Concrete sawing, used to ensure that recently poured concrete cures properly, is an essential part of the installation process. Yet even those who work in the construction industry often fail to understand the reasons and methods behind concrete sawing. Whether you work in the field or are simply an amateur with an upcoming concrete project, read on. This article will provide a valuable overview of the concrete sawing process.
What Sawing Accomplishes
Sawing--performed using a circular saw, preferably one equipped with a diamond-tipped blade--is used to create joints in large concrete slabs. These joints are vital in preventing the formation of random cracks caused by drying shrinkage. You see, a certain portion of the water in concrete evaporates as it dries. When the stress caused by this shrinkage is greater than the concrete's tensile strength, unwanted cracks form.
Concrete sawing limits the formation of such cracks to the sawed joint. While such joints can also be created by hand, sawing represents a much more versatile and consistent means of getting the job done. For one thing, the window of time for joint creation is much greater. It is also much easier to ensure consistent joint depth and width, as well as to create clean, straight cuts.
Timing Is Key
Although fairly permissive, concrete sawing must take place within a certain timing window in order to yield the desired results. Cutting too soon--that is, before the concrete has hardened enough--can lead to the problem known as joint raveling. This essentially means that the edges of the cut will tend to crumble away, leaving a ragged, damaged appearance.
Cutting too late can be just as problematic. Should the concrete have solidified too much, the sawing process can lead to uncontrollable cracking in the adjacent portions. Unfortunately, there is no magic number for when concrete sawing should occur. Rather it depends on an array of factors including:
- weather conditions
- composition and hardness of the particular concrete mix
- size and type of sawing blade
- curing method employed
Generally speaking, concrete has sawing window of between four and twelve hours after pouring. This window will extend up to a couple of days, when working in cold conditions. That's because concrete cures much more slowly in lower temperatures.
Where Cuts Happen
In order to be effective, concrete joints must be placed at regular intervals along the surface. Likewise, the joints must be of an appropriate depth, if they are to have the intended effect. A good rule of thumb is that joint depth should be equivalent to 25% of the concrete's thickness.