养生方法对泡沫沥青冷再生混合料性能的影响

Effect of Curing Procedure to Foamed Asphalt Cold Recycled Mixture Properties

为了更真实模拟现场养生状况,设计开放养生、半密封养生及半密封+全密封养生("组合"养生)3种养生方式,并采用力学试验对3种养生条件下泡沫沥青冷再生混合料的含水率、劈裂强度(indirect tensile strength,ITS)、无侧限抗压强度(unconfined compressive strength,UCS)及抗剪参数的发展规律进行研究;同时,通过CT扫描试验对混合料内部空隙结构进行分析.结果表明:不同养生方式下,混合料内部水分迁移路径和散失速率不一致,导致混合料养生过程中含水率及强度发展规律不一致;含水率与混合料终期养生强度密切相关;不同养生条件下混合料的内摩擦角变化规律基本一致,而黏聚力受含水率影响明显;半密封及"组合"养生水分散失速率慢,养生过程中被水化产物包裹的水分产生的水蒸气压力会破坏原有空隙结构,从而揭示了不同养生方式的空隙分布机理并推荐半密封养生36 h+全密封养生36 h作为泡沫沥青冷再生混合料中长期养生方法.

In order to simulate field curing condition, uncovered curing,semi-covered curing and semicovered+ covered curing ( “ combination冶 curing) of three methods were designed. Mechanics tests were used to study development law of moisture content, indirect tensile strength ( ITS) , unconfined compressive strength ( UCS) and the shear parameters. At the same time, the internal void structure of mixture was analyzed by CT scanning test. Results show that the difference of the strength development law results in the difference of moisture migration path and loss rate at three curing conditions. Moisture content is closely correlative with mixture strength, and the change law of internal friction angle of mixture seemes similar and the cohesive force is significantly influenced by the moisture content. The void structure which was formed by hydration products is destroyed by water vapor pressure due to the slow evaporation rate of semi-covered curing and “ combination 冶 curing procedure. Therefore, the strength presents lower than that of uncovered curing. According to the research of mechanical properties and voids distribution,semi-covered curing 36 h + covered curing 36 h is recommended as a long term curing procedure in foamed asphalt cold recycled mixture design.