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-   -   how long to cure before using wedge anchors (http://www.diychatroom.com/f105/how-long-cure-before-using-wedge-anchors-190071/)

ugabulldog 11-10-2013 09:21 AM

how long to cure before using wedge anchors
 
I poured a footing yesterday with quikrete and want to install post brackets with wedge anchors, how long should I wait?

stadry 11-10-2013 09:32 AM

how thick's the footing & how close to the edge for anchors ?

ugabulldog 11-10-2013 09:33 AM

Quote:

Originally Posted by itsreallyconc (Post 1264794)
how thick's the footing & how close to the edge do you want do drill for the anchors ?

8" footing, wedge anchor is only 4", at least 6" from edge.

stadry 11-11-2013 05:34 AM

curious why no j bolts in wet conc ? quikcrete suggests a diy project - what's your goal ? ?

Mr Chips 11-16-2013 10:18 PM

You really shouldn't drill or install wedge anchors in concrete less than 28 days old

Tscarborough 11-17-2013 08:38 PM

That is not correct, Mr. chips, I have installed many anchors the next day. What matters is the distance from the edge, not the age of the concrete. Under your circumstance, I would drill them asap and set the anchors, but not tighten them for a couple of days if possible.

Mr Chips 11-17-2013 09:51 PM

Because you can doesn't mean you should. I have never seen any wedge anchor manufacturer publish any load values for wedge anchor in green concrete. How much an anchor will hold is based on the several factors, one being the compressive strength of the base material. Uncured concrete has unknown compressive strength. Under your scenario the wedge anchors are unset and you might as well drill holes and just drop bolts into the holes

Tscarborough 11-17-2013 10:12 PM

The cure (and hence the strength, of which we care about the tensile, not the compressive in this instance) of concrete is not a linear function. Concrete will reach 50% of it's final strength within a day or 2, 75% within a week, and not reach it's complete strength in our lifetime.

The OP is setting posts, not securing girders supporting a highway bridge, and it goes with the workflow to set said posts and anchors as soon as is practical. If the OP drills the holes and sets the post brackets, he can proceed with his project and tighten them the next day or two with no issues.

Arkitexas 11-18-2013 06:36 PM

Standard concrete reaches 50% design strength in approximately three days, 75% in about 7 days, 90% in about 14 days, and 100% in about 28 days. Concrete technically never ceases getting harder but after 28 days the increments become so small as to not be useful. The above percentages vary depending on the temperature, curing conditions, and mix additives.

If you install wedge anchors the day after you cast the concrete, it is at only 25% to 30% of its 28 day strength and you run the risk of obvious fracturing or something even more subtle. Wedge anchor design relies on the concrete in the anchor hole to NOT move but rather "push back" (resist) the anchor's sideway pressure. This pressure is what holds the anchor in place. The greater the pressure between the concrete and the anchor the stronger the anchorage (until the anchor pressure exceeds the shear strength of the concrete). As some suggest here, green concrete (that which has not fully cured) may in fact not fracture under load from a wedge anchor but green concrete is still somewhat pliable and it will move under pressure from the anchor by essentially enlarging the anchor hole. This results in reduced pressure at the anchor, and ultimately weakens the connection. In building construction we never permit structural wedge anchors to be set or cast-in-place anchors to be loaded before the concrete has set for 28 days. If you are in a rush, wait at least a week when the concrete is at 75% strength. If your anchor is not carrying any appreciable load it may be ok. If you want it to be strong.. wait.


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