Abstract
Use of fly ash by percent replacement of cement is considered as one of the most economical and effective methods for mitigating alkali-silica reaction (ASR) related distress in the concrete. However, fly ash has been proven to be somewhat variable in its effectiveness in inhibiting alkali-silica reactivity, principally because its composition depends on the coal properties from which it is derived. Typically class C fly ashes are not as efficient as class F ashes due to their higher calcium oxide content. Nevertheless, it is important to find out whether the lime content in the fly ash has linear effect on ASR distress mitigation and if the dosage of fly ash is more influential than type of fly ash. This research conducted extensive testing with nine different types of fly ashes with three in each category of fly ashes, class C, class F, and intermediate class. The results indicated that the effect of increased dosage of fly ash on ASR mitigation is linear for both low-lime and high-lime fly ashes and the dosage effect is more significant with rapid effect with high-lime fly ashes compared to low-lime fly ashes.
Highlights
The alkali-silica reaction (ASR) related distress is a matter of great concern to the concrete industry and regarded as second most deterioration issue after corrosion
This study only focuses on fly ash which is the most commonly used additive to mitigate ASR distress
It appears from these results that low-lime and intermediate-lime fly ashes were effective in controlling ASR expansion; highlime fly ashes were not effective in controlling ASR expansion
Summary
The alkali-silica reaction (ASR) related distress is a matter of great concern to the concrete industry and regarded as second most deterioration issue after corrosion. ASR-induced expansion will occur only if the following three conditions are met: (1) the aggregates in the concrete mixture contain reactive forms of silica, (2) there are sufficient alkalis; alkali content in the cement is greater than 0.60%; and (3) sufficient moisture is available in the hardened concrete (above 75% RH within the concrete). Preventing any of these three conditions from being a reality is sufficient to prevent deterioration and is often the emphasis of prevention strategies. ASTM C150/C150 M-15 [1] designates cements with more than 0.6 percent of Na2O as high-alkali cements
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