The phenomenon of cracking when laid, concrete normally contains more water than is required for cement hydration. As concrete hardens and begins to lose excess water, shrinkage begins. If the concrete is not restricted, no cracks will develop. It's natural to worry about cracks in freshly poured concrete, but the truth is that some cracks are inevitable due to the structure of the surface.
Very fine surface cracks, sometimes called “cracking”, are an indication that the concrete surface dried up too quickly when it was poured. While unsightly, these cracks in a concrete driveway do not indicate underlying structural problems. As long as the rest of your driveway is in good shape (no shaking, sinking, or crumbling), you can replace those small cracks with a smooth concrete surface by applying a high-quality resurfacing product, such as Quikrete Concrete Rejuvenator. This cement-based product contains polymer modifiers and additives that are designed to form a durable and permanent bond with existing concrete.
While the application of Concrete Rejuvenator does not require the help of a professional, it does require attention to detail. Existing concrete must first be thoroughly cleaned with a high-power pressure washer. Depending on the size of the driveway, you'll want to apply the respaver with a long-handled squeegee to the small, workable sections, one at a time. This helps ensure that you can apply the product, soften it and add a brushing effect to the surface before it dries.
Small cracks here and there that are narrower than ¼ inch are probably the result of shrinkage as the entrance healed. Like the cracks of the spider web, these small cracks do not indicate a major problem and often appear shortly after pouring concrete mix. Cracks of this nature may never get bigger, but water can seep, freeze and expand, causing cracks to widen, so it's a good idea to seal them with Quikrete's flexible advanced polymer concrete crack sealer. Sealing can avoid major problems on the line, and the no-sag consistency and matte gray color of the advanced polymer concrete crack sealant will even out the surface and have a texture to blend into the existing inlet, hiding the fact that there was once a crack.
Flexibility is key to a good sealant because concrete expands and shrinks slightly with temperature changes. Before applying the sealant, you'll need to do some prep work, which includes widening the crack with a hammer and chisel in places where it is less than ¼ inch wide and brushing off any crumbling debris. After that, filling small cracks is an easy DIY project, but for best results, watch this concrete crack repair video before you start. When pouring large concrete slabs, the contractor forms or cuts joints every eight to 10 feet, in order to limit any shrinkage cracks caused during the curing process or by future slab movement.
In this way, cracks are hidden deep inside the joints, so that the smooth surface of the driveway is maintained. Therefore, if you notice cracks along a control joint, do not worry; it is only the joint that serves its purpose. What you should watch for are cracks that are wider than an inch and are uneven; this could indicate an underlying structural problem. While this type of problem is more common with older entries than newer ones, it is an indication that the entry or at least the section with the cracks should be replaced.
Although concrete is a very strong building material, it has its limits; placing excessive amounts of weight on a concrete slab can cause cracks. When you hear that a concrete mix has a strength of 2000, 3000, 4000 or more than 5000 PSI; you mean the pounds per square inch it would take to crush that concrete slab. Concrete driveways can crack for many reasons; repeated freezing and thawing, heavy loads, tree roots and even soil changes can cause damage. When you learn how to repair cracks in a concrete driveway; you may be able to stop them before they cause major problems.
Fortunately; filling cracks in a concrete driveway is a simple and relatively inexpensive DIY project. Wait until the forecast indicates dry weather and the concrete surface is at least 50 degrees F; if you see cracks or curls; it is possible that the concrete will dry out faster than it should during pouring. On sunny or windy days; where the top of the slab dries faster than the bottom; the top of the concrete surface may become crisp. The American Concrete Institute addresses this issue in its manual from The American Concrete Institute (ACI 302).
Consult an engineer or concrete repair professional to determine what caused your crack and recommend what repair solution would be best for your situation. The bottom line is that a low ratio of water to cement is key for quality concrete; excess water reduces this ratio. Concrete repair contractors will provide crack sealing as part of their service package which includes sealing. Consider hiring some additional workers because once you start pouring concrete; you will have to continue until your entire slab is poured.
When properly installed; concrete is one of most durable products you can use in your home.