DESIGN AND CONSTRUCTIONCLAY PAVING

Acrobat Edition

C l a y Pa v i n g D e s i g n a n d C o n s t r u c t i o n

Clay Brick and Paver Institute

PO Box 6567, Baulkham Hills BC, NSW 2153, AustraliaTel (02) 9629 4922Fax (02) 9629 7022info@claybrick.com.auwww.claybrick.com.au

Clay pavers have a long and illustrious record of creating attractive and durablepavements in a wide variety of applications including paths, pedestrian areas,driveways, patios and recreation areas.This manual contains recommendations from the Clay Brick and PaverInstitute for the design and construction of flexible and rigid clay pavements.Also covered are paver selection, material specifications and maintenance,including cleaning and stain removal.Cover: Moore Park Gardens, a major redevelopment project on the former Resch’s Brewery site ininner Sydney. Reg Smith, project director for architects Allen, Jack + Cottier, describes the clay pavedinternal street as “one of the most successful aspects of the whole project. We paved the footpathsand road and because it’s a shared zone it tied the whole thing together very well.” The pavers arelaid on a concrete base with sand-filled joints. Photograph by Jackie Dean, Dean Photographics.

First published July 2001, amended March 2002, and May 2003ISBN 0-947160-06-X This publication, its contents and format are copyright of the Clay Brick and Paver Institute, and may not bereproduced, copied or stored in any medium without prior, written authorisation from the Institute. The ClayBrick and Paver Institute is wholly sponsored by the Australian clay brick, block and paver industry. Local orstate regulations may require variation from the practices and recommendations contained in this publication.While the contents of this publication are believed to be accurate and complete, the information given isintended for general guidance and does not replace the services of professional advisers on specific projects.The Clay Brick and Paver Institute cannot accept any liability whatsoever regarding the contents of thispublication. Copyright © Clay Brick and Paver Institute 2001. ABN 30 003 873 309.

1 Introduction ..................................................................................4

2 Definitions ..................................................................................5

3 Specifying clay pavers ...................................................................6

3.1 General .............................................................................................6

3.2 Relevant standards ..............................................................................6

3.3 Relevant tests ......................................................................................6

3.3.1 Work size................................................................................6

3.3.2 Breaking load ..........................................................................6

3.3.3 Other tests ..............................................................................6

4 Flexible pavements ........................................................................8

4.1 Applications ........................................................................................8

4.2 Laying.................................................................................................8

4.2.1 General...................................................................................8

4.2.2 Subgrade ................................................................................8

4.2.3 Base course ............................................................................9

4.2.4 Bedding course........................................................................9

4.2.5 Laying pavers ........................................................................10

4.2.6 Joint filling ............................................................................12

4.2.7 Compaction of surface course .................................................13

4.2.8 Edge restraints.......................................................................13

4.3 Flexible pavements for sloping driveways..............................................14

4.3.1 General.................................................................................14

4.3.2 Restraint system ....................................................................15

4.3.3 Drainage ...............................................................................15

4.3.4 Laying patterns......................................................................15

4.3.5 Maintenance .........................................................................15

5 Rigid pavements ..........................................................................16

5.1 Applications ......................................................................................16

5.2 Laying ...........................................................................................16

5.2.1 Subgrade ..............................................................................16

5.2.2 Base course ..........................................................................16

5.2.3 Paver laying ..........................................................................16

5.2.4 Expansion joints ....................................................................17

5.2.5 Joint filling ............................................................................17

2

Ta b l e o f C o n t e n t s

3

6 Maintenance ...............................................................................18

6.1 Early trafficking and cleaning...............................................................18

6.2 Basic cleaning principles ....................................................................18

6.2.1 General.................................................................................18

6.2.2 Select correct cleaning chemicals.............................................18

6.2.3 Follow correct cleaning procedures...........................................18

6.2.4 Safety precautions essential ....................................................18

6.3 Removing common stains ...................................................................19

6.3.1 Efflorescence .........................................................................19

6.3.2 White scum...........................................................................19

6.3.3 Dirt and grime .......................................................................19

6.3.4 Vanadium stains ....................................................................19

6.3.5 Fresh mortar stains ................................................................20

6.3.6 Hardened mortar stains ..........................................................20

6.3.7 Fungi, moulds, moss and lichens ............................................21

6.3.8 Oil, bitumen and tar...............................................................21

6.3.9 Food stains and tyre marks .....................................................21

6.3.10 Chewing gum........................................................................21

7 References ................................................................................22

Figures

1. Section through a typical clay pavement and edge restraint...............................5

2. Paving patterns ............................................................................................5

3. Typical stringline grid ..................................................................................11

4. Well-filled sand joint ...................................................................................12

5. Vibrating plate compactor with glider attachment ...........................................13

6. Edge restraints ...........................................................................................13

7. Typical plain transverse beam for a single residence driveway .........................14

8. Typical drainage systems.............................................................................15

9. Section through typical rigid clay pavement...................................................17

Tables

1. Specification requirements for clay pavers .......................................................7

2. Bedding and jointing sand ............................................................................9

4

1 . I n t r o d u c t i o n

This publication containsrecommendations by the Clay Brickand Paver Institute for the use of claypavers in flexible and rigid pavements(see Section 2, Definitions). It alsohas information on the specification,design, installation and maintenanceof clay pavements.Local experience may support thedeparture from these recommendationswhere the performance in the field hasbeen demonstrated over a period oftime.

The decision as to whether a flexibleor rigid pavement is used depends onspecific site conditions and acomparative cost analysis of the twosystems. This decision must be madeon an individual project basis and,therefore, no recommendations aremade here as to which type ofpavement system to utilise.This manual supersedes and replacesDesign Manual 1, Clay SegmentalPavements and Paver Note 1,Specifying and Laying Clay Pavers,both published by the Clay Brick andPaver Institute.

