\curing concrete with Curing compounds 6

[JECCNC]

I have a contractor who wants to use curing compounds instead of water to cure concrete, I have not used these compounds before and know nothing about them, my qustion is:
1- do these compounds totaly replace water, or are they used togethr with water
2- are they applied for 7 days like water , or once only and the work continues? if so how can you tell that the concrete has reached its strength
3- are they effective
thanks

 

[tolchijb]

My understanding, and I'd like to hear what others know, is that a curing compound basically creates a barrier to keep mix water in the concrete and outside water out of the concrete. There are a several different varieties. The ones I am familiar with need to be blasted from the surface before any water repellant or the like can be applied to the surface. There are other low VOC varieties that will break down in the sunlight and theoretically do not need to be blasted from the surface. I am not sure how I feel about that.

To get back to your questions, I believe they eliminate the need to wet cure (not positive about this), they are applied once and your done, and, depending on the variety being used, I believe them to be very effective. The strength of the concrete is still measured in the typical fashion. The idea being that the design mix is intact since nothing can get in or out through the curing compound barrier, so cylinders should be accurate.

 

[SkiisAndBikes]

Curing compounds are generally applied to the top surface of flatwork to assist in curing of the concrete. They have their good points and their limitations. My preference if I was going to choose between the two would be to wet cure.

Typically they are spray applied once. There can be issues if sealers or coatings are to be applied afterwords.

My main issue with curing compounds is the application. Time and time again the concrete gets a quick spray and the contractor is done. I was onsite for a demonstration by a sealer manufacturer. The stipulated coverage rate meant a heavy spray in each direction, something I had never seen applied onsite before. The effectiveness of the sealer decreases rapidly if the coverage rate is not met.

 

[SlideRuleEra]

Agree with SkiisAndBikes. Curing compounds are effective, if applied correctly. This is not always done. They can be substituted for a wet cure and they are used without water. The only time that I prefer to use them is on surfaces (such as walls, when the forms need to be removed for immediate reuse) that are difficult to wet cure. Here is a brief comparison of various curing methods by the Portland Cement Association:

http://www.cement.org/tech/cct_curing.asp

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[hokie66]

This is an Australian reference, but applies anywhere. Note the poor performance of the PVA curing agents. The wax emulsion and chlorinated rubber curing compounds do a good job, but are hard to remove if applied finishes follow. Also, I think the chlorinated rubber has some health and safety issues. Nothing like good old ponding for curing concrete, but that is hard to achieve on site.

 

[hokie66]

Forgot the attachment.

http://www.concrete.net.au/publications/pdf/Curing06.pdf

 

[Ron]

hokie66 nailed it....read it twice!!