Predicting CBR Values of Black Cotton Soil Stabilized with Cement and Waste Glass Admixture Using Regression Model

Ibrahim Abdulkarim Ikara

doi:10.11648/j.ajtte.20190401.15

Abstract

In highway constructions, sub-grade and sub-base soil stabilization has been used as one of the prime and major process for many years in order to improve the engineering properties of soil. The strength of theses layers is indicated by their California bearing ratio (CBR) value which is quite expensive and time consuming. In order to overcome this situation, this study presents a methodology for predicting soaked California Bearing Ration (CBR) value of Black Cotton Soil Stabilized with Cement and Waste Glass Admixture using Multiple Regression Analysis (MRA). Experimental test results such Atterberg limit (Liquid limit (LL), Plastic limit (PL) and Plasticity index (PI)), Compaction characteristics of two compactive efforts namely standard proctor (SP) and modified proctor (MP) (maximum dry density (MDD) and optimum moisture content (OMC)), CBR, Waste glass (WG) content and Cement content (Cm), obtained from a laboratory at Abubakar Tafawa Balewa University Bauchi, Nigeria, have been employed in developing multiple regression models. California Bearing Ration was taken as the dependent variables while Liquid limit, Plastic limit, maximum dry density, optimum moisture content, waste glass content and Cement content were taken as independent variables. The regression analysis calculated the error mean square (MSE) for each possible model, and models with large MSE were not selected for the best regression equations. The best models have a minimum value of MSE occurring for the six-variable model (Cm, WG, LL, PL, OMCsp, MDDsp) and (Cm, WG, PL, LL, OMCmp, MDDmp) with a corresponding higher value of coefficient of multiple determination R2 = 0.98 and 0.94. The performance evaluation of the fitted regression models indicates a strong correlation (R2 = 0.89 - 0.98) between the mentioned variables, and the model equations developed from this work provided a very good prediction of the response, as the equations can be employed for making estimates of soaked CBR of other black cotton soils having similar geotechnical properties.

Highlights

In order to improve the strength properties of Black cotton soil, several types of stabilized materials are used as base courses, sub-base courses, or treated sub-grade for highway pavements, [1]
To conduct a California bearing ratio (CBR) test, representative soil sample has to be collected from the selected location, from which a remoulded specimen has to be prepared at predetermined optimum moisture content (OMC) and maximum dry density (MDD) with standard or modified proctor compaction energy as the case may be, for the test to be conducted
The CBR was used as the dependent variables, while MDD, Waste Glass (WG), Cm, LL and PL were used as independent variables

Summary

Introduction

In order to improve the strength properties of Black cotton soil, several types of stabilized materials are used as base courses, sub-base courses, or treated sub-grade for highway pavements, [1]. These include cement stabilized or treated aggregate, soil cement, lime-cement fly-ash, and limestabilized materials. The CBR values of these materials is used for pavement design purpose. Highway pavement is a relatively stable supper-imposed layers of materials, constructed over the natural soil for supporting and distributing wheel loads and providing durable wearing surface for transportation and economic development of a country, [2]. The California bearing ratio (CBR) test is an empirical method used in design of flexible

Methods

Results

Conclusion