Pavers with dry jointsmortared to concrete Jointing Clayedge strip or pressed sand paversinto low-slump concrete

Surfacecourse

Beddingcourse

Basecourse

2 . D e f i n i t i o n s

Base course: The structural course orlayer of granular material beneath thebedding course (see Figure 1). Thebase course distributes loads to thesubgrade.Bedding course: The layer or courseof sand on which the pavers arebedded to form the pavement surface(see Figure 1). Generally a well-graded sand is used for this purpose.California Bearing Ratio (CBR): Anindicator of the shear strength ofsubgrade material.Clay pavers: Fired clay unitscomplying with the specification andintended to form the surface courseof a pavement (see Figure 1).Edge restraint: An existing orconstructed element forming aboundary to the paved area. Edgerestraints minimise lateral movementof the pavers and material loss fromthe bedding course (see Figure 1).Flexible pavement: A pavement thatdoes not rely on a rigid layer, such asa concrete slab, to distributesuperimposed loads to the subgrade.Formation: The final shape of thesubgrade surface followingcompletion of earthworks.Herringbone bond: A laying pattern ofthe general form illustrated in Figure2. This is the preferred laying patternfor pavements used by vehicles.

Interlock: The effect of frictionalshear forces induced in the sand-filled joints between pavers thatinhibits paver movement andtransfers loads between adjacentpavers. Interlock accounts for theload-spreading capability of pavers.Jointing sand: Fine sand that isswept and vibrated to fill the verticaljoints between pavers (see Figure 1).It is important to note that beddingsand is not always satisfactory as ajointing sand.

5

Laying face: The working edge of thepavement, that is, where pavers arebeing laid during construction.Light vehicular traffic: Areas subjectto occasional light vehicular traffic,typically cars and station wagons, inapplications such as off-street carparks. Access driveways, loadingbays and other areas used bycommercial vehicles with axle loadsgreater than 2.7 tonnes are excluded.Rigid pavement: A pavement thatrelies on a rigid layer, such as aconcrete slab, to distributesuperimposed loads to the subgrade(see Figure 9).Severe marine environment: Theportion of land up to 100 m from anon-surf coast and up to 1 km froma surf coast.Subgrade: The upper part of the soil,natural or constructed, that supportsthe loads transmitted by the overlyingpavement layers (see Figure 1).Surface course: A layer of pavers ona bedding course that act as awearing course and a majorstructural element of the pavement(see Figure 1).Wearing surface: The surface thatthe clay paver manufacturer hasdesignated to be laid uppermost andtrafficked.Work size: The dimensions adoptedfor manufacture.

Figure 1. Section through a typical clay pavement and edge restraint

Figure 2. Paving patterns

Basketweave 2x1 Basketweave 2x2 Zig zag running bond Circular (radial)

Tracery Stack Stretcher Stack and stretcher

Offset stretcher Offset running bond 90˚ herringbone 45˚herringbone

SubgradeConcrete edge strip

6

3.1 GeneralThis section contains recommendationsby the Clay Brick and Paver Institutefor the minimum requirements forclay pavers intended for use in thenominated applications.Local experience may supportdepartures from the specifiedprovisions where satisfactoryperformance in situ has beendemonstrated over a period of time.Manufacturers of clay pavers shouldbe consulted for details.

3.2 Relevant standardsAS/NZS 4455:1997 Masonry Unitsand Segmental Pavers1 sets out theinformation that is required to bemade available by suppliers of claypavers.AS/NZS 4456:1997 Masonry Unitsand Segmental Pavers – Methods ofTest2 describes the procedures thatmust be followed to determine therequired physical properties of thepavers.AS/NZS 4586:1999 Slip ResistanceClassification of New PedestrianSurface Materials3 provides a meansof classifying clay pavers according totheir characteristics of friction and,therefore, their suitability for specificapplications.

3.3 Relevant tests3.3.1 Work sizeAS/NZS 4455:1997 requiressuppliers of clay pavers to makeavailable the work size of the units.This is determined in accordancewith AS/NZS 4456.3:1997Determining Dimensions, Part ADetermination of CumulativeDimensions4. This test involves theoverall measurement of 20 units forlength, width and depth.

3.3.2 Breaking loadAS/NZS 4455:1997 requiressuppliers of clay pavers to makeavailable the characteristic breakingload of the units. This is determinedin accordance with AS/NZS4456.5:1997 Determining BreakingLoad of Segmental Paving Units5.

In this test a paver is placed with itsbedding face supported by a bar ateach end. A load is applied throughanother bar on the centre of the topface. The load is increased until thepaver fails. The maximum load is thebreaking load of the paver.It should be noted that breaking load,not compressive strength, is thestrength criteria for assessing theperformance of clay pavers.

3.3.3 Other testsAS/NZS 4456.9:1997 DeterminingAbrasion Resistance6 sets out theprocedure for testing the abrasionresistance of clay pavers whensubjected to the impact and rollingaction of ball bearings. Test resultscan be used to predict unit wear inits intended application.AS/NZS 4456.10:1997 DeterminingResistance to Salt Attack7 enables aprediction of the performance of claypavers in the intended exposureenvironment (see Section 2,Definitions, ‘Severe marineenvironment’).AS/NZS 4586:1999 Appendix A.Slip Resistance Classification of NewPedestrian Surface Materials: WetPendulum Test Method8. Resultsfrom this test are used to predictpaver slip/skid resistance.

