Image Processing Techniques for Assessment of Deterioration in Recycled Aggregate Concrete Due to Chemical Attack

Replacement of natural aggregate with Recycled Aggregate is one of the key steps to account for sustainability in structures. Recycled aggregate has higher water absorption, varied shape and surface texture due to the presence of adhered mortar content and a weaker interface. In the present study, the durability of Recycled Aggregate Concrete (RAC) is estimated by subjecting the concrete specimens to different species of chemicals. The visual examination of colour variation gives a preliminary insight into the damage caused and the chemicals responsible for the damage. The visual examination can be accompanied by digital image processing techniques to quantify the deterioration caused and the extent of damage. In the present study, Natural Aggregate Concrete (NAC) and Recycled Aggregate Concrete (RAC) specimens are subjected to the attack of four chemicals viz., HCl, H2SO4, NaCl and MgSO4 after the required curing period. These specimens are subjected to 28 days period of chemical exposure. The images of the specimens are captured and analysed using Image-J software. The deterioration is quantified in the HSI colour space from the RGB values of image. The Durability Loss Factor of the specimens is evaluated from mass loss, diagonal loss and strength loss of concrete. From the results obtained, it can be observed that the specimens exposed to H2SO4 show a greater variation of colour due to higher deterioration, followed by HCl, MgSO4 and NaCl respectively. The Recycled Aggregate Concrete exhibited greater deterioration due to decrease in the quality compared to conventional concrete. The Durability loss factor is maximum for specimens exposed to H2SO4 compared to other chemicals indicating a greater deterioration. This reinforces the results obtained from image analysis. The image analysis can hence, form an effective non-destructive and visual examination method of estimating concrete deterioration.