温度对水泥乳化沥青砂浆层与混凝土层间界面黏结影响

Influence of Temperature on Interfacial Bonding between Cement Emulsified Asphalt Mortar Layer and Concrete Layer

采用高低温循环模拟试验,研究温度对板式轨道砂浆充填层与混凝土底座板层间界面黏结的影响.分别用沥灰比（A/C）为0.3、0.5、0.7、0.9的水泥乳化沥青砂浆和C40混凝土,制备不同砂浆层与相同混凝土层2层黏结的复合试件,置于变温范围为-20℃～60℃试验箱内,在设定的高低温循环变化制度下,用表面粘贴应变片法测试复合试件中各层和界面的变形规律,并用Z字型夹具测试经一定温度循环后复合试件的界面剪切强度.结果表明：在温度升降过程中,水泥乳化沥青砂浆层的热变形行为不同于混凝土,砂浆层的热变形值大于混凝土层的热变形值,且随沥灰比增加而增大;砂浆层的热变形速率有温度和时间依赖性;复合试件中混凝土层对砂浆层的热变形具有较大约束作用,导致复合试件界面处产生温度应力;在高低温循环变化条件下,温度应力引起砂浆层出现表面开裂,并导致界面剪切强度不断下降,最终引起层间离缝和界面完全脱黏.由此证明了环境温度变化和砂浆与混凝土的热行为差异是板式无砟轨道结构服役中出现砂浆充填层开裂和层间离缝等劣化现象的2个重要原因.

High-low temperature cycling simulation tests were made to investigate the temperature effect on in- terracial bonding between the cement emulsified asphalt mortar layer and concrete layer. Composite specimens of two bonded layers were prepared, in which one layer was invariable C40 concrete and another layer was vari- able cement emulsified asphalt mortar（SL mortar） made of different asphalt-cement （A/C） ratios of 0.3, 0.5, 0.7, 0.9. These specimens were laid into the testing chamber with the temperature cycling range of -20 ℃ ~60 ℃. Under the setting high-low temperature cycling system, expansive and shrink strains of composite speci- mens were measured with surface strain gages, and after some time of temperature cycling, the shear strength of the interface between the concrete substrate and SL mortar layer was measured with the self-made Z-type shear fixture. Testing results show as follow.. The thermal deformation behavior of the SL mortar layer is dif- ferent from that of the concrete layer; the expansive and shrink strains of the former are larger than that of the latter and increase with increasing of the A/C ratio;the strain rate of the former is obviously dependent on temperature changes and time;constraints of the concrete layer on the thermal deformation of the SL mortar layer produce considerable temperature stress in the interfaces; temperature stress generated due to changing temperaturecycles will result in cracking in the SL mortar layer, cause the interfacial shear strength to fall continuously and finally lead to interface separating and complete unsticking. The appearance of opening gaps between layers and cracking of the SL mortar layer of in-service slab track structures can be explained as the result of changes of ambient temperatures and notable differences of the thermal deformation behavior of mortar and concrete.