Tools for assessing damage in concrete affected by AAR coming from fine and coarse aggregates

L F M Sanchez,J Bastien,D Mitchell,B Fournier,M Jolin

doi:10.1590/s1983-41952017000100005

L F M Sanchez, J Bastien + Show 3 more

Open Access

https://doi.org/10.1590/s1983-41952017000100005

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Abstract

Over the last few years, comprehensive management programs for the diagnosis and prognosis of alkali-aggregate reaction (AAR) in aging concrete structures were developed in North America, based on a series of laboratory test procedures. Although promising, these lab-procedures presented several parameters whose impacts were not completely understood, which significantly reduced their applicability for the appraisal of deteriorated concrete structures in service. In this context, it has been suggested that two lab-tools, the Stiffness Damage Test (SDT) and the Damage Rating Index (DRI) could reliably assess the condition of concrete affected by AAR. This paper presents the condition assessment of 25, 35 and 45 MPa AAR affected concrete specimens incorporating fine and coarse reactive aggregates and presenting different distress degrees (i.e. expansion levels from 0.05 to 0.30%) through the use of an innovative multi-level approach. Results show that both SDT and DRI are suitable for assessing damage in AAR affected concrete through their output parameters. Yet, they present a complementary character, which illustrates the need for a multi-level approach.

Highlights

Alkali-silica reaction (ASR), one of the most common deleterious mechanisms identified in concrete structures worldwide, consists in a chemical reaction between “unstable” silica mineral forms within the aggregate materials and the alkali hydroxides (Na, K – OH) dissolved in the concrete pore solution
It has been suggested that two lab-tools, the Stiff ness Damage Test (SDT) and the Damage Rating Index (DRI) could reliably assess the condition of concrete affected by aggregate reaction (AAR)
Results show that both Stiffness Damage Test (SDT) and DRI are suitable for assessing damage in AAR affected concrete through their output parameters

Summary

Introduction

Alkali-silica reaction (ASR), one of the most common deleterious mechanisms identified in concrete structures worldwide, consists in a chemical reaction between “unstable” silica mineral forms (i.e. minerals that are susceptible for presenting dissolution under alkaline environments) within the aggregate materials and the alkali hydroxides (Na, K – OH) dissolved in the concrete pore solution. There is currently no consensus about the most efficient method(s) (surface treatments for moisture control, chemical treatments, strengthening, stress relief (slot cutting), etc.) that should be implemented, and when, for the rehabilitation of concrete structures/structural elements suffering from ASR In this context, one of the biggest challenges in dealing with ASR damaged aging concrete structures is to establish the correlation between ASR distress “signatures” (i.e. ASR distress illustrated in Figure 1) and the loss/reductions in mechanical properties, physical integrity, durability and performance of the affected material, as well as their structural implications. Recent studies dealing with the evaluation of the mechanical performance of aging concrete suggest that both the Stiffness Damage Test (SDT) and the Damage Rating Index (DRI) can provide a diagnostic evaluation of the “damage degree” of concrete affected by ASR [2,3,4]

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