Increasing amount of construction waste and, concrete remnants, in particular pose a serious problem. Concrete waste exist in large amounts, do not decay and need long time for disintegration. Therefore, in this work old demolished concrete is crashed and recycled to produce recycled concrete aggregate which can be reused in new concrete production. The effect of using recycled aggregate on concrete compressive strength has been experimentally investigated; silica fume admixture also is used to improve recycled concrete aggregate compressive strength. The main parameters in this study are recycled aggregate and silica fume admixture. The percent of recycled aggregate ranged from (0-100) %. While the silica fume ranged from (0-10) %. The experimental results show that the average concrete compressive strength decreases from 30.85 MPa to 17.58 MPa when the recycled aggregate percentage increased from 0% to 100%. While, when silica fume is used the concrete compressive strength increase again to 29.2 MPa for samples with 100% of recycled aggregate.

Unpaved roads are subject to rapid deterioration and large deformations under mechanical and environmental stresses that can render them impassable. Prior work has shown that plastic soils can be mixed with a polymeric chemical admixture to create a hydrophobic material and potentially minimize these issues. The purpose of this work is to assess the durability of a low plasticity clay soil treated with a chemical admixture by evaluating changes in physical and mechanical behavior when subjected to alternating cycles of wetting and drying. Volumetric change, water content change, and mass loss were measured at the completion of each one of up to twelve wetting and drying cycles. Unconfined compression tests were performed after select cycles to assess changes in mechanical properties. Tests were also performed on specimens stabilized with Type I/II portland cement for comparison. It was found that the specimens with chemical admixture treatment survived a full twelve cycles of wetting and drying. The volume changes of the specimens were small (±2 %) and there was no apparent reduction in strength. The chemically stabilized soil retained its physical and mechanical properties in a manner comparable to cement stabilization of the same soil. These results suggest that the CAT produces a sufficiently stable material when subjected to alternating wetting and drying conditions and has potential applications in improving long-term performance of unpaved roads.