Desiccant dehumidification (March, p. 86) looks like a very nice solution that will allow tile to be placed on concrete sooner. I would also like to mention another solution that will save even more time and will also save money.

The main reason for the long wait before placing tile or a coating is that most portland cement concrete is placed at about a 0.50 water/cement ratio (w/c), but the portland cement requires only a 0.25 w/c for full hydration. That excess can easily amount to over 2000 pounds of water per 1000 square feet of concrete. That is a great deal of water that has to come out of the slab.

On the other hand, Type K shrinkage-compensating cement, which has been used in the United States for over 40 years, requires a 0.45 w/c for full hydration. This means that there is little excess water, so the slab will naturally dry out much more quickly. Testing has shown that the concrete is ready for a surface treatment in one-third to one-half the time.

There are many additional benefits to the floor slab contractor that make the slab actually cost less than a conventional slab. For most slabs, the steel reinforcement can be eliminated since it is really only there for shrinkage and crack control. With no rebar in the way, pumping may not be necessary. Productivity also is up with no rebar in the way. No need to worry about saw-cutting the slab because joint spacing can be extended up to 150 feet. This also means no need to worry about saw-cut timing or filling control joints. No dowel baskets to bother with. Punch lists become much shorter without repairing cracks, patching spalls, and grinding curl. This solution saves both time and money.

— Kyle de Bruyn, Product Development Engineer CTS Cement Manufacturing Corp. Cypress, Calif.