[SEFI] Use of plastic sheet to avoid plastic shinakage crack in concrete

[ANKITA GANDHI]

Dear members.

Now a days, plastic sheet is covered on freshly laid concrete to avoid plastic cracking of concrete. Is it advisable ? What phenomina takes place when it is coverd? Does it work as steam curing or if heat is stored, does it create other problems?

Regards,

Ankita

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Structural Engineers Forum of India

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[drnsmani]

Hi Gandhi,

When water evaporates from the surface of freshly placed concrete, faster than it is replaced by bleed water, the surface concrete shrinks. This results in Plastic Shrinkage Cracking.

To prevent rapid loss of surface moisture, while the concrete is still plastic, concrete surface may be covered with plastic sheets or through use of spray-applied finishing aids. For more information on concrete cracking and other tips on concrete please visit PCA 's web site: http://www.cement.org/.

You may also refer my paper

Subramanian N., Curing – The Last and the Least Considered Aspect in Concrete Making, ICI Journal,Vol.3, No.1, April–June 2002, pp.13-20.

I am glad you raised a question on curing- which is much neglected in India- mainly due to the fact that it is not considered in the costing of a project. The performance of any concrete structure is based on the quality of concrete, which is dependent on many factors and one such factor is the quality of curing.

The other factor which is neglected is the mix design, especially the quantity of water that is added to concrete. There is no control over this, as the person who is supervising at site may not know concrete technology. These comments are pertaining to small projects, which constitute 80% of the volume of construction in India. I am afraid there is no course on concrete technology at the UG level (I am not sure about the current situation).

However there are a number of good books available in the market. My good friend Prof. A.R. Santhakumar has written a good book recently on this topic. See the link:
http://www.oup.co.in/search_detail.php?id=143963

Best wishes
Subramanian
Dr.N.Subramanian,Ph.D.,F.ASCE, M.ACI,

Computer Design Consultants: www.cdcstruct.com
Maryland, USA

See my books at: www.multi-science.co.uk/subramanian-book.htm
www.oup.co.in/search_detail.php?id=144559





--- On Thu, 8/28/08, ANKITA GANDHI wrote:

Quote:

From: ANKITA GANDHI Subject: [SEFI] Use of plastic sheet to avoid plastic shinakage crack in concrete To: gen...@sefindia.org Date: Thursday, August 28, 2008, 11:46 AM

http://www.sefindia.org/forum/viewtopic.php?p=8214#8214

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