摘要
通过系统探讨了高钙粉煤灰(HFA)与低钙粉煤灰(LFA)对磷酸镁水泥基超高性能混凝土(MPC-UHPC)水化行为及力学性能的影响机制。对比0~60%掺量范围内HFA/LFA对MPC-UHPC抗压强度、氯离子渗透性、干燥收缩及微观结构的调控规律,结合多尺度表征(SEM、XPS、MIP等),揭示了钙含量对火山灰反应激发和孔隙结构优化的作用机理。结果表明:HFA的高钙特性(CaO含量12.77%)在MPC体系高碱性环境中显著加速火山灰反应,促进C-(A)-S-H凝胶生成,有效填充孔隙并优化微观结构。掺入20%HFA的MPC-UHPC在90 d时抗压强度达153.4 MPa,较基准组(142.8 MPa)提升6.91%,且氯离子扩散系数(1.12×10^(-12)m^(2)/s)显著低于LFA组(1.33×10^(-12)m^(2)/s)。此外,HFA的微膨胀效应与物理填充协同抑制干燥收缩,其掺量20%时28 d收缩率较基准组降低30.7%。过量掺入(>50%)HFA/LFA会导致MPC-UHPC力学性能下降。MPC-UHPC中粉煤灰的优化掺量设计及工程应用提供了理论依据。
The effects of high-calcium fly ash(HFA)and low-calcium fly ash(LFA)on the hydration behavior and mechanical properties of magnesium phosphate cement-based ultra-high performance concrete(MPC-UHPC)were systematically investigated.The effects of HFA/LFA on the compressive strength,chloride ion permeability,drying shrinkage and microstructure of MPC-UHPC were compared in the range from 0 to 60%.Combined with multi-scale characterization(SEM,XPS,MIP,etc.),the mechanism of calcium content on pozzolanic reaction excitation and pore structure optimization was revealed.The results showed that the high calcium characteristics of HFA(CaO content 12.77%)significantly accelerated the pozzolanic reaction in the high alkaline environment of MPC system,promoted the formation of C-(A)-S-H gel,effectively filled the pores and optimized the microstructure.The compressive strength of MPC-UHPC with 20%HFA reached 153.4 MPa at 90 d,which was 6.91%higher than that of the reference group(142.8 MPa),and the chloride ion diffusion coefficient(1.12×10-12 m2/s)was significantly lower than that of the LFA group(1.33×10-12 m2/s).In addition,the micro-expansion effect of HFA and physical filling synergistically inhibited the drying shrinkage,and the 28 d shrinkage rate was 30.7%lower than that of the reference group when the content of HFA was 20%.Excessive incorporation(>50%)of HFA/LFA will lead to a decrease in the mechanical properties of MPC-UHPC.It provides a theoretical basis for the optimal dosage design and engineering application of fly ash in MPC-UHPC.
作者
胡勤
李猛
刘京
陈继东
HU Qin;LI Meng;LIU Jing;CHEN Jidong(College of Arts and Sciences,Yangtze University,Jingzhou 434020,China;Xiangyang Polytechnic,Xiangyang 441050,China;Zhongsheng Hongyu Engineering Consulting Co.,Ltd.,Wuhan 430000,China)
出处
《混凝土》
北大核心
2025年第7期95-102,共8页
Concrete
基金
教育部产学合作协同育人项目(220905377063130)
湖北省教育厅科学研究计划项目(B2022476)
湖北省教育科学规划课题(2022GB119)。
关键词
粉煤灰
磷酸镁水泥
UHPC
水泥水化
孔隙结构
fly ash
magnesium phosphate cement
UHPC
cement hydration
pore structure
