As a general rule, if the cracks are less than a quarter of an inch wide, you can be content with simply repairing the surface. You can then opt to reseal or repaint the entire area to ensure that it has a uniform appearance. For cracks larger than 6.5mm, however, the repair is only a temporary solution. To fix these, you should pour enough dry concrete mix into a 5-gallon bucket to fill in the cracks and patch any damaged areas.
Sand mix or concrete resurfacing, which does not contain gravel, can be used if the area to be repaired is not large or deep. A standard concrete mix containing gravel works best for patching large or deep areas. Hairline surface cracks, sometimes referred to as “crazing”, are an indication that the surface of the concrete dried too quickly when it was poured. Although they may be unsightly, these cracks in a concrete roadway do not indicate underlying structural problems.
As long as the rest of your driveway is in good condition (no lifting, sinking or crumbling), you can replace these small cracks with a smooth concrete surface by applying a high-quality resurfacing product, such as Quikrete's Concrete Resurfacer. This cement-based product contains polymer modifiers and additives that are designed to form a durable and permanent bond with the existing concrete. Epoxy-based materials are available, but are probably best left for smaller jobs. Mixing epoxy and getting it to penetrate 50 feet of narrow width cracks could be an exercise in futility.
For one or two short sections of cracks, epoxy provides a good long-term solution, although the appearance may not be the best. Start by using a pressure washer to remove any mould and dirt. After wetting the slab, a special masonry cleaning solution is added to the pressure washer tank and sprayed on the surface. Once the cleaner has been applied, a high-pressure nozzle is connected to the washer and the surface is thoroughly cleaned.
Be sure to clean the cracks as well, removing dirt or loose concrete so that the patching material will adhere to the concrete. Cracks in concrete can be caused by tree roots and soil movement, as well as freeze-thaw cycles in winter and expansion during summer months. Like spider web cracks, these small cracks do not indicate a major problem, and usually appear shortly after the concrete is poured. When the concrete begins to set, a broom with an extended handle can be used to give the surface some texture. As long as your driveway is structurally sound, there are ways to repair minor and even major defects without having to tear it out and replace it completely.
An old roadway does not have the colour of new concrete; it would take some real trial and error work with pigments to match it after the patch has completely dried and set. Generally limited to a small area, these cracks are good candidates for repair with Quikrete Rapid Setting Cement mixed with Acrylic Fortifier. Instead of going through the expense of removing the slab and pouring a new one, you may be able to repair and resurface the existing concrete. Cracks of this nature can never get any bigger, but water can seep into them, freeze and expand, causing them to widen; so it's wise to seal them with Quikrete's Advanced Polymer Flexible Crack Sealant. In this project, the concrete driveway was stained a warm shade of walnut to accentuate existing cracks and give it a rich leather look.
Sealing can prevent major problems in the future; and Advanced Polymer Concrete Crack Sealant's no-sag consistency and matte grey colour will even out the surface while its texture blends in with your existing driveway - disguising any evidence that there was once a crack. Many of the serious concerns about concrete's sorry state can be traced back to its brittleness. When large slabs are poured, contractors will shutter or cut joints every two to three metres in order to limit shrinkage cracks caused during curing or by future movement of the slab. Shrinkage cracks caused by air pockets in concrete can occur within hours of pouring it; inadequate subfloor preparation, poor concrete mix or shrinkage during curing are all factors that can cause cracks and result from improper initial installation of a roadway. Very small cracks are difficult to fill with this material as it must be pushed into them with a trowel or other fine tool; but if done correctly it makes for a lasting repair. If damage is extensive you may want to call in a professional; but if limited to one small section you may be able to replace it yourself.