Determination of Mixing and Compaction Temperatures ... - ijcebm

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Mixing/Compaction temp. o C 250 240 230 220 210 200 190 180 170 160 150 International Journal of Civil Engineering and Building Materials (ISSN 2223-487X) Vol. 2 No.4 2012 © 2012 International Science and Engineering Research Center Hydrated lime mix.temp Lime mix.temp Cement mix.temp Hydrated lime comp.temp lime comp.temp Portland cement comp.temp Hydrated lime mixing temp.polyline Hydrated lime com.temp. polyline Portland cement mix.temp. polyline Portland cement comp.temp. polyline Limestone mix.temp. polyline Limestone comp.temp polyline 140 0 0.3 0.6 0.9 1.2 1.5 Dust to binder ratio Fig. 4 Mixing and Compaction Chart for No.70 Asphalt Mastic at Different Filler type and Content Discussion of Test Results Based on the generated results the following is observed: Viscosity: Viscosity in all mastic samples at same dust content decreases with increasing test temperature. Viscosity is a well defined linear function of increased mineral filler to binder content and temperature. The viscosity follows the behavior of plain asphalt at increased temperatures with a positive shift due to the stiffening effect from mineral fillers. Portland cement and limestone mastics show a similar trend of viscosity increase at increased temperature while hydrated lime mastics show a more significant viscosity response with temperature increase than other mastics. The comparisons of figures 1, 2 and 3 reveal that the ranges of initial viscosities for asphalt mastic tend to increase relative to that of plain asphalt mastic with increasing testing temperature and mineral filler content. Mixing temperature shift: Asphalt mixtures mixing temperature determined from viscosity-temperature charts at different mineral filler to binder ratio contents using the equi-viscous line of 0.170±0.02 Pa·s, shows an increment of 7.7 o C per 0.1% increment of hydrated lime and 5.3 o o C per 0.1% increment of Portland cement while limestone is 3.4 C per 0.1% from that determined from a neat binder. Compaction temperature shift: Compaction temperatures determined from equi-viscous line of 0.280±0.03 Pa·s for asphalt mixtures shows an increment of 7.9 o C per 0.1% increment of hydrated lime and 5.4 o C per 0.1% increment of Portland cement while limestone is 3.5 o C per 0.1% from that determined from a neat binder. Mineral filler equivalent factors for mixing temperatures: At 0.6 hydrated lime dust to binder ratio content the effect on mixing temperature increase is equivalent to 0.722 Portland cement and 0.735 pulverized lime. 164
International Journal of Civil Engineering and Building Materials (ISSN 2223-487X) Vol. 2 No.4 2012 © 2012 International Science and Engineering Research Center Mineral filler equivalent factors for compaction temperatures : At 0.6 hydrated lime dust to binder ratio content the effect on compaction temperature increase is equivalent to 0.706 Portland cement and 0.748 pulverized lime. Asphalt grades: Asphalts, within a given grade, do not differ substantially in their rheological properties, however it is advisable to carry out all the conventional binder tests before using these developed mixing and compaction temperature mastics graphs to check for rheological consistency. In aggregate stockpile, a small amount of dust or mineral filler is usually found as a result of natural degradation or as excess fines/dust after the crushing process of larger aggregates. For this practical reason, mineral filler is included in the aggregate gradation and the filler also serves to give a continuous size representation in aggregate gradation. However, mineral filler exerts a significant effect on the characteristics and performance of asphalt mixtures, such as ; decreased optimum asphalt content, higher filler concentrations result in stronger pavement due to better asphalt cohesivity as well as internal stability from the good packing contributed by the filler, the inclusion of mineral filler increases resilient modulus of asphalt mixtures, also excessive filler may weaken the mixture by extending the amount of asphalt or simply makes the asphalt stiff and consequently affecting the workability of the mixture, mineral fillers affect the engineering properties of the parent binder. Therefore, inappropriate amount of the mineral filler may lead to instability, rutting, moisture damage and cracking of the resulting asphalt mixture. Understanding of the effects of mineral filler additives to asphalt mixtures is very important prior to undertaking this task to avoid the aforementioned problems [7]. Summary and Conclusions This study has presented a comprehensive methodology for the determination of mixing and compaction temperatures shift curves for No. 70 asphalt mastic at different type and content of mineral fillers. Test data presented in this study leads to several important conclusions as below. Due to stiffening and extension effect on original binders caused by mineral fillers, effect on viscosity is demonstrated. Fillers increase the viscosity at increased dust levels and hydraulic lime shows a more significant increment as compared to other fillers. Mixing and compaction temperature curves for No. 70 petroleum of China asphalt mastic at any different dust to binder ratio have been established using the figures generated in this study. Equi-viscous concept can be used to determine mixing and compaction temperatures for asphalt mixtures from asphalt mastics whose base binder is unmodified asphalt cement. The utility and significance of extensive tests evaluating the properties of asphalt binders in their original state are questionable without fillers. The measurement of paving mixture properties, rather than plain binders appears to be more rational. In paving mixtures, at temperatures of pavement use, the asphalt is admixed in thin films with a variety of mineral substances. With fillers, it forms binders varying greatly in properties of the original in-bulk asphalt. Additionally, the properties of the original asphalt are changed by heating in the hot paving mixture preparation process. Thus, utility and significance of extensive tests evaluating the properties of the binder at high temperatures, in its original state, are questionable. The measurement of paving mixture properties, rather than the properties of the binder, appears to be a more rational approach. A comparative effect of different type and content of mineral fillers on the laboratory determination of asphalt mixtures mixing and compaction temperatures has been achieved and master curves developed. The experimental results demonstrated that the presence of mineral fillers in asphalt mastic was able to give a positive shift change in the mixing and compaction temperatures compared to those determined from plain asphalt binders. Acknowledgement Special thanks to co-authors and the literature provided in support of this manuscript. 165
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Determination of Mixing and Compaction Temperatures ... - ijcebm

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