Now is a great time of year to upgrade your home with a concrete driveway. Think back to last winter...did you have ice between the stones on your gravel driveway that just wouldn't melt? Did your snow blower or shovel keep getting stuck on the heaving cracks of your asphalt or old concrete? Forward to spring...are you, like me, tired of raking gravel out of your yard from the snow removal from your gravel driveway? (Yes, we do concrete work and I still have a gravel driveway...such is life on a farm and I am okay with that!) You don't want to go through that again, do you?
But before you sign the contract or otherwise commit to a contractor to place the concrete, make sure you are going to get a quality and long lasting job. Here are some things to look for before you sign the dotted line:
1) Base - a compacted base is a must for a quality end product. We recommend a 4" gravel base compacted uniformly and evenly so the slab won't settle and won't vary in thickness.
2) The concrete should be 4000-4500 psi (determines the compressive strength, or also the amount of cement in the mix) and is air entrained. The slump should be a maximum of 4-5 inches for a non-reinforced slab. (This is a test that basically determines how wet or runny the concrete is.) The slump should be consistent with each pour that is placed throughout the project.
3) Reinforcement - You may have the option of fiber, wiremesh or rebar reinforcement. Fiber is usually used in concrete to reduce plastic shrinkage cracks or dry shrinkage cracks, the cracks that may occur during the initial curing process. The intent of wire or rebar is to hold the concrete together should cracking occur to reduce the heaving or shifting of concrete. Don't let any contractor tell you that their concrete won't crack. A contractor can do all they can to control the cracks, but they do occur beyond anyone's control. For more information on cracking, visit this website: http://www.concretenetwork.com/concrete/concrete_cracks/
4) Water should not be added to the concrete after it is placed to make the concrete more workable. Throwing water on top reduce the water to cement ratio on the top layer of concrete making it weaker. Beware of the contractor who does this! Some water or an admixture may be added before discharging from the concrete truck, but not after discharge begins. Admixtures can be added to the concrete while in the drum to make the concrete more workable.
5) A new slab should be allowed two months of curing time of temperatures above 40 degrees F. In our location, we do not recommend placing a driveway after October 1st.
6) Joints - Control or contraction joints on a 4" thick slab should be placed approximately every 10 feet and at a depth of at least 1/4" into the thickness. The joint gives potential cracking a place to "run" instead of randomly zigzagging across your driveway. If you find a crack in a control joint, that means it worked!
7) Curing - This is one of the most important steps in concrete construction. There are a variety of ways to cure concrete, but the most widely used method is a liquid membrane which is sprayed or rolled on the surface of the slab immediately after finishing.
8) In most cases you should be able to walk on your driveway the day after it is placed, but don't drive your vehicle on it for 7-10 days after placement. It actually won't reach its 4500 psi compression strength for up to 28 days in normal temperatures. Consult with your contractor on when he/she says it is okay to drive on your new driveway.
If you have questions, please leave me a comment and I will be glad to help guide you in your search for a durable driveway.
I pray that God blesses you in all you do, and that you have a wonderful weekend.