Mechanism of concrete deterioration due to salt crystallization

doi:10.1016/j.matchar.2004.08.013

Materials Characterization

Volume 53, Issues 2–4, November 2004, Pages 123-127

https://doi.org/10.1016/j.matchar.2004.08.013 Get rights and content

Abstract

Surface scaling of concrete is observed due to salt crystallization. The salts present on concrete as efflorescence or subflorescence are usually highly soluble in water. The most common efflorescent material is anhydrous sodium sulfate (Na₂SO₄, thenardite) and hydrous sodium sulfate (Na₂SO₄·10H₂O, mirabilite). Various mechanisms have been proposed concerning the cause of this form of deterioration: (a) the solid volume change from the thenardite to mirabilite; (b) salt hydration pressure; and (c) the salt crystallization pressure. All three mechanisms are reviewed and discussed in the present paper.

Introduction

Surface scaling of concrete due to salt crystallization is a recognized form of deterioration [1], [2], [3]. However, there is no consensus on the mechanism of this form of concrete deterioration. The mechanisms proposed by various researchers can broadly be classified in three groups:

(a)
solid volume change during transformation of anhydrous salt to its hydrous form [4];
(b)
salt hydration pressure; and
(c)
salt crystallization pressure [6], [7], [8], [9], [10], [11], [12].

The purpose of the present paper is to review and discuss these mechanisms.

Section snippets

Solid volume change hypothesis

Solid volume change is the most popular hypothesis advanced by many researchers and accepted by many people as the most possible mechanism. The main deficiency of this hypothesis is that it does not account for the volume of water in the net calculation. Considering only the solid volumes, the hydrous form of a salt has higher volume than its anhydrous form. However, if the volume of water is included in the net calculation, the formation of hydrous salt reduces the total volume. Take the

Conclusions

It is well established that concrete can deteriorate due to salt crystallization. Three different mechanisms have been proposed in the literature. These mechanisms have been evaluated and two of them rejected. Solid-state salt hydration does not occur because it is a through-solution process. Volume change from the anhydrous form to the hydrous form is unimportant because, taking into account the water added, the total volume of the system decreases. Crystallization pressure created by salts

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¹: Present address: Degussa Admixture, Inc. 23700 Chagrin Boulevard Cleveland, OH 44122-5554, USA

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Mechanism of concrete deterioration due to salt crystallization

Abstract

Introduction

Section snippets

Solid volume change hypothesis

Conclusions

Cem. Concr. Res.

Cem. Concr. Res.

Cem. Concr. Res.

Cem. Concr. Res.

Efflorescence and breakdown of building materials

Nord. Concr. Res.

Salt hydration distress observations-an unidentified or misidentified cause of concrete distress

Concr. Int.