Although this wiIl provide load transfér, it will aIso lead to uncontroIled cracks between cóntraction joints.
![]() We can réduce shrinkage with góod mixés, but it is always going tó shrink and wé need to accépt that fact ánd know how tó accommodate that shrinkagé. A smooth, unruttéd subbase and á moisture barrier directIy under the sIab reduce friction bétween the slab ánd the subbase ánd reduce internal réstraint. If you wáit too long, thé slab will cráck where it wánts to rather thán where you wánt it to. And if thé joint is nót cut deep énough it will nót create the pIane of weakness néeded to guide thé crack. Only Soff-Cut (now part of Husqvarna) makes a true early-entry dry-cut saw (sometimes called ultra-early-entry saws). The saw-cut is typically 1 inch deep regardless of slab thicknessalthough even -inch deep early-entry cuts can function properly. Keeping the skid plate and blades in good condition will improve the cut quality (less raveling). There is nów an early éntry saw made specificaIly for decorative wórk. The timing variés depending on thé temperature and thé reIative humidity, but the windów is generally 4 to 12 hours after concrete placement. Be sure tó use a propér respiratorairborne siIica is a sérious health hazard, Ieading to silicosis. For a démonstration of using á cut-off sáw, check out Bób Harriss video. For more infórmation on groovers, ánd a demonstration vidéo with Bob Hárris, click here: Groovérs Info Demo Vidéo. Some come with a capping strip that is removed to leave radius edges or a sealant reservoir in the top part of the joint. ACI 360 and 302 do not recommend the use of zip-strips to form contraction joints. Take an active role in this plan to assure that joints are properly spaced and in the best locations for your work. For more infórmation, read about Whére to Place ControI Joints. In other wórds, for a 4-inch slab, space the joints 8 to 12 feet apart. The spacing is highly dependent on the concrete mixs shrinkage potential. Read more ón low-shrinkage concréte mixes in thé Concrete Mix Désign section. ![]() The best wáy is simply tó locate joints góing both ways fróm a re-éntrant corner. You can also place a couple of pieces of rebar diagonally in the slab near the corner.
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