Concrete Frequently Asked Questions

Q: Cement and Concrete- Aren't they the exact same thing?

A: Definitely not. Though these two words are sometimes used referring to the same thing (i.e. cement pavement), they are not the same thing. Concrete is an end product made up of paste and aggregates, and one of the components of the paste is Portland cement.

Q: How strong is concrete?

A: Concrete is one of the most durable and versatile materials we know of. Through a process called "hydration", concrete transforms from a malleable plastic substance into a hardened tough material. The concrete continues to harden for years after it is set in place, making it even stronger over time.

Q: How do I cure concrete?

A: To greatly impact both the longevity and strength of concrete that one should "cure" the concrete. Curing is a very important step in the concrete process. As we mentioned earlier, concrete hardens as a result of hydration when the water and chemicals in concrete are able to interact and essentially fuse together. However, if water is not available to the concrete, hydration cannot occur. This is where curing comes into action. The process involves keeping the concrete moist over about a week period to allow the hydration process to occur.

Here are some curing methods that are popular to keep the concrete moist

  • Concrete soaking hoses
  • Sprinklers
  • Wet burlap sacks placed over the concrete
  • Curing compounds that seal in the moisture.

Remember temperature plays a significant role in this process as well. If it's too hot the moisture will evaporate and conversely if it's too cold the process may not happen at all.

A good rule of thumb to follow is to cure in temperatures above 52 degrees Fahrenheit.

Q: What are Concrete mix proportions?

A: Concrete mix proportions are the amount of cement, water, air, and aggregates are used to create a final concrete product. Generally, to create strong quality concrete result, the "rule of six" is a strong method to follow. This rule states to use six bags or cement for every cubic yard of concrete needed, six gallons of water per bag of Portland cement, a six day curing period, and an air content of six percent.

Q: Why is my concrete cracking?

A: Concrete, like any material, is directly affected by temperature and changes in volume. In the beginning stages, concrete will shrink in volume slightly as it dries causing cracks to occur. Later sharp changes in temperature can cause the cracks to start or existing cracks to become larger.

A way to cope with this draw back is to follow the methods of concrete contractors and put joints in the concrete pavement. This won't stop the cracking but it will allow the cracks to occur in neat straight lines at the joint when concrete begins to shrink.

Q: How do I know that the concrete I paid for is the concrete I'm receiving?

A: After figuring out exactly what type of concrete you need, it is easy to trust that your dealer will supply what you want. Unfortunately it is not entirely uncommon for someone to pay for one type of concrete and receive a cheaper version of it in the finished project. To avoid this unethical and potentially dangerous problem, you should always perform a concrete test to confirm the type of concrete being used. There are many tests that apply to different types of concrete. Here are a few:

  • Slump Test- Slump is simply the consistency of the concrete. The relative ability of the concrete to flow when being put in place is very important and problems can arise if the slump level is too low, such as proper consolidation of the concrete. Likewise if the slump is too high, meaning there is too much flow in the concrete there can be several issues including finishing delays and segregation.
  • Air Content Test- This test is executed by taking some fresh concrete and measuring the total air content contained within it. This test, however, is not entirely accurate because some air will eventually be lost in transportation, consolidation, etc.
  • Unit Weight Test- Weight of a known volume of fresh concrete is a fairly good indication of the makeup contained within it.
  • Compressive Strength Test- Measuring the force needed to break poured cylinders of concrete. This test is performed as the concrete goes through its hardening process and is executed at pre set intervals.

Q: What is "three thousand pound" concrete?

A: Three thousand pound or 300 pound concrete has stress strength of 3000 psi. This has to be maintained over a 28 day period. It isn't the only strength out there but is very common for most concrete to have less than a 7000 psi.

Here are a few brief tips about ordering concrete in case the above didn't help:

  • Always carefully measure length, width, and depth of the area that you need to fill.
     
  • You can expect to pay about $100 or less per yard of concrete, so budget yourself accordingly and play it conservatively. A lot of times there are hidden costs we don't think of.
     
  •  Make sure there is a clear path to your job site and that there will be no delays after the truck arrives. You don't want to have the concrete driver wait around because the concrete is best used when it is as fresh as possible. Also, if you don't use one of our concrete plants they may charge you for the extra time.

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