石灰石粉在水泥浆抗氯离子渗透性中的作用机理

Action mechanism of limestone powder on resistance to chloride ion permeability of cement pastes

为了阐明氯离子和石灰石粉、铝相之间的相互作用,以及它们对水泥浆微观结构和氯离子渗透性的影响,通过X射线衍射仪和差热分析表征了水泥浆的物相,采用扫描电镜观测了水泥浆的微观形貌,借助压汞法测试了水泥浆的孔结构,通过RCM法表征了水泥浆的氯离子渗透性。在此基础上,研究了氯盐环境下,不同掺量和比表面积石灰石粉对水泥浆微观形貌和氯离子迁移系数的影响。研究结果表明,随着石灰石粉掺量的增大或比表面积的减小,水泥浆的氯离子迁移系数随之增大。当石灰石粉的掺量从0%增大到30%时,水泥浆的氯离子迁移系数从7.16×10^(−12)m^(2)/s增大到22.17×10^(−12)m^(2)/s。当石灰石粉的比表面积从500 m^(2)/kg增大到800 m^(2)/kg时,水泥浆的氯离子迁移系数从22.17×10^(−12)m^(2)/s降低到20.57×10^(−12)m^(2)/s。在氯盐环境下,碳铝酸钙的XRD衍射峰随之消失,并形成了Friedel’s盐的衍射峰。随着石灰石粉掺量的增大,Friedel’s盐含量先增大后降低。当石灰石粉掺量为10%时,Friedel’s盐含量最高,增大到了3.70%。当石灰石粉比表面积从500 m^(2)/k增大到800 m^(2)/k,Friedel’s盐含量从3.02%增大到3.63%,水泥浆最可几孔径从38.72 nm降低到36.54 nm,孔隙率从25.63%降低到25.24%,改善了水泥浆的微观结构,从而提高了水泥浆的抗氯离子渗透性。在氯盐环境下,石灰石粉掺量不宜超过20%,建议石灰石粉的比表面积为800 m2/kg,以提高掺石灰石粉水泥基材料的抗氯离子渗透性。

To clarify the interaction between chloride ions,limestone powder and aluminum phase,and their influences on the microstructure and chloride ion permeability of cement pastes,the phase was analyzed by X-ray diffractometer(XRD)and differential thermal analysis.The micromorphology was observed by scanning electron microscope.The pore structure was measured by mercury intrusion method.The chloride ion permeability was tested by RCM methods.On this basis,effects of limestone powder with different amount and specific surface area on the microstructure and chloride ion migration coefficient of cement pastes under chloride salt environment were investigated.Test results show that with the increase of limestone powder amount or the decrease of specific surface area,the chloride ion migration coefficient of cement pastes increased.When the content of limestone powder increased from 0%to 30%,the chloride ion migration coefficient of cement pastes increased from 7.16×10^(-12)m^(2)/s to 22.17×10^(-12)m^(2)/s.When the specific surface area of limestone powder increased from 500 m^(2)/kg to 800 m^(2)/kg,the chloride ion migration coefficient of cement pastes decreased from 22.17×10^(-12)m^(2)/s to 20.57×10^(-12)m^(2)/s.Under the chloride salt environment,the XRD diffraction peak of calcium aluminate disappeared,and the diffraction peak of Friedel’s salt was formed.With the increase of limestone powder content,the Friedel’s salt content first increased and then decreased.When the limestone powder amount was 10%,the Friedel’s salt content was the highest,which was 3.70%.When the specific surface area of limestone powder increased from 500 m^(2)/kg to 800 m^(2)/kg,the Friedel’s salt content increased from 3.02%to 3.63%,the most probable pore size decreased from 38.72 nm to 36.54 nm,and the porosity decreased from 25.63%to 25.24%,which improved the microstructure of cement pastes,thereby increasing the resistance to chloride ion permeability of cement pastes.In the chloride salt environment,in order to improve the resistance to chloride ion permeability of cement-based materials mixed with limestone powder,the limestone powder content should be less than 20%,and the specific surface area of limestone powder was suggested to be 800 m2/kg.