TAIT Guidance 28 Mar11

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TAIT Guidance 28 Mar 2011

Guidance on TAIT Process

for TS2010


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TAIT Guidance i 28 Mar 2011

Contents

1 Introduction 11.1 General 11.2 TAIT 1

1.2.1 The TAIT process 11.2.2 Stage approval 11.2.3 TAIT contact 11.2.4 TAIT progress reports 1

2 Stage 1: Laboratory testing and design 22.1 Mix design 22.2 Testing 22.3 Stage 1 Process 4

2.3.1 Responsibilities 42.3.2 Reporting 42.3.3 Approval 5

3 Stage 2: Product mix trial 63.1 Purpose 63.2 Procedure 6

3.2.1 Notification of trial date 63.2.2 Trial mixture 63.2.3

Testing 6

3.3 Material consistency 83.4 Plant 83.5 Training 8

3.5.1 Records of training 94 Stage 3 Trunk Road Network Trial 10

4.1 Paving and Compacting 104.1.1 Transport and delivery 104.1.2 Site preparation and bond coat 104.1.3 Paver and laying 104.1.4 Compaction and gritting 114.1.5 Aftercare 11

4.2 Testing 114.3 Interim Approval 12

5 Stage 4 Final Approval 135.1 TAIT completion 13


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TAIT Guidance 1 28 Mar 2011

1 Introduction1.1 GeneralTransport Scotland Interim Amendment (TSIA) No 35 was issued on 10th December 2010

to introduce a new surface course specification (TS 2010) and notes for guidance. Aspart of controlling the introduction of this new specification, a Type Approval InstallationTrial (TAIT) process has been established.

This guide aims to assist those directly involved in the introduction of the TS2010specification so that the material is consistently designed and configured, produced andlaid correctly.

1.2 TAIT1.2.1 The TAIT processThe TAIT comprises a four-stage process: Laboratory testing and design, Product mixtrial, Trunk Road Network Trial (Interim Approval), and Final Approval. This documentprovides guidance on what information is required to demonstrate compliance with eachstage of the TAIT. The report contains quick reference tables on tests required as part ofeach stage and supplements the TS2010 specification by providing practical advice forClients, Suppliers and Contractors. In particular, the guide is intended to address andhighlight the importance of the following subjects:

mixture composition importance of design and evaluation testing

mixture production product consistency and temperature control

transport and laying operations compaction, joints and gritting

training and supervision demonstrating competence and understanding of thenew specification.

1.2.2 Stage approvalFor the purposes of this guidance, a Hold Point is referred to within the text. This is apoint at which Client approval is required to proceed to the next stage of the TAITprocess.

1.2.3 TAIT contactThe Supplier shall provide Transport Scotland with a named individual who will haveresponsibility for collating all the documentation associated with the TAIT process. TheTAIT contact shall possess appropriate qualifications and experience to manage the fullTAIT process as outlined in the proceeding chapters to this document.

1.2.4 TAIT progress reportsTransport Scotland will document the progress of each Suppliers TAIT application byissuing an interim TAIT status report. This will typically be issued at Stage 3. However,interim reports may be issued earlier, e.g. following Stage 2, to document any

observations or issues that need to be addressed before the Supplier can progress to the

next stage of the TAIT process.


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2 Stage 1: Laboratory testing and design2.1 Mix designStage 1 relates to designing a mixture in the laboratory that meets the TS2010

specification. It includes establishing important aggregate and binder properties andensuring the composition of the mixture adheres to strict grading requirements to ensurethe correct extent of gap-grading. Maximum and minimum air voids content need to bedemonstrated, and performance tests are required to demonstrate that high binder

contents can be achieved in the mixture without drain-off and that adequate deformationresistance is achieved. It is important when using a performance test that particularattention is given to the production method used for the specimen as this can affect theevaluation of the results.

2.2 TestingTable 2.1 provides information on some of the important tests that need to be carriedout as part of Stage 1. The table includes references to the TS2010 specification and

notes for guidance.

Table 2.1: Set of tests for TAIT: Stage 1

Property Test method/procedure Limits Spec & NG Ref.

Coarse aggregateparticle density

BS EN 1097-6:2000 Resultsdeclared

2.2.2.1.1NG 2.3

Notes:

If aggregate density is high (approaching 3.0) then the TS2010 specification minimum

binder content (Table 2.1A & 2.1B) may not be achievable.It is possible that some mixes with high density aggregates will produce very low airvoids content (


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Table 2.1: Set of tests for TAIT: Stage 1 (cont.)


