Study on Sludge Recycling with Compaction Type and Placing Type by Rice Husk-Cement-Stabilized Soil Method

摘要

As the results of dredging activities, a huge amount of sludge has been generated. And one of recycling methods for the sludge has been developed by using paper debris and cement. This is called “Fiber-cement-stabilized soils method” (FCSS). The modified-sludge produced by this method has several features such as high failure strength, high failure strain, and high durability. However, it is almost difficult to apply this method directly for the dredged sludge in Mekong delta, because it is hard to obtain a large amount of paper debris. By the way, a large amount of agricultural wastes are discharged, especially in the case of rice husk in Mekong delta. If the rice husk (RH) can be used instead of paper debris, it will be possible to recycle the dredged sludge in Mekong delta by FCSS. Moreover, FCSS is generally carried out by compaction method. However, compaction method cannot be used in some constructions such as backfilling. In these cases, placing method is generally used and one of recycling methods that applied placing type is Liquefied-Stabilized Soil Method (LSS). In this method, high flowability and low bleeding rate materials are made by adding the cement and water with excavated soil. LSS is possible to simplify construction sequence because LSS flows like concrete mortal and compaction is not necessary. However, LSS method showed some disadvantages such as low durability for drying and wetting conditions. In this study, several specimens were made by using rice husk with FCSS and LSS, and unconfined compression tests were carried out. It was confirmed that rice husk can be used as a substitute of paper debris in FCSS and LSS. Furthermore, empirical equations were obtained as a function of initial water content of the sludge to estimate the optimum additive amount of rice husk and cement for both compaction and placing types.