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Meyer and several colleagues at New York's Columbia University recently conducted research to find methods to use waste glass as an aggregate for concrete. Substituting waste glass for natural aggregates in concrete has so far been unsuccessful because of the problem of alkali-silica reactions (ASR). The researchers also expected that glass aggregate would affect concrete strength.

To study the effect of glass particle size on mortar bar expansion, they replaced 10% of the aggregate in concrete samples with an equal amount of crushed clear glass of various sizes. Grinding glass finely enough appears to minimize ASR-induced damage.

In regard to whether glass color has any effect on the expansion as measured in the ASTM C 1260 test, one type of amber glass caused a clear reduction in expansion. But bars with a type of green glass displayed less expansion than even the reference mortar bars.

The article also includes information about three glass aggregate applications with immediate commercial potential: concrete masonry block, paving stones, and architectural/decorative concrete. In addition, tabular data indicates that glass aggregate additions to concrete block mixes do not adversely affect concrete strength.