基于界面改性的水泥混凝土力学性能和机理

Mechanical Properties and Mechanism of Cement Concrete Based on Interface Modification

为了提高混凝土的力学性能,首先选取活性外加剂硅灰,采用内掺法将其掺入水泥,然后对不同硅灰掺量的净浆与混凝土进行了宏观力学试验;分别对比了硅灰对净浆与混凝土力学性能的改善结果,并分析了其产生改性结果差异的原因;最后结合扫描电子显微镜(scanning electron microscope,SEM)与X射线衍射(X-ray diffraction,XRD)微观试验技术探究了其改性机理。结果表明:硅灰的掺入对水泥净浆的力学性没有明显改善;基于界面改性的水泥混凝土其28d抗压强度提升幅度较大,当硅灰掺量为10%时,较未改性混凝土其抗压强度提升了26.4%,可以推断出硅灰改善了混凝土界面从而提高混凝土整体力学性能;对比界面改性前后混凝土扫描电镜图,硅灰不仅提高了水泥基体的密实度,还改善了混凝土界面的结构与密度,以及界面处水化产物氢氧化钙的排列方式;硅灰具有填充效应、促进二次水化反应及与氢氧化钙发生火山灰反应等特性,随着硅灰的掺量的增加,氢氧化钙含量减小,C_(3)S和SiO_(2)增加,利用硅灰与水化产物间的物理、化学作用,达到改善改性后混凝土综合性能的目的。

In order to improve the mechanical properties of concrete,the active admixture silica fume was first selected and mixed into the cement by the internal admixture method,and then macro-mechanical tests were carried out on the pure slurry and concrete with different silica fume content,the silica fume was compared respectively.The improvement results of ash on the mechanical properties of pure slurry and concrete were compared,and the reasons for the difference in the modification results were analyzed.Finally,the modification mechanism was explored by combining scanning electron microscope(SEM)and X-ray diffraction(XRD)microscopic test techniques.The results show that the addition of silica fume does not significantly improve the mechanical properties of the cement paste.The 28 d compressive strength of cement concrete based on interface modification is greatly improved.When the silica fume content is 10%,it is relatively unchanged.The compressive strength of concrete has increased by 26.4%.It can be inferred that silica fume improves the concrete interface and thus improves the overall mechanical properties of the concrete.Comparing the scanning electron microscope images of the concrete before and after the interface modification,silica fume not only improves the compactness of the cement matrix,but also improves the structure and density of the concrete interface,as well as the arrangement of the hydration product calcium hydroxide(CH)at the interface.Silica fume has the filling effect,promotes the secondary hydration reaction and the pozzolanic reaction with CH,etc.As the content of silica fume increases,its CH content decreases,C_(3)S and SiO_(2) increase,and the physical and chemical effects between silica fume and hydration products are used to improve the overall performance of the modified concrete.