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

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.