MgO反应活性对外掺MgO碾压混凝土性能的影响

Influence of MgO reactivity on the properties of RCC mixed with MgO

采用力学试验、变形观测、压汞测试、扫描电镜观察等手段,研究MgO膨胀剂的反应活性对外掺MgO碾压混凝土的力学性能、自生体积变形及微观结构的影响。结果表明,随着MgO反应活性提高,混凝土在龄期28、90 d的强度增大,在龄期360 d的孔体积减少、孔隙率降低;反应活性越高的MgO,成型的碾压混凝土的早期自生体积变形越大,但后期的膨胀速率减小,膨胀稳定早;反之,早期的自生体积变形越小,后期的膨胀速率增加。在为坝体混凝土选择氧化镁膨胀剂时,活性指数不宜太小,也不宜太大。

The effects of magnesium oxide(MgO for short)expansion agent reactivity on the mechanical properties,autogenous volume deformation and microstructure of roller compacted concrete(RCC for short)mixed with MgO were studied by means of mechanical experiment,deformation observation,mercury injection test and scanning electron microscope.The results show that the strength of concrete increases at 28 d and 90 d,and the pore volume and porosity decreases at 360 d with the increase of MgO reactivity.The autogenous volume deformation of RCC formed by MgO with higher reactivity increases in the early stage,but the expansion rate decreases in the later stage and the expansion stabilizes earlier.Conversely,the smaller the autogenous volume deformation is in the early stage,the higher the expansion rate is in the later stage.When selecting magnesium oxide expansion agent for dam concrete,the activity index of MgO should not be too small or too large.