堆石坝混凝土抗裂技术研究

Mix proportion design of crack-resistant concrete for face rockfill dam

根据积石峡面板堆石坝混凝土的技术要求,在满足工作性、力学性能的基础上,从粉煤灰掺量、功能性外加剂(萘系、聚羧酸类)角度优化了混凝土配合比;在此基础上,采用不同煅烧温度的氧化镁类膨胀剂与减缩剂进行复合,大幅降低了混凝土的干燥收缩,72 d时混凝土的干燥收缩值为222×10-6,仅为基准配合比干燥收缩值的53.8%;采用圆环法研究了砂浆的开裂敏感性,对于砂浆开裂敏感性的降低幅度J,M-SRA>JM-PCA>FA,粉煤灰掺量为25%J,M-PCA、M2J、M-SRA复掺的砂浆放入恒温恒湿室39 d后才出现裂缝,较基准配合比延长了28 d。

According to the requirement of Ji Shi-xia face rockfill dam concrete,basing on meeting workability and mechanical properties,the mix proportion has been optimized with content of fly ash、functional super plasticizers（naphthalene series,polymer carboxylic series）,the appearance of the peak of hydration heat has been postponed,the peak value of hydration heat has been reduced;On the basis of this,MgO expansive agent burned under different temperature and shrinkage reducing agent have been compounded,the drying shrinkage significantly reduced,after 72 d the drying shrinkage value is 222×10-6,only 53.8% of the standard mix proportion;the cracking sensitivity of mortar has been studied through ring test,the rank of effect for reducing cracking sensitivity is JM-SRAJM-PCAFA,the mortar compounding fly ash,JM-PCA,M2,JM-SRA cracks after 39 d,28 d later than standard mix proportion.