The history of segmental paving relates largely with urban streets. In medieval times the streets served as sewers as well as for a source of access. These streets lead to a need to be paved as well as to facilitate drainage, to enable pedestrian and vehicle movements. The design and construction of these pavements required skill to ensure that proper drainage and sustainability of these areas are achieved. In Europe, many master paviors emerged and established monopolies in this industry.
These master paviors concentrated on the road surface and it was only with the increase in the weight and number of vehicles using the road, that attention became focused on the requirements of the underlying base and sub-base and the evolution of the substructure was developed.
Historically, there were four types of small elements used to pave urban areas and because of the cost, the below were manufactured.
- Stone setts
- Wooden blocks
- Concrete blocks
Creating Priceless Memories
1) Stone-sett pavements, early city pavements were laid in cobblestones, typically 100 to 150 mm in diameter, collected from river beds. These were laid in a layer of coarse sand which also used to fill joints. Where cobblestones were unavailable, pavements were sometimes constructed with quarried stones that were trimmed in rectangular, pentagonal or hexagonal shapes and were used. This provided a very rough uneven surface and by the eighteenth century these began to be displaced by pavements laid in stone setts.
2) Wood-Block pavements were often used as an alternative to stone setts especially where it was desired to reduce the noise caused by steel wheels and horses’ hooves early in the nineteenth century. These block sizes were 122 to 250 mm long and 75 to 100 mm square although in some early wood-block pavements in America round blocks were used.
3) Brick Pavements. There are documented reports of brick pavements been used from as early as the first 5000 years. The earliest evidence of such pavements comes from Mesopotamia because of the lack of local stone, pavements were surfaced with bricks.
4) In the USA and Europe, the selection of brick thickness was largely empirical. In the American mid west, experience showed that brick thicknesses as little as 60 mm could successfully withstand motor vehicles. To verify this, accelerated trafficking tests were initiated in 1926 by the Bureau of Public Roads. The objective was to examine the feasibility of using brick thicknesses of 75 mm or less. These tests appear to be the first test track evaluations of a segmental pavement and it represented one of the first evaluations of any pavement made using scientific methods.
Just like the case of stone setts, bricks were generally installed on a sand bed placed either directly on the sub grade or on a broken stone base and the joints were filled with sand or more commonly, with a bituminous material applied hot..
The principal problem associated with brick pavements was their propensity to surface damage. In an attempt to strengthen brick pavements, experiments were conducted in Holland and America whereby both transverse and longitudinal steel reinforcement was laid in joints which were then mortared. Tests conducted in Illinois in the 1930s showed such pavements could carry heavy traffic with little or no maintenance. A more conventional approach was developed in Hungary where very high quality paving bricks were made from clay with a high lime content which was moulded in steel forms under high pressure and fired at high temperatures. This process yielded bricks with strengths similar to basalt setts and enabled pavement lives of about 30 years under traffic to be achieved. However, in general, brick pavements normally had an effective life of less than 20 years.
There were two types of concrete blocks been used in roadworks and these comprised of asphaltic concrete and Portland cement concrete. Asphaltic concrete blocks laid on sand and with sand used to fill the joints were used in America in the early part of this century and comprised of a mixture of sand, aggregate and bitumen. The hardness of the bitumen was found to be crucial to pavement performance and hard grades of bitumen led to cobbling of the blocks in a manner similar to that observed in stone and brick pavers whilst the use of soft grades led to the disappearance of the joints and to deformations in the pavement. To balance these conflicting requirements proved difficult and the use of asphalt blocks was eventually in favour of machine laid asphaltic concrete surfacing.
Major development of concrete pavers occurred in Germany and the first concrete blocks were manufactured at the end of the nineteenth century and several patents were issued before World War I. It was quickly recognized that the concrete pavers provided better uniformity than the stone setts and that they obviated the need to dress any of the faces of the block before laying. Moreover, by the 1930s, compressive strengths of 1000 MPa were being achieved. The first significant test of concrete brick paving appears to have been at Neuss in 1936. Here rectangular units 240 x 120 x 80 mm were successfully tested under heavy traffic. However, prior to World War II concrete pavers were seen largely as a substitute for stone setts.