3 . S p e c i f y i n g C l a y P a v e r s

7

Residential pavementsPedestrian traffic only 40 2 DP0Driveway, light

40 3 DPA1 W No requirementvehicles onlyDriveway, including

60 5 DPA1commercial vehiclesPublic area pavementsPedestrian traffic only

40 2 DPA1(see notes 1 to 3)Pedestrian traffic Low volume: 7and light vehicles 50 3 DPA2 W Medium volume: 5.5(axle loads <3.0t) High volume: 3.5

Pedestrian traffic andcommercial vehicles 60 5 DPA2 (axle loads >3.0t)RoadsGeneral vehicle trafficon minor or local roads 60 6 DPA2 W No requirement(see note 4)

Application Minimum Minimum Dimensional Slip resistance Mean abrasionthickness characteristic deviation classification resistance

(mm) breaking load (cm3)(kN)

Notes:

1. Typical low volume pedestrianareas include paths in publicgardens, schools or campuspavements, hard landscape areas,and common areas of residentialbuildings.

2. Typical medium volume pedestrianareas include suburban shoppingarea pavements and pedestrianareas around institutionalbuildings, sporting or recreationalvenues.

3.Typical high volume pedestrianareas include inner city and majorsuburban pedestrian malls andpaths, and pavements with highvolume pedestrian traffic (over30,000 passes per day) includingabout one-third with high-heeledshoes.

4. Minor and local roads, excludingcollector roads, carrying up to1000 vehicles per day.

Table 1. Recommended specifications for clay pavers

5. Pavers not reaching theserequirements may be used whensupported by local manufacturer’sexperience and performance data.

6. Other test methods may be usedwhen they have been usedextensively and shown to relate toperformance data.

7. Exposure grade units are requiredfor use in severe marineenvironments and around salt-water swimming pools.

8

4.1 ApplicationsFlexible clay pavements (see Section2, Definitions) have been successfullyused in a wide variety of applicationsfor many years, including:• domestic pathways• patios• domestic driveways• pedestrian areas.In some locations, flexible pavementshave provided effective service inapplications where heavy vehicletraffic occurs. The manufacturer’sadvice should be sought as to theirlocal knowledge regarding this point.

4.2 Laying 4.2.1 GeneralA flexible pavement consists of thefollowing components (see Figure 1and Section 2, Definitions):• subgrade• base course• bedding course• surface course• jointing sand.The design of the lower courses iscritical to the pavement’s finalperformance. With the possibleexception of domestic pathways, allflexible pavements should bedesigned around specific siteconditions. It is up to the designer orcontractor to ensure there isadequate information or that therequired testing is carried out.

4.2.2 SubgradeThe California Bearing Ratio (seeSection 2, Definitions) of thesubgrade should be assessed whenconsidered necessary by the designeror contractor. The CBR is an indicatorof the shear strength of the subgradematerial and widely used as a meansof assessing subgrade strength forhighway design.The CBR of a soil can be measureddirectly or derived from a knowledgeof other soil properties. The nature ofclay paving projects is such that CBRvalues are often estimated ratherthan measured. Direct measurementcan be made in the laboratory on

undisturbed or remoulded samples.In the field a standard site testapplies. Note however, that theobjective is to provide the in-servicemoisture conditions under theconstructed pavement and tomeasure the CBR under theseconditions.It is important to relate the scale ofthe site investigation to the size ofthe project. In small schemes, thecost of measuring CBR directly maybe more than the saving thatknowledge will permit. In largeschemes, differences in soilproperties across a site may suggestdifferent designs for different parts ofthe site. In situ testing identifies therange of materials present. Howeveran allowance must be made for thewater content of the material testedwith a comparison is made withlaboratory-soaked CBR values.

Width of subgradeThe subgrade should be prepared tothe required profile. It should besufficiently wide to extend to the rearface of the proposed edge restraintsor to the face of existing abuttingstructures.

Drainage of subgradeWhen necessary the excavationprepared for the pavement shouldhave piped or channelled stormwater and subsoil drainage. Alldrainage trenches within the pavedarea should be backfilled to ensurethey perform similarly to theundisturbed ground. All piped andsubsoil drainage construction locatedbeneath the pavement should becompleted in conjunction withsubgrade preparation before thecommencement of base courseconstruction.The objective of this requirement isto prevent the accumulation ofsubsurface water anywhere in thearea excavated for the pavement.Water accumulating in this locationcould reduce the stability of thewhole structure or bring efflorescingsalts to the pavement surface anddetract from appearance or durability.

4 . F l e x i b l e Pavemen t s

9

Removal of unsuitable materialAny unsuitable material should beremoved from the subgrade andreplaced with appropriate material,such as properly compacted basecourse material. Proof rolling may beused to locate areas of unstablesubgrade. Closely observing the effectof the slow passage of a wheel of aladen sand truck often clearly revealsunsuitable subgrade material.Bedding course sand should not beused a replacement material.

ResurfacingClay pavers are ideal for resurfacingestablished formations and existingpavements such as residential streets,pedestrian precincts and footpaths.These can usually be regarded as asuitable subgrade.

4.2.3 Base courseBase courses should be designed onthe basis of sound engineeringprinciples and the CBR of thesubgrade. The surface of the baseshould be close-knit to preventbedding course material from movingdownwards. It must be of goodquality to avoid failure due to highstress concentrations immediatelyunder the surface course of pavers.The base course material should bespread and compacted in layers. Thethickness of these layers must beconsistent with the compactioncapability of the equipment beingused. Note that on large projects avibrating plate compactor may not besuitable for this task; a vibrating rollermay be required. This particularlyapplies to pavements carryingvehicles.

4.2.4 Bedding courseGeotextile materialsGeotextile materials can be used togreat effect as drainage layers andseparation layers. In both applicationsit is recommended the fabric beplaced between the base course andthe bedding sand. In this position itcan drain the bedding layer andprevent bedding material being lostinto the base course.On reactive clay sites subgradecracking may cause loss of bedding

sand accompanied by subsidence.The separation layer of geotextilefabric prevents this and stiffens thepavement.

