Mike Harper - NextGen Events

safetrack ® 

Micro-Trench Reinstatement Techniques 

Youre not putting that in my 

road 

Micro-trench reinstatement 

Presented By: Mike Harper – Development Director, Stirling Lloyd. 

NextGen 12 - London 

www.stirlinglloyd.com

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Micro-trenching Reinstatement 

• What is the problem? 

• Why Micro-trench? 

• Limitations of traditional 

reinstatement 

• Incorrect approaches 

• Whats required? 

• The Safetrack approach 

• Step by step examples 


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What is the problem? 

• Micro trenching not covered by 

the new yellow book 

• Little existing knowledge on how 

to reinstate micro trenches 

• Councils object on grounds of 

• Youre cutting my road in half 

• No specification 

• Water ingress into the road 

• No HAPAS approval 

• Cant compact asphalt in a slot 


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Why Microtrench? 

1 - Its Much Faster 

! 4 to 5x faster than open trench 

! 600 ln m per day on a trunk 

route (achieved in Shetland) 

! Less disruption to the public 

! Less traffic congestion 

Getting FTTP to 90% of UK addresses 

could mean 247,500 km of fibre 

installation! 


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2 - Lower Environmental Impact 

! Significantly less waste created 

to be disposed of 

! Less new materials imported 

! Fewer truck movements because 

of the above 

! Less traffic congestion because 

of fast turnaround 

! All this means lower CO 2 


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3 - Lower Cost 

! Lower costs because of speed / 

waste & new material 

! Lower long term maintenance 

costs if you get the reinstatement 

right (no secondary compaction / 

sunken trenches) 

! Less damage to the highway 

asset (shallower – less impact on 

sub-base / surface course and 

services) 


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What is the problem? 

• Traditional reinstatement materials 

(macadam & asphalt) were not designed 

for this. 

• Cant place / compact hot asphalt / 

macadam in a 20mm wide slot 

• Pouring neat bitumen is not the solution 

(no strength or skid resistance) 

• Trying to tamp cold lay asphalt? Early 

failure due to lack of compaction 

• Most methods will let water into the 

pavement!! 


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Incorrect approaches and why? 

1. Cement grout to the surface 

Not flexible 

No bond to asphalt 

Cracking / water ingress 

Slow strength gain 

2. Epoxy Mortar 

Not flexible 

Long cure time = greater disruption 

Cracking / water ingress 

2. Cold lay macadam 

Needs adequate compaction to 

achieve cohesion 

Little bond to cut asphalt edges 

Ineffective seal – water ingress 

Lack of cohesion 


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What current advice is there? 

• Most recent advice note from DCMS – 

the Department for Culture, Media & Sport 

- outlines current best practice 

• This can be complied with and is a good 

start 

• Key drawback is reinstatement in the 

asphalt layer only at depths that exceed 

the asphalt depth in evolved roads 


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So what do we need to reinstate a micro-trench effectively? 

• A fluid material that will penetrate - 

needs no compaction 

• High bond strength to the cut asphalt 

• Supports the cut edges of the asphalt 

• Compatible flexibility with asphalt 

• No shrinkage & waterproof seal 

• Skid resistance 

• Dimensional stability under traffic 

• Fast return to service 

• BBA / HAPAS approval 


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The Safetrack approach 

• Materials designed for highway use 

• Safetrack is fluid & self compacting 

• Cold applied – safe to use 

• No site mix – Factory batched (QA) 

• Dimensional stability – cant be trafficked 

out, rut or sink (no secondary compaction) 

• Bond strength > cohesive strength of asphalt 

(bonds the road back together) 

• Waterproof and seals the road 

• Skid resistant 

• No glare 

• BBA / HAPAS approved 


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The Safetrack approach 

Additional benefits 

• No specialist equipment = quality installation 

from every team, all the time. 

• No heating = no risks to public and 

operatives + less CO2. 

• Safetrack MTI indicator layer = reduces risk 

of accidental damage in future by using yellow 

below the surface 

• Doesnt damage the fibre installation 

• Permits removal / reinstatement of duct if 

required. 


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Successful Safetrack Microtrench Installations 

South Wales – Safetrack approved for use by the 

Welsh Assembly for microtrenching on trunk roads 

in 2009 

Shetland – Safetrack products successfully used 

over last 3 years – now on Phase 4. 

Galway – Safetrack products used over last 2 

years – now in Phase 2. 

Bournemouth – multiple products tried without 

success. Safetrack products were the only ones 

regarded successful by Bournemouth CC. 


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Microtrenching 

Step by step through the process 


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Cutting 


• Cutting machine type 

is very important 

• Match the duct to the 

cut size 

• Avoid oversize cutting 

• 20mm cut / 16mm 

duct is ideal where 

possible 


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Cutting 


• Dry cutting is a clean 

process - no slurry 

waste from wet cutting 

• Vacuum extraction 

hoovers dust from 

the slot 

• Cutting depth is 

constant (150mm here) 

• Overbreak along the 

cut is minimal 


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Cutting 


• Vacuum extraction 

avoids dust 


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Cutting 


• Resultant cut is even 

width 

• Minimal damage to 

surrounding asphalt 

• Minimal work area 

• Fast, clean and 

accurate 


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Drying 


• Safetrack drying lance 

removes any residual 

dust 

• Dries the cut asphalt 

faces using air and / or 

heat if required 

• A clean dry asphalt 

face = high bond 

strength and a good 

seal 


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Installation 


• Protective foam strip into the 

bottom of the micro-trench 

• Microduct – with or without fibres 

– is installed 

• A protective foam strip is applied 

over the duct 

• The micro-trench is now ready to 

be permanently reinstated 


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Reinstatement 


• Installing Safetrack 

Crack Infill into the 

micro-trench 

• Cold process – simple 

and accurate placement 

• Can use yellow 

indicator below the 

surface to avoid future 

damage 

• BBA / HAPAS 

approved product 


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Reinstatement 


• Yellow first pass up to 

10mm from the surface 

• Black capping layer 

with embedded 

aggregate for skid 

resistance 


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Reinstatement 


• Safetrack 

Overbanding black 

surface layer 

• Aggregate overscatter 


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Reinstatement 


• Process train 

approach moves 

continuously along the 

road 

• All the processes are 

in this image 

• Rapid cure of the 

reinstatement means 

minimal traffic 

management behind 

the works 

• 600 ln m per day 

complete installation 


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Reinstatement 


• Completed micro-trench 

• Fibre duct installed at 150mm deep 

• Safetrack Overbanding permanent 

reinstatement 

• Up to 600 ln m per day completed and 

returned to service same day (Shetland 

rural roads) 


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But weve always done it this way …… 

• Traditional trench dig would be 5x slower 

• Would create much more disruption for 

residents and road users 

• Uses far more material and creates much 

more waste 

• Far higher carbon footprint 

• Much greater damage to the road or 

pavement asset and likely requirements for 

more long term maintenance (secondary 

compaction etc) 

• We need micro-trenching but we need to 

do it right. 


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Questions? 


For more information contact us: 

t: 01565 633111 

m: 07976 517200 

e: mike.harper@stirlinglloyd.com 

w: www.highwaymaintenanceproducts.co.uk

Mike Harper - NextGen Events

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