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TECH SPECTECH SPECN U M B E R • 15

Tech Spec 15 – A Guide for The Construction of Mechanically Installed Interlocking Concrete Pavements

IntroductionThis guide is intended to assist design professionalsin the developing a construction specification for themechanical installation of interlocking concretepavement. The core is the Quality Control Plan thatrequires a high level of planning and detail for execut-ing large-scale projects. When refined into a projectspecification, it should be a tool to obtain a commit-ment to its requirements by the General Contractor(GC), paver installation subcontractor, manufacturer,and facilitate coordination among them. The ultimateoutcome is increased assurance for owners of largepaved facilities.

The set of contractual relationships among theowner, Engineer, GC, subcontractors, and manufactur-ers (suppliers) will vary with each project. This guideassumes that an Engineer works for the owner whohires a GC to build the project. The GC subcontracts toa company specializing in interlocking concretepaving. The subcontractor purchases pavers from apaver manufacturer. The Engineer or other employeesworking for the owner inspect and accept the paving.

Construction specifications in North America fol-low various formats. A common one is set forth by the

© 2003 ICPI Tech Spec No. 15 • Interlocking Concrete Pavement Institute

Construction Specifications Institute (CSI) calledMasterFormat (2) and this guide is written to fit thisformat. Specifications using the CSI format sectionshave three parts; General, Products, and Execution.This guide is divided into these three parts to assist inwriting each.

1.0 PART 1—GENERALThis specification guide includes the installation ofinterlocking concrete pavers with mechanical equip-ment, bedding and joint sand, and optional joint sandstabilization materials. ICPI Tech Spec 11,Mechanical Installation of Interlocking ConcretePavements (2) should be consulted for additionalinformation on design and construction with thispaving method. Other references will includeAmerican Society for Testing and Materials and theCanadian Standards Association for the concretepavers, sands, and joint stabilization materials. Othersubcontractors or the GC provides the base,drainage, and earthwork.

1.1 DefinitionsThis guide sets forth definitions so all project partic-ipants use the same terms within the specification:

Figure 1. Mechanical installation of interlocking concrete pavements (left) and permeable units (right) isseeing increased use in industrial, port, and commercial paving projects to increase efficiency and safety.

2 Tech Spec 15—A Guide for the Construction of Mechanically Installed Interlocking Concrete Pavements

Base: Layer(s) of material under the wearing courseand bedding course.Bedding course: A screeded sand layer on whichthe pavers are bedded.Bundle: Paver clusters stacked vertically, boundwith plastic wrap and/or strapping, and tagged forshipment to and installation at the site. Bundles ofpavers are also called cubes of pavers. Concretepaver bundles supplied without pallets are strappedtogether for shipment then delivered and transportedaround the site with clamps attached to variouswheeled equipment. The Subcontractor may providesome wooden pallets at the site to facilitate move-ment of bundles. See Figure 2.Chamfer: A 45o beveled edge around the top of apaver unit nominally 2 to 6 mm wide.Cluster: A group of pavers forming a single layerthat is grabbed, held, and placed by a paver-layingmachine on a screeded sand bedding course.Interlock: Frictional forces between pavers whichprevent them from rotating, or moving horizontallyor vertically in relation to each other.Joint: The space between concrete pavers typicallyfilled with sand.Joint filling sand: Sand used to fill spaces betweenconcrete pavers.Joint sand stabilizer: Liquid applied materials pen-etrate the in-place joint sand or an additive is mixeddry with sand prior to filling the joints. Joint sandstabilization materials are optional and may be ofvalue in certain applications.Laying face: Working edge of the pavement wherethe laying of pavers occurs.Wearing course: Surfacing consisting of interlockingconcrete pavers and joint sand on a sand bedding layer.Wearing surface: The top surface that contacts traf-fic whose edges are typically chamfered.

1.2 SubmittalsThe following is submitted by the GC to theEngineer for review and approval:1. 14 pavers with the date of manufacture marked on

each. These can be made available for testing. 2. Manufacturer’s catalog cut sheets and produc-

tion mold drawings.3. The stitching pattern for joint clusters when the

pavers are placed on the bedding sand.4. 6 lbs. (3 kg) bedding sand.5. 6 lbs. (3 kg) joint filling sand.6. Manufacturer’s catalog cut sheets of joint stabi-

lization material (if specified).7. 1 quart (liter) joint sand stabilizer or joint sand

additive (if specified), or 2 lbs. (1 kg) joint sandstabilizer additive.

8. Quality Control Plan.

1. 3 Quality Control PlanThe GC provides the Engineer, paver installation sub-contractor, and manufacturer with a Quality ControlPlan describing methods and procedures that assure

all materials and completed construction submittedfor acceptance conform to contract requirements.The Plan applies to specified materials manufacturedor processed by the GC, or procured from subcon-tractors or manufacturers. The GC meets the require-ments in the Plan with personnel, equipment, suppliesand facilities necessary to obtain samples, performand document tests, and to construct the pavement.

The GC performs quality control sampling, testing,and inspection during all phases of the work, or dele-gates same, at a rate sufficient to ensure that the workconforms to the GC requirements. The Plan is imple-mented wholly or in part by the GC, a subcontractor,manufacturer, or by an independent organizationapproved by the Engineer. Regardless of implementa-tion of parts of Plan by others, its administration,including compliance and modification, remains theresponsibility of the GC.

The Plan should be submitted to the Engineer atleast 30 days prior to the start of paving. The GC,paving Subcontractor, and Manufacturer then meetwith the Engineer prior to start of paving to decidequality control responsibilities for items in the Plan.The Plan includes:1. Quality Control organization chart with the

names, qualifications, and contact information

Figure 2. Bundles of ready-to-install pavers for set-ting by mechanical equipment. Bundles are oftencalled cubes of pavers.

