As the name suggests, shrinkage cracks are cracks that forms as the concrete shrinks or cures. Concrete cracks present themselves in varied patterns. Some are uniform in width while some are v-shaped with the top wider than the bottom. Some are vertically, diagonally or horizontally straight while others are wandering, irregular and random. In any case, you will be able to identify shrinkage cracks because of the fact that they taper or diminish before they reach the concrete on the load bearing elements of the house like beams, floors or room corners where the concrete is held more strongly in place by steel reinforcements.
Shrinkage Crack Risks
Shrinkage cracks are mostly only cosmetic and not structural in nature. This means that aside from being displeasing to look at; they usually pose no great threat to the integrity of the house. Cracks that propagate through load bearing members like the floor, beams or foundation however should be checked by a specialist as these may not be symptoms of shrinkage cracks but rather signs of foundation settlement, loading or movement.
Shrinkage cracks, when located on basement walls, foundations, crawlspace or basement slabs however add an additional cause for concern into the mix as they may allow entry of water or radon into these areas and may threaten the health of your family or structurally damage the foundations.
Cause of Shrinkage Cracks
It is only natural for concrete to develop internal stresses as it dries. Shrinkage cracks that develop from these internal stresses however could be substantially reduced if one follows the recommended way of curing concrete including the installation of control joints which helps relieve the internal pressures that build up. Concrete curing is a chemical reaction, not just “drying” or loss of water. But depending on the concrete mix, amount of water, portland, aggregate type, temperatures, humidity, groundwater, sun exposure, and other conditions, the amount of shrinkage that will occur in concrete as it cures will vary.
As such, to avoid shrinkage cracks, take note of the following advice:
1. Right mix of concrete: different elements of the house will require different concrete mixes. If the mix for the basement wall, slab or foundation was incorrect, then you can expect shrinkage cracks to occur.
2. Control Joints: Control joints provide a way for the internal stresses of the concrete to be released. With these, cracks are at most limited to control joints only. Control joints however must be properly placed and distanced to be effective.
3. Improper Curing: Concrete needs a certain amount of days and certain conditions in order to reach its full structural strength. This includes the amount of moisture present, the surrounding temperature, the number of days before the concrete supports are removed, etc.
Shrinkage Cracks Solution
Most of the solutions to prevent shrinkage cracks are done before and during the curing of the cement mix. Existing shrinkage cracks are oftentimes repairable by simple plastering but for those shrinkage cracks that allow water entry into the home, waterproofing techniques may be used to solve the problem. You can read more about waterproofing in this article.
In all the above cases, it is best to seek for professional opinion in order to make sure that the cracks are not caused by other factors like earth loading or foundation movement that may severely compromise the structural integrity of your home. Sinai Construction offers free consultation services that can help you diagnose and identify solutions for concrete cracks in your home.