6.1 Early trafficking and cleaning
If the pavement has unbound joints traffic may use the pavement immediately following the final pass of the vibrating plate compactor.
At this stage the joints between the pavers will be relatively porous.
Cleaning should be by hand broom only for this period. Cleaning with hoses or mechanical sweepers with vacuum attachments is not recommended during the first 3 months.
Following the ingress of water, together with general dirt and detritus, the jointing sand will consolidate and become relatively impervious.

6.2 Basic cleaning principles

6.2.1 General
Clay paving provides a durable and hard wearing surface, but like any other paving material, may suffer from staining. Frequent sweeping and washing reduces the effect of dirt and grime and maintains the attractiveness of a pavement. The removal of stains need not be a problem if the following principles and procedures are followed.

6.2.2 Select correct cleaning solutions
Is the use of chemicals necessary?
If clean water and a detergent fail to work then the answer could be yes. Do not automatically reach for an acid cleaner, establish what the contaminant is.

6.3 Removing common stains

6.3.1 Efflorescence
The majority of clay pavers have a low soluble salt content and a slight white bloom may appear on the surface immediately after laying. The source of this stain is most likely to be derived from the jointing sand.
These salt deposits are usually harmless and can be removed by dry brushing and allowing to weather away naturally.

Efflorescence may also manifest itself when pavers start to dry out following the seasonal use of de-icing salts, particularly in town centre pedestrian areas. Normal weathering will remove this discolouration. Special urea based gritting salts are available to minimise this problem.

6.3.2 White scummming
This is often seen as a thin white film on the paving surface if there is contamination from an external source, e.g. concrete structures discharging their run off, or even the leaching of certain limestone sub bases. It may also appear after an attempted removal of mortar stains or after the sanding of joints with ‘clayey’ sand (i.e. sand contaminated with clay content).

6.3.3 General dirt and grime
Frequent sweeping and hosing will usually ensure a clean pavement. If this is not enough then washing with a detergent may be required. Any use of pressure washing may require the replacement of jointing sand.

6.3.4 Vanadium stains
Buff or fireclay products in particular often contain vanadium salt that may appear as a yellow, green or red/brown discolouration of the pavers. Vanadium stains are naturally occurring and are neither permanent nor harmful and do not indicate any defect in the paver. Stains in exposed areas generally wash of in time but their removal can be hastened by chemical treatment. Refer to Design Services.

6.3.5 Mortar stains
Experiment on a small section of the affected pavement with a weak solution of water mixed with hydrochloric acid. Once the appropriate strength of solution has been determined then follow the manufacturer’s instructions in the removal of the stain. Clean area down with clean water once stain is removed.

6.3.6 Fungi, moulds, moss and lichens
These are common, particularly in shady or damp parts of the pavement. They will not damage the pavement but may cause it to become slippery. Remove by vigorously brushing the effected area when it is dry. Alternatively high pressure water may be used.
It is necessary to ‘sterilise’ the area with a strong fungicide/weed killer or proprietary brands from garden centres. Follow manufacturer’s instructions and test their effect on a small area initially.

6.3.7 Oil, bitumen, tar
Oil does not penetrate into the body of clay pavers and will sit on the surface until it is dispersed naturally.
Scrape off any excess material when dealing with petroleum asphalt and bitumen or mop up immediately any petrol or oil stains using absorbent paper towels. Wiping and further spreading of the contaminants should be avoided.
Treat with commercial emulsifying agents, such as ‘Gunk’, following manufacturer’s instructions. Subsequently, use detergent to clean up and rinse well with clean water.
Neither hot water, nor steam, nor emulsifying agents will affect the colour of the paving.

6.3.8 Food stains and tyre marks
Scrub with full strength commercial detergent and rinse well.

 6.3.9 Chewing gum
The most serious of cleaning problem associated with town centre and public realm projects is chewing gum.
Wire brushes should remove the majority of chewing gum but it will require several attempts. Specialised high-pressure water jet lances and freezing methods have also been successful in varying degrees.

6.3.10 Paint and graffiti
Very difficult to remove.
Soak up any wet paint with an absorbent material. Do not wipe as this will spread the paint. Treat with white spirit solvent followed by washing down of the area with a strong detergent and hot water/steam.
Dried paint should be scraped off and an appropriate paint stripper applied following manufacturer’s recommendations. Wash the area down with a strong detergent and hot water/steam.
Alternatively, consult a specialist company should the affected area be large or as a result of vandalism.

Should all else fail, take up the affected area, turn the pavers over and re-lay.