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Suggestions for Placing Concrete Slab to Minimize Random Cracking.

Step

What You Do

Why You Do It

1

Level and compact sub grade, place 4” of damp sand and grade so concrete poured is a consistent depth.

The sand provides a cushion for the concrete, and good drainage.

2

Separate your new concrete from all existing concrete with ½” felt. Felt must match the depth of your new slab.

The felt separates your new concrete from existing, so it may shrink, expand, and move up (or down) without a detrimental effect.

3

Screen off our concrete.

Makes sure there are no low spots.

4

Roller-bug your concrete.

Once over the surface, it helps vibrate, consolidate, and give you a better finish.

5

Float concrete with wood bull float only.

Wood keeps the surface open and allows the concrete to bleed. This prevents water entrapment, discoloration, and/or plastic cracking.

6

Cut control joints perpendicular from edge ¼ the depth of the slab, using appropriate spacing. 4” slab would be 8’ x 8’

These joints should allow the concrete to crack in the joint, taking the path of least resistance.

7

Allow all bleed water to evaporate from the surface; then, you can finish the concrete with metal trowels.

If you do not wait for all bleed water to evaporate, you end-up troweling your bleed water back into the surface, dramatically changing your water:cement ratio, on the surface, causing a weaker surface.

8

When surface is finished, spray with a concrete cure; if the concrete is colored, you must use a cure formulated for colored concrete.

This protects the concrete from wind and heat, and allows your slab to cure on its own, giving you a much better finished product.

9

Never add water or dry cement to the surface of your slab.

These two things also change water:cement ration on the surface and can ruin your slab.

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