摘要
为解决咬合桩施工现场超缓凝混凝土的制备问题,探究缓凝剂的作用机理,采用白糖和葡萄糖酸钠按质量比7∶3配制复合缓凝剂,对比一次搅拌和二次搅拌工艺,制备超缓凝混凝土。采用抗压抗折一体化试验机、环境扫描电子显微镜(ESEM)、总有机碳分析仪和等温量热仪测试分析超缓凝混凝土的力学性能、微观形貌、吸附量和水化性能。结果表明,混凝土的凝结时间随着缓凝剂掺量的增加而延长。当缓凝剂掺量为0.38%(质量分数)时,一次搅拌组初、终凝时间分别为31 h和46 h,二次搅拌组初、终凝时间分别为34 h和50 h;当缓凝剂掺量为0.50%(质量分数)时,一次搅拌组初、终凝时间分别为61 h和78 h,二次搅拌组初、终凝时间分别为65 h和84 h。两种掺量下,混凝土56 d抗压强度均达到40 MPa以上,满足两种工况的施工要求。采用二次搅拌工艺制备超缓凝混凝土有助于进一步延长混凝土的凝结时间,改善混凝土拌合物的流动性,但会略微降低混凝土的抗压强度。不同缓凝剂在水泥颗粒表面的吸附能力强弱顺序为:葡萄糖酸钠>白糖-葡萄糖酸钠>白糖>白糖-葡萄糖酸钠后掺。缓凝剂的掺入起到降低水化放热,抑制水泥水化的作用,从而延长混凝土的凝结时间。
In order to solve the preparation problem of super-retarding concrete at the construction site of bite pile and explore the mechanism of retarder, the super-retarding concrete was prepared by adding sugar and sodium gluconate with a mass ratio of 7 ∶3 as composite retarder, and two kinds of preparing process, namely the primary stirring process and secondary stirring process were compared. The mechanical properties, microstructure, adsorption amount and hydration properties of super-retarding concrete were tested and analyzed by compressive and flexural testing machine, environmental scanning electron microscope(ESEM), total organic carbon analyzer and isothermal calorimeter. The results show that the setting time of concrete increases with the increase of retarder content. When the content of retarder is 0.38%(mass fraction), the initial and final setting time of the first stirring group are 31 h and 46 h, respectively, and the initial and final setting time of the second stirring group are 34 h and 50 h, respectively. When the content of retarder is 0.50%(mass fraction), the initial and final setting time of the first stirring group are 61 h and 78 h, respectively, and the initial and final setting time of the second stirring group are 65 h and 84 h, respectively. Under the two dosages, the 56 d compressive strength of concrete is all above 40 MPa, which can meet the construction requirements of the two working conditions. The secondary stiring process is helpful to further prolong the setting time of concrete and improve the fluidity of concrete mixture, but slightly reduce the compressive strength of concrete. The order of adsorption capacity of different retarders on the surface of cement particles is: sodium gluconate>sugar-sodium gluconate>sugar>sugar-sodium gluconate after blending. Mixing retarder can reduce hydration heat and restrain hydration of cement, so as to prolong setting time of concrete.
作者
刘世成
曹开伟
徐升才
王信刚
王睿
朱街禄
LIU Shicheng;CAO Kaiwei;XU Shengcai;WANG Xingang;WANG Rui;ZHU Jielu(School of Infrastucture Engineering,Nanchang University,Nanchang 330031,China;Jiangxi Zhongheng Underground Interspace Science Co.,Ltd.,Nanchang 330052,China;Architecture&Design College,Nanchang University,Nanchang 330031,China)
出处
《硅酸盐通报》
CAS
北大核心
2022年第12期4214-4224,共11页
Bulletin of the Chinese Ceramic Society
基金
国家自然科学基金(52062032)
江西省自然科学基金重点项目(20212ACB204017)。
关键词
超缓凝混凝土
复合缓凝剂
咬合桩
二次搅拌
吸附量
水化热
super-retarding concrete
composite retarder
bite pile
secondary stirring
adsorption amount
hydration heat
