Sustainable Materials in Road Construction

Kathrin Schilling

Published: 25 November 2019

Road construction is an ever growing business in most places of the world. The constantly increasing number of vehicles poses challenges to the road surfacing material and also the road base material. Safe, efficient and comfortable driving is a concern of nearly everyone - and the road construction materials industry has reacted with remarkable innovation. Generally known as a traditional sector in many countries, road construction has increasingly focused on performance enhancers for asphalt and bitumen.

The Importance of a Durable Roadway Surface

The goal of creating road building materials that ensure

  • optimal levels of friction between the road surface and the tyres
  • a high degree of evenness of the road covering material
  • advanced water drainage systems
  • appropriate light reflection of the road pavement material

Sustainable Materials in Road Construction

and possibly other characteristics, have made researchers look at alternatives to conventional techniques. Road building materials nowadays are sophisticated blends involving plant-based additives that have proven to enhance the overall performance. Cellulose fibers are known to boost stability of the asphalt mix, its homogeneity and to prevent segregation/erosion. These powdery raw materials have traditionally been wood-based, however, there are alternative road materials derived exclusively from agricultural by-products.

Innovative Road Construction Materials: Olive Stones in the Focus

Asphalt is generally composed of bitumen and small, granular rocks or sand as fillers. The bitumen is a viscous or liquid binder to keep the compound together. In the past, asphalt was often reinforced with polymer fillers, glass or carbon fibres. Beneficial outcomes were undeniable, however, a growing awareness of recycling and microplastics issues led to a stronger focus on recycled road base alternatives. Cellulose - one of the major constituents of refined olive stones - has been the solution. So how can the olive actually make a difference in new road materials?

Sustainable Materials in Road Construction

Research has mainly been conducted with micronized olive pit granules in the micron range between 100 and 500 μm. 10-15% of those granules were mixed with the bitumen. This modified bitumen was subsequently examined for an enhanced stiffening effect - with significant success. The improved stability (i.e. greater resistance to hot and cold temperatures) was subsequently examined over time to determine the asphalt's ageing (or stabilizing) behavior. A needle penetration test after 14 days revealed an increased softening point from 49.2 to 52.2°C. Considering the diversity of applied asphalt mixes, more specific conclusions can be drawn in tailored, client-centered research.

Further examinations were done to test the effect of olive fibers on the bitumen drainage behavior. Depending on the layer structure of the asphalt paving materials, more or less bitumen is generally lost due to a certain drainage of the liquid matter. A number of tests comparing fiberless bitumen with fiber-reinforced bitumen were carried out. Without entering into specifics, it can be concluded that drainage (i.e. loss of binder in the asphalt) could be reduced from around 13% to under 4%.

Sustainable Materials in Road Construction

Materials used in road construction are constantly developing. Polyethylene, polyurethane, polyester and glass fillers are for good reasons replaced by bio-based materials, which creates enormous innovation potential. Specialists at can provide professional advice based on your existing asphalt mix or new development. We work with companies worldwide, ship to any destination and make bespoke powders with hydrophilic or hydrophobic properties.

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