PbO-glass behavior in cement based materials

Recycled glass has already been used as concrete aggregates or cement substituted, however, its amorphous nature can promote and develop alkali-silica-reaction (ASR). ASR is definitely one of the most deleterious event that can occur in concrete: the reaction products are expansive and lead to crack formation with disruptive effects. ASR usually occurs when glass is used as sand replacement, whereas when glass is added as cement replacement pozzolan reaction takes place. However, it has been proved that glass chemical composition is a key parameter for the developing of ASR. Crystal glass with a PbO content of 26 wt% favours the occurrence of ASR also when the glass partially replaces cement. In this work, silicate glass containing different amount of PbO (from 1 to 26 %) coming from dismantled fluorescent lamps, cathode-ray tubes (CRT), and crystal house-ware glass have been studied to test their reactivity towards alkalis. All glass types have been used both as cement substitute and aggregates replacing sand. This study investigates the relation between PbO content and its potentially deleterious behavior by expansion test carried out in different experimental conditions. Moreover, through SEM-EDS analysis, an assessment of the materials is carried out. An attempt to link the behavior to the solubility and chemical reactivity of the glass is proposed. Eventually, since heavy atoms can be leached due to the high alkalinity of cementitious materials, leaching tests have been performed to test the environmental safety of these materials.