Can the R3-test be used as a rapid screening test for the ASR mitigation potential of calcined clays?

Alkali-silica reaction (ASR) is a known concrete deterioration mechanism leading to substantial reconstruction costs each year. An efficient way to enhance the resistance of concrete against ASR is the addition of supplementary cementitious materials (SCMs). Calcined clays present an alternative to common pozzolanic SCMs, because of their worldwide availability and their promising pozzolanic reactivity. In this study, we investigate the relationship between the pozzolanic reactivity of calcined clays and their ASR mitigation potential as SCMs in concrete. For this, the pozzolanic reactivity of three calcined clays, with various aluminum contents, was determined by using the R3 test. In addition, concrete prisms were prepared with Borosilicate glass as reactive aggregate and the three calcined clays replacing 10 wt% of plain Portland cement. After curing the prisms at 20 °C for 28 days, they were stored over water at 40 °C. The prism expansion was measured to determine the ASR mitigation potential of the three calcined clays. The microstructure of the prisms was investigated after 140 days of exposure by polarization microscopy and electron microprobe-WDX. The results show a correlation between the pozzolanic reactivity of the calcined clays determined by the R3 test and their ASR mitigation potential in concrete. This study presents a preliminary proof-of-concept, which could serve as a basis to develop an early screening method for the ASR mitigation potential of calcined clays before performing time consuming and costly ASR performance tests. Currently, additional ASR testing regimes are under investigation, with the aim to validate this correlation.     «

Alkali-silica reaction (ASR) is a known concrete deterioration mechanism leading to substantial reconstruction costs each year. An efficient way to enhance the resistance of concrete against ASR is the addition of supplementary cementitious materials (SCMs). Calcined clays present an alternative to common pozzolanic SCMs, because of their worldwide availability and their promising pozzolanic reactivity. In this study, we investigate the relationship between the pozzolanic reactivity of calcined...     »