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Department of Civil and Construction Engineering
Submitted by: Adoyo Felix O tieno
A thesis submitted in partial fulfillment for the Degree of Master of Science in Civil Engineering in the department of Civil and Construction Engineering, University of Nairobi.
October 2012
This thesis research is my original work and has not been presented for a degree in any other university
Adoyo Felix Otieno Reg. F56/65073/
This thesis research has been examined with my approval as university supervisor
Acknowledgement Special thanks to Prof. S.K. Mwea for his helpful guidance and encouragement throughout this research. Prof. Gichaga J. Francis whose lectures on pavement evaluation inspired me to undertake this research is greatly appreciated. Prof. Mbeche O.O. is appreciated for his guidance on research methodology and for presentation guidelines. Special gratitude The Chief Engineer, Ministry of Roads, (Materials Department) and Eng. Wanyiri for offering guidance and conducting deflection measurements and concrete strength tests. Special thanks to Albert Ndege who helped in data analysis. Thanks to the following staff members of Civil and Construction department of the University of Nairobi whose comments and opinions helped to shape up this research: Dr. Mumenya S. Wanjiku, Eng. D.M. Wanjau, Eng. D.O. Koteng' and Prof. Nyangeri E. Nyanchaga.
Special thanks to my dear wife for contribution in preparation of this research and emotional support throughout the entire duration of the thesis and to my daughter Nicole for her valuable encouragement.
Special appreciation to all the second year data collection enumerators from Kenya Polytechnic University College of The University of Nairobi for taking time and effort that resulted in the success of this research.
Dedication
This work is dedicated my loving mother Penina Adhiambo Nyakiti for all the sacrifices she made in my education. May the Almighty Father reward you according to his bountiful promise.
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List of Figures
List of Appendices Appendix I Appendix II
Appendix III
Appendix IV
Homogeneity of concrete on Mbagathi Road Procedure for determining present serviceability ratings The existing pavement structure in Mbagathi Road Falling Weight Deflectometer Results
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List of Abbreviations AASHTO - American Association of State and Highway Transportation Officials ADT - Average Daily Traffic CBR - California Bearing Ratio CRCP - Continuously Reinforced Concrete Pavements EACPA - East Africa Cement Producers Association EUPAVE- European Concrete Paving Association FWD - Falling Weight Deflectometer JCP - Jointed Concrete Pavements KURA - Kenya Urban Roads Authority LHS - Left Hand Side (Langata road to Ngong road side) RHS - Right Hand Side (Ngong road to Langata road side) M.O.R -M inistry of Roads NCDOT-North Carolina Department of Transportation NDT - Non Destructive Test PCA - Portland Cement Association SANRA-South African National Roads Agency Limited RDC- Radius of Curvature UNON - United Nations Office in Nairobi
WTIC- Wisconsin Transportation Information Centre
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noise and the relative difficulty of repairing concrete roads compared to asphalt is a major disadvantage (EUPAVE, 2009).
Mbagathi road is not the first concrete pavement in Kenya but is the first concrete road that the Government has taken ownership of. The project involved white-topping funded by the Government through proceeds from Road Maintenance Levy Fund. The project involved overlay of the 6km dual carriageway through provision of 205mm thick dowel jointed concrete pavement, construction of access and cross culverts, construction of a new footbridge, construction of 3m footpaths in concrete paving blocks and the provision of street lights.
1.2. Description of the Study Area Mbagathi Road is located in Nairobi City, the capital city of Kenya and covers an area of 696 km2 at an elevation of 1,661m with an estimated population of 3,138,295 and population density of 4,509 persons/km2 (CBS, 2009) making it be the most populated city in East Africa. Nairobi is also the headquarters for the UN in Africa & Middle East, the United Nations Office in Nairobi (UNON).
