Influence of vibrating compaction time on the strength and microstructure of ultra-high performance concrete

During the forming process of ultra-high performance concrete (UHPC), the duration of vibrating compaction plays a pivotal role in influencing its performance. Our study delved into the impact of various factors on the macroscopic mechanical properties, considering the influence of vibrating compaction time on the pore size distribution in the matrix, fibre distribution characteristics, and fibre-matrix interface. We employed SPSS software to analyse the correlation between different factors and UHPC strength. Based on our experimental findings, the influence of vibrating compaction time on the flexural and compressive strengths of UHPC varied within the 0-15 s vibration range. Notably, vibration time had a significant effect on the distribution of pores and fibres within the UHPC matrix. The alterations in pore size distribution and fibre distribution induced by vibrating compaction time were primarily responsible for its impact on UHPC strength. The study provides a solid theoretical foundation for optimising the vibrating compaction time in UHPC mixtures.