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Working Together for Optimal Results

 

Here is an overview of some of the key issues each contractor should be held accountable for on a polishing project. The purpose of this list is not to hang anyone out to dry if something goes wrong, but rather to let all parties know what is expected of them and that they need to strictly adhere to the project specifications to avoid potential problems.

It's imperative that everyone involved in a polished concrete project knows what to expect of the end product and the process of achieving it. There are many caveats to polished concrete that can affect its finished look which may or may not make a client's requests realistic. The condition of the substrate, areas in need of repair or patching, aggregate exposure, cracks, chips, and divots, color sampling, and more should be discussed in detail with all parties to ensure understanding of the polishing process.

 

Placing and Finishing contractor 

  • Determining how the concrete will be delivered. Should it be tailgated (poured directly out of the truck) or pumped?

  • Protecting the fresh concrete under extreme conditions. If the concrete can potentially freeze, measures should be taken to keep the air warm inside the building when the trucks enter and exit, such as by setting up temporary tented rooms with large flaps that open and close.

  • Checking that jobsite water (water of convenience) is only added one time to the concrete by a preapproved person, per the specification requirement.

  • Verifying that the inside ambient temperature of the building is a minimum of 55° F.

  • Installing the concrete at the specified thickness and then laser screeding and finishing the surface to ensure that the floor meets the specified flatness and levelness requirements.

  • Cutting contraction joints in the slab at the specified depth and spacing, using an early-entry saw that won't mar the surface and then removing any residual dust.

  • Making provisions to properly cure the slab. Should the slab be wet cured or should a sacrificial liquid membrane be applied? Wet curing is not always practical because it can take much longer for the slab to reach acceptable moisture-vapor readings.

 

Independent testing firm

  • Monitoring the subgrade to make sure the loaded concrete trucks are not creating ruts deeper than ½ inch.

  • Testing the concrete in the first truck for slump, temperature, air content, and unit weight and then checking roughly every fifth to tenth truck thereafter. Test cylinders should also be taken.

  • Verifying that the concrete was placed and finished to the specified floor flatness (FF) and levelness (FL) tolerances.

 

General contractor

  • Checking the vapor barrier and reinforcing steel before concrete delivery. Are all the seams in the vapor barrier properly sealed? Is the rebar consistently tied on 18-inch centers and uniformly lifted and chaired in position in the middle of the slab?

  • Making sure that when the concrete truck backs over the steel, it is not bent and the vapor barrier is not punctured.

  • Checking isolation joints to ensure that all steel columns are wrapped with closed-cell foam and there is no concrete-to-steel contact.

  • Checking construction joints to confirm that ¼-inch plate dowels are located exactly middepth of the slab on 24-inch centers.

 

Polishing subcontractor

  • Performing a mockup once the concrete slab has cured sufficiently so the owner or owner's agent can sign off on the dye/stain color, the quality of the finish, the color of the joint filler, the topical protective treatment, and the degree of shine. (This should be done roughly 30 days after concrete placement and after the HVAC system has been operating for a minimum of 14 days.)

  • Filling the joints with the approved filler material.

  • If areas need repair from poor finishing or damage during construction, using the appropriate repair material that matches the color of dye or stain to be used.

  • Taking gloss meter readings to make sure the concrete meets the specified minimum gloss requirements after polishing.

 

Other building trades

  • During the remaining construction, making sure all equipment on the floor is equipped with nonmarking tires and is diapered to prevent oil and hydraulic stains.

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