PROPERTIES OF GLASS CONCRETE CONTAINING RECYCLED CARPET FIBERS

Carpets are a major component of today’s waste streams, totaling an estimated 3.5- 4 billion pounds in the US in 1996, which corresponds to 1 % of all solid waste by weight or 2 % by volume. More recent statistics are not likely to be less. In response to federal regulations which require the producers of carpets and carpet fibers to take back old carpets, a number of recycling strategies are now being explored. At Columbia University, a major study to evaluate the feasibility of using post-consumer glass as aggregate in concrete has been expanded to investigate the suitability of large quantities (up to 20 % by weight) of recycled carpet fibers in concrete products. The expected benefits were to be threefold: first, the fiber reinforcement was expected to improve the mechanical properties of the concrete. This expectation was fulfilled to some extent, although the effect was less than when virgin fibers were used. Second, it was hoped that large quantities of recycled reportedly hollow carpet fibers would enhance the thermal properties of the concrete by increasing the R-value. Unfortunately, only modest improvements were observed. Finally, the recycling of used carpet fibers is a contribution to sustainable development, as value is added to a material that otherwise would constitute an environmental burden