الفهرس 
CHAPTER (1) INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
This thesis is intended to experimentally study the geotechnical behavior of recycled concrete and recycled brick as geotechnical materials mixed with natural sand to be tested as a replacement soil. Concrete and brick debris was collected from field and grinded to small sized particles. Routine tests were conducted to measure their natural physical and mechanical properties in parallel with naturally – quarried sand. Following that, sand was mixed with each recycled material individually following the mixing ratios: 0.0% -100%, 25% - 75%, 50% - 50%, 75% -25%, and 100% - 0 % by dry weight. Identically, the same index tests were repeated regarding new mixtures and the same properties were re-evaluated.
Following that, an experimental program was assigned to evaluate the performance of recycled materials purely and mixed with sand as replacement soil for soft clay. A highly plastic clayey soil (CH) was dried, pulverized, and mixed with water to produce very soft condition, acting as a soft layer. Three main parameters were regarded in the program; replacement depth (h) / footing width (b) ratio, type of replacement soil, and mixing ratio of sand: each recycled material. Four typical values of h/b ratio were tried namely; 0.25, 0.50, 0.75, and 1.0.Vertical loads were incrementally applied and load – settlement measurements were recorded. A total number of 37 tests were conducted.
Two sets of conclusions were derived from this experimental work. The first one which is concerned with identification and characterization of 100% recycled materials and their mixtures with sand. Results revealed that addition of sand to recycled materials has led to new mixtures whose properties were better than pure recycled materials. Addition of sand to recycled materials raised the maximum dry density and specific gravity. On the contrast, adding recycled materials to sand significantly increased the CBR values. Gradation of mixtures lied between limits of sand and 100% recycled concrete and recycled brick.
Typical interpretation of bearing pressure / settlement of all tests was graphically plotted. It was noticed that replacement of soft clay by different granular materials resulted in modifying the load – settlement behavior of the replacement soil / soft clay system. The two - layered system became stiffer. Significant improvement in ultimate bearing capacity was detected. Increasing the replacement thickness regardless the replacement type lead to an increase of ultimate bearing capacity and reduction of settlement.
100% recycled materials performed better than 100% sand and their combinations with sand. It was also identified that increase of recycled material content in the mixture is directly proportional to the improvement in ultimate bearing capacity. One of the main conclusions is that h/b ratio should be > 0.25 for all replacement soils to obtain a good level of performance. Strong trend lines were drawn to relate the ultimate bearing capacity to different parameters of the study.