三种减缩措施对隧道混凝土变形控制的影响比较

通过开展混凝土干缩试验,对采用聚羧酸系高效减水剂、膨胀剂及内养护技术的混凝土干缩体积稳定性进行研究,分析不同减缩措施对隧道混凝土变形控制的影响.结果表明,与膨胀剂相比,聚羧酸系高效减水剂不会增加混凝土干缩,在后期有一定程度的改善作用,而且对施工阶段的保湿养护要求不太苛刻,在隧道火灾条件下水化产物也具有更好的稳定性.实际隧道工程中,率先采用聚羧酸系高效减水剂代替AFt类膨胀剂用于地下工程结构,应用实践表明是合理可行的,对混凝土结构耐久性能有利.

Comparison on the Effect of Three Shrinkage Reducing Measures to Ttmnel Concrete Deformation

Volume stability induced by drying shrinkage of concrete used in Xuanwu Lake Tunnel was studied through measuring the drying shrinkage of concrete,in which admixtures and presoaked LWA such as polycarboxylate-type superplasticizer(PS),ettringite type expansion agent(AEA),magnesia type expansion agent,perlite and ceramsite were used.The results reveal that using PS does not degrade the drying shrinkage of concrete compared with expansion agent,and improvement occurs to some extent in the long term.In addition,rigorous curing is not needed in construction stage,and it performs excellent volume stability in case of fire in tunnel.Concrete is prepared with PS but no expansion agents in construction of main structure which exhibits good performance since constructed.In a conclusion,it is desirable to replace AEA with PS in the tunnel engineering practice,which will benefit the durability of the concrete structure.