改性粉煤灰对改善高铁相水泥砂浆性能的研究

Study on improving performance of high iron phase cement mortar by modified fly ash

为了进一步提升海洋工程中所用水泥基材料的抗海水侵蚀能力,提出在粉煤灰表面接枝憎水性油酸小分子,与一种新型高铁相水泥(C4AF≥18%,C3S≤50%)进行复合,制备改性水泥砂浆以提高砂浆基体的憎水性,从而改善砂浆的抗渗性能。研究结果表明:①若油酸改性粉煤灰的比例超过3%,水泥砂浆的力学性能会明显降低,但是其抗渗性能得到较大提升。这是由于离子在混凝土中的渗透是以水为介质,利用油酸改性后的粉煤灰在砂浆中均匀分布,使得基体具有良好的憎水性,因此砂浆整体的抗氯离子渗透性能得以提升。②选择蒸汽养护的方式能使高铁相水泥砂浆的早期强度得到提升。这是由于环境温度升高加快了水化反应速率,有利于促进水化反应进程,提高砂浆早期强度,而水化反应加快也会促进氢氧化钙的产生,使粉煤灰的二次火山灰反应提前,因此空白组砂浆的28 d强度较有所提升。

It is proposed to graft the hydrophobic oleic acid molecule on the surface of fly ash, and to prepare the modified cement mortar by adding a new type of high iron phase cement (C4AF ≥ 18%, C3S ≤ 50%), in order to improve the hydrophobicity of mortar matrix and further improve the impermeability of mortar. In order to research the improving performance of high iron phase cement mortar performance by modified fly ash, a series of tests were carried out. The results showed that if the proportion of oleic acid in modified fly ash was more than 3%, the mechanical properties of cement mortar would reduced obviously, but the impermeability of cement mortar would be improved greatly. This is due to the fact that water was the the medium for ions in concrete to penetrate, and the uniform distribution of oleic acid modified fly ash in mortar made the matrix have good hydrophobicity, so the overall resistance to chloride ion penetration of mortar can be improved. Steam curing can improve the early strength of high iron phase cement mortar, which was due to the fact that the increase of ambient temperature accelerated the hydration reaction rate, process and thus improved the early strength of mortar. The acceleration of hydration reaction also promoted the production of CH and advanced the secondary pozzolanic reaction of fly ash, so the strength of mortar at the age of 28 days was higher than that of the control group.