Abstract
Abstract According to previous studies, fine materials originated from reactive aggregates can act as a Alkali-Aggregate Reaction mitigator, having its effectiveness dependent on their reactivity, fineness and added content. Thus, the present work aims to study if reactive granitic rock fines can mitigate or reduce the AAR and how the fineness of the material influences its mitigation capacity. For this purpose, granitic rock fines (GRF) from 2 different deposits and Pyrex glass fines (PGF) were tested as concrete addition. Each one of these fines were used in two different finesses and added to the concrete in the contents of 20% by mass of cement. It was observed that the addition of GRF did not affect the physical-mechanical properties of concrete and allowed the reduction in the AAR, being more accentuated with the increase of its specific surface.
Highlights
According to the Brazilian Mining Institute [1], in 2017, Brazil produced about 420 million tons of aggregates for civil construction
As an alternative to add value to this material, studies about its incorporation on concrete and mortars have been made. Such alternative should be performed with caution, because some aggregates can cause a deleterious reaction to the concrete, known as the alkali-aggregate reaction [2]
The chemical compositions of the fines were determined by X-ray fluorescence spectrometry (XRF), using the Bruker S2 Ranger equipment and the pozzolanic activity was determined by chemical titration test, according to the European standard EN 196-5 [14], replacing 25% of the cement with fine
Summary
Priskulnik [3] indicates several factors that can contribute to the reduction and/or mitigation of the AAR, among them: decrease of concrete permeability due to the low water/cement ratio, dosage of an adequate cement consumption and use of active mineral additions, such as silica fume and blast furnace slag, because they fix cement alkalis in the initial phase of cement hydration and decrease the pH of the interstitial concrete solution Some materials, such as ground glass, when incorporated into the cement matrix may be favorable to the occurrence of the AAR or act as a mitigator, depending on the particle size of the material. The reactive silica, when finely ground, contributes to the gel forming in a distributed manner in the cement paste When it is present in the aggregates, it causes the accumulation of the alkali-silica gel in specific places, making them potential expansion points [10]. It was studied if this accelerated reaction harms the physical-mechanical properties of the mortars tested
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