Coarse aggregateresistance tofragmentation

BS EN 1097-2:2010 LA302.2.2.1.5

Notes:

Los Angeles (LA) value should be less than 30: the smaller the number the lessvulnerable it is to fragmentation.

The test is a measure of abrasion/toughness. The aggregate sample is placed in arotating drum with steel spheres and rotated. The number is a percentage of theoriginal weight and is called the "percent loss".

Coarse aggregate

resistance to wear

BS EN 1097-1:1996

micro-Deval method

MDE declared 2.2.2.1.7

Notes:The micro-Deval coefficient is determined using a test that is similar to the LA testabove.

Smaller spheres are however used and the addition of water is made to the sample.

As opposed to the LA test, which tends to break aggregate particles, the MDE wears theaggregates producing rounded particles.

The test is used in parallel with the LA test in France to determine the mechanicalproperties of aggregates. It is included to provide a more comprehensive predictor ofdurability. As a rough guide aggregates can be considered to be durable if % loss 18%.

Air voids content BS EN 13108-20:2006 2.4.12.4.2NG 2.1NG 2.4.1, NG 2.4.2

SMA 6, SMA 8(surf) Vmin3,5 ; Vmax4

SMA 10, SMA 14(surf) Vmin3 ; Vmax3,5

Notes:

The air voids content range is deliberately tight and may be difficult for the Supplier toachieve at Stage 1 (in the laboratory).

At Stage 1, small variations may be permitted (0.2%)where documented evidence ofattempting to achieve the required gradings is provided.

It should be made clear to the Supplier that no relaxation in specification tolerances willbe accepted at Stage 2 (trial strip).

The aggregate shape is a very important factor in achieving air voids content in SMA.Poor aggregate shape can have an adverse affect.

Binder content BS EN 12697-1:2005 Relevantcolumn ofTable 2.1A or2.1B

2.3.1Table 2.1A & 2.1BNG 2.3NG 2.3.1

Notes:

Binder content shall comply with relevant Table 2.1A & 2.1B minimums.

Binder penetration BS EN 1426:2007 75 - 130 NG 2.2.1Table NG 2.1

Notes:


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Binder softening point BS EN 1427:2007 75 NG 2.2.1

Table NG 2.1Notes:

Softening point should be greater than 75 but should not exceed 100oC.

Grading BS EN 12697-2:2002 Relevantcolumn ofTable 2.1

2.3.1Table 2.1A & 2.1B2.12.2

Notes:

Currently the SMA 8 is not used in the UK because it uses a different series of sievesizes. If SMA 8 is being proposed the sieve sizes listed in Table 2.1B apply.

It is important that the supplier targets the mid-point of the grading envelope so

production fluctuations do not exceed the limits of the respective grading curves.

Binder drainage BS EN 12697-18:2004,

Schellenberg method

D0,32.5NG 2.2.5, NG 2.5Table NG 2.2

Notes:

The average binder drainage (D) should be less than 0.3%. The lower the percentage thebetter the result.

The test measures the mass of bitumen lost by drainage, after 1 hour at a temperature

representative of the maximum mixing temperature expected at the mixing plant. Thebinder drainage is determined by the residue left after turning over a beaker containingthe specific mixture.

Resistance topermanentdeformation

BS EN 12697-22:2003 Rut rate andrut depth shallbe reported

2.7NG 2.7Table NG 2.3

Notes:

Limits are not specified as there is little experience of using this test procedure inScotland. However, the rut rate should be less than 1mm/103 cycles and the reduction in

depth no more than 35% of the original thickness of the specimen (see Table NG 2.3).

2.3 Stage 1 Process2.3.1 ResponsibilitiesThe TAIT contact shall identify and nominate a person with responsibility as designer forStage 1 of the TAIT. The individual shall possess appropriate knowledge and experience

of designing asphalt mixtures and supervising staff that will assist in the laboratorytesting and design.

2.3.2 ReportingThe design will be presented in the form of a Stage 1 report and shall be submitted for

approval to Transport Scotland (TS) prior to progressing to Stage 2 of the TAIT process.The report will summarise the results of the laboratory work carried out for the design

and assessment of the proposed TS2010 SMA mixture. Any departure or failure to


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comply with the TS2010 requirements shall be highlighted. The submission of asatisfactory report is a Hold Point within the TAIT process.

