Westinghouse Outdoor Power Equipment Electric Pressure Washer 1500 MAX PSI 1.5 GPM with Anti-Tipping Technology, ePX2000, Foam Cannon with Adjustable Spray
- 1500 max PSI of deep-cleaning water pressure and up to 1.5 GPM water flow - Adjustable spray wand with easy-coil nylon-braided 15' hose
- Super compact and lightweight at 14” tall and 15 lb. for convenient storage and portability - Four Quick-Lock wheels with 360° steering design and low center of gravity engineered for anti-tipping design
- Foaming soap cannon with 10 oz (300 mL) detachable bottle to add detergents/chemicals for versatile cleaning power on decks, driveways, garage floors, stairs, fencing, patio furniture, and vehicles
- Pump automatically stops when trigger is not engaged to conserve energy, prolong pump life, and added safety
- Backed by 3-Year Limited Manufacturer Service, Labor, and Parts Coverage
CLEANING CONCRETE SURFACES
Concrete stained surfaces can be cleaned, but to guarantee results you need to know the type of cleaning and the appropriate procedure in each case. To do this, nothing better than reading this article and others that will follow, as they contain everything there is to know on the subject.Cleaning should be done in a way that removes dirt without neglecting the concrete. The structure and color of the cleaned surfaces must not differ from the untreated surfaces. In principle, three cleaning methods can be used: 1
- mechanical procedures (scraping, rubbing, brushing, etc.);
- cleaning by washing (softening of the dirt and its elimination with water);
- dissolution cleaning (dissolution, absorption).
Sometimes all three methods are combined or used one after the other.
Stains on concrete surfaces
Soot, dust, sand, rubber particles, greasy materials, etc. are deposited on concrete surfaces. Lime efflorescence is also frequently added to newly finished concrete elements, rust stains, microorganisms, plants, as well as products of the reaction of cement paste with compounds in the air.
Initially, these deposits usually only damage the appearance of concrete elements, but do not directly reduce the functional capacity or durability of the same. Even certain layers of dirt are transformed into protective layers (patina). However, these crusts can also contain contaminating materials that damage the materials they cover. The faster a stain is removed, the greater the chances of success. Old stains can spread on the surface or penetrate deeply and are often solidly bound to the hardened cement paste, with which they sometimes react, with effects that make cleaning more difficult. On the other hand, it sometimes happens that mixtures are formed with the stains that were already in the concrete before,
Criteria for choosing cleaning methods
In general, the procedure should be chosen that allows the desired effect to be obtained by the least aggressive means, and that does not attack, or that attacks very little, the hardened cement paste. In addition, care must be taken that other elements that are in the vicinity and are made of wood, glass, aluminum or plastic material, as well as the gasket materials, can be protected if they are at risk of being attacked. It goes without saying that the people doing the cleaning should always be out of danger, as well as other people, plants or animals in the immediate environment. The evacuation of water, sand, dust, etc., coming from cleaning, must be carried out in accordance with the provisions of the legislation. Before using a procedure to solve a cleaning problem for the first time, it will be necessary to test in an inconspicuous place. In the case of a wet test, the effectiveness of the procedure cannot be judged until at least one week later.
Procedures based on the use of a combination of solvents or chemicals, or even both, are well known as a way to remove many types of stains on concrete surfaces. This will be covered in the next issue.
The following list shows different cleaning procedures in order of increasing efficiency and, for unidentified stains, it is advisable to use the first one that achieves the desired effect.
- Dry rubbing with a stiff brush
- Surface wetting, dry rubbing with a hard brush, low pressure water jet washing
- Cleaning with a high pressure water jet or steam
- Cleaning chemicals (for example, acids or bases)
- Sandblasting or other abrasive
- Torch cleaning
At least the last two of these procedures erode the concrete to a greater or lesser extent, generally requiring a coating to be applied immediately or other measures to be taken. Some of the main non-chemical procedures for cleaning concrete surfaces are listed in Table 1.
For delicate concrete surfaces it is advisable to use procedures whose degree of aggressiveness increases more slowly:
- Water with a soft brush
- Mild soapy water
- Strong soapy water
- Stronger soapy water and ammonia
- Stronger soapy water and vinegar
If that does not work, it will be necessary to resort to stronger products.
Wet cleaning
Cleaning with water is one of the procedures that mistreat concrete the least. It is effective only when the stains are only on the concrete surface and have been fixed there by water-soluble compounds, such as gypsum (CaSo4.2 H2O). (Gypsum results from the reaction of calcium hydroxide [Ca (OH) 2] coming out of the water contained in the pores of concrete, with the sulfur dioxide [SO2] contained in the air.)
Here, different degrees of cleaning are also possible:
- Cold water cleaning without pressure
- Cleaning with cold water under pressure
- Pressureless hot water cleaning
- Cleaning with very hot water (steam)
For cleaning with water under pressure, flat nozzles and special discharge systems are commercially available.5 High pressure water jets can also be used to remove thicker or thin layers of concrete. The cleaning effect of the different procedures can be improved by the addition of soap or other surfactants (surface agents), particularly for the removal of greasy surface stains. When water is not enough to remove softened staining matter, brushing is often indicated.
