Fresh and hardened properties of self-compacting concrete was experimentally examined by replacing different percentages of cement by soft clay powder, which resulting from crushing the wastes of clay bricks. Three percentages (5%, 10%, and 15%) of cement were replaced with clay powder to study their effect on the properties of cement mortar and concrete of Grade (C35) in both fresh and hardened states. It was found that development rates of the compressive and tensile strengths for the mortar between ages of 7 to 28 days, decreased with increasing the percentage of the clay powder. Compared to the mix without clay powder, it was found that replacing (5%) from the cement causes a significant increase in the workability of the self-compacting concrete and the properties of the resulting hardened concrete such as compressive strength, tensile strength, and modulus of elasticity. While using (10%) and (15%) of the clay powder causes a significant decrease in the workability of the fresh concrete and the properties of the hardened concrete compared to mix without clay powder.
The main objective of this study is to get more information about the flexural behavior of composite reinforced concrete slabs using two layer of concrete, first layer is light weight concrete (LWC), and second layer is normal weight concrete (NWC), through an experimental tests carried out on five samples different in their details and the position of the concrete type layer within the slabs. In this study, simply supported slabs subjected to one point load were adopted. The effect of concrete grade for the (LWC) was also studied. The light weight coarse aggregate which that used in this study is the expanded light clay aggregate (LECA). Using this type of light aggregate in concrete leads to reducing the weight of composite concrete slabs about (11.4%-17.5%). In this study, one grade of NWC was used of (25 MPa), while three of grade types were adopted for LWC (25 MPa, 18 MPa, 15 MPa).