2.3.3 ApprovalThe Supplier/TAIT contact will receive Stage 1 approval after the submission of asatisfactory design report. If the design for any reason is not accepted, reasons forrefusal to proceed to Stage 2 will be stated.


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3 Stage 2: Product mix trial3.1 PurposeThe product mix trial forms Stage 2 of the TAIT. It provides an opportunity for those

involved with the process to see the designed mixture being produced, laid and to assessits behaviour under laying and compaction. The mix trial will enable the collection ofimportant information of the laid and compacted material, such as air voids content andthe correlation of certain destructive and non-destructive testing.

The product mix trial is intended to allow the Supplier to become familiar with thematerial and the process of paving, compacting and treating the surface with grit.

The product mix trial also allows the Client to assess the competency of the Supplier smanagement and laying team in fulfilling their requirements to comply with the TS2010

specification.

3.2 Procedure3.2.1 Notification of trial dateFollowing the successful completion of Stage 1, Transport Scotland will agree anarrangement with the supplier for the Product Mix Trial (Stage 2)

3.2.2 Trial mixtureAt least one 20-tonne batch of the design mixture submitted as part of Stage 1 shall be

laid in the presence of Transport Scotland. The trial is not permitted to form part of

permanent Trunk Road works. The compacted material shall be gritted in accordancewith the TAIT Stage 2 requirements in the TS2010 specification.

3.2.3 TestingTable 3.1 provides information in the notes on tests that need to be carried out as partof Stage 2. The table includes references to the TS2010 specification and notes forguidance.


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Air voids in mat BS 594987:2007, Annex G 2.4.2NG 2.1

NG 2.4.2SMA 6, SMA 8(surf) Vmin2 ; Vmax6SMA 10, SMA 14(surf) Vmin2 ; Vmax5

Notes:

The following are important requirements to ensure that the air voids content in the laid materialis met:

The test method is written for binder course, but is to be adopted for the surface course.

The layer thickness shall be 40mm thick.

A pair of 150 mm diameter cores shall be taken at each of three locations: one on thecentre line of the mat, and one centred 0.4 to 0.6 m from the edges of the mat. The corepairs should be spaced equally along the full length of the trial strip.

All cores taken shall be tested and reported.

For calibration purposes, indirect density gauge measurements shall be taken at oradjacent to the location of the six cores.

The Supplier shall provide a method statement for complying with the air voids contentrequirements.

Binder content BS EN 12697-1:2005 Relevant

column ofTable 2.1A or2.1B, toClause 2.3.1tolerance

2.3.1Table 2.1 A&BNG 2.3NG 2.3.1

Notes:

A method statement for collection and sampling shall be submitted to the Client forapproval.

Problems with higher bitumen contents have been reported when the material iscollected in paper bags as a significant quantity of the bitumen is retained in the samplebag.

Grading BS EN 12697-2:2002 Relevantcolumn ofTable 2.1A or2.1 B

2.3.1Table 2.1 A&B

Notes:

If SMA 8 is being proposed the sieve sizes listed in Table 2.1B.


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Texture BS EN 13036-1:2010 To be

recorded

2.11

NG 2.11

Notes:

The initial surface macrotexture shall be measured using the volumetric patch methodusing glass spheres/beads.

Representative areas both with and without grit shall be tested and reported.

For each area at least ten measurements shall be taken diagonally and equally spacedacross the mat (SHW, Clause 921).

Although no specification requirements apply, the texture should not be too low, e.g. anSMA 10 that meets aggregate properties and grading requirements should typically be inthe range 1.1 - 0.8 mm.

The Supplier shall provide a method statement for conducting texture measurements.

3.3 Material consistencyMaterial shall be produced in accordance with the requirements of BS EN 13108-21,Factory Production Control (FPC) and industry Sector Scheme 14, and the Supplier shallprovide evidence of this.

Information such as the Operating Compliance Level (OCL), which is calculated on thelast 32 testing results and the Mean Deviation, should be provided as a method ofassessing product consistency and the proximity of FPC results to the targetcomposition.

Records showing the control of temperatures, grading, and binder content compliance onanalysis are required.

