Utilizing Coal Fly Ash and Recycled Glass in Developing Green Concrete Materials.

摘要

The environmental impact of Portland cement concrete production has motivated researchers and the construction industry to evaluate alternative technologies for incorporating recycled cementing materials and recycled aggregates in concrete. One such technology is based on using pulverized glass as sand or pozzolan. Currently in the United States more than 600,000 tons/year of recycled glass bottles are stockpiled due to prohibitive shipping costs from recycling locations to glass melting factories. This project demonstrates the potential use of this waste material along with fly ash (another industrial byproduct with landfill rate of 42.4 million tons/year) in developing durable and environmentally positive concretes that can be used for various transportation applications. Toward this objective, the project included two main tasks. In the first task, the deleterious alkali-silica reaction (ASR) induced by the use of silicate glass aggregates was mitigated via the use of fly ash. Mixtures were prepared using one of six different fly ashes. The main objective of this task was to better understand the mechanisms by which fly ash mitigates ASR and to identify factors that most significantly determine fly ash effectiveness against ASR. Through a combination of advanced analytical measurements and numerical simulations, it can be concluded that fly ash is effective against ASR by (a) reducing the alkalinity of pore solution by alkali binding, (b) reducing the mass transport in concrete, (c) improving the tensile strength of concrete, and (d) reducing the aggregate dissolution rate by reducing the concentration of OH-ions per unit surface area of siliceous aggregates.