The following is a list of items, techniques and actions for properly placing concrete. Allow yourself time to do the job well without rushing, although you must go straight to work when the concrete is mixed. Make sure you have enough help, too.
Tools you’ll need
- Bull Float
- Concrete Rake
- Concrete Broom
- String Lines / Chalk Line
- Steel or Wood Stakes
- Tape Measure
- Adequate drainage
- Class 5 or better base material
- Compact base material to maintain thickness of desired depth of concrete
- Remove large or excess debris not consistent with sub base material
- Prior to placing concrete, the sub base should be saturated not dry
- Never place concrete directly on clay. Always place a minimum 6” of Class 5 material on clay to help reduce frost heave.
- Minimum thickness for concrete slabs is 4”: 2×4 lumber or greater is recommended
- Use wood or steel stakes to support the formwork with proper spacing to prevent the concrete from blowing out the forms
- Run string /chalk lines to ensure proper slope required for application
Reinforcing: Three types to choose from
- Fibermesh (Recommended)
- Excellent against surface cracking
- Improved impact resistance
- Mitigates water migration
- Distributes uniformly throughout the thickness of the slab
- Rebar (#3 bar every 3-4’ on center)
- Rebar should be kept at the top third of the slab.
- Wire Mesh (6x6x10x10)
- Wire Mesh should be kept at the top third of the slab.
Job site preparation
- Adequate entry and exit point for ready-mix trucks.
- Ensure the construction road is stable and safe for ready-mix truck to maneuver.
- Concrete has a workability life of 3 hours from the time it is batched. Therefore, please ensure the job site is complete prior to the ready-mix truck arriving on site.
Mix verification and adjustments
- Once the ready-mix truck arrives, please verify the certificate of compliance to verify the correct mix design and location.
- Once the mix and location has been verified, adjust the concrete to the desired slump for placement. Note the allowable water on the certificate of compliance to meet the water-cement-ratio for maximum durability.
- Placing procedure
- After verifying the proper mix, slump and location, you can begin placing the concrete.
- Whether placing by wheelbarrow, buggy or truck chute, ensure you have enough manpower to complete the task prior to initial set of concrete (15 wheelbarrows equals 1 cubic yard of concrete)
- While placing, concrete should be maneuvered to ensure proper thickness by use of
- leveling (screed) and a concrete rake. When leveling (screed) your concrete, it’s best to use a 2×4 lumber in a back and forth motion.
- After placing, leveling and raking, immediately close the surface by using the concrete bull float.
- Once the surface is closed and after bleed water has dissipated proceed to place control joints 2 times the thickness of the slab using the jointer. The depth of the joints should be 1/3 the depth of the slab.
- Use the edger around the perimeter of slabs.
- Finally, after jointing, immediately broom the surface with the concrete broom. Ensure you keep the broom damp during this process.
- Wait a minimum of 7 days to remove forms.
You must cure concrete immediately after you’ve placed and finished it so the desired properties develop. Ultimate strength gain is achieved with curing; almost half the potential strength is lost without it. Also, well-cured concrete improves durability against moisture, harmful chemicals, surface wear, and abrasion. Finally, proper curing enhances the serviceability and appearance of your concrete over time.
Sealing compounds are liquids applied to the surface of hardened and cured concrete to reduce the penetration of deicing solutions that cause increase freeze-thaw damage. These liquids are typically not applied until the concrete is 28 days old.