Bedding course materialBedding course material should be awell-graded coarse sand. In theabsence of other indications ofsuitability, sand of the sort used formaking concrete should make asatisfactory bedding course. Saltattack is a potential problem withsome clay paving and the capillarybreak provided by a coarse beddingsand is essential. Concrete sandscontaining less than four per cent ofmaterial passing through the 75micron sieve should prove suitable.The sand gradings shown in Table 2are recommendations only. The finalselection of sand for bedding andjointing is dependent upon the gradescommercially available in the region.

100

90

80

70

60

50

40

30

20

10

0

75 150 300 600 1.18 2.36 4.75 9.52

Sieve size (µm/mm)

A sand which conformsto the dark section ofthe graph (where theenvelopes overlap) willbe suitable for bothbedding and jointing

% P

assi

ng

Table 2. Bedding and jointing sand

Sieve size PercentpassingJointing Bedding

sand sand

9.52mm n.a. 1004.75mm n.a. 90-1002.36mm 100 75-1001.18mm 75-95 55-90600 microns 50-80 35-59300 microns 20-45 8-30150 microns 5-15 0-1075 microns 0-5 0-5

Sieve size Percent passingJointing Bedding

sand sand

JOIN

TIN

G

BED

DIN

G

10

Bedding sand constructionEither of the following installationprocedures is acceptable:• Spread the material loose and

screed to the final level plus anamount to accommodate thereduction in thickness that willoccur when the pavers are vibrated;

• Spread a loose uncompacted layerequal to the final requiredthickness. This sand is vibratedusing the same vibrating platecompactor as that used for vibratingthe pavers. Finally spread andscreed a further layer to form aloose surface onto which the pavers can be laid.

In either method the sand should bedisturbed as little as possible prior topaver installation. Any disturbancemay lead to final surface undulations.Gaps between edge restraints or atthe intersection with other pavementsshould be sealed to avoid loss ofbedding sand.

4.2.5 Laying paversSelectionPavers should be selected byreference to Section 3.0 as to theirsuitability for the intended application.

Laying patternsTwelve laying patterns are shown inFigure 2. Herringbone (both 45 and90 degree) is recommended forwheeled traffic areas. Many otherdecorative laying patterns are possiblebut are only suitable for pedestrianareas.The chosen laying pattern willdetermine the way the pattern isgauge controlled. For example inrunning bond the paver unit widthcontrols the gauge in one directionwhile the unit length controls thegauge in the other direction.Herringbone pattern can be laid to agauge based on the unit width onlyregardless of the aspect ratio.Basketweave pattern is easiest tocontrol when the unit length is twicethe unit width plus the nominal jointwidth.

4 . F l e x i b l e Pa v emen t s

Fatty sands, loams or packing sandsare difficult to adequately consolidateas a satisfactory bedding layer anddo not form a capillary break.Crushed stones with excessive fines,such as ‘crusher dust’ or dolomite,are unsuitable because although theycan be compacted they fail to providea capillary break.Moisture content of bedding courseThe moisture content of the beddingcourse should be uniform. Stockpiledmaterial should be covered.Waterproof membranes beneath thebedding course of pavers are notadvised except where the paving isunder cover.Cement-stabilised bedding sandCement-stabilised bedding sands arenot recommended where a well-graded bedding sand is available. Ifpoor quality bedding sands must beused a very lean cement stabilisationmay be appropriate.Mixing in two to four per cent cement(by volume) to the bedding sandproduces a cement-stabilised beddingsand. This is a method of retainingpoor quality sands on sloping sites orwhere water may scour beneath thepavers.For sections of paths with slopes of1:15 or steeper, cement stabilising ofbedding sand is a practicalconstruction approach. For drivewayswith a sloping pavement of greaterthan 5 m, a transverse concretebeam running between edgerestraints should also be used. Acapping course of pavers is mortaredonto the sub-surface beam and thepavers up the slope from the beamare then laid on cement-stabilisedsand. (See Section 4.3 for moreinformation on flexibly paved slopingdriveways.)Bedding sand thicknessFollowing compaction, the beddingsand should be uniformly 30 mmthick with a maximum specified of50 mm and a minimum of 20 mm.The thickness should only be otherthan 30 mm only when the need toachieve fixed levels precludes itsspecification. It is very important toachieve a uniform thickness ofbedding sand.

Bedding sand

Where pavers are out of alignment these must be relaid3 or 4 rows back to correct the error shown shaded

String lines

45˚ herringbone pattern

String lines set at 10 rows apart

String lines may be set perpendicularly as shown or alternatively at 45˚ in line with the long side of the paver.

Figure 3. Typical stringline grid

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Pavers should be laid such that ajoint width of 2 to 5 mm formsbetween each paver with a targetjoint width of 3 mm thus ensuringthere is no point contact betweenunits. Point contact betweenadjacent pavers produces highlocalised stresses that are known tocause edge chipping, reduce sheartransfer and cause patterndistortion.This requires consistent gauging ofthe job to ensure that equal areas orlengths have equal numbers ofpavers. Experienced paviors gauge byeye but still check with stringlines.Stringlines are recommended tomaintain gauging on all jobs.Mechanical force should not be usedto bring pavers into intimate contact.

Figure 3 shows typical stringlinearrangements. When pavers deviatefrom the stringline it will benecessary to remove pavers fromseveral rows and re-lay to thestringline. The shaded pavers in thefigure should be re-laid.TrimmingPavers should be trimmed to shapeand size to form boundaries and towork around any obstructions.Accurate trimming can only becarried out using a masonry saw. It is recommended that the minimumsize of a cut piece be not less thanone-third of the area when cuttingcross-ways or one-quarter when cut diagonally.

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4.2.6 Joint fillingProcedureA suitable fine-graded joint-fillingsand (see Table 2) should be spreadover the surface and swept into thejoints. The use of dry material willassist in rapid joint filling. A sandcontaining clay that is likely to stainthe surface of the pavers should notbe used.Commercially prepared stabilisedjointing sands may be used. Thepaver supplier should be consulted asto the suitability of these materials.

