Correlation between diffusion coefficient values of chloride ions obtained through column and ion migration tests in cementitious matrices with varying contents of silica fume and mortar

Silas De Andrade Pinto,Daniel Véras Ribeiro,Sandro Lemos Machado

doi:10.1590/s1983-41952022000300007

Silas De Andrade Pinto, Daniel Véras Ribeiro + Show 1 more

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https://doi.org/10.1590/s1983-41952022000300007

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Abstract

Abstract Corrosion is one of the main phenomena that lead to pathological manifestations in reinforced concrete structures under aggressive environments. with the chloride ion being the most responsible for its occurrence. In this way, understanding the transport mechanisms of this ion through the microstructure of the concrete is of fundamental importance to prevent or delay the penetration of these aggressive agents to guarantee a durable structure. In the literature, there are extensive studies concerning the diffusion of chlorides in concrete and the influence of pozzolanic additions in this mechanism. However, only a few correlate the different methods of analysis. This work aims to determine the chloride ion diffusion coefficients in concrete containing various levels of silica fume (5%, 10%, and 15%) or varying the mortar content (54%, 80%, and 100%), and compares the results obtained through column tests and chloride migration tests. It was observed that, although the techniques used were quite distinct, the diffusion values obtained were similar, contributing to the validation of both techniques. Furthermore, the variation in the mortar ratio causes a reduction in the interfacial transition zone of coarse aggregate/mortars and an increase in the content of aluminates, which promotes a similar effect to the use of silica fume.

Highlights

Concrete is a durable material when well dosed and executed, concrete structures can deteriorate because of a series of deleterious mechanisms/reactions, bringing risks to the safety of users, besides the high costs of repairs.The addition of supplementary materials with pozzolanic characteristics has been proving to be a good alternative for improve the concrete properties while reducing cement consumption
This is due to the pozzolanic reaction, a consequence of the presence of amorphous silica in the silica fume used, which promotes the formation of hydrated calcium silicate (C-S-H)
The silica fume has a filler effect caused by particles that do not react with Ca(OH)2 and that contribute to the filling of voids, allowing better packaging of particles [36], [37]

Summary

Introduction

Concrete is a durable material when well dosed and executed, concrete structures can deteriorate because of a series of deleterious mechanisms/reactions, bringing risks to the safety of users, besides the high costs of repairs.The addition of supplementary materials with pozzolanic characteristics has been proving to be a good alternative for improve the concrete properties while reducing cement consumption. Among the techniques extensively studied in the literature for chloride diffusion in concrete, are those used by Ribeiro et al [5], Shackelford [6] and Andrade [7], based on ASTM C 1202 [8], NT BUILD 492 [9], ASTM C 1556 [10], and ASTM C 1543 [11]. These aim to accelerate the natural process of penetration of these ions and allow the determination of diffusion and of other transport parameters such as tortuosity and mechanical dispersion

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