Alternative patch repair materials for rebar corrosion damage

Primesh Jassa,Hans Beushausen,Ines Tchetgnia Ngassam,M.G Alexander,F Dehn,H Beushausen,P Moyo

doi:10.1051/matecconf/201819907017

Abstract

One of the most common methods adopted in the rehabilitation of corrosion-damaged concrete is the patch repair procedure. However, in practice this method has shown to often be unreliable as a consequence of the widespread occurrence of shrinkage induced cracking and poor substrate-patch adhesion leading to debonding of the patch repair. From a practical point of view, such failed repair systems essentially restore the repaired concrete back to a deteriorated state. There is a common belief that repairing concrete with specialised proprietary repair materials would guarantee durability. However, the widespread premature failure of patch repairs conducted using such materials has proven the contrary. This paper presents an understanding of the materials and issues concerning the durability and serviceability of concrete patch repairs, with the aim of identifying alternative non-structural patch repair materials for the effective repair of corrosion-damaged concrete structures. The potential patch repair materials researched were polymer-cement concrete (copolymer of vinyl acetate and ethylene with 5% cement replacement) and 60%, 80% and 100% fly ash (FA) mortar. Patch repairs were conducted on substrate moulds to test application and observe cracking/debonding occurrence. Furthermore, compressive strength, durability index, accelerated drying shrinkage, restrained shrinkage, workability and scanning electron microscopy (SEM) tests were conducted to determine the properties of the materials developed with reference to performance requirements of durable concrete repairs. It was concluded that the 60% FA and polymer-cement concrete repair materials had the best overall performance. This research established that innovative alternative repair materials such as a 60% FA or polymer-cement concrete material, can be developed for non-structural patch repairs with improved long-term performance relative to conventional materials.

Highlights

Steel corrosion is of major concern in civil engineering due to its widespread occurrence and associated effects of concrete cracking, delamination and spalling
This study developed four new repair materials namely: 100% fly ash (FA), 80% FA, 60% FA and a polymer repair materials
The 60% FA repair material had the best overall performance with an increase in FA content from 60% to 100%, it was identified that there was a significant drop in overall performance with respect to durability and strength

Summary

Introduction

Steel corrosion is of major concern in civil engineering due to its widespread occurrence and associated effects of concrete cracking, delamination and spalling. A comprehensive investigation on 230 concrete structures in Europe called the ConRepNet Report concluded that up to 50% of all concrete repairs had failed prematurely [1]. The report concluded that 75% of all repairs failed within the first 10 years of service, refer to Fig. 1. This failure rate occurs despite the fact that numerous improvements in materials and methods have been developed. The continuation of corrosion in the adjacent substrate concrete, shrinkage induced cracking and debonding of the patch repair is widespread. These mechanisms fundamentally return the concrete integrity back to a deteriorated state

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