When to cut control joints in concrete slab?
Jul 01, 2021 · WHEN TO CUT CONTROL JOINTS. Make sure you are cutting joints soon enough. 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. These saws cut 1" to 3" …
What is the best time to cut control joints?
May 30, 2020 · WHEN TO SAW CONTROL JOINTS Cutting freshly poured concrete too late can lead to unwanted cracks in the concrete, rendering the joints ineffective. For most concrete work, cutting should take place within the first 6 to 18 hours and never beyond 24 hours. How soon can you cut concrete after pouring? Timing for Cutting Concrete The timing varies according to …
How deep to cut control joints in concrete?
Dec 29, 2021 · 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. Therefore, the timing of saw cuts is critical.
What are control joints in concrete slab?
Recap On Cutting Concrete Control Joints Control Joints are not intended to stop cracking but rather control cracking It is best to cut joints as early as possible either while finishing with a concrete groover or within 6-18 hours after... Plan out …
How big can a concrete slab be without control joints?
Rule #5: For better crack control keep the maximum distance between joints in feet at 2 to 2.5 times the slab thickness in inches. For a 6 in. thick slab, the maximum joint spacing should be limited to 12 to 15 ft. Exceeding a joint spacing of 15 ft.17 Apr 2018
How long after pouring concrete can you cut it?
The timing varies according to local conditions, but typically saw cuts can be done 4 to 12 hours after the concrete has been finished. In hot weather early-entry dry-cut joints are cut 1 to 4 hours after finishing; they're not cut as deeply as conventional cuts.
Are concrete control joints necessary?
Concrete expands and contracts with changes in temperature and moisture. If not properly controlled, cracks can begin to appear. Placement of concrete control joints and expansion joints are crucial when designing and pouring concrete slabs and sidewalks.3 Nov 2015
Why do you cut joints in concrete?
WHAT ARE CONTROL JOINTS? Control joints are planned cracks which allow for movements caused by temperature changes and drying shrinkage. In other words, if the concrete does crack-you want to have an active role in deciding where it will crack and that it will crack in a straight line instead of randomly.1 Jul 2021
Is it too late to cut control joints?
Joints should be sawed as soon as the concrete can withstand the energy of sawing without raveling or dislodging aggregate particles. For most concrete work, cutting should take place within the first 6 to 18 hours and never beyond 24 hours.
How many times do you float concrete?
Push the bull float in one direction only across the concrete, keeping its front edge slightly above the surface by raising or lowering the handle. Two or three times is enough. Don't overwork the concrete or you'll weaken it by drawing too much sand and cement to the surface.
What happens if you don't put expansion joints in concrete?
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.28 Jul 2017
What is the difference between expansion joints and control joints?
Control joints can be isolated within the plane being treated (brick facades, concrete sidewalks) while expansion joints must bisect the entire structure thereby creating a gap throughout all of the building elements—foundation, walls, curtainwalls, plaza decks, parking decks, floors, and roof.29 Oct 2019
Are expansion joints necessary?
Expansion joints are virtually never needed with interior slabs, because the concrete doesn't expand that much—it never gets that hot. Expansion joints in concrete pavement are also seldom needed, since the contraction joints open enough (from drying shrinkage) to account for temperature expansion.
How do you keep concrete from cracking?
If you're having new concrete poured consider the following ways to prevent cracking:Start with a sound subgrade. Make sure the subgrade is compacted. ... Modify the concrete mix. Use a low water-to-cement ratio. ... Install joints. Be active in deciding where control joints will be placed. ... Properly cure the concrete.
What is an isolation joint in concrete?
An isolation joint is a separation between adjacent sections of a concrete structure to allow relative movement in three directions and through which all of the bonded reinforcement is interrupted.
How long after concrete is poured can you cut?
In hot weather conditions, saw cutting may start as soon as four hours after the concrete is poured. In cooler weather, sawing may not start for 12 hours after pouring. 1 The best way to determine whether the slab is ready is to make trial cuts to check for raveling. Saw cutting should start as soon as the raveling stops during these trial cuts.
What happens if you cut concrete too early?
Cutting too early causes raveling, an effect created by the saw blade pulling the aggregate out of position, leaving a messy, weakened edge along the cut. This also causes undo wear on diamond concrete saw blades. Sawing too late can result in uncontrolled cracking as the concrete contracts during curing.
How far apart should joints be on a concrete slab?
Joints shall be spaced at 24 to 36 times the slab thickness but this need to be confirmed by a structural engineer. Joint spacing normally ranges between 10 to 18 feet depending on the amount of reinforcement the slab has. 1 If you are using high shrinkage concrete, you might want to decrease the cut spacing.
Why delay sawing concrete?
Some contractors delay sawing to protect their equipment and saw blade to reduce blade abrasion. There are several types of saw blades that can be used, depending on the concrete type and how soon the cuts can be started. Other factors that can lead to excessive blade wear and joint raveling include:
Why do we use saw cuts in concrete?
