Effect of coal waste on grain failure of cement-stabilized sand due to compaction

Stabilization of the soil on the site is one of the methods used to improve the mechanical properties of soils. On the other hand, the replacement of cement by other materials for reducing the environmental issues has always been of interest to engineers. The soil is compacted after mixing with the stabilizing agent. The application of compaction energy can cause the grains to fail. By performing the standard compaction and subsequent soil grading tests, this study investigated the effects of different factors such as compaction moisture, cement percentage, percentage of coal waste, and grading method on the grain failure after compaction. The results of this study showed that increasing the cement weight ratio increases the maximum dry density and reduces the optimum moisture content. The increase in the weight ratio of coal waste for the sample with 3% cement increases the maximum dry density. However, for the sample with 6% cement, the addition of coal waste up to 10% increases the dry density and then reduces the density. All percentages of moisture in the compaction test result in a smaller size of sand grains due to the grain failure. On the other hand, up to the near optimum moisture, increasing the moisture will reduce the failure of grains. The grain failure rate increase is in the primary moisture contents. Also, increasing the moisture content for a mixture with 3% cement reduces the grain size, and for the mixture with 6% cement, it increases the grain size (reducing the rate of grain failure). Finally, it could be stated that the addition of coal waste has a significant effect on the change in the behavior of soil stabilized with cement in the area of grain failure.