Umbumbulu Road project in a ‘Glas’ of its own

13 March 2019 | Web Article Number: ME201913893

Construction, Civil & Structural Engineering
Consulting Engineers & Project Management
Engineering Supplies

WHEN delays during a routine maintenance project on the R603 in KwaZulu-Natal caused severe problems, Kaytech was contacted to supply GlasGrid, an asphalt pavement reinforcement system that the company says dramatically extends the lifespan of roads, runways and parking lots.

Popularly known as the Umbumbulu Road, the 81km R603 is an important regional route intersecting with the N3 near Camperdown and ending near the N2 at Winkelspruit on the South Coast.

Bypassing the congestion of the N3/N2 EB Cloete ‘spaghetti junction’ in Durban as well as reducing the distance between the two towns by 10km, the Umbumbulu Road is a convenient alternative for both travellers and freight traffic alike.

Umbumbulu Road project in a ‘Glas’ of its own
Road maintenance on the Umbumbulu Road

With numerous sections of the road requiring resurfacing, the KZN Department of Transport appointed VNA Consulting to design and supervise a roadworks project that included milling off the existing asphalt and replacing it with a new 40mm asphalt surface.

Due to unforeseen circumstances, however, after milling was completed, the base course was left exposed for a period of time during which heavy rains caused softening of the base leading to both vertical and horizontal cracking.

To prevent these cracks from reflecting through the proposed new asphalt layer, GlasGrid 8550 (50kN x 50kN tensile strength) was specified where a layer of existing asphalt would be milled off and the GlasGrid 8550 affixed to the milled surface.The 8550-grade open aperture size of 25 x 25mm conforms to the milled surface texture quite well.

Pinetown-based contractor, Crossmoor Transport commenced the project in January 2019. At the time of writing, the project was still ongoing with 3 000sqm of GlasGrid 8550 having been installed.

Designed for asphalt reinforcement, GlasGrid is a polymer-coated, woven fibreglass grid structure with a pressure-sensitive adhesive to enable ease of placement. By ‘sandwiching’ the geogrid between the prepared milled surface and new asphalt course or within two layers of new asphalt, cracks are redirected horizontally thus dissipating traffic induced stresses. The open aperture design of GlasGrid promotes aggregate interlock between layer works thereby greatly decreasing shear potential so common in paving fabrics.

Besides water-induced cracking as in this case, further causes of pavement cracking are loading, age-hardening and temperature cycling. By providing strength and strain resistance for long-lasting performance, GlasGrid helps arrest these cycles of deterioration by retarding cracks from reflecting through asphalt overlays.

“GlasGrid is the hidden strength in a road and reduces reflective cracking for years to come. The combination of high tensile strength and high modulus of elasticity at low strain makes GlasGrid stronger than steel by mass in all asphalt reinforcement applications,” Kaytech representative Sham Luchai said.

He added that the inclusion of GlasGrid in the Umbumbulu Road project would mean far lower maintenance costs in the future as well as a postponement of the complete reconstruction of the road.

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