| Concrete |
| What are preexisting conditions that are beyond my control? |
We did not pour the concrete slab and had nothing to do with leveling or toweling the slab. That was the job of the concrete contractor! In addition, we did not mix the cement and do not know what was put into it. There is real chemistry in concrete. It is more than cement, rock, sand, etc. mixed together. There are two issues with grinding concrete. One issue is actually desirable depending on the desired look you are trying to achieve. No one that I know of can see into the concrete and see where the aggregate lies. The aggregate may be spread evenly, close to the surface or deep in the slab. If imperfections have to be ground out in most cases the aggregate will become exposed. Sometimes normal grinding may also expose aggregate and there is nothing that can be done about it. If you have imperfections in the floor and you do not want exposed aggregate then your floor may not be a candidate for “true” concrete polishing or the imperfections will have to be left. Slabs over 50 years old in particular and some younger can have a problem that is a result of excessive microporosity and deterioration of the cement binder. This happens on older concrete before plasticizers were available or on newer concrete when plasticizers were not used. Plasticizers increase the concretes workability making the concrete easier to work with using less water. When plasticizers are not used more water is added to make the concrete more workable. When a lot of water is used more of it has to travel to the surface (bleed water) and it creates excessive micropores. As the floor is polished areas of the cement binder can come out because of the excessive porosity. Since it is impossible to polish a void what is left is an effect called various names such as Swiss cheese, eggshell, speckled or orange peel. These voids can vary in size as small as the point of a pin. This issue may not be realized to the fullest extent until the “polishing” process begins. Again, this is a preexisting condition that is not always predictable because it may be hidden just below the surface.
If the concrete has/had a covering or coating on it and it did not allow for vapor transmission the concrete underneath could be deteriorated. This is more likely in a situation where there have been passed moisture issues. Concrete exposed to these conditions have a problem that is a result of excessive microporosity and deterioration of the cement binder. This is considered a preexisting condition and may not be detectable until the covering or coating has been removed. If for example, a tile was on the floor the area under the tile towards the center in most cases will have the most damage as a result of the moisture not being able to escape out from under it. These areas are much softer and more porous. When polishing the floor these areas may end up with a different polish then the rest of the floor. Again, this is a preexisting condition.
If there has been glue, mastic, etc. on the floor from carpet, tile, wood or for any other reason these products can go down into the concrete. Often the results of these products being on or in the concrete do not show up until the floor has been polished.
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