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Expert: - 9/12/2008


Question
In gulf states when we said Grade 25 or Grade 35 concrete what does it mean? What will be the ratio (cement:sand:aggregate) for these grades? Also in Gulf temperature is very high, so what is the normal temperature for pouring a concrete here and how to control it? please answer in detail. Thanks.

Answer
Hi Muhammad,

Grade 25 means the crushing cube strength of the concrete at 28 days is 25 N/mm2. Ditto for 35, 40, 50, etc. The higher strengths are achieved by proper choice and grading of aggregates, a low water-cement ratio and higher quantity of cement, and possibly by use of admixtures. You need to read up about design mixes as that is too complex a subject to discuss in this website.

There is a good guide produced by CIRIA for concrete in the Gulf- you will find it by going to www.google.com


For casting concrete during hot weather you need to cool the aggregates, use iced water and also shade the areas being concreted- best to do large pours during the night hours.

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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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