sprayed concrete getting the best from...efnarc-certified nozzlemen in their tender documents....

IT TAKES A CERTAIN sort of person to be agood nozzleman. “They have to really careabout the job,” says spray master AdamBarker, a nozzleman with an impressive 18years experience. “People who have beendoing it for a long time, it gets into theirblood. They love it.”

For proof of the difference a nozzleman canmake, take a look at two samples (photo tothe right), taken from the same tunnel and thesame concrete batch, but applied by twodifferent nozzlemen. As sprayed concretelinings move from the realm of temporaryworks into permanent works, designers needassurances that their wall will look like thesample on the right, not the one on the left.

Yet until recently, there was no way ofknowing how good your nozzlemen were.

Enter EFNARC, once a group of nationalassociations set up to reach technicalagreement on the new Euro Norms, now agroup of manufacturers and other expertssetting guidelines on how to best usedeveloping concrete technologies. EFNARC’sguidelines are recognised around the industry,more often than not forming the basis for thenext generation of standards.

In October 2009, EFNARC, (which nowdefines itself as an international association ofExperts for Specialised Construction andConcrete Systems), launched its nozzlemancertification scheme (see Box p41). Althoughstill in its infancy, the scheme is already gainingrecognition, with some clients asking forEFNARC-certified nozzlemen in their tenderdocuments. EFNARC has also been talking toCrossrail about how the scheme can be

applied at their Tunnelling and UndergroundConstruction Academy (TUCA).

Recognising how crucial the role ofnozzleman is becoming, EFNARC membersNormet, who Barker joined in 2009, Mapei,Putzmeister, Sika, Stratacrete and TAM, havebeen among the first to send employees onthe examiners courses. Normet, for example,wants to have 12 spray masters, like Barker, onits books in five years’ time: practical andtechnical experts who can provide trouble-shooting, training and certification services toits customers.

Supporting innovationLike the new residual flexural strength test forsprayed concrete which one of its technicalcommittees has just published (see Box p44),the nozzleman scheme demonstrates whatEFNARC is all about: bringing the latestpractical experience, technical knowledge andresearch together to ensure that contractorsand designers get the best out of the materialsthey are using.

“The companies in EFNARC understand thatthey can’t introduce new technologies andinnovations, without some sort of history orperformance or backing,” says EFNARC

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40 TUNNELLING JOURNAL

Getting the best from

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As the use of sprayed concrete advances, so mustthe skill of those applying it and the testing

regimes used to check it. That’s where EFNARCcomes in, reports Kristina Smith

TJ_0911_ERNARC_Reprint.qxd:Feature 5/9/11 22:14 Page 3

secretary Roland Harbron.“By producing guidelinesand standards, they aregiving assurances to theindustry and protecting theirinterest by making sure theirproducts are being usedcorrectly.”

Because all the members ofEFNARC’s technicalcommittees are involveddirectly in the industries theyserve, they can work out wherethe next gaps in knowledge andinformation are likely to be andact accordingly. Once thenozzleman scheme is fullyestablished, EFNARC has plans tolook at a similar style certificationscheme related to the design ofpermanent sprayed concretelinings in tunnels.

The nozzleman scheme takesexpert practitioners from aroundthe world and trains them to beexaminers who can then certifyalready-experienced nozzlemen.These examiners test nozzlemen on

1Experienced nozzlemen, oftenalready trainers, attend an

assessment course at the HagerbachTest Gallery in Switzerland. During the2.5 day course, they receive a technicalrefresher course and learn how to testnozzlemen on their spraying skills andtechnical knowledge.

2Armed with the nozzleman coursenotes and slides, theory exam

questions and practical assessmentforms and checklists, the examiners cannow begin assessing nozzlemen in theirworkplaces.

3Over two days, an examiner willtake the

nozzlemen through the course notesand spend time with them at theworkface before the practical andtechnical assessments.

4The practical assessment covers pre-application tasks, start-up

procedures, spraying applicationprocedures, shut down procedure,troubleshooting and problem solvingand HSE issues. The practicalassessment has a higher overallweighting than the theoretical one.

5The theory assessment takes theform of a multiple choice, given

aurally or in a writtentest. The course notescontain all theinformation neededto answer thequestions correctly.

Here are threeexamples of thetheory questionswhich thenozzleman might beasked to answer.We have notincluded theanswers as wedon’t want to giveanyone an unfairadvantage!

