高速铁路无砟道床真空脱水机制砂混凝土抗冻性能

Study on Frost Resistance of Cast⁃in⁃place Bed Slab Manufactured Sand Concrete with Vacuum Dewatering Method

冻融损伤是严寒地区高速铁路无砟道床机制砂混凝土耐久性下降的主要原因,提升无砟道床机制砂混凝土抗冻性对于保障道床板的长期服役性能有重要的意义。采用006、008 MPa的真空度对C40现浇道床机制砂混凝土分别真空脱水1、3、5、10 min,研究真空脱水处理后机制砂混凝土的单面抗冻性,通过真空脱水率、表面回弹值和孔隙结构等方法分析真空脱水处理对机制砂混凝土的影响。结果表明:与未处理的机制砂混凝土相比,真空脱水机制砂混凝土在单面冻融循环12次后单位面积冻融剥落物质量降低258%~955%,单面吸水率降低79%~770%;真空脱水处理降低表层混凝土的实际水胶比,改善表层混凝土的孔隙结构,增加混凝土密实度。以真空度和真空脱水时间作为真空脱水处理指标,建立机制砂混凝土单位面积剥落物质量与真空度、真空脱水时间之间的关系模型。混凝土表层真空脱水技术为严寒地区现浇机制砂混凝土抗冻性能提升提供了技术方案。

Freeze-thaw damage is the main durability degradation mechanism for cast-in-place bed slab manufactured sand concrete of high-speed railway ballastless track in cold regions.Improving the frost resistance of ballastless track bed slab manufactured sand concrete presents great benefits for the long-term service performance of ballastless track sys-tem.In this paper,the manufactured sand concrete of C40 cast-in-place bed slab was dewatered with a vacuum method at a vacuum degree of 006 MPa and 008 MPa for 1,3,5 and 10 minutes,respectively to study the frost resistance of vacuum dewatering treated manufactured sand concrete.The influence of vacuum dewatering treatment on manufactured sand concrete was analyzed through the vacuum dewatering rate,surface rebound value and pore structure of the surface concrete.The results show that compared with untreated concrete,the mass of scaling of treated manufactured sand con-crete is reduced by 258%~955%,with water uptake reduced by 79%~770%.With the effect of vacuum dewatering process,the actual water cement ratio of the surface concrete is decreased with improved pore structure of the surface concrete and the increased compactness.The relationship model between the mass of scaling of concreteand the vacuum degree and time was established,aiming to provide a technical solution for improving the frost resistance of cast-in-place bed slab manufactured sand concrete in severe cold regions.