Development andimplementation ofthe Quality ControlPlan is a joint effortby the project engineer, the GC,the paver installationsubcontractor, mate-rial suppliers, andtesting laboratories.

Tech Spec 15—A Guide for the Construction of Mechanically Installed Interlocking Concrete Pavements 3

of responsible personnel, and each individual’sarea of responsibility and authority.

2. A listing of outside testing laboratoriesemployed by the GC and a description of theservices provided and the tests performed byGC personnel.

3. Preparation and maintenance of a Testing Plancontaining a listing of all tests to be performedby the GC and the frequency of testing.

4. Procedures for ensuring that tests are conductedaccording with the Plan including documenta-tion and steps for taking corrective actions ifmaterials do not meet criteria for meeting thestandards.

5. The paver installation Subcontractor’s methodstatement.

1.3.1 Quality Control Plan ElementsTesting—Independent testing laboratories typicallyare involved in testing sand and concrete pavers.They should have in-house facilities for testing bed-ding and joint sands. The laboratory should providea letter certifying calibration of the testing equip-ment to be used for the specified tests. Uponapproval of the Engineer, the laboratory performstesting of sand and paver samples prior to com-mencement of paving to demonstrate their ability tomeet the specified requirements.

Paver Manufacturer—The paver manufacturer pro-vides evidence of capability to manufacture interlock-ing concrete pavers. Information may include a histo-ry of supplying projects of similar application and size,with project references and contact information inwriting for verification. Personnel and qualificationsmay be part of the submission. The project history andreferences should demonstrate ability to perform thepaver installation and related work indicated in theplans and specifications to the satisfaction of theEngineer.

The submission should include a description of themanufacturer’s ability to make, cure, package, store,and deliver the concrete pavers in sufficient quantitiesand rates without delay to the project. Evidence caninclude diagrams and photos showing the number andstacked height of pavers on pallets, or in bundles with-out pallets, banding of the pavers, use and placementof plastic wrap, pallet dimensions and construction,and overall loaded pallet or bundle dimensions.

Transportation planning for timely delivery ofmaterials is a key element of large interlocking con-crete pavement projects. Therefore, the manufacturershould include a storage and retrieval plan at the facto-ry and designate transportation routes to the site. Inaddition, there is a description of the transportationmethod(s) of pavers to the site that incurs no shifting ordamage in transit that may result interference with anddelay of their installation. The manufacturer’s portionof the quality control plan includes typical daily pro-duction and delivery rates to the site for determining

on-site testing frequen-cies.

A key component isthe plan is a methodstatement by the manu-facturer that demon-strates control of paverdimensional tolerances.This includes a plan for managing dimensionaltolerances of the paversand clusters so as to not interfere with theirplacement by pavingmachine(s) during me-chanical installation. Thecontents of this planinclude, but are not lim-ited to the following:1. Drawings of the

m a n u f a c t u r e r ’smold assembly in-cluding overall dimensions, pattern, dimensionsof all cavities including radii, spacer bars, andthe top portion of the mold known as a head orshoe.

2. If a job is large enough to require more than onemold, the actual, measured dimensions of allmold cavities need to be recorded prior to man-ufacture of concrete pavers for this project. Thisis needed because the new or used productionmolds may vary in overall cluster size. Mixingpavers from a larger mold with a smaller moldmay cause installation problems.

3. Molds will wear during manufacture of pavers.Production mold wear is a function of the con-crete mix, mold steel, and production machinesettings. A manufacturer can control by rotatingthe molds through the production machine(s) onan appropriate schedule so that all molds expe-rience approximately the same amount of wearon the inside of the mold cavities. The manufac-turer can also hold a larger mold out of the rota-tion until the smaller (newer) molds wear suffi-ciently to match its size. An initial, baselinemeasurement of all mold cavities provides start-ing point for documenting and planning formold cavity growth.

4. The manufacturer should state the number ofmolds and a mold rotation plan with a statementof how often mold cavities will be measuredduring production, as well as the method ofrecording and reporting, and the criteria formold rotation. While mold cavity wear will varydepending on a number of factors approximate-ly 0.1 mm wear of the mold cavities can typi-cally be expected for every 10,000 cycles.Production records for each bundle should showthe date of manufacture, a mix design designa-

Figure 3. A cluster of pavers (or layer) is grabbedfor placement by mechanical installation equip-ment. The pavers within the cluster are arranged in the final laying pattern as shown under theequipment.


tion, mold number, mold cycles, and sequentialbundle numbers.

A large variation in cluster size can reduce mecha-nized paving productivity, thereby increasing costs andlengthening production schedules. Extreme variationsin cluster size can make mechanical installationimpossible. Following certain procedures during man-ufacture will reduce the risk of areas of cluster sizesthat will not fit easily against already placed clusters.Such procedures include (1) consistent monitoring ofmold cavity dimensions and mold rotation duringmanufacture, (2) consistent filling of the mold cavities,(3) using a water/cement ratio that does not cause theunits to slump or produce “bellies” on their sides afterthe pavers are released from the mold, and (4) moder-ating the speed of production equipment such thatpavers are not contorted or damaged. All of these fac-tors are monitored by regular measurement of the clus-ter sizes by the manufacturer and the subcontractor.

It is essential that at least two identical jigs be usedto check cluster dimensions, one in the paver produc-tion plant and the second on the job site. The manu-facturer should provide these two jigs. The jigs shouldcheck the overall length and width of assembled,ready-to-place clusters. The sampling frequencyshould provide at least a 95% confidence level and thefrequency should be agreed upon in writing by theowner, GC, Subcontractor, and manufacturer.

