车桥耦合振动对混凝土早期性能的影响及其损伤机理

Effects of Vehicle-Bridge Coupled Vibration on Early-Age Properties of Concrete and Its Damage Mechanism

在分析车桥耦合振动参数变化规律的基础上,提出了合理的振动模拟试验方法与评价指标,研究了车桥耦合振动参数对不同水胶比混凝土性能的影响,并结合微观结构试验结果,探讨了混凝土损伤机理.研究发现：车桥耦合振动会加速混凝土的泌水,降低实际水胶比,一定程度上有利于其抗压强度测试值的提高,但会提高混凝土内部大于200nm的多害孔比例,同时加剧石子下沉和浆体上浮,使得混凝土早期离析程度增大,均匀性降低,密实度降低,从而降低混凝土长期性能.在混凝土凝结硬化初期（贯入阻力≤0.5MPa）和后期（贯入阻力≥28.0MPa）,车桥耦合振动产生的破坏作用较小;在凝结硬化中期（贯入阻力为0.5～28.0MPa）,车桥耦合振动会导致混凝土内部产生永久微裂纹等缺陷,对混凝土性能影响较大.

The variation law of vehicle-bridge coupled vibration was analyzed and a reasonable method to simulate coupled vibration in lab as well as the evaluation indexes was proposed.Then the effects of vehicle-bridge coupled vibration parameters on the properties of concrete with different water-cement ratio were studied.The damage mechanism of vehicle-bridge coupled vibration on concrete was investigated according to the microstructure results.The results indicate that under vehicle-bridge coupled vibration,the bleeding of concrete accelerates,the actual water-cement ratio reduces,and the compressive strength increases to a certain extent.However,the early segregation of concrete is aggravated by the vibration,which leads to worse uniformity and compactness.The long-term performance of concrete is deteriorated as seen from a higher proportion of deleterious pores（200nm）of concrete.At the early age（i.e.penetration resistance≤0.5MPa）of setting and later age（i.e.penetration resistance≥28.0MPa）of hardening,the negative interference of vehicle-bridge coupled vibration is insignificant,however,vehicle-bridge coupled vibration can lead to a lot of irreversible micro-cracks in concrete at the middle age（i.e.penetration resistance0.5-28.0MPa）,which may have a great influence on concrete performance.