Excavations for a major pipeline bisecting a section of Northbury Road in Phoenix, Durban, caused severe damage to the existing surface. After an on-site inspection, Naidu Consulting determined Kaytech’s SealGrid 50to be theideal geosynthetic interlay forthe rehabilitation project.

Once Durban’s existing Northern Aqueduct system had reached maximum flow capacity, construction of the Northern Aqueduct Augmentation system commenced in 2014. This massive project, undertaken in phases by eThekwini Municipality, has increased bulk water infrastructure for the city’s rapidly developing northern areas. The pipeline crossing Northbury Road formed part of Phase Five of the project in progress during 2019.

Once excavation for the pipeline was completed, contractor Masakhane Project Managers cleaned the surface area of all dirt, dust and vegetation. Thereafter, all large cracks were filled and covered with a levelling course of asphalt. A cold pave tack coat was then applied by hand to the asphalt at a rate of one litre per square metre.

After waiting for the tack coat to break, 300 m² of SealGrid 50 (50 x 50 kN/m) was laid out on to the tacked surface, in the process ensuring that it was free of wrinkles and folds. It was then rolled with a pneumatic tyre roller to prevent pick-up. To complete the four-week project, SealGrid 50 was overlaid with a 30 mm layer of asphalt. By bonding the existing surface to the new one, SealGrid will ensure a strong interlock between the two.

Reinforced composite

SealGrid is a reinforced composite paving fabric manufactured from high-strength glass-fibre roving, knitted in a grid pattern on to a paving fabric. The reinforcing effect of the low-strain glass filaments – in combination with the waterproofing, stress-relieving and bonding properties of the paving fabric – leads to a dramatic reduction in reflective cracking under asphalt overlays. SealGrid is unaffected by high temperatures and most chemicals.

A highly versatile product, SealGrid can be installed under or between asphalt layers in many situations, such as where high stresses may occur, on road-widening schemes with differential settlement or where stress cracking is possible over expansive clay subgrades. Importantly, by reducing traffic-induced crack propagation by a factor greater than seven, SealGrid provides a significantly increased life cycle, which in turn equates to great economic benefits. The end results have been put to the test on Northbury Road.