Contraction joints are used in slabs-on-ground to create weakened planes that limit the frequency and width of random cracks caused by volume changes due to restrained drying shrinkage, ther-mal contraction, or both. Introduction: This page is part of a series of pages that consider cutting techniques used with flags (or slabs, if that's what you call 'em). Plan out your control joint spacing 24-36 times the depth of your concrete slab; Always cut off of your corners as soon as possible because this is usually the first place cracking starts A control joint is an intentional point of weakness cut within the slab to … My concrete contractor poured a 5", 4,000 psi basement slab for my new house yesterday. Control joints also called contraction joints are placed in concrete slabs to control this cracking. In the first instance, a flexible material is inserted along the length of the joint before the concrete is poured [link to how to lay a concrete slab]. Movement joints in concrete slab. Joints are usually a metal joint (armoured joint) built into the floor during the concrete pour; or a saw-cut joint (induced joint) cut into the finished floor. The charges for saw cutting concrete are usually dependent on the depth per linear foot. In ACI 360, Section 6.2 – Load transfer mechanisms, the primary, and most effective, method of load transfer across the CJ is the use of smooth dowels. This is often called `jointless` slab construction. Contractor said he added fiber in the concrete. If ¼ of your slab’s thickness, doesn’t reach 1” make sure you still cut at least a 1” depth. In ACI 332 Section 10.6.2 – Minimum steel reinforcement based on joint spacing, the term “without steel reinforcement” in Table 10.5.2 refers to both plain concrete and concrete reinforced for crack control only. Hello all, I have the same issue as Ken. Use a low RPM setting when cutting through the concrete to keep the blade from overheating and throwing chunks of concrete from the surface of the slab. Dry-cut joints should be made between 1 to 4 hours after completion of finishing. The agilia mix I usually use for instance. Why seal an expansion joint? The saw joints run in both directions at the spacings indicated above. I hosed the slab down twice, after … 3. Those experts who have been using some high-shrinkage concrete may go for a lower cut spacing. Purpose of Control Joints. This method allows the placing of concrete for a complete floor area in one operation. Control Joints & Saw Cut Filling. Please see the attached video which was found on youtube. The construction joints are to placed at the contractor's discretion and locations are specified parallel to the longitudinal steel spaced at approximately 16ft to 18ft oc (over the pier centerlines). don’t know much about this. Tip. On a 4″ slab, that is a 1″ deep saw cut and nobody want to use that much caulking. PJE1 (Materials) (OP) 29 Sep 05 10:14. Typically concrete joints should be cut in less than a day, but the specific timing depends on numerous factors, including local conditions, weather and concrete mix. Keyed joints are not recommended for industrial floors. Control joints are usually cut into all engineered slab floors such as the malls, low rise industrial, etc. Whether the joint is saw-induced (saw-cut) or a formed construction joint (armoured joint), filling the gap with a sealant helps to support the joint and prevent arris damage. control & saw cut joints in concrete slabs; Welcome to the Revit Forum You are currently viewing as a guest which gives you limited access to view attachments, ask questions and access other features. Joint sealants are an important part of protecting joints in concrete floors. They may be formed either by saw cutting the slab after it has hardened or by casting a crack inducer into the slab when the concrete is poured. Keep in mind that joints have to be spaced at 25 to 32 the piece’s thickness, while this has to be initially set by your expert. Early-entry Dry-cut Process Concrete Saw Slab Reinforcing at Joints Sawcut CJ Detail from ACI 360 Fig 6.8 . The costs of saw cutting a concrete slab are solely dependent on the size of the slab surface and the condition/location of the wall. Since all concrete floors are subject to cracking, Control Joints (or contraction joints) should be placed in fresh concrete to create weakened planes that control the severity and pattern of cracks. Theres also maximum bay sizes with certain types of concrete. See Figure 1 for other methods of forming free joints. The pour was complete by 12:30 PM, and the finishing was complete around 3:30 PM. Fill the saw cut 1/4″ to 3/8″ below the concrete surface and proceed as above. A good rule of thumb is to make your cut ¼ the thickness of your concrete. To get full access to all the features, please register for an account. For large area pour construction, sawn induced contraction grooves are cut into the slab surface at 6 to 8m centres, both ways. I just done cocrete work. In winter, It should be done within 48 hours. The alternative and strongly preferred method of crack control, by providing appropriate reinforcement, is also discussed. Control joint cuts are also made once the concrete is poured using a concrete saw, whereas an expansion joint is a predetermined gap created between the pouring of two distinct slabs. Cutting paving slabs with a chisel and hammer is a time-honoured way of getting the job done. A fresh concrete mixture is a fluid, plastic mass that can be molded into virtually any shape, but as the material hardens