Bituminous binders and slurries for road-surfacing specialist manufacturer and applicator Colas South Africa completed 700 000 m2 of road reseal for Mogale City local municipality, including several roads in the Krugersdorp Nature Reserve, over the past three years.

For the project, which amounted to about R38-million, Colmat L microsurfacing and patching, fogspray and line marking were used. The Colmat range comprises Colmat N, Colmat L, Colrut and Colpave, which can be used for different applications.

Colmat L is a cold microsurfacing system that seals aged and damaged road surfaces. It contains a cationic quickset bitumen emulsion mixed with selected crushed mineral aggregate, cement and water, which is applied with an improved purpose-designed slurry machine system, supplied by Colas.

The product prevents the ingress of water into the underlying layers of a road by filling the cracks and voids of the existing surface, and improves durability by preventing further oxidation of aged binder in the existing surface.

“Colmat L offers the ultimate road-sealing solution in a complete package using Colas leading-edge technical expertise, extensive experience and support during application,” says Colas South Africa commercial, communications and marketing manager Herman Groenewald.

He explains that Colmat L system is a specially formulated quick set cationic microsurfacing bitumen emulsion modified with styrene-butadiene rubber (SBR) latex for mixing with selected continuously graded crushed aggregate, cement and water by means of a slurry machine.

“SBR latex improves the temperature susceptibility of the binder and the aggregate adhesion, which reduces the risk of aggregate loss, especially in the early life of the seal.”

Groenewald says the system is a cost-effective remedial treatment for improving the road profile and skid resistance of an existing blacktop surface or concrete pavement. He points out that the product can be applied in one pass of between 5 mm and 20 mm on urban streets, highways and airports.

Using Colmat L allows for the surface to be used by traffic within 90 minutes of application during normal weather, with ambient temperatures not exceeding 35 ºC, and providing that the reactivity of the aggregate is favourable.

“Working during the winter months has its challenges as Colmat L cures slower in lower temperatures. However, we overcome this by adjusting the chemical formulation of the emulsion to enable it to cure quicker, thereby enabling us to reopen the road for traffic.”

Groenewald says, when compared with other surfacing types, microsurfacing results in a low tyre noise of the final surfacing, with no harmful emissions during application and curing.

“Workers and pedestrians’ health and safety are assured during and after application, owing to Colmat’s environment- and user-friendly cold mixing and laying process, and our improved application slurry machinery.”

He says applying Colmat L on a road enhances surface roughness and micro texture through the aggregate grading used.

Groenewald adds that the application process guarantees minimal disruption to traffic prior to its application as there is no need to lift curbs and manholes, and no tack coat is required.

Further, the Colmat system is complete, with no additional on-site construction plant required.

“As your partner throughout the process, Colas assists with aggregate selection and product mix design; we will provide the required specialised equipment and personnel. Colas’ technical and support team significantly reduces your risk and creates added confidence – especially in the application process,” Groenewald concludes.