Five steps to a certified nozzleman

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1. Tick 3 actions to ensure good bond strength between

successive layers of sprayed concrete.

� sand blasting

� use internal curing agents

� apply a bonding agent

� hydro-jetting

� detergent application

� high volume water jet

� dampen surface

2. Order the following actions (1 to 7) to be taken

immediately a blockage occurs.

� point nozzle down

� stop accelerator

� stop air

� reverse concrete pump

� stop concrete pump

� locate blockage if in line

� release line clamps/couplings

3. Tick 3 ways that excess water will

most affect the properties of sprayed

concrete.

� reduce the in-place cost

� lower the durability

� improve long term strength

� increase the setting time

� reduce strength

More information from www.efnarc.org and [email protected]

TUNNELLING JOURNAL 41


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their practical skills and top up their technicalknowledge. The result is certified nozzlemenwho are not only competent applicators butwho also have the confidence to challengewhen problems occur.

“One of the most important things with wetspray is the material. They need to know if it isright, and if it isn’t right, they need to knowthe reason why,” says Paul Brown, seniorcontracts engineer with BAM Ritchies. Brown,who has 38 years of spraying concrete underhis belt, is not an EFNARC member but he isone of the 23 new examiners, havingattended one of the first courses. “Armingthem with technical knowledge is a greatthing. It is something I have had to gleanalong the way.”

As is the norm in construction, nozzlementend to fall into the job by a combination ofchance and family connections. Barker, anEnglishman who moved to Australia when hewas eight, got his first spraying job through agirlfriend’s father. For Brown, it was his unclewho introduced him to the industry.

In times of boom, almost anyone will begiven the nozzle. “Take Australia before wehad the economic crash: if anyone looked likehe could do it, they would get him in thereand start him doing it,” says Barker who wasworking in Australian mines before Normet

recruited him. “When a lot of people got laidoff, those that hadn’t been doing it for longfell by the wayside.”

Both Barker and Brown are agreed that theideal nozzleman needs a combination ofdedication and endurance. “We tend to bringpeople into the industry as machine operativesand graduate them onto the nozzle if they aresuitable,” says Brown. “Part of that suitabilityis conscientiousness. They are a pretty uniquebreed.”

“To be a nozzleman, you can’t be afraid ofhard work,” adds Barker. When blockagesoccur, a nozzleman must wrench apart thepipes by hand to unblock them. And he mustbe prepared to stay at his post until the job isdone, however many hours it takes.

Although years of experience are often agood indicator of a competent nozzleman,Barker says that he has come across men witha decade on the tools but the wrong attitude –which can be just as disastrous as aninexperienced sprayer.

The fact that sprayed concrete is applied byrobotic arm these days does not negate thepossibility of problems and errors. There are

still plenty of things that can go wrong, fromthe blockages already mentioned, to incorrectmixes, to the actual application.

Barker spent time hand spraying before hestarted working with robots, experience whichstood him in good stead. “You have a muchfiner technique when you have done handspraying,” he says. “Spraying concrete is allabout the angles. You have to spray at 90degrees to the surface you are spraying on.”

In a tunnel with its uniform cross-section,angles are less of a problem. But in mines,where blasting has made the way, there areangles everywhere. If a nozzleman tries tospray everything from one position, there willbe voids which are weak points.

Soaking up the knowledgeTo date 26 nozzlemen have been certified.And while you can find the names of all theEFNARC examiners on its website, you won’tfind the names of the nozzlemen. Althoughthey originally intended to list them, EFNARCsoon realised that this would form a shoppinglist for contractors.

Barker has certified seven men, in Anglo

A montage of pictures showing nozzlemen in action, both at work and in the Hagerbach TestGalleries in Switzerland. Comparing the right photos to the one on the left gives a goodindication of the different quality surfaces a sprayer will have to contend with

“One of themost importantthings withwet spray isthe material.They need toknow if it isright, and if itisn’t right,they need toknow thereason why”


American’s Lisheen Mine and Boliden’s TaraMine, both in Ireland. His experience hasshown how eager the nozzlemen are to gaintechnical knowledge – even though there areover 100 EFNARC training slides to workthrough, taking the nozzlemen from thebatching plant all the way through the processto application and testing.

