氧化镁膨胀剂对船闸施工期混凝土开裂风险的影响

针对船闸大体积、异型结构混凝土的施工期开裂问题,依托九圩港二线船闸工程,模拟评估氧化镁膨胀剂及外保温措施对结构混凝土温度场、应力场和开裂风险的影响,并通过对实体结构温度、变形的监测,评估实际工程应用效果。结果表明,在混凝土中掺加氧化镁膨胀剂是降低船闸结构混凝土施工期收缩开裂的有效措施之一,在冬季较低的浇筑温度下,掺加氧化镁膨胀剂并配合一定保温措施,可同时降低混凝土结构表面和中心的开裂风险。氧化镁膨胀剂的掺入基本不会影响船闸混凝土的温度历程,但能够降低闸室边墙结构混凝土温降阶段的收缩50×10~(-6)~70×10(-6),降低闸首廊道结构混凝土温降阶段收缩40×10~(-6)以上,显著提升船闸混凝土施工期抗裂性。

Effect of MgO expansive agent on cracking risk of ship lock concreteduring construction period

Aiming at the cracking problem of large volume and irregular structure concrete during ship lock construction period,relying on the Jiuweigang Second-line Ship Lock engineering,we simulate the effects of MgO expansive agent and insulation measure on the temperature field,stress field and the cracking risk of sidewall concrete in lock chamber,and monitor the temperature and deformation histories of the actual structure concrete.The results show that the addition of MgO expansive agent is one of the effective measures to reduce the shrinkage and crack risk of ship lock concrete during the construction period,when proper insulation measure is taken at the same time,the crack risk of the surface and the center concrete casted in winter can be reduced simultaneously.The addition of MgO expansive agent almost has no effect on the temperature history of ship lock concrete,while it can reduce the shrinkage of 50×10-6~70×10-6 for the actual sidewall concrete in lock chamber and reduce the shrinkage over 40×10-6 for the actual sidewall concrete in lock head corridor.