Steel Corrosion Behavior of Reinforced Calcium Aluminate Cement-Mineral Additions Modified Mortar.

Zhongping Wang,Zheyu Zhu,Xiang Peng,Linglin Xu,Kai Wu,Yuting Chen

doi:10.3390/ma14144053

Abstract

Mineral additions can eliminate the conversion in calcium aluminate hydrates and thus inhibit the future strength retraction of calcium aluminate cement (CAC). However, the impacts of these additions on the protection capacity of CAC concrete in relation to the corrosion of embedded steel reinforcement remains unclear. This paper focused on the corrosion behavior of steel reinforcement in slag, limestone powder, or calcium nitrate-modified CAC mortars via XRD and electrochemical methods (corrosion potential, electrochemical impedance, and linear polarization evaluation). The results indicate that strätlingite (C2ASH8), which is formed in slag-modified CAC, has poor chloride-binding ability, leading to decline in corrosion resistance of the steel reinforcement. The electrochemical parameters of specimens immersed in NaCl solution suddenly drop at 14 days, which is 28 days earlier than that of the references. In contrast, the Ca2[Al(OH)6]20.5CO3OH·H2O (CaAl·CO32−-LDH) and 3CaO·Al2O3·Ca(NO3)2·12H2O (NO3-AFm) in limestone powder and calcium nitrate-modified CAC mortar show great chloride-binding ability, thereby improving the corrosion resistance of the steel reinforcement. The electrochemical parameters of specimens modified with calcium nitrate maintain a slow decreasing trend within 90 days.

Highlights

Chloride corrosion is the main cause for this, as it destroys the passive film on the surface of the steel reinforcement
Studies have shown that reducing free chloride content is the most effective way to protect steel reinforcements in concrete; chloride-binding ability is of great significance [5,6,7]
This paper aims to clarify the chloride corrosion of steel reinforcements in calcium aluminate cement (CAC) modified by mineral additions

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The foundation often comprises of reinforced concrete structures. Damages caused by seawater corrosion have led to huge economic losses and waste of resources [1]. Chloride corrosion is the main cause for this, as it destroys the passive film on the surface of the steel reinforcement. The large volumes of rust lead to crack in the concrete under expansion stress, accelerating chloride corrosion rates [2,3,4]. Studies have shown that reducing free chloride content is the most effective way to protect steel reinforcements in concrete; chloride-binding ability is of great significance [5,6,7]

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Methods

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Conclusion