干湿循环硫酸盐环境下碱矿渣水泥C(N)-A-S-H凝胶结构演化规律

The changes in the structure of calcium silicate hydrate [C(N)-A-S-H] gel in alkali-activated slag cement mortar under dry-wet cycling conditions in 5% (mass fraction, the same below) and 10% sulfate solutions were studied. Fourier transform infrared spectroscopy, comprehensive thermal analysis, 29Si magic angle spinning nuclear magnetic resonance, backscattered scanning electron microscopy and transmission electron microscopy - energy dispersive spectroscopy were used to analyze the phase composition in the mortar and the changes in the chemical structure of the C(N)-A-S-H gel. The results show that sulfate erosion increases the hydration degree of slag in alkali-activated slag (AAS) cement mortar and changes the structure of the C(N)-A-S-H gel. After dry-wet cycling erosion in MgSO4 solution, the main erosion product is gypsum; after erosion in Na2SO4 solution, gypsum was not detected; after erosion in MgSO4 solution, some long chains of the C(N)-A-S-H gel were broken; but erosion in Na2SO4 solution starts from the short chains or the ends of the long chains of C(N)-A-S-H, resulting in a significant increase in the average chain length. Under dry-wet cycling in water, the C(N)-A-S-H gel in AAS mortar can be interpreted as a mixture of tobermorite/hydroxyxonotlite dimers to hendeca -mers (T/J2 ~ T/J11), while after erosion in Na2SO4 solution, it can be regarded as a new C(N)-A-S-H gel with short chain destruction and increased protonation (or Na substitution rate).

研究了在5%(质量分数,下同)及10%硫酸盐溶液中干湿循环条件下,碱矿渣水泥砂浆中水化硅酸钙[C(N)-A-S-H]凝胶结构的变化。使用Fourier变换红外光谱,综合热分析,29Si魔角自旋核磁共振,背散射扫描电子显微镜及透射电子显微镜–能谱分析了砂浆中物相组成及C(N)-A-S-H凝胶的化学结构变化。结果表明:硫酸盐侵蚀使碱矿渣(AAS)水泥砂浆中矿渣的水化程度增加且改变C(N)-A-S-H凝胶结构。在MgSO_4溶液干湿循环侵蚀后,产生的主要侵蚀产物为石膏;Na_2SO_4溶液侵蚀后,则未检测到石膏;当MgSO_4溶液侵蚀后,C(N)-A-S-H凝胶的部分长链发生了断裂;但Na_2SO_4溶液侵蚀从C(N)-A-S-H短链或长链端部开始,从而造成了平均链长显著增加。在水中干湿循环下,AAS砂浆中的C(N)-A-S-H凝胶可解释为托贝莫来石/羟基硅钙石二聚体至十一聚体(T/J2 ~ T/J11)混合物,而Na_2SO_4溶液侵蚀后,可以视为短链破坏且质子化(或Na取代率)提高的新的C(N)-A-S-H凝胶。