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Expert: - 4/3/2010


Question
how can i control in very thick raft (3.50m)thickness to avoid high temperature borned in internal hydration of mixing concrete?

Answer
Hi Hamdy,

The main control measures are:

1. Use up to 60% cement replacement(pozzalana, pulverised fly ash, etc).
2. Keep aggregates wet or chilled and covered from direct sunlight.
3. Use ice in the mixing water.
4. Cast the raft in cooler season or at night.
5. Insulate the formwork and top surface with polystyrene blocks/sheets for up to 7 days.
6. Use thermocouples to monitor temperature differentials between the core and the outer surface. Maximum internal/core temperature should not exceed 70 deg C and the maximum differential between this and the outer surface should not be more than 30-40 deg C (or 20 deg C times distance between core and outer surface).
7. Keep concrete wet or sealed with polythene sheet to maintain high humidity.

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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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