Mbagathi Road is approximately 6km dual carriageway and starts at Langata Road (C58) roundabout, passing next to Nyayo Highrise estate, Kenyatta Market and ends at Ngong road (C60) roundabout at City mortuary next to Kenyatta National Hospital. Mbagathi Road was initially designed as a flexible pavement in 1970s and the main works executed between the year 2005 and 2006 comprised rehabilitation of the carriageway with cement concrete overlay on the following existing pavement layers:
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ii. Completely failed sections which exhibited complete pavement failure. The existing failed pavement was entirely removed and a 300mm hand packed stone base was provided.
1.3. Statement of the Research Problem Concrete roads can last over 20 years without any major maintenance (EUPAVE, 2009). However, Mbagathi road has lasted 5 years and yet observations that have been made on the road have shown widespread deterioration of concrete pavement slabs and joints. Among other defects, the following have been observed:
Cracking of pavement slabs as shown is Figure 1.1. 'r Widening of the joints due to infiltration of particulates and water into joints as shown is Figure 1.2. ^ Ponding of water was observed in a section next to the bridge due to rains and poor drainage. Damaged kerbs and polished outer lanes on sections of the road as shown is Figure 1.3.
Fig. 1.1: Pavement cracking of concrete slabs at Mbagathi Way
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1.4. Research Objectives This research will be based on the following objectives. i. To determine the relationship in the observed deterioration of Mbagathi Road with the performance of concrete slabs forming part of Mbagathi Way. ii. To conduct a pavement condition survey and hence investigate the causes of the following observed defects on Mbagathi Way a. Failure and Widening of joints b. Cracking of concrete pavement slabs c. Water ponding along sections of the road iii. To determine magnitude and pattern of deflection of pavement slabs and dowel joints on Mbagathi Road as a measure of the performance of the road and further to determine the value of initial deflections that will form the basis of further research.
1.5. Justification of the Study Mbagathi Road was opened to traffic in 2006 and has operated without any major maintenance whereas distress features have been observed on the road hence indicating deterioration. An evaluation of distresses on Mbagathi Road provides insights into methods on improving the design and construction of rigid pavements in the region and forms a basis for future research on the road.
Mbagathi Road project was implemented through co-operation between the Ministry of Roads and cement producers in order to show engineers that roads constructed of concrete would perform better than flexible pavements. However, since its construction there has not been any documented evaluation of the road despite it having been the first concrete pavement which the government actively participated. This evaluation has expanded knowledge and expertise on Mbagathi Road and rigid pavements in Kenya.
Owing to scarce pertinent data on evaluation and performance of concrete pavements in Kenya and given the several roads in Kenya which would ordinarily be constructed on concrete for example roads forming the northern corridor due to heavy truck loads, this research has provided data on performance of rigid pavements in Kenya and 5
methodologies to be applied for evaluation of rigid pavements for other researchers and highway engineers.
Improvement to infrastructure is key to the realization on Kenya Vision 2030 and Nairobi Metropolis plans. Infrastructure is one of the four pillars of vision 2030 and hence knowledge on performance of concrete roads is paramount in decision making for road improvements and new construction (Ministry of Nairobi Metropolitan Development, 2008). Economic appraisal with cost-benefit analyses will be better understood when comparing several improvement alternatives with clear performance indices for the alternatives. When one of the alternatives is concrete roads, this research is useful for performance indices of rigid pavements.
1.6. Scope and Limitation of Study This study was conducted within the following scope: i. Deflection measurements using Falling Weight Deflectometer at 100m intervals along Mbagathi Road. ii. Pavement condition survey of Mbagathi Road. iii. Determination of traffic loading on Mbagathi Road by conducting a 7-day traffic survey. iv. Determination of in situ concrete slab homogeneity by non-destructive methods.
Deflection study was limited to initial baseline investigation upon which further research will be based. The determination of stresses in the pavement was limited to interior stresses only.
Traffic loading was carried out using the assumption of no overloading. Actual axle loading surveys were out of the scope of this study and hence legal limits of vehicle equivalence factors have been employed in traffic analysis.
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