of interface and improved the bonding ofinterface.By SEM test, the conclusions can be drawn that no the generation of new material existed and the mixture of each material was only physical composite.