Questions Regarding Concrete

We have compiled a list of questions that are frequently asked, in effort to provide you with an easy way to move forward with your project with piece of mind. However, as we are always updating and adding to our database, if you don't find the answer to a question you are looking for please feel free to email us at joe.rodgers@robinsonconcrete.com . This will also allow us to get the question and answer into our database here, to help others in the future.

Concrete.com....Another Great Site for answers to your questions........

Are there different kinds of Concrete?

Concrete has two basic categories; Interior and Exterior. Interior concrete is used where freezing will never occur and Exterior concrete is used in areas that may or will experience freezing. Exterior concrete contains an admixture known as air entrainment. This product, when added and mixed properly in the batch, will produce countless numbers of microscopic air pockets. These pockets allow space for the moisture drawn into the concrete to expand when moisture freezes. A glass bottle, when filled to the top, capped and placed in the freezer, will shatter. When a glass bottle is only filled partially and frozen, the shattering of the container will not occur. This is due to the fact that the liquid in the container has room to expand within the container as it froze. The air pockets within "air entrained" concrete will allow for expansion in a similar fashion.

Concrete can also be categorized as footing mix and slab mix. The differences inherent in these two is based upon the mix strength. This strength is a factor of the amount of cement placed in each cubic yard. a 2,500 psi mix is a basic footing mix. Higher strength mixes, 3000, 3500, 4000, 4500 and so on, have more cement in the mix design. In addition, footings are placed at a greater thickness ( approximately 10 to 12 inches) and do not require as much cement. Driveways and sidewalks are placed at a thickness of approximately 3 to 4 inches and more cement is needed to bring about strengths needed to support vehicles.

Is concrete a viable alternative in the Northeast with our hard winters?

Although our winters are tough on all surfaces, concrete is an excellent alternative to the traditional blacktop driveway. It also has the distinct benefit of far more flexibility in terms of colors or patterns. It does require some special care and treatment however which has a significant impact on the longevity of the surface life. We carry both Xypex and Sealtech products in an effort to make sure that we provide you with the total solution.

Can concrete be colored or dyed?

Actually, the coloring of concrete has become a very popular application in the northestern United States. It is actually becoming common also to "Stamp" the concrete into certain forms or designs such as stone or brick. If you visit the information Toolbox you will find links to a couple of different websites showing a number of different possibilities.

What is the Pitting of my Concrete caused by?

This "Scalling" or pitting as you refer to it is in many cases being caused by the desicion of the city, county and in some cases the state, to change the type of salt that they use to try and make our roads more passable in the winter months. Although they do the best they can in general, often there is not enough testing done on the various structures in the area before decisions are made. The properties of the current salt are such that as we warm a bit, they are able to eat into the surface of the concrete and create a very unappeling surface condition.

Are there different kinds of Concrete?

Concrete has two basic categories; Interior and Exterior. Interior concrete is used where freezing will never occur and Exterior concrete is used in areas that may or will experience freezing. Exterior concrete contains an admixture known as air entrainment. This product, when added and mixed properly in the batch, will produce countless numbers of microscopic air pockets. These pockets allow space for the moisture drawn into the concrete to expand when moisture freezes. A glass bottle, when filled to the top, capped and placed in the freezer, will shatter. When a glass bottle is only filled partially and frozen, the shattering of the container will not occur. This is due to the fact that the liquid in the container has room to expand within the container as it froze. The air pockets within "air entrained" concrete will allow for expansion in a similar fashion.

Concrete can also be categorized as footing mix and slab mix. The differences inherent in these two is based upon the mix strength. This strength is a factor of the amount of cement placed in each cubic yard. a 2,500 psi mix is a basic footing mix. Higher strength mixes, 3000, 3500, 4000, 4500 and so on, have more cement in the mix design. In addition, footings are placed at a greater thickness ( approximately 10 to 12 inches) and do not require as much cement. Driveways and sidewalks are placed at a thickness of approximately 3 to 4 inches and more cement is needed to bring about strengths needed to support vehicles.

What are concrete dyes?

 Although stains have received much applause for their amazing color transformations, dyes deserve equal kudos. These underrated coloring agents can achieve vibrant tones simply not possible with stains alone.  “Dyes can get the applicator into more vibrant colors such as yellow, blue, and purple to name a few,” says Bob Harris, president of The Decorative Concrete Institute and author of Bob Harris’ Guide to Stained Concrete Interior Floors. “The nice thing about working with dyes is that you can mix them at the jobsite to obtain your desired color. Dyes are often used in conjunction with acid stains to produce a variegated look and, in most cases, complement the already stained floor.”

What strength concrete do I need for my driveway?

We recommend a 4000 PSI strength for all exterior concrete.

Why does concrete crack?

The wet concrete will have a loss of volume as the concrete "sets" and continues to harden. This loss of volume occurs as shrinkage. That sets up tensile stresses causing cracks in concrete. Concrete cracking can be controlled but almost never eliminated.

How do I control cracking?

Concrete needs to be jointed to account for the shrinkage that will occur. Joint placement is determined by the thickness of the concrete.

How long should I stay off my new concrete?

A properly cured 4000 PSA mix should generate enough strength to drive on in seven days.