Efficiency of Cow Bone Ash (CBA) In Mitigating Alkali Silica Reaction (ASR) Based On Accelerated Mortar Bar Test (AMBT) In Concrete Pavements

Abstract

Nigerian roads which are predominantly flexible pavements are in a deteriorated state and requires frequent maintenance before the expiration of their design life. Rigid/Concrete pavements serves as a better alternative to flexible pavements on the long term considering their ability to contain higher traffic load, constructed over a weak subgrade, requiring little maintenance and many much benefits. Concrete pavements however are susceptible to Alkali Silica Reaction (ASR) which compromises the strength and morphological properties of the pavement. This has necessitated studies on the use of supplementary cementitious materials (SCMs) to reduce the effect of ASR and enhance the properties of the concrete pavement. The efficiency of SCMs such as Cow Bone Ash (CBA) to partially replace cement and mitigate the effect of ASR in concrete is researched in this study. This will help reduce the menace of greenhouse gas emission that results from the production of cement required for concrete pavement construction. Concrete bars of known dimensions were constructed with partial replacement of cement by CBA (0%-30%). The expansion of the concrete bars was measured on the 7th, 14th and 28th day of immersion in 1M NaOH. The concrete bars expansion values are then compared to VicRoads 610 and ASTM C1260 standards to determine the concrete reactivity classification. The study revealed that at above 15% CBA replacement levels, cow bone ash is efficient for use in rigid pavements for mitigating the effects of Alkali Silica Reaction. The regression analysis of concrete cubes expansion against percentage of CBA replacement indicates a high level of relationship between both variables. This indicates that the higher the level of CBA addition, the lower the level of concrete expansion and lower level of ASR attack in the Portland cement/rigid pavement. Recommendations on how ASR can be mitigated in new and existing structures are highlighted