渠道衬砌混凝土冻融风蚀耐久性能及寿命预测

Durability and life prediction of freeze-thaw-wind erosion of channel lining concrete

为探究内蒙古河套灌区渠道混凝土衬砌在冻融循环与风沙吹蚀不利环境下的耐久性能,采用固体废弃物粉煤灰和硅粉替代部分水泥制备渠道混凝土试样,利用快冻法和气流挟沙法模拟野外服役环境,借助超景深三维显微镜观测风沙吹蚀面破坏形态,运用核磁共振探究孔隙结构变化.结果表明:风沙吹蚀混凝土,表层浆体脱落严重,黄河水及盐离子易进入混凝土内部孔隙中,冻融循环加速冻胀和盐侵,有害孔和多害孔逐渐形成贯通裂缝,质量和动弹性模量损失严重,加速了混凝土的冻融破坏.双掺合料有助于增加表面密实度,提高了内部胶凝性,使渠道混凝土抗冻融和冻融-风蚀耐久性显著提高.基于物质衰变理论,以相对动弹性模量为评价指标建立混凝土冻融-风蚀作用寿命预测模型,计算得出复掺粉煤灰硅粉的F15S4较单掺粉煤灰服役寿命提高1.3倍.研究结果为灌区周边固体废弃硅粉-粉煤灰在渠道混凝土中的推广应用提供了理论基础,为配制适合河套灌区特殊服役环境的渠道衬砌提供了研究基础.

In order to explore the durability of channel lining concrete under adverse environmental conditions of freeze-thaw cycle and wind-sand erosion in Hetao Irrigation District,Inner Mongolia,solid waste fly ash and silica fume were used to replace part of the cement for preparing channel concrete samples.The fast freezing method and air flow sand-carrying method were used to simulate the field service environment,damage pattern of the surface erosion was observed with the help of super depth of field,and the pore structure was studied by nuclear magnetic resonance(NMR).The results show that the erosion of concrete by wind and sand causes serious shedding of the surface slurry,and the Yellow River water and salt ions easily enter the internal pores of the concrete.The freeze-thaw cycle accelerates the frost heaving and salt invasion,and the harmful and multi-hazard pores gradually form through cracks.The mass and dynamic elastic modulus loss are serious,which accelerates the freeze-thaw damage of the concrete.Double admixtures helps to increase the surface density,improves internal gelation,as well as the freeze-thaw resistance and freeze-thaw-wind erosion durability are significantly improved.Based on the material decay theory,the relative dynamic elastic modulus is used as the evaluation index to establish the life prediction model of freeze-thaw-wind erosion of concrete,and the calculated service life of F15S4 mixed with fly ash silica fume is 1.3 times higher than that of single fly ash.It provides a theoretical basis for the popularization and application of solid waste silica fume-fly ash in channel concrete around the irrigation area,and provides some basic research for the preparation of channel lining suitable for the special service environment of the Hetao Irrigation District.