In no case should the “stack test” be used as ameans for determining dimensional consistency. Thistest consists of stacking 8 to 10 pavers on their sides toindicate square sides from a stable column of pavers,or leaning and instability due to bulging sides or “bel-lies.” It is a test for checking for bellied pavers, there-by providing a quick field determination of the possi-bility of pavers that may not be capable of beinginstalled with mechanical equipment. It is an earlywarning test to indicate the possibility of installationproblems from bellied pavers (3). The stack test is notreliable and should not be substituted for actuallymeasuring the pavers to see if they meet specified tol-erances.

The mold pattern, the mold rotation plan, and theanticipated mold wear information should be reviewedand submitted by both the manufacturer and the paverinstallation subcontractor. This is necessary to insurethat they have a common understanding and expecta-tions.

The subcontractor’s quality control proceduresinclude, but are not limited to the following:1. Demonstrate past use of mechanical installation

by key staff on single projects having a similarapplication and loads.

2. Provide mechanical installation project historyincluding references in writing with contactinformation for verification. The history and ref-erences should demonstrate ability to performthe paver installation and related work indicatedin the plans and specifications to the satisfaction

of the Engineer.3. List the experience and certification of field per-

sonnel and management who will execute thework.

4. Provide personnel operating mechanical instal-lation and screeding equipment on job site withprior experience on a job of similar size.

5. Report methods for checking slope and surfacetolerances for smoothness and elevations.

6. Show a means for recording actual daily pavingproduction, including identifying the site loca-tion and recording the number of bundlesinstalled each day.

7. Show diagrams of proposed areas for storingbundles on the site, on-site staging of storageand use, and the starting point(s) of paving theproposed direction of installation progress foreach week of paving. These should be made inconsultation with the GC as site conditions thateffect the flow of materials can change through-out the project.

8. Provide the number of paver installationmachines to be present on the site, and antici-pated average daily installation rate in squarefeet (m2).

9. Provide a diagram, including dimensions, of thetypical cluster or layer to be used.

10. Provide a diagram of the stitching pattern usedto join clusters including a statement about orillustration of the disposition of half-pavers, ifany.

12. The subcontractor and manufacturer are encour-aged to hold memberships in the InterlockingConcrete Pavement Institute.

1.4 Mock UpA test area or mock up is necessary to demonstratecompetence and efficiency of the paver installationsubcontractor, and to serve as an example of compli-ance with the construction documents. This area isconstructed prior to starting full paving activities.The mock-up area should be at least 1,000 sf (100m2). The mock-up should be retained and used as astandard for judging the remainder of the work.When accepted by the Engineer, the mock-up shouldremain in an undisturbed condition for periodic ref-erencing against the work in progress. At the time ofsubstantial completion of paving, the mock-up maybecome part of completed work. At a minimum, themock-up should demonstrate the items listed below:1. Efficient, uninterrupted use of all mechanical

installation and screeding equipment. 2. The quality of workmanship that will be pro-

duced for the remainder of the project includingcut pavers at edges, paver border courses, paverpattern(s) in the field of pavement, laying faceconfiguration, cluster placement and offsets,stitching of half or full pavers among clusters,pattern direction, typical surcharge and com-


paction depth of bedding sand and pavers, typi-cal joint widths, joint lines, joints filled withconsolidated sand, and typical application ofsand stabilizer, if specified.

3. A demonstration of the typical methods forinspection and acceptance of existing site condi-tions, cleaning of base surfaces in preparationfor paving, dimensional control procedures forthe clusters, placement of the bedding sand,placement of the pavers, initial compaction ofthe pavers into the bedding sand, stitching andadjusting of pavers, complete installation of thejoint sand and fullness of joints, cleaning of thepaver surface, paver cutting, site clean up, end-of-day installation and site conditions, and tech-niques for protecting materials and work frominclement weather.

1.5 Delivery, Storage And HandlingAll required testing for products or materials shouldbe completed and the results submitted in writing forapproval by the Engineer prior to delivery of thatproduct or material to the site. Materials shouldarrive at the site with no damage from hauling orunloading, and be placed on the site according theQuality Control Plan. Each bundle of pavers shouldbe marked with a weatherproof tag that includes themanufacturer, the date of manufacture, the moldnumber, the project (or project phase), for which thepavers were manufactured, and the sequential bun-dle number. The sequential number should beapplied to the bundle based on the manufacturingrun for the job, not on the order of delivery. Anybreaks in numbering should be reported immediate-ly by the manufacturer to the Subcontractor,Contractor, and Engineer in writing.

Bedding and joint sand delivered to the site shouldbe covered and protected from wind and rain.Saturated bedding cannot be installed because it willnot compact. Environmental conditions precludinginstallation are heavy rain or snowfall, frozen granularbase, frozen sand, installation of pavers on frozen sand,and conditions where joint sand may become damp soas to not readily flow into the joints.

2.0 PART 2—PRODUCTS

2.1 Concrete PaversIn North America, concrete pavers should meetASTM C 936 (4) in the United States or CSAA231.2 (5) in Canada. Besides supplier information,the color(s), plus the exact length, width, and heightdimensions of the units should be stated. Spacer barsare required for mechanical installation and are notincluded in the overall dimensions. Spacer barsshould protrude from the side of the paver a distanceequal to the minimum allowable joint width. SeeFigure 4.

ASTM C 936 includes the following requirements:1. Absorption: 5% average with no individual unit

greater than 7% per ASTM C 140 (6).2. Abrasion resistance: No greater volume loss

than 0.92 in.3 (15 cm3) per 7.75 in.2 (50 cm2)and average thickness loss shall not exceed0.118 in. (3 mm) when tested in accordancewith Test Method ASTM C 418 (7).

