Transportation Professional June 2018

Road reinforcement solution proven in south Wales

Rate of cracking in micro asphalt has been reduced on a street in Cardiff with the introduction of geotextile reinforcement.

Use of a geotextile reinforcement system to extend pavement life is proving successful on a residential road in Cardiff following an installation by specialist contractor Asphalt Reinforcement Services.

The firm’s GlasPave 50 solution was deployed on Mercia Road – an estate road composed of seated concrete overlaid with a 30mm dense bituminous macadam (DBM) – last summer. The road surface was displaying cracking failure and options to deal with this were limited. Introducing the geogrid system under a micro asphalt layer was seen as a cost effective solution to help stop further deterioration.

GlasPave 50 mats are constructed of high strength continuous fibreglass fibers, coated in an elastomeric polymer and embedded between two spun bond polyester textiles. The contractor installed this reinforcement system with 50kn/50kn tensile strength directly to the existing asphalt surface.

In total 1200m² of reinforcement was rolled out. The solution was used in conjunction with a 160/220 pen bond coat before being overlaid with a micro asphalt system in two layers to a nominal thickness of 15mm.

The installation was undertaken successfully and, although only a year on, the early signs are positive with no cracking evident in the carriageway. Asphalt Reinforcement Services managing director Howard Cooke comments that geotextile reinforcement extends the life of pavements, and can significantly delay cracking in asphalt, which is recognised as one of the biggest problems faced by highways engineers.

Cardiff City Council highways engineer Gareth Jones adds that Glaspave 50 used in the right circumstances is a valuable tool for highway engineers in managing the highway asset effectively. Installation of the solution on Mercia Road came following an earlier controlled trial in 2012 at Penarth Road, a route serving industrial and retail units in Cardiff that features a jointed concrete carriageway with sections 7m long.

Cardiff City Council undertook a trial to investigate whether a geotextile used
in conjunction with a premium micro asphalt system would extend the life of the pavement against cracking failure. Control sections were laid featuring no geotextile.

Within four months the control sections had started to crack over the construction joints within the concrete. But the reinforced sections were found to extend the pavement life and only after four years started to show signs of cracking over the joints. Gareth Jones says that the geotextile had significantly extended the life of the micro asphalt and that the cracking now present over the joints in the reinforced section were significantly less pronounced than those in the control sections without the geotextile.