Contents lists available at ScienceDirect Applied Clay Science journal homepage: www.elsevier.com/locate/clay Research paper Clay concrete and effect of clay minerals types on stabilized soft clay soils by epoxy resin Salaheddin Hamidi a,b,⁎ , Seyed Morteza Marandi a,b a Department of Civil Engineering, Shahid Bahonar University of Kerman, Iran b Department of Civil Engineering, Shahid Bahonar University of Kerman, Iran ARTICLE INFO Keywords: Clay concrete Epoxy resin Clay mineral UCS Toughness Elastic modulus Failure strain ABSTRACT Clay soils, especially soft clay soils covered considerable parts of the earth. Cement and lime are used as tra- ditional additives for clay soils stabilization but unable to increase the strength properties of clay soils sig- nificantly. So, it seems necessary to use new additives to increase the strength parameters of soft clay soils. Therefore, cement and epoxy resin are used for stabilization of soft clay soils in this study. The main objects of this study are the determination of the effect of epoxy resin on the mechanical parameters and microstructure properties of clay soils, the phenomenon of clay concrete and effect of clay minerals on its properties and also, using knowledge of the elastic modulus, toughness and elastic and plastic strain of the stabilized soft clay as a practical criterion for determination of the optimum additive percentage in soft clays stabilization in addition to UCS. In this study, two samples of clay soils with different clay minerals were investigated. Clay soil samples that tested experimentally were bentonite and kaolinite. A series of microstructure and macrostructure experiments were conducted on the samples. The results show that using epoxy resin increases strength parameters about 100 to 1000 times while UCS reaches to more than 50 MPa in some samples based on the clay mineral types in the soils. Unlike the cement concrete, as the strength increases the failure strain and material toughness will increase simultaneously as well. In addition, the important and prominent result of stabilization by epoxy resin is the best efficiency in the weakest and the most sensitive soils. 1. Introduction Soft clay soil is one of the problematic soils covering considerable parts of the earth including many low-land and coastal regions where many urban and industrial hubs are located and are frequently en- countered in civil engineering projects. (Williams et al., 1985; Schwartz, 1985; Sasanian, 2011). Some of the major behavioral and strength problems associated with these types of soils are low strength, excessive settlements, high plasticity, swelling, dispersivity, erodibility, high compressibility and sensitivity to environmental conditions (Huat, 1994; Ouhadi et al., 2014; Ahmed, 2015). Generally, problematic soils such as soft clay soils were improved in order to improve their beha- vioral and strength properties (Vichan and Rachan, 2013; Yi et al., 2015, 2016; Sukpunya and Jotisankasa, 2016). One of the methods to improve soft clay soils is deep mixing method (DMM) in which binders such as cement, lime, fly ash, gypsum and other additives are mixed with the soil in order to form stone columns of a hardened material improving the classification properties and strength parameters such as bearing capacity (Porbaha, 1998, 2002; Sukontasukkul and Jamsawang, 2012; Voottipruex and Jamsawang, 2011a, 2011b, 2014; Anagnostopoulos, 2015). The DMM method is often applied in many geotechnical and foundation applications, such as the stabilization of deep excavations or high embankments, slope stability, tunnel support, reduction of settlement or increase of bearing capacity of soft com- pressible soils for building foundations, and water retention (Anagnostopoulos, 2015). Despite the positive points mentioned about the DMM, laboratory and in situ research works have shown that the traditional additives used in this method are incapable of increasing the strength and ductility properties of stabilized soft clay soils significantly (Kamruzzaman et al., 2000; Horpibiulsuk et al., 2002; Petchgate et al., 2003, 2004; Ahnberg et al., 2003; Puppala et al., 2003; Tabbaa, 2003; Wu et al., 2005; Impe and Flores, 2006; Lorenzo et al., 2006;Horpibulsk et al., 2011; Pakbaz and Alipour, 2012; Khemissa and Mahamedi, 2014; Anagnostopoulos, 2015). The terms that should be noted about clay stabilization with cement are influence of high water or organic matter content of a soil, the pH value, clay mineral types in clay soil samples and sensitivity of clay soils on the various factors on the strength of the soil–cement mixture renders the application of the deep cement mixing http://dx.doi.org/10.1016/j.clay.2017.10.010 Received 3 April 2017; Received in revised form 9 October 2017; Accepted 11 October 2017 ⁎ Corresponding author at: Shahid Bahonar University of Kerman, Faculty of Eng., Civil Eng. Department, Kerman, Iran. E-mail address: s.hamidi@eng.uk.ac.ir (S. Hamidi). Applied Clay Science 151 (2018) 92–101 Available online 05 November 2017 0169-1317/ © 2017 Elsevier B.V. All rights reserved. MARK