3. Compressive strength: Average 8,000 psi (55MPa), with no individual unit below 7,200 psi(50MPa) when tested according to ASTM C140. If whole pavers are tested, an adjustmentfactor should be multiplied by the tested com-pressive strength per the table below to compen-sate for the height of the unit (8):

If cut, cube-shaped coupons are tested, use the 55MPa and 50 MPa values regardless of the initialdimensions of the paver from which the coupon wascut.

CSA A231.2 includes the following requirements:1. Compressive strength: Average 7,200 psi (50

MPa) at 28 days with no individual unit lessthan 6,500 psi (45 MPa) . The CSA test methodfor compressive strength tests a cube-shapedspecimen. This method eliminates differences incompressive strength resulting from variousthicknesses of pavers.

2. Freeze-thaw deicing salt durability: averageweight loss not exceeding 200 g/m2 of surfacearea after 25 cyclesor 500 g/m2 after 50cycles. This require-ment can be omittedfor projects not sub-ject to deicing salts.However, the testmethod and criteriashould be applied toall projects in NorthAmerica subject todeicing salts, and notjust those in Canada.(The freeze-thaw testand requirements inASTM C 936 do notinclude deicing saltdurability. Therefore,it is not a requirementin this guide specifi-cation.)

Figure 4. Spacer bars are small nibs on the sidesof the pavers that provide a minimum joint spac-ing into which joint sand can enter.

3 1/8 in. (80 mm) 1.18

4 in. (100 mm) 1.24

4 3/4 in. (120 mm) 1.33

NominalThickness

Multiply Tested Compressive Strength by


The CSA freeze-thaw deicing salt test for freeze-thaw durability requires several months to conduct.Often the time between manufacture and time ofdelivery to the site is a matter of weeks or even days.In such cases, the Engineer may consider reviewingfreeze-thaw deicing salt test results from pavers madefor other projects with the same mix design. These testresults can be used to demonstrate that the manufac-turer can meet the freeze-thaw durability requirementsin CSA A231.2. Once this requirement is met, theEngineer should consider obtaining freeze-thaw deic-ing salt durability test results on a less frequent basisthan stated here.

Sometimes the project schedule requires thatpavers be delivered to a job site prior to 28 days. If thatis the case, the manufacturer can develop strength-age

curves to demonstrate the relationship of compressivestrength at 3, 7, or 14 days with respect to what thestrength will be at 28 days. This should be submittedto the Engineer before the start of the project. Under noconditions should the pavers be opened to containerhandling equipment prior to achieving their 28-daycompressive strength.

A key aspect of this guide specification is dimen-sional tolerances of concrete pavers. For length andwidth tolerances, ASTM C 936 allows ±1/16 in. (±1.6mm) and CSA A231.2 allows ±2 mm. These areintended for manual installation and should be reducedto ±1.0 mm (i.e., ±0.5 mm for each side of the paver)for mechanically installed projects, excluding spacerbars. Height should not exceed ±1/8 in. (±3 mm) fromspecified dimensions. Dimensions should be checked

with calipers.

2.1.1 Quality AssuranceTestingAn independent testing laborato-ry typically conducts tests on thepavers and sands. The GeneralConditions of the Contract (typi-cally found in Division 01 of theproject manual) may specifywho pays for testing. It is recom-mended that the GC be responsi-ble for all testing. All test resultsshould be provided to theEngineer, GC, subcontractor,and manufacturer, and withinone working day of completionof the tests. All should be noti-fied immediately if any testresults do not meet those speci-fied. The independent testing isintended for project qualityassurance. It does not take theplace of any testing required forquality control during produc-tion.

For the initial testing frequen-cy, randomly select 14 full-sizepavers from initial lots of 25,000sf (2,500 m2) manufactured forthe project, or when any changeoccurs in the manufacturingprocess, mix design, cement,aggregate or other materials.25,000 sf (2,500 m2) approxi-mates an 8-hour day’s productionby one paver manufacturingmachine. This can vary with themachine and production facilities.This quantity and the sample sizeshould be adjusted according tothe daily production or deliveryfrom the paver supplier. Consult

Grading Requirements for Bedding Sand

ASTM C 33 CSA A23.1-FA1

Sieve Size Percent Passing Sieve Size Percent Passing

3/8 in.(9.5 mm) 100 10 mm 100

No. 4 (4.75 mm) 95 to 100 5 mm 95 to 100

No. 8 (2.36 mm) 85 to 100 2.5 mm 80 to 100

No. 16 (1.18 mm) 50 to 85 1.25 mm 50 to 90

No. 30 (0.600 mm) 25 to 60 0.630 mm 25 to 65

No. 50 (0.300 mm) 10 to 30 0.315 mm 10 to 35

No. 100 (1.150 mm) 2 to 10 0.160 mm 2 to 10

No. 200 (0.075 mm) 0 to 1 0.075 mm 0 to 1

Grading Requirements for Joint Filling Sand

ASTM C 144 CSA A179

Sieve Size Percent Passing Sieve Size Percent Passing

No. 4 (4.75 mm) 100 5 mm 100

No. 8 (2.36 mm) 95 to 100 2.5 mm 90 to 100

No. 16 (1.18 mm) 70 to 100 1.25 mm 85 to 100

No. 30 (0.600 mm) 40 to 75 0.630 mm 65 to 95

No. 50 (0.300 mm) 10 to 35 0.315 mm 15 to 80

No. 100 (0.150 mm) 2 to 15 0.160 mm 0 to 35

No. 200 (0.075 mm) 0 to 10 0.075 mm 0 to 10

Table 1

Table 2

Note: ASTM C33 does not specify the percent passing the No. 200 (0.075 mm) sieve. CSA A23.1allows up to 3% passing the No. 200 (0.075 mm) sieve. The above grading requirement for thissieve are modifications of these standards.

