Document Type : Review Article
PhD Student in Energy Systems _Energy and Environment, Department of Environmental Engineering, University of Tehran, Tehran, Iran
After water, concrete is the most widely used material in the construction industry due to its special properties. However, the Portland cement production process has major environmental disadvantages, resulting 8% of global CO2 emissions (4 billion tons per year). Therefore, the need to use an alternative to Portland cement seems necessary. In recent years, geopolymer has been proposed as a new and environmentally friendly cement agent to replace Portland cement. Geopolymers are chains or networks of mineral molecules that are attached by covalent bonds, and are composed of a combination of two main parts, the aluminosilicate source (by-products) and the alkaline activating solution. They can exhibit outstanding technical properties such as high mechanical strength, good chemical resistance, or high thermal resistance. The use of PFA powdered fuel ash from coal-fired power plants to replace conventional OPC Portland cement has become quite common. Quantifying the environmental benefits of using these materials is difficult. The LCA life cycle assessment method, which is internationally standardized by the ISO14040 series, can be used to quantify the environmental impacts of products and processes. In this review article, the use of LCA method for comparing the environmental impact of OPC precast concrete products with PFA precast concrete products is shown. The four stages of LCA are described in detail and the results of determining the material as a by-product or waste are discussed. An overview of other LCA studies conducted for environmental applications is also provided to determine which of the impact assessment methods is most widely used.