Reliability Of Multi-Method Mineralogical Identification In Expansive Soils

Abstract

The swelling characteristics and engineering performance of expansive soils are primarily governed by their clay mineralogy; however, mineralogical identification based on a single method may be insufficient for natural clays composed of multiple clay minerals together with non-clay constituents. This study aims to determine the mineralogy of a natural expansive clay from the Çubuk district of Ankara, Türkiye, using an integrated set of direct and indirect methods, and to demonstrate the limitations of relying on a single technique while proposing a practical combination of tests for more reliable mineralogical identification. Direct analyses included X-ray diffraction (XRD) and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDX), while indirect indicators comprised methylene blue adsorption, Atterberg limits, clay fraction content (<2 μm) and activity. The results show that the Çubuk clay contains a significant smectitic (montmorillonitic) component together with non-clay minerals such as quartz and calcite. Methylene blue results indicate high cation exchange capacity and specific surface area, and SEM–EDX spectra support the presence of interlayer cations consistent with a smectite-dominant clay fraction exhibiting illite-smectite characteristics. The results highlight the advantage of a multi-method approach and provide a practical framework for more robust mineralogical characterization.

Keywords

• Expansive soil
• Clay mineralogy
• XRD
• SEM-EDX
• Methylene blue test

Supporting Institution

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Ethical Statement

This study does not involve human participants or animals. All experimental procedures were conducted in accordance with standard laboratory practices. No ethical approval was required.

Thanks

The authors would like to thank laboratory staff for their valuable support during the experimental studies.

Şişen Zeminlerde Çoklu Yöntemlere Dayalı Mineralojik Tanımlamanın Etkinliği

Abstract

Şişme potansiyeline sahip zeminlerin şişme davranışı ve mühendislik performansı büyük ölçüde kil mineralojisi tarafından kontrol edilmektedir; ancak birden fazla kil minerali ile birlikte kil dışı bileşenler içeren doğal zeminlerde tek bir yöntemle yapılan mineralojik tanımlama çoğu zaman yetersiz kalmaktadır. Bu çalışmada, Ankara ili Çubuk yöresine ait doğal bir şişen kilin mineralojisi, doğrudan ve dolaylı yöntemlerin birlikte kullanıldığı bütüncül bir yaklaşımla belirlenmiş; ayrıca tek bir yönteme dayalı analizlerin sınırlılıkları ortaya konularak daha güvenilir mineralojik tanımlama için pratik bir deney kombinasyonu önerilmiştir. Doğrudan analizler kapsamında X-ışını kırınımı (XRD) ve enerji dağılımlı X-ışını spektroskopisi ile desteklenmiş taramalı elektron mikroskobu (SEM–EDX) kullanılmış, dolaylı göstergeler olarak ise metilen mavisi adsorpsiyon deneyi, Atterberg limitleri, kil fraksiyonu (<2 μm) oranı ve aktivite değerleri değerlendirilmiştir. Elde edilen sonuçlar, Çubuk kilinin önemli miktarda smektit (özellikle montmorillonit) içerdiğini ve bunun yanında kuvars ve kalsit gibi kil dışı mineralleri de barındırdığını göstermektedir; metilen mavisi deney sonuçları yüksek katyon değişim kapasitesi ve özgül yüzey alanına işaret ederken, SEM–EDX analizleri smektit ağırlıklı ve illit–smektit karakteri gösteren kil fraksiyonunda tabakalar arası katyonların varlığını desteklemektedir. Bu bulgular, çoklu yöntem kullanımının sağladığı üstünlüğü açıkça ortaya koymakta ve daha sağlam bir mineralojik karakterizasyon için uygulanabilir bir yaklaşım sunmaktadır.

Keywords

• Şişen zeminler
• Kil mineralojisi
• XRD
• SEM–EDX
• Metilen mavisi deneyi

Supporting Institution

Bu çalışma, kamu, ticari veya kâr amacı gütmeyen herhangi bir kuruluştan özel bir destek almamıştır.

Ethical Statement

Bu çalışma insan katılımcılar veya hayvanlar üzerinde gerçekleştirilmemiştir. Tüm deneysel çalışmalar standart laboratuvar uygulamalarına uygun olarak yürütülmüştür. Etik kurul izni gerekmemektedir.

Thanks

Yazarlar, deneysel çalışmalar sürecinde katkı sağlayan laboratuvar personellerine teşekkür eder.

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