Communities and towns were allowed to develop linearly along the R61 Route through the former Transkei due to statutory control regulations not being enforced. Of particular concern was Section 8, between Libode and Mngazi which was severely impacting the safety of all road users. This is a typical challenge associated with Ribbon development in rural settlement areas. In response to reports received, SANRAL approved a road safety project involving the construction of bridges and livestock underpasses, widening of intersections and closing unsafe accesses. Benefits of the project would be two-fold; namely to improve road safety conditions for pedestrians and non-motorised transport in the area and to create employment using unskilled labour in the community.
The outcome would be achieved by upgrading intersections and structures. In so doing, access points onto the National Route would be formalised with minor roads linking the surrounding communities and directing local traffic to safe intersections along the R61.
The following issues had to be taken into consideration when planning the upgrading of the access roads:
- Low traffic volumes
- Following the existing ground levels
- As far as possible, to locate on existing tracks to minimise land acquisition
- Use inexperienced local Level 1 Civil Engineering (1CE) contractors.
This made traditional road pavement construction difficult. The project team appointed by SANRAL comprised of H & I Construction and Hatch Ltd. who investigated and implemented a range of alternative construction methods that could be built by inexperienced local 1CE contractors and, at the same time, maximise the use of local labour.
One of the alternatives implemented was that of constructing roads using Kaytech’s proven Multi-cell® PP system. Multi-Cell® PP is a honeycombed, cellular structure manufactured from strips of a coated slit film. This woven polypropylene tape is stitched together to form three-dimensional diamond shaped cells. It is used as an in-situ shuttering to cast continuous, interlocking concrete paving for road or canal construction.
Panels of bespoke width Multi-Cell® PP were laid down on top of a 150mm thick compacted G7 base layer and tensioned using a tension frame. The 200mm x 200mm cells of the Multi-Cell® PP were then filled with 25 MPa concrete. The benefit of this pavement structure was that the base layer could be compacted with a pedestrian roller without causing any structural damage to the houses on the adjoining properties.
Due to the simple installation procedure the inexperienced 1CE contractors soon became proficient in installing the Multi-Cell® PP concrete road system. The uniform 75mm and 100mm cell height assisted the contractors in spreading the concrete to a consistent finished road level, with an acceptable ride quality. In total, 6.8km of road was constructed with widths varying between 4.0m and 6.0m depending on the road.
The Multi-Cell® PP system eliminates the need for steel reinforcement and construction joints. Due to the flexibility of the fabric cell walls, the concrete surface is able to accommodate some subsidence in the base layer. This is typically seen as cracks along the line of the cell walls. Despite this cracking the interlocking nature of the individual cells provides lateral load distribution that keeps the road intact and limits the ingress of surface water. As a result these low volume roads are expected to be usable in the long-term with minimal maintenance.
The cost of the Multi-Cell® PP roads was comparable to the other alternative construction methods implemented.
The project spanned almost three years and was completed in February 2019. When the consulting engineer visited the project in July 2021 he was satisfied with the performance of the Multi-Cell® PP concrete roads. Multi-Cell® provided an opportunity to minimise base and subbase categories. Future maintenance is substantially reduced as concrete provides a more durable finish than other road surfacing materials. There is also no requirement for future joint maintenance to prevent water ingress and growth of vegetation.
Multi-Cell® PP offers an excellent solution for the construction of durable, economical, low maintenance, low volume roads, while providing training and work opportunities for unskilled labour. The knowledge gained by the local 1CE contractors offers them a broader opportunity for future work.