The first day we started with plywood handsets. To determine the pour rate of a concrete wall we examined each of the components that make up the wall. For example, we started with the hardware that attaches to the tie. I didn't know what a john-a or a steel pressed wedge is good for so I used the premise that in thirty four years I have not seen either one of them fail therefore they must be good for a minimum of 3,000 psi. Next the wall ties are good for 3,000 psi (unless they are special order 5,000 psi ties.) That means if the ties are sixteen inches on center we could use a pour rate of sixteen feet per hour.

The next item is the 2x4 waler. Usually Douglas Fur is used. The chart that I have says that if you are willing to accept ¼" deflection you could use a pour rate of seven feet per hour. Seven ply ¾" plywood is positioned so that it is perpendicular to the waler. The walers are sixteen inches on center on the plywood and we won't accept more than 1/16" deflection between the walers, the pour rate would be about two and a half feet per hour. (Plywood is the weakest link.)

When it comes to inside corners, usually plywood gussets with 8 penny duplex nails hold them in place (see picture #1) and the outside corners are held in place with 2x4's and sixteen penny nails. (See picture #2) The shear value of a 16 penny nail through Douglas Fur is 189 psi. So if we poured a 2 1/2 foot lift of concrete in a twelve inch wide wall and the ties were 16 inches away from the end of the wall then we would need to have 4 nails driven through the walers and the 2x4 at the end of the wall. More often than not, those pouring the wall pour the lifts more than 2 1/2 feet per hour, but more like 4 or 5 feet per hour. That's why we always log cabin the corners with 12 nails at the walers every 16 vertical inches. (See picture #1.)

There are a couple of reasons not to exceed the recommended deflection rate on plywood. The first is because the plywood is glued together with brittle glue. As the plywood deflects or bends, the outer layer bends more then the inner layer causing the glue to crack and delaminate from the wood a little. This weakens the plywood and the next time the plywood is used it will deflect more under the same pressure. The second reason is this causes pillowing. For a structural wall this is not serious as long as the plywood doesn't deflect more than the allowable amount for the classification of the wall. If the wall is architectural, then the shadows that are cast by the sun make the wall not very appealing.

Additionally, if the wall you are pouring is 32 feet high (see picture #3) and you pour at the rate of 2 1/2 feet per hour, it will take you almost 13 hours to top it off. This is where set rate comes in. If you can make a 2 ½ foot lift every 45 minutes, then you can finish in about 8 1/2 hours.

Some of the things you can do to increase set rate are:

• Remove fly ash
• Increase powder
• Use type III cement
• Reduce water with a high range water reducer
• Add hot water
• Use a non chloride accelerator

Just remember that when you are playing with set rate, you're playing with fire. If any thing goes wrong, i.e.

• Stuck vibrator
• Vibrator burns up
• Workers operating vibrators can't keep up with pour rate
• Form work blow out
• Power quits because: wet GFI keeps tripping, generator goes down, cords go bad, power panel goes bad, too many cords, not enough circuits
• Pump truck brakes down, plugs up
• Concrete trucks get delayed i.e. traffic, bad roads, driver stops for lunch, driver can't find project, truck brakes down
• Batch plant brakes down
• Batch plant over booked
• Other pours have priority over yours

or many others they can make your wall look like #%*&?! So be careful and have fun.

Happy Valentines Day!

Ray

P.S. There's gold in them th'ar hills