C3A掺量对C3A-C3S浆体微结构的影响

Effect of C3A Content on Microstructure of C3A-C3S Paste

采用X射线衍射(X-ray Diffraction,XRD)、29Si核磁共振(29Si Nuclear Magnetic Resonance,29Si NMR)、27Al核磁共振(27Al Nuclear Magnetic Resonance,27Al NMR)和BET氮吸附等方法研究了标准养护条件下C3A掺量对C3S-C3A复合浆体微结构的影响。结果表明:C3A的加入可以促进C3S-C3A复合浆体的水化,释放的Al^3+可以进入C-S-H凝胶硅氧链上的桥硅氧四面体位置,形成Al掺杂C-S-H凝胶;随C3A掺量增大,复合浆体中C-S-H凝胶的Al[4]/Si和MCL增大;随养护龄期增大,Al掺杂C-S-H凝胶硅氧链上的Al[4]逐渐脱出,进入浆体并转化为Al[6],导致相同C3A掺量下的复合浆体中Al[4]相对含量下降,Al[6]相对含量增长;C3A的加入在降低复合浆体平均孔径的同时,也提高了浆体的孔隙率。

X-ray diffraction(XRD),29Si nuclear magnetic resonance(29Si NMR),27Al nuclear magnetic resonance(27Al NMR)and BET nitrogen adsorption were used to study the effect of C3A content on the microstructure of C3S-C3A composite paste under standard curing conditions.The results show that the addition of C3A can promote the hydration of C3S-C3A composite paste,and the Al^3+released can enter the position of the bridge silicon oxy tetrahedron on the silica gel chain of C-S-H gel to form C-S-H gel of Al incorporation.With the increase of C3A content,the Al[4]/Si and MCL of C-S-H gel will increase.With the increase of curing age,the Al[4]on the C-(A)-S-H silica gel chain gradually disappears and enters the paste with Al[6]form,resulting in the decrease of the relative content of Al[4]and the increase of Al[6]relative content in the composite paste with the same C3A content.The addition of C3A reduces the average pore size of the composite paste while increasing the porosity of the paste.