When concrete is poured, it is very important to cut expansion joints in the concrete. By cutting control joints in the concrete you can better control the random cracking that inevitably occurs in concrete slabs soon after the concrete is poured and set.
In hot weather, concrete might crack if joints are not cut within 6-12 hours after finishing concrete. In this condition, if you don't want to use a grooving tool to cut joints, there are early-entry dry-cut lightweight saws that can be used almost immediately after finishing.
For most concrete mixtures, this means sawing should be completed within the first six to 18 hours and never delayed more than 24 hours. Early-entry saws are available which may allow cutting to begin within a few hours after placement.
Cutting concrete is essential to control cracking.
All newly poured concrete shrinks slightly as it dries which can result in cracks. To control potential cracking the concrete is cut. These cuts are called Construction Cuts – also known as Control or Expansion Cuts.
Saw cuts are a used to create control joints in concrete, which help control where cracking occurs due to shrinkage. The cuts should be made at a predetermined spacing and only after the concrete has obtained sufficient strength but before internal cracking begins.
HOW DEEP SHOULD A CUT BE? If you are working on a project with a spec included, there should be a depth listed that you need to achieve. If not, you need to have a minimum of a 1” depth, but you can also base it off the thickness of the slab. A good rule of thumb is to make your cut ¼ the thickness of your concrete.
All concrete will shrink slightly as it dries and, when it's set, will expand or contract depending on the ambient temperature. To prevent cracks from forming, concrete expansion joints should be incorporated to allow for movement, particularly in slabs with a surface area exceeding 6m2.
Slab sawing is like wall cutting, except instead of cutting a vertical wall, you cut into the horizontal floor. You use a slab saw when you need to cut into concrete floors, bridges, roads, or anything flat made of concrete.
If you're working on a concrete project, then you'll need to use a concrete edger at some point. A concrete edger is a tool used to create a clean edge along the top of a concrete slab. This is important for two reasons: it looks nice and prevents water from seeping underneath the concrete and causing damage.
If you're using concrete to make a sidewalk, the shrinking concrete will cause cracks to appear as it dries. To prevent sidewalks from cracking in random spots and breaking apart, builders make lines in sidewalks.
Contractors mainly use wet cutting for tile work, reinforced concrete, metal, bricks and masonry. It can produce long, clean cuts because it is less prone to overheating or wearing the blade. If electrocution is a potential hazard, consider dry cutting instead.
Troweling too early can also result in eventual scaling and blisters due to trapped rising bleed water and air. Early scaling results in a weak layer of concrete that may break when exposed to winter conditions and deicing chemicals. Using a steel trowel too early could also cause the top layer to delaminate.
If you're wondering why your concrete cutter has suggested using wet cutting, it's because they value worksite safety above all. One of the biggest risk factors when dry cutting into concrete, mortar, bricks, pavers, tiles or anything that contains crystalline silica (quartz) is the emission of tiny harmful particles.
A high flow high-pressure water jet can cut through concrete by eroding the cement. At high pressure with a lower flow, water can actually remove coatings without damaging the sound concrete below. Add an abrasive to the jet and water can completely cut through a concrete slab with rebar inside.
If you have a concrete floor in your commercial building, you know expansion joints are necessary to allow for the natural expansion and contraction that occurs from temperature changes. Without these joints, large cracks can travel across your floor, creating costly damage.
Yes. You can cut concrete board, pavers, blocks, walls and even slabs yourself. The tools and techniques needed will vary depending on the project. However, a circular saw is usually enough for most projects where the depth is less than seven inches.
It is important to float the concrete before excess moisture or bleed water rises to the surface and accumulates. Excess water can significantly weaken concrete; therefore, floating must occur before too much water bleeds to the surface.
When you don't finish concrete floors, many things can occur such as wear and tear in high traffic areas, unwanted and unsightly cracks, higher associated costs, increased cleaning and maintenance, and water retention.
Expansion material is placed between sections of concrete. It's that black stuff you see between concrete slabs sometimes if a contractor doesn't put a sealant on top of it. If they do seal it, you're likely going to see a grey sealant between sections of concrete.
In Australia, concrete slabs must be fixed in adherence with the Australian Standards AS 2870 and AS 3600. The most common slab thickness in Australia is between 85mm and 100 mm. The thickness of concrete slabs is usually stated in specification documents.
Why do concrete contractors add lines? Cracking caused by the expansion and contraction of concrete due to temperature changes is thwarted by these separations. Without these spaces, in time, cracks could lead to the destruction of the concrete surface.
Wet concrete is very difficult to cut, and fully cured concrete can fracture as it's being cut. So if possible, cut concrete when it's hard but only half cured. The cut will come out smoother with less dust.
Depth of Cut
In case the cut is too deep, the interlocking may not be sufficient enough for transfer of loads. On the other hand, if it's too shallow, it might result in random cracking. The contractor should also make sure that the concrete cut depth meets the appropriate structural engineering specifications.
The answer is that concrete never cures completely. It is always hardening a little bit more each day. The way concrete hardens is a function of the cement particles reacting with the water it is mixed with. As the cement bonds with the water molecules, the concrete gets harder.
Cracking can occur in both hardened and fresh, or plastic, concrete as a result of volume changes and repeated loading. This involves tensile stresses being loaded onto the concrete, the cracks occurring when the force exceeds its maximum tensile strength.