A micro fabric study of untreated and treated expansive soils using atomic force microscopy

Hariprasad, C and Thejesh kumar, G and Umashankar, B (2014) A micro fabric study of untreated and treated expansive soils using atomic force microscopy. In: Indian Geotechnical Conference IGC-2014, 18-20 December 2014, Kakinada, India.

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Abstract

Chemical stabilization is one of the common soil improvement methods to stabilize expansive soils. The changes in fabric of treated soil can provide insight into the extent of chemical stabilization. In this study, a brief review of state-of-art on the usefulness of microscopic studies is presented. In addition, application of Atomic Force Microscopy (AFM) technique to study the micro fabric of soils are presented, and a case study is considered to illustrate the robustness of the method. Black cotton and shale soils used and the fabric of untreated and treated soils is obtained using AFM technique. The results indicate that Atomic Force Microscopy is a powerful technique for imaging soils and other mineral surfaces in the sub micrometer and sub nanometer range. INTRODUCTION Grain-size distribution of soil is an important characteristic affecting its behavior. Particle sizes in the range of 2µm to 2mm are determined by sieving and hydrometer method. However for soil particles with size less than 2µm (particles that cannot be seen with the naked eye), microscopic methods are useful to classify soil. Particles with size fraction less than 2µm have significant effect on the engineering properties of soils. There are a few techniques available to study the features of particles in the sub-micron range. They include Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM). TEM and SEM facilitate direct imaging of particles providing size, shape, and morphological information. However, TEM and SEM methods are sometimes unable to differentiate between agglomerates, particles, and grains. Sample preparation procedure for SEM/TEM techniques is time consuming and tedious. A new family of microscopy techniques is Scanning Probe Microscopy (SPM) used to image and measure the parameters of material. The Scanning Probe Microscopy includes Atomic Force Microscopy (AFM), Magnetic Force Microscopy (MFM), Electrostatic Force Microscopy (EFM), Lateral Force Microscopy (LFM), and Electrochemical Atomic Force Microscopy (ECAFM). In the present study, Atomic Force

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