Concrete is an extremely durable and strong material, popular because it has so many practical uses in homes and commercial buildings. However, when concrete experiences too much tension or movement, it can crack—making your concrete surfaces unsightly and weakening their performance.
If you’re noticing fractures in your concrete, you’re likely wondering how serious the problem is and whether it needs repair or not. Below is an overview of why concrete cracks, and how to recognize when it needs to be fixed.
Different Types of Cracks and What Causes Them
There are several causes of concrete breakage—resulting in different types of cracks. Here are the most common issues you may experience, and why they’re happening.
After the concrete is poured, the heavier particles sink to the bottom and the lighter ones rise to the top, along with water. If the water at the top evaporates too fast, it shrinks, causing cracks that weaken the overall surface.
This happens when rebar, welded wire mesh, post-tensioning tendons, and other support elements are not positioned far enough away from the surface of the newly poured concrete. If they are too close to the top, the cement pulls apart, impairing your concrete’s performance.
Decomposing tree roots and other issues can create vacant spaces in the soil around your foundation, leading to settling that can crack concrete slabs. Minor settling may not be a concern, but it should be evaluated by pros to be sure your home is structurally sound.
When snow and ice cover driveways and sidewalks, homeowners may use salt to melt the precipitation. Unfortunately, salt is concrete’s kryptonite, causing pits to form in the surface. Over time, the cracks are likely to grow, making walkways unsafe to navigate.
Rusting steel rebar, iron rails or wire mesh can eat away at the concrete around it. Small cracks develop, allowing water to seep into the slab surface. Over time, those small cracks turn into larger ones.
Some cracks happen when too much weight overloads the concrete underneath it. Knowing the limit, or the PSI (pounds per square inch) of the surface is important to make sure you don’t put anything too heavy on top of it. The typical concrete strength of a home driveway is 3000-4000 PSI, which works for cars and lightweight pickup trucks. But large, industrial trucks can cause serious damage.
Concrete expands as it gets hotter. When it does, it pushes against anything in its path—whether that’s a tree, a brick wall, or your house’s four walls. Too much expansion, and the concrete may crack, leading to significant damage to both the slab and your home.
Frost heaving is a big concern in Oklahoma. When temperatures drop below freezing, moisture in the ground expands, causing anything above it (including concrete) to rise several inches before the soil thaws and everything settles back down. As this freeze-thaw process repeats itself, it contributes to concrete cracking, which can damage your foundation slab.
When fresh concrete doesn’t dry properly, two types of damage can occur: crazing and crusting.
Crazing cracks are very thin, surface fractures that look like shattered glass or spider webs. When a newly poured concrete slab loses moisture too quickly at the top, crazing can appear.
Crusting cracks normally occur while stamping and adding texture to concrete surfaces. If the stamp isn’t embedded with care, the surface pulls apart slightly, which leaves small cracks around the outside edges.
While crazing and crusting may impact the concrete’s appearance, they don’t mean your concrete is weak and in need of repair.
What Can Be Done about Cracked Concrete?
When doing a fresh installation, experienced concrete contractors will do their best to control or prevent cracks from forming by using appropriate techniques to minimize issues during the pour.
Choose a company that provides reliable, highly recommended residential concrete services and that lays slabs properly the first time. Ask if they plan to use any or all of these materials:
Control joints, also called contraction joints, allow the concrete to experience movement without unsightly damage. With control joints, if the concrete cracks, it does so in a straight line and below the surface. This keeps the top of the surface smooth.
Expansion joints can help to prevent cracks in foundations. Expansion joints penetrate the full depth of the slab because they are designed to allow movement, and then are sometimes filled with a flexible material.
Concrete doesn’t exactly move or expand the way a wall, pipe or column does, so isolation joints are placed where concrete meets other surfaces. This allows for vertical and horizontal movement in these isolated spots, bearing the load without cracking.
Reinforcements, such as steel reinforcing bars and welded wire, help maintain a concrete slab’s strength and give it support for when cracks occur. Reinforcements can keep any cracks that develop tighter and can often prevent them from spreading.
Get Sound Advice on Your Concrete—and Peace of Mind
Still have questions or concerns about cracked concrete? Wondering if it’s time for repairs or replacement? We’ve got answers to put your mind at ease.
The best way to determine how serious your concrete damage is and what to do about it is to get an inspection, including an estimate for any needed repairs. Reach out to us to request a free consultation. Our team, at R&M Concrete, will examine your property and explain to you what you’re seeing and why it’s happening—so you can make good decisions about whether to make cosmetic fixes, install supports, or replace your surface with fresh concrete.