Reduce The Cost Of Concrete In Slump & Watercement Ratio

The right amout of water can reduce your concrete cost.

Adding water to concrete can increase its workability and reduce the amount of concrete that you use in a pour, but you have to be very careful when doing so. Add too much water and you can exceed the slump allowance specified by the engineer and building inspector and will have to order new concrete. By knowing how far you can go with your slump and learning measure the slump yourself you can change the water-to-cement ratio and reduce your costs.

Instructions

1. Find the concrete specifications for your job and for the specific type of structure you will be pouring (slab, wall, column). The specifications will include the slump allowances for the area. If they are not in the general notes of your building plans contact the building inspector and engineer of record to get the specifications.

2. Add water to your ready mix concrete. If your concrete is being delivered in a truck, use a spray hose to introduce the water into the mixing tank. If you have hand mixed the concrete, use a small container to add water to it. Add the water in increments of a 1/2 gallon per cubic yard of concrete that is in the concrete mixer (or wheelbarrow). Less than that will not effect the slump enough to measure and adding more than that means you run the risk of having added too much (which means adding more concrete to return the slump to an acceptable level).

3. Mix the concrete and added water, no water should remain pooled on the surface of the concrete (either in your wheelbarrow or when you release some concrete from the truck into the pour chute to test the slump).

4. Use a hand trowel to fill a slump test cone with concrete. Use the flat end of the trowel to level the concrete in the cone so the concrete is even with the top of the cone edge.

5. Lift the cone up by grabbing the top rim of the cone and holding it off the ground for a minute. You will see the top of the concrete settle in the center. Measure the depth that it settled to determine the slump (slump cones are marked in millimeters so it is easy to measure the depth). Compare the slump you measured with the slump you are allowed in your pour to determine whether you can add more water to your concrete.

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