Corrosion of Glasses and Expansion Mechanism of Concrete Containing Waste Glasses as Aggregates

Abstract

Expansion and cracking of portland cement concrete containing glass aggregates have been known for decades. Traditional alkali-silica reaction and expansion mechanisms are being used to explain the reaction and expansion mechanisms of cement concrete containing glass aggregates. This paper reviews glass chemistry, alkali-silica reaction mechanism, expansion of concrete containing glass aggregates, and microstructure of the interfacial transitional zone between cement paste and glass particles. Analysis of these published results indicates that the formation of expansive sodium-calcium silicate hydrate (N-C-S-H) gel around glass particles in concrete results from the dissolution and precipitation of soda-lime glass in high pH environments and not from the reaction between glass particles and the alkalis in cement. The corrosion of soda-lime glass and formation of N-C-S-H can happen when the pH of the pore solution is greater than 12 regardless of the presence of alkali ions. Thus, the expansion of concrete containing glass aggregates is different from that caused by traditional alkali-silica reaction. The presence of moisture and high pH (>12) are the two necessary conditions for concrete containing glass aggregates to expand.