预制构件混凝土塑性开裂特征及防裂措施研究  

Study on the Plastic Cracking Characteristics and Crack Prevention Measures of Precast Concrete

作　　者：张丰[1,2] 祝烨然 白银[1,2] 陈波 吕乐乐[1,2] ZHANG Feng;ZHU Yeran;BAI Yin;CHEN Bo;LYU Lele(Nanjing Hydraulic Research Institute,Nanjing 210029,China;State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering,Nanjing 210029,China;Nanjing R&D High-Tech Co.,Ltd.,Nanjing 210024,China)

机构地区：[1]南京水利科学研究院,南京210029 [2]水文水资源与水利工程科学国家重点实验室,南京210029 [3]南京瑞迪高新技术有限公司,南京210024

出　　处：《材料导报》2023年第S02期235-241,共7页Materials Reports

基　　金：国家重点科学研发计划(2020YFC1511902);国家自然科学基金重点项目(51739008);江苏省自然科学基金项目(BK20201125);南京市交通科技项目(G312NJ-KTYJ7)。

摘　　要：本工作基于混凝土早期毛细孔负压发展规律,分析预制构件混凝土塑性开裂特征,并研究功能材料对混凝土早期抗裂性的影响。结果表明,混凝土表层失水快,负压峰值大,峰值出现时间早;越往混凝土内部深处,毛细孔负压增长越缓慢。预制构件C50混凝土在浇筑后4~10 h发生塑性开裂风险最大,5~25 cm区域内混凝土毛细孔负压梯度在6.6 h左右达最大值3.20 kPa/cm;早期开裂敏感性高、抗裂性差,平板总开裂面积高达310 mm^(2)/m^(2),圆环开裂时间52 h。减缩剂、内养护剂、膨胀剂的掺入均可使混凝土毛细孔负压峰值降低、峰值出现时间延后,减缩剂对降低混凝土毛细孔负压效果最佳;内养护剂、减缩剂对改善早期平板抗裂性效果显著,单位面积总开裂面积降低89%~96%;减缩剂对改善圆环法抗裂性效果更佳。Based on the development law of capillary negative pressure of concrete at early age,this paper analyzed the plastic cracking characteristics of precast concrete,and investigated the influence of functional materials on the early cracking resistance of concrete.The results showed that,the water loss rate of concrete surface is fast,the peak value of negative pressure is large,and the peak value occurs early.The deeper into the concrete,the slower the growth of negative capillary pressure.The risk of plastic cracking of precast C50 concrete of prefabricated component is the highest at 4—10 h after pouring,and the negative pressure gradient of concrete capillary in the 5—25 cm area reaches the maximum value of 3.20 kPa·cm^(-1) at about 6.6 h.The C50 concrete has high cracking sensitivity and poor cracking resistance in the early stage.The total cracking area of slab is 310 mm^(2)·m^(-2),and the cracking time of the ring is 52 h.The incorporation of shrinkage reducing agent,internal curing agent or expansive agent can reduce the peak value of capillary negative pressure of concrete and delay the peak time,among which shrinkage reducing agent has the best effect on reducing the capillary negative pressure of concrete.Internal curing agent or shrinkage reducing agent can significantly improve the crack resistance of early flat plate,and the total cracking area per unit area can be reduced by 89%to 96%.And the shrinkage reducer has a better effect on improving the crack resistance of the ring method.

关 键 词：预制构件 毛细孔负压 塑性开裂 减缩剂 内养护剂 

分 类 号：TV42[水利工程—水工结构工程]