Papers by Keyword: Foamed Bitumen

Abstract: Foamed bitumen is a binder of cold mix road recycling materials. It is necessary to understand the best foamed bitumen properties prior to mixing with aggregate materials. Viscosity is one of the important properties, which facilitate the foam to distribute across the aggregate phase in the mixing process, and form a well coated asphalt mix. Unfortunately, the understanding of foamed bitumen viscosity and its contribution in the development of mixture performance is still poorly understood. This paper discusses foamed bitumen viscosity which was explored based on theoretical studies and a series of laboratory investigation. Foamed bitumen was produced using bitumen Pen 70/100 at temperature of 180°C. The research method was developed in three activities, i.e. (1) the previous studies on the foamed bitumen rheology, (2) investigating flow behavior of foamed bitumen, and (3) estimating foamed bitumen viscosity using Kraynik equation.The research results can be summarized in the following three points. First, foamed bitumen consists of gas content and liquid bitumen, in which the value of foam viscosity increases with the gas content. Second, foam flow can be used to indicate the apparent foam viscosity. Foamed bitumen with a higher foaming water content (FWC) tends to have a decreased flow rate and hence higher apparent viscosity. Third, foamed bitumen viscosity estimated using Kraynik equation is affected by gas content and liquid bitumen viscosity. It was found that an ER_m of around 35 (or at FWC of 6%) is the critical area of foam viscosity.

Abstract: This study investigated the effects of different active filler types and contents on the mechanical properties of foamed bitumen treated materials under laboratory conditions. Four different active fillers were tested namely Portland cement, hydrated lime, quicklime and fly ash, at varying concentration of 0%, 1%, 3% and 5%. To evaluate the effects of the additional active fillers, samples were prepared under laboratory conditions and tested using indirect tensile strength, indirect tensile resilient modulus and unconfined compressive strength tests. Based upon our findings, all active filler types except fly ash contributed in improving the strength of foamed bitumen mixtures at different levels. Cement, regardless of adding contents, always provided the highest mechanical performance compared with the other two counterparts: hydrated lime and quicklime. Fly ash was deliberated to be precluded because fly ash on its own did not affect any mechanical strength of foamed bitumen mixes instead it acted as a mineral filler to modify aggregate gradation. The addition of active filler content should be limited within 3% in terms of strength gain and potential cracking prevent when mixing with 4% foamed bitumen content and locally sourced raw materials for base course.