Institute of Food Research, NARO

Renewable resources help make roads stronger!

- An asphalt modifier prepared from starch-

The National Agriculture and Food Research Organization(NARO) has developed the starch-based asphalt modifier C-AG. C-AG disperses fibrously in asphalt, improves the flow resistance of asphalt and helps in prolonging the road life. By means of using this newly developed asphalt modifier, energy consumption related to modified asphalt production and road construction is lower when compared to conventional asphalt modifiers, and Greenhouse gas(GHG) emissions can be expected to be reduced.


Starch is abundant in rice and corn and is an important source of nutrition for the mankind. Also, it is an excellent renewable resource because the cycle in which plants store starch is short. Starch has been used so far in the fields of textiles and papermaking, but in recent years, it has been grabbing attention as an alternative material to fossil resources in other fields as well. In this research, we have developed an asphalt modifier from starch, which is a renewable resource. This asphalt modifier contributes to the extension of road lifespan and reduction of GHG emissions associated with road pavement.

Asphalt used for road pavement becomes softer and more fluid when it reaches the road surface temperature of 60°C in midsummer. However, if a car passes in such condition, uneven ruts will be created on the road surface, and the road has to be repaired. Therefore, in order to improve the flow resistance of asphalt near the road surface temperature in summer, Polymer-modified asphalt has been developed by adding petroleum-based polymers to asphalt and improving the viscoelasticity of asphalt. However, high temperatures of around 180°C are required to disperse petroleum-based polymers in asphalt and to construct roads using polymer-modified asphalt. This will result in issues such as large amounts of energy consumption, associated GHG emissions, and harsh working environment.

Therefore, in this research, we have developed the asphalt modifier C-AG, which improves the flow resistance of asphalt and realizes the manufacture and construction of modified asphalt under lower temperature conditions. The asphalt modifier C-AG can be produced in large quantities in high yield by reacting starch-derived natural sugar 1,5-anhydroglucitol with fatty acids. C-AG disperses in asphalt at temperatures below 130°C and forms a fibrous structure in the asphalt when cooled. It was revealed that the C-AG modified asphalt containing this fiber has the same level of fluidity resistance as the polymer modified asphalt at 60°C.

This technology makes it difficult to dig ruts even under the road surface temperature in summer, and so the road life can be prolonged. At the same time, it is expected to contribute to solving various problems such as reduction of GHG emissions related to road construction and improvement of working environment.


Rika Iwaura, Shiro Komba "Modification of asphalt by starch-derived supramolecular fibers: A simple way to tune flow resistance" ACS Sustainable Chemistry and Engineering,

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