An Experimental Study on Production of Planting Soil from the Viewpoint of Soil Physical Properties

We have already developed a new recycling system for high-water content mud by using paper debris and powder polymer in order to increase the recycling rate of the construction sludge and water purification sludge.Modified soils produced by this system have several features such as high failure strength, high failure strain and high durability for drying and wetting. In spite that modified soils have several features, the utilization of modified soils as landfill materials is not largely increasing because a large amount of free excavated soils which are competing goods of modified soils remains. Therefore, in this study, the utilization of modified soils as planting soils is focused. In the recycling system developed previously, the addition rate of paper debris is determined based on the water content of the mud. However, it is difficult to produce the planting soils of constant quality because soil/paper mass ratio is not always constant if the water content of the mud is different. Therefore, the purpose of this paper is to investigate the optimal soil/paper mass ratio from the view point of soil physical properties and to produce the planting soils of constant quality regardless of the water content of the mud. It was confirmed through the experiments that the most appropriate soil/paper mass ratio was in the range of 5-6. In case of wet type planting soils, it was impossible to satisfy all target values, but it can be considered that the quality of wet type planting soils will be improved and they will satisfy all target values if the other lightweight construction wastes such as wooden chips are mixed with wet type planting soils.