For most jobs, cleaning should be handled by a professional company experienced in the use of cleaners and spray equipment. Professionals typically use a pressure washer and an applicator to apply efflorescence cleaner (when needed). The various methods for applying joint sand stabilizers and sealers are covered later. A high pressure sprayer applies cleaner and water between 600 and 2,000 psi (4.1 and 13.8 MPa), and at a rate between 6 and 12 gallons/minute (22 and 45 liters/minute). The rate of flow is adjusted to ensure sufficient rinsing. The pressure loosens dirt and pushes water from the surface without the need for scrub brushes. The nozzle type and its distance from the paver surface influences the effectiveness of the cleaning as well. A nozzle that creates a wide spray enables a large area to be covered efficiently and prevents sand from being washed from the joints. A low angle of attack from a wide nozzle spray will also reduce the risk of dislodging joint sand. Cleaners to remove efflorescence are applied with a low pressure pump spray 30 to 100 psi (0.2 to 0.7 MPa). A shower type spray nozzle will help ensure even distribution of the cleaner. Cleaning chemicals are applied, allowed to sit an appropriate time, then rinsed away with a high pressure sprayer. The final rinse should be water only. A large amount of water is more important to rinsing than high pressure. For small areas, an adequate cleaning job can be achieved without this equipment. Such areas include residential patios, walks, or small driveways. Cleaners can be applied by hand, the pavers scrubbed to remove dirt and efflorescence, then thoroughly rinsed with water from a garden hose. Scrub brushes with steel bristles are not recommended. They will loosen from the brush, rust, and leave stains. Brass or plastic bristles are acceptable. This method of cleaning is for do-it-yourselfers who wish to refurbish a small area of pavers. The additional time required to clean and seal pavers without the help of a professional should be weighed against investing in a competent company to do the job. Professionals have the equipment and experience with the various chemicals. They can achieve the highest level of results in the least amount of time. We always advise contacting a local professional. Please contact a local distributor for companies that specialize in cleaning and sealing paving stones. For more information, please refer to theICPI Tech Spec 5 - Cleaning, Sealing and Joint Sand Stabilization of Interlocking Concrete Pavement

Commercial stain removers available specifically for concrete pavers provide a high degree of certainty in removing stains. Many kinds of stains can be removed while minimizing the risk of discoloring or damaging the pavers. The container label often provides a list of stains that can be removed. If there are questions, the supplier should be contacted for help with determining the effectiveness of the chemical in removing specific stains. Identify the stains prior to applying the cleaner. A test application should be evaluated in a small, inconspicuous stained area for cleaning effectiveness. stains may require repeated applications of the remover to achieve effective cleaning. This is often the case for deep set oil stains. With all stain removers, cleaners, joint sand stabilizers, and sealers, the label directions and warnings should be read and carefully followed for all precautions. Start removal of stains at the bottom of the pavement and work up the slope in manageable sections. By working up the slope, cleaning fluids will drain down the pavement. This technique assists in uniform removal while allowing the used cleaner to be rinsed away consistently. The surface remains dry ahead of the cleaner-soaked wet areas, allowing better visibility of the stains to be removed. Take care in selecting and applying cleaning products, as acidic ones may harm vegetation and grass. These cleaners should not run onto vegetation. When using strong acidic stain removers or cleaners that might drain onto vegetation, saturate the vegetation with water prior to using acidic cleaners. This will minimize absorption of cleaner rinse water and reduce risk of damage to vegetation. We always advise contacting a local professional. Please contact a local distributor for companies that specialize in cleaning and sealing paving stones. For more information, please refer to the ICPI Tech Spec 5 - Cleaning, Sealing and Joint Sand Stabilization of Interlocking Concrete Pavement

Efflorescence is a whitish deposit which can appear on concrete products. When cement hydrates (hardens after adding water), a significant amount of calcium hydroxide is formed. The calcium hydroxide is soluble in water and migrates by capillary action to the surface of the concrete. A reaction occurs between the calcium hydroxide and carbon dioxide (from the air) to form calcium carbonate, then called efflorescence. Efflorescence does not affect the structural performance or durability of concrete pavers. The reaction that takes place is the formation of water soluble calcium bicarbonate from calcium carbonate, carbon dioxide and water. It may appear immediately or within months following installation. Efflorescence may reach its peak in as short as 60 days after installation. It may remain for months and some of it may wear away. If installation takes place during dry period of the year, the next cycle of wet weather may sometimes be necessary for efflorescence to materialize. If there is a need to remove deposits before they wear away, best results can be obtained by using a proprietary efflorescence remover. The acid in proprietary cleaning chemicals is buffered and blended with other chemicals to provide effective cleaning without damage to the paver surface. Always refer to the paver supplier or chemical company supplying the chemicals for recommendations on proper dilution and application of chemicals for removal of efflorescence. They are generally applied in sections beginning at the top of slope of the pavement. If the area is large, a sprayer is an efficient means to apply the cleaner. The chemicals are scrubbed on the surface, then rinsed away. Results can be verified after letting the area dry for at least 24 hours. In most instances one application is sufficient. However, in severe instances of efflorescence, a second application may be necessary. Contact the manufacturer of the cleaning product to determine if a second application will not discolor the pavers or expose some aggregates. Note: Protective clothing, chemical resistant rubber boots and gloves, and eye goggles should be worn when applying acid or alkalies. For more information, please refer to the ICPI Tech Spec 5 - Cleaning, Sealing and Joint Sand Stabilization of Interlocking Concrete Pavement

