碱激发偏高岭土-矿渣对氯离子的固化能力及其影响因素

Chloride binding ability of alkali activated metakaolin/slag blends and its influencing factors

氯离子的固化能力影响到碱激发偏高岭土-矿渣代替水泥用于混凝土结构的耐久性.为此,研究碱激发偏高岭土-矿渣硬化浆体(Alkali activated metakaolin-slag,AAMS)固化氯离子的能力,通过等温吸附平衡法和X射线衍射(XRD)方法考察了矿渣掺量、激发剂模数和激发剂浓度等因素的影响.研究结果表明:AAMS对氯离子的固化能力主要归因于C/N-A-S-H和C-S-H凝胶对氯离子的物理吸附;碱激发偏高岭土的氯离子固化能力较水泥净浆(PC)差,但矿渣掺入后可以提高碱激发偏高岭土对氯离子的固化能力;Langmuir等温线对AAMS固化后的游离氯离子与结合氯离子之间的关系具有更好地拟合效果.AAMS对NaCl溶液中氯离子的固化效果受NaCl溶液浓度的影响,对高浓度(>1.0 mol/L)NaCl溶液的吸附更加显著.AAMS对氯离子的固化能力随激发剂模数和激发剂浓度的减小而增大,尤以激发剂浓度的影响为最,且随矿渣掺量的增加,二者对AAMS固化氯离子的影响越显著.

The ability to bind chloride ions is related to the durability of alkali activated metakaolin-slag blends in place of cement for concrete structures.In this work,the effects of slag dosage,activator modulus,concentration of activator and other factors on the ability of the alkali activated metakaolin-slag blends(AAMS)to bind chloride ions were studied by isothermal adsorption equilibrium method and X-ray diffraction(XRD)method.The results show that the binding ability of AAMS for chloride ions is mainly attributed to the physical adsorption of chloride ions by C/N-A-S-H and C-S-H gels.The chloride binding ability of alkali-activated metakaolin is poorer than that of cement paste(PC),but slag incorporation can improve the binding ability of alkali-activated metakaolin for chloride ions.Langmuir isotherm has a better fitting effect on the relationship between free chloride ions and bound chloride ions after AAMS binding.The binding effect of AAMS is influenced by the concentration of NaCl solution,which is more significant for high concentration(>1.0 mol/L)NaCl solution.The binding ability of AAMS on chloride ions increases with the decrease of activator modulus and activator concentration,especially the effect of activator concentration is the most important,and with the increase of slag dosing,the more significant the effect of both on AAMS binding chloride ions.