This civil engineering article sheds light on concrete floor slab detail, floor slab thickness and the steps to get rid of common mistakes in concrete floor slab construction.
To increase the longevity of concrete floor slab, proper care should be taken for concrete floor slab construction regarding proper base preparation, mix design, placement, finishing, and curing.
Floor Slab Thickness
In any residential construction, the typical floor slab thickness should be 4 inches. In case of greater load that is necessary for motor homes or garbage trucks, five to six inches should be retained.
Ground Floor Slab Construction
- To develop the base, the ground level should be cut into to the proper depth to accommodate the concrete slab thickness. All sorts of organic material and large hard objects like stones and tree roots should be removed to a depth of minimum 4 inches.
- When it is required to construct the grade, gravel or sandy soil should be used and the final base should be compacted with a vibratory plate or equivalent device. The edge forms should contain any straight material that should be fixed into position.
- In case, the straight lumber is not accessible, plastic or metal forms can be used in place of it. Prior to arrange the formwork, a string line should be set with grade stakes or batter boards to retain a square, level reference.
Concrete Mix For Floor Slab
- The concrete mix for floor slab should satisfy the compressive strength requirements (normally 3000 pounds per square inch) without measures that leads to unnecessary shrinkage. Due to water increases shrinkage and cracking, a plasticizer should be applied to attain necessary slump. In order to avoid plastic shrinkage cracking, the fibers should be applied. Greater strength and entrained air are necessary for exterior slabs which are uncover to freezing weather or deicing chemicals.
- Refrain from using extra water at the jobsite exceeding 1 to 2 gallons per cubic yard. When extra slump is required, consult with the mixer truck driver regarding the quantity of water to be added without taking the concrete out of specification.
- It is suggested to allocate the concrete around the slab area as close to its final position as possible, and then rake it into position. To consolidate low-slump mixes, a handheld vibrator or a vibratory screed should be used. To label the surface, finish with the least amount of force and strokes of the float.
- The control joints should be formed no farther apart than 24 to 30 times the slab thickness and under no circumstances exceeding 15 feet along both the width and length of the slab by pushing a 1-inch deep grooving tool into the surface.
- If the joint spacing surpasses 15 feet, the load transfer devices like dowels or dowel plates should be utilized. For slabs with long joint spacing or no joints, steel reinforcement is necessary. Though, it can raise the scope for random cracking, but it will retain cracks firmly to maintain good structural performance.
Curing Concrete Floor Slab
- There should be exact curing conditions and the curing method should be set up once the finished surface can control the damage. It should be kept in mind that the concrete is not freeze or dried out.
- A curing compound should be provided over the surface, or proper moist curing should be retained.
- In case of freezing, the slab should be wrapped with an insulator, like insulating blankets or a 4-inch-thick layer of straw that is weighted down so that it can’t wipe out.
- The insulator should be kept in proper position unless the concrete attains a minimum strength of 500 psi. It generally happens within a few days
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