Research Project Summary Information
Precast Concrete Walls Using Recycled Products:Precast Concrete Walls(ST4710-1)
Columbia University research showed that it is technically feasible to replace a portion of the sand and cement in concrete blocks with recycled glass. Further, the University determined the economic scenarios under which this approach would be viable. Based on its favorable findings, Columbia is extending the use of this technology to precast concrete wall panels for residential basement foundations and architectural applications (e.g., curtain walls). In addition to incorporating recycled glass, Columbia will also evaluate using recycled carpet fibers in the panels, to measure the potential increase in R-value in the final wall panel.
Columbia will evaluate the technical and economic feasibility of using recycled glass and carpet fibers in precast-concrete wall panels for residential and commercial buildings. Columbia intends to conduct a literature survey on the use of recycled glass and carpet fibers in building products, as well as research recycled-carpet fiber-supply issues and evaluate the thermal properties of carpet fiber. It will test concrete sample mixtures containing recycled glass and carpet fibers, as well as optimize them for mechanical, thermal and durability characteristics. Finally, it will identify any manufacturing process changes necessary to produce precast-concrete wall panels with recycled glass and carpet fibers, and then manufacture and test full-size prototype wall panels for commercialization.
Adding recycled carpet fibers to wall panels could increase the R-value of the resulting panels between 10% and 15%. Furthermore, the approach could create a new beneficial use for the 225 million pounds of carpet fiber and 490 million pounds of recycled glass that are discarded every year in New York State.
Columbia succeeded in developing a concrete mixture, containing recycled carpet fibers, that is suitable for precast basement foundations. Columbia also developed techniques to produce concrete samples containing recycled glass to yield architectural curtain walls that emulate granite, as well as other aesthetic finishes that cannot be achieved with natural materials. Columbia found that most recycled carpet fibers are not hollow as originally believed, because of changes in DuPont's recycling program. The researchers determined that adding recycled carpet fibers to concrete decreased thermal conductivity by 30%, but that the drop was not big enough to significantly increase overall thermal resistance of an entire foundation wall assembly for a residential building. Adding this recycled material not only did not significantly change the concrete's strength, but it provided the benefit of controlling cracking.
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