PAVING NEW LANES
Roads are the aorta of an economy and it is critical to keep them healthy, but realistically, many roads in South Africa are more like torn aortas. Persistent potholes are a symptom of roads in need of reconstruction and in the fragile state of these transport arteries, it will take prime quality cement to put safe and strong surfaces back on the road.
Real high cost of poor roads
Any motorist who has hit a ghostly pothole will know first-hand about annihilation of tyres/rims and the high replacement cost, and that’s for light vehicles. Consider the danger that poor condition roads pose to commercial vehicles and their drivers, as they work long haul shifts to deliver heavy loads safely to keep the wheels of commerce turning.
Statistics bring the high damage zone home as at November 2020 in the 2019/20 financial year, it was stated by the Transport Minister that government had received pothole damage claims valued at over R5.2 million lodged against the department. Many of these claims were valued at over R100 000.
A second statistic to consider is that between 2005 and 2019 South Africa was the largest commercial vehicle market in Africa. Whilst the global pandemic may have imploded economies and vehicle sales declined in 2020, the trip metres of fleets had to keep running and existing commercial vehicles continued to operate through Lockdown, as roads did not “stay home”.
Motorist and cargo safety are two of the major reasons why sustainable roads must consistently be built or rebuilt and maintained. It is also imperative that we are smart in how we rebuild the local economy following the negative impact of Covid-19, and cement-concrete provides us with the smartest of binding and stabilisation materials.
Total construct for concrete roads
In these conditions what are the solutions to consider? The Hellenic Cement Industry Association sums up benefits of concrete roads, saying:
“The contribution of cement and concrete to transportation and particularly to road construction is considerable. Bridges, tunnels, safety barriers, concrete: roads and sound barriers are several examples of successful cement/concrete applications. A characteristic of the use of cement in the aforementioned applications is the small maintenance cost together with the elongation of the service life of the structure.
In road building, cement is also used for the treatment of aggregates and the stabilization of soils. The production of cement binding mixtures, contributes to the upgrade of the bearing capacity of sub grade along with an increase of the bearing capacity of the pavement layers. This increased bearing capacity provides the ability to construct road surfaces of lesser thickness and thus of a significantly lower cost.”
Cement-concrete pavements, says the association “form an unrivalled type of paving for highways, roads of heavy traffic and simple rural and urban roads.” They point out benefits such as low tyre wear, reduced total cost in service life cost analysis, high durability, better visibility for motorists, and a low maintenance cost.
Technicalities under the road surface
Cement must deliver strength, frost resistance, resistance to chemical de-icing agents, abrasion and absorptivity to road construction project teams.
A Polish technical paper by ScienceDirect highlights the importance of the two strength parameters, namely compression and bending. “The results of determination of strength classes for standard use surface finishes in Poland should be in class C25/30 ÷ C40/50. Tensile strength on bending is tested on 15×15×7cm samples by bending them with a four-point load. ”
The authors stipulate that absorbability of the topcoat must be within 5% and in terms of abrasion, note that this “is mainly dependent on the strength of the aggregate slurry binding the aggregate. Its size is usually determined by the weight loss or the original dimensions of the samples. …” adding that the value of abrasion during testing for road surfaces should not exceed 4mm.
Closer to home, Concrete Trends (2019) stated, “Nigeria, for a start, now seems totally converted to concrete roads.” With 80% of road construction materials in the country being imported at the time and nearly R14 billion having to be paid for asphalt road repairs, the Dangote Group formed a partnership with the Nigerian government to address these issues.
In the article the Founder of the Dangote Group and Sephaku Cement Chairperson, Aliko Dangote explained:
“It is cheaper to build a concrete road that will last 50 years than be faced with the constant maintenance required by bitumen-based roads. Our Group’s decision to help introduce concrete roads in Nigeria is in line with the experience of other countries worldwide. For instance, the famous Autobahn in Germany was constructed with concrete and India’s popular Marine Drive in Mumbai, built in 1939, are just two examples of the durability of concrete roads.”
In our South African market, in particular, there are some best practice projects underway to construct durable roads. One of these projects is covered in Part 2 of this Paving New Lanes series by Sephaku Cement where we focus on the TRAC N4 rehabilitation and expansion project case study in which Raubex Construction and Sephaku Cement are smart at work to build this highway for tomorrow.