沥青混合料的变速拌和功率测试与拌和流变模型

Mixing power measurement at different mixing velocities and mixing rheological model of bituminous mixture

为了定量评价沥青混合料的和易性与深化认识其强度构成的演变机理,基于沥青混合料的常规拌和设备,自行开发了一种变速拌和功率测试装置V-P-Mixer,进行了沥青混合料的拌和流变特性试验。针对不同沥青用量(0~8%)的AC-13C型沥青混合料,在不同拌和温度(130℃~170℃)和不同拌和速率(20~50r·min^(-1))下进行了拌和功率测试,绘制了功率-速率流变图,建立了黏塑性拌和流变模型,并以拌和黏度的倒数定义了和易性指数。分析结果表明:拌和消耗的电流、电压和有功功率的波动误差分别为2.25%、0.11%和5%,重复再现误差为0.25%,测试数据稳定、可靠,可用来表征沥青混合料的拌和功率;拌和流变模型服从线性的Bingham黏塑性模型,流变直线的斜率可以表征沥青混合料的拌和黏度,定义斜率的倒数为和易性指数;拌和温度每升高10℃可降低拌和黏度和提高和易性指数10%~20%;沥青用量的增加会增大拌和的黏度和阻力,每增加1%降低和易性指数5%~25%;从强度构成的演变机理来看,碎石决定了内在塑性极限,沥青决定了黏性强度。

In order to quantitatively evaluate the mixing workability and to deeply know the evolution mechanism of the strength of bituminous mixture, an experimental device of mixing power measurement at different velocities named V-P-Mixer was developed in laboratory based on the conventional mixing devices, and an experiment was carried out for the mixing rheological behavior of bituminous mixture. Based on AC-13C bituminous mixtures with different bitumen contents （0-8%）, the mixing powers were measured at different mixing temperatures （130 ℃- 170 ℃） and mixing velocities （20-50 r · min^-1）, the power-velocity diagrams were analyzed, a visco-plastic mixing rheological model was presented, and the workability index was defined as the reciprocal of mixing viscosity. Analysis result shows that the alternating errors of electric current, voltage and power consumed during mixing are respectively 2.25%, 0. 11% and 5%, and the repeatability error is 0. 25 %, so the measurement is stable and reliable to characterize the mixing power of bituminous mixture; the mixing rheological property obeys the linear Bingham model, in which the straight slope represents the general viscosity of bituminous mixture, and the reciprocal of the viscosity is defined as the workability index; when the temperature increases by 10 ℃, the mixture＇s viscosity decreases and the workability index increases by 10%-20%, so it is easier to mix; the mixing power and resistance increase with the increase of bitumen content, and the workability index decreases by 5%,-25%, when the bitumen content increases by 1%,; aggregate plays plastic role, and bitumen plays viscous role in the strength mechanism of bituminous mixture. 6 tabs, 9 figs, 22 refs.