骨料对MgO混凝土开裂敏感性的影响研究

从几个典型工程中分别选取了玄武岩、角闪岩和灰岩这3种人工骨料以及花岗岩天然骨料，研究了骨料的长期吸水特性及其对MgO微膨胀混凝土变形性能的影响，利用温度应力试验机比较了用不同骨料配制的MgO微膨胀混凝土的开裂敏感性.试验结果表明，180d龄期时骨料的饱和面干吸水率相比24h时有大幅增长，骨料吸水率越高，混凝土的自收缩和干缩变形越大；采用玄武岩和角闪岩骨料配制的MgO微膨胀混凝土的开裂温度较低，元素聚类分析揭示用玄武岩和角闪岩骨料配制的混凝土界面区Ca，Mg元素富集程度较为显著，更多水化产物在此区域堆积，从而增加了界面区的密实度，有助于提高混凝土的抗裂能力.

Influence of Aggregates on Cracking Sensitivity of Micro expansive MgO Concrete

The long term water absorption of aggregates including artificial basalt, diorite, limestone and natural granite as well as its influence on deformation of MgO concrete were investigated. The cracking sensitivity of MgO concrete made from different aggregates was measured by advanced temperature and stress equipment (TST machine). Results indicated that obvious increment in water absorption of aggregates from 24h to 180d was observed and self shrinkage and drying shrinkage of concrete was closely related to water absorption of aggregates. The higher the water absorption, the bigger the shrinkage of concrete. Lower cracking temperature of MgO concrete made from basalt and diorite was shown according to the results of TST machine test.It is also shown that enrichment of Ca and Mg on interfacial transition zone of these two concretes was more obvious which implied denser compaction of hydration products favoring crack resistance of concrete.