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Civil Engineering/cracks in structures

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Expert: - 7/20/2008


Question
I am a quality control engineer and I notice we keep getting a lot of cracks in our box culverts and median barriers. I also realize that the C30/20 mix that we use gives a very high strengths, an average of about 55 but the concrete at the pours normally have a very high temperature too, averaging over 33 degree cel. What is your impression of how I could prevent some of the shrinkage cracks. We use a lot of curing compound and plastic

Answer
Hi Courtney,

This could be due to several reasons, such as very thick or very thin concrete cover to rebar, outer rebar being too large in diameter or too far apart, the section being thick and outer temperature dropping rapidly compared with the core, the water cemnet ratio being too high, the curing not being done for long enough, etc. The following website will give you further clues as to how you may get over this problem:

http://www.concretenetwork.com/concrete/preventing_concrete_cracks.htm

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Arshad Khan

Expertise

I can answer any questions to do with civil and structural engineering consultancy and construction industry in East Africa and the Middle East, and specifically with the analysis and design of reinforced concrete structures. My particular expertise is in the aseismic design and optimisation of tall buildings.

Experience

Employment history: 36 years in Construction and consultancy in the UK, Kenya, Tanzania, Uganda, Ethiopia, Eritrea, South Africa, Somalia, Zambia, Austria, Bahrain, Kuwait, Doha and the U.A.E.

Organizations
.Fellow of Institution of Structural Engineers (UK) .Fellow of Institution of Civil Engineers(UK) .Member of the Institution of Engineers, Kenya .Registered Engineer, ERB, Kenya .Member of the Architectural Association of Kenya (Engineers Chapter) .Chartered Engineer (UK)

Publications
•1984: International Conference on the Art and Practice of Structural Design, London •1994: 3rd Int. Kerensky Conference in Structural Engineering, Singapore •2008: International Conference on High-Rise Towers, Abu Dhabi

Education/Credentials
BSc, 1st Class Hons, in Building Engineering, University of Bath, UK MSc in Concrete Structures and Technology, University of London. Diploma of Imperial College, UK.

Awards and Honors
•Science Congress Special Award (for 2-seater Hovercraft - 1968) •Institution of Civil Engineers Award for outstanding performance at Bath University (1975) •Concrete Society Postgraduate study Bursary Award (1976) •Consular Representative for British High Commission, Nairobi. (1995 to 1998) •Examiner for Institution of Civil Engineers Professional Interviews, Nairobi. (1997 to 1998) •Branch Representative in Vienna for PI assessment for Inst. of Struct. Engrs. (1999 to date)

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