The main impacts for the development of concrete brick paving occurred in post war Holland. In the 1950s there was a substantial growth in the Dutch population. This, coupled with the needs of war damage reconstruction, resulted in a large increase in the demand for new houses. This led to a shortage in bricks and brick manufactures switched much of their production therefore expensive pavers were reluctantly accepted as a substitute for bricks. These blocks were manufactured in the same rectangular formats as the brick pavers. Initially the bricks and blocks had similar costs but increasing mechanization and a lower energy consumption in the concrete block manufacturing industry eventually led to blocks being produced at just 40 per cent of the cost of bricks.
The successful use of concrete brick paving in the Netherlands was soon copied in Germany. Here, however, unlike Holland which persisted in the use of rectangular units. The main advances in concrete brick paving followed the introduction of shaped units in the mid 1950s.
Concrete pavers were originally developed as a substitute for bricks or stone setts and from the 1950s onwards there was a steady evolution in block shape. At first the blocks merely imitated the stone sets or bricks for which they were to substitute. Formats and dimensions of the blocks were identical to the existing setts and bricks. The only engineering advantages of the blocks over other types of paver was the costs and dimensional consistency of the units. In the second stage of the evolution, the block shape began to be refined so that each unit could fit in with others and various shapes became available.
In a technical sense the evolution of shaped blocks served to differentiate concrete pavers from all earlier forms of segmental paving and the introduction of shaped units also acted as a market stimulus. In this respect there was a rapid proliferation of proprietary paving systems until, by the late 1970s, at least 200 systems were being marketed.
Not only was concrete brick paving more cost-effective than other small-element pavers but the emergence of a variety of proprietary shaped units made concrete brick paving much more versatile than any of the earlier forms of segmental pavement.
This made it inevitable that the use of concrete brick paving was firmly established in America, South Africa and during the 1970s was introduced to the other countries of the world and most recently the use of brick paving has spread to the Middle East and Asia.
Paving - Maintenance
Regular maintenance and good cleaning practices will enhance the overall appearance of your paving.
General Cleaning of Paving
Regular hosing and sweeping will not only keep your paving looking clean but it will also prevent weeds from taking root as they usually grow when seeds are left undisturbed to germinate in the debris that collects in between the pavers.
To remove general dirt and detritus, regularly hose down your paving and sweep with a hard bristled outdoor broom.
When the paving is heavily soiled, scrub the area with a hard bristled brush or broom, soap (a general purpose, pH neutral/slightly alkaline, non-abrasive cleaner can be used). Ensure all the soap has been thoroughly washed off from the surface after cleaning and that the run-off soapy water is channelled to drainage points or containers where it can be disposed of safely.
Note: Do not use power hoses to clean paving as this may wash out jointing sand and damage the grouting between pavers and will damage the pavers themselves.
We recommend specialised products from Tile and Floor Care.http://www.tfc.co.za/
It is essential to seek expert advice and guidance. We cannot accept any responsibility for inappropriate use of detergents or the incorrect application thereof.
It is advised that sections of paving, at least, be cleaned daily on commercial pedestrian areas like shopping centre piazzas and walkways. For daily maintenance of large paved areas, we recommend the use of specialised equipment.
Goscor is the agent for Tennant cleaning machines in South Africa. Tennant is regarded as the world leader in this field.
It is strongly advised that an industry expert advise you on equipment to be used on your site.
The following recommendations deal with sweeping machines and associated equipment and their use:
- Equipment should be designed for the purpose of sweeping the particular area. If there is any doubt, the vehicle manufacturer should be consulted.
- Tyres should be inflated according to the manufacturer’s recommendations to ensure maximum weight distribution.
- Polypropylene brushes, not wire, should be used.
- Sweeping brush pressures should be set to the minimum requirement suitable for the particular task, i.e. surfaces swept regularly will require a lesser setting than those swept infrequently or those covered with heavy deposits.
