1 THE 20TH ENGINEERS’ INTERNATIONAL CONFERENCE Tom Mboya Labour College, Kisumu, Kenya 8 – 10 May, 2013

DESIGN FOR STRENGTH OR DURABILITY G.Nganga, M.Alexander, H.Beushausen and S.Mumenya IEK CONFERENCE 9 TH MAY 2013

Outline 3 Introduction The South African durability index (DI) performance-based approach The Gauteng Freeway Improvement Project (GFIP) The design for durability in Kenya Conclusion

Introduction 4 Lack of durability in reinforced concrete structures due to corrosion. The main approach in control of quality of reinforced concrete structures is through a measure of strength. However, the durability of reinforced concrete structures is dependent on penetrability of the concrete cover. Strength is therefore an inadequate quality control criterion and to ensure durability the penetrability and thickness of the concrete cover should be verified.

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Durability Index Tests 8 The three durability index tests  Permeability Oxygen Permeability Index test (OPI)  Sorptivity Water Sorptivity Index test (WSI)  Conductivity Chloride Conductivity Index test (CCI)

Durability Index Approach (Contd ) The application of the test in performance- based design The development of the durability index test approach in performance specifications 9

Gauteng Freeway Improvement Project Implementation of the durability index performance approach in the GFIP Improvement of durability index performance- based specifications

Design for Durability in Kenya 11 Design for durability in reinforced concrete structures in Kenya Approaches that can be adapted from the South African durability index performance- based approach.

Design for Durability in Kenya (Contd ) BS 8110 Part 1, 1997 Section  Durability, workmanship and materials 12

Spacer Blocks 13

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Conclusion 16 Quality control and specifications for spacer blocks Mix design for durability, not for strength only Need for service life prediction as a requirement in engineering practice. DI approach can be modified accordingly in order to develop a Service Life Prediction Model for Kenyan environment. Adoption of the South African DI approach to design of structures and perform necessary modifications for Kenya’s environment, particularly at the Coastal region.

THANK YOU 17