Waterproofing roads using nano-modified emulsion could reduce potholes, expert says

10th July 2023 By: Marleny Arnoldi - Deputy Editor Online

University of Pretoria (UP) Department of Civil Engineering Professor Gerrit Jordaan has said the key to solving South Africa’s pothole problem is using modified emulsion and nano-materials, which he noted were inexpensive and already being manufactured in South Africa.

During a session of the Southern African Transport Conference, which is being held from July 10 to 13, in Pretoria, he explained that the main problem with pavement structure was water infiltration and resultant cracking, stressing the need for preventing potholes by resurfacing roads with the correct materials instead of having to keep fixing potholes that reappear.

Jordaan shared that the size of a bitumen particle is between two and five nanometers, while a water particle is 0.5 nanometres in size, meaning the water has deep penetration capability in respect of bitumen. South Africa currently has manufacturers making nano-polymers sizing between 60 and 80 nanometers, and nano-silanes between two and five nanometres. Nano-silanes of 0.5 nanometer in size are available for import.

He added that, with the correct mineralogy mix, an emulsion can be made to chemically attach to aggregates and thereby create more composite and tensile strength against water and temperature.

Additionally, nanomaterials can be applied by hand sprayer, with very little training required. Jordaan noted that the correct amounts of material can be applied according to the condition of the road, to reduce wastage.

He suggests a process of cleaning a pothole, filing it with water-repellent pothole mix and filling it with nano-modified emulsion. Local deformations in wheel tracks can then be made, before applying a waterproof slurry for longer road life.

The manual labour nature of this process creates opportunities for local employment and small business development.

By building a nano-modified base, the university has proven that it will withstand water penetration. “There is no silver bullet here, and there is no perfect bitumen emulsion off the shelf. Hence, the need for a material compatible solution that creates chemical bonds between the minerals in the material, added nano technology and bitumen emulsion to firmly attach to the aggregate,” Jordaan said.

He suggested that government, in its roads tenders, start specifying the engineering properties that are required in terms of compressive strength and tensile strength, as well as durability.

In turn, durability is determined by getting information on hydrophobicity. Jordaan added the quality of bitumen emulsion procured has a huge impact on quality of the road, and government often favours the cheaper cost tenders in this regard.

To this end, Jordaan recommended that more engineers become familiar with chemistry and, as part of the product specification process, require a contractor to guarantee that a product will be stable on site, in the sun and in the rain, for at least four months without any increase in viscosity or any visible separation.

However, he pointed out another challenge as being political will to commit to a budget, setting funds aside and monitoring spending accordingly.

UP Department of Construction Economics Professor Kevin Wall agreed, saying that factors impacting the underlying state of repair of infrastructure such as roads should be considered, particularly as the public becomes more aware of the impact of failing service delivery.

He agreed with Jordaan that there had been limited success with permanently fixing road faults, which, coupled with maintenance deferral, more destructive service delivery protests and greater vandalism in the country overall, required a more long-term and fiscal-friendly solution, such as partnerships with the private sector.

Wall pointed out paved roads in the major urban and metropolitan areas as being a particular area of concern, given its “report card score” in South African Institution of Civil Engineering’s Infrastructure Report Card. The report card shows a decline in the condition of paved roads in major urban and metropolitan areas from a score of C in 2006 to C- in 2011, and D- in 2017 and 2022, which implies the condition of the road network leaves much to be desired and poses a risk to safety and the economy.

This while provincial and municipal unpaved roads have been at a consistent score of E, meaning it is dangerously damaged and defective. Paved provincial roads also sit at a score of D as of 2022, while national roads sit at B+.

Jordaan concluded that the only way to save the surfaced road network is through labour-intensive water-proofing and restoration.