Cracks that are identified as small and fine (less than 0.3 mm in width), are generally deemed acceptable as part of minor settlement depending on the purpose and intent of the concrete structure, the environment it is placed in, the design-life and the durability design.
Generally, cracks with a width of less than 0.3 mm are acceptable and do not affect the structure.
Structural concrete cracks have the potential to negatively impact the durability and strength of a concrete structure. These cracks are general recognized as serious if they are progressively widening, retaining dirt, allowing penetration of moisture, or developing in highly visible locations.
These cracks are called hairline cracks (or shrinkage cracks). Hairline cracks are cracks in a nonstructural slab that: Remain about one-eighth-inch wide. Present no vertical displacement (one side of the crack is higher than the other)
Hairline cracking: Very thin but deep cracks. Due to settlement of the concrete while it is curing. Due to their depth, these cracks can allow for more serious cracking once the concrete is hardened.
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.
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.
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.
The federal regulations from the U.S. Department of Transportation — no crack larger than 3/4 inch in diameter, no two cracks within three inches of each other, no intersecting cracks, or cracks directly in the driver's view — are the minimum standards. Your state may have additional and possibly stricter requirements.
The higher the PSI the more durable your concrete will be and will thus be resilient to cracking. The average residential project uses a minimum of 2,500 to 3,000 PSI; however if you're concerned about cracking then we recommend talking to your concrete contractor about stronger products on the market.
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.
Sure sign of a structural deficiency are horizontal cracks, and cracks wider than a 1/4 inch. Structural foundation cracks are normally the result of movement, whether it's caused by temperature changes, soil pressure or soil shrinkage. In this case, epoxy is the material of choice for repairing the crack.
Characteristics of structural cracks
Over 1/10 inch wide – Structural cracks are usually wider than 1/10 inch (often wider at one end than the other) and grow larger over time. Horizonal foundation cracks in walls, with or without bowing – These are almost always structural.
To avoid water seepage and further damage, it's critical to seal any cracks that develop. This article will discuss why cracks happen and how to quickly repair them.
The 28-day curing time is a common requirement, but don't expect all cracking to be completed by 28 days. Drying shrinkage cracking can take place months after a concrete slab is placed.
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 ruler is simple instrument used to monitor crack width variation. The width of the crack can be measured to the nearest 0.5mm provided that great care is practiced.
Detecting Crack Depth
Accurate depth measurements require instruments that look for discontinuities in the concrete to indicate the extent of a crack. Ultrasonic pulse velocity is one such method and operates by detecting the travel time of stress waves of ultrasonic energy transmitted through concrete sections.
Changes in Temperature
When this happens, your windshield's structure tends to shift, thus weakening the corner of each crack or chip. In one day, these cracks will start spreading on a microscopic level. Within a few days, you will see marked differences in the crack with the naked eye.
A structural crack is where the foundation wall feels uneven or the width of the crack is about ¼” or wider. If you have a structural foundation crack, you may need an engineer's specifications to do a basement foundation repair.
A 1/16-inch crack is quite common when a home starts to settle. These hairline cracks should be vertical and should be between 2-6 inches in length.
Cracks found larger than five millimetres should be investigated further and an Engineer should be consulted. Cracking in a home or the type of crack found doesn't always mean there is a structural concern.
Cracks between 5mm and 15mm wide are more likely to be serious and may need professional repairs. Any crack bigger than 25mm wide should definitely be examined by a professional. If the crack is wider at the top than the bottom, and visible on both the outside and inside of your home, you might have subsidence.
The good news is not all foundation cracks affect your home's structural integrity. Sometimes they're just ugly and caused by shrinkage during the concrete curing process. These unsightly, non structural shrinkage cracks (which are often hairline cracks) don't put your home in immediate danger.
Horizontal cracks are much more dangerous than vertical cracks because they can quickly lead to total foundation failure. Even without total failure they will likely begin to cause serious damage to the walls of your home as multiple supports in one area will likely already be compromised.