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Richfield Concrete Minneapolis St Paul MN

What Is Concrete?

Concrete is a mixture of gray powder called “Portland Cement”, sand and gravel or crushed stone. The “Portland Cement” reacts chemically with water and hardens over time – a process called “hydration,” Concrete doesn’t “dry;” it “cures.” Additives are generally included in the mixture to improve its suitability for driveways. The most common are water-reducers that improve strength, and air-entraining mixtures that make the concrete resistant to cycles of freezing and thawing. Air-entrained concrete additives, containing billions of microscopic air bubbles, and reduce expansion and contraction. This helps concrete withstand Minnesota’s large temperature range over our four seasons.

How Strong Is Concrete?

The compression strength (resistance to downward force) of concrete is determined by a number of factors. The most important is the ratio of water to cement in the mixture – the lower the ratio the stronger the concrete. Another way to increase the strength of concrete is to increase the amount of cement used. The strength of concrete is measured in pounds per square inch (PSI) Concrete used in driveways is generally 3,000 – 4,000 PSI, this strength is the result of using 5 bags of cement per cubic yard in the mix. At Richfield Concrete, we use 4,500 PSI for our paving projects.

If Concrete Is So Strong, Why Does It Crack?

There are two kinds of concrete: the kind that is cracked and the kind that is going to crack. If a driveway contractor tells you his concrete driveways won’t crack, be skeptical, because it’s just not true. Although concrete has very high compression strength, it has very little tensile strength (resistance to being pulled apart). Because concrete shrinks as it cures, at a rate of about 1/16th of an inch for every 10 feet, there is strong tension pulling the cement slab. Because the whole slab can’t move over the ground, it can pull apart in the middle, causing a crack. Proper steel grid and micro-fiber reinforcement can help reduce this cracking tendency. The age of concrete has no bearing on when it will crack.

Reinforcement Gives Concrete More Tensile Strength

As mentioned, concrete, by itself, has low tensile strength, a major factor in cracking. Steel, on the other hand, has very high tensile strength and expands and contracts at rates very similar to concrete. When steel rods are set into the slab in a grid pattern they greatly improve the overall strength of the concrete and reduce its potential to crack. Microfibers are millions of small fiberglass strands that are interwoven to help hold concrete together and resist cracking. At Richfield Concrete, we use both steel and micro-fiber reinforcement to further strengthen the concrete, unlike some companies, which may use one or the other.

Control Joints Help Control Cracking

Control joints, as they are called, weaken the concrete slightly at the surface, so that when the concrete cracks it will likely follow the control joint and not be noticed. These control joints can be created in two ways. The concrete can be cut in straight lines, roughly ¼ of the depth of the slab. Hand-troweled control joints are another option, also often seen on sidewalks. The number and spacing of these control joints depends on the specific installation.

What Other Factors Cause Cracks?

In addition to shrinkage, there are four other main causes that contribute to cracking:

  • Expansion and contraction due to temperature changes
  • Concentrated heavy loads
  • Poor un-compacted sub-base conditions
  • Rapid water loss prior to finishing the concrete after it is poured.

All of these causes can be minimized with proper care and installation. A properly compacted sub-base of the proper thickness under the concrete is crucial. In Minnesota’s cold winter climate, only air-entrained concrete should be used. Heavy vehicles, such as garbage trucks should be kept off the slab, especially near the edges. Finally, an experienced concrete paving company will properly manage the curing process after the concrete is poured.

Your Choice of A Paving Contractor Is Important

To make sure your new concrete driveway gets off to a great start, you need to make sure the contractor who builds it has the experience needed to take all the factors above into consideration and the integrity to follow the best practices in building your driveway. Shortcuts and cutting corners during in construction will only lead to problems. Choose your contractor wisely for the best results.

Richfield Concrete – Experience, Expertise, and Integrity in Concrete Paving

At Richfield Concrete, our long experience in concrete driveway construction, combined with our strong commitment to quality construction is your assurance of a long-lived, beautiful driveway. Our thousands of customers over the 60+ years we’ve been building driveways regularly recommend us to their friends and neighbors in Minneapolis St. Paul Metro Area. If we built poor driveways, we wouldn’t have the outstanding Better Business Bureau rating we’re so proud of. If you’re thinking about replacing your driveway, call us soon, or contact us online. Let one of our experienced driveway consultants explain all of your options and provide you with a free, no-obligation estimate. We’ll show you how our paving company builds top-quality concrete driveways at competitive prices.