J. Electrochem. Sci. Technol., Epub ahead of print - 1 - Experimental Investigation of Electrochemical Corrosion and Chloride Penetration of Concrete Incorporating Colloidal Nanosilica and Silica fume Rishav Garg 2 , Rajni Garg 1 *, and Sandeep Singla 3 Rayat Bahra University, Mohali, India Galgotias College of Engineering & Technology, Greater Noida, India RIMT University, Mandi Gobindgarh, India ABSTRACT Enhancement of durability and reduction of maintenance cost of concrete, with the implementation of various approaches, has always been a matter of concern to researchers. The integration of pozzolans as a substitute for cement into the concrete is one of the most desirable technique. Silica fume (SF) and colloidal nanosilica (CS) have received a great deal of interest from researchers with their significant performance in improving the durability of concrete. The synergistic role of the micro and nano-silica particles in improving the main characteristics of cemented materials needs to be investigated. This work aims to examine the utility of partial substitution of cement by SF and CS in binary and ternary blends in the improvement of the durability characteristics linked to resistance for electrochemical corrosion using electrical resistivity and half-cell potential analysis and chloride penetration trough rapid chloride penetration test. Furthermore, the effects of this silica mixture on the compressive strength of concrete under normal and aggressive envi- ronment have also been investigated. Based on the maximum compression strength of the concrete, the optimal cement substituent ratios have been obtained as 12% SF and 1.5% CS for binary blends. The optimal CS and SF combination mixing ratios has been obtained as 1.0% and 12% respectively for ternary blends. The ternary blends with substitution of cement by optimal percentage of CS and SF exhibited decreased rate for electrochemical corrosion. The strength and durability studies were found in consistence with the microstructural analysis signifying the beneficiary role of CS and SF in upgrading the performance of concrete. Keywords: Corrosion, Electrical Resistivity, Half-Cell Potential, Strength, Chloride Penetration Received : 28 December 2020, Accepted : 30 April 2021 1. Introduction Durability of a cementitious structure is the ability to resist against various deterioration processes viz. chemical, weathering, abrasion etc. in aggressive environmental conditions without any adverse effect on the identity, quality & performance of the cemen- titious structure during its service life [1,2]. Many physical, chemical & electrochemical processes affect the durability of the cement mortar leading to cracking [3]. The responses inside of the cement mortar as it sets and fortifies are hard to control and this is a progressing issue in the construction business [4]. The major issue in the cement mortar at the solid- ified state is the voids and cracks furthermore, its ensuing issues because of salt silica response, which is a concoction response that causes gaps in the cement matrix. Aside from the above, penetrability of gasses through pores and small scale cracks in the cement, which prompts erosion issue in the fortification of the matrix brings on additional weakening and causes disintegration, and chemical leaching mainly due to the excess calcium hydroxide [5]. The pores present in the matrix of concrete make it vulnerable towards the inva- sion of ions in the aggressive environment. Recently, many chemical admixtures have been evaluated to play a role as supportive cementitious materials (SCMs) that Research Article *E-mail address: rajni.garg@rayatbahrauniversity.edu.in DOI: https://doi.org/10.33961/jecst.2020.01788 This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.