You’ve decided. You’re choosing concrete over asphalt for your driveway or parking lot project. But did you know that not all concrete mixes are created equal? The type of concrete mix you need will largely depend on the type of project you’re working on.
Driveways need stronger concrete whereas decorative projects require more flexibility. So, how do you choose the best concrete mix for your project? Well, your first option is to consult with a concrete contractor early on in your project and work together to find the solution. But if you’d like to know a little more about the process, here are some tips on choosing the best concrete mix for your project.
Want to learn more about the basics of concrete before you keep reading? Just visit this page.
To understand the variations of concrete mixes, you need to understand what goes into concrete. There are four main materials in concrete:
- Aggregate (crushed stone/rock).
- Water .
The ratio of sand to cement plays the biggest role in determining the strength of the mixture. As a standard guide, a concrete mix is made of:
- Four parts aggregate.
- Two parts sand.
- One part cement.
But this ratio is not ideal for every situation.
What Makes Concrete So Durable?
Concrete is made of a mixture of aggregates, portland cement and water. Concrete may also include supplementary cementitious materials, chemical admixtures and/or fiber reinforcement. The key to achieving a durable, strong concrete is the careful proportioning and mixing of these ingredients. A well graded mix of large, medium and fine aggregates allows the cement to bind the mix more tightly increasing durability & making it more impervious to water, salt and other external forces.
Alternatively, a concrete mix with high portland cement and sand will be easy to mold and produces a very smooth surface, making it ideal for countertops or other interior decorative uses that won't be exposed to temperature extremes or heavy vehicle traffic.
A properly designed mixture is both workable for forming and has the required durability and strength when it hardens and cures. A typical mix is about 10 to 15 percent cement, 60 to 75 percent aggregate, and 15 to 20 percent water. Exterior concrete mixtures also contain air content of 5 to 8 percent which gives the concrete freeze-thaw durability.
Another critical maintenance step is to avoid deicers than contain calcium chloride or magnesium chloride. Also, never use deicers that contain ammonium sulfate or ammonium nitrate. These products will cause concrete to deteriorate faster than normal. The only recommended deicer to use is plain rock salt, which is sodium chloride.
What To Consider When Choosing the Best Concrete Mix
Before you get started, there are a number of factors to consider when determining your concrete mix.
Strength: The type of project will determine how strong your concrete mix needs to be. Higher traffic areas call for concrete with higher PSI (pounds per square inch). Concrete for driveways or highly trafficked sidewalks should have anywhere from 2,500 PSI to 10,000 PSI. 2,500 PSI generally works for home driveways, walkways, and floors. Despite what the area can handle, a contractor might choose a higher PSI in order to guarantee the durability of the project.
Temperature: Before choosing a mix, consider what kind of climate the area will endure throughout its lifetime. High temperatures or extreme variations might call for an entrained air mixture, a mixture that holds tiny air bubbles that allow it to expand and shrink in a changing climate.
Surface Area: If you’re working with tight spaces, you might want to choose a mix with a plasticizer. This makes the mix more fluid and helps it fit into hard-to-reach areas.
Best Mix for Concrete Driveway
For a driveway where you may need more strength you could use:
- Three parts aggregate.
- Three parts sand.
- One part cement.
This creates a mixture that would withstand about 3000 PSI. For a project that needs to withstand more weight, you would use more aggregate. For more decorative projects that require more flexibility, you would want more aggregate and less sand.
Best Mix for Concrete Counters
Countertops and projects inside the home will have different aesthetic requirements. For countertops, you need a mix with high early (compressive) strength. This is important when you need to get the concrete out of the forms and start grinding it as soon as possible. This type of strength is achieved by using a low water to cement ratio.
Talk to your contractor about how to achieve low shrinkage potential by adding shrink-reducing admixtures to any mix used on countertops or similar projects. This helps reduce the root cause of cracking and curling.
Overall, you want to make sure you have the right concrete for the job which means having the right contractor on the job. If you’re not a concrete expert, call your concrete contractor early on in your project to make sure you get the right mix.
Get connected to the right contractor for the job. Reach out to Michigan Concrete to get started.