- When sweeping, engine revolutions should be set at the minimum requirement to maintain vacuum (suction) pressure.
- Operators, including relief staff, should be trained to vehicle manufacturer’s recommendations and tyre and brush pressures should be checked regularly.
- Advice should be given to operators that, when equipment is stationary or left unattended, suction, brush rotation and water jetting equipment should be switched off to avoid the risk of damage to the area below the stationary equipment.
- In new or re-laid areas, allow the pavement to settle and the joints to seal before manual cleaning.
- When water jetting equipment is used to wash such areas , the jets or hand held lance should be directed at the surface at an angle not greater than 30° and across the diagonal (i.e. not parallel to joints) using a suitable detergent solution.
- The area should be inspected after cleaning to ensure that joints are refilled with jointing sand if necessary.
Stain removal & Spot Treatments
- Oil stains: As soon as the stain appears dab excess spillage with an absorbent cloth or towel. Then remove the stain with soap, water and a brush. Ensure that all residues are washed away with hot water.
- Scuff marks from vehicle tyres: These marks can normally be removed by scrubbing the area with hot water and a strong detergent. Remember to rinse thoroughly.
- Rust stains, concrete, plaster and paint marks: Call in a cleaning professional to assist with the cleaning of these particular marks on your paving.
- Smoke, fire and tobacco stains: Stains like this can normally be removed by scrubbing with hot soapy water. If the stain is persistent, apply a mild bleach solution and then rinse the area with clean water, taking care to dispose of the run-off safely.
- Beverage, smoke, fire and tobacco stains: These can normally be removed by scrubbing with hot soapy water. If the stain is persistent, apply a mild bleach solution and then rinse the area with clean water, taking care to dispose of the run-off safely.
Weeds on Paving
It is a common misconception that weeds grow from underneath the paving. This may occur in rare instances; however weeds almost always grow from seeds and bird droppings that land in paving joints from above. Regular hosing and sweeping of the paved area will prevent weeds from growing as it disturbs newly emerging weeds before they are fully established.
Paving Maintenance tips
Inspect paving on a quarterly basis:
This is done to check for any loose, damaged or stained paving, and to ensure that the jointing material is intact.
- Loose paving.
It is important to rectify the cause of the movement / settlement. Subsidence of the substrate layers are the most common reasons for pavement failure.
No matter what the cause, it needs to be investigated and rectified before replacing or re-bedding the paving units.
- Damaged or stained paving.
Individual blocks can easily be replaced. Call Paving worx for assistance and advice.
- Jointing material that is no longer intact.
The pavers simply need to be topped with jointing sand by brushing or sweeping in approved, dry plaster sand as required.
Maintaining your paving during construction
Paving should be kept covered during construction or renovation to protect it from damage and possible staining from paint or oil-based substances as well as any harsh chemicals.
Sealing of paving
We recommends using products from Tile and floor care or Resiblock imported by Cretesol.
It is strongly advised to seek expert advice from such an industry specialist.
Sealing of concrete products should be done six months after installation in order for products to cure fully on site and for possible efflorescence to take its course.
It must be expected that sealants may have an effect on the colour of the paving, its slip/skid resistance and may require on-going maintenance during the life of the paving. It is also important that the surface of the units is dry, clean and efflorescence-free before any sealer is applied.
Benefits of sealing your paving
- Improving its appearance
- Under some circumstances, prolonging its life
- Helping to seal the jointing material
- Inhibiting weed growth
- Stain prevention (especially from oil based stains)
The Cure for Efflorescence
We believe the best cure for efflorescence is to just leave it as it will go away with time.
From experience we know that some paving installations have had efflorescence for a few weeks only, while others have been affected for months. Sometimes efflorescence is recurring and sometimes it happens only once. Therefore one can never predict the outcome of a specific site. What we do know however is that it is temporary.
When you “Google” (Remove efflorescence), there are around 260,000 results. Most of them recommend washing the affected material with a weak acid solution. It might however re-appear within a day. As mentioned, man can’t force nature to change.