there is a reduction in volume or shrinkage. Smooth Dowel Reinforcement Detail from ACI 360 Fig 6.5. Control joints that are cut into the slab should be formed within 24–48 hours after pouring, depending on the ambient temperature. The first page examined the basic principles of cutting-in: this page looks at how curves are cuts; subsequent pages consider other cut features such as notches and flagged radii. Saw cut and seal method in concreting defines where cracks occur and hides them under a tidy sealed crease instead of letting concrete crack at random. Control joints should be in the centre of the slab dividing the concrete into equal segments. Contraction or Control joints are provided to avoid this crack from developing to the entire area. Registration is fast, simple and absolutely free, so please register today! The purpose of this AD Note is to discuss the issues involved in the use of saw cutting to form crack inducing joints in composite slabs and to emphasise the risks involved and the care needed in practice. Filling the saw cut is mandatory as control joints are 1/4 the thickness of the concrete. Contraction (Control) Joints: Place contraction joints at the re-entrant corner to create weak planes in the slab that will increase the possibility of cracks forming in the bottom of these contraction joints rather than at ~135° from the corner. 15×10 and 8×10. Location of Control Joint. When you are looking for saws to do relief cuts, make sure that it is a down cut. The slab area is approimately 28000sf. With our many types of floor saws we can accommodate diamond floor sawing and concrete floor cutting projects in the most challenging of environments. The saw cut & seal is the most basic type of formed joint. The spacing of the joints is in the range of 24 to 36 times the thickness of the concrete slab. When to cut control joints in concrete slab? Once the concrete gets poured and hardened, the water in it starts to evaporate and makes the concrete to shrink and develop shrinkage cracks, especially on longer slabs. The saw-cut must be deep enough to ensure any reinforcing passing through the joint is cut through when the slab is cut. Yesterday was dry, sunny and relatively wind still in the basement. 2. Saw-cut joints should be done within 4 to 12 hours after the concrete has been finished. My contractor did not cut the joints. What is Contraction/Control Joints? Joint arris protection. I live in Toronto, Canada. Otherwise, radiant heat tubing can be damaged when saw cutting joints, causing construction delays and expensive repair costs. Timing is critical for saw-cut joints; cutting too soon spoils the concrete while cutting too late fails to fulfill the purpose. Concrete saw cutting is commonly used for cutting hard flat surfaces such as motorways, bridges, pavements and floor slabs, along with trenching, joints, demolitions cuts and floor chases. Cutting paving slabs with block and slab splitters. 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. And, if you're looking to create curves with your paving we have some tips for cutting curved slabs too.-----3 STEPS TO CUTTING PAVING SLABS WITH A CHISEL AND HAMMER. As the name implies, saw joints are cut with a saw (saw cut shown in above image). One thing to be aware of before we go further. Oftentimes, concrete cutting involves more than one activity, which means that the different activities that need to be performed will demand varying charges. Post Tension Slab | Eliminating cracks and joints in concrete Contraction/control joints are placed in concrete slabs to control random cracking. On no account should concrete dust be allowed to rest on the surface for any length of time as it will set and could damage the surface when forcibly removed. Saw-cutting should start as soon as the ravelling stops during these trial cuts. it has been 2 days already but contractor did not show up to cut the joint. In some cases, control joints are done after the concrete has cured and hardened by cutting lines in the floors with a concrete saw. Cutting paving slabs with a hand-held saw. RCR Flooring … In summer, this should be done no later than 24 hours after pouring. Sawn joints are normally cut a week or more after sealing, so that the concrete will have had a reasonable amount of time to cure and avoid 'spalling' at the cut edges, and for the sealant to protect the surface from the concrete dust. Contraction joints can be formed by tooling the joints while the concrete is still plastic or with a saw after the concrete has set. When some steel fibre types are used and dosage is high enough, large area pours can be constructed without joints except for a perimeter construction joint. When using joint groove for contraction joints, the joint should be a minimum depth of ¼ thickness of the slab. require contractors to saw cut contraction joints in elevated slabs. Normally, the spacing between the joint maybe around ten to twenty feet, it also depends on the volume of the slab’s support. Properly placed joints will concentrate cracking along the joint line, and reduce the potential for random cracking throughout the slab. WHAT KIND OF SAW TO USE. Sign in to follow this ... and not at the points where you would think was a "weak point" As he is planning to polish the concrete and varnish it, an expansion joint or 2 would probably have been better than 2 cracks. Early-entry Dry-cut Process Concrete Saw Slab Reinforcing at Joints. Overnight temp fell into the 50's. 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