Note: The allowable maximum percent passing the No. 200 (0.075 mm) sieve may need to bedecreased to allow for penetration of joint sand stabilizer. Test penetration depths on the sitemock up area of paving.


the paver supplier for a more precise estimate of dailyproduction output. Initial sampling and testing ofpavers should be from each day’s production at theoutset of the project to demonstrate consistency amongaggregates and concrete mixes.

Testing includes five pavers for dimensional varia-tions, three pavers for density and absorption and threepavers for compressive strength (and three pavers forfreeze-thaw durability if required). If all tested paverspass all requirements for a sequence of 125,000 sf(12,500 m2) of pavers, then reduce the testing frequen-cy for each test to three full-sized paver from each25,000 sf (2,500 m2) manufactured. If any pavers failany of these tests, then revert to the initial testing fre-quency.

125,000 sf (12,500 m2) approximates five days ofproduction by one paver manufacturing machine. Thiscan vary with the machine and production facilities.This quantity and the sample size should be adjustedaccording to the daily production or delivery from thepaver supplier. Consult the manufacturer for a moreaccurate estimate of the five-day production output.

The entire bundle of pavers from which the testedpaver(s) were sampled should be rejected when any ofthe individual test results fails to meet the specifiedrequirements. Additional testing from bundles manu-factured both before and after the rejected test sampleshould be performed to determine, to the satisfactionof the Engineer, the sequence of the paver productionrun that should be rejected. Any additional testingshould be performed at no cost to the owner. Theextent of nonconformance of test results may necessi-tate rejection of entire bundles of pavers or larger quan-tities. The Engineer may need to exercise additionalsampling and testing to determine the extent of non-conforming clusters and/or bundles of pavers, and base

rejection of clusters of entire bundles on those findings.

2.2 Bedding SandBedding sand gradation should conform to ASTM C33 (10) or CSA A23.1 (11) as appropriate with mod-ifications as noted in Table 1. Supply washed, natu-ral or manufactured, angular sand.

At the start of the project, conduct gradation testsper ASTM C 136 (12) or CSA A23.2A (13) for every25,000 sf (2,500 m2 ) of wearing course or part there-of. Testing intervals may be increased upon writtenapproval by the Engineer when sand supplier demon-strates delivery of consistently graded materials.

The Lilley-Dowson sand degradation test (9)should be conducted to assess the durability of the bed-ding sand in port, airport, and industrial pavementswhere wheel loads exceed those typical to highways.The test is recommended for streets if the anticipated18-kip (80 kN) equivalent single axle load (ESALs)exceeds 1.5 million for the design life of the pavement.Figure 5 shows the test apparatus and Figure 6 illus-trates its cross section.

The test method is as follows. Obtain a representa-tive sand sample weighing 3 lbs. (1.5 kg). The sampleis dried for 24 hours or to a constant weight in a ther-mostatically controlled oven at a temperature of 240-250o F (115-120o C). Obtain three sub-samples eachweighing 1lb. (0.5 kg) by passing the main sampleseveral times through a riffle box. Conduct a sieveanalysis test in accordance with ASTM C 136 on eachsample. Remix each sub-sample and place in a 5 in.(125 mm) diameter liter nominal capacity porcelain jartogether with two 25 mm diameter steel ball bearingseach with a mass of 0.16 ±01 lb. (75 ±5 g). Place eachjar on a bottle roller to rotate at 50 rpm for a period ofsix hours. Repeat the sieve analysis on each sub-sam-ple. Report the individual and mean sieve analysis. The

Figure 5. Ceramic bottles used in the Lilley-Dowson test forassessing the durability of bedding sand under heavy wheelloads (9).

Bottle

SteelBalls

Drive Roller

Aggregate

Figure 6. A cross-section of the bottle rolling apparatus(9).


samples shall comply if the maximum averageincrease in the percentages passing each sieve and themaximum individual percent passing are as follows:

Sieve Size Max. Increase Max. % PassingNo. 200 (0.075 mm) 2% 2%No. 100 (0.150 mm) 5% 15%No. 50 (0.300 mm) 5% 35%

Repeat the test for every 250,000 sf (25,000 m2) ofbedding sand or when there is a change in sand source.

2.3 Joint Filling SandJoint sand gradation should conform to ASTM C144 (14) or CSA A179 (15) with modifications asnoted in Table 2. Supply washed, manufactured,angular sand.

At the start of the project, conduct gradation test perfor every 250,000 sf (2,500 m2) of concrete paverwearing course. Testing intervals may be increasedupon written approval by the Engineer when the sandsupplier demonstrates delivery of consistently gradedmaterials.

2.4 Joint Sand StabilizerStabilization materials for joint filling sand areoptional and there are two categories of materials.These are liquid penetrating and dry mix formulasincluding materials mixed with joint sand and acti-vated with water. Both categories of materialsachieve early stabilization of joint sand. Liquid pen-etrating materials should have 24-hour cure time andbe capable of penetrating the joint sand to a mini-mum depth of 1 in. (25 mm) prior to curing. Dry mixorganic or polymer additives combine with jointsand prior to placing it in the joints. These materialstypically cure in a few hours after activation withwater. If the need for joint sand stabilization isdetermined, the application rate and method shouldbe established on the mock-up area of paving.

