Keywords: building materials, concrete, cement
Summary:Concrete is a composite building material consisting of a binder (typically, Portland cement), coarse and fine aggregates (rock and sand), water, and various chemical and mineral admixtures to address specific performance related requirements. The cement industry is the most energy intensive of all manufacturing industries. Currently, a state of the art “dry process” cement production facility utilizes approximate thermal energy of 3,500 MJ and electrical energy of 110 kWh to produce a tonne of Portland cement. This tonne of Portland cement is then used to produce, typically, 3.5 m3 of Portland cement concrete. In a typical concrete office building floor of ~ 25,000 ft2, there would be approximately 407 m3 of concrete containing approximately 110 tonnes of Portland cement. Further, production of one tonne of cement produces approximately 900 kg of carbon dioxide. Given that the quantity of concrete used in construction is greater than any other material and that there’s not a lot to be done with water and aggregates, it’s reasonable to look to innovations in the binder to reduce the energy intensity and to enhance the performance of concrete. Such innovations involve the use of industrial byproducts, and natural mineral materials requiring low energy processing, not contributing to carbon dioxide emissions due to physical or chemical transformations of materials. These innovations provide multiple advantages and, unlike some other proposed and researched materials, are available today. Further, concrete can be engineered and produced with performance characteristics beyond those that are traditionally associated with it (compressive strength, flexural strength, modulus of elasticity). Such characteristics include permeability, unit weight, tensile strength, protection of reinforcing steel and others. Finally, because sustainability of building materials also includes (or should include) maximizing service life and capability for adaptive reuse, design for and prediction of service life and mechanisms of deterioration as well as early detection, mitigation, and prevention of such deterioration is a major research endeavor. This ubiquitous and ancient material can, with today’s technology, perform in ways not possible even 50 years ago and can do so with dramatically less impact on the environment.