Colour-stability analysis for estimation of deterioration in concrete due to chemical attack

Abstract

Inaccessibility and subjectivity in damage evaluation during visual inspection may often lead to faulty assessment of concrete. Digital imaging tools can be used to identify and quantify the extent of distress due to deteriorating agents on concrete. Structures subjected to environmental degradation manifest deterioration in terms of changes in surface characteristics. It is strongly believed that there lies a co-dependency between the extent of deterioration and the reduction in the mechanical and durability performance. In the present study, digital image analysis technique, namely Colour-Stability Analysis (CSA), has been performed on cube samples of 30 MPa grade concrete, immersed in acid solutions (HCl, H2SO4), chloride (NaCl) and sulphate (MgSO4) at 5% concentration, exposed for various periods of 3, 7, 14 and 28 days, after the end of the requisite 28-day curing period. The CSA is conducted in CIE-LAB colour space as it is device-independent and represents the human perception of colour. The colour profiles of the deteriorated surfaces before and after immersion in the above reagents for 3, 7, 14 and 28 days have been quantified. The successive and relative differences in the surface colour profiles for respective reagent-immersion and exposure conditions have been computed and analysed. The current study revealed the influence and mechanism of various reagent’s impact on the deterioration of concrete surface with time and the same is quantified. The correlation between the extent of damage in concrete in terms of change in colour profiles, residual strength and durability is established.