American Journal of Civil Engineering 2015; 3(2): 26-30 Published online February 28, 2015 (http://www.sciencepublishinggroup.com/j/ajce) doi: 10.11648/j.ajce.20150302.11 ISSN: 2330-8729 (Print); ISSN: 2330-8737 (Online) Application of Jute Fiber for the Improvement of Subgrade Characteristics Md. Akhtar Hossain * , Md. Shakhawat Hossain, Md. Kamrul Hasan Department of Civil Engineering, Rajshahi University of Engineering & Technology, Rajshahi, Bangladesh Email address: akhtar412002@yahoo.com (Md. A. Hossain), shakhawat09ruet@gmail.com (Md. S. Hossain), hasankamrul.ce@gmail.com (Md. K. Hasan) To cite this article: Md. Akhtar Hossain, Md. Shakhawat Hossain, Md. Kamrul Hasan. Application of Jute Fiber for the Improvement of Subgrade Characteristics. American Journal of Civil Engineering. Vol. 3, No. 2, 2015, pp. 26-30. doi: 10.11648/j.ajce.20150302.11 Abstract: Improvement in subgrade has always been an area of concern to highway and geotechnical engineers. In case of a highway, a weak subgrade results in greater thickness of pavement layer which increases the cost of pavement construction. To strengthen the subgrade soil, the use of jute fiber is advantageous because they are cheap, locally available, biodegradable, and eco-friendly. Jute fiber mixed randomly with subgrade soil has significant impact on the improvement of subgrade characteristics over the last decade. Keeping this in view an experimental study was conducted on locally available soil reinforced with jute fiber. In this study the soil samples were prepared at its maximum dry density corresponding to optimum moisture content in the CBR mold with and without reinforcement. The percentage of jute fiber by dry weight of soil was taken as 0.3%, 0.6%, 0.9%, and 1.2%. In the present investigation the length of fiber was taken as 15 mm and 30 mm, and two different diameters (4 mm and 8 mm) were considered for each fiber length. From the laboratory tests the effect of jute fiber content on density of soil (optimum moisture content and maximum dry density) was observed for each length and diameter of jute fiber. It was observed that the optimum moisture content increases and the maximum dry density decreases with the increase in jute fiber content for each length and diameter of jute fiber. The laboratory CBR values of soil and soil reinforced with fiber were determined. The effects of aspect ratio (length/diameter ratio) of jute fiber on CBR value of soil were also investigated. Test results indicate that CBR value of soil increases with the increase in length of jute fiber. It was also observed that increasing the diameter of jute fiber further increases the CBR value of reinforced soil, and this increase is substantial at fiber content of 1.2% for aspect ratio of 3.75 (length = 30 mm, diameter = 8 mm). Keywords: Subgrade, Jute Fiber, Length, Diameter, CBR Value 1. Introduction Transportation plays a vital rule in the development of economy, industry, society and culture of any country. To achieve development in those fields, a satisfactory mode of transport and communication is indispensable. This can be achieved through a transportation system, which is economically viable. Economy in road network can be achieved through economical pavement design. Practically it is not possible to have good subgrade always. Poor subgrade necessitates a greater pavement thickness resulting in increased construction cost. With the aim of reducing pavement thickness on poor subgrade new techniques of construction and soil stabilization have been continuously explored. Poor natural soils make them practically unsuitable for many civil engineering construction activities including road pavements. In such cases natural soils are being treated with different kinds of materials to improve their engineering properties. Aggarwal and Sharma (2010) studied the application of jute fiber in the improvement of subgrade characteristics. From this study it was concluded that jute fiber reinforcement reduces the maximum dry density and increases the optimum moisture content of the subgrade soil. The CBR value of the subgrade soil increases up to 250% with the inclusion of bitumen coated jute fiber [1]. Fiber reinforced soil has been used in many countries in the recent past and further research is in progress for many hidden aspects of it. Fiber reinforced soil is effective in all types of soil (i.e. sand, silt, clay). Use of natural material such as jute, coir, sisal and bamboo, as reinforcing materials in soil is prevalent for a long time and they are abundantly used in many countries like India, Philippines, and Bangladesh etc. The main advantage of these materials is they are locally available and are very cheap. They are biodegradable hence do not create disposal problem in environment. Processing of