Civil Engineering/Civil

Advertisement

Expert: - 2/22/2009


Question
Hi,
I am QC inspector. I want to prepare a presentation. I need some tips for that. Can you please tell me the problems caused by below listed bad practices in a construction site.
1)Discontinuing concrete curing before 7 days.

2)Commencing protective coating  around concrete structures before completing the curing period.

3)Back filling before protective coating has been dried out.

4)Adding water to ready mix concrete at site.

5)Pouring concrete even though the mix has been exceeded the expiry time

6)Back filling as mass fill instead of filling layer by layer & compacting

7)Back filling without proper moisture content.

Thanks & regards,
Mohamed Nousar.

Answer
Hi Nousar,

Briefly, here are my answers:

1. This can cause cracking due to shrinkage and also "surface crazing", which is a series of small cracks in a random pattern.

2. This can cause bubbling of the waterproofing layer as the curing releases gases that cannot escape. So this will compromise the waterproofing. In addition, the coating may not adhere properly to wet or un-cured concrete.

3. This can damage the protective coating as it may not have gained full strength.

4. This can cause segregation of the aggregate and also may lead to un-controlled water:cement ration, which is so critical to achieving good concrete.

5. This can lead to either lack of proper compaction, so lack of bond with the rebar. It can also cause excessive honey-combing.

6. This can create voids in the back-filling and so in future it can result in excessive settlement.

7. This can result in compaction that is not optimum, and hence result in excessive settlement in future.  

Civil Engineering

All Answers

Answers by Expert:

Ask Experts

Volunteer

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)

©2012 About.com, a part of The New York Times Company. All rights reserved.