Researech On Standard Compaction Method For Cement Stabilized Sand Gravel

Cement stabilized sand gravel (CSSG)is widely paved as the base course in China. The mix must reach a certain degree of compaction, and the compactness is one of the most important requirements. Generally, Modified Proctor Compaction Test (MDCT) is used to get the maximum dry density (MDD) and optimum water content, the former is used as the standard to evaluate the degree of compaction in construction field.The method to determine the maximum dry density is according to The Methods of Materials Stabilized with Inorganic Binders for Highway Engineering (JTG E51-2009).For sand gravel, it is difficult to get the similar compaction curves as clay which can be used to determine the maximum dry density and optimum moisture content. When doing the MDCT, the MDD increased with the amount of water added to the mix,and the vibrating compaction tests done by the 3rd -Generation Vibrating Compactor shows the similar result done by MDCT, and the moisture content of the compacted saturated samples is stable.In order to explain the compaction property, the paper do analyses as follows:the mineral constituent of the sand gravel , grain composition,the interaction between water and grain,the permeability's influence on compaction property. The main minerals of the sand gravel are quartz, feldspar etc, which are difficult to deform during compaction. Meanwhile, the content of the fines that make the material cohesive is very small, according to the sieving test results of the 5 kinds of sand gravel used in Bei(an)Hei(he) expressway construction, almost 95 percent of sand gravel is coarse grain (larger than 0.075mm),it makes the sand gravel have the different compaction property compared with clay soil.According to the relevant reference ,for sand gravel having high content of coarse grain, the permeability parameter is 100 thousand times of clay soil; the capillary pressure decrease with both the grain diameter's augmentation and saturation aggrandizement. When the sand gravel is under saturation condition, the water lubricates the grain surface without high pore water pressure for the good permeability of sand gravel. To sum up, the saturation condition is defined as the best compaction condition for sand gravel.On the basis of understanding the compaction property of sand gravel and the best compaction condition, the paper establish a new method to determine cement stabilized sand grave's maximum dry density——"Saturated Sand Gravel Compaction"+"Cement Filling Correction". The cement slurry fills the void between the aggregate grain, without changing the volume of compacted samples, therefore the dry density of CSSG increases. When the method is applied in the mix design ,it shows that the method is not only accurate but also easy to use. The method solve the problems that confuses the highway tester personal ,which make them cannot but fabricate data in order to get the appointed compaction curves. The maximum dry density determined by the method is more applicable to control the degree of compaction and it is better suited the current construction technology and vibrating roller's application.