Joints and interlockInterlock is developed during theinstallation of the pavers and can bedefined as the inability of anindividual paver to move in isolationfrom its neighbours. It can be dividedinto three components:1. Vertical interlock prevents a loaded

paver from sliding down the sidesof its neighbours and is developedby the sand that enters the jointsfrom below. This sand rises byapproximately 20 mm during thevibration of the pavers andbecomes wedged tightly betweenthem. Vertical loads applied ontoan individual paver are transferredinto neighbouring pavers as ashear force through this sand, sogenerating vertical interlock.

2. Rotational interlock is developedby providing edge restraint to thepaving and is completed byvibrating in fine jointing sand fromabove. An individual paver canrotate only if its neighbours movelaterally to create the space neededfor rotation. Edge restraints preventthis lateral movement and sogenerate rotational interlock. Theinclusion of the fine sand in thejoints shifts the potential hinge ofrotation to the top of the paver andthereby adds further rotationalinterlock.

3. Horizontal interlock is achieved byensuring that either the layingpattern or the shape of the pavereliminates continuous straight linesthrough the pavement surface.Horizontal interlock is achievedmost commonly by laying arectangular paver in herringbonepattern and there seems to be no structural preference for thealignment of the direction of the herringbone.

In order to facilitate the installation ofthe jointing sand, a fine round sandshould be specified and this shouldbe dry. Sand may be lost from thejoints during the early life of asegmental pavement especially if thepavement has a steep longitudinalgrade. Where loss occurs, jointsshould be ‘topped-up’ to avoid thepossibility of pavers being displaced.

4 . F l e x i b l e Pa v emen t s

Figure 4. Well-filled sand joint

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4.2.7 Compaction of the surfacecourse

Compaction should follow laying andjoint filling as soon as possible butshould not occur closer than onemetre to the unrestrained workingedge of the pavement underconstruction. No area of pavingshould be left uncompacted at thecompletion of the day’s work, apartfrom the edge strip of the laying face.Compaction should be carried out bya vibrating plate compactor with aplan area of not less than 0.25 m2 ora rubber-rollered mechanical vibrator.A vibrating plate compactor is bestfitted with a glider attachment (Figure5) or the plate may be wrapped incarpet. Alternatively a carpet squareor a sheet of plywood can be laidover the pavers to protect them fromdamage. Compaction shouldcontinue until all paver faces are in the same plane.The area to be compacted should beswept clean of joint filling sand andthen receive at least two passes ofthe vibrating plate compactor. Thejoints should then be topped up bysweeping joint filling sand over thearea prior to a final compactionconsisting of at least two morepasses of the vibrating platecompactor.4.2.8 Edge restraintsThe perimeter of all paved areasshould be provided with edge restraintsto prevent lateral spread of the paversand consequent loss of interlock.These should be adequate to supportthe intended loads and to prevent theescape of bedding course materialfrom beneath the paved surface.Edge restraints should be formedbefore compacting adjacent units.Together with any concretehaunching, the edge restraints shouldbe mature before vibration of thesurface course is undertaken.Haunching to an edge restraintshould be continued down to theunderside of the bedding course.Where appropriate, drainage shouldbe provided at edge restraints toprevent the build up of a head ofwater in the bedding course.

Figure 5. Vibrating plate compactor with glider attachment

Paver on edge(or treated timber)

Hardwood edgerestraintHardwood stake

Mortar

Concrete

Concrete edgerestraint poured on site

Figure 6. Edge restraints

Note: concrete is essential for driveways

4.3 Flexible pavements for sloping driveways

4.3.1 GeneralThis section deals with the generalcriteria to be used in the design andlaying clay pavers on slopingresidential driveways. The principlescan be applied to multi-residentialdevelopment sites and to slopingroadways.The general design criteria may needto be further developed or modifiedfor individual sites, depending onlocal soil types, drainage, slope andthe volume and type of traffic. Insome instances it will be necessaryto have a site-specific designprepared by a structural engineer.The most common cause for concernon sloping sites is shunting and edgechipping of individual pavers. Thisproblem is not confined to claypavers, it is common to all pavertypes: concrete, clay andreconstituted stone.In normal use, pavers will only chipif they are able to touch. Furthermorethey will only shunt if the 2 to 3 mmgap between the pavers is able toclose. Therefore shunting andchipping can be eliminated if the gapbetween the pavers is maintained.This is relatively difficult, particularlyon sloping, curved driveways. Evenwhere the gap between the pavershas been completely filled with well-compacted jointing sand during the

laying process, there is still thetendency for the sand to be washedout or ‘pumped’ out by wheel loadson the individual pavers during wetperiods.Localised rutting from inadequate subbase preparation, loss of the beddingsand (usually from poor sub-surfacedrainage), and localised movementsparticularly at edge restraints canalso cause the pavers to push outresulting in eventual loss of sand,shunting and chipping.In order to minimise or eliminateshunting and chipping, the aspectspreviously discussed for flexiblepavements must also be addressedwhen designing and constructing asloping driveway, namely:• sub-grade• road base• bedding and jointing sand• surface and sub-surface drainage• selection of pavers• laying pattern.Two additional items must beconsidered:1. The use of a restraint system2. Ongoing maintenance in order to

retain the jointing sand betweenthe pavers.

The following sections detail theadditional requirements for designingand constructing a flexibly-pavedsloping driveway.

