The standard concrete mixing procedures indicate that during concrete mixing process, it is recommended to use fully saturated- dry surface course aggregates (FSDCA). It is clear that the exact application of this rule will produce a concrete of a good quality. But in practice, course aggregates are exposed to weather changes. This actual situation will lead to dry the course aggregates in summer and to over wet it during winter. To investigate the effect of using different moisture content course aggregates on concrete product in work site an experimental program had been done. This program consists of testing 54 concrete samples (27 cube +27 prism). The samples were divided into three groups (a, b, and c). The second group (b) was a concrete mix containing dry aggregates, while the third group (c) contained over wet aggregates and the first group (a) was the basic standard mix using (FSDCA). One third of the samples were tested in the age of 7 days, while the other third was tested in the age of 14 days and the rest after 28 days. Test results show that there are reduction in compression and flexural strengths of concrete due to the use of different moisture content course aggregates. Finally, new recommendations were concluded to be used in practice to overcome the mentioned repetitive error and to be more close to the theoretical recommendations in order to get better concrete properties.
Problematic soils, especially clayey soil, are problematic for engineering projects in their natural state because of clay's swell-shrinkage phenomenon. Numerous methods and stabilizer materials have been used to enhance clay's geotechnical properties and make them appropriate for construction. One of the significant methods of stabilization of problematic soil is using waste materials like waste glass, waste stone, waste plastic, etc. Due to the waste stone's consistency reducing water content and increasing the soil's strength, it has been employed in many civil engineering studies. Waste stone is available in various forms, including waste stone powder (WSP). WSP is produced by blasting tunnels or cutting huge stone blocks. Hence, the main aim of this study is to review the influence of WSP on improving the geotechnical properties of problematic soils treated with WSP, for this purpose, the treated problematic soils with various percentages of WSP are compared with natural soils. This study evaluates physical properties (i.e., Index properties, linear shrinkage/swelling, optimum moisture content, and maximum dry density) and mechanical properties (i.e., unconfined compressive strength and California bearing ratio). Also, the effect of WSP on decreasing the thickness of pavement layers was reviewed
Deep mixing technology is used to improve the engineering properties of soil. In this review, previous studies on the properties and problems of weak soils were collected and explained, focusing on silty soils found globally and locally. The study also includes a discussion of physical and chemical improvement methods, specifically (cement columns). The advantages of deep mixing technology are also covered from an engineering and economic point of view, as well as its relationship to the environmental impact, as it is one of the sustainable development techniques due to its use of environmentally friendly materials. In addition, one of the objectives of this research is to study the methods of adding cement, whether in the form of powder (dry method) or mortar (wet method). A comparison was made between them to clarify the advantages and disadvantages. It was found that what distinguishes the use of the dry method from the wet method is that the former is more common. The method's effectiveness depends on the soil's moisture content, so the technique is ineffective in soils with less than 30% water content. As cement hydration produces a cementitious gel (CSH) that binds soil particles together, leading to early strength gain, pozzolanic reactions cause increased shear strength and decreased soil compressibility. Finally, some recommendations are included in this article to understand the behavior of cement columns in improving soil and avoiding problems