The invention is an improved cementitious mixture used to form structural components that are strong, lightweight, heat and fire resistant, and very economical to produce. The material includes a mixture of cement, water, ribbon-like virgin polyethylene strips and aggregate materials. The aggregate preferably includes recycled industrial waste products. Examples of these industrial wastes include shredded tires, wood by-products, waste coal combustion by-products, recycled waste gypsum products, recycled industrial foundry sand, and waste foam products such a Styrofoam. This new cementitious material is strong and lightweight. It has a lower thermal conductivity than conventional concrete and therefore improved insulative properties. The use of industrial recyclables not only enhances the performance characteristics of the components made from this material but aids in maintaining the environment by providing a practical use for industrial waste.