The ASR mechanism in concrete and the influence of lithium in mitigating it: A critical review

Abstract

Alkali Silica Reaction (ASR) which is most familiarly known as ‘Concrete cancer ‘ is a serious trouble in concrete which has been a major challenge for all the researches. An alkali silica gel is formed when the reaction occurs between alkaline solution (OH–, Na+, K+ ions) and silica present in the aggregates. This gel sucks up adequate amount of moisture, it will enlarge and this is the cause of the cracks. This process is called “Alkali Silica Reaction”. ASR requires four vital conditions. Presence of silica in aggregates, existence of OH– ions in the alkaline solution of concrete, presence of dissolvable Ca, entry of moisture is the four vital condition. It can create significant cracking in concrete and results in various negative impacts on expansion, compressive strength, tensile strength, modulus of elasticity, fatigue and shear strength and as a consequence crucial structural complication can occur, which can even vigor the destruction of that specific structure. Elgeseter Bridge is one such example for that damage. Since it is a critical trouble, taking measures to mitigate them is indispensable. Various mitigating measures like limiting the alkali content of cement, limiting reactive silica content of the cement are taken. However, due to the dwindling availability of good performance aggregates, using lithium composites as an admixture to concrete mixes is one such technique to minimize this destructive reaction. The reaction between the alkalis and aggregates are reduced by altering chemical constitution of reaction products, damaging expansivity are minimized due to the presence of lithium ions. Thus, this paper gives detailed review about requirements of ASR, mechanism of ASR, their damages, their preventive measures, role of lithium in mitigating ASR and also about their various advantages.