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. Therefore, the timing of saw cuts is critical.
How to cut joints with water?
Once you've laid out the joints to be cut, mark them using a chalk line. If you're using water cutting equipment, make sure that the water is running all the way down to the blade. Allow the blade to reach the required depth, then start walking or moving the equipment following the chalk like mark.
Is it better to have smaller cracks or larger cracks?
It is better to have smaller cracks than to increase cost by having and maintaining several joints. Under hot weather conditions, you might want to try forming a larger square and then cutting interior joints. By doing this you will be controlling fast setting concrete cracks in larger areas.
How soon after a concrete saw can you cut off a joint?
Here is a quick recap of what you need to know. It is best to cut joints as early as possible either while finishing with a concrete groover or within 6-18 hours after finishing with a concrete saw. Always cut off of your corners as soon as possible because this is usually the first place cracking starts.
What happens if you cut concrete too early?
If you cut to early though you can cause your concrete to ravel on the edge of the cuts but if you cut to late you will end up with uncontrolled cracking. There are many different factors that come in to play when it comes to timing of administering cuts such as. Tools used to cut concrete. Blade type. Saw speed.
What happens if you don't cut your concrete?
If this step is not done properly then you are essentially wasting your time. You will find that your concrete is still going to crack wild in an uncontrolled manner. To plan out where you are going to puts your cuts it is going to be important to know the depth of your concrete slab.
How much does concrete shrink?
As concrete goes through it’s curing process it shrinks as much as 1/2″ over 100′ which of course will cause it to pull apart resulting in hairline cracks. It is also important to know that the more water used in the placing process, the more likely it is to shrink and crack.
What determines when to cut concrete?
Factors such as concrete mix, weather conditions, hardness of concrete and types of machines used for making the control joints determine when to cut the concrete slab. When the concrete is sawed with the help of blade before it has reached its initial setting time, the aggregates may strew out of the concrete slab and leave a messy, ...
How long after concrete is poured can you saw?
In hot weather conditions, sawing can be started 4 hours after the concrete is poured. In cold weather conditions, sawing can be started 12 hours after the concrete is poured. The best way to determine whether the slab is ready is to make trial cuts to check for ravelling.
How to determine control joints?
If you are using high shrinkage concrete, you might want to decrease the cut spacing. The factors that determine the location of control joints are : 1 Continuity: The joints must be continuous. 2 Square Pattern: They must form segments in square patterns. 3 Reinforcement: The ideal location of placing the control joints is where the steel reinforcement is less or not found. 4 Size of the segment: The square segments formed in the hot climatic conditions are larger than conventional segments due to the fast setting of concrete in a big area.
Where to place control joints?
Location of Control Joint. It is recommended to place the control joints in the centre of the slab dividing the concrete into equal segments. The spacing of the joints is in the range of 24 to 36 times the thickness of the concrete slab. If you are using high shrinkage concrete, you might want to decrease the cut spacing.
What determines the location of control joints?
The factors that determine the location of control joints are : Continuity: The joints must be continuous. Square Pattern: They must form segments in square patterns. Reinforcement: The ideal location of placing the control joints is where the steel reinforcement is less or not found.
Why don't engineers specify the time to see joints?
Engineers don't specify a time to saw joints because they don't know what time of year the concrete will be placed or even what time of day the contractor will decide to place the concrete. Unfortunately, the time to saw joints is based on experience and trial and error.
Can you cut concrete before a saw?
Sometimes concrete cracks before the saw can cut the joint without causing raveling. In these cases, consider using a lightweight saw that allows you to cut within a few hours after final concrete finishing. Using this equipment, you can place concrete in the morning, then cut the slab during regular working hours the same day.
What Do You Understand By Expansion Joint Cutting?
Once the pouring of the concrete is done, it starts to set it and shrinks as it hardens. Ultimately, it is condensed into one solid mass. The concrete becomes prone to issues like random cracking with the leaving of moisture and hardening of it.
When Should You Cut Concrete Saw?
You must adequately understand the suitable time to see cutting the concrete slab. Several issues can arise if you focus on cutting too early. These issues involve ravelling, leaving a messy edge, especially along with any made cuts. On the other hand, if you cut too late, you can ultimately create more random cracking.
Where To Consider Saw Cutting Concrete?
Before starting saw cutting of the concrete slab, you must first choose where these specific cuts will be made on the concrete. It is recommended to begin cutting the control joints at the centre or on the column lines.
How To Saw Cut Concrete?
Once you have decided on where to place your cuts, you now need to mark them with the help of a chalk line. In this way, you would be able to keep your cuts precise. Whenever it comes to saw cutting concrete slabs, you will find the easy availability of many different methods and tools in the market.
Essential Tips To Follow For Concrete Saw Cutting
All that you need is to utilise the below-mentioned tips to ensure that you are cutting concrete effectively:
Closing Thoughts
All in all, concrete saw cutting can be a challenging task, and making any mistake can increase the project’s overall cost.
