基于XCT的C60高性能混凝土高温细观结构损伤研究

Meso structure Damage of C60 High Performance Concrete atHigh Temperature Based on X CT

摘要:

采用X射线计算机断层扫描（XCT）技术，对20~600℃下C60高性能混凝土（HPC）和掺0.2%聚丙烯纤维C60高性能混凝土（PPHPC）的细观结构进行试验研究，旨在分析高温及聚丙烯纤维对高性能混凝土内部细观结构损伤及劣化衍化的影响，揭示高性能混凝土高温爆裂及聚丙烯纤维改善其高温性能的机理.结果表明：随着温度的升高，混凝土的孔隙率、平均孔径不断增加，裂缝长度、宽度、面积及周长均有所发展，内部细观结构不断劣化，抗压强度随之降低；400℃高温作用后，PPHPC内部孔隙数量较HPC有所增加；XCT图像直观表明PPHPC劣化滞后于HPC，PPHPC孔隙增长率及抗压强度损失率均较HPC低；受火温度与缺陷率是影响混凝土强度的主要因素，掺聚丙烯纤维可以改善HPC的高温性能.

Abstract:

The meso structure of C60 high performance concrete mixed with no fiber(HPC) and 0.2% polypropylene fiber(PPHPC) at 20600℃ was studied by X ray computed tomography(X CT). The effects of high temperature and polypropylene fiber on the damage and deterioration of HPC were investigated. The mechanism of high temperature bursting and the improvement of high temperature properties by mixing polypropylene fibers were revealed. Results show that with the increasing temperature, the porosity and average pore size increase; the cracks also develop in length, width, area and perimeter; the meso structure of concrete deteriorates and the compressive strength decreases. The number of pore in PPHPC is more than that in HPC at 400℃. CT images show that PPHPC deteriorates lag behind HPC. The pore growth and compressive strength loss rate of PPHPC are both lower than that of HPC. Fire temperatures and defect rate are the main factors affecting the strength of the concrete, and polypropylene fiber improves the high temperature performance of HPC.