Quantitative study on the dielectric properties of tricalcium silicate pastes under different W/C

Abstract

C3S (tricalcium silicate) pastes with water-cement ratio (W/C) of 0.23, 0.3, 0.4 and 0.5 were designed, and the influence of the dielectric properties of C3S paste were quantitatively analyzed. The results show that when the W/C is 0.23, the real part of permitivity of the C3S paste is the smallest. With increases of the W/C, the real part of permitivity of the C3S paste decrease, and the loss tangent increases. The real part of permitivity of C3S paste decreases with the increase of Ca(OH)2 and pore phases, and increases with the increase of C3S and CSH gel phase. The permitivity of C3S paste decreases most due to increase pore phase (about 4 times that of Ca(OH)2 phase), and increases most due to increase CSH gel phase (about 6.6 times that of C3S phase). The dielectric weight coefficient proposed in this study can well predict the changing trend of the real part of permitivity of C3S pastes with different W/C. Finally, based on the Thermogravimetric analysis (TGA), Scanning electron microscope (SEM), Mercury intrusion porosimetry (MIP), N2 adsorption and 29Si magic angle spinning nuclear magnetic resonance (29Si NMR) test results, the reasons of electromagnetic loss changes of C3S pastes with different W/C were analyzed from the molecular structure of CSH gel, the crystalline products and the pore structure of C3S paste.