Mechanical and thermal cleaning procedures
There are numerous variants of mechanical cleaning procedures. All cause a more or less great loss of matter, which damages the surface, and it is the case that it remains in such a way that it suffers new stains. Generally used: 2.6
Cleaning by hand with
- brush or broom
- cellular glass
- water resistant sandpaper
Mechanical cleaning with
- circular brush
- strawberries
- corundum discs
Spray cleaning with
- sand
- wet sand
- grain
- jet of water under pressure
- jet of water under pressure combined with sand
- thermal cleaning
- blowing with special nozzle
Many small stains can be removed by simply scrubbing with a stiff non-metallic brush, fine pumice stone, or cellular glass. This type of rubbing can also serve as an auxiliary means for cleaning by the wet method. If done properly, this rubbing does not damage the concrete surface at all. However, do not use mechanical brushes (steel or brass), because fine metal particles can cause color changes.
Sand blasting 2, 3, 7 lends itself to the removal of numerous impurities that have not penetrated deeply into the hardened cement paste. This abrasive treatment pulverizes and removes dirt particles as well as some of the surface layer. Since there are many abrasives available (blast furnace slag, silicon carbide, quartz sand, walnut shells, etc.), you can choose the blasting method that damages the substrate as little as possible. The blasting, however, is little appreciated as a cleaning procedure because, despite all the precautions, the loss of material is inevitable, the surfaces become rough and, therefore, more exposed to the influence of the environment. Also, this procedure generates a lot of dust and noise,
Wet blasting is less aggressive than dry blasting.2, 3, 7 Although some of the same abrasives are used as for dry blasting, the surface stresses are lower, and less dust is produced. With thermal cleaning, using a special 2.6 torch with an oxyacetylene flame, the concrete surface is subjected to such stress that the upper area disintegrates and partially separates. Rubber particles, as well as oil stains and other organic compounds are well removed as they burn.
Chemical cleaning procedures in general
The specialized literature informs us of a great variety of chemical products that allow removing certain stains from the concrete surface. We can add products that exist in the market and that have been perfected for certain applications.
This variety can have its risks, and requires great prudence on the part of users, as well as protection of the people who apply them; improper use can cause irreversible damage. To avoid this, it is necessary to call specialists, or inquire well in specialized publications. Inexperienced employees must be carefully updated on their new assignment.
The effect produced by chemicals on stains can be very diverse. In general, acids chemically react similarly with the surface of concrete. Often times, alkaline products and surfactants do not dissolve stains but emulsify them, that is, they give them a shape that allows them to be washed away.6
For many uses of chemicals, the procedure is almost always the same: the surface is carefully moistened so that the chemicals applied quickly by spray or brush do not penetrate too deeply. It is immediately rinsed with plenty of water, after a reaction time that should be as short as possible. It may be necessary to repeat these operations several times.
Acidic cleaning products
En el momento de utilizar ácidos, es particularmente importante el humedecimiento previo del concreto, ya que la mayor parte de los ácidos reaccionan con la pasta de cemento endurecido. Por la misma razón, una vez que ha terminado la limpieza, es necesario enjuagar hasta que el agua de lavado sea casi neutra. Las pruebas de neutralización con atomizador de las soluciones alcalinas no son aconsejables, pues es imposible conseguir una dosificación precisa.3
The most frequently used acids are the following: muriatic acid, phosphoric acid, sulfuric acid, oxalic acid, acetic acid and formic acid.7 If necessary, it must be taken into account that muriatic acid and sulfuric acid cause the formation of ions of chloride or sulfate, which promote corrosion of concrete. For safety reasons, the use of hydrofluoric acid should not be used.3 Acids generally help to eliminate efflorescence. It is advisable to use dilute muriatic acid. The use of phosphoric or formic acid at 15 percent is also possible. The acid is sprayed on the previously moistened support, or spread regularly with a sponge or brush. After three to five minutes (end of foaming), rinsed thoroughly and eventually brushed with a stiff brush. In the case of strong efflorescence, it may be necessary to repeat this treatment.3 Working with acids involves several disadvantages. For example, the concrete surface becomes rough and of a darker tint, even if chemicals are used sparingly. Acid that has penetrated the concrete and is not washed off will eventually dissolve the ferruginous minerals, which can cause brown spots on the concrete surface. even if chemicals are used sparingly. Acid that has penetrated the concrete and is not washed off will eventually dissolve the ferruginous minerals, which can cause brown spots on the concrete surface. even if chemicals are used sparingly. Acid that has penetrated the concrete and is not washed off will eventually dissolve the ferruginous minerals, which can cause brown spots on the concrete surface.
Construction elements that cannot stand coming into contact with acid must be protected.
Alkaline cleaning products
Alkaline cleaning products - mainly sodium and potassium hydroxide - have the advantage over acidic products that they do not react, or react very slowly, with the compounds of the hardened paste. This advantage is negated by the fact that such products attack glass and aluminum, and that they force users to wear protective glasses and clothing. It is also necessary to collect and neutralize the wash water.
Alkalis are especially suitable for removing oil or greasy stains, since they saponify fats and neutralize fatty acids. The reaction products can be removed by rinsing with water.
Protection of people and the environment
It has been mentioned several times in the course of this article that man runs risks when using chemicals. Employees, above all, have only some knowledge of chemistry and should not handle chemicals unless they have received sufficient instruction and are adequately protected. And, as necessary, the environment must also be protected against the action of chemicals.
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