The South African National Road Agency (SANRAL) has reported that the country has now more than 25 million potholes which have a 67% increase since the number reported in 2017. The increase in pothole damage can be attributed to reduced preventative maintenance being applied to many roads, combined with particularly wet periods during rainy seasons and rapidly increasing numbers of heavy vehicles. Numerous claims have been laid against road authorities for vehicle damage caused by potholes and even for serious vehicle accidents resulting from excessively large potholes.
A general understanding of the main cause associated with potholes is that moisture permeates the pavement structure, and freezes during winter resulting in an increase in volume and a consequent decrease in material density. The climate in South Africa, however, is such that this problem can be considered minimal and not an important contributor to the overall pothole problem. There is no doubt that water is the primary cause of potholes, with the access of water into the road structure to cause potholes being mostly a function of surface condition however, due to a lack of periodic and/or preventative maintenance of roads leads to the development of surface cracks, which allow rapid ingress of water into the structural layers during rainfall.
Potholes in asphalt originate in two ways; the cracking of the asphalt because of fatigue or aging (binder shrinkage) that allows water into the support, or by the penetration of water to a less permeable interface within the asphalt layer, resulting in stripping of the asphalt. The CSIR gives a technical guide to the causes, identification, and repair of potholes. The document summarizes the main causes of typical potholes and ways of limiting their formation.
As towns grapple with the ever-increasing commuting populations and a growing list of infrastructure needs, tackling potholes has become an important part of a larger effort to maintain the quality of life for citizens. When it comes to keeping our roads in good condition, local government often relies on engineers and other technical professionals. This is because patching potholes should not be taken as simple as filling them up with asphalt, – there are certain engineering considerations that need to be considered to ensure that streets are kept safe for motorists and pedestrians alike.
The first type of asphalt that typically comes to mind when pothole patching is mentioned is cold-mix asphalt, a less expensive mix made mostly from recycled materials. This is suitable primarily for temporary repairs due to its shorter lifespan than other options. Cold mix can easily plug holes quickly but will not last as long as some alternatives like hot or warm mix which makes it more ideal for short-term fixes instead of permanent patches since over time the surface may begin deteriorating again rapidly.
Many instances are observed where pothole patches have failed. This is normally the result of either the original cause of the problem not being addressed or the effect of poor patching workmanship. Thankfully, companies like Ditlou Consulting Engineers notice that beleaguered communities deserve long-lasting solutions to pothole safety concerns that enrich citizens’ quality of life. In 2019 Mogale City Local Municipality appointed Ditlou Consulting Engineers to provide roads and stormwater services in Rietvlei Extension 1 and Proper. Surfacing overlaying and patching was needed on various roads as the existing roads experienced surface and structural failure due to inadequate road maintenance and stormwater.
The solutions implemented by Ditlou Consulting in ensuring that the pothole patching done using a cold mix asphalt would be long-lasting was to ensure that once the potholes had been patched using the cold mix then a surface overlay would follow using the hot mix asphalt. Further to that, crucial quality procedures after patching the potholes with a cold mix of asphalt were strictly abided and these were to:
- Making sure the repaired area matches existing pavement texture achieving seamless integration between new and old pavements to match as closely as possible in surface texture offering a superior traction characteristic and,
- Ensure freshly patched areas are leveled off correctly before allowing traffic back onto them at any speed lower than normal cruising rates – otherwise, this could cause other potentially disastrous effects such as irritable ‘moon’ craters appearing around poorly ranked settlements.
Warm Mix Asphalt (WMA) also provides better workability of compaction as compared to HMA (Hot Mix Asphalt). It utilizes advanced technology called foaming agents that lower production temperatures by allowing airflow into the mixture making it easily workable. This material property, however, allows WMA’s superior performance in terms of durability versus regular HMA because energy consumption levels drop significantly during construction without sacrificing strength properties – all while reducing costs & emissions simultaneously! Additionally using WMA does not cause odors or dust pollution so there’s little impact on the environment and disruptions for those living near the roads being repaired/paved.
Finally, recently developed polymer-modified emulsion mixes have become popular thanks mainly due to the incredibly strong adhesions achieved between layers. These systems create patched areas unlikely to crack and crumble even after adverse weather.