Service Life Prediction and Use of Green Corrosion Inhibitors for RCC Structures

Abstract

The rapid growth in the construction industry has led to the development of mega structures. These structures developed the necessity of introducing reinforced cement concrete. However, using steel rebars as reinforcement results in a major durability issue; named as corrosion. To surmount this, ample amounts of materials as well as techniques have been adopted and are developing and being researched upon. Inhibitors are an example of them. Commercially available inhibitors are responsible for environmental hazards. Thus, the recent studies are focusing on green corrosion inhibitors. They are produced from agro-forest products, making them a feasible and viable economical solution. The deterioration of material happens due to the destruction of the passive layer present around the rebars due to corrosion. This leads to formation of rust around the bars, which eventually cracks the concrete cover. Treating the RCC structures with inhibitors slows down the corrosion rate responsible due to carbonation and chloride attack. In this study, Azadirachta indica (Neem leaves) and Bermuda Grass are used for corrosion resistance. The extraction is carried out using the Hot-reflux method and Boiling technique. The amount of antioxidant in the extract is measured by performing FT-IR. RC specimens are prepared to investigate the corrosion parameters and analyze their performance by performing tests such as Rebound hammer test, Accelerated corrosion test, Accelerated Carbonation test, Volhard method of Analysis, Resistivity meter and Half-cell potential. Furthermore, a commercially available inhibitor named as Conplast CN is also used to compare the results with the green corrosion inhibitors adopted. The corrosion happens due to carbonation or chloride attack depending upon the environmental conditions. Focusing on the durability, the durability of a building is hugely affected by corrosion. Formation of Ferric hydroxide due to the corrosion process results in volume expansion of the steel bars. As said before, rust can be seen by the brown color on the rebars. This will turn them soft and start forming cracks until the concrete cover falls. Thus, it is essential to estimate the service life, so that proper maintenance and design criteria can be adopted. In this study, estimation of service life is carried out with the help of analytical models as well as software. Analytical models (Morinaga's model, Bazant's model, and Weibull distribution) are prepared using MATLAB. Also, software (Life365) is used to predict the service life of any RCC specimen. Various parameters present in the models are studied along with their effect on the corrosion rate and remaining service life. Concerning the study of the parameters, models, and software; the service life of various structural components is predicted by referring to several pieces of literature. Lastly, a comparison is done of the service life predicted by the discussed models and tools.