SOLUTIONS

What is wrong with Concrete ??? Concrete is susceptible to a number of problems Concrete is porous Gasoline, grease, oil, chemicals, dirt and even water will enter the pores and stain, spot, unhygiene and/or discolor. Concrete can wear The abrasion of continuous traffic or equipment movement can lead to erosion of the surface and create unevenness. Concrete can be damaged Impact from a sudden blow or a heavy load can crack or break concrete. Concrete can trap odors In some environments, bacteria can invade the floor causing permanent odors and health hazards. Concrete can create environmental and safety hazards Chemicals can penetrate the concrete and contaminate the surrounding soils Causes for Problems : REACTIVE AGGREGATES AND SOILS Aggregates consist of sand, gravel or crushed stone, and they are used in a variety of construction projects. Some earth materials, when used as concrete aggregates, react with the Portland cement through expansive reactions that cause accelerated aging and premature failure of the resulting concrete. Such materials are called "Reactive Aggregates". Reactive minerals that commonly find their way into aggregates include clay minerals. Clays hidden within dolo-stones (rocks, composed primarily of the mineral dolomite; calcium-magnesium carbonate), or within limestone (rocks composed primarily of the mineral calcite-calcium carbonate) can be troublesome. Other reactive minerals are "sulfates and nitrates" or "micas" (layered silicate minerals), some "feldspars" (alumina-silicate minerals), "opal" (hydrated silica), "chert" (a very fine grained mixture of quartz and opal) and "pyrite" and "marcasite" (iron sulfides). Natural non-crystalline substances that occasionally produce expansive reactions include "volcanic glasses" and "diatomaceous earth" (an earth material that consists of the silica shells of one-celled algae called diatoms). Ignorance about the nature of the aggregate produces expensive mistakes in construction of short-lived highways, bridges and sidewalks. When reactive materials are known to be present, special additives can be placed in the concrete mixture to insure longer life but usually with side effects (softening of concrete). POROSITY Porosity can be defined as, "Being full of pores, or tiny holes, through which fluids, air, or light may pass." Normally, concrete is a mixture of four basic ingredients: sand, gravel, cement, and water. In the mixing process, as certain amount of air is mixed into the concrete. The water and air take up space inside the concrete even after the concrete is poured in place and during the early stage of setting. When the concrete is "worked" in place and begins to polymerize, the heavier ingredients have a tendency to settle to the bottom and the lighter ingredients have a tendency to float to the top. Water being the lightest of the four basic ingredients, floats to the top and is evaporated away, or is squeezed out the sides or bottom. As the water is squeezed out, it moves in all directions. Water, being a solid in that it takes up space, leaves millions of small rivulets and pores crisscrossed in all directions. As the air escapes, it has the same effect. These small rivulets or hollow spaces tie together creating what we call "Pores" Quite often the pores create hairline cracks inside the concrete, weakening the concrete. As the capillary action of the concrete draws water up into the concrete, or rain hits the side of a concrete wall, or water hydrology bears against a concrete basement wall, the water travels via these pores through the concrete. The pores are interwoven and interconnected, thus allowing a slow seepage of water through the concrete. The denser the concrete, the tighter the pores, and less water is allowed to pass through. WALL SWEATING It should be remembered that the surfaces of most common masonry building materials have an affinity for water molecules. The water molecular film is proportionate to the relative humidity. At the saturation point all voids , pores , and capillaries become completely filled. Then, when the atmospheric condition, inside or outside, which caused the excess of moisture in the first place is not alleviated, the porous wall may be filled to saturation point with moisture in liquid form. This condition then provides an excellent opportunity for vapor travel within a wall. The vapor may strike a cold area or dew point, and condense in sufficient quantities to reach the interior wall surface and appear as "wall sweat or bleeding" Each of the above, if allowed to go unchecked, can be responsible for heavy maintenance costs by causing peeling paint, formation of mildew, and efflorescence. All porous masonry wall materials do the same thing, unless proper steps are taken to avoid it. FAILURE OF FLOOR COVERING & PAINTS Floor covering failures are caused by one, or