14

4 . F l e x i b l e Pa v emen t s

Clay pavers set in concreteor in 1:4 mortar

Plain concretetransverse beam

Notes:

1.Depth of beam will depend on soil typeeg. for clay soils typically 250 to 300 mm deep

2.Transverse beam not required ifconcrete slab is used. Pavers can bemortared directly to slab

Fall in direction of road

Min. 90 mm Ø µPVCslotted subsoil drain withfilter sock min 1:100 fall

65 mm pavers 30 mm bedding sand

125 mm compacted road base

Figure 7. Typical plain concrete 230 mm wide transverse beam for a single residence driveway

15

4.3.2 Restraint systemPlain concrete transverse beamsshould be strategically placed alongthe driveway, generally at 90 degreesto the direction of traffic flow. Theintention of the transverse beams isto reduce the effective length of thedriveway and hence the potentialfor shunting.The spacing and size of transversebeams will be influenced by thepavement length, slope, soilconditions, traffic volume and type.Engineering advice should beobtained for difficult sites or thoseinvolving multi-residentialdevelopments or roadways.A typical cross-section of a transversebeam for a single dwelling is shownin Figure 7. These should be usedwhere the length of the drivewayexceeds about 7 m, and spaced atabout 5 to 6 m.Concrete used in edge restraints,transverse beams, kerb and guttersand drains should have a minimumcompressive strength of 20 MPa at28 days.Pavers laid over transverse beams,edge restraints and around pits and

grates should be laid as a headercourse set in a mortar of one partPortland cement to four partswashed sand.4.3.3 DrainageSurface drainage is not normally aproblem on sloping driveways.However, inadequate or non-existentsub-surface drainage is a commoncause of failure in all pavements,particularly on sloping driveways and roads.It is very important to ascertain anylocations along the length of thedriveway where sub-surface watermay accumulate and providedrainage outlets at these locations. Ifthis is not done the water will makeits own way out, eroding bedding andjointing sand. Shunting and chippingis inevitable when this occurs.Generally a drainage system must beprovided where natural drainagethrough the sub-grade is not availableor where sub-surface water is likelyto pool or not drain freely under thepavers. Sub-surface water is likely todam at the top side of transversebeams, the lower side of edgerestraints, and at grates. Figure 8

shows typical drainage systems thatcan be adapted for these locations.4.3.4 Laying patternPavers should be laid in a 45 degreeherringbone pattern. Due to itsinterlocking action this patternprovides the best interlock andresistance to shunting. Otherpatterns are not recommended forvehicular traffic.4.3.5 MaintenanceIt is critical to maintain the jointingsand between units in order to avoidmovement that may result in pavershunting and/or chipping.This may require frequent ‘toppingup’ of the jointing sand particularlyafter periods of heavy rain.Alternatively, proprietary binders areavailable that effectively bind thesand particles together whilemaintaining the required flexibility totransfer load.Pavers around drainage pits andservice pits should be laid in headercourses and set in a cement mortar,or a concrete surround used in lieu ofthe pavers. This reduces the erosionof sand by stormwater.

Grate

Pavers in header course all round 30 mm Ø PVC pipe capped with filterfabric from base of bedding sand into pit

2 to 3 mm paverjoints filled with finewashed sand

3 % cement stabilised roadbase or concrete slab

3 % cement stabilised roadbase or concrete slab

Min. 90 mm Ø µPVC slottedsubsoil drain with filter sock,laid min. 1:100 fall 230

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Varie

s

30 mm PVC pipe capped with filtersock on lower side of road only

Plain concrete edge restraint

Clay pavers set on wet concrete or laidon 1:4 mortar (wet); provide 10 mmexpansion gaps at intervals of 10 m(straight section) or 5 m (curved section).

Discharge

(Note: PVC pipes to be provided at min. 450 cts on high side only)

Fall

Fall

Figure 8. Typical drainage systems

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5.1 ApplicationsRigid clay pavements (see Section 2,Definitions) can be utilised in a widevariety of applications including:• domestic pathways• patio areas• domestic driveways• pedestrian areas.Testing carried out by the ClayBrick and Paver Institute has shownthat clay pavers used in a rigidpavement, as described in thissection, are suitable for use whereheavy vehicle loading is expected.Testing has shown that this methodwithstands the forces that maysometimes induce movement or‘shunting’ in a flexible pavement.

5.2 Laying5.2.1 SubgradeThe considerations with regard to thesubgrade for a rigid pavement are thesame as those for a flexiblepavement.In every case the pavement designerand/or the contractor must considerall measures necessary to determinethe site conditions that will impact onthe long term performance of thepavement including, but not limited to:• Loadbearing capacity of the

subgrade (CBR) (see Section 2,Definitions)

• Subgrade drainage• Removal and replacement of

unsuitable material.

5.2.2 Base courseThe base course for a rigid pavementis a concrete slab having thefollowing properties:• Strength to be consistent with

expected traffic loading andsubgrade strength but, in generalterms, should always exceed an ultimate strength of 20 MPa.

• Thickness to satisfy predictedloadings.

• Reinforced, if required due topredicted loading.

• Finished to a smooth surface byfloating with a ‘helicopter trowel’.

• Allowed to harden overnight beforepavers are laid.

5.2.3 Paver layingPavers should be selected as to theirsuitability for the intended applicationby reference to Section 3.0. Paverscan be laid once the concrete slabbase course had hardenedsufficiently to resist deformation,usually overnight.The perimeter pavers are laid first,generally as a header course aroundthe job. They are bonded to thehardened slab either by a strongcement:sand mix (1:3 or 1:31/2) orby an adhesive.Once the perimeter pavers have beeninstalled, the main body of thepavement can be laid in the chosenpattern. For rigid pavements that willbe used for vehicular traffic it isstrongly recommended that a 45 or90 degree herringbone pattern isused.The gaps that are essential betweenpavers in a flexible pavement are notnecessary in a rigid pavement. Theycan be used if this is an aestheticrequirement but gaps are notessential to the performance of arigid pavement.It must be noted that with thissystem there is no allowance for thevariation in the depth or height of thepavers as they are being laid on ahardened concrete base. Thereforeany variation in height of the unitswill show up in the finishedpavement. Pavers that have abevelled or rounded arris candisguise this variation.

