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. |