“They really absorb all the technical stuffthey are not exposed to in their every dayworking lives,” says Barker. “They are likesponges.”

And that knowledge will have a big impact,says Barker, citing water/cement ratio as anexample. “If the concrete turns up and it’s a bitdry, a nozzleman would usually add a bit ofwater,” he says. “Now they realise how badthat is: what they do to that mix could be

detrimental to its strength. That’s somethingconcrete sprayers really need to be aware of.”

The thirst for technical knowledge alsoapplies to the examiners. Originally a two-daycourse at the Hagerbach Test Gallery inSwitzerland, the session was extended to two-and-a-half days so that they could learn moreabout concrete technology with theresearchers.

The existing test for checking theresidual flexural strength of sprayedconcrete linings needs updating: it’scomplicated to do, doesn’t match theupdated international standard andmay not give accurate results. That’swhy EFNARC’s Fibres TechnicalCommittee has spent over four yearsdeveloping a new test method, nowpublished, which has addressed allthose issues.

“Testing is very important. And nowthat some contractors, especially in theUK, are promoting the use of SCL as afinal lining it becomes even moreimportant,” says Benoit de Rivaz, chairof the committee and global tunnellingmanager for Bekaert. “Residual strengthis a key material property. That’s whywe need such an accurate residualstrength value.”

There are two main tests used forsprayed concrete. Energy absorption ismeasured by testing a small panelwhich can be sprayed at the job site.But energy absorption, although usefulfor comparing different products withthe same mode of failure, is not used asa design value.

The test for residual flexural strength,EN 14488-3, requires a much largerpanel to be sprayed, from which beamsmust then be cut. In practice, says deRivaz, this test is often not very oftenused because it is not really practical.

EFNARC’s new test employs exactlythe same size of panel as the energyabsorption test. These can be sprayedon site alongside the energy absorptionones and then go straight to thelaboratory to be tested on standardequipment. The panel size ensures that

the distribution of fibres in the matrix isas close as possible to that in the realstructure, in contrast with the sawnbeams, which cuts through fibres,creating a false situation.

The new test method also definesresidual flexural strength in the sameway as the updated international code,fib Model Code 2010. And the scatter ofresults this test produces is lower thanthat produced by the existing one –which means it is more accurate.

EFNARC hopes that its test methodwill go on to become an official ENStandard, as is the case with many of

the guideline it produces. This will takeat least a year, says de Rivaz, as moreresults from the field must now begathered. But the method has alreadybeen presented to the ITA’s WorkingGroup 12 on Sprayed Concrete Usewhich should smooth its passage tobecoming an EN and/or ASTM.

The next task for the Fibres TechnicalCommittee, whose members come fromBekaert, Adfil, CUC, Grace andMaccaferri, is to assess all the availabletest methods for fibre reinforcedsprayed concrete to check theirrelevance and accuracy.

Why accurate tests are vital

Instructors and attendees work together at the EFNARC Nozzleman

training course in Switzerland’sHagerbach Test Galleries, not only to

improve actual spraying practices,but to further their theoretical

understanding of concrete

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“On the examiner’s course, you get told alot of things you probably already know, butit’s beneficial to have it all in front of you,” saysBarker. “It confirms what you have learnt fromyears of experience and takes you up to thenext level. You are gaining experience frompeople who have studied it.”

The fourth examiner’s course – whichexperience has shown runs best with eightpeople or less, says Harbron – will take place inOctober this year. The notes for the course,which are given to the examiners and thenozzlemen, will also be updated, as EFNARC’s

goal is to keep pace as technology andpractice moves on.

Examiners outside Europe have alreadybeen trained from Australia, Asia, North andSouth America. The next steps will see thenotes translated into other languages,starting with Spanish, German and Italian.

Although all examiners and nozzlemenmust be re-assessed every three years,Harbron will be setting up an auditing systemto provide an extra level of assurance that thesame standard of certification applieswherever the examiners are working. And he

is talking to ITA about gaining theassociation’s approval for the certificationprocess.

Looking further to the future, Barkerbelieves that clients will require that allnozzlemen be EFNARC-certified. Crossrail’sstated ambitions to up the competency ofthe industry through TUCA can only helpspeed that process. But in the mean time,those contractors who can offer EFNARC-certified nozzlemen will definitely be flaggingit up at tender time as an additionalguarantee of quality.


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