Introduction 

How to meet the housing and infrastructural needs of society in a sustainable manner is, unquestionably, the most important challenge confronting the concrete industry today. Among the sustainability issues, the three major ones that are widely discussed in the published reports may be summarized as follows: 

Climate change—In many parts of the world, extreme weather patterns are occurring with greater frequency. Most scientists believe that this phenomenon is associated with the high emission rates of green-house gases, primarily carbon dioxide, the environmental concentrations of which has increased from 280 to 370 parts per million volume mainly during the industrial age (1, 2). The transportation industry and the portland cement industry happen to be the two largest producers of carbon dioxide. The latter is responsible for approximately 7% of the world’s carbon dioxide emissions. 

Resource productivity—The concrete industry is the largest consumer of virgin materials such as sand, gravel, crushed rock, and fresh water. It is consuming portland and modified portland cements at an annual rate of about 1.6 billion metric tons. The cement production consumes vast amounts of limestone and clay besides being energy-intensive. 

Obviously, large amounts of energy and materials, in addition to financial resources, are wasted when structures deteriorate or  fail prematurely which, in fact, has been the case with many recently built reinforced concrete bridge decks, parking garages, and marine structures throughout the world. Traditionally, most concrete structures are designed for a service life  of 50 years. With the advent of highperformance concrete mixtures, some structures are now being designed and built for a service life of 100 years. In the long run, sustainable development of the concrete industry will not take place until we are able to make even more dramatic improvements in our resource productivity. In this context, it should be noted that the Factor Ten Club, a group of scientists, economists and business  people have made a declaration that, within one generation, nations can achieve a tenfold increase in their resource productivity through a 90% reduction in the use of energy and materials. 

Industrial ecology—Achieving a dramatic improvement in resource productivity through durability enhancement of products is, of course, a long-term solution for sustainable development. A short-term strategy that must be pursued simultaneously is to practice industrial ecology at a larger scale than is the case today. Simply defined, the practice of industrial ecology by a manufacturing industry involves the reclamation and re-use of its own waste products and, to the extent possible, the waste products of other industries which are unable to recycle them in their own manufacturing process. 

Reportedly, over 1 billion tons of construction and demolition waste is generated every year. Cost-effective technologies are available to recycle most of the waste as a partial replacement for the coarse aggregate in fresh concrete mixtures. Similarly, industrial wastewaters and non-potable waters can substitute for municipal water for mixing concrete unless proven harmful by testing. Blended portland cements containing fly ash from coal-fired power plants, and ground-granulated slag from the blast-furnace iron industry provide excellent examples of industrial ecology because they offer a holistic solution for reducing the environmental impact of several industries.

The construction industry already uses concrete mixtures containing cement replacement materials, such as 15% to 20% fly ash or 30% to 40% slag by mass. As discussed in this paper, with conventional materials and technology, it is now possible to produce high-performance concrete mixtures containing 50% to 60% fly ash by mass of the blended cementitious material. Note that fly ash is readily available in most parts of the world. China and India, the two countries that consume large amounts of cement, together produce over 300 million tons of fly ash per year.