Paving Worx believes the use of acid is not worth the risk. If however you are forced and /or prepared to take the risk, we recommend consulting the following British web page, for an objective and very comprehensive take on efflorescence, together with some removal options.
The above information is intended as a general guideline on the cleaning and maintenance of precast concrete paving and is not intended to be a comprehensive guide.
It is particularly important with all cleaning methods that a test should be carried out on a small, preferably inconspicuous area, to determine the effect of the treatment before commencing work on a larger area.
Clay Paver Maintenance
Clay pavers require no special maintenance as natural weathering keeps most clay paving systems clean and beautiful. Pressure washers are not recommended for use on flexible base applications. The pressure washer tends to remove joint sand which compromises interlock. We suggest using a stiff application brush and a normal pressured garden hose. For specific cleaning situations like oil stains or spills, use commercial cleaners generally available at masonry supply outlets. When using any type of cleaner, always test on a small hidden portion of the pavement. Prewet pavement thoroughly before cleaning and rinse after with clean water. In mortared applications, use Sure Klean 600 or 202 New Masonry Detergent, or equivalent as directed. Vanatrol or 202V Vana-Stop or an equivalent product should be used to clean all light colored and brown pavers. DO NOT USE MURIATIC ACID. Pressure washers can be used provided application pressure is limited to 30-50 psi and a 50-degree Fan Tip is used. Rinse pressure should not exceed 200-300 psi.
Moss & Weeds
The existence of moss is an indication of poor drainage(in a shaded area) as the saturation of water creates an ideal environment for growth. The best solution is to keep the area dry by improving drainage or elevation although these remedies may not be practical. For moss and organic growth removal, a three-to-one solution of water and chlorine bleach is recommended or a one to one dilution in severe cases. Weed growth in flexible base paving systems is common in lower traffic areas. Contrary to popular belief, growth takes place in the sand joint and not from underneath the pavers. Weed killer such as Round Up will handle existing growth while a pre-emergent weed killer can be used in the spring as a prevention measure. Joint sand stabilizers are also effective at weed prevention (Surebond1370 or Sandlock).
Cleaning of Clay Paved Surfaces
These notes are intended for general guidance and are not intended to be exhaustive. Clay paving provides a durable, hardwearing surface but, like any surfacing material, this may suffer from time to time from staining, due to general trafficking and contamination from other sources.
Due to the nature of construction, there may also be some vegetation growing in the joints, or on the paving themselves in shaded areas or areas subject to long periods of dampness. As for any other surfacing material regular maintenance and good cleaning practice will enhance the overall appearance of the paving.
Initial maintenance – flexibly laid clay pavers
During the very early life of the pavement, the joints between the pavers will be relatively porous.
The ingress of water will consolidate the jointing sand and it is important that the joints are regularly filled with jointing sand to replace the sand consolidated by the rainwater. The joints will soon become semi-impervious due to detritus tending to seal the joints. Until this has occurred the paving should only be brushed by hand.
Mechanical sweepers, and in particular sweepers with high suction forces should not be used.
If they are used, there is a real risk of loss of jointing sand from between the pavers.
There is a number of water miscible liquids that can help to stabilise the joint filling sand. These can aid in the reduction of the removal of sand by suction cleaners, and at the same time, helps to prevent the ingress of water during the early life of the pavement. It is essential to consult with the paver manufacturer before applying any form of surface treatment.
General dirt and detritus
To remove general dirt and detritus, regular brushing is recommended. If detritus masks the colour of the material then this can be reestablished by scrubbing with hot soapy water. This can be carried out by hand or by using an industrial cleaner. Ensure that all the detergent has been thoroughly washed from the surface on completion of the cleaning and the resulting run-off is carefully channelled to either drainage points or containers where it can be safely disposed of. If a hose is used, then care must be taken to avoid the removal of the jointing material (sand or mortar).
Moss, lichens and algae
Moss, lichens and algae should not grow on clay pavers unless the area is heavily shaded, is under trees, or is not laid to an adequate fall. If such growth does occur and is considered undesirable then the area should be treated with a proprietary moss killer used in accordance with the manufacturer’s instructions.
