Frequently Asked Concrete Questions

What’s the difference between cement and concrete?
Cement is an ingredient in concrete, much like flour is an ingredient in cake mix. Dry, powdered (portland) cement is blended with sand, stone and water to produce concrete. Kuhlman Corporation is a producer of ready-mixed concrete.

Why does concrete crack?
Concrete, like all construction materials, contracts and expands under various conditions of moisture and/or temperature. Cracks may be caused by movement of the subgrade, or the application of heavy loads. The lack of proper curing and control joints will contribute to random cracking.

How do you cure concrete?
Portland cement needs water to hydrate (harden). Curing is the name given to the procedures and products necessary to maintain and/or provide moisture for the cement to hydrate. Adequate curing provides additional strength and durability. Concrete cured for three days will have only 66% of the strength of concrete cured for 28 days. Chemical moisture barriers and mechanical methods can be effectively used for curing. Contact us at 419/897-6000 for assistance in selecting a suitable curing method for your application.

How big is a cubic yard?
A cubic yard of concrete measures three feet by three feet by three feet, or 27 cubic feet. It will weigh about 4000 pounds. It will cover an area of 81 square feet when placed four inches thick. Our concrete mixer trucks can deliver up to ten cubic yards per load.

What is air-entrained concrete?
When we want our concrete to be watertight and durable while being exposed to freezing and thawing, we add a small amount (5 to 7 percent) of microscopic air bubbles into the mixture. These bubbles provide expansion space for water that may saturate the concrete, freeze and expand. Air-entrained concrete should be specified for exposed (outside) concrete.

What is slump?
Slump is a measurement of the uniformity of concrete. The slump test is taken to measure the consistency between different truckloads of concrete. Most commercial concrete mixes are designed for a three- to five-inch slump. This is the measurement of the distance the concrete settles after being removed from a standard slump testing cone. Increasing the amount of water in a mix will increase the slump, however, there are chemical admixtures available to achieve the same results. Adding more water to a mix can be detrimental to concrete strength and durability.

When can I drive on my new driveway?
Always consult with your builder, but as a rule of thumb, in the summer, a new concrete driveway may be opened to cars (not trucks) after five to seven days with proper curing. Uncured concrete will require three weeks to achieve the same strength. In cool weather, wait an additional three to five days. We suggest concrete driveways not be constructed in the winter, unless EXTREME protective measures are taken to prevent damage. The best time of year in Northwest Ohio and Southeast Michigan to construct a driveway is after April 15th and until October 31st each year.

Call your knowledgable Kuhlman representative for help with any of your concrete questions.

Other Topics
For additional information on purchasing and working with concrete from Kuhlman Corporation, please see the other sections of this web site dealing with such topics as concrete basics, concrete placement and finishing techniques, and concrete curing/sealing.