Effect of ultrasonic treatment on clay microfabric evaluation by atomic force microscopy Ali Asghar Firoozi a,⇑ , Mohd Raihan Taha a,b , Ali Akbar Firoozi a , Tanveer Ahmed Khan a a Department of Civil & Structural Engineering, Universiti Kebangsan Malaysia, 43600 UKM Bangi, Selangor, Malaysia b Institute for Environment and Development (LESTARI), Universiti Kebangsan Malaysia, 43600 UKM Bangi, Selangor, Malaysia article info Article history: Received 25 September 2014 Received in revised form 5 February 2015 Accepted 9 February 2015 Available online 18 February 2015 Keywords: Atomic force microscopy Microfabric Ultrasonic Clay Orientation abstract Researchers previously thought the only ways to investigate the microfabric of clayey soil were through a scanning electron microscope (SEM), a transmission electron microscope (TEM), an X-ray, and an optical microscope. However, in this research, ultrasonic equip- ment was used to disperse clayey soils (bentonite, illite, and kaolinite) for different lengths of time. After dispersion, an atomic force microscope (AFM) was employed to take three- dimensional (3D) photographs. While the samples were intact, AFM was able to take 3D photographs in different environments. The IA_P9_BUILD software was employed to ana- lyze the data to obtain the angle of particle orientation and the particle size distribution. In this investigation, it was observed that with the use of an ultrasonic device with 30 KHz of power, bentonite, illite, and kaolinite reached a dispersion state after 12, 8, and 6 min, respectively. Ó 2015 Published by Elsevier Ltd. 1. Introduction The angle of particle orientation has a significant effect on the mechanical properties of clayey soils [1]. The angle of particle orientation can be identified by studying the microfabric of clayey soil [2,3]. Soil response is known to be sensitive to material fabric, that is, the topology of the internal structure of the soil. Soil fabric is the geometric arrangement of particles within the soil mass [4]. In geomechanics research, fabric has been qualitatively described, and fabric changes have frequently been inferred from macroscale observations of soil responses: for example, the anisotropy of small-strain stiffness [5], the anisotropy of permeability [6], or a comparison of the mechanical responses of specimens prepared using differ- ent approaches [7]. On a small scale, the soil microfabric can be studied by looking at undisturbed samples under a scanning electron microscope (SEM) or it can be described under a high- resolution optical microscope in a thin section [8–13]. Soil fabric can be quantified using either scalar parameters or directional parameters. Examples of scalar measures of fabric include the coordination number, the void ratio dis- tribution within the sample, and the contact index. Direc- tional fabric can be measured using particle long-axis orientations or contact normal orientations, and the statis- tical approaches to analyze datasets of orientation vectors are relatively well-established [14–16]. Different kinds of soil fabrics indicate different sedimentary environments in which the soils were formed [17–19]. In addition, they could show the information of the different properties and distinct material compositions of soils. In general, the engineering properties of soil are connected closely to its structure and fabric [10]. In addition, they depend on the distance and angle between the clay particles [20,21]. The distance between two clay particles defines the porosity of the soil mass [4], whereas the angle http://dx.doi.org/10.1016/j.measurement.2015.02.033 0263-2241/Ó 2015 Published by Elsevier Ltd. ⇑ Corresponding author. E-mail addresses: mehran.firoozi2@gmail.com (A.A. Firoozi), profraihan@gmail.com (M.R. Taha), a.firoozi@gmail.com (A.A. Firoozi), takhan557@gmail.com (T.A. Khan). Measurement 66 (2015) 244–252 Contents lists available at ScienceDirect Measurement journal homepage: www.elsevier.com/locate/measurement