Optimal Tempererad Asfalt - OTA - en undersökning av asfalt med Sasobit

Sammanfattning: The concept of OptimalTempered Asphalt, OTA, stands for the best temperature all aspects considered for the bitumen and the manufacturing process as well as the end-product. This is achieved in various ways using additives, choice of manufacturing procedure and changing mixture of asphalt. This bachelor thesis is a study of the effects the additive Sasobit has on bitumen and asphalt from an OTA perspective. The supposed lubricating effect induced by Sasobit and possible stiffening effects are examined. Sasobit is used globally in various countries and has been used in Sweden in a large scale over the last decade. Positive effects such as increased manageability at lower temperature have been noticed by producers. The asphalt was produced in a full scale asphalt plant. The type of asphalt was a base course asphalt and specimens were made using a Marshall impact compactor, but with variations in the number of blows and two temperatures. The specimens were tested for air void content, stability and indirect tensile strength while extracted bitumen was tested to determine viscosity and needle penetration. All tests were carried out following current Swedish Standards with a few documented deviations except the determination of viscosity where test procedures were set by manufacturer of the Brookfield Viscometer. There were no conclusive results in our specimens air void content with wax which would explain the lubricating effect mentioned by producers and those who first hand work with asphalt containing Sasobit. Bitumen containing Sasobit had a slightly lower viscosity above temperatures of 100°C where the wax is melted. While below the melting point there was a substantial increase in viscosity compared to bitumen without wax. This difference in viscosity and stiffness was at its maximum at temperatures around 60°C. The wax continued to have a stiffening effect on bitumen at the needle penetration test which was carried out at 25°C but as the temperature falls the effects of Sasobit are overtaken by the stiffening effects of bitumen. Marshall Stability and Marshall Quotient were very much elevated from the use of Sasobit at 60°C while in the Indirect Tensile Strength test at 10°C was very little affected regarding stiffness and the failure value.