MgO膨胀剂对长龄期混凝土性能的影响

Effect of MgO Expansive Agent on Properties of Long-Age Concrete

关键词:  MgO膨胀剂  混凝土  长期膨胀变形  微结构分析

Key words:  MgO expansive agent  concrete  long-term expansion deformation  microstructure analysis

摘要:

在模拟实际工程变温条件下，对掺MgO膨胀剂混凝土的长期变形性能及微观形貌进行了跟踪监测，并表征了其在80 ℃高温养护下的变形性能.结果表明：在经历早期变温历程及后期常温养护条件下，MgO膨胀剂在混凝土中的补偿收缩性能随着MgO掺量的增加而增大，活性值高的MgO对混凝土的补偿收缩效能更为显著；当常温养护3.0 a时，掺MgO膨胀剂混凝土的变形基本稳定；在80 ℃高温密封养护条件下，3.5 a龄期以上的掺MgO膨胀剂混凝土相较基准混凝土未出现膨胀现象，甚至略有收缩；随着养护龄期的延长，混凝土中MgO颗粒与周围水泥浆体间的分界面呈现逐步融合的特征，MgO颗粒内部O、Mg原子比呈现逐渐上升的趋势.

Abstract:

The long-term deformation performance and microscopic morphology of concrete mixed with MgO expansive agent were monitored under simulated variable temperature conditions of actual engineer， and their deformation performance under high temperature of 80 ℃ was characterized. The results show that the compensatory shrinkage performance of MgO expansive agent in concrete increase with the increase of MgO dosing under the early variable temperature course and later ambient temperature curing conditions. The compensatory shrinkage performance of concrete with high activity value MgO is more significant. When curing at ambient temperature of 3.0 years， compared with the base concrete， the deformation of concrete mixed with MgO expansive agent is basically stable. Under the high temperature condition of 80 ℃， concrete mixed with MgO expansive agent above the age of 3.5 years does not show expansion phenomenon， or even slightly contracted. With the increase of curing age， the partition interface between MgO particles and the surrounding cement paste in the concrete show a gradual integration， and the O and Mg atomic ratios in MgO particles show a gradually increasing trend.