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5 . R i g i d Pavemen t s

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5.2.4 Expansion jointsExpansion must be considered whenlaying a rigid pavement. The gapsbetween pavers in a flexiblepavement allow for thermal and long-term moisture expansion of claypavers to be taken up. In a rigidpavement this does not occur.Therefore expansion joints arerequired in rigid pavements. Thepaver manufacturer should beconsulted for advice on the locationof such expansion joints.

5.2.5 Joint fillingOnce all the full and cut pavers havebeen laid it is time to fill the joints.The jointing mix is 1:3 cement:finesand mixed with sufficient water toturn it into a fluid slurry. The mixturemust be sufficiently fine so that theslurry mix can flow around any gapsin the paver and fill any voidsunderneath them.Finally once the slurry filling of thejoints is complete the surface of thepavers should be hosed down usinga high-pressure, fine mist spray toremove the excess slurry.Vehicular traffic should be preventedfrom traversing the pavement for atleast four days.

Clay paver header course,bonded to slab with 1:3 cement : sand mix, or adhesive

Clay pavers laiddirectly on hardenedconcrete slab

Concrete slab base course,‘helicopter trowel’ finish,reinforced if required

Fluid slurry jointing mix(1:3 cement : sand mix)fills voids between andunder pavers

Figure 9. Section through typical rigid clay pavement.

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6.1 Early trafficking andcleaning

If the pavement has unbound joints,traffic may use the pavementimmediately after the final pass of thevibrating plate compactor. Cleaningwith hoses or powered vacuumcleaners is not recommended duringthe first three months of thepavement use. Cleaning should be byhand broom only during this period.

6.2 Basic cleaningprinciples

6.2.1 GeneralAll pavements are subject to spillagesand soiling and a build-up of dirt andgrime. The careless use of cement-type materials during the laying of apavement can also lead to soiling.Frequent sweeping and washingreduces the effect of dirt and grimeand maintains the attractiveness ofa pavement.The removal of stains is not alwayseasy but by following these principlesand procedures the cleaning of a claypavement need not be a problem.6.2.2 Select correct cleaning

chemicalsThe first question should be: “Is theuse of chemicals necessary?” If drysweeping or washing with clean waterand a detergent fails to bring thepavement to an acceptable state ofcleanness, the answer could be “yes”.However rather than automaticallyusing an acid cleaner such as spiritsof salts (hydrochloric acid), it isessential to identify the substance tobe removed. Some useful hints tohelp you identify stains on pavementsare given later. If this is not enough,consult your supplier or a professionalknowledgeable in the subject.6.2.3 Follow correct cleaning

proceduresFollow the instructions given here oron the label of the selected proprietarycleaner. If you are inexperienced, testthe selected chemical on a small,inconspicuous patch before tacklingthe whole pavement. This could savetime and effort if, for instance, themethod used or the chemical selectedis not effective.

6.2.4 Safety precautions essentialThere are few chemicals that areentirely safe and those used forcleaning paving are often potentiallydangerous. A few elementaryprecautions are necessary:• Protect yourself against inhaling

dangerous fumes and against acidburns on your skin or in your eyes.

• Wear protective clothing.• Dilute acids in the open with the

breeze behind you.• Always add acid to water, NOT

water to acid.While working with these chemicals,keep people (especially children) andanimals out of the area. Uponcompletion ensure the chemicals aresafely stored.

6 . Ma i n t e nanc e

6.3. Removing commonstains

6.3.1 EfflorescenceThis is a powdery deposit of salts(usually white or yellow), often foundon the surface of clay pavers afterrain. The source of this stain couldbe the pavers but more often itcomes from the surroundingmaterials, for example the soil underthe pavement, or from cement (if thesoil was stabilised), or both.Efflorescence is usually harmless andcan be removed by dry brushing andhosing. However sometimes it isnecessary to follow this up with awash of weak acid or a proprietarycleaner.

6.3.2 White scumDo not confuse this with efflorescence.White scum is a thin white film onthe surface of pavers. This film isinvisible when the pavers are wet butshows up as the surface begins todry. It often appears after anattempted removal of mortar stains orafter the sanding of the joints with a‘clayey’ sand (that is, sand with ahigh clay content).White scum is particularly difficult toremove. Water, detergents or spirits ofsalts (hydrochloric acid) often do nothave any effect on it. Howeverscrubbing with a proprietary cleanerwill often improve the appearance ofpavements affected by this stain.6.3.3 Dirt and grimeFrequent sweeping and hosing willusually ensure a clean pavement. Ifthis is not enough, washing with adetergent or proprietary cleaner maybe required.

6.3.4 Vanadium stainsLight-coloured clays often containvanadium salt that may appear as ayellow, green or reddish-browndiscolouration of the pavers.Vanadium stains are naturallyoccurring and are neither permanentnor harmful and do not indicate anydefect in the pavers. Stains inexposed areas generally wash off intime but their removal can behastened by chemical treatment.A number of treatments are available.It is best to test the efficacy of thesechemicals on a test area to determinethe most suitable treatment to use.Vanadium stains can be removed by:(a) Sodium hypochloriteThe active ingredient in householdbleach and swimming pool chlorine,sodium hypochlorite is aninexpensive treatment for mild casesof vanadium staining. Spray or brushthe chemical onto the stain withoutpre-wetting, allow it to stand until thestain disappears, and then rinse off.(b) Oxalic acidProbably the best-known chemical forremoval of vanadium stains. Howeverit must be followed by a neutralisingwash. If this action is omitted (as itcommonly is) further staining of aserious nature can result. The correctprocedure is:• Mix 20 to 40g oxalic acid per litre

of water (preferably hot water).• Apply to the stained pavers without

pre-wetting.• Neutralise the oxalic acid by

applying a solution of 15 g ofwashing soda per litre of water. Donot wash off.

