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]. The saw-cut must be deep enough to ensure any reinforcing passing through the joint is cut through when the slab is cut. 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. 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. 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 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. RCR Flooring … When using joint groove for contraction joints, the joint should be a minimum depth of ¼ thickness of the slab. Contractor said he added fiber in the concrete. I just done cocrete work. I live in Toronto, Canada. One thing to be aware of before we go further. 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. 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. Cutting paving slabs with a hand-held saw. This is often called `jointless` slab construction. Fill the saw cut 1/4″ to 3/8″ below the concrete surface and proceed as above. The pour was complete by 12:30 PM, and the finishing was complete around 3:30 PM. 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). Early-entry Dry-cut Process Concrete Saw Slab Reinforcing at Joints Sawcut CJ Detail from ACI 360 Fig 6.8 . Control joints that are cut into the slab should be formed within 24–48 hours after pouring, depending on the ambient temperature. To get full access to all the features, please register for an account. Movement joints in concrete slab. Joint sealants are an important part of protecting joints in concrete floors. Oftentimes, concrete cutting involves more than one activity, which means that the different activities that need to be performed will demand varying charges. Yesterday was dry, sunny and relatively wind still in the basement. My concrete contractor poured a 5", 4,000 psi basement slab for my new house yesterday. 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. it has been 2 days already but contractor did not show up to cut the joint. The spacing of the joints is in the range of 24 to 36 times the thickness of the concrete slab. 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. 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. 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. 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. A control joint is an intentional point of weakness cut within the slab to … 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). Cutting paving slabs with block and slab splitters. don’t know much about this. Location of Control Joint. Contraction or Control joints are provided to avoid this crack from developing to the entire area. Please see the attached video which was found on youtube. Tip. Theres also maximum bay sizes with certain types of concrete. This method allows the placing of concrete for a complete floor area in one operation. My contractor did not cut the joints. The charges for saw cutting concrete are usually dependent on the depth per linear foot. 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. Those experts who have been using some high-shrinkage concrete may go for a lower cut spacing. 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. Contraction joints can be formed by tooling the joints while the concrete is still plastic or with a saw after the concrete has set. Joint arris protection. Contraction/control joints are placed in concrete slabs to control random cracking. Smooth Dowel Reinforcement Detail from ACI 360 Fig 6.5. When to cut control joints in concrete slab? Properly placed joints will concentrate cracking along the joint line, and reduce the potential for random cracking throughout the slab. 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. 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. 15×10 and 8×10. As the name implies, saw joints are cut with a saw (saw cut shown in above image). Dry-cut joints should be made between 1 to 4 hours after completion of finishing. Control joints are usually cut into all engineered slab floors such as the malls, low rise industrial, etc. 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. 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. 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