The Importance of Cleaning Concrete
Concrete is among the most durable of all building materials that the construction industry uses. However, other materials can tarnish it.
Over the years I’ve been able to compile a list of some of the most common cleaning challenges that arise and solutions for them.
Soft drink, alcoholic beverage, tea, and coffee stains usually can be removed using hot water and soap. However, if the stains persist, a bandage can be applied with 4 parts water and 1 part glycerol (glycerin). You can also add two parts isopropyl alcohol to the mixture to speed the removal action up. Bleaches for removing smoke stains can be effective well at removing other stains including coffee. On tough stains, you can use a poultice of trichloroethylene and talc.
Airborne dirt may collect on a concrete surface and then form a dark and at times stains or oil buildup. A building that has architectural concrete might need to have air pollution deposits cleaned off in order to regain its original appearance. You can remove some dirt by scrubbing with water and detergent or around 20 parts water and 1 part hydrochloric acid. Special proprietary cleaners, however, are often preferred instead of hydrochloric acid solutions that can attract concrete.
You can use a solution of 3 parts water and 1 part phosphoric acid to scrub away moderate or light amounts of dirt with no or little corrosion. Proprietary cleaners that are made out of buffers and hydrochloric acid for protecting the concrete are used for removing serious dirt buildup. Another cleaning method is alkaline pre-wash and then followed up with an acetic acid wash. Special cleaning solutions may be designed especially for removing certain kinds of dirt.
The methods that are used for removing oil can be helpful to remove really oily dirt. Other effective methods include water blasting, light sandblasting, and steam cleaning.
After a surface is clean, it is a good idea to apply a clear-water repellent penetrating sealer (like siloxane or silane) or a breathable clear sealer (like an acrylic-based material or methacrylate) should be used for resisting the build-up of dirt and to make it easier to clean in the future. There are some cleaning specialists who prefer siloxane or silane treatments due to their high breathability (frequently with a vapor transmission of 95%).
You can remove most solidified epoxies from small areas to burn them off using a blowtorch. It is important to provide adequate ventilation since it will emit black acrid smoke. If there is a remaining black stain, it can be treated in the same way as smoke stains. For large areas, it is more appropriate to use abrasive blasting.
Since greasing doesn’t penetrate concrete usually scrubbing and scraping will remove it. Scrape all of the excess grease off of the surface and then scrub with detergent, trisodium phosphate or scouring powder. If the staining persists, you will need to use a method that involves solvents.
To create a stiff poultice, use a chlorinated hydrocarbon solvent like trichloroethylene or mineral spirits (naptha solvent). Apply it to the stain and leave it on until the paste has dried thoroughly. Repeat this application as frequently as needed. If necessary, scrub using proprietary cleaners that are specially formulated to remove grease from concrete, trisodium phosphate, scouring powder or strong sap. Use clear water to rinse.
For larger areas, like a whole floor, use a metasilicate, butyl cellosolve (with adequate ventilation) or another alkaline floor cleaner in order to emulsify the oil and grease on the slab surface. It will usually require brush scrubbing. Before the emulsion breaks down or the cleaning solution dries, flood rinse using water after you finish scrubbing. Other solvents that you can use to remove grease include chloroform, carbon tetrachloride, and sodium carbonate.
*Warning: Do not make a poultice using trichloroethylene since it reacts with strong alkali’s like fresh concrete or cement which results in dangerous gases being formed.
Make a solution of 3 quarts of water, 1 quart of commercial laundry bleach, 3 ounces of trisodium phosphate, and 1 ounce of commercial laundry detergent. Apply this mixture to the area using a soft brush. Use clear water to rinse.
When exterior concrete surfaces do not have any exposure to sunlight and are in damp conditions constantly, they might have signs of moss or other plant growth. You can successfully remove those growths by applying ammonium sulfamate (which is marketed under different brand names and can be purchased at a garden supply store). You should carry out this treatment according to the package directions. If an unsightly powdery deposit remains on the surface, you can wash it off with water.
You can also use a solution of 8 parts water and 1 part sodium pentachlorophenate. Apply to the moss or other plant growth so that it is thoroughly saturated. If rain exposes the surfaced within 24 hours of the application, part of the solution will become lost and it might be necessary to do a further application. Around one week after applying the pentachlorophenate solution, it should have killed all of the vegetation growth and you can brush away any remaining residue. Usually, the surface will retain enough weed killer so that further growth is inhibited for quite some time.