3.0 PART 3 – EXECUTION3.1 ExaminationThe elevations and surface tolerance of the base

determine the final sur-face elevations of con-crete pavers. The paverinstallation subcontrac-tor cannot correct defi-ciencies in the base sur-face with additional bed-ding sand or by othermeans. Therefore, thesurface elevations of thebase should be checkedand accepted by the GCor designated party, withwritten certification tothe paving subcontrac-tor, prior to placing bed-

ding sand and concrete pavers. The GC should inspect, accept and certify in writ-

ing to the subcontractor that site conditions meet spec-ifications for the following items prior to installation ofinterlocking concrete pavers:1. Subgrade preparation, compacted density and

elevations conform to specified requirements.2. Geotextiles or geogrids, if applicable, placed

according to drawings and specifications.3. Aggregate, cement-treated, asphalt-treated, con-

crete, or asphalt base materials, thicknesses, com-pacted density, plus surface tolerances and eleva-tions that conform to specified finished surfacerequirements.

Heavy-duty paving will often have high strengthbase material such as cement stabilized base, concreteslabs, or asphalt. Even though these materials arebeing used as a base layer, the construction specifica-tion must require installation of the top layer of thesematerials to typical surface finish tolerances. Asphaltcrews, for example, may use different elevation controlmethods for base lifts than they do for top lifts. Thebase lift methods often are not as tightly controlled forgrade as variations can be made up by the top lift ofasphalt. If a base lift is directly under the bedding sand,a top lift may not be present, nor close surface toler-ances normally expected from a top lift. Compensationfor variations in base lift elevations must not be fromadding more bedding sand. Special care should also betaken at edge contacts to ensure that asphalt, or othermaterials are installed deeply enough to allow a com-plete paver and sand section above.

Edge restraints should be in place before pavers areinstalled. Some projects can have completed edgerestraints with paving activity near them while the con-struction schedule dictates that the opposite side of thearea may see ongoing construction of edge restraints.In such cases, the GC should propose an edge restraintinstallation schedule in writing for approval by theEngineer. All bollards, lamp posts, utility covers, firehydrants and like obstructions in the paved area shouldhave a square or rectangular concrete collar. The loca-tion, type, and elevations of edge restraints, and anycollars around utility structures, and drainage inletsshould be verified with the drawings.

Likewise, verification of a clean surface of the basesurface is required, including no standing water orobstructions prior to placing the bedding sand and con-crete pavers. There will be a need to provide drainageduring installation of the wearing course and jointsand by means of weep holes or other effective methodper the drawings, temporary drains into slot drains,dikes, ditches, etc. to prevent standing water on thebase and in the bedding sand. These may be indicatedon the drawings. If not, they should be a bid item pro-vided by the GC from the paver installation subcon-tractor. All locations of paver contact with other ele-ments of the work should be inspected, including weep

Figure 7. Maintaining an angular laying face thatresembles a saw-tooth pattern facilitates installa-tion of paver clusters.


holes, drain inlets, edge restraints, concrete collars,utility boxes, manholes, and foundations. Verify thatall contact surfaces with concrete pavers are vertical.

Areas where clearances are not in compliance, orwhere the design or contact faces at adjacent pave-ments, edges, or structures are not vertical should bebrought to the attention of the GC and Engineer inwriting with location information. The GC should pro-pose remediation method(s) for approval by theEngineer. All such areas shall be repaired prior to com-mencing paver installation. Alternately, the GC maypropose a repair schedule in writing for approval bythe Engineer.

3.2 InstallationThere are a variety of ways to install interlockingconcrete pavements. The following methods are rec-ommended by ICPI as best practices. Other methodsvary mainly in the techniques used for compactionof the pavers and joint sand installation. ICPI rec-ommends using a vibrating plate compactor on con-crete pavers for consolidation of bedding and jointsands. Other methods that have been used under spe-cific project conditions including vibrating steelrollers and applying water to move sand into thejoints.

The bedding sand installation begins by screeding auniform layer to a maximum 1 in. (25 mm) thickness.Maintain a uniform thickness within a tolerance of ±1/4in. (±6 mm). Allow for surcharge due to compaction ofthe pavers, typically 3/16 in. (5 mm). For example, if thepavers are 31/8 in. (80 mm) thick, the elevations of thebase surface should be 41/8 in. (105 ± 5 mm) below thefinish elevation of the pavement. The exact amount ofsurcharge will vary depending on local sands and thisis determined in the mock up. Do not fill depressionsin the surface of the base with bedding sand, as theymay reflect to the paver surface in a few months.

Variations in the surface of the base must berepaired prior to installation of the bedding sand. Thescreeded bedding course should not be exposed to footor vehicular traffic. Fill voids created by removal ofscreed rails or other equipment with sand as the bed-ding proceeds. The screeded bedding sand courseshould not be damaged prior to installation of thepavers. Types of damage can include saturation, dis-placement, segregation, or consolidation. The sandmay require replacement should these types of damageoccur.

Installation of the concrete pavers starts with secur-ing string lines, laser lines, or snapping chalk lines onthe bedding course. These or other methods are accept-able to maintain dimensional control in the direction ofpaving. These lines are typically set at 50 ft. (15 m)intervals for establishing and maintaining joint lines atmaximum allowable width of clusters. The installationsubcontractor will determine exact intervals for lines.

A starting area may need to be placed by handagainst an existing curb. This will establish coursing,

squareness of the pattern, and offset of the mechanicalinstalled layers. Interlocking patterns such as herring-bone patterns are recommended for port pavements.The orientation of the pattern is typically governed bythe site operational layout and orientation should beincluded in the drawings. An angular laying face (orfaces) should be maintained with the laid clusters cre-ating a saw tooth pattern. This will facilitate rapidinstallation and adjustment of clusters as laying pro-ceeds. Figure 7 illustrates this pattern for the layingface.

