Durabilità dei calcestruzzi alleggeriti con aggregato di vetro espanso

The progressive increase of concrete production in the last decades has lead to a substantial exploitation of resources and an increase in pollutant emissions. However, if on the one hand the concrete has a significant impact on the environment, on the other hand it offers interesting opportunities towards a sustainable development. In fact, since the 1940s, different residues of industrial processes were recycled in the concrete (for example, carbon fly ash, blast furnace slag and silica fume as a partial replacement of Portland cement). Other waste materials are compatible with the concrete technology; in particular, glass is potentially usable in the form of expanded aggregates in order to reduce the density of concrete. However, the use of expanded glass in the concretes poses some concern about durability, because of its poor stability in alkaline environments. The paper presents the results of a research aimed at studying the use of expanded glass as lightweight aggregate in the concrete. Expanded glass particles were characterized in terms of alkali-aggregates reaction, density, absorption and electron microscopy. The replacement of the fine fraction of aggregates with expanded glass has allowed to cast lightweight concrete with 28-day compressive strength of about 25 MPa on which the long term stability in wet environments of expanded glass aggregates was investigated.