Influence of Specimen Size on the Expansion of Portland Cement Mortars Immersed in Sodium Sulphate Solution

Abstract

This paper explores the role of specimen size on the rate of length change in sodium sulphate attack. Prismatic cement mortar specimens of size cross sections 10 mm × 10 mm and 20 mm × 20 mm with length of 160 mm and standard size (ASTM C1012) of 25 mm × 25 mm × 285 mm, were continuously immersed in 50 g/l sodium sulphate solution, and the change in length was monitored periodically. The expansion was seen to be dependent on the surface area to volume ratio. Quantification of the attack using the depth of alteration in the specimens was studied by X-ray microtomography. The information from the microstructural analysis was used to assess the impact of specimen size, with a view of connecting laboratory specimens to actual structural elements in sulphate-rich environments.