1 School of Mechanics and Civil Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China 2 Faculty of Civil Engineering, Beijing Jiaotong University, Beijing 100044, China 3 Beijing Construction Engineering Group, Advanced Construction Materials Limited Liability Company, Beijing 100015, China
Abstract: Influence of silicon carbide whiskers (SiCw) on mechanical properties of ultra-high performance concrete (UHPC) was investigated. Moreover, microstructure of UHPC modified by SiCw was determined by means of scanning electron microscopy, mercury intrusion porosimetry and X-ray diffraction analysis. The results showed that SiCw is not conducive to improving the mechanical properties of matrix at the early age (within 8 h), but has a positive effect on the mechanical properties in the later stage. This is mainly due to that the SiO2 protective film on the whiskers adsorbed Ca2+ in the solution at the early age, which can delay the hydration of cement to a certain extent. With the extension of curing age, the nucleation effect, filling effect and bridging effect of whiskers are effectively exerted. Meanwhile, the SiO2 protective film on the surface of SiCw may also react with calcium hydroxide crystals generated by the cement hydration, thus resulting in the formation of more additional C-(A)-S-H gels. In addition, larger aspect ratio increases the contact area between SiCw and the UHPC matrix to get stronger interface adhesion between them, resulting in more energy consumption during the pulling out process, which is more conducive to improving the mechanical properties of UHPC. However, excessive SiCw is difficult to uniformly disperse, and they easily aggregate in the matrix and form defects, which will adversely affect the mechanical properties of UHPC. The optimum dosage is 0.15% in this experiment.
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2025, Vol. 39 
