Working with concrete is simple enough that many homeowners opt to undertake basic paving tasks themselves. Yet unless you're a professional paving contractor, chances are there are a few essential tricks you don't know. If you would like to learn more to keep cracks from forming in hardening concrete, read on. This article will address two of the causes of so-called pre-setting cracks--and teach you how to prevent them.
Plastic Shrinkage Cracks
Plastic shrinkage cracks are commonly encountered when pouring concrete in outdoor settings, especially when the conditions are windy and/or hot. These two factors will lead to uneven drying of your concrete. Specifically, the surface will dry at a much faster rate than the concrete deeper down, thus causing networks of fine, spidery cracks to appear. Though not a structural concern, such cracks often result in an undesirable appearance.
The best way to avoid plastic shrinkage cracks is to take the expected weather conditions into consideration when planning your construction project. If the weather is going to be hot, make a point to pour the concrete in the evening, when the effects of sun and heat will be somewhat diminished. If this isn't an option, look into erecting wind breaks and/or sun shields to help mitigate their negative effects as your concrete dries.
Form Movement Cracks
The shape that your concrete will ultimately take once hardened is designated by the boundaries set by your forms. Forms are most commonly created using wooden boards that are braced along the outside of the wall with stakes. A common mistake when constructing forms is to underestimate the pressure exerted by wet concrete. Unless your forms are securely fitted in place, the great weight of the concrete will force them outward, thus leading to cracks as the drying concrete alters its position.
Regardless of the particular structure you are building, it is vital that you erect the strongest possible forms. The boards that you use must be a minimum of one and a half inches thick. Anything less and you risk warping, bowing, or even breaking. To reduce this risk even further, utilize heavy duty stakes. These must be placed evenly along the entire length of the form.
If constructing a concrete surface that will sit below ground level, the stakes don't have to be quite as close together--one every three feet ought to suffice. When working with above ground forms, these stakes will need to be much closer together--about 16 inches apart. In this manner you can help prevent cracks due to shifting forms.Share