Performance of recycled soda–lime glass powder in mitigating alkali–silica reaction

Abstract

Recycled soda–lime glass powder (SLGP) is a valuable supplementary cementitious material. However, it has a high alkali content, and its effectiveness in mitigating the alkali–silica reaction (ASR) is uncertain. In this study, the ASR performance of SLGP was evaluated using the accelerated mortar bar test (ASTM C 1567) and the concrete prism test (ASTM C 1293). It was determined that a sufficient dosage of SLGP can mitigate ASR according to ASTM C 1567, and that finer SLGP is more effective. Meanwhile, the 2-year concrete prism test showed that the same type, fineness and dosage of glass powder as tested by C 1567 does reduce ASR, but not sufficiently and below the ASTM failure threshold. Pore fluid composition monitoring revealed that SLGP, over time, serves as a net contributor to the pore solution alkalinity, but these alkalis are released slowly. Overall, SLGP can reduce ASR, albeit insufficiently and temporarily. This ASR reduction is likely through a combination of reduced pore solution pH at early ages (due to cement dilution) and reduced portlandite content and transport properties at later ages (due to pozzolanic reaction). Long-term ASR testing is necessary to determine if and at what dosage a glass pozzolan may be able to control ASR sufficiently.