Investigation Of Subgrade And Performance Characteristics Of Cementtreated Base Materials For Road Pavement System Enhancement: A Case Study In Addis Ababa

Abstract

In Ethiopia, Conventional Asphalt Pavements With Granular Base And Sub-Base Layers Often Face Issues Like Premature Deterioration, High Maintenance Costs, And Poor Drainage. These Problems Stem From Factors Such As Substandard Construction Practices, Weak Subgrade Strength, And Overloading, Leading To Rutting And Fatigue Cracking. This Study Investigates Cement-Treated Base (Ctb) As A Viable Alternative To Improve Pavement Performance And Reduce Costs. A Thorough Subgrade Assessment Was Conducted, Including Soil Classification, Compaction, And Strength Testing To Meet Engineering Standards. Ctb Provides Several Advantages Over Traditional Base Materials, Such As Increased Structural Capacity, Enhanced Resistance To Cracking, And Improved Fatigue Performance. Its Stiffer Base Minimizes Deflections Under Heavy Traffic, Extending The Pavement???S Lifespan. Additionally, Ctb???S High Bearing Strength Allows For A Thinner Base Layer, Which Optimizes Material Usage And Accelerates Construction. Mechanical Testing Showed That A Cement Content Of 5% Yielded An Unconfined Compressive Strength Of 5.22 Mpa, Within The Target Range Of 4.5???7 Mpa, Resulting In A Mix That Effectively Resists Deformation And Distributes Loads. Microstructural Analyses Using X-Ray Diffraction (Xrd) And Scanning Electron Microscopy (Sem) Identified Calcium Silicate Hydrates (C-S-H) As Critical Components Contributing To Ctb???S Strength And Durability, With Sem Images Displaying A Dense Microstructure That Enhances Crack Resistance. Performance Assessments Using Iitpave Software Indicated That Ctb Outperforms Conventional Materials In Reducing Subgrade Rutting And Fatigue. Cost Analysis Revealed That Ctb Is Approximately 15-20% Less Expensive Than Traditional Granular Base Systems Due To Its Increased Load-Bearing Capacity, Allowing For A Thinner Layer And Reducing Material And Construction Costs. Furthermore, Numerical Modeling With Plaxis 3d Demonstrated That Using Ctb As A Base Layer Significantly Reduces Settlement Compared To Dense Bituminous Macadam (Dbm), Particularly When Supporting Asphalt Concrete (Ac) And Soil Layers. This Supports The Concept Of An Inverted Pavement System, Where A Ctb Layer Under Asphalt Minimizes Settlement And Enhances Load-Bearing Capacity, Offering A Cost-Effective And Durable Solution For Ethiopia???S High-Traffic Roads With Weak Subgrades.