Structural Build-Up of Cementitious Paste Under External Magnetic Fields

Engineering application processes of fresh concrete include transporting, pumping, formwork casting, etc. Each process is a significant factor influencing properties of fresh and hardened concrete. However, many contradicting requirements of fresh concrete performances (such as structuration rate) exist in these operation processes. Therefore, advanced techniques need to be proposed to satisfy future challenges. Actively controlling the stiffness by applying external magnetic fields would be a potential solution for the contradicting requirements, and could make the pumping and casting processes smarter and more reliable. In the present paper, the effects of magnetic field strength and magnetizing time on structural build-up of cementitious paste are discussed. The results show that higher magnetic field strengths result in higher percolation time and lower phase angle at equilibrium state. However, the application of external magnetic fields with low flux density has little effects on the viscoelastic behaviour of cementitious paste. Under high magnetic field strengths, the viscous-liquid behaviour dominates the elastic-solid behaviour at early stage, while the solid-like behaviour becomes more dominant with magnetizing time.