STABILIZATION OF BLACK COTTON SOIL WITH GROUNDNUT SHELL ASH USING BRITISH STANDARD LIGHT COMPACTION ENERGY

STABILIZATION OF BLACK COTTON SOIL WITH GROUNDNUT SHELL ASH USING BRITISH STANDARD LIGHT COMPACTION ENERGY

ABSTRACT

           The study is a potential stabilization of black cotton soils in Gombe state using Groundnut Shell ash. Index properties of the natural soil showed that, the soil belongs to A-7-6 in AASHTO classification system and CH in USCS classification system. This indicate a poor soil  for engineering use. Liquid limit and Plasticity index values of 83.36 % and 89.32 % respectively for the natural soil suggest that the soil is highly pastic. There was gradual decrease in the free swell to a minimum value of 2.91% at 10% GSA as compared to the natural value of 15.25%.  The soaked CBR for the natural soil is 1.67% which increased to 2.17% at 10% GSA. This value fell short of specification requirement of the CBR value to be used as sub-base or base material. For the electrokinetic test, pH test, considerable increase to a peak value of 9.2 while the peak CEC is 70.50mol/kg at 0% GSA. The durability of samples determined in terms of resistance to lost in strength failed to meet the 80% resistance to loss in strength. This concludes that the groundnut shell ash cannot be used as stabilization for black cotton soil as stated by Stephen (2006)  However, there was increase in strength for UCS of 21 days curing period from a value of 134kN/m² as compared to 313kN/m² for the unstabilized soil.

CHAPTER ONE

INTRODUCTION

1.1 PREAMBLE

          Generally, lands with Black Cotton soils are fertile and very good for agriculture, horticulture, sericulture and aquaculture. Good irrigation systems exist, rainfall is high and people are affluent in these areas. Though black cotton soils are very good for agricultural purposes, they are not so good for laying durable roads. Good road network is a basic requirement for the all round development of an area. Unfortunately, poor road network is hampering the full fledged development of the otherwise prosperous areas. (Bhavanna Rao, 2005).

         Application of solid waste (Groundnut Shell Ash) disposal for soil stabilization is a significant which serves various benefits to the environment. The term solid waste includes all those solid and semi solid materials that are discarded by the community. Improper management of solid waste causes adverse effects on ecology which may lead to possible outbreaks of diseases and epidemics. The over dependence on industrially manufactured soil improving additives (cement, lime etc) have kept the cost of construction of stabilized road financially high. This hitherto have continued to deter the underdeveloped and poor nations of the world from providing accessible roads to meet the need of their rural dwellers who constitute large percentage of their population which are mostly rural farmers. Furthermore, the World Bank has been expending substantial amount of money on research aimed at harnessing industrial waste products for further usage. (Oriola and Moses 2010).

           Black cotton soils are expansive clays with potential for shrinking or swelling under changing moisture condition. The soils are formed under conditions of poor drainage from basic rocks or limestones under alternating wet or dry climatic conditions. They usually exhibit high shrink-swell characteristics with surface cracks, opening during the dry seasons which are more than 50mm or more wide and several mm deep. These cracks close during the wet season and an uneven soil surface is produced by irregular swelling and heaving. Such soils are especially troublesome as pavement sub-grades. (Osinubi, 1997)

           Groundnut Shell is an agricultural waste obtained from milling of groundnut. In the world, the total hectare planted to groundnut is over 20 million hectares per year. It is estimated that over 2 million hectares are planted on groundnut in Nigeria. Groundnuts are mostly intercropped. Groundnut contains about 25% Protein and 45 to 50 % oil. The skins are high in Vitamin B. Groundnut can be decorticated by hand-operated decorticating machine. (NAERLS, 2009)

        In this work, an exercise is done to utilize groundnut shell ash (GSA) to improve the engineering performance of Black Cotton soil which may be an economical solution of soil stabilization.

1.2 Justification of the Research

         In Nigeria, and the world at large; the cost of constructing stabilized roads is financially high. This is apparently due to the over dependence on industrially manufactured soil improving additives (cement, lime etc). The high amount of money spent has continued to invalidate poor and underdeveloped nations of the world from making accessible roads available to meet the standard of their rural dwellers that constitute large percentage of their population. On the other hand, the safe disposal of waste products from industries and agriculture has been hitherto a challenging issue demanding urgent solution because of the decline effect of these materials on the environment and the hazardous risk it pose to the health of humanity.

      Thus, it is greatly required to consider the use of agricultural waste (such as Groundnut Shell Ash- GSA ) in improving the engineering properties of the soil, in this case Black Cotton soil (BCS) when used in road construction will considerably reduce the cost of construction and as well as eradicate or reduce the environmental and hazardous risk of such wastes. Hence, this research is justifiable in the use of Groundnut Shell ash to stabilized Black Cotton soil.

1.3 AIM OF RESEARCH

       This research is aimed at evaluating the possibility of utilizing groundnut shell ash (GSA) in the stabilization of black cotton soils.

1.4 OBJECTIVES OF THE RESEARCH

The following objectives are devised for this research work and are summarized below.

• To investigate the pozzolanic   properties of Groundnut Shell Ash.
• To examine the physical and engineering properties of black cotton soil treated with various percentage of Groundnut Shell Ash (0% – 10%) using British Standard Light compactive effort.
• To contrast between the engineering properties of natural black cotton soil and engineering properties of the treated soil.
• To investigate the electrokinetic properties of virgin BCS treated with GSA
• To carry out durability and strength assessment tests on natural and treated BCS

1.5 SCOPE AND LIMITATION OF THE RESEARCH STUDY

         This research is focused on stabilizing black cotton soil treated with various percentage of Groundnut Shell Ash (0%, 2%, 4%, 6%, 8% and 10% by dry weight of soil). All these tests are carried out at their respective Optimum Moisture Content limited to British Standard Light Compactive effort.