a combination of, the following: moisture, alkali, oils, contaminants or hydrostatic pressure. To apply asphalt, vinyl, rubber, tile, etc., 3 items are necessary-- a floor (usually concrete), adhesive, and covering. We now know the make up of concrete and the problems built into it, in the form of alkali, lime, and moisture. Another important fact is needed, that is porosity. The slab of concrete acts as a sponge and draws moisture from the ground. The moisture passes through these voids and mixes with the ever present alkali. When this alkali moisture is drawn to the surface of the slab, it comes in contact with the adhesive. When alkaline water meets the adhesive it emulsifies and commences to deteriorate the adhesive. The end result to the floor covering is alkali bubbles and blisters, usually followed by warping, cracking, and peeling of the floor covering which necessitates replacing the covering. Paints blister and crack on masonry surfaces because of saponification. When soap is manufactured the basic ingredients are a form of alkali and oil. The combination of the alkali in the masonry and the oil in the paint cause the saponification, which results in flaking, blistering, bleeding, and burning off the paint from the surface. Vinyl, rubber, or latex-based paints are in wide spread use today. These, as well as oil based paints, peel and crack off masonry surfaces. The prime reason for this is that the alkali and lime are fighting the paint. In the event that these surface coatings are used as a sealer or waterproofing agent, they must be applied and periodically reapplied so that the coatings are 3 to 6 layers on the surface. These procedures are harmful to masonry and provide only temporary relief. ACID / ALKALI DISINTEGRATION Concrete is a mixture of Portland cement, sand, gravel and water. But, the simplicity ends there. Concrete, whether it be slabs, blocks, walls, roofs, piers, beams, pipe, etc., is extremely vulnerable to the industrial society. Sulfuric acid is one of the most commonly used chemicals in the industry, yet it is one of the most damaging to concrete. It is used in the manufacturing of dyes, paints, explosives, fertilizers, to demineralize water in power plants and many other such common industrial applications. It is constantly being spilled on our concrete, unknowingly forming other acids, or being atomized into our atmosphere. Our automobiles spread sulfuric acid onto our roads and into the atmosphere. Our sewage systems produce hydrogen sulfide, which when mixed with water also form sulfuric acid, to disintegrate the concrete pipe and lift stations. We have hydrochloric acid, nitric acid, and carbonic acid which when mixed with water form other acids that are concrete killers. So, you can see that our industrial society and community waste systems constantly provide the setting for the formation of concrete disintegrating compounds. Alkali can be defined as any base or hydride, such as soda, potash, etc. that is soluble in water, and can neutralize acids. If acids disintegrate concrete, then alkalis should protect it. But, not so. Sodium hydroxide; also known as sodium hydrate, caustic soda and lye; is commonly used in oil refineries, paper manufacturers, paints, plastics, soaps, and many other common products. This caustic soda, being on the other end of the pH value scale from acids also will disintegrate concrete. PLASTICIZER MIGRATION One of the major problems facing the floor covering industry is plasticizer migration. That is, the movement of substance from one product into another product, so as to create a product deterioration. This product deterioration can take many forms such as: softening, cracking, blistering, peeling , de-lamination, loss of strength, etc. Today, many floor coverings are laid on a concrete base. The owner has 2 (two) options. First, lay the floor covering on the bare concrete. Or second, seal the concrete before laying the floor covering. Let's examine these 2 options. First. If the floor covering is laid on bare concrete, there may be a migration of the alkali, other salts or any foreign material down inside the concrete, such as oil, which may attack the adhesive or the floor coverings directly. Subsurface oils may take months to show up at the surface, to attack or discolor the floor covering. Second. If the concrete is sealed conventionaly, another set of detrimental factors may start to emerge. The concrete sealants used today are cementitious membranes or oil-based paints. There is a good possibility of a plasticizer migration directly from these surface sealants to the adhesive or floor covering. Also, the alkali or pollutants in the concrete will cause saponification, eventual disintegration or release of the surface which brings on long range problems and excessive costs.

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