Concrete polishers are not miracle workers. 

 

They cannot make cracked concrete flawless. 

They cannot make a sloped floor perfectly flat.

They cannot make a 50 year old floor brand new again.

 

They can repair the floor and grind down over many inconsistencies, therefore increasing the reflectivity and aesthetic value of the floor. 

 

Setting realistic expectations with the customer, then exceeding them, is always preferred over setting them too high and not delivering. The final quality of a polished concrete floor is largely dependent on the quality of the pour.  

 

On most projects, a polisher will first walk the floor to determine what work needs to be done prior to even submitting a bid. With new construction projects, walking the floor is not possible as it has not yet been poured. Only a mock-up slab is available for inspection, and it may not be a truly representative sample. When polishing will be completed as the finish on the concrete, the importance of quality flatwork is often overlooked, as it is frequently assumed that the concrete polisher will grind off any problem areas. This is a disadvantage to the polisher, as polishing is the final step of the slab construction, and the polisher should not be held responsible for faults he was not involved in. 

 

Setting expectations at the beginning of the project, with all involved, will eliminate many headaches, (and possibly thousands of dollars of loss) later on.  The best way for a polisher to do this is by staying involved in the preconstruction meetings. Preconstruction meetings are an excellent forum for educating owners and architects on the unique needs of a polisher, and for fostering communication and cooperation between contractors that is more difficult to ascertain after construction has commenced. 

 

There are numerous things a polisher should be prepared to discuss during the pre-construction meeting. One of the first, is that there is a need to protect the floor from damage throughout the construction process. Heavy objects dropped onto the floor during construction can gauge or chip the surface, leaving unslightly blemishes in the concrete and cost the client additional money to repair. Even chalk marks left on a wet concrete floor will seep into the surface and will be difficult to get out. 

 

Secondly, the polisher should be very clear about their flatwork needs. A polisher requires from the flatwork installers a reasonable assurance of uniformity of aggregate placement.  This is especially important to prevent “bowls”, which are caused during the pour when someone walks across the slab, creating low spots in the aggregate, then attempts to covers these areas with cement cream without aggregate. 

 

 

Though counter-intuitive, for cream jobs (a project which exposes no aggregate and polishes the cement at the very surface of the slab) aggregate placement is critical. The spec should require the flatwork installers to work the cement, possibly by vibrating the surface to settle the aggregates to the bottom of the slab, and floating a good layer of the cement, or cream, to the surface. Doing so will prevent the polisher from running into fine aggregates at the surface, and will result in a monolithic look across the slab.

 

Many clients who wish to utilize polished concrete are looking for a salt-and-pepper look. Salt-and-pepper, or small aggregate exposure, looks incredible, and often resembles granite or fine stone.   It is a challenge to offer a consistent fine aggregate finish, and requires the polisher to follow a thin line. They must grind deep enough into the surface to expose the small aggregates, but not deep enough to expose the tops of large stones. To do this, the cement pour must have enough fine aggregates in the mix and be worked well enough to bring those aggregates uniformly to the surface. Once again, bowls can be very problematic, as puddles of cream resemble footprints that can be traced across the polished slab. Even completely flat floors may have low areas that have had cream pulled over the top of them leaving color variations. 

 

Large aggregate exposure presents its own set of problems. A polisher is guaranteed that there is consistent large aggregate somewhere down in the slab, but the polisher must continue to grind deep into the floor to find it. The curing method used on the concrete, and any additives used within it, can make the concrete very difficult to cut. Simply wet-curing the concrete, without the use of cure and seals, will result in a dense surface that can be polished well.   

 

Having quality standards that everyone agrees to, and follows is very important. Flatness F-Number, or FFs, are the closest standard available to protect polishers. These are a standard set by the American Concrete Institute and defines the maximum curvature of the floor allowed over a 24” area computed on the basis of successive 12” sections. Levelness F-number, or FL is another standard that polishers may find useful. It defines the relative conformity of the concrete floor to a horizontal plane as measured over a 10’ distance. If the flatwork installer is held to the minimum FF/FLs, the polisher has a better chance that the slab has been prepared correctly for an optimal polish. The preferred FF/FL for polishing is 50/35.

 

Fostering a sense of cooperation between contractors will go a long way in resolving and preventing problems. Placing blame, even when it is there, will not often result in a successful correction of any situation. Understanding how problems effect the polishing job and focusing on the solution will arm polishers with the best course of action.

 

When you start fixing someone else’s problem, it becomes your problem.