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CURING

CURING

(OP)
Waht do you suggest best method to cure structural slab in
hot weather and cold weather

RE: CURING

Wet curing is best method.  If used in cold weather, must be used in conjunction with auxiliary heat source to prevent freezing.  If no heat source available or practical, use burlap blankets, straw, sand, etc. to maintain moisture in slab.

RE: CURING

To prevent plastic cracking in hot weather, you better use a white plastic foil to prevent heating of the surface and drying in very few minutes after placing the concrete. When the concrete gets a little of strength, you can remove the foil and use wet covers. If you could pour water on the foil so that a pool with a few milimiters of depth is created, you won't need to remove it. In the cold weahter, you have to prevent concrete to go lower than 5 degrees centigerad. So you better use blankets on the surface of the slab. If the weather is freezing, you better use a heating source together with the blanket.

RE: CURING

We always try and encourage our contractors to use plastic covering to cure concrete. You can use burlap, sacking, hessian etc. but you have to keep it wet and let's face it who is going to keep wetting it every few hours if the engineer is not around. At least with plastic you know most of the water will be retained and certainly all the water the cement needs for reaction will be retained. The excess water will condense under the plastic and you will get excess vapour pressure under the plastic discouraging the water the concrete needs from leaving. I would be very wary of anything that relies on people doing something regularly particularly if those people don't really see the point of it. Obviously this doesn't apply to very cold climates.

Carl Bauer
www.bauerconsultbotswana.com

RE: CURING

Is this functional?  When a slab is poured, build about a 2" dam around the edge and then  put a water hose with a level switch to maintain the water level.  Should work in temperatures above freezing and you wouldn't have to worry about someone not wetting it down.  Does anyone know how fiber in concrete impacts the curing process?
ken ballard, pe
you@surfbest.net

RE: CURING

On a project I was on, the contractor used a synthetic spray-on coating.  A thin film was applied (with a device simiar to a hand held pesticide sprayer) just after finishing. It drys similar to a plastic coating.  Not sure what it is made of (it is stinky as hell) or how good it prevents moisture loss--seemed pretty good though for long narrow strips.

RE: CURING

"you"....yes, damming and flooding is a great curing method, as long as you accommodate the removal of the water and prevent freezing, erosion.  It is one method of wet curing.

As for fiber, it has no real impact on curing other than to enhance the crack control a bit in the initial stages.  Functionally, it does nothing to the chemical curing process.

a3a...the material you mention is made from either a wax-like petroleum derivative (one form), a polymer, or a combination.  These "curing compounds" are intended to prevent evaporation of interstitial water from the slab.  They are better than nothing, but do not compare well to wet curing.

RE: CURING

"Ron"... Could the material that a3a mentioned be boiled lindseed oil?  If not, do you have some names of the product and a locatiion where I could obtain some more info.  Might be less expensive and more functional than the damming and flooding.  thanks
ken ballard, p.e.
you@surfbest.net

RE: CURING

Ken,
W. R. Meadows Company has curing compounds (www.wrmeadows.com) and Sealmaster (www.sealmaster.net), and others (I believe Thoro products has one, etc.).  These curing compounds will run about $10/gallon (US).

Boiled linseed oil was used at one time, primarily as a form release agent, but could be sprayed on the surface of the concrete for curing.  Its obvious disadvantage was its slipperiness and cleanup.  

Ron

RE: CURING

Ron,

Appreciate the informations. Have sent request to WRMeadows and SealMaster for specfic information on their 'curing' products. Also asked if they handled fibers and coloring for concrete.

Last Winter, my concrete diveway scaled after twenty five years of surviving this Ok. weather.   After chipping all the lose stuff, I patched it with some fiber reinforced concrete and then applied a coat of BOILED LINSEED OIL for a sealant. It is not the best looking driveway, but it is holding up very well.

Plan to construct a new house out in Ca.  That is the reason for the questions.

ken ballard, p.e.
you@surfbest.net

RE: CURING

Wax based curing compounds are very effective, but can interfere with the application of some types of floor covering. We don't used much water curing in our area due to the highly expansive clays beneath our slabs.  The water used in curing seems to find its way to the adjacent soil no matter what you do.

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