双螺杆挤出胶粉改性沥青流变性能研究

为解决橡胶沥青黏度高、掺量低的问题,用双螺杆挤出法对胶粉进行脱硫,同时为了进一步解决螺杆高温挤出时胶粉力学性能损失大的问题,采用双螺杆分别在低温(低于170℃)120℃、160℃和高温200℃、240℃挤出胶粉,再分别以20%、30%、40%的胶粉掺量(质量分数)制备12组胶粉改性沥青。通过溶胶含量试验,测试胶粉的脱硫程度;采用布氏黏度试验、动态剪切流变试验(DSR)、多应力蠕变恢复试验(MSCR),研究挤出温度、胶粉掺量对胶粉改性沥青加工流动性能、流变性能的影响规律。结果表明:采用活化工艺结合双螺杆挤出工艺制备的胶粉溶胶含量有较大提高,160℃挤出温度下溶胶含量较120℃挤出温度下溶胶含量提高了2.13%;黏温曲线中,活化挤出胶粉改性沥青相比橡胶沥青黏度降低较为明显,说明活化挤出工艺能很好地改善橡胶沥青黏度高的问题;随着挤出温度的升高,胶粉改性沥青复数剪切模量逐渐降低,同时在低频区相位角不断增大,意味着弹性性能逐步减弱;挤出温度为120℃和160℃时,胶粉掺量的增加能改善沥青高温性能和弹性恢复性能,但温度升至200℃及240℃时,高温性能随掺量增加有所降低,240℃时弹性恢复性能也开始降低;12组样品中160℃挤出温度条件下,各掺量胶粉改性沥青流变性能较好,加工流动性能也相比橡胶沥青有较大改善。

Rheological Properties of Crumb Rubber-modified Asphalt Prepared by Twin-screw Extrusion

Twin-screw extrusion was used to desulfurize rubber powder in order to solve the problem of high viscosity and low content of rubberized asphalt. Meanwhile, in order to further address the mechanical property loss of rubber powder that occurs when screw extrusion is conducted at high temperatures, in this study, a twin-screw extruder was used to extrude the rubber powder at low temperatures (i.e., temperatures below 170℃) of 120℃ and 160℃ and high temperatures of 200℃ and 240℃. Twelve groups of rubber-modified asphalt were prepared using 20%, 30%, and 40% of rubber powder. The desulfurization degree of rubber powder was tested by measuring the "sol" content. The influence of extrusion temperature and dosage of rubber powder on the flow and rheological properties of the modified asphalt was studied by the Brookfield viscosity test, dynamic shear rheometer, and multi-stress creep recovery test. The results show that the content of rubber powder sol significantly increases by using activation technology combined with twin-screw extrusion. The content of sol at an extrusion temperature of 160℃ is 2.13% higher than that at an extrusion temperature of 120℃. From the viscosity-temperature curve, it can be seen that the viscosity of activated-extruded rubber-modified asphalt decreases more evidently than that of rubberized asphalt; this shows that the high viscosity of rubberized asphalt can be improved by the activated extrusion process. With an increase in the extrusion temperature, the multi-shear modulus of the modified asphalt gradually decreases and the phase angle of the low-frequency region increases; this indicates that the elastic properties of asphalt are gradually weakened. When the extrusion temperature is 120℃ or 160℃, the addition of rubber powder can improve the high-temperature performance and resilience of asphalt. However, when the temperature is increased to 200℃ and 240℃, the high-temperature performance decreases with an increase in dosage; additionally, the elastic recovery performance begins to decrease at 240℃. In the 12 groups of samples, the rheological properties of rubber-modified asphalt improve with increasing rubber content at an extrusion temperature of 160℃, and the flow performance of modified asphalt is more satisfactory than that of rubberized asphalt.