Bundles of pavers are positioned by the laying faceand machines pick from them as laying proceeds.Straight joint lines are maintained by adjusting clustersand pavers with rubber hammers and pry bars. If thecluster pattern is shipped to the site with half-sizedpaver units, adjust their locations, or remove them andfill openings with full-sized pavers so that each clusteris stitched and interlocked with adjacent clusters intothe designated laying pattern. There may be paver lay-ers that do not require the removal of half pavers if thelayers are installed in a staggered fashion. The result-ing final pattern should be illustrated in the methodstatement in the Quality Control Plan. As paving pro-ceeds, hand install a string course of pavers around allobstructions such as concrete collars, catchbasins/drains, utility boxes, foundations, and slabs.

Pavers are typically cut with powered saws. Cuttingpavers with mechanical (non-powered) splitters for

Figure 8. Edge pavers are saw cut to fit against a drainage inlet.


industrial pavement is an acceptable method as long asthe resulting paver meets project tolerances for square-ness and surface variations, as well as specified jointwidths. Do not allow concrete materials emitted fromcutting operations to collect or drain on the beddingsand, joint sand, or in unfinished joints. Figure 8 showsa cutting with a dust collection system to prevent con-tamination of surfaces. If such contact occurs, removeand replace the affected materials.

Cut pavers should be no smaller than one-third of afull paver and all cut pavers should be placed in thelaying pattern to provide a full and complete paverplacement prior to initial compaction. Coursing can bemodified along the edges to accommodate cut pavers.Joint lines are straightened and brought into confor-mance with this specification as laying proceeds andprior to initial compaction.

Remove debris from surface prior to initial com-paction and then compact the pavers using a vibratingplate compactor with a plate area not less than 2 sf (0.2

m2) that transmits a force of not less than 15 psi (0.1MPa) at 75 to 100 Hz (see Figure 9). After initial com-paction, remove cracked or broken pavers, and replacewith whole units. Figure 10 shows removal of a paverwith an extraction tool. Initial compaction shouldoccur within 6 ft. (2 m) of all unrestrained edges at theend of each day.

After initial compaction of the pavers, sweep andvibrate dry joint sand into the joints until all are com-pletely filled with consolidated joint sand (see Figures11 and 12). The number of passes and effort requiredto produce completely filled joints will vary based onmany factors. Some of these include moisture, sandgradation, sand angularity, weather, plus the size, con-dition, and adjustment of the vibrating plate, the thick-ness of the pavers, the configuration of the pavers, andthe skill of the vibrating plate operator.

Joint sand should be spread on the surface of thepavers in a dry state. If is damp, it can be allowed todry before sweeping and vibration so it can enter the

Figure 11. Sweeping jointing sand across thepavers is done after the initial compaction of theconcrete pavers.

Figure 12. Final compaction should consolidate thesand in the joints of the concrete pavers.

Figure 9. Initial compaction sets the concrete pavers into the bedding sand. Figure 10. During initial compaction, crackedpavers are removed and immediately replaced withwhole units.


joints readily. Vibration and filling joints with sand incompleted to within 6 ft. (2 m) of any unconfined edgeat the end of each day.

The various activities of the crews should be sched-uled so that the paver surface is completed each day.This is the best practice. The surface should be placedto specified tolerances, all cut pavers in place beforeinitial compaction, and the joints completely filledafter the final compaction. This provides the maximumprotection from weather and vehicles. Moreover, oncean area is completed, inspected and accepted, it can beput to immediate use by the owner.

Coordination and Inspection—Large areas ofpaving are placed each day and often require inspec-tion by the Engineer or other owner’s representativeprior to initial and final compaction. Inspection shouldkeep up with the paving so as to not delay its progress.There may be the occasional case where there inspec-tion is not administered on a timely basis. In suchunlikely cases, the Engineer should decide the totalallowable uncompacted area. It should be based on thedaily production of the subcontractor, inspectionschedules, and weather. Therefore, the Engineer mayestablish a maximum distance from the laying face foruncompacted pavers that relates to the timing ofinspection. For work in rainy weather, the 6 ft. (2 m)distance should be maintained, regardless of the timingof inspection. Rainfall will saturate the bedding sandunder uncompacted pavers with no sand in the joints.This condition makes the bedding course impossible tocompact.

3.2.1 Joint Sand ConsolidationAfter the final compaction of the joints in the sand,filling and consolidation of the joint sand should bechecked by visually inspecting them. Consolidationis important to achieving interlock among the units.Consolidation also reduces infiltration of water intothe sand and base. This can be done by dividing theproject into areas of about 5,000 sf to 10,000 sf (500to 1,000 m2 ). Visually and physically inspect eacharea by taking at least 30 measurements of joint sanddepth and consolidation. Take measurements byinserting a thin, rigid putty knife into the joint andpressing down. See Figure 13. It should not pene-trate more than 1/4 in. (6 mm) when pressed firmlyinto the joint.

If areas are found deficient in consolidation and/orjoint sand, make additional passes of a plate com-pactor. It should have a minimum compaction of 6000lbf (26 kN). Higher force compactors will be requiredon pavers thicker than 3 1/8 in. (80 mm). Inspect thejoints again after refilling and compaction. Fill andcompact until the joint sand has consolidated so that aputty knife moves less than 1/4 in. (6 mm) into the joint.

3.3 Tolerances on CompletionThe minimum joint width is determined by the sizeof the spacer bar used for the project. This is typi-

cally 1/16 in. (2 mm). The maximum joint widthdepends on the paver shape and thickness.Generally, thicker pavers with more than four sides(dentated) will require slightly larger joints, often asmuch as 1/4 in. (6 mm).

