Role of the nature of reaction products in the differing behaviours of fine glass powders and coarse glass aggregates used in concrete

This paper deals with the incorporation of glass cullet in cement-based materials. The aim is to help understand the differing behaviours observed depending on the particle size of the glass: the use of fine powders usually improves the concrete properties due to pozzolanic reaction, while coarse aggregates are generally detrimental for concrete due to alkali-silica reaction. It is shown that the lack of swelling of gels resulting from the reaction of glass fines can be partly due to the nature of these gels. The comparative investigation carried out on reaction products resulting from glass grains of various sizes, in the presence of both portlandite Ca(OH)₂ and C₃S (tricalcium silicate: 3CaO · SiO₂), has shown that glass aggregates produce detrimental gels while glass fines produce gels that help to improve concrete properties.