Potential alkali silica reaction expansion mitigation of ferronickel slag aggregate by fly ash

This study investigates the potential alkali silica reaction (ASR) of ferronickel slag (FNS) aggregate, which is a by-product of nickel production. A class F fly ash was used as a possible ASR mitigation in accelerated mortar bar test (AMBT) specimens containing 50% FNS. There were visible surface cracks on the specimens using no fly ash or 10% fly ash. Use of 20% fly ash reduced expansion by 45% as compared to that with 10% fly ash. In accordance with the expansion limits of Australian Standard, the mixtures using 20 and 30% fly ash were categorized as slowly reactive and nonreactive, respectively. Thermogravimetric analysis (TGA) and microstructural observations confirmed the effectiveness of fly ash in reducing Portlandite content that reduced the ASR expansion. Therefore, the use of 20-30% fly ash as cement replacement is considered as an adequate ASR mitigating measure of FNS fine aggregate

Mitigation Effect of Waste Glass Powders on Alkali–Silica Reaction (ASR) Expansion in Cementitious Composite

The effects of different contents and particle sizes of waste glass powder on alkali–silica reaction (ASR) expansion of cementitious composite bar were investigated in this study. Waste glass powder with particle size less than 300 μm exhibits an excellent mitigation effect on ASR expansion. With larger content and smaller particle size, the mitiga- tion effect of waste glass powder on ASR expansion gradually increases. The mitigation effect of waste glass powder with particle size ranging from 38 to 53 μm and 20% by weight of cement seems relatively better than that of fly ash. When the waste glass powder content reaches 30%, the mitigation effect is still effective and almost the same as that of fly ash. However, the waste glass powder with particle size larger than 300 μm presents negative mitigation effect on ASR expansion when the replacement rate is larger than 30%. On the other hand, the waste glass powder and calcium hydroxide (CH) further react, and produce more calcium–silicate–hydrate gels, which apparently reduce the amount of CH. Moreover, the increasing content of waste glass powder results in a lower pH value in the pore solu- tion of cementitious composite