Scrub black area with water, detergent and scouring powder. In the case of small stained areas, removal and replacement with new pavers may be an option. For more information, please refer to the ICPI Tech Spec 5 - Cleaning, Sealing and Joint Sand Stabilization of Interlocking Concrete Pavement

Mop up any excess oil with rags. Cover the area with oil absorbent (kitty litter). Talc, fuller’s earth, diatomaceous earth can be used. Leave it on the stain for a day then sweep up. For more information, please refer to the ICPI Tech Spec 5 - Cleaning, Sealing and Joint Sand Stabilization of Interlocking Concrete Pavement

During the course of normal use, the sand-filled joints receive dirt from traffic on the pavement. Dirt settles into the top of the joints, helping to hold the sand in place. Installations exposed to driving winds or runoff, however, may lose some joint sand that can be simply replenished with dry sand. Weeds can germinate between pavers from windblown seeds lodged in the joints. They don’t grow from the bedding sand, base or soil. Weeds can be removed by hand or with herbicides. Take care in using herbicides so that adjacent vegetated areas are not damaged. Use biodegradable products that won’t damage other vegetation or pollute water supplies when washed from the pavement surface. For more information, please refer to the ICPI Tech Spec 5—Cleaning, Sealing and Joint Stabilization of Interlocking Concrete Pavement.

Most paver producers add chemicals to the concrete that reduces the likelihood of efflorescence occurring. In most cases, the additives prevent efflorescence. However, completely eliminating the chance of efflorescence isn’t possible because it’s a natural byproduct of hardened concrete. Efflorescence is a white haze that may appear on the surface of pavers sometime after installation. It forms as a result of a natural chemical reaction that occurs when the lime or water soluble calcium oxide produced by the cement contained in the pavers reacts with water. When the water enters the microscopic capillaries in the pavers where calcium hydroxide is formed. The calcium hydroxide rises to the surface of the paver, reacts with the carbon dioxide in the air, and forms a white haze of calcium carbonate when the moisture on the surface of the pavers evaporates. The appearance of efflorescence will stop when there isn’t any more calcium hydroxide available to move to the surface. Since efflorescence brings out salts that are not ordinarily part of the paver, it is not a structural, but, rather, an aesthetic concern. The white haze may give the impression that the color of the pavers is fading but this is not the case. Efflorescence may occur randomly or be concentrated in certain areas. Dark colored pavers show efflorescence more than lighter-colored ones. If efflorescence does occur, it can be removed with cleaners specially made for concrete pavers. Careless or improper cleaning can result in damage and discoloration to the concrete paver surfaces. Contact your paver supplier for further information about the chemistry of efflorescence and appropriate commercially available cleaners. For more information, please refer to the ICPI Tech Spec 5—Cleaning, Sealing and Joint Stabilization of Interlocking Concrete Pavement.

Settlement is often caused by inadequate soil or base compaction. Other factors can be water in the base or soil, too thick a layer of bedding sand, or washed out bedding and joint sand. Loose or inadequate edge restraints will cause pavers to move apart. Pavers in uneven areas can be removed, the settlement adjusted, and the units reinstated with no wasted paving materials or unsightly patches. If the base or soil has settled and is stable, remove the pavers and bedding sand, place and compact additional base material to the correct level, then add bedding sand. Bedding sand alone shouldn’t be applied to adjust the level of the surface if its thickness exceeds 11/2 in. (40 mm). Concrete pavers can be removed for access to underground utilities, and reinstated after repairs. When utility repairs are complete, fill the trench with base material and compact it. Remove about 18 in. (0.5 m) of pavers on either side of the opening, level the bedding sand and replenish as necessary. Reinstate the pavers, compact, fill the joints with sand and compact the surface again, filling joints as needed. For more information, please refer to the ICPI Tech Spec 6— Reinstatement of Interlocking Concrete Pavements. It provides step-by-step guidelines on removal and replacement of concrete pavers.

Concrete pavers on driveways stained by oil leaking from cars aren’t damaged by petroleum products, but the stains can be difficult to remove. Stains should be treated as soon as possible since the longer they remain on the surface, the deeper they penetrate and the harder they are to remove. Wipe excess oil from the surface as soon as possible and apply liquid detergent. Allow it to soak for several minutes. Then wash the pavers with hot water. Several treatments may be necessary for particularly stubborn stains. Cleaners specially made for removing oil stains from concrete pavers are recommended since they yield good results. In some cases, it may be simpler to replace the stained pavers with new ones. Removing oil and many other stains are discussed in ICPI Tech Spec 5- Cleaning and Sealing Interlocking Concrete Pavement. Cleaning and sealing concrete pavers early in their life can make removing stains easier since sealers prevent stains from soaking into the surface. However, the sealers may need to be reapplied from time to time due to wear and weather. Concrete pavers should be cleaned prior to applying a sealer to obtain the best performance and appearance. Your paver source can provide information on cleaners and sealers specifically made for concrete pavers. For more information, please refer to the ICPI Tech Spec 5—Cleaning, Sealing and Joint Stabilization of Interlocking Concrete Pavement.