Experimental study on mechanical properties of lightweight concrete containing recycled thermostone and steel fibers

Lightweight structures as well as recycling demolition materials as construction materials offers environmental and economic advantages by protecting raw materials and reducing costs of construction. This paper deals with the influence of partial replacement of conventional coarse aggregate (natural gravel) with recycled coarse aggregate (crushed thermostone) on mechanical properties of the resulted lightweight concrete. In addition, the effect of incorporating steel fiber into lightweight concrete is also studied. Seven concrete mixes were adopted with various replacement ratio of coarse aggregate (25%, 50% and 75%) and steel fiber volumetric ratio (0.2%, 0.4% and 0.6%). Results show that replacement ratio of 25% or more give structural lightweight concrete with densities in the range between 1600 – 2100 kg/m3, compressive strength up to 23.73 MPa (74.01% of reference concrete), tensile strength up to 2.38 MPa (68.78% of reference concrete) and modulus of rupture up to 5.08 MPa (70.45% of reference concrete). The reductions in tensile strength and modulus of rupture of lightweight concrete can be overcome by incorporating steel fibers. In contrast, slight or no effect can be observed for steel fibers on density and compressive strength of lightweight concrete.