ASR Resistance of Ground Bottom Ash-Based Alkali-Activated Concrete and the Prospect of Using MCPT for the Evaluation

The decline in fly ash and blast furnace slag production motivated us to look for alternative unconventional aluminosilicate binders such as ground bottom ashes, volcanic ashes, and calcined clays as precursors for producing alkali-activated concrete (AAC). The science of developing mechanical and durability properties of so-called nontraditional precursors-based alkali-activated systems remains less investigated. The study explores the most decisive durability parameters of such systems, alkali-silica resistance (ASR) of different ground bottom ashes (GBA)--based alkali-activated concretes (AAC). Three ground bottom ashes with distinct oxide compositions and amorphous contents are considered. The activator solution used had a silica modulus of 1.25 and a Na₂O content of 9.25% by mass of the binder. A solution-to-binder ratio of 0.6 and a binder-to-total aggregate proportion of 35:65 was used. Four different aggregates with varying degrees of reactivity, as established by ASTM C1260, were used. Miniature concrete prism test (MCPT), as specified by AASHTO T 380 for OPC, is used for detecting ASR in the AAC. AAC and OPC prisms are prepared, cured, and exposed to 1N NaOH solution per the code recommendations. The length change of four replicates is monitored for 56 days at designated intervals. All AAC mixtures produced significantly low expansions compared to OPC counterparts, irrespective of GBA compositions or aggregate combinations. We conducted microstructural investigations to validate the expansion results and understand the mechanisms of ASR in GBA-based alkali-activated concrete.