细粒式沥青混合料断裂愈合预估模型

Prediction Model of Fracture-healing of Fine-grained Asphalt Mixture

为分析沥青混合料断裂愈合预估模型,采用70#基质沥青和SBS改性沥青制备AC-13混合料半圆试件,通过半圆弯曲试验获得荷载-位移曲线,将断裂的半圆试件拼接后放入烘箱中养护,并对养护后的试件进行二次加载。采用愈合后和愈合前两次加载的临界荷载比作为愈合指数(Healing index,H_(I)),并用其评价混合料的断裂愈合性能。根据毛细流动原理,建立沥青混合料愈合预估模型,并根据试验结果验证该模型的适用性,根据H_(I)建立愈合时间和愈合温度的转换关系。结果表明:发生开裂的沥青混合料试件在特定的环境中养护后具备二次承载的能力,虽然H_(I)<1.0,但试件在100℃&12 h环境中愈合后,H_(I)可达到0.7,即愈合后抗拉强度恢复了70%;愈合时间从4~8 h延长至8~12 h时,100℃环境中70#AC-13混合料的H_(I)增长速率分别为0.096/h和0.023/h,SBS AC-13混合料的H_(I)增长速率分别为0.096/h和0.009/h,说明H_(I)随愈合时间的延长而增加,但增长速率先增后减;采用函数H_(I)(t)=(-1+e^(-Ct))^(2)(C>0)能较好地拟合不同愈合温度下愈合指数随愈合时间的变化,拟合系数R~2>0.90;根据H_(I)值建立愈合温度和愈合时间的转换模型t(T)=C_(3)·e^(C_4/T)(00.95)。

In order to study the prediction model of fracture-healing property of asphalt mixture,in this paper,70#matrix asphalt and SBS modified asphalt were used to make AC-13 mixture semi-circular specimen.The load-displacement curves were obtained through the semi-circular bending test(SCB),and the cracked semi-circular specimen was spliced and placed in an oven for healing.The secondary loading was applied to the healed specimen.The peak load ratio after and before healing was used as the healing index(H_(I))to evaluate the fracture-healing property of the mixture.According to the capillary flow principle,the prediction model of asphalt mixture healing was established,and it was used to fit the test results.The conversion equation between healing time and temperature during H_(I)fixation was established by fitting equation.The results show that the fractured asphalt mixture has the secondary bearing capacity after healing in a specific environment.Although the H_(I)value is less than 1.0,it can reach 0.7 in the healing condition of 100℃&12 h,That is,the tensile strength recovers by 70%after healing;When the healing time is from 4 h to 8 h and 8 h to 12 h,the H_(I)growth rate of 70#AC-13 asphalt mixture in 100℃are 0.096/h and 0.023/h,respectively.The H_(I)growth rate of SBS AC-13 asphalt mixture are 0.096/h and 0.009/h,respectively,it shows that H_(I)increases with the increase of healing time,but the growth rate increases first and then decreases.A function H_(I)(t)=(-1+e^(-Ct))_(2)(C>0)can be used to fit the change of healing index with healing time at different healing temperatures,and the fitting coefficient is R 2>0.90.Based on the principle of time-temperature equivalence,a transition model t(T)=C_(3)·e C_(4)/T(0<C_(3)<1,0<C_(4),R 2>0.95)between healing temperature and healing time is established.