3.4 PlantThe Supplier shall demonstrate through the use of method statements and reference toindustry best practice that the correct and most appropriate plant is used. Examples ofbest practice include:

taking steps to ensure that transportation, laying and compaction temperatures

are achieved

use ofinsulating wings on paver, e.g. clad with 50mm of hardwood

use of shuttle buggies

rollers should operate as close as possible to the paver rollers and be turnedslightly to the side when reversing direction or stopping

calibration of the grit box prior to use.

3.5 TrainingThe use of skilled and properly trained personnel is of paramount importance insuccessfully laying asphalt to the TS2010 specification. Prior to the undertaking of the

Stage 2 product mix trial, Transport Scotland requires documented evidence of


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competency and training appropriate to TS2010 stating the type of guidance given to thepaving team.

The Suppliers attention is drawn to the competency guidelines contained within theNational Highways Sector Schemes (NHSS) quality management system for laying ofasphalt mixtures.

3.5.1 Records of trainingThe content of training should cover the topics and issues covered under the proceedingchapter (Section 4.1) of this document, and evidence of this training shall be submittedto Transport Scotland.


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4 Stage 3 Trunk Road Network Trial4.1 Paving and CompactingTS2010 shall be laid in accordance with BS 594987. The Suppliers team shall be well

trained and familiar with industry best practice.

4.1.1 Transport and deliveryIt is vital that an estimate of the delivery time to site has been made and the correctnumber of wagons has been programmed to allow continuous supply of material to the

paver. In addition, programming shall ensure that paving does not commence until asufficient number of wagons are present on site. This is to guarantee a continuoussupply of material, thereby removing the need for making unplanned transverse joints.

Delivery wagons require to be properly insulated with roller blankets installed. Drivers

shall be instructed not to prepare the wagons for discharge until instructed to do so by

the Suppliers site supervisor. It has been observed on occasion that some drivers havea habit of opening the back door and removing roller blankets prior to reversing to thepaver. Such a practice is particularly detrimental during cold and windy weather as itallows the material to cool prematurely causing a crust to form on the asphalt.

It is important that the asphalt has arrived within the correct delivery temperatureenvelope. In addition, the presence of any contamination, segregation, uncoated and

partially coated material shall be reported to the surfacing supervisor and the load, orthe affected part thereof, rejected. Care shall be taken to remove any material droppedfrom the tailgates of wagons to avoid contaminating the prepared substrate.

A responsible person shall be appointed for site checking and reviewing of all delivery

tickets to ensure that the material is correct and what was ordered. All delivery tickets

shall be given to the Clients representative, who will collate and file them in the projectfile.

4.1.2 Site preparation and bond coatAn inspection of the existing surface that is to be overlaid is required to ensure that it isdry, sound and clean. It needs to be free from loose materials and foreign matter, e.g.mud, slurry, leaves or other deleterious material. The surface shall not be frozen and

shall be free of any standing water.

Joints in the existing pavements shall be formed ensuring that they are clean, verticaland of sufficient depth to suit the asphalt being laid. It is essential that all vertical facesare painted with hot bitumen so that good contact is made between the existingpavement and the new asphalt layer. All iron work shall also be properly prepared, i.e.painted with bitumen.

To ensure that the bond coat is applied uniformly and at the specified rate, the bond

coat sprayer requires to be calibrated and this needs to be undertaken at intervalsspecified in the SHW, Clause 920.

4.1.3 Paver and layingExamples of best practices as per sub-clause 3.5 of this document should be adopted

where possible. Data on the suitability of conditions for the laying of asphalt, e.g.intensity of rainfall, wind speed, air temperature, condition of surface etc., shall be

recorded and assessed prior to making the decision whether paving should commence.


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The paver driver shall be experienced in the correct use of the specific paver to be used.Checks shall be made to ensure that the paver can extend wide enough to remove theneed for hand-spreading of the surface course material. The paver must be fullyoperational, i.e. all 'electronics', such as joint matchers, magic eyes and temperaturedisplay panels are working. If paving is taking place within the winter season the hoppersides shall be adequately insulated and wherever possible the paver hopper shall be kept

full.

The paver shall be capable of laying the asphalt continuously and producing a mat to therequired widths, thicknesses, profiles, cambers and crossfalls without segregation,dragging, overheating, surface defects or irregularities.

