Abstract
Use of any recycled material helps to maintain a greener environment by keeping waste materials out of the landfills. Recycling practices also can decrease the environmental and economical impact of manufacturing the materials from virgin resources, which reduces the overall carbon footprint of industrial materials and processes. This study examined the use of waste materials such as crushed glass, ground tire rubber, and recycled aggregate in concrete. Compressive strength and elastic modulus were the primary parameters of interest. Results demonstrated that ground tire rubber introduced significant amounts of air into the mix and adversely affected the strength. The introduction of a defoamer was able to successfully remove part of the excess air from the mix, but the proportional strength improvements were not noted implying that air left in the defoamed mixture had undesirable characteristics. Freeze-thaw tests were next performed to understand the nature of air in the defoamed mixtures, and results demonstrated that this air is not helpful in resisting freeze-thaw resistance either. Overall, while lightweight, low-carbon footprint concrete materials seem possible from recycled materials, significant further optimization remains possible.
Highlights
Construction materials are increasingly judged by their ecological impact
If crushed glass is used as a substitute for fine aggregate, there is the possibility of an alkali silica reaction between the paste and the glass
Experience shows that if the recycled aggregate is cleaned, sorted, and selected properly, it can be used as an acceptable substitute for virgin coarse aggregate
Summary
Construction materials are increasingly judged by their ecological impact. The use of recycled materials for coarse and fine aggregate is being actively encouraged. Coupled with the increasing scarcity of suitable aggregate, the pressure is severe to find an acceptable replacement for virgin aggregate. Use of recycled concrete aggregate (RCA) from the demolition of old structures could be an acceptable solution [2]. There is the possibility of cement reacting with the aggregate itself. If crushed glass is used as a substitute for fine aggregate, there is the possibility of an alkali silica reaction between the paste and the glass. Experience shows that if the recycled aggregate is cleaned, sorted, and selected properly, it can be used as an acceptable substitute for virgin coarse aggregate
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