Tempo:
7. After the water sheen has disappeared and as soon as the concrete can support foot traffic without indentations occurring, edging, jointing and floating operations can begin. Performing any of these operations while bleed water is present will cause serious dusting or scaling. 8. Proper control jointing or grooving may be necessary to avoid minor random cracking in the slab. Control joints should be placed on line with interior columns and at changes in width of the floor slab (Figure 48). The maximum spacing of control joints should be between 4.5 and 6.0 m (15 and 20 ft.) in either direction. Joints may be formed in the freshly placed concrete by cutting grooves by hand with a jointing tool as soon as the concrete is firm enough. The depth of joints should be about one-quarter the thickness of the floor slab. 9. As soon as the floor surface has been finished, curing should begin. It should continue for at least five days at air temperatures of 21°C (70°F) or higher, or for seven days at
temperatures of 10 to 21°C (50 to 70°F). Curing may be carried out by ponding water on top of the slab (by temporarily plugging all floor drains), or by covering with burlap kept continuously wet. If this is not practical, liquid, membrane-forming curing compound may be spread on the concrete surface. Use curing compounds that are compatible with tile adhesives if the floor finish is to be tiled. The 2010 NBC provides specific protection against future radon ingress into conditioned spaces in housing by requiring compliance with one of the following two methods:
The first method requires a gas-permeable layer between the ground and the air barrier that allows for depressurization of the space below the soil gas barrier. This layer could be coarse sand or a dimpled membrane or another product that allows the collection and extraction of gas. An inlet needs to be provided that allows for effective depressurization of the gas-permeable layer. An outlet must be provided that permits
48 Location of control joints
1. control joints within 3 m (10 ft.) of corners 2. spacing of joints 6 m (20 ft.) maximum 3. joints incorporate side of opening 4. control joint in floor slab 5. floor slab joint spacing of 6 m (20 ft.) maximum 6. control joint around column footings (see note)
1
1 2
3 4
3
3
5 5
6
Note: The diamond-shaped joints (6) may be omitted if column footings are below floor level and the column is wrapped with two layers of sheathing membrane or joint filler to break the bond.
temperatures of 10 to 21°C (50 to 70°F). Curing may be carried out by ponding water on top of the slab (by temporarily plugging all floor drains), or by covering with burlap kept continuously wet. If this is not practical, liquid, membrane-forming curing compound may be spread on the concrete surface. Use curing compounds that are compatible with tile adhesives if the floor finish is to be tiled. The 2010 NBC provides specific protection against future radon ingress into conditioned spaces in housing by requiring compliance with one of the following two methods:
The first method requires a gas-permeable layer between the ground and the air barrier that allows for depressurization of the space below the soil gas barrier. This layer could be coarse sand or a dimpled membrane or another product that allows the collection and extraction of gas. An inlet needs to be provided that allows for effective depressurization of the gas-permeable layer. An outlet must be provided that permits
48 Location of control joints
1. control joints within 3 m (10 ft.) of corners 2. spacing of joints 6 m (20 ft.) maximum 3. joints incorporate side of opening 4. control joint in floor slab 5. floor slab joint spacing of 6 m (20 ft.) maximum 6. control joint around column footings (see note)
1
1 2
3 4
3
3
5 5
6
Note: The diamond-shaped joints (6) may be omitted if column footings are below floor level and the column is wrapped with two layers of sheathing membrane or joint filler to break the bond.
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