Title: Chemical Reactivity Assessment of Glass Powder in R³ Method Synthetic Concrete Pore Solution by Accelerated Solubility Testing

Author(s): Wena de Nazaré do Rosario Martel, Josée Duchesne, and Benoît Fournier

Publication: Symposium Paper

Volume: 362

Issue:

Appears on pages(s): 1006-1032

Keywords: chemical dissolution, pozzolanic reactivity, recycled glass powder, R³ method, supplementary cementitious materials, synthetic concrete pore solution

DOI: 10.14359/51742026

Date: 6/18/2024

Abstract:
Due to its predominant soda-lime composition, most post-consumer glass processed by recycling facilities would be classified as high-alkali pozzolanic glass powder (GP). In cementitious matrices, the intrinsic alkaline pore solution induces the dissolution of both silica and alkali ions. Therefore, the GP can potentially induce two similar reactions in concrete: either a deleterious alkali-silica reaction or a pozzolanic reaction. The equilibrium of the pore solution will determine which reaction will prevail in the long term. To understand the chemical stability of GP in a cementitious system, the evolution of the solubility of key elements in an alkali-rich synthetic pore solution was studied as a function of reaction time, particle size, presence of Ca(OH)₂ and CaCO₃, and binder/solution ratio (B/S). The solution was based on the R³ method, which consists mainly of lab-grade chemicals such as KOH and K₂SO₄. Although the chemical equilibrium seems to be fully reached in the first hours of hydration, the main products, such as C-S-H, are unstable because the alkali leaching/uptake in the C-S-H chains is dynamically evolving. The experiments show that both C-S-H precipitation and alkali leaching rates increase with increasing B/S ratio and decreasing particle size, and are directly related to the presence of calcium in the solution.