Using recovered glass as construction aggregate feedstock

Abstract

The success of recycling collection programs has resulted in an over-supply of broken glass, or cullet, in many parts of the country. To open the construction aggregate market, a multistate and industry evaluation of glass as construction aggregate was conducted. The study defines the suitability of cullet as a construction aggregate in terms of its engineering performance, environmental impact, cost comparability with natural aggregates, and safety in handling. The analysis concludes that glass, as an aggregate, is strong, clean, safe, and economical. From an engineering standpoint, cullet appears to be an excellent supplement or replacement for natural aggregates in many construction applications. Comprehensive tests were performed for specific gravity, gradation, workability, durability, compaction, permeability, thermal conductivity, and shear strength. The effects of debris level, cullet content as a percentage of aggregate, and cullet size were also investigated. When cullet is compacted to a dense state, the material is rigid and strong. The test data indicate that under normal working stresses, the moduli and shear strength of the cullet samples are similar to those of natural aggregate. In the case of 1/4-in. minus cullet, adding cullet to the natural aggregate can even increase the rigidity and strength. Compaction curves tend to become flatter as cullet content increases, implying that the maximum dry density is relatively insensitive with respect to moisture. From a construction standpoint, this means that the material can be compacted even in wet weather.