CHEMICAL TREATMENT WITH OXALIC ACID TO IMPROVE THE DURABILITY OF CEMENT-BASED MATERIALS IN ACID ENVIRONMENTS
Author(s): Voegel, C., Bertron, A., Erable, B. and Escadeillas, G.
Paper category: Conference
Book title: XIII International Conference on Durability of Building Materials and Components - XIII DBMC
Editor(s): Marco Quattrone, Vanderley M. John
Print ISBN: none
Publication year: 2015
Total Pages: 9
Abstract: This aim of the work reported here was to improve the durability of cement-based materials exposed to acidic environments, using superficial chemical treatments of the hardened cement matrix.
Our previous studies, focusing on the action of organic acids on the cement matrix, highlighted the protective effect of calcium oxalate salt formed during attack of the cement matrix by oxalic acid. It was shown that calcium oxalate was stable even at very low pH and seemed to act as a sealant for the cement matrix porosity. On the basis of these results, the chemical treatments implemented in the present paper consisted of impregnating cement matrices with solutions made of oxalic acid or mixes of oxalic and acetic acids.
These treatments were carried out on CEM I cement paste specimens made with two water/cement ratios (0.4 and 0.27) in order to investigate the influence of the initial porosity of the matrix. After the treatments, the cement paste specimens were immersed in aggressive solutions of acetic acid with a pH of 4. The efficiency of the treatments was assessed by measuring mass losses and degraded depths. The chemical, physical and mineralogical changes in the cement pastes were investigated using XRD, EPMA and water porosimetry.
In this work, the protective effect of oxalic acid, previously demonstrated for CEM I W/C=0.27, was confirmed for CEM I with W/C=0.40. The mix of acetic and oxalic acids in the treatment solution improved the protective effect of the treatment against further acid attack but the protection was not total.
Online publication: 2015
Publication Type: full_text
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