Evaluating Adaptability of Design Procedures for Concrete Pavements in Kenya

1. IEK INTERNATIONAL CONFERENCETheme: The Role of Engineering Practitioners in the Implementation of the Constitution Title: An Assessment of the Adaptability of Empirical & Mechanistic Design Procedures for PCPs in Kenya P. O. Jangaya Moi University

2. Introduction • Generally, CC roads are associated with high initial construction costs, and low cycle costs compared to AC roads. • Types of CC? “cheapest”. • As at “1st ¼ of 2010”, cement concrete roads constituted approximately 0.002 % of Kenya’s road network – Mbagathi Way, NRB

3. Introduction • CC design procedures: Empirical, mechanistic & mechanistic-empirical. • Empirical: based on long term experience with concrete roads -> adequate experimental data. • Mechanistic: based on mathematical models of material behaviour and determination of stresses within the structure -> ‘new’ countries.

4. Introduction • Practice • Empirical: e.g. Germany (described by RStO 01 (2001) & revised after every 10 years), Austria and Belgium. • Mechanistic: e. g. the Netherlands, South Africa, and Canada. . Major works done at Mbagathi Way, BUT not first one.

5. Mbagathi Way in brief • Approx. 3 km long, built in 2006 – 2007 • Design done based on S.A. design procedure • 210 mm thick DJPC pavement done by Kabuito Contractors Ltd

6. What next after REHAB? • Monitoring program? • Development of own design code? • Evident in draft from Ministry of Roads in 2009 • In this document, -- a lot of borrowing from what is already available from other countries especially from South Africa. • Why the heavy borrowing? • Any progress on this draft?

7. My contribution • 2010 IEK Conference • Why the literature survey? • Clauses from the draft. • to make objective & informed decision(s) for adoption/adaption.

8. German design procedure Alternative designs of CPs for German expressways for heaviest traffic loadings and a frost-proof pavement structure of 900 mm: (1) concrete pavement on cement-bound base (2) concrete pavement on geotechnical fabric and cement-bound base (3) thick concrete pavement on crushed aggregate base

9. Traffic loadings: Axle loads, Directional factor, Design traffic lane, Substructure: Modulus of substructure reaction Concrete: Strength Parameters, Elastic modulus Climate:Temperature gradients Temperature gradient stresses: Eisenmann/Dutch method Traffic load stresses: Load transfer at joints, Westergaard equation Concrete slab thickness: Miner fatigue analysis Dutch design procedure

10. Adaptability to Kenya • Parameters considered, include: • traffic loadings; • temperature gradients (climate); • concrete grades; • Characterization of substructure;

11. Conclusion • Kenya, just starting to appreciate use of CC, needs: • design procedure which allows the use of a country’s nationally determined parameters for inclusion in its models • procedure should also be one that does not require a lot of field data (experience)

12. Conclusion • Dutch “better” addresses: • overloaded trucks, • temperature variations – what’s required, • concrete grades • German “better” addresses: • characterization of the substructure

13. Issues • Do we need monitoring program for Mb. W • Any challenges with Mbagathi Way • Progresses with the design codes.

14. Appreciation & Acknowledgement IEK Conference organising committee VLIR-UOS MU-K CSE project Moi University Session & programme chair

15. END!! Thanks