A new experimental approach to the improvement of sandy soils with construction demolition waste and cement

摘要

Soil improvement has become an important issue on which further investigations should have to be performed in depth as a result of an increasing demand rate on land use in order to compensate increasing population. The main reasons for soil improvement are to decrease plasticity, reduce permeability and compressibility and increase soil strength. Wastes can be used along with some other additive materials such as cement, lime, fly ash, and bitumen in the improvement of soils which are inadequate in terms of engineering properties. In recent years, as a result of increasing rates of earthquakes along with the numbers of constructions which are to be demolished as the updated regulations point out, a great amount of wastes have been accumulating. These wastes are generally referred to as construction demolition wastes (CDW). There exist some methods which are considered for the elimination of these wastes. One of the mentioned methods is to use construction demolition wastes in soil improvement procedures. Within the context of this study, effects of construction demolition wastes (CDW) and cement (CMT) on soil stabilization and engineering properties of sandy soils (SS) were investigated. Parameters such as optimum ratios of CDW and CMT, bearing capacity and settlement values, soil improvement depths, and time factor were analyzed. Consequently, an equation with high-degree correlations was obtained in order to use CDW and CMT efficiently at optimum ratios. It was determined that by using CDW, increments of up to 3.09 times were attained in the values of bearing capacities. The optimum value of improvement depth for sandy soil was obtained asH/D= 0.75 (H: soil improvement depth,D: diameter of the model footing) up to a pressure value of 520 kPa. It was also found that the highest bearing capacity with respect to time was reached at the end of 28 days and a significant increment did not take place in the values of bearing capacities after exceeding the mentioned time period. Therefore, it is proposed that at least 28 days should pass after the completion of any soil improvement procedure before any further construction work is initiated.