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

Nano-Structural Change of C(N)-A-S-H Gel in Alkali-Activated Slag Pastes Subjected to Wetting-Drying Cyclic Sulphate Attack

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,^(29)Si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_(2)SO_(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_(2)SO_(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_(2)SO_(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。

Nano-structural change of calcium(sodium)aluminium silicate hydrates(C(N)-A-S-H)gel in alkali-activated slag(AAS)mortars after wetting-drying cyclic attack in 5%(mass fraction,the same below)and 10%sulphate solutions was investigated.The structural and compositional changes of aluminosilicate chains in the main binding phases(C(N)-A-S-H)in AAS mortars were analyzed by Fourier-transform infrared spectroscopy,thermogravimetry-differential scanning calorimetry,29 Si magic angle spinning nuclear magnetic resonance,backscattered scanning electron microscopy and transmission electron microscopy-energy dispersive X-ray spectroscopy.The results show that the sulphate attack increases the degree of reaction of ground granulated blast-furnace slag regardless of sulphate salt type.The main corrosion products in MgSO_(4)solutions are gypsum,which is not detected in the samples subjected to Na_(2)SO_(4)solutions.The C(N)-A-S-H with longer chains prefers to be attacked in MgSO_(4)solutions,whilst the end-members of the chains or short chains of C(N)-A-S-H are broken in Na_(2)SO_(4)solutions.The C(N)-A-S-H after cyclic water attack is a mixture of tobermorite/jennite dimer to undecamer(T/J2-T/J11),while the Na_(2)SO_(4)solutions attack results in the destroy of shorter chains and the increase of protonation(or Na-balanced ratio),thus forming a new C(N)-A-S-H gel.