Techno Press
Techno Press

Geomechanics and Engineering
  Volume 20, Number 3, February10 2020 , pages 233-241
DOI: https://doi.org/10.12989/gae.2020.20.3.233
 

Effect of rock mineralogy on mortar expansion
Kadir Karaman and Aknur Bakhytzhan

 
Abstract
    Alkali-silica reaction (ASR) is among one of the most important damaging mechanisms in concrete, depending primarily on aggregates which contain reactive minerals. However, expansion in concrete may not directly relate to the reactive minerals. This study aims to investigate the influence of ASR and the expansion of mortar bars depending on aggregate type containing various components such as quartz, clay minerals (montmorillonite and kaolinite) and micas (muscovite and biotite). In this study, the accelerated mortar bar tests (AMBT) were performed in two conditions (mortar bars in the same and sole NaOH solutions). Petrographic thin section studies, X-ray diffraction (XRD) analysis (Rietveld method), scanning electron microscopy (SEM) and chemical analyses were carried out. This study showed that quartzite bars led to increase in expansion values of mortar bars in diabase-1 and andesite when these were in the same NaOH solution. However, three samples (basalt, quartzite and claystone) were found having ASR expansion based on the AMBT when the special molds were used for each sample. SEM study revealed that samples which exhibit highest expansions according to AMBT had a generally rough surface and acicular microstructures in or around the micro-cracks. Basalt and quartzite showed more variable in major oxides than those of other samples based on the chemical analyses, SEM studies and AMBT. This study revealed that the highest expansions were observed to source not only from reactive aggregates but also from alteration products (silicification, chloritization, sericitization and argillisation), phyllosilicates (muscovite, biotite and vermiculite) and clays (montmorillonite and kaolinite).
 
Key Words
    alkali silica reaction; mortar bar expansion and microstructure; rock mineralogy
 
Address
Kadir Karaman and Aknur Bakhytzhan: Department of Mining Engineering, Karadeniz Technical University, 61080 Trabzon, Turkey
 
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