摘要
在水利水电工程中,混凝土的收缩开裂一直没有得到根本解决。如何有效控制和防止混凝土裂缝的产生,特别是对混凝土薄壁结构物来说尤为关键。掺入减缩剂是从混凝土材料本体上来解决干缩问题,它能有效降低混凝土自身的干缩值,特别适用于有抗裂要求的薄壁混凝土结构。本研究开发的SK-J减缩剂可明显降低混凝土毛细孔中水溶液的表面张力,在强碱条件下稳定存在,与常用减水剂、引气剂具有良好的相容性。SK-J减缩剂试验表明:①掺减缩剂对新拌混凝土无明显影响,混凝土和易性良好,不离析、不泌水,凝结时间正常。②掺入减缩剂对混凝土的抗压强度、劈拉强度、抗弯强度等力学性能影响不大;对极限拉伸和弹性模量影响不大,对抗裂有利。③掺入2.0%减缩剂,可使混凝土28d干缩率降低30%以上,而掺入聚丙烯晴纤维和钢纤维对混凝土长期变形性能无明显改变。④显著减少早期塑性收缩裂缝和早期干燥收缩裂缝的数量,限裂等级为一级。
Shrinkage cracking is common in hydraulic project,and it is especially important to prevent this kind of cracking for the thin-walled hydraulic concrete.Entraining of shrinkage-reducing agent could effectively reduce the shrinkage value of fresh concrete,and is especially suitable for the thin-walled hydraulic structure.In this paper,SK-J shrinkage-reducing agent has been developed,which can reduce the surface tension of the capillary water in concrete,be chemically stable in the alkali environment,and compatible with the normal additives of water-reducing and air entraining.According to the test result,SK-J shrinkage-reducing agent will:①not influence the setting time of fresh concrete,with no segregating and no bleeding;②not impact the mechanical properties,such as compressive strength,splitting strength,bending strength,especially the extreme tensile strain and elastic modulus in favor of crack prevention;③reducing the 28-day shrinkage rate of concrete by more than 30%,rather than the no change of long-term deformation behavior of the concrete entraining fibers of polyacrylonitrile or steel;④obviously reduce the early shrinkage-cracking of concrete,and being on the first level in the crack restriction grade.
作者
高曙光
马锋玲
李秀琳
GAO Shu-guang;MA Feng-ling;LI Xiu-lin(Beijing IWHR-KHL Co.Ltd.,Beijing 100038,China;China Institute of Water Resources and Hydropower Research,Beijing 100038,China)
出处
《水利科技与经济》
2021年第11期110-113,117,共5页
Water Conservancy Science and Technology and Economy
基金
新疆2019-2021年院士工作站合作研究项目新疆水专项(2020.C-004)的支持。
关键词
减缩剂
薄壁结构混凝土
干缩裂缝
聚丙烯晴纤维
钢纤维
shrinkage-reducing agent
thin-walled structural concrete
shrinkage-cracking
polyacrylonitrile fiber
steel fiber
