ORIGINAL PAPER Shear Strength Parameters of Improved Peat by Chemical Stabilizer Hossein Moayedi • Sina Kazemian • Bujang B. K. Huat Received: 15 June 2012 / Accepted: 11 March 2013 Ó Springer Science+Business Media Dordrecht 2013 Abstract The present research aimed to discuss the applicability of cationic grouts in geotechnical engi- neering. The effects of several cationic stabilizers such as monovalent (sodium silicate), divalent (calcium oxide and calcium chloride), and trivalent (aluminum hydroxide) were investigated on shear strength improvement of tropical peat samples. The unconfined compressive strength (UCS) tests were performed after the time frame of 7, 21, and 30 days as curing time, respectively. Apart from the physicochemical characteristics of the stabilized peat, scanning electron microscopy and energy-dispersive X-ray spectroscopy tests were also carried out to study the ongoing microstructural changes. It is to be noted that the shear strength values for peat samples rose to 8, 6, 6, and 4% of sodium silicate, calcium oxide, calcium chloride, and aluminum hydroxide, respectively. The highest observed UCS outcome is the one taken from the calcium oxide where the UCS of treated peat after 30-day curing time increased to 76 kPa. The strength changes resulted from the various cationic stabilizers can best be explained via the consideration within the mineralogical composition as well as those physico- chemical changes happening in the peat. Keywords Tropical peat  Soil improvement  Chemical grouts  Microstructure analysis 1 Introduction As stated by the American Standard of Testing and Material (ASTM), peat is a soil having more than 75 % organic content. It is generally formed under anaerobic conditions through the action of fungi, bacteria, and chemical compounds upon the plant remains. Peat naturally contains a very high water content in comparison with mineral soils. However, in most countries around the globe, this material covers a substantial area which is called tropical land. In Malaysia, about 8 % of the country’s land area is covered with this type of soil (Edil 2001; Huat 2004). The extremely low shear strength of peat has propelled this soil material family to a prominent place within various research scopes in the realm of soil improve- ment (Edil and Wang 2000; Hebib and Farrell 2003; Kalantari et al. 2010; Kazemian et al. 2012). Chemical stabilization applies to a variety of soils. They are often applied as a cost-effective material to improve the performance of soft ground. Chemically H. Moayedi (&) Faculty of Engineering, Kermanshah University of Technology, Kermanshah, Iran e-mail: hossein.moayedi@gmail.com S. Kazemian Department of Civil Engineering, Bojnourd Branch, Islamic Azad University, Bojnourd, Iran B. B. K. Huat Department of Civil Engineering, Universiti Putra Malaysia, Serdang, Selangor, Malaysia 123 Geotech Geol Eng DOI 10.1007/s10706-013-9635-5