Troubleshooting Concrete

      

TROUBLESHOOTING PROBLEMS:
Below is a list of problems that can occur when working with concrete mixtures. They may be helpful when you get into trouble:

Too much, too little water-
One problem that you will soon figure out is that the more water is added to the mix, the easier the mix is to work, and also the easier it is to place the mix into the forms.

Try pulling the concrete up in a series of ridges with a hoe. If the ridges slump back down and can't be seen easily, there is too much water. If you cannot create distinct ridges, there is too little.

Poor mixing-
Make sure you have mixed all the ingredients properly and thoroughly, scraping them from the sides and bottom of the mixing box. The concrete mix should be an even color. Light or dark streaks indicate poor mixing.

Remedying a poor mix-
If the mix is too wet, it doesn't have enough sand and aggregate for the amount of cement paste. Add 5 to 10 percent more sand and aggregate, mix it well, and test. Repeat this until the mix is correct. Keep careful notes of the added amounts; when you make the new batch, you will follow the revised figures for sand and coarse aggregate.

If the mix is too stiff, it has too much aggregate. Don't try to remedy the problem by adding water alone. Instead, add a cement-water solution that has proportions of 2 to 1. Unfortunately, in most cases even this will not work and you will have to start from scratch with decreased amounts of sand and coarse aggregate. Experiment, keeping track, of the decreased proportions, until you have a satisfactory nix. You may have to try several small batches before you produce the right mixture.

Mortar mixes-
These can vary, of course, and there are lots of pet formulas floating around. Below is a good rule of thumb formula for Portland cement mortar and for masonry cement mortar. The formula makes just 1 cubic foot, of mix enough to lay 25 bricks.

• PORTLAND CEMENT: 16 pounds of Portland cement mixed with 8-1/2 pounds of hydrated lime mixed with 100 pounds of dry sand. Add enough water to make a fluid, smooth mixture-about 2 gallons, maybe three. Check as you mix.
• MASONRY CEMENT: 31 pounds of masonry cement mixed with 100 pounds of dry sand. Add from 2 to 3 gallons of water, but check as you go.

USING ALREADY MIXED:
If you have a large project such as a driveway or patio, we recommend concrete from an already mixed company. This company-or transit-mix concrete-has some definite advantages such as less cost and special ingredients such as air-entrainment.

There are several possible limitations, however, that must be considered before you order. The first is whether the truck can get to the forms. Most trucks have chutes that let the driver move the concrete as much as 20 ft. That is about the limit. If the truck cannot get close enough, you will have to move the material in wheelbarrows to the final location. If there is any doubt about your situation, and if you are dealing with a fair amount of material, it would be a smart idea to have the concrete dealer come out and look at the site.

Concrete trucks are extremely heavy. Fill areas around new house construction or even around older homes may be too soft to support the weight. The result is a stuck truck. A more serious result might be a tipped truck. Even in dry weather on normal ground, concrete trucks sometimes tear up a yard. Try to plan a route that will cause the least amount of damage to your property. If access is via your neighbor's property, better get permission for the truck to use this access before you order.

If you have to move concrete by hand, let the dealer know. Some companies charge for extra time. And, most important, have the job ready to go, i.e., the forms built and the finishing equipment handy. The driver will dump the load and go. You had better be ready to work the material. You won't have much time-usually an hour or less.

Ordering and scheduling-
Just give the dealer the dimensions of your project. He will figure out how much material is needed. You often can buy rein forcing bars and mesh from this dealer if you can't find it at your home center or building products store. If you can, specify that the load be brought to you early in the morning. This timing will give you time to work the job properly.

Almost always, the truck will bring a bit more mix than you need. Since the truck may have to be rinsed and dumped, you should have an area avail able in which to dump the excess. If just a little is left over, the material can be put in a wheelbarrow and kept until the pour is completed. After the forms are filled, you may need a shovelful l or two in places that looked full during the placement.

Soak the form and the subgrade with water the night before you start the job. Or moisten the subgrade just before the placement.

Make sure that you have properly prepared the site and that you have all tools on hand. It is smart to have a couple of helpers for a large pour.

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