Such products take some days to be effective and work best when applied during a spell of dry weather.
Any thick growths should be scraped off first and the chemical treatment well brushed in.
Some treatments leave a residue to discourage the re-growth of the moss and algae, but this will only be of limited value if the paving remains damp and in shade.
First of all, action must be taken to eliminate the sources of staining. To remove the rust stain the surface should be made wet and then the affected area treated with a 5-10% hydrochloric acid solution. Before cleaning, provision should be made for the collection and disposal of waste chemical materials, in accordance with legislative requirements. Buff clay pavers should NOT be treated with acid without first discussing the stain with the paver manufacturers.
Oil does not penetrate readily into clay pavers, but if oil is spilt on the pavers, the spillage should be removed promptly with an absorbent material, such as paper towels. The oil should not be wiped up; otherwise this will spread the contamination on the surface of the paver. Steam cleaning can be used on clay pavers to remove such staining, but if this is unsuccessful an emulsifying de-greaser should be employed. Brush with plenty of water to safe disposal. An alternative cleaning method is to brush the area with a strong detergent and hot water. This will not affect the colour of the clay paving.
Bitumen does not penetrate readily into clay paving. The best method of removal is to leave the bitumen until it has cooled. A paint scraper or a similar mechanical device can then often remove it. If it is particularly resistant, the use of ice to make the bitumen even more brittle may be required, prior to scraping it from the paving. Any residue should be removed with a scouring powder and finally the whole area rinsed with clean water. Certain proprietary cleaning agents are available to remove bitumen, but these should be tested on an inconspicuous area of paving first.
Graffiti and paint stains
Both paint and graffiti are difficult to remove. Fresh wet paint should be soaked up with an absorbent material without wiping the paint, as this will spread the stain. It should then be treated with a suitable solvent, such as white spirit, and then the area washed with a de-greasing agent taking care in the disposal of the run-off material. With dried paint, the paint should be scraped off as far as possible and then a paint remover to BS3761 (4) should be applied.
Smoke, fire and tobacco stains
Normally these stains can be removed by scrubbing with hot soapy water. Where the stains persist, scouring powder or household bleach solution has been found to be successful.
These can normally be removed by scrubbing the stain with hot soapy water. If the stain is persistent, apply bleach solution and then rinse the area with clean water, taking care to dispose of the run-off safely.
Chewing gum is one of the most difficult substances to remove from any surface material. Newly discarded gum can be scraped off by using a scraper, but hardened gum can only be removed by freezing the gum and chiselling it from the surface of the paving or, alternatively, by using a hot water/steam cleaner. There is a number of contract cleaning companies who specialise in this type of cleaning, and it is advised that they are contacted directly for further details.
Scuff marks from vehicle tyres
These can normally be removed by steam cleaning, or by scrubbing the area with hot water and a strong household detergent solution.
Efflorescence on clay pavers
Any soluble salts showing on the surface of the paver should be allowed to weather away naturally, as experience shows that such weathering will occur quite rapidly. These salts are not damaging to clay paving. Chemical treatments should not be used. Certain light coloured pavers are manufactured from fireclay and in extreme cases may suffer from metallic salts staining. Vanadium efflorescence takes the form of a yellow/green stain, and orange/brown deposits may result from iron or manganese compounds. These stains should be allowed to weather away naturally, but if they persist contact the paver manufacturer.
Remove large deposits with wooden implements to avoid damaging the paver surface. Following the pre-wetting of the area, treat the residue of mortar by careful application of a dilute hydrochloric acid solution or a proprietary cleaning solution. The application of the acid breaks down the cementitious components but is not damaging to clay pavers. As with all cleaning procedures a rinsing operation should be carried out shortly after application, and care taken to dispose of run off solutions safely. If the above method is not successful with coloured mortars, specialist advice from the coloured mortar supplier should be sought.
On the rare occasions when a vanadium efflorescence is present, hydrochloric acid based cleaners must not come into contact with the efflorescence, otherwise a dark stain will result which will become fixed on the surface.