Recommended tolerances are as follows:1. Joint widths: This depends on the paver thick-

ness. For 3 1/8 and 4 in. (80 and 100 mm) thickpavers, 1/16 to 3/16 in. (2 to 5 mm) is acceptable.No more than 10% of the joints should exceed 5mm for the purposes of maintaining straightjoint lines. For 4 3/4 in. (120 mm) thick dentatedpavers, the maximum joint spacing can beincreased to 1/4 in. (6 mm) with no more than10% of the joints exceeding 6 mm for the pur-poses of maintaining straight joint lines.

2. Bond or joint lines: ±1/2 in. (±15 mm) from a 50ft. (15 m) string line.

3. Surface tolerances: ±3/8 in. over a 10 ft. (±10mm over a 3 m) straightedge. This may need tobe smaller if the longitudinal and cross slopes ofthe pavement are 1%. Surface elevations shouldconform to drawings. The top surface of thepavers may be 1/8 to 1/4 in. (3 to 6 mm) above thefinal elevations after the second compaction.This helps compensate for possible minor set-tling normal to pavements. The surface eleva-tion of pavers should be 1/8 to 1/4 in. (3 to 6 mm)above adjacent drainage inlets, concrete collarsor channels. Surface tolerances on flat slopesshould be measured with a rigid straightedge.Tolerances on complex contoured slopes shouldbe measured with a flexible straightedge capa-ble of conforming to the complex curves in thepavement.

3.4 Protection and Clean UpThe GC should insure that no vehicles other thanthose from subcontractor’s work are permitted onany pavers until completion of paving. This requiresclose coordination of vehicular traffic with othercontractors working in the area. After the paverinstallation subcontractormoves to another area of a largesite, or completes the job andleaves, he has no control overprotection of the pavement.Therefore the GC shouldassume responsibility for pro-tecting the completed workfrom damage, fuel or chemicalspills. If there is damage, itshould be repaired to its origi-nal condition, or as directed bythe Engineer. When the job iscompleted, all equipment,debris and other materials areremoved from the pavement.

Figure 13. A simple test with a putty knifechecks consolidation of the joint sand.

Interlocking Concrete Pavement Institute1444 I St. NW, Suite 700Washington, DC 20005-6542 USA(202) 712-9036Fax: (202) 408-0285

Canada:PO Box 2305355 Ontario StreetMilton, ON L9T 2M0E-mail: [email protected] site: www.icpi.org

WARNING: The content of ICPI Tech Spec technicalbulletins is intended for use only as a guideline. It isNOT intended for use or reliance upon as an indus-try standard, certification or as a specification. ICPImakes no promises, representations or warranties ofany kind, express or implied, as to the content of theTech Spec Technical Bulletins and disclaims any lia-bility for damages resulting from the use of TechSpec Technical Bulletins. Professional assistanceshould be sought with respect to the design, specifi-cations and construction of each project.

References:1. MasterFormat, Construction Specifications

Institute, Alexandria, Virginia, 1995. Note:Division 02, Section 02785 is where interlock-ing concrete pavement is often specified. CSIshould be contacted as major changes are under-way for MasterFormat. See <www.csinet.org>.

2. ICPI, Mechanical Installation of InterlockingConcrete Pavement, Tech Spec 11, InterlockingConcrete Pavement Institute, Washington, DC,1998.

3. Probst, Martin, “Mechanical Installation ofConcrete Block Pavers,” in Proceedings of the3rd International Workshop on Concrete BlockPaving, Cartagena, Columbia, May 10-13,1998, pp 39-1 to 39-11, Institute of ColumbianCement Producers, Medellín, Columbia, 1998.

4. ASTM C 936, Standard Specification for SolidConcrete Interlocking Paving Units, AnnualBook of Standards, Vol. 04.05, ASTMInternational, Conshohocken, Pennsylvania,2001.

5. CSA A231.2, Precast Concrete Pavers,Canadian Standards Association, Rexdale,

Ontario, 1995.6. ASTM C 140 Standard Test Methods for

Sampling and Testing Concrete Masonry andRelated Units, Annual Book of Standards, Vol.04.05, ASTM International, Conshohocken,Pennsylvania, 2001.

7. ASTM C 418, Standard Test Method forAbrasion Resistance of Concrete bySandblasting, Annual Book of Standards, Vol.04.02, ASTM International, Conshohocken,Pennsylvania, 1998.

8. BS 6717: Part 1: 1993:, Precast ConcretePaving Blocks. British Standards Insitute,London, England, 1993.

9. Dowson, Allan J., Investigation and Assessmentinto the Performance and Suitability of LayingCourse Material, Ph.D. Dissertation, Universityof Newcastle, England, February, 2000.

10. ASTM C 33, Standard Specification forConcrete Aggregates, Annual Book ofStandards, Vol. 04.02, ASTM International,Conshohocken, Pennsylvania, 2001.

11. CSA A23.1, Concrete Materials and Methods ofConstruction, Canadian Standards Association,Rexdale Ontario, 1995.

12. ASTM C 136, Standard Test Method for SieveAnalysis of Fine and Coarse Aggregates,Annual Book of Standards, Vol. 04.02, ASTMInternational, Conshohocken, Pennsylvania,2001.

13. CSA A23.2A, Canadian Standards Association,Rexdale, Ontario. 2000.

14. ASTM C 144, Standard Specification forAggregate for Masonry Mortar, Annual Book ofStandards, Vol. 04.05, ASTM International,Conshohocken, Pennsylvania, 2002.

15. CSA A179, Mortar and Grout for UnitMasonry, Canadian Standards Association,Rexdale, Ontario, 2000.

Figure 14. The Port ofOakland, California, isthe largest mechanical-ly installed project inthe western hemisphereat 4.7 million sf(470,000 m2).

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