(c) Potassium hydroxide or sodiumhydroxide (caustic soda)Mix 150g of potassium or sodiumhydroxide per litre of water and applyto the stained pavers. Leave until thestain disappears, then wash off. Awhite residue may appear after thistreatment and this should also behosed off.(d) Noskum (proprietary cleaner)Noskum is a general-purpose claybrick and paver cleaner that rapidlyremoves the stain. Apply to dry paverand wash off after the stain isremoved.

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6.3.5 Fresh mortar stainsThe simplest way to remove wetmortar stains is to lightly cover thepavement before the mortar setshard, with clean, but slightly damp,washed sand. Sweep the sandtowards the edges of the pavement.If necessary repeat this until thesurface is almost clean. The mostimportant point to remember is thatthe sand MUST be free of clay.Follow this up with a further sweepwith dry washed sand. Any stickywet mortar residues that escaped thewet sanding will be removed. Onceagain the sand must be free of clay.One or two days after the pavementhas dried, some mortar residues maystill be visible as a faint white film.Normally this will weather away. Theappearance of efflorescence is almostcertain but do no panic, just followthe instructions above.

6.3.6 Hardened mortar stainsExperiment on a small section of thepavement with decreasingproportions of water mixed withhydrochloric acid, starting with onepart of acid to eight parts of water.Once you have determined theappropriate proportion of acid towater, or the type of proprietarycleaning solution needed, proceed asfollows:1. Slightly wet the pavement with a

fine spray of water2. Using a stiff brush, apply the acid

over approximately one squaremetre. Vigorously scrub the areasstained with mortar. Whenscrubbing is not sufficient loosenthick mortar patches with a hardimplement such as a steel scraper.Work on the mortar stain until it isdissolved.

3. Give the area a good hose-down. Apressurised water spray unit isuseful for this job.

Repeat 1 to 3 until the wholepavement has been cleaned.A final rinse of the pavement witha high-pressure water jet is oftenbeneficial. However there are somepavers that could be damaged by theoveruse of high-pressure water jets.Care must also be taken not toremove sand from the paver joints.

6 . Ma i n t e nanc e

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6.3.7 Fungi, moulds, moss andlichens

These are common, particularly in shady or damp parts of thepavement. They sometimes appearas localised dark stains or patches ofgreen, giving a dirty and unsightlyappearance.Alternatively these growths may addto the appearance of the pavement.They will not damage the pavementbut may cause it to become slippery.To remove these growths, vigorouslybrush the effected area when it isdry. High-pressure water may also beused. Although the surface may nowappear to be completely cleaned it isnecessary to sterilise the area with apoison or a strong fungicide thatshould be allowed three to four daysto act. Blue crystals (coppersulphate) is one such poisonwhereas sodium hypochlorite (liquidchlorine or bleach) and formaldehydeare fungicides. Other proprietarybrands are available from plantnurseries. The surface should bebrushed again when dry.

Warning: Some of the poisons infungicides may discolour thepavement. Check their effect on asmall part of the pavement beforeproceeding to clean the wholearea. Pay attention to nearbygarden plants or lawn, especiallyon the lower side of the paved areabeing treated.

6.3.8 Oil, bitumen and tarThese stains usually need twotreatments with a commercialemulsifying agent. First, mix theemulsifier with kerosene to removethe stain. Then clean the keroseneoff with the emulsifier mixed onlywith water.When dealing with petroleum asphaltand bituminous emulsion, scrape offthe excess material and scrub thesurface with scouring powder andwater. Chilling the surface with ice orsolid carbon dioxide can causebrittleness in the asphalt and assistremoval.For petrol or lubricating oil stains,free oil must be mopped upimmediately with an absorbentmaterial such as paper towelling.Wiping should be avoided as itspreads the stain and tends to forcethe oil into the pavement. Hardenedoil must be scraped off.The area affected should then becovered with a dry absorbentmaterial such as diatomaceous earth,fine white clay, kaolin or whiting andthe procedure repeated until there is no further improvement.Subsequently use detergent to cleanup, and rinse well with clean water.

6.3.9 Food stains and tyre marksScrub with a full-strength commercialdetergent and rinse well.

6.3.10 Chewing gumIn large areas, wire brushes free fromrust should remove the majority ofchewing gum. This may requireseveral attempts. Careful applicationof high-pressure water jets can alsobe successful.For smaller areas freeze each piece ofchewing gum with a carbon dioxideaerosol or dry ice. The chewing gumcan then be chipped off with ascraper or chisel.

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1. AS/NZS 4455:1997 Masonry Units and Segmental Pavers, Standards Australia,Sydney, 1997

2. AS/NZS 4456:1997 Masonry Units and Segmental Pavers – Methods of Test,Standards Australia, Sydney, 1997

3. AS/NZS 4586:1999 Slip Resistance Classification of New Pedestrian SurfaceMaterials, Standards Australia, Sydney, 1999

4. AS/NZS 4456.3:1997 Method 3, Determining Dimensions, Part A Determinationof Cumulative Dimensions, Standards Australia, Sydney, 1997

5. AS/NZS 4456.5:1997 Determining Breaking Load of Segmental Paving Units,Standards Australia, Sydney, 1997

6. AS/NZS 4456.9:1997 Determining Abrasion Resistance, Standards Australia,Sydney, 1997

7. AS/NZS 4456.10:1997 Determining Resistance to Salt Attack, StandardsAustralia,Sydney, 1997

8. AS/NZS 4586:1999 Appendix A, Slip Resistance Classification of New PedestrianSurface Materials: Wet Pendulum Test Method, Standards Australia, Sydney, 1999

7 Re f e r e n c e s