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Expert: - 11/21/2009


Question
QUESTION: dear sir,
       what  is the criteria  for core cutting test.? on how many days test result this  is recommended .? can it be done after  threemonths casting  of  raft foundation.ply  reply  soon.
its  urgent.

ANSWER: Hi Raj,

Yes, you can cut cores anytime after 7-14 days (so long as concrete is hard enough not to disintegrate). Normally, they should be extracted and tested at 28 days strength, but 3 months is also OK. Remember that concrete continues to gain strength after 28 days, so this factor needs to be kept in mind.

---------- FOLLOW-UP ----------

QUESTION: sir,
   please give me details of the factors in relation to no of  months .? and also what can be the maximum permessible  time limit for core cutting test.
please reply soon

Answer
Hi Raj,

The strength gain after 28 days depends on several factors, including method and length of curing, ambient conditions, mix design, ingredients (additives), etc. In general, you can count on additional strength gain of between 5-15% of the specified 28-day strength over a  period of several months. See the Q&A below, which gives some more details:

http://uk.answers.yahoo.com/question/index?qid=20090222081430AARqmGR

There is no time limit as to when you may take core samples.  

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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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