Other chemical solutions you can use include copper sulfate – 5 ounces to 1 gallon of water, copper nitrate, formaldehyde (49 parts of water to 1 part formaldehyde), or sodium hypochlorite (laundry bleach). Just boiling water can be used as well.
For best results, seal the surface after brushing off any dead moss and dirt. There are various transparent sealers or paints that are available commercially for this kind of application. An effective sealer might contain a 1% ammonium chloride as the coagulator and a 33% sodium silicate within water. The sealer allows you to easily wash off growth but does not prevent it from forming. Other sealers can also be helpful, including zinc fluosilicate in 1-gallon of water or 7 ounces of magnesium fluosilicate.
The simple methods below can be used to remove oil stains effectively from parking lots and driveways.
Method 1: Use paint thinner or mineral spirits to saturate the area. Cover using an absorbent material like corn starch, corn meal, Fuller’s earth, cat litter, talc, or dry Portland cement. Allow it to stand overnight and then sweep the covering away. Repeat if needed.
Method 2: If an oil stain is not removed by Method 1 scrub using a trisodium phosphate solution.
Method 3: Use a laundry bleach to bleach the surface.
There are many commercial products that are well-suited for removing felt tip marketing and spray-paint off of concrete surfaces. Usually, the products are also effects for removing lipstick, chalk, and crayon. Always follow the manufacturer’s directions. If you do not obtain satisfactory results with your first application, you should make a second or third attempt using other products. The same product might not remove both felt tip stains and spray paint.
You can use methylene chloride if there are not proprietary cleaners available. Wear protective clothing and brush methylene chloride on the surface. Allow it to sit for two minutes and rinse using water as you continuously brush. Hydrogen peroxide or oxalic acid may be used for helping to bleach some pigment out of the concrete pours. Other helpful solutions for removing graffiti include methyl ethyl ketone, xylene, or sodium hydroxide. Other effective cleanings can be done with sandblasting and water blasting.
After removing the graffiti, or before placing the structure back in service preferably, you should apply an anti-graffiti sealer or coating. Treating the surface should help to prevent graffiti from penetrating into the concrete’s pores and help to facilitate removing graffiti, hopeful without taking away the surface treatment.
Aliphatic urethanes are thought to be the best anti-graffiti coatings due to their resistance to abrasion, yellowing, and solvents. Solvents like methyl ethyl ketone and mineral spirits can remove a majority of graffiti off of aliphatic polyurethane without the urethane coating being compromised. Siloxanes, silanes, epoxies, and acrylics can be used as well to make it easier to remove graffiti. Epoxies tend to discolor or yellow and acrylics dissolve with solvent. Siloxanes and silanes might not resist some graffiti material or urethane. However, they resist graffiti penetrating into the concrete and maintain high breathability on the surface of the concrete.
There are stains that vary in intensity from brown to light yellow that can occur sometimes on terrazzo floors and interior concrete due to subsequent cleaning or the original finishing. Usually, it is not difficult to remove these discolorations. It is possible to bring back the surface to its original appearance when you apply a poultice containing Javelle water (sodium hypochlorite solution) or using Javelle water to scrub the surface.
Other stains not discussed here can be removed by trying out various solvents or bleaches in an inconspicuous area. You should always thoroughly scrub the treated area using clear water following your treatment so that there are no removing agent traces remaining.
You can protect coloured concrete using the following tips for easy care.
These help to protect concrete against damage from freeze-thaw cycles and de-icing agents, while also repelling water, grease, oil, and repelling oil stains. Use a quality sealer to seal the concrete. It is critical that the sealer is applied during the first after placing the concrete and before the first frost occurs. Schedule a regular resealing program to take place every one or two years.
In order to prevent dirt from gradually accumulating, get periodic cleaning schedule. the most effective cleaning method for coloured concrete is low pressure, chemical-free power washing.
Removing Ice and Snow
– Do not chip ice on concrete surfaces
– Avoid using de-icing salts
– Use a plastic snow shovel to remove ice and snow