海水侵蚀环境下混凝土材料微观结构分析

Analysis of microstructure of concretes utilized under marine environments

采用数显显微硬度计、扫描电子显微镜、X射线衍射仪、压汞仪和固体核磁共振波谱仪分析了混凝土材料的细观实验力学性能、微观形貌、化学组成和孔隙结构。结果表明:海水侵蚀环境下,混凝土界面区附近聚集石膏、钙矾石等晶体,导致溶出性或膨胀性破坏;通过掺入矿粉,细化混凝土的孔隙、改善界面区的力学性能,但矿粉掺量超过30%后的孔隙细化效果不佳,且使孔径分布呈两极化趋势,无害孔和多害孔明显增加,少害孔和有害孔急剧减少;核磁共振波谱仪分析表明其胶凝体系中29Si所对应的共振频率降低,化学位移向负值方向移动,凝胶产物中的硅氧四面体除以Q1、Q2和Q2(1Al)形式存在,还以Q3和Q4形式存在。

The evolution of microstructure of concretes utilized under marine environments was studied by mi-crohardness,SEM,XRD,MIP and 29 Si MAS NMR.The results showed that concrete under marine environ-ments is apt to be destroyed by dissolution or expansion damage due to the roles of gypsum and ettringite easily gathering in interface transition zone.Slag-incorporated Concrete is obviously less porous and the mechanical properties of the interface transition zone are enhanced.However,with the slag content of more than 30%,the pore refining effect is less significant and the distribution of pore diameter is bipolarized,the harmless pores and much harm pores are obviously increased,while harmful pores and less harm pores are reduced.There exist [SiO 4 ]tetrahedrons of hydration products in forms of Q3 and Q4 in addition to the forms of Q1 ,Q2 and Q2 （1Al）,which can be resulted from the reduced resonance frequency of 2 9 Si and the chemical shift with a shift to negative.