Wu Taige, Wang Honghu, Rong Zhidan
School of Engineering, University of Birmingham, Birmingham B15 2TT, UK.
China Machinery International Engineering Design & Research Institute Co., Ltd.-East China Branch, Nanjing 210023, China.
Materials (Basel). 2024 Aug 28;17(17):4253. doi: 10.3390/ma17174253.
Silica fume (SF) is an essential component in ultra-high-performance concrete (UHPC) to compact the matrix, but the nucleus effect also causes rapid hydration, which results in high heat release and large shrinkage. In this paper, the carboxylic agents, including polyacrylic acid and polycarboxylate superplasticizer, were used to surface modify SF to adjust the activity to mitigate hydration at an early time and to promote continuous hydration for a long period. The surface and dispersion properties of modified SF (MSF), as well as the strength and pore structure of UHPC, were studied, and the stability of the modification was also investigated. The results demonstrated that, after treatment, the carboxylic groups were grafted on the SF surface, the dispersion of SF was improved due to the increased negative pentanal of the particle surface and the steric hindrance effect, the early hydration was delayed about 3-5 h, and the hydration heat release was also mitigated. The compressive strength of UHPC with MSF reached a maximum of 138.7 MPa at 3 days, which decreased about 3.7% more than the plain group, while flexural strength varied insignificantly. More pores and cracks were observed in the matrix with MSF, and the hydration degree was promoted with MSF addition. The grafted group on SF fell off under an alkali environment after 1 h.
硅灰（SF）是超高性能混凝土（UHPC）中用于压实基体的重要组分，但核效应也会导致快速水化，从而产生高放热和大收缩。本文采用包括聚丙烯酸和聚羧酸减水剂在内的羧酸类试剂对硅灰进行表面改性，以调节其活性，在早期减轻水化，并促进长期持续水化。研究了改性硅灰（MSF）的表面和分散性能以及UHPC的强度和孔结构，并对改性的稳定性进行了研究。结果表明，处理后羧酸基团接枝在硅灰表面，由于颗粒表面负电位增加和空间位阻效应，硅灰的分散性得到改善，早期水化延迟约3 - 5小时，水化热释放也得到减轻。含MSF的UHPC在3天时抗压强度最高达到138.7 MPa，比空白组降低约3.7%，而抗折强度变化不显著。含MSF的基体中观察到更多气孔和裂纹，添加MSF促进了水化程度。硅灰上的接枝基团在碱性环境下1小时后脱落。
