Concrete sawing has a vital role to play when installing and curing fresh concrete. Contractors use heavy-duty concrete saws to create control joints on the surface of a newly poured slab. These control joints relieve the shrinkage forces that would otherwise cause serious cracks to form on the surface of the concrete.
Of course, concrete sawing can only accomplish this goal if performed according to strict standards. Inexperienced contractors often fail to create the kind of joints needed to properly relieve internal stresses. If you would like to learn more about what it takes to saw concrete the right way, read on. This article outlines three aspects of successful concrete sawing.
As concrete cures, water evaporates out of its surface. This evaporation often causes the concrete to pull apart from itself, resulting in the formation of unattractive and structurally problematic cracks. Control joints prevent cracks from forming by allowing the concrete room to shrink without detrimental effects.
In order to provide effective crack protection, however, joints must occur at specific intervals. Most contractors determine joint spacing according to the thickness of the slab. The American Concrete Institute advocates for a rule of three, meaning contractors should multiply the thickness of the slab (in inches) to determine the control joint spacing (in feet).
Therefore, for a 2 inch slab, control joints should occur every 6 feet. In some cases, contractors may choose to place joints more closely than this, for instance to compensate for the additional stresses caused by expansive soils.
Another key aspect of joint spacing involves the relative dimensions of the panels created by the joints. The closer you can make the panels to squares the better. Of course, square panels may not always be practical. In that case, a general rule of thumb states that the panel length to width ratio should never exceed 1.5.
Even well-spaced control joints may fail to prevent cracking if the joints are not deep enough. Shallow joints simply do not prevent enough relief for the shrinkage forces encountered during the curing process. For optimal results, joints should have a depth of either 1/4 or 1/5 the total thickness of the slab.
Joints deeper than 1/4 the slab thickness won't add any extra benefit. In fact, excessively deep joints may lead to problems down the line, since they reduce the amount of aggregate interlock for the pavement.
Unfortunately, not all aspects of joint cutting are as regimented as those discussed above. In particular, the question of when to cut control joints requires the judgment of an experienced concrete contractor. While the particular proportions of the concrete mix play a large role in joint timing, numerous other factors may come into play.
Such factors include temperature, humidity level, and the method being used to cure the concrete. In some cases, sawing may commence as quickly as four hours after finishing. In other cases, contractors may need to wait as long as three days before sawing. Fortunately, contractors usually understand the best timing for a given season in their region.
Even then, however, most contractors proceed by a trial and error process. Workers often make tests cuts at the beginning of the potential sawing window. If edges of the test cut ravel - in other words, if aggregate crumbles out of the concrete matrix - then control joint formation must be delayed.
Once a test cut shows only minimal raveling, a contractor may proceed with confidence that the control joint formation won't negatively impact the concrete. Control joints play a vital role in the long term stability of a concrete slab. For more information about what it takes to create control joints the right way, please contact the concrete sawing experts at Capital Concrete Cutting.