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Each year, about 730 million tons of bottom ash is generated in coal fired power plants worldwide. This by-product can be used as partial replacement for Portland cement, favoring resource conservation and sustainability. Substantial research has explored treated and processed coal bottom ash (CBA) for possible use in the construction industry. The present research explores using local untreated and raw CBA in mitigating the alkali–silica reaction (ASR) of reactive aggregates in concrete. Mortar bar specimens incorporating various proportions of untreated CBA were tested in accordance with ASTM C1260 up to 150 days. Strength activity index (SAI) and thermal analysis were used to assess the pozzolanic activity of CBA. Specimens incorporating 20% CBA achieved SAI greater than 75%, indicating pozzolanic activity. Mixtures incorporating CBA had decreased ASR expansion. Incorporating 20% CBA in mixtures yielded 28-day ASR expansion of less than the ASTM C1260 limit value of 0.20%. Scanning electron microscopy depicted ASR induced microcracks in control specimens, while specimens incorporating CBA exhibited no microcracking. Moreover, low calcium-to-silica ratio and reduced alkali content were observed in specimens incorporating CBA owing to alkali dilution and absorption, consequently decreasing ASR expansion. The toxicity characteristics of CBA indicated the presence of heavy metals below the US-EPA limits. Therefore, using local untreated CBA in concrete as partial replacement for Portland cement can be a non-hazardous alternative for reducing the environmental overburden of cement production and CBA disposal, with the added benefit of mitigating ASR expansion and its associated costly damage, leading to sustainable infrastructure.

Sugarcane bagasse ash (SBA) is a supplementary material widely used around the world for improving mechanical and durability properties of concrete. Main aim of this study was to examine the potential of SBA for controlling alkali-silica reaction (ASR) in concrete incorporating reactive aggregates. SBA and reactive aggregates were acquired from local industry and quarry. Mortar bar specimens were cast to investigate various dosages of SBA (i.e., 10, 20, 30, and 40% by cement weight) for mitigating the alkali-silica reactivity expansion as per ASTM C1260. Petrography analysis of aggregates revealed the presence of deleterious minerals, which are prone to ASR. Strength activity index and thermal analysis results confirmed the pozzolanic activity of SBA. Mortar bar results showed 20 and 40% decrease in ASR expansion for specimens incorporating 10 and 40% of SBA by cement weight, respectively. Moreover, scanning electron microscopy analysis showed no sign of cracks due to ASR for specimens incorporating SBA. The improved behavior of specimens with SBA addition was due to alkali absorption and dilution process leading to low CaO/SiO 2 ratio, confirmed through energy disperse X-ray spectroscopy. Therefore, it can be envisioned that full-scale implementation of SBA addition in concrete mixtures could mitigate land filling of this by-product and lead toward the development of eco-friendly and sustainable technique for controlling the ASR associated damages in concrete structures. K E Y W O R D Saggregates, alkali-silica reaction, durability, mortar bar, sugarcane bagasse ash

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