At the end of each load, the asphalt around the screws shall be cleared prior to passingfresh material through. The paving team need to be aware that material remaining in thepaver hopper, particularly in the wings, for extended periods may become unsuitable for

use, and they need to have an understanding of what actions should be taken in suchcases. As an example, the speed of the paver may have to be reduced to avoid theaccumulation of cold material.

Hand-laying shall only be undertaken where the site is such that machine laying is

impractical and only where small quantities of asphalt are involved.

4.1.4 Compaction and grittingIt is essential that an adequate number of rollers are present for the tonnage being laid.Rollers shall be filled with water and have fully functioning wetting devices fitted to atleast the width of the rolls. Operators shall have a full understanding of the appropriaterolling method required for the TS2010 material to achieve the correct surface profileand finish and the required degree and uniformity of compaction for the particular layer

thickness and mixture composition.

The discharge and laying of the asphalt shall not commence until the roller drivers have

their rollers in the correct locations ready to commence compaction. Asphalt compactionshall commence as soon as rolling can be undertaken without causing undue

displacement, surface cracking or loss of texture of the asphalt. The operation sequenceshall be such that no discernable roller marks shall be left on the surface.

As required by the TS2010 specification, lightly-coated grit shall be applied from a

hopper attached to the front of rollers. Following an initial two or three passes by theroller over the surface course material, the grit shall be applied at the rate specified.Care shall be taken to avoid over-spreading and overlapping and gritting shall beconfined to the area of the paving works. When the new surfacing has reached ambienttemperature, surplus grit shall be swept from the carriageway prior to the road beingopened to traffic.

4.1.5 AftercareThe new surface course shall remain free from all traffic and plant (including site traffic)until the surface course has reached ambient temperature.

4.2 TestingTable 4.1 provides information on certain tests that need to be carried out as part ofStage 3. The table includes references to the TS2010 specification and notes forguidance.


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Air voids in mat BS 594987:2007, Annex I 2.4.2NG 2.1

NG 2.4.2SMA 6, SMA 8(surf) Vmin2 ; Vmax6SMA 10, SMA 14(surf) Vmin2 ; Vmax5

Notes:

Correlations between non-destructive and destructive testing results shall be monitored,verified and updated as new data becomes available.

Binder content BS EN 12697-1:2005 Relevantcolumn ofTable 2.1A or2.1B, to

Clause 2.3.1tolerance

2.3.1Table 2.1 A&BNG 2.3NG 2.3.1

Notes:

A method statement for sampling shall be submitted to the Client for approval.

Grading BS EN 12697-2:2002 Relevantcolumn ofTable 2.1

2.3.1Table 2.1 A&B

Notes:

If SMA 8 is being proposed the sieve sizes listed in Table 2.1B apply.

Texture BS EN 13036-1:2010 To berecorded

2.11NG 2.11

Notes:

Where site conditions permit, texture measurements shall be taken in the grittedcondition and reported.

For each area at least ten measurements shall be taken diagonally and equally spacedacross the mat in accordance with SHW, Clause 921.

Grip test number after4 weeks and 6months

BS 7941-2:2000 Minimum GripNumber fromrelevantcolumn of

Table 2.3

2.10.1Table 2.4NG 2.10.1NG2.10.2.3

Table NG 2.4

Notes:

4.3 Interim ApprovalFollowing completion of Stage 3 to the satisfaction of Transport Scotland, confirmation of

formal Interim Approval to use the product on the Trunk Road Network will be given.


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5 Stage 4 Final Approval5.1 TAIT completionThe TAIT process is completed when the requirement of Table 5.1 has been satisfied,

and a visual assessment of surface condition has been satisfactorily concluded. Thevisual inspection will be undertaken using the TRL inspection panel methodology, underwhich the material should be assessed asGoodor above. The issue of a Final Approvalwill then be made by Transport Scotland.

Table 5.1: Test for TAIT: Stage 4


CSC# value after aminimum of 2 years*

BS 7941-1:2006 As perrequirementsof HD 28/04(DMRB 7.3.1)

2.10.3

Notes:

The CSC is an estimate of the underlying skid resistance once the effect of seasonalvariation has been taken into account. On receipt of processed survey data, the CSCvalues shall be compared with the predetermined Investigatory Levels [Table 4.1 ofHD28/04 (DMRB 7.3.1)].

* Undertaken by Transport Scotland

# Characteristic SCRIM Coefficient

TAIT Guidance 28 Mar11

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