Cold Mix Asphalt Plants enable the Recycling of Road Materials

Cold mix asphalt plants are changing the way road maintenance is carried out. Asphalt is the road construction material of choice, due to providing skid resistance on roads, speed of installation (vs concrete) and has excellent durability, among other benefits.

These days, after completing repairs, companies are no longer faced with leaving piles of leftover material on the side of the road to be disposed of later.  It is now possible to crush or grind the old layers of the road surface on-site, first using a crusher and then putting crushed material into the mobile mixing plant, together with the special emulsion, concrete and water as required.

These different materials are mixed on-site in batches as needed to create cold asphalt.  The road surface is then laid using this new composite, without the heat and fumes of traditional road repair and replacement.


Asphalt is produced in a plant that heats, dries and mixes aggregate (eg gravel, crushed stone, slag, or rock dust), bitumen and sand into a multi-part mix. It is then fed into a paving machine on the construction site and used as a solid material in a required thickness.

Bitumen, one of the parts used to make asphalt, is obtained by the partial distillation of crude petroleum. It is known for being strongly adhesive and resistant to damage from water or oil spilt on it. This makes bitumen the ideal binding agent for asphalt, which is commonly used as a surface for roads, car parks and driveways.

Bitumen is sometimes confused with tar, which is another binding agent, which, when mixed with aggregate, makes tarmac. Tar is a very sticky liquid which contains high amount of carbon.

How IS asphalt recycling BEING USED?

Asphalt recycling offers an economical solution to road maintenance by re-using all the existing roadbed aggregate and asphalt. By doing this on the road repair site, interruptions to traffic flow are kept to a minimum, since the final surface material can be driven on immediately following rolling.

When considering a road surface damaged by cracks and/or potholes, a construction engineer can fix these deformed areas or irregular thickness of road surface layers by using cold asphalt processing to repair the existing road top. 

Zimbabwe’s Road Building and Restoration Project

Use of modern equipment and this recycling technology will be regarded as particularly useful in the massive road infrastructure development and upgrade projects currently being considered by the Zimbabwe Government as part of their Vision 2030 strategic plan. Work has already started in Zimbabwe’s eight provinces targeting an overall 781km of highways throughout the country for renovation or expansion, including:

  1. Beitbridge to Victoria Falls – the existing two-lane road via Bulawayo will be widened and restored, so that there are two lanes in either direction. 22 new bridge crossings are also being built as part of this work. Upgrading the route will help boost tourism for Victoria Falls (one of the Seven Wonders of the World) and the Hwange National Park. The highway is also an important transport route for Zimbabwe, as it connects with the trans-African highway.
  2. Chirundu to Beitbridge – this highway will connect Zimbabwe’s borders by road, with Zambia to the north and South Africa to the south and runs through Zimbabwe’s capital, Harare.
  3. Kanyemba to Mount Darwin – this road connects the southern African region via Mozambique and is already under construction, with only 34km left to finish the road to the Mozambican border. The completed roadway is expected to improve trade and regional connectivity.

Blend Plants’ machinery, particularly their batch mobile mixing plants, [link to be added when article is uploaded and live] is highly suited for tender-awarded contractors who can now use the old bituminous road surfaces when stripping back a road to repair it. Both large and small contractors can benefit using this equipment. 

“This is the ultimate in recycling for road repair”, a recent press release from MMI (Pvt) Ltd noted. “The recycling process produces a high-quality product which hardens with compaction; absolutely no heat is required.” In addition, Blend’s concrete mixing equipment and their add-on horizontal silos for storage will also be of immense use in this road network initiative.

What are the benefits of recycling with MOBILE ASPHALT MIXING PLANTS?

As road asset management is progressively switching from new construction to maintenance, this has led to a changed approach to resource optimisation.

Asphalt recycling reduces the development of new quarries for the road materials and therefore lessens the impact of mining on the environment.  Transport costs not only of materials to the site, but also man-hours to remove the old road surface refuse, are vastly reduced, so making road and pothole repair more affordable.  The time taken to repair and resurface roads is also reduced, as well as the carbon footprint lowered by fewer vehicles circulating to and from the worksite.

Other benefits include:

  1. Sustainability and energy saving – lower impact on the environment and use of fossil fuels results in environmental benefits.
  2. Safety – a decline in dust and noxious fumes for road building employees to come in contact with, as well as the issues related to dealing with hot asphalt.
  3. Excellent workability – combined with the right equipment, various types of road degradation can be repaired almost permanently, for example cold patching for potholes.
  4. Proven results – the laboratory results of cold asphalt technology show the Real Time and Comparative Tracking Index (CTI) performance tends to improve over time. This means that cold asphalt is able compete in strength with hot asphalt.
  5. Use in other applications – it is also possible to use recovered asphalt for other engineering purposes. This is sometimes known as “Downcycling”, as the recycled material does not go back to its original use, but into an alternative less demanding application.

It’s a Win-Win result for road maintenance

Cold recycling of asphalt road materials has proved to be an effective maintenance and renewal technology for both environmental and economic reasons.

It should be noted, however, that using cold-recycled asphalt mixtures still requires engineers to carefully assess the suitability of product’s properties, especially when they are designed to replace traditional hot-mix asphalt concrete mixtures.

Innovation is a fundamental feature of Blend Plants Africa, paying attention to all aspects of the construction industry. Their professional teams recognise customer challenges and needs, leading to the development of solutions that will beneficially impact such activities.  Blend Plants’ goal is to offer equipment that will improve the quality, the efficiency and, particularly, the profitability of all their customers’ projects.

MMI’s BLEND Plant solutions can cater for a wide choice of applications whether it be stabilisation cement, bridge mix, laboratory specified mix, colour cement, backfill, cold asphalt or standard concrete. Contact Blend Plants for more information on your specific needs.