Learn the Real Facts About Concrete and How Its Used for Foundations

Concrete is commonly misunderstood. We want to bring to light the falsities and replace such knowledge with the truth. From the difference between concrete and cement to whether concrete is impermeable. Learn the real facts, here.

Contention: “Concrete” and “cement” are two names for the same thing.

Correction: It’s true that these terms are used nashville concrete contractors interchangeably, but concrete and cement is not the same thing. Cement -or to be more accurate, Portland cement– is actually an ingredient in concrete. Although additives are sometimes used to alter different handling, curing or strength characteristics, the basic ingredients of concrete never change:

7%-15% Portland cement
8% or less Air
60%-75% Coarse & fine aggregates (gravel & sand)
14%-21% Water

If you want to be accurate, say “concrete mixer” instead of “cement mixer,” and “concrete sidewalk” instead of “cement sidewalk.”

Contention: Curing concrete means letting it dry.

Correction: The curing process for concrete, referred to as “hydration,” is more complex than simply allowing the liquid mix to dry into a solid. Hydration is a chemical reaction that bonds elements together. If concrete is allowed to dry out too quickly, bonding action diminishes, along with the strength of the concrete. That’s why contractors typically find ways to keep concrete damp as it cures, ensuring optimum hydration

Contention: Reinforced concrete won’t crack.

Correction: Different materials are used to reinforce concrete. Steel reinforcing bars (commonly known as “rebar”) are placed in forms for poured concrete footings and walls. Strong steel wire is bedded in the mortar between courses of concrete block. Poured concrete slabs are reinforced with welded wire mesh that looks like screen fencing material. And loose fiberglass fibers are sometimes mixed into poured concrete to increase its strength. But none of these reinforcing techniques will eliminate the chance of concrete cracking if it is subjected to a great deal of force.

Concrete has exceptional compressive strength but poor tensile strength. A concrete foundation wall can accept a substantial compressive load from the structure it supports, but the same wall can crack if soil pressure outside the foundation is pushing the wall inwards (tensile load). This is why a seemingly strong, solid foundation can crack and even shift in response to soil settlement or pressure.

Contention: Concrete is impermeable.

Correction: A bowl, basement or swimming pool made from concrete will hold water. But the concrete itself will also absorb water. As the soil outside a concrete foundation becomes more and more saturated with moisture, the foundation will also become saturated and transmit this moisture to the interior, even if no visible leaks are present.

Contention: A poured concrete foundation will always be stronger and more resistant to cracking than a concrete block foundation.

Correction: Assuming proper construction techniques are used to build both foundations, there should be little difference in strength and crack resistance between the two. Concrete blocks, after all, are made from poured concrete. And a block wall can be reinforced with steel and by filling hollow block cores with concrete. When concrete block walls crack because of soil pressure or movement, cracks typically occur along the mortar joints. Poured concrete walls, on the other hand, typically show diagonal cracks that extend from foundation corners when they fail due to soil pressure.