MgO膨胀剂在沿海地下工程混凝土裂缝控制中的应用研究

Study on application of magnesium oxide expansion agent in concrete crack control of coastal underground engineering

沿海地区地下水中含有大量的氯离子、硫酸根离子等,含有这些离子的地下水会通过混凝土裂缝渗入到结构内部,对地下工程耐久性构成严重威胁。通过在混凝土中分别掺入活性为120 s和80 s的MgO膨胀剂配制补偿收缩混凝土,同时采取混凝土配合比优化,施工过程、拆模及养护控制等技术来解决混凝土的收缩开裂。结果表明:2种活性的MgO膨胀剂均能有效控制混凝土裂缝。在环境温度较低时,活性为80 s的MgO膨胀剂补偿效果较好,41 d龄期时混凝土内部仍处于微膨胀状态,应变达78με。

Groundwater in coastal areas contains a large amount of chloride ions,sulfate ions,etc.The ground water with these ions will penetrate the concrete cracks into the interior and pose a serious threat to the durability of underground engineering.In this paper,the compensation shrinkage concrete is prepared by blending MgO expansion agent with activity of 120 s and 80 s in concrete respectively.At the same time,control technology of concrete mix ratio optimization,construction process,demoulding and maintenance are used to solve the shrinkage cracking of concrete.The results show that the MgO expansion agents of two activities can compensate the shrinkage of concrete effectively.The compensation effect of 80 s MgO expansion agent is better at lower ambient temperature.The interior of the concrete is still in a micro-expansion state at the age of 41 d,and the strain value reaches 78με.