The modification of bituminous materials using tall oil pitch : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Chemical Technology at Massey University, New Zealand
There are economic, occupational safety and health, and environmental advantages in using tall oil pitch (TOP) as a bitumen extender. However, before bitumen modified with TOP can be used commercially in New Zealand, it must meet the requirements of the national specification for roading bitumen. The rheological and chemical properties of TOP modified bitumen were assessed before and after ageing samples as 1 mm thick films for 3024 ± 8 hours in an oven at 60°
C. An 80/100 bitumen was produced by blending 12% TOP with 40/50 bitumen. Similarly, 180/200 bitumen was produced by blending 25% TOP with 40/50 bitumen, 15% TOP with 80/100 bitumen or 6% TOP with 130/150 bitumen. The ageing index of the bitumen increased as the TOP content increased, which indicates that TOP modified bitumen is less durable than conventional bitumen. Increasing the TOP content caused both a decrease in the dispersability of the asphaltenes as measured by the Heithaus parameter Pa
, and an increase in the quantity of asphaltenes after ageing. However, analysis of the bitumen using gel permeation chromatography and confocal laser scanning microscopy showed that the size of the asphaltene aggregates remains in the range of 2 - 7 µm and is not affected by the TOP content or by ageing. The acid value of the bitumen is proportional to the TOP content and is unaffected by ageing. TOP modified bitumen is compatible with kerosene and AGO in proportions commonly used during chipsealing. Although TOP had an adverse effect on the effectiveness of adhesion agents used during chipsealing, it improved the resistance of asphalt concrete to moisture damage. Because of its poor ageing characteristics, asphalt concrete manufactured using TOP modified bitumen is more likely to suffer from fatigue cracking and ravelling, but it less likely to rut or produce tender mixes. The use of TOP as a bitumen modifier in NewZealand is not recommended since it lacks both durability and compatibility with adhesion agents as required by the national bitumen specification. Future research should concentrate on improving the resistance of TOP modified bitumen to age hardening and improve its compatibility with adhesion agents. Keywords: Tall oil pitch, bitumen, asphalt, asphaltenes, ageing, oxidation, durability, GPC, confocal laser scanning microscopy, interfacial tension, adhesion.