Advantages of Using Low Alkali Cements and Industrial Waste Materials in Prevention of Alkali-silica Reaction in Concrete

Manufactured cement has to comply with the requirement of containing less than 0.60% sodium oxide equivalent (Na2Oeq) to meet the standard alkali content specified by codes of practices worldwide, such as ASTM C150 [1]. This limit has been adopted since the 1940s for the purpose of preventing deleterious expansion due to alkali-silica reaction (ASR), which has the potential to compromise the mechanical performance of concrete structures in service. Limiting the amount of sodium and potassium alkalis in cement is one method of lowering the alkali content [2]. However, raw materials used to manufacture cement may often contain alkali contents exceeding this limit. These raw materials are thus often discarded for use in cement manufacture. Another challenge to contend with is the need to conserve naturally occurring resources. Therefore, alternative solutions proposing the use of industrial by-products raw materials need to be considered [3]. The use of supplementary cementitious materials (SCMs), like fly ash and slag, generated as industrial waste can be recycled in blended cements [4], which provides a viable option for lowering the alkali content of cement permitting the use of raw materials that would otherwise be discarded to landfill. This paper reviews the advantages of using SCMs to lower the alkali content of cement and allow a wider range of raw materials to be employed in cement manufacture whilst conserving natural resources and decreasing the CO2 emissions associated with cement manufacture [5].