But at the same time it is relatively weak and brittle when formed into thin sections. So any movement at all in a large slab will create cracks like the ones you're seeing in your driveway. Concrete cracking can show up at any time, even on a one year old slab like yours.
As the concrete hardens, which is caused by the cement and water forming bonds, some of that water escapes through evaporation. This reduces the size of the concrete slab, and since concrete is a very hard, tightly bound substance, this loss of material creates stress. This stress can lead to cracks in the concrete.
As the shrinkage begins, the concrete will crack where it is the weakest. Cracking typically starts within 12 hours of the finishing process. Weather conditions will slow or accelerate it. Shrinkage cracking is typically planned for and handled with control joints.
Cracks after hardening
More often, they result from poor curing. Other cracks which occur after hardening can be caused by lack of adequate reinforcement at corners, insufficient depth of concrete over bends in reinforcement, nesting of reinforcing steel in concrete, lack of expansion and contraction joints.
As the slab loses moisture while curing it gets a bit smaller. As the concrete shrinks, the slab could crack in order to relieve tension. Shrinkage cracks are common and can occur as early as a few hours after the slab has been poured and finished. Usually they are not a threat to the structure.
Generally, cracks with a width of less than 0.3 mm are acceptable and do not affect the structure. However, they may develop and grow to become structural cracks. Therefore, one should monitor small cracks on houses or structures.
A concrete slab will shrink about ¼ inch for every 100 square feet of surface space. When concrete dries and shrinks, cracking can occur hours after being poured. Any crack that is ⅛ of an inch or smaller on your patio or driveway is considered standard. Some hairline cracks may form and disappear after a month or two.
In residential concrete, 4 inches is the minimum thickness for walkways and patios. Garage slabs and driveways should be 5 to 6 inches thick if any heavy truck traffic is anticipated, otherwise 4 inches is adequate.
Here's how to know if a crack is structural: One of the easiest 'tells' for structural damage cracks is that they grow over time. A thin, non-structural crack can quickly become a structural foundation crack if it gets wider after several weeks or months.
Actually, concrete cracks are very common, some are even inevitable. We explain 6 of the most common types of concrete cracks below.
The hardening, or curing, continues as long as moisture remains in the concrete. If too much water is lost from the concrete through evaporation, the hardening process slows down or ceases.
They usually appear soon after it's poured. These fine surface cracks are often cosmetic and not signs of serious structural damage. If the rest of the concrete is sound and the surface is primarily smooth, fix the crazing by applying a resurfacing product.
Technically, concrete never stops curing. In fact, concrete gets stronger and stronger as time goes on. But, as far as we're concerned, to reach a practical strength, most industrial concrete mixes have a 28 day curing period.
A well-made concrete structure should not develop structural cracks quickly. Nevertheless, hairline cracks can be expected. Don't stress; these cracks are not a sign of bad quality and can be fixed without much effort.
Foundation cracks are, for obvious reasons, one of the number one signs of foundation failure. However, not all foundation cracks are created the same, which means they won't all require the same repair method—some may not require repair at all.
Typically, larger cracks (those bigger than 15mm in width) are a cause for concern, as they could point to structural issues. You'll want to get these inspected by a structural engineer.
Hairline cracks can grow over time and weaken the structure, such as in a home foundation. Some hairline cracks can also cause leaks in a foundation. It's important to watch the cracks to see if they grow. Contact a concrete contractor if you notice cracks exceeding 0.3 millimeter wide.
Steel reinforcing bars and welded wire reinforcement will not prevent cracking. Reinforcement is basically dormant until the concrete cracks. After cracking, it becomes active and controls crack widths by restricting crack growth.
Can Sealing Prevent Cracks on Concrete Surfaces? Concrete sealing can stop most types of concrete fractures. This fact is especially true if the crack is a result of poor-quality work in the concrete mix or site preparation. However, sealing can prevent future damage that may start from the top layer of the concrete.
The fact that high-strength concrete is easily to crack has a significant negative impact on its durability and strength. This paper gives an optimum design method of high-strength concrete for improving crack resistance based on orthogonal test artificial neural networks (ANN) and genetic algorithm.
Can you pour concrete over cracked concrete? Pouring concrete over cracked concrete before at least repairing the cracks is not going to go well. If the issues that caused the cracking to occur on your existing concrete surface are still present, they will affect your new concrete surface, too.
Fixing Larger Concrete Cracks
You can either fill the crack with sand leaving ¼ inch to the surface of the crack to be filled with the grout or make multiple grout applications that are ¼ inch thick, allowing adequate time for each application to dry.
As per IS 456 and BS CP 114 concrete gains 120 % -124 % strength in one year.
For large scale projects like buildings, concrete should last up to 100 years if it's properly cared for. Concrete projects that experience more wear-and-tear like sidewalks and driveways have an expected lifespan of about half that—50 years.