Table of Contents
Why do you float concrete?
Float the concrete when you’re done grooving and edging (Photo 6). Floating removes the marks left by edging and brings the surface one step closer to a final finish. You may have to bear down on the float if the concrete is starting to harden.
Can you just bull float concrete?
Bull floating is performed on freshly poured concrete during the initial finishing process before surface water, called bleed water, appears. Floating with a hand or power float, is a final finishing procedure performed after the bleed water has dried.
Can you smooth out concrete after it dries?
Sand the Surface and Wash the Concrete Finish by fine-tuning with light sandpaper, until the surface is perfectly smooth. We recommend using a hand planer to smooth and compact the surface. If the concrete dries a lot then we recommend that you add water to the surface, this will help you give it a good finish.
What may occur if a slab is floated too soon?
More often, premature finishing or improper first (bull floating) or second floating results in trapping rising bleed water and air below the top surface of the concrete (Image 2). When this occurs, the resulting weak or soft zone below the surface causes the top surface of the concrete to flake or scale off.
What is the difference between a float and a trowel?
STEEL TROWELS. Purpose: Used after floating to produce a smooth, hard, dense slab surface. What’s available: Steel trowels look similar to hand floats, except the blades are thinner and the handles are open rather than closed. The key difference among tools is the type of steel used for the blade.
How long should concrete set before power trowel?
Usually, this can take as less as 20 minutes to even four hours in some cases. It depends on the temperature on the concrete site, humidity, and the intensity of wind: If the temperature is high, the water on the concrete surface would disappear earlier and vice versa in case of cold temperatures.
When should you Powerfloat?
A rough guide for considering when to begin power floating is when walking on the surface leaves indentations of 3-4 mm. If the concrete is too wet the machine will tear up the surface, and if it is too dry, it will not be possible to trim high spots or fill low spots effectively.
What can I use instead of a bull float?
Fresnos are used for troweling slabs that do not require a hard trowel surface. A Fresnos will speed up the troweling process. Fresnos should not be used as bull floats. Troweling can also be accomplished by machine.
How much rebar should I use in a slab?
Contractors sometimes use the “1/8 Rule,” meaning the size of the rebar is 1/8 the thickness of the slab. For example, a slab that is 6 inches thick might have rebar marked as size 6 or 3/4-inch. Slabs for septic tanks may require the use of both welded wire fabric and rebar.
How do you know when to trowel concrete?
A useful guideline to know when you can start up your trowel, is when the operator can stand on the concrete surface, and leave footprints about 1/8”-1/4” in depth and you can walk on it firmly without the top layer sticking to your boots it is ready to power float.
What is the best temperature to pour concrete?
Experts agree—the best temperature to pour concrete is between 40° – 60°F. When temperatures dip below 40°F, the chemical reactions that strengthen concrete slow down and can lead to weaker concrete.
Can you sand concrete with a palm sander?
If you only have a small area to sand, you can also use a palm sander, orbital sander or belt sander. Rough imperfections may require the use of a special diamond disc and a concrete floor grinder.
What happens if you dont trowel concrete?
If you haven’t done this before or only done it a few times you are likely to make two mistakes; troweling too soon and troweling too much. Both of these have the effect of pulling fines and water to the surface. This can lead to a weakened surface, tiny cracks and a white dusty surface.
How long do you wait to bull float concrete?
Darbying or bull floating should be done immediately after “screeding”, or after the concrete has been tamped if tamping was done. This process should be finished before excess moisture or bleedwater appear on the surface.
Can you over work concrete?
Never overwork or over finish the surface of any exposed concrete slab. This brings too much fine material to the surface, works out the designed air entrainment*, and will weaken the surface of the slab leaving the top of slab more vulnerable to freeze/thaw damage and sheet scaling*.
Why does magnesium float for concrete?
Magnesium smooths the surface of fresh concrete and opens the pores for proper evaporation, all without pulling the surface like a wood or resin tool. Extruded floats are made by pushing molten magnesium through a die (think Play-Doh), so the floats are the same profile from end to end.
When should I take magnesium trowel?
ANSWER: A hand-held magnesium float, steel trowel, and fresno are different tools and should be used in the proper sequence when finishing a hard-troweled floor. Improper or out-of-sequence use can cause surface defects, including blistering and delaminations.
