Alkali-Silica Reaction (ASR) is one of the most important mechanisms of durability reduction in cement mixtures. Taking place between the reactive silica of aggregates and the alkaline elements of cement (sodium and potassium), this reaction produces a hydrophilic gel known as glass water, which swells upon absorbing water, causing significant internal pressure in the mortar. This study investigated the effectiveness of microbial calcite precipitation (MCP) with Sporosarcina pasteurii in the inhibition of ASR. The investigation was performed on the mortars made by substituting 0, 25, 50, 75, and 100% of sand aggregates with waste glass (as the extreme material causing ASR). The specimens were prepared using the accelerated mortar bar method as per ASTM C1260 and received one of the following two MCP treatments: Wet Calcite Precipitation (WCP) and Fixed Calcite Precipitation (FCP). X-ray diffraction analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were performed to study the formation of calcium carbonate precipitate, gel formation, and the nature of ASR gel compounds in control and treated specimens. Physical and mechanical properties of the mortars were measured using expansion, ultrasonic pulse velocity (UPV), and compressive strength tests. The results showed that both MCP treatments significantly reduced the destructive effects of ASR in the mortar compared to the control at the 95% confidence level. Between WCP and FCP, the former was more effective in improving UPV and expansion test results and the latter was significantly more effective in improving compressive strength. The findings showed that MCP could be an effective strategy for limiting the adverse effects of ASR in cement mortars.

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