Concrete finishing is an art and a science that takes years to perfect. Professional concrete finishing is an exact skill that requires years of hands on experience. For those who would rather do it themselves, we offer the following homeowner’s introduction to the many types of concrete available. This section contains common definitions and helpful tips for preparing, placement, finishing, and curing of concrete along with tips and ideas for ordering the right concrete for your job.
Accelerator – when added to concrete, this will increase the rate of hydration, shortening the time of setting. This “accelerates” the hardening and strength development.
Aggregate – the granular component such as sand, gravel, or crushed stone that is combined with the hydraulic cementing medium to make concrete or mortar.
Air Entrained – intentionally incorporating microscopic air bubbles into the concrete during mixing. this process increases durability and resistance against damage by repeat freeze-thaw cycles and deicing chemicals.
Batch – the amount of concrete mixed at one time.
Bleeding -water at the surface because of the settling of solid materials within the concrete.
Bull Float – a large, flat, rectangular tool made of wood, aluminum, or magnesium. Usually 8 inches wide and 48 inches long with a handle 4 to 6 feet in length. This is used to smooth fresh concrete or other unformed surfaces.
Cubic Yard – concrete is sold by volume. To calculate the amount needed for your project, use the online concrete calculator.
Curing – maintaining the concrete at a satisfactory temperature and moisture content during the early stages so that desired properties develop.
Gravel Mix – a concrete mix that contains natural gravel coarse aggregate. This type is normally used for interior applications such as garage floors, basement floors, and footings.
Performance Mix – a concrete mix that can be specified to meet minimum compressive strength requirements measured in pounds per square inch (such as 3000psi, 3500psi, and 4000psi). More psi results in more strength and durability. This is similar to a sack mix (see definition), but achieves hardened characteristics by use of pozzolans or admixtures. The slow set times of this type make it ideal for the homeowner. This must be requested at the time of order.
Portland Cement – hydraulic cement that sets and hardens through a chemical reaction with water.
Ready Mixed Concrete – concrete specifically made to be delivered to the customer in an unhardened state.
Sack – 94 pounds of Portland cement.
Sack Mix – The amount of cement, stated in sack per cubic yard of concrete (such as 5sack, 5.5sack, or 6sack). The higher the sack number, the stronger the resulting concrete. Request when placing order.
Screeding – forming the surface by using screed guides (or forms) and a strike off.
Set Time – the amount of time in hours and minutes measuring the stiffening of the concrete and resistance to penetration.
Slump – a term of measurement of freshly mixed concrete. When a conical mold (slump cone) is lifted from the test source, the slump is the measurement in inches that the concrete subsides.
Sub Grade – the prepared and compacted soil ready to receive the concrete. The surface should be granular and free of clay.
Tools (concrete) – our supply store has more information on the purchase or rental of proper finishing tools. Coming soon!
The Four Steps to Successful Concrete Finishing:
Step 1: Preparation and Planning
- The sub grade must be compacted and free of standing water.
- Forms must be secure and strong enough to hold the pressure of fresh concrete
- Place your concrete order with as much advance notice as possible to insure availability
- Arrange enough help to place and finish concrete If there is under 150 square feet of concrete to finish, plan on a minimum of two people
- Plan on one more person for each additional 200 square feet of concrete
- Arrange pick-up or delivery of finishing tools and equipment at the supply store In order to avoid confusion, assign specific tasks to helpers before concrete arrives (designate who will be screeding, bull floating, washing tools, etc.)
- Make sure there is acceptable access for delivery – stable soil (supporting up to 80,000 pounds), wide enough (10 feet wide by 14 feet high), and proximity (the chute can reach approximately 16 feet)
- Determine what type of control joints will be used to control cracking, hand tooled or saw cut.
- Concrete for residential uses should be at least four inches thick
- The joint depth should be at least 1/4 the thickness of the concrete
- Placing control joints should be part of the planning process
- Control joints should not be farther than ten feet apart
- Sections should be square or nearly so
- Avoid creating triangles or odd shaped panels when placing joints
Step 2: Placement:
The concrete should be discharged from the truck as close to final position as possible (avoid “dragging” the concrete long distances) Concrete must be discharged in a timely fashion upon arriving at the job site.
During the placement process, follow these easy steps:
- Strike off or “screed” the concrete to the desired elevation or form height with a wood or magnesium straight edge Immediately after striking off, and before bleed water appears, the concrete must be bull floated.
- Once concrete has been bull floated, no finishing may take place until the bleed water has completely evaporated.
Step 3: Finishing
Finishing is simply the actual process of texturing the surface of the concrete. If you hand tool the control joints, it must be before the final texture is applied. There are four different possible finishes:
- Broom or brush finish This finish is recommended for areas that require skid resistance such as driveways or sidewalks. To achieve this texture, wait until the concrete reaches the desired consistency and then simply push or pull the concrete broom across the surface. Deciding when the time is right to apply the broom depends on how deep the texture is desired.
- Porous trowel finish This type of surface is smoother than the brush finish. This can be used in areas such as porches and patios where skid resistance isn’t as important. For a porous trowel finish, smooth the trowel across the concrete when it has reached the consistency that will bear your weight and leave a footprint of about ¼” depth.
- Hard trowel finish A smooth finished concrete surface for use when a non-porous surface is required such as shop, garage, or basement floors. In order to achieve a hard trowel finish, a power trowel must be used. These are available for rent in our supply store.
- Decorative or architectural finish For any type of special finishes, it is recommended that you hire a concrete contractor that specializes in decorative concrete.
Step 4: Curing
Although curing is the most important step in this process, it’s probably the most neglected as well. Properly curing the concrete ensures that it reaches its maximum specified strength and will be able to withstand temperature differences and chemical exposure. Curing should start as soon as the concrete will accept the process without damage to the finish. Choose one of these good curing practices for your project. Wet curing In this process, the surface of the concrete is kept saturated. Typically, a garden sprinkler is used to keep the surface wet as the concrete hardens. Curing compound Using this method, a curing sealant is applied to the concrete surface. A paint roller or garden air sprayer is used to distribute the sealant to the concrete surface. Curing compound is available in our supply store.
- Water should not be added to the concrete during the finishing stage.
- Finishing techniques should not be started while bleed water is present.
- Over working the finished surface will ruin the internal air void system that is necessary for a good cure.
- Make sure that the concrete you are using for interior applications is made for interior projects.
- Concrete is made specific to it’s final purpose.
- Most importantly, don’t be afraid to ask questions. Feel free to call our dispatch or sales staff with any concrete question you may have.