Does the Methylene Blue Test Give Equally Satisfactory Results in All Studied Igneous Rocks Relative to the Identification of Swelling Clay Minerals?

Panagiota P Giannakopoulou,Eleni Gianni,Basilios Tsikouras,Petros Koutsovitis,Dimitrios Papoulis,Aikaterini Rogkala,Paraskevi Lampropoulou,Petros Petrounias,Konstantin Hatzipanagiotou

doi:10.3390/min10030283

Panagiota P Giannakopoulou, Eleni Gianni + Show 7 more

Open Access

https://doi.org/10.3390/min10030283

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Journal: Minerals	Publication Date: Mar 21, 2020
Citations: 4	License type: CC BY 4.0

Affiliation: University of Patras, Universiti Brunei Darussalam

Abstract

The presence or the absence of swelling clay minerals in rocks, which are used in various construction applications, constitutes a determinant factor for their strength, and consequently, in their general behavior in various construction applications, as they have the ability to swell up to 400 times of their usual volume, causing failures to any application in which they participate. The aim of this study is to respond to the question of whether the empirical method of methylene blue yields equally safe and correct results in different types of igneous rocks and if not, which is the determining factor affecting the results. The answer to this complex question is feasible by investigating the microscopic structure and the mineralogy of the studied rocks, and particularly, using the content of specific phyllosilicate minerals which may be related or not with the methylene blue values. According to the results, the methylene blue test seems to work correctly for the intermediate (Group I) and mafic (Group II) examined rocks, but it seems to be wrong for the highly serpentinized ultramafic rocks (up to 70% of serpentine) (Group III).

Highlights

Clay minerals are amongst the constituents of rocks which are used as aggregates and belong to the silicate class, whereas tetrahedron rings are linked by shared oxygens to other rings in a two-dimensional plane which forms a sheet-like structure [1,2]
The present study focuses on responding to a fundamental question concerning the methylene blue test and if this test shows accurate and satisfactory results in each type of igneous rock used as aggregates
The content and the type of the swelling clay minerals have been investigated by several researchers that deal with the study and the use of aggregate rocks in various construction applications

Summary

Introduction

Clay minerals are amongst the constituents of rocks which are used as aggregates and belong to the silicate class (phyllosilicate minerals), whereas tetrahedron rings are linked by shared oxygens to other rings in a two-dimensional plane which forms a sheet-like structure [1,2]. These tetrahedral sheets are held together by weakly-bonded cations and usually contain entrapped water molecules between the sheets [3,4]. The 2:1 clay consists of Minerals 2020, 10, 283; doi:10.3390/min10030283 www.mdpi.com/journal/minerals

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