Effect of construction demolition wastes on the bearing capacity of sub-base fillings

Large quantities of waste are generated during the construction of new buildings and demolition of current structures. Outdoor storage or disposal of waste creates significant environmental and health risks. The use of Recycled Concrete Aggregate (RCA) in construction projects is a crucial strategy for sustainable growth, both financially and environmentally. This study investigated the effect of RCA admixture on the shear strength properties of sandy soil and the ultimate bearing capacity of the single foundation resting on it. The sandy soil was reinforced with different proportions (%5.00, %10.00, %15.00 and %20.00) and sizes (2.00-4.76mm and 4.76-6.30mm) by weight of GDA. Vertical loading tests were carried out in the laboratory on square model foundations in a test tank. The experiments were carried out on both unreinforced sand and GDA reinforced sand soils. The soil specimens in the tank were prepared at 80% relative stiffness (Dr) for each percentage and size of GDA admixture. To support the experimental results, numerical analyses were performed using the Plaxis 3D program based on the finite element method. In addition to these studies, three bearing capacity theories, which are frequently used by engineers, were used in the analysis. Terzaghi (1943), Hansen (1970) and Vesic (1973) were used to calculate the ultimate bearing capacity of the model foundations. As a result of the index and strength tests performed in the laboratory, it was determined that the dry unit volume weight values of the mixtures increased up to approximately 4% with increasing GDA by weight ratio. A decrease in void ratio was observed with increasing GDA ratio. It was determined that the internal friction angle of the mixtures increased up to 14% with increasing GDA by weight ratio. As a result of the model loading tests, it was concluded that the bearing capacity of the model foundation increased by 40-48% as the GDA ratio by weight increased. The coarse-grained GDAs used in the study resulted in a 3-6% increase in bearing capacity compared to the fine-grained GDAs. It was determined that the experimental and numerical results were quite compatible with each other. The theoretical bearing capacity formula that gives the closest results to both experimental and numerical results is Vesic (1973). In addition, this study contributes to the gap in this field in terms of analyzing the effect of GDA use on sandy soils.