THE 20TH ENGINEERS’ INTERNATIONAL CONFERENCE Tom Mboya Labour College, Kisumu, Kenya 8 – 10 May, 2013
IEK CONFERENCE DESIGN FOR STRENGTH OR DURABILITY G.Nganga, M.Alexander, H.Beushausen and S.Mumenya 9TH MAY 2013
Outline • Introduction • The South African durability index (DI) performance-based approach • The Gauteng Freeway Improvement Project (GFIP) • The design for durability in Kenya • Conclusion
Introduction • 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.
Durability Index Tests • 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
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 • 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 2.1.3 • Durability, workmanship and materials
Conclusion • 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.