Optimization and Modelling of Rice Husk Ash-clay Soil Stabilization

Optimization and Modelling of Rice Husk Ash-clay Soil Stabilization

CHAPTER ONE

OBJECTIVES

This study will hopefully be relevant in the following respects:

The design and construction of pavements and foundations on expansive soils
To the material engineering students and practicing engineers.
To the governmental agencies that are entrusted with the responsibility of ensuring quality control.
To civil engineering consultants; contractors and their clients.
It is also perceived that it would generate further research in the following areas

CHAPTER TWO

LITERATURE REVIEW

GENERAL INTRODUCTION

In addition to the conventionally used materials there are various alternative technologies and materials developed by various research organizations, innovators and manufacturers globally that are beneficial in the civil engineering construction. As part of this study, these alternatives were researched and the information collected has been provided in what follows.

In the review of literature by Department for International Development DFID (2003) titled: “Stabilized Sub-Bases For Heavily Trafficked Roads,” Stabilization is said to mean the process of mixing a stabilizer, for example cement, with a soil or imported aggregate to produce a material whose strength is greater than that of the original unbound material. The use of stabilization to improve the properties of a material is becoming more widespread due to the increased strength and load spreading ability that these materials can offer. Stabilization technology is extremely relevant for heavily trafficked pavements where its’ benefits are beginning to be appreciated. Soil stabilization has been widely used as an alternative to substitute the lacking of suitable materials on site.

DFID (2003) describes the basic types of stabilization, indicates when it should be used, and discusses the main advantages and disadvantages of its use. The role of the sub base and other pavement layers are also discussed for both flexible and rigid pavements. DFID (2003) international publication describes some of the latest research and design methodology associated with stabilized materials used for sub-bases on heavily trafficked roads.

Types of Stabilization

There are a number of different types of stabilization, each having its own benefits and potential problems.

The types described below are those most frequently used, however, it must be noted that not all of them are appropriate for all situations.

CHAPTER THREE

MATERIALS AND METHOD

SPECIMEN PROCUREMENT AND METHODS OF EXPERIMENTS

Soil Procurement

The soil samples were collected from three different borrow pit locations in the eastern region using the hand auger and shovel at 1.2m depth below surface level. From the hand auger, the samples were transferred to black polyethylene bag to reduce loss of moisture. They were then taken to the laboratory for examination and subsequent improvement for engineering use.

The locations the samples were collected are:

Eke – Obunagu Borrow Pit, Nike, Enugu State
Egbede Borrow Pit, Aba, Abia State
Ugwuaji Borrow Pit, Nkanu, Enugu State

CHAPTER FOUR

RESULTS AND DISCUSSION

RESULTS

The next logical step is to optimize, that is, to determine the region of the important factors that leads to the best possible response. Once we have found the region of the optimum, a second experiment would typically be performed. The objective of this second experiment is to develop an empirical model of the process and to obtain a more precise estimate of the optimum operating conditions for the controllable and uncontrollable variables. This approach to process optimization is called response surface methodology

Here, the second experiment is culled from the Table 3.5 as given as Table 4.1. The controllable variables are prepared soil samples and RHA x_i, while the uncontrollable variables are Optimum Moisture Content OMC, Maximum Dry Density MDD, and California Bearing Ratio CBR.

As discussed in Section 2.4.5, the method of least square chooses the coefficients and in Equation 2.14 so that the sum of the squares of the errors between the experimental expected response ( and ) and predicted expected response ( and ) is minimized. The function L is to be minimized with respect to and .

Satisfying this condition by using equations 2.16 and 2.17, the least square method results to a system of linear equations with three unknowns constants to be determined for each of the soils obtain from the various locations.

CHAPTER FIVE

CONCLUSIONS AND RECOMMENDATION

CONCLUSIONS

The study thus concludes as follows:

Models suit A-6 soils obtained from Egbede.
Models developed are very handy and simple compared to the experimental methods.
Properties of soils such as OMC and CBR can be improved by the addition of RHA to the soil.
The optimum moisture content increases with increase in RHA.
There is decrease of MDD with increase of RHA.
RHA lacks cementing properties and should be used with lime – containing material or cement for MDD soil improvement.

RECOMMENDATIONS:

The study thus recommends as follows:

The empirical models developed may adequately be used to predict the soil – RHA properties, in the absence of experimental data for soils in the three locations.
RHA should not be used alone for stabilization of soils for pavement constructions.
RHA should be used in addition to lime containing compounds.
For pavement and foundation requirements, RHA should be used in addition to lime or cement for soil improvement.
The empirical models predict soil properties as the experimental methods, but with ease.

REFERENCES

ASTM. (1981). C618: Specification for Fly Ash and Raw or Calcined Natural Pozzolana for use as Mineral/Admixture in Portland Concrete. America Society for Material Testing .
Basha, E. A., Hashim, R., Mahmud, H. B., & Muntohar, A. S. (2005). “Stabilization of Residual Soil with RHA and Cement”. Construction and Building Materials , p. 448.
Boeteng, A. A., & Skeete, D. A. (1990). “Incineration of Rice Hull for Use as a Cementitious Material : The Guyana Experience”. Cement and Concrete Research , Vol. 20, p. 795.
Brooks, R. M. (2009). “Soil Stabilization with Fly ash and Rice Husk Ash”. International Journal of Research and Reviews in Applied Sciences , Vol. 1 (3), pp. 209 – 217.
Chandra, S., Kumar, S., & Anand, R. K. (2005). Soil Stabilization with Rice Husk Ash and Lime Sludge. Journal of Indian Highways , p. 87.
Chandrasekar, S., Satyanarayana, K. G., & Raghavan, P. N. (2003). “Processing, Properties andApplications of Reactive Silica from Rice Husk – An Overview”. Journal of Materials Science , Vol. 38, p. 3159.
Cornell, J. A. (1991). “Mixture Designs for Product Improvement Studies”. Communications in Statistics – Theory and Methods , Vol. 20 (2), pp. 391 – 414.
Croney, D., & Croney, P. (1998). The Design and Performance of Road Pavements (3rd ed.). London: McGraw-Hill.
DFID. (2003) Literature Review: Stabilized Sub – Bases for Heavily Trafficked Roads. Department for International Development.

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