摘要
马鞍山公铁两用长江大桥主航道桥为千米级三塔钢桁梁斜拉桥,边塔高308 m、中塔高345 m,桥塔采用钢-混组合结构,中、下塔柱采用C60混凝土结构,塔柱横截面壁厚1.4~3.0 m。为提高该桥桥塔混凝土抗裂性能,在优选原材料的基础上,提出添加降黏剂的混凝土配合比进行优化比选;优选分别掺加16%减缩型和12%抗裂型降黏剂的混凝土配合比进行1.4 m(未设冷却水)和3.0 m(设置冷却水)壁厚塔柱的足尺模型试验。结果表明:降黏剂的掺入可显著降低混凝土的塑性粘度和开裂温度,提升混凝土的应力储备,延缓混凝土到达温峰的时间,提高混凝土的抗裂性能;足尺模型混凝土表面外观质量均良好、均未出现有害裂纹。由于掺加16%减缩型降黏剂配合比混凝土的性价比更优,因此该桥Z3号、Z4号桥塔最终采用该配合比方案,提高了混凝土外观质量及抗裂性能,拆模后的塔柱混凝土表面平整光滑、色泽一致,无有害裂纹。
The main navigation channel bridge of Maanshan Changjiang River Rail-cum-Road Bridge is a three-pylon steel truss girder cable-stayed bridge with two main spans over 1000 m long.All the three pylons are steel-concrete composite structures,the two side pylons rise 308 m,and the central pylon measures 345 m.The intermediate and lower pylon columns are made of C60 concrete,with wall thickness between 1.4 and 3.0 m.The materials for pylons had been selected in accordance with strict norms,however to obtain improved cracking resistance of pylon concrete,viscosity reducing agent was introduced to modify the mix proportion of concrete.The characteristics of concrete mixes with and without viscosity reducing agent were compared and analyzed.Full-scale models of the pylon columns with wall thicknesses of 1.4 m(with water cooling pipes)and 3.0 m(without water cooling pipes),respectively,were prepared to investigate the cracking resistances of the concrete mix added with 16%shrinkage-reduction type viscosity reducing agent and the concrete mix added with 12%anti-crack type viscosity reducing agent.As per the analysis,adding viscosity reducing agent can significantly decrease the plastic viscosity of concrete,reduce the cracking temperature,improve the stress reservation of concrete and delay the arrival of peak temperature of concrete,as a result,the cracking resistance of the concrete has been improved.The pylon columns have smooth surfaces and no harmful cracks occur.Compared with the concrete mix with 12%anti-crack type viscosity reducing agent,the concrete mix added with 16%shrinkage-reduction type viscosity reducing agent is considered better in terms of cracking resistant performance and economy.The piers Z3 and Z4 are cast with the concrete with 16%shrinkage-reduction type viscosity reducing agent to achieve better visual appearance and cracking resistance.When the formwork was removed,the surfaces of the concrete pylon columns were visually appealing,with good color consistency and no hazardous cracks.
作者
龙勇
刘爱林
董继红
黄斌
盖珂瑜
LONG Yong;LIU Ai-lin;DONG Ji-hong;HUANG Bin;GE Ke-yu(China Railway Bridge Science Research Institute,Ltd.,Wuhan 430034,China;National Key Laboratory of Bridge Intelligent and Green Construction,Wuhan 430034,China;China Railway Major Bridge Engineering Group Co.,Ltd.,Wuhan 430050,China)
出处
《桥梁建设》
EI
CSCD
北大核心
2023年第3期8-15,共8页
Bridge Construction
基金
中铁大桥局集团有限公司科学技术研究与开发项目(GS.2022-02-重点)。
关键词
公路铁路两用桥
斜拉桥
桥塔
混凝土
抗裂技术
降黏剂
配合比
足尺模型试验
rail-cum-road bridge
cable-stayed bridge
pylon
cracking resistant technique
concrete
viscosity reducing agent
mix proportion
full-scale model test
