Deterioration mechanisms and physicochemical changes induced by silage environment on ternary and alkali activated binders and concrete

The performance of the specimens was evaluated by recording visual damage, mass loss, and compressive strength loss against reference specimens stored in water. In addition, paste specimens exposed to outdoor laboratory conditions as above were used to study the evolution of microstructural properties using XRD, TGA, FTIR, and SEM-EDS. The findings show that decalcification and carbonation are the significant changes occurring to the ternary and activated GGBS systems due to effluent exposure.

The activated fly ash and calcined clay systems, although of lower strength grade, were not affected by the exposure and gained strength, whereas the other binder systems recorded a loss in strength of 6-32%. Fly ash and calcined clay systems showed changes to aluminium and iron minerals, respectively, closer to the exposure surface. However, the depth to which these metals were removed from are nominal in comparison to Ca dissolution/leaching in other blends.<br><br>Based on the findings from the above studies, AAFA and AACC concrete specimens exhibited mass and strength gains under exposure to silage effluent.

This contrasts with earlier studies conducted by the research team, where AAFA mortar specimens showed mass and strength losses when exposed to acetic and lactic acid solutions. This discrepancy suggests that other components present in silage effluents such as chlorides, sulfates, and phosphates—also play significant roles in influencing the performance of these alkali-activated systems.<br>In stage 2, the performance of selected three blends, viz., a ternary, an AAGGBS, and AAFA systems against combined organic acid and salt attack was investigated.

Four combinations were studied: lactic acid–chloride, lactic acid–sulfate, lactic acid–phosphate, and acetic acid–sulfate. <br>In conclusion for whole project, alkali activated systems performed superiorly in silage and its component acid/salt environments. Salts have significant influence on the deterioration behaviour and therefore should be considered alongside mineral acids in future durability studies.<br><br><i>Thesis is embargoed until 31 December 2026.</i><br><br><br>