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The aim of this study was to improve an effective approach to the processing of asphalt binder modified with micro-silica particles. Various mixer type (mechanical and high shear), revaluation rates (2000, 4000 and 6000 rpm), and two mixing time (30 and 60 minutes), were adopted. Three micro-silica contents 2%, 4%, and 6% by weight of asphalt cement were added. The asphalt binder was prepared at temperature of 140 °C. Comparisons were made to evaluate the properties of the modified asphalt binder such as penetration grade, softening point temperature, temperature sensitivity, rotational viscosity and ductility. Results of this study showed that the use of micro silica as a modifier was helpful in enhancing the physicals properties of the asphalt binder. In general, it was found that the penetration value decreased and softening point temperature, as well as the viscosity value, increased and the temperature sensitivity was improved. Furthermore, high shear mixing was more practical particularly to achieve a good dispersion of micro silica particles into asphalt binder and obtained a homogenous composite binder. Finally, the tested specimens showed 6% of micro silica was adequate to improve the physical properties of asphalt and become more suitable for constructing the highway pavements in hot weather conditions.

This research study examines the practicability of using micro and nano size silica to improve the asphalt characteristics. Asphalt cement penetration grade of (60 /70) was prepared using (0%, 2%, 4% and 6%) of silica filler by weight of asphalt and investigated in terms of the softening point, penetration, and penetration index, viscosity, and ductility values. To modify the asphalt binder, the silica powder was mixed by a mechanical blender set at (2000) rpm at a mixing temperature of 140°C. However, the main challenge is an agglomeration of nano-silica powder which can reduce the ductility of nano silica modified binder. Therefore, this paper studies the efficiency of mixing period to obtain a homogeneous composite binder while alleviating the agglomeration issue. To do so, the effect of periods of mixing ranged between (30 to 60) minutes were examined on characteristics of modified asphalt binders. Overall, the addition of silica filler has an encouraging impact on the asphalt binder rheological properties. Also, the ductility value decreases with the addition of nano-silica content, attributed to the huge surface area and degree of agglomeration.  Furthermore, results exhibited that 6% of micro silica powder and 4 % of nano silica powder were reasonable to develop the rheological properties.

In past, the use of by-product materials such as cement kiln dust and fly ash powders, especially in the field of highway pavements has received increasing attention. The aim of this research is to investigate the physical properties of the modified asphalt binder with additives of filler types such as cement kiln dust, fly ash, and metakaolin powder. Then, to assess the Marshall properties of modified asphalt mixtures. Three fillers containing 3%, 5%, and 7% by weight were used. The modified asphalt binder was mixed by a mechanical mixer having a revolution rate of (2000 rpm.), for mixing time (5 to 20) min. at a temperature of 140 °C. Results showed that the use the additives was beneficial in improving the physical characteristics of the asphalt cement. Overall, it was found that the penetration grade reduced and softening point values increased and the susceptibility of temperature was enhanced. Furthermore, the results of the tested specimens, the 5% of CKD, 5% of fly ash and 7% of MK were sufficient to improve the physical characteristics and Marshall properties of modified asphalt binder mixtures. In addition, the results obtained from the Marshall test show that the maximum stability for 7% of MK, 5% of CKD, 5% of fly ash, and control asphalt mixtures are (14.4, 13.6, 11.7 and 10.4) kN, respectively.

In Iraq pavements materials are exposed to various distresses due to the adverse environmental conditions and heavy traffic. The improvement of performance of flexible pavements is necessary for decreasing these distresses. The objective of this research is to improve the mixing efficiency of nano-silica particles with asphalt binder. Two mixer type (mechanical and high shear), rotational speeds (2000, 4000 and 6000 rpm), and mixing period (30 and 60 minutes) were assessed. Three nano-silica per cent 2%, 4%, and 6% by weight of asphalt were added and the asphalt binder mixtures were prepared by heating at mixing temperature 140 °C. Furthermore, comparisons were made to assess the modified asphalt binder characteristics such as penetration value, softening point, temperature sensitivity (penetration index), ductility and rotational viscosity. Results showed that the use of nano silica as an additive was useful in improving the asphalt binder characteristics. Generally, has been found that the penetration value decreased and softening point increased, as well as the viscosity, were increased and the temperature sensitivity was developed. Additionally, high shear mixing was more useful especially to obtain a good dispersion of nano silica powder in asphalt binder and got a homogenous composite material.