Masonry Magazine October 1994 Page. 24
Photo courtesy ProsoCo, Inc.
Apply cleaning solution to small sections of masonry with a stiff bristle brush. Prewetting and careful rinsing are key steps for successful cleaning when using a cleaning solution.
Pressure water cleaning should be used only with extreme caution. Too much water or too much pressure and water can saturate a wall causing efflorescence. Improper use of pressure water sprays can also damage the face of masonry units and erode mortar joints. When used in conjunction with a cleaning solution, the same preparation is required as with the bucket-and-brush cleaning procedure outlined previously. The masonry must be presoaked with clean water prior to application of the appropriate cleaning solution. The cleaning solution may be applied to the masonry surface under low pressure just sufficient to carry the solution to the face of the masonry. After the cleaning agent has been on the wall for about five minutes, the pressure water spray may be used to clean and rinse the wall. Nozzle pressures should be limited to less than 700 psi. Use a fan nozzle to produce a flat spray. Keep stream of high pressure water moving over the masonry surface. Angle spray to avoid hitting the surface of the masonry with a perpendicular stream of water.
Abrasive cleaning techniques include dry abrasive blasting and wet abrasive blasting. The abrasive material most often used is sand. While wet blasting tends to be less destructive than dry blasting, both methods function on the principle of cleaning the masonry by eroding the surface of the masonry. Neither is generally recommended for cleaning new masonry construction. For additional information on abrasive cleaning techniques and cleaning special stains see the references listed below.
References
1. Panarese, W.C., Kosmatka, S.H., and Randall, F.A., Jr., Concrete Masonry Handbook for Architects, Engineers, Builders, EB008M, Portland Cement Association, 1991, pp. 214-217.
2. "Removal of Stains from Concrete Masonry Walls," NCMA-TEK 45, National Concrete Masonry Association, Herndon, VA, 1972.
3. "Cleaning Brick Masonry," BIA Technical Note 20 Revised II, Brick Institute of America, Reston, VA, 1990.
4. "Removing Stains and Cleaning Concrete Surfaces," IS214, Portland Cement Association, 1988.
5. Clayford T. Grimm, "Cleaning Masonry-A Review of the Literature," University of Texas at Arlington Construction Research Center, Arlington TX, 1988.
CAUTION: Contact with wet (unhardened) concrete, mortar, cement, or cement mixtures can cause SKIN IRRITATION, SEVERE CHEMICAL BURNS, or SERIOUS EYE DAMAGE. Wear waterproof gloves, a long-sleeved shirt, full-length trousers, and proper eye protection when working with these materials. If you have to stand in wet concrete, use waterproof boots that are high enough to keep concrete from flowing into them. Wash wet concrete, mortar, cement, or cement mixtures from your skin immediately after contact. Indirect contact through clothing can be as serious as direct contact, so promptly rinse out wet concrete, mortar, cement, or cement mixtures from clothing. Seek immediate medical attention if you have persistent or severe discomfort.
This publication is intended SOLELY for use by PROFESSIONAL PERSONNEL who are competent to evaluate the significance and limitations of the information provided herein, and who will accept total responsibility for the application of this information. The Portland Cement Association DISCLAIMS any and all RESPONSIBILITY and LIABILITY for the accuracy of and the application of the information contained in this publication to the full extent permitted by law.
Portland Cement Association 5420 Old Orchard Road, Skokie, Illinois 60077-1083
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An organization of cement manufacturers to improve and extend the uses of portland cement and concrete through market development, engineering, research, education, and public affairs work.
24 MASONRY-SEPTEMBER/OCTOBER, 1994