With torrential rain in February causing existing potholes to widen and new ones to emerge, soil stabilisation products supplier AnyWay Solid Environmental Solutions South Africa believes roads authorities should consider new ways to deal with what is now a persisting scourge.
“The problem with most pothole repairs is that they don’t last and the same pothole has to be repaired constantly because many repairs focus only on the surface and do not fix the underlying problem, says AnyWay Solid Environmental Solutions MD Jean du Plessis.
He explains that potholes occur when the fine particles of a road layer are washed out by a combination of water ingress and pressure caused by vehicles on the layer. The larger particles then become unbound and loose, unable to form a dense mass that can support any pressure. To prevent this situation, one must try to make the particles in a road layer resistant to water ingress.
“This involves strengthening the base-material layers in the pothole, instead of simply covering the pothole with asphalt, which can be done inexpensively, timeously, durably and in an environment-friendly way by reusing the existing base material excavated from the hole and adding some extra soil from the roadside and stabilising it with a soil stabiliser,” he points out.
The company says using a soil stabiliser creates a strong partially impermeable material that has a high interparticle bond strength, therefore preventing the fine particles from being washed out by water and vehicle movement.
“Base material stabilised with AnyWay Natural Soil Stabiliser (ANSS) – a modified cementitious stabiliser that improves the strength and engineering performance of a wide range of soils – is much stronger and more durable than when using only gravel. ANSS-treated material will not break up as easily, allowing for sealing with asphalt within a few days,” Du Plessis continues.
With the current material used to repair potholes, dumpsites are necessary, which is not environmentally friendly, and borrow pits for new material will destroy natural areas somewhere else. The cartage of material by heavy trucks will feed carbon dioxide into the atmosphere and damage roads.
Du Plessis notes that using ANSS eliminates removing and dumping the excavated soil elsewhere as well as transporting new base material to the site, which can be time consuming, costly, inconvenient for road users and harmful to the environment.
Further, should additional material be needed, almost any soil, free of organic material, can be stabilised and used successfully to fill a pothole.
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This method has proven to be successful in repairing potholes on local and international roads, such as the Wellington–Wolseley provincial road, in the Western Cape. Although the road was apparently well drained, it exhibited pothole formations in both lanes virtually after every rainfall before it was stabilised,” he highlights.
AnyWay’s repair action for the road entailed stripping off the asphalt surfacing. This revealed a sandy gravel base layer with rounded river stones underneath, which was removed and stockpiled for stabilisation and reuse, as was the layer of soil beneath it.
“The stockpiled base and subbase materials were then combined and mixed with 4% of ANSS by mass. When ANSS is mixed with soil or gravel material, ANSS reacts with the mineral elements in the material to form new, stable soil particles. The process also creates cohesion between the newly formed stable particles and reduces inter-particle voids owing to crystal formation that renders the layer less permeable to water.
“After being stabilised, the base and subbase materials were placed back into the pothole and compacted. The ANSS-treated repair layer was immediately given a bitumen emulsion tack coat and sealed with cold mix asphalt. The road was reopened within an hour after the work had been completed,” says Du Plessis.
He concludes that this method of fixing potholes allows for the use of unskilled personnel and encourages job creation through the development of working teams that could take charge of specific regions to repair all the potholes.