A study of deterioration of cement paste due to acid attack using X-ray computed micro-tomography

Cementitious materials are highly vulnerable to rapid and serious deterioration in aggressive acidic environments. The aim of this paper is to understand the microstructure deterioration of cement paste due to acid attack using the non-destructive technique called X-ray computed micro-tomography (micro-CT). To investigate this deterioration, an accelerated static immersion based leaching test with periodic abrasive action was performed on cement paste specimens of size 10 × 10 × 60 mm, prepared using ordinary Portland cement with a water-to-cement ratio of 0·40. After 28 d of initial curing in saturated lime water, specimens were exposed to 1% sulfuric, 1% hydrochloric, 0·5 M acetic and 0·5 M citric acid solutions for a maximum period of 6 weeks. X-ray micro-CT was used for imaging the deteriorated specimens to investigate the changes in microstructure. Various parameters related to degradation were also deduced based on the image analysis performed on the CT images in order to evaluate the performance of the cement paste in various acid solutions. Parameters such as altered depth/area could be considered as primary indicators of attack, which can be best captured and analysed using X-ray CT.