盐冻融条件下热再生混合料水稳定性及细观特性研究

Research on Impact of Salt Freeze-thaw Cycles on the Moisture Performance and Microstructure of Hot Recycle Mixture

对热再生混合料进行不同浓度盐溶液10次冻融循环试验,并采用4%盐溶液进行重复冻融循环试验,分析溶液浓度及冻融次数对热再生混合料空隙率和TSR(冻融劈裂强度比)的影响;同时,采用CT扫描手段分析冻融循环作用对混合料内部孔隙分布的影响。结果表明:经过10次盐冻融循环后,0、2%、4%及6%浓度盐溶液条件下空隙率增加程度分别为2.9%、7.5%、13.0%和12.6%;冻融7次以后空隙率增大幅度明显变大,其TSR不断下降,这说明随着冻融循环次数的继续增加混合料内部沥青与集料的黏结作用受到破坏;固液交替产生的膨胀应力、温度应力及盐溶液对集料-沥青界面的共同破坏作用导致混合料内部孔隙发生变化,体积在0~20mm3范围内孔隙数目明显减少,而体积在20~40mm^3范围内的空隙明显增加。

Ten times salt freeze-thaw cycling tests are carried out on hot recycled mixture with different concentration of salt solution,and repeated salt freeze-thaw cycling test with 4%salt solution is also conducted to analyze the impact of solution and the number of salt freezing and thawing on hot recycled mixture void fraction and TSR;at the same time,CT scanning is used to analyze the void distribution during salt freeze-thaw cycling.Test results show that after 10salt freeze-thaw cycles,under 0,2%,4%and 6%concentration of salt solution freezing and thawing,the air void increases by 2.9%,7.5%,13.0%,and 12.6%;after seven freezing and thawing cycles,the air void obviously increases,but the TSR decreases,which indicates that as freeze-thaw cycle of continued the adhesive in asphalt mixture and aggregate is damaged;air void changes due to the expansion,temperature stress,and damage of the salt solution to asphalt aggregate interface:numbers of the air volume within 0~20 mm3 decrease significantly,while the volume within 20to 40mm3 increases significantly.