High-volume fly ash system: the concrete solution for sustainable development
The challenge for the civil engineering community in the near future will be to realize projects in harmony with the concept of sustainable development, and this involves the use of high-performance materials produced at reasonable cost with the lowest possible environmental impact. Portland cement concrete is a major construction material -worldwide. Unfortunately, the production of portland cement releases large amounts of CO2 into the atmosphere, and because this gas is a major contributor to the greenhouse effect and the global warming of the planet, the developed countries are considering very severe regulations ‘ and limitations on the CO2 emissions. In view of the global sustainable development, it is imperative that supplementary cementing materials be used to replace large proportions of cement in the concrete industry, and the most available supplementary cementing material worldwide is by ash, a by-product of thermal power stations. To considerably increase the utilization of fly ash that is otherwise being wasted, and to have a significant impact on the production of cement, it is necessary to advocate the use of concrete that will incorporate large amounts of fly ash as a replacement for cement. Such concrete, however, must demonstrate performance comparable to that of conventional portland cement concrete, and must be cost effective. In 1985, CANhlET developed a concrete incorporating large volumes of fly ash that has all the attributes of high-performance concrete, that is, one that has excellent mechanical properties, low permeability, superior durability, and that is environmentally friendly. This paper gives an overview of the properties of this type of concrete that is believed to be a very promising alternative for the industry seeking to meet the sustainable development objectives.