Abstract—Utilizing waste materials in civil engineering applications has a positive influence on the environment by reducing carbon dioxide emissions and issues associated with waste disposal. Granulated blast furnace slag (GBFS) is a by-product of the iron and steel industry, with millions of tons of slag being annually produced worldwide. Slag has been widely used in structural engineering and for stabilizing clay soils; however, studies on the effect of slag on sandy soils are scarce. This article investigates the effect of slag content on shear strength parameters through direct shear tests and unconsolidated undrained triaxial tests on mixtures of Perth sand and slag. For this purpose, sand-slag mixtures, with slag contents of 2%, 4%, and 6% by weight of samples, were tested with direct shear tests under three normal stress values, namely 100 kPa, 150 kPa, and 200 kPa. Unconsolidated undrained triaxial tests were performed under a single confining pressure of 100 kPa and relative density of 80%. The internal friction angles and shear stresses of the mixtures were determined via the direct shear tests, demonstrating that shear stresses increased with increasing normal stress and the internal friction angles and cohesion increased with increasing slag. There were no significant differences in shear stresses parameters when slag content rose from 4% to 6%. The unconsolidated undrained triaxial tests demonstrated that shear strength increased with increasing slag content. Keywords—Direct shear, shear strength, slag, UU test. I. INTRODUCTION HEAR strength is one of the most important soil characteristics required for analysing and designing geotechnical applications, such as foundations, slopes, embankments and retaining walls [1]. Shear strength refers to the maximum stress that a soil can withstand before reaching failure conditions [2]. In granular soils, shear strength is a combined effect of friction and interlocking forces between soil grains. Conversely, in fine soils, the shear strength is produced from soil particles cementing together, or in other words, their cohesion. Shear strength characteristics, for instance the internal friction angle and cohesion, have been extensively investigated by the implementation of both in situ and laboratory tests, such as the direct shear box, ring shear, cone penetrometer and triaxial apparatus. Variations in strength and density, low bearing capacity and high permeability are negative properties of sandy soils which can cause problems for construction [3]. Numerous studies have researched methods to reduce the negative properties of sandy Ayad Salih Sabbar is Ph.D. candidate at the Department of Civil Engineering, Curtin University, Perth, Australia (phone: +61424673252; e- mail: Ayadsalih.sabbar@ postgrad.curtin.edu.au). Amin Chegenizadeh, Researcher, and Hamid Nikraz, Professor, are with the Department of Civil Engineering, Curtin University, Perth, Australia (e- mail: Amin.Chegenizadeh@ curtin.edu.au, H.Nikraz@curtin.edu.au). soil by mixing it with additives such as cement, lime, clay, and fly ash. There has been recent interest globally in the use of slag in different civil engineering applications, due to the environmental and economic advantages. Using Slag has a positive influence on the environment, as it reduces carbon dioxide emissions and other issues associated with waste disposal; most countries in the world, including Australia, are manufacturing millions of tons of slag annually [4], [5]. The production of one ton of Portland cement generates 0.95 tons of CO 2 ; however, production of the same amount of slag produces 0.07 tons of CO 2 [6]. Additionally, using slag in construction engineering may reduce the cost of building and conserve resources. Slag is a by-product of the iron and steel industries which can be classified into different types based on the production method used. Blast furnace slag is a by-product of iron made in a blast furnace, which can be divided into three categories (those being air-cooled, granulated, and expanded slag). Slag has been widely utilized in structural engineering, but has more recent application in geotechnical engineering [6], [7]. According to the Australian Slag Association [8], 80% of the 3.4 million tons of slag which was produced in Australia in 2009 was used in the construction of buildings and roads. In geotechnical engineering, slag has been utilized widely for improving the properties of clay soils, but published research on the use of slag (without other additives) for improving sandy soils is limited. Slag reacts to water contact in the same way as Portland cement; however, it takes a long time to complete its chemical reaction, which is why it is sometimes blended with a chemical activator [9]. According to [10], the geotechnical characteristics of GBFS, such as a high internal friction angle, light weight, and high permeability, make it useful for the backfilling of quay-wells, sand mats, and lightweight embankments. Many researchers have found that the shear strength of slag-stabilized sand was increased by using a chemical activator with the slag [6], [11], [12]. The present study was recently started by the authors in collaboration with an investigation into the effects of slag content on the shear strength characteristics of sandy soils. The aim was to examine the possibility of improving the shear strength of sandy soils by using waste materials, such as slag. It is apparent from the literature review that numerous investigations have been conducted on the effects of slag contents on clay soils, while research into the effect of slag on the shear strength of sandy soils is limited. Therefore, this study aimed to explore the properties of clean sand compared to sand mixed with various slag contents (2%, 4%, and 6%, by weight), using direct shear tests and unconsolidated undrained triaxial tests. Additionally, this work is a part of ongoing Experimental Investigation on the Shear Strength Parameters of Sand-Slag Mixtures Ayad Salih Sabbar, Amin Chegenizadeh, Hamid Nikraz S World Academy of Science, Engineering and Technology International Journal of Geotechnical and Geological Engineering Vol:11, No:3, 2017 222 International Scholarly and Scientific Research & Innovation 11(3) 2017 ISNI:0000000091950263 Open Science Index, Geotechnical and Geological Engineering Vol:11, No:3, 2017 publications.waset.org/10006467/pdf