Study on High-Volume Unprocessed Fly Ash Concrete with Colloidal Nanosilica under Chloride Exposure

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Title: Study on High-Volume Unprocessed Fly Ash Concrete with Colloidal Nanosilica under Chloride Exposure

Author(s): Lincy Varghese, V. V. L. Kanta Rao, and Lakshmy Parameswaran

Publication: Materials Journal

Volume: 116

Issue: 4

Appears on pages(s): 61-68

Keywords: chloride exposure; corrosion; diffusion; durability; electrical resistivity; high-volume fly ash concrete; migration; unprocessed fly ash

Date: 7/1/2019

Abstract:
The paper presents an experimental investigation on durability performance of colloidal nanosilica-added high-volume fly ash concrete (HVFAC) mixtures made with coarser unprocessed siliceous fly ash (with its proportion varying from 50 to 70% in the cementitious matrix) under chloride exposure. Chloride-induced corrosion is a serious durability concern for reinforced and prestressed concrete structures, and corrosion of reinforcement severely lowers the service life of structures. Therefore, an attempt has been made in this study to investigate, through rapid chloride permeability and chloride penetration tests, the performance of HVFAC mixtures under chloride ingress by migration and diffusion mechanisms. The permeability test results have been further corroborated with electrical resistivity of these concretes. The corrosion behavior of reinforcing bar embedded in test specimens made with these concretes was also investigated. The study indicated that the addition of small quantities of colloidal nanosilica significantly improved the resistance to chloride ingress and increased resistance to the corrosion of reinforcing bar in HVFAC.