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Within the interior infrastructure of many countries, rural and secondary roads form a vital backbone network for vehicle transport. These roads are lifelines for rural communities, providing access to essential services, markets, education, and healthcare. On a broad scale, they are often constructed as gravel roads – and therefore may face challenges such as poor maintenance, extreme weather conditions, and limited funding – all of which may lead to rapid deterioration and unsafe travel conditions.
Gravel Wearing Course (GWC) is a vital component in constructing safer, more durable roads in general. But unlike paved roads, gravel roads do not have asphalt or concrete surfacing. Gravel Wearing Course comprises the uppermost layer of a gravel road, and therefore directly bears the wear and tear of traffic and exposure to the elements.
As a result, it must be composed of a blend of aggregates that offer sufficient strength, durability, and grading to resist deformation and erosion. This makes the quality and composition of the gravel layer critical. When properly designed and maintained, a well-graded Gravel Wearing Course can significantly extend the lifespan of a road and enhance safety.
Key aspects of road safety
Improved traction and skid resistance
One of the most critical safety concerns on rural roads is vehicle skidding, especially during wet conditions. A properly designed GWC ensures adequate friction between tires and the road surface, reducing the risk of accidents. The angular nature of well-graded gravel provides better traction compared to rounded particles that tend to roll under pressure.
Smooth driving surface
A smooth, well-compacted gravel surface minimises vehicle bouncing and vibration, leading to safer driving conditions. Poorly maintained gravel roads are prone to potholes, rutting, and corrugation, which increase the risk of vehicle damage and driver fatigue.
Drainage and water management
Surface water is a significant threat to road stability. The gravel wearing course plays a vital role in shaping the road crown and side slopes, ensuring proper drainage, which reduces erosion and prevents the formation of mud holes and soft spots that often compromise driver control and road usability.
Visibility and dust control
Excessive dust on gravel roads can reduce visibility and, additionally, cause respiratory problems. A well-graded GWC, possibly treated with dust suppressants such as calcium chloride, helps to bind fine particles and limit dust emissions, thus improving both safety and public health.
Extending the durability of gravel roads
In rural and secondary roads, especially those exposed to seasonal rains or harsh sun, the GWC acts as a protective layer. It shields the underlying structural layers from moisture and temperature fluctuations. This reduces the likelihood of the base material weakening and subsequent road failure.
- Load distribution: Gravel Wearing Course helps distribute vehicle load across a broader area. In this way, it reduces stress on the lower layers – a load-spreading effect that is crucial in areas where there is heavy agricultural or transport equipment presenting considerable axle load.
- Erosion control: Through proper grading and selection of materials, the GWC resists surface erosion caused by water runoff. This is especially important on hilly or undulating terrain, common in many rural areas, where erosion can wash away the road structure in a short space of time if not addressed quickly and effectively.
- Maintenance flexibility: Gravel roads with a well-constructed wearing course are relatively easier and cheaper to maintain than paved roads. Grading, re-gravelling, or spot repairs can be conducted with local materials and labour, empowering communities to participate in road upkeep and enhancing road sustainability.
TRH Specifications
TRH20 is a technical guideline developed by South Africa’s Department of Transport that provides standardised criteria for the selection, grading, and application of gravel materials used in road construction. It is critical for the design and maintenance of gravel roads, ensuring both safety and longevity, and is an especially vital practice in South Africa, where rural and secondary roads form a major part of the transport network.
By adhering to TRH20, road engineers ensure that the gravel wearing course has the correct grading envelope, sufficient plasticity, and adequate compaction properties — all essential for roads exposed to heavy vehicles, erratic weather, and limited maintenance budgets.
Poor road conditions can severely impact livelihoods, and therefore, compliance with TRH20 is not just a technical requirement; it’s a foundational practice for building resilient, cost-effective, and safer gravel roads that support South Africa’s development goals.
From Quarry to Quality: Building the Future with Safer, Longer-Lasting Roads
Lime Sales offers a variety of products used in both the construction and civil construction industries, as well as the agricultural sector. We take pride in delivering products that are fully compliant with industry regulations and tailored to our customers’ specific needs.
Contact our sales team for pricing, product availability, and tailored solutions to suit your soil health or construction material requirements.
Find out more at: www.limesalessa.co.za
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