Concrete Broom For Stamp Concrete

Concrete Broom for stamp concreteBroom finished concrete is popular for patios, driveways and more. Sometimes called brushed concrete, a broom is used to create a slip-resistant texture on the surface of the concrete. Concrete finishers have been broom finishing for about as long as there has been concrete.

When it comes to brooming, timing is critical—brush too early and the surface will be weak, brush too late and there won’t be enough texture. It must be done while the slab is still soft, but after the bleed water has dissipated. Depending on the weather, this can take anywhere from 20 minutes to 4 hours.

Each contractor has a trick for determining when to broom concrete. Some wait until their finger doesn’t leave an imprint, others simply know it’s ready by how the broom feels when pulled across the surface.

The typical process for a broom finish is:

• Pour the slab
• Strike off with a screed
• Bull float
• Wait for the bleed water to evaporate
  Although with low water-cement ratio exterior concrete with the proper amount of air, there might not be much bleed water. Bleed water is a result of the wet concrete settling and with entrained air, it doesn't settle much and therefore little water comes to the surface. The proper amount of air is always critical in any exterior concrete that will be exposed to free-thaw action. For concrete with ¾ or 1-inch aggregate, order the concrete with 6% entrained air (plus or minus 1%)-and make sure you are getting it, otherwise the surface will spall. For smaller aggregate you need more air-7% for ½ inch and 7.5% for 3/8 inch.
• Trowel
  There's some disagreement here. In many cases, today's finishers won't trowel a slab that's getting a broom-finished surface, just bull float and broom. One veteran finisher, however, told me "I like to use a fresno to get the bull float lines out." Bob Simonelli, with Structural Services Inc., says that some troweling is OK, "but be careful not to over-finish the surface and work some of the air out." Advice in a 1996 edition of Concrete Construction's Problem Clinic, however, says you can trowel twice before brooming, but be sure to keep the trowel flat during the second troweling and begin brooming "immediately after the second troweling." If you get the surface troweled hard, it will be difficult to get much texture. PCA's Cement Mason's Guide says to use a damp broom after troweling.
• Broom the surface
  Run a concrete broom perpendicular to the slope, if there is one. On concrete that's intended to drain, though, broom marks should be run towards the drain. One thing to note is that a broom-finished exterior surface is just as durable as a smooth finish.
• Cure the concrete
  You can (and must) cure broom-finished concrete with sheets of polyethylene or by spraying on curing compound. For plain gray concrete, a curing agent with some color (typically white) in it helps you to see where it's been applied. The color dissipates after a few weeks. For decorative concrete, use a cure & seal. Don't forget the curing!