Effect of Colloidal Silica on the Hydration Behavior of Calcium Aluminate Cement

Abstract

The effect of colloidal silica (CS) on the hydrate phases and microstructure evolution of calcium aluminate cement (CAC) was investigated. Samples hydrated with CS were obtained and characterized by X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared spectroscopy (FT-IR), hydration heat measurement and Nuclear Magnetic Resonance (NMR). The results revealed that SiO2 nanoparticles may affect the hydrates crystallization process. There was a compact structure in the CAC paste with CS, while petal-shaped hydrates with a porous structure were formed in the pure CAC paste. The maximum value of electrical conductivity for CAC paste with CS suggested that the early stage of hydration for CAC was accelerated. However, the hydration heat curves revealed that the late stage of the CAC hydration process was inhibited, and the hydration degree was reduced, this result was in accordance with Thermogravimetry-Differential scanning calorimetry(TG-DSC) curves. The fitting results of hydration heat curves further showed that the hydration degree at NG (nucleation and crystal growth) process stage was promoted, while it was limited at the phase boundaries stage, and the diffusion stage in the hydration reaction was brought forward due to the addition of CS. According to these results and analyses, the differences in the hydration process for CAC with and without CS can be attributed to the distribution and nucleation effect of SiO2 nanoparticles.

Properties of Alkali-Activated Slag Paste Using New Colloidal Nano-Silica Mixing Method

“…So far, studies using nano-particles in the OPC base have shown improved mechanical properties and durability [6,7,8]. The cause of this improvement in OPC was found to be the nucleation effect, pozzolanic reaction and filler effect of nano-particles [9,10,11]. However, the research results of nano-particles based on OPC have pointed to a drastic decrease in fluidity as a major disadvantage [12,13].…”

De-Powdering Effect of Foundry Sand for Cement Casting

“…However, CAH10 and C2AH8 are metastable and are known to get converted to the more stable C3AH6 and AH3 species. In Figure 5a, every sample shows an AH3 conversion endothermic signal at 240 °C [28,29]. Additionally, all samples exhibit an inflection point with varying strengths near 800 °C.…”

“…However, CAH 10 and C 2 AH 8 are metastable and are known to get converted to the more stable C 3 AH 6 and AH 3 species. In Figure 5a, every sample shows an AH 3 conversion endothermic signal at 240 • C [28,29]. Additionally, all samples exhibit an inflection point with varying strengths near 800 • C. The DSC profile of the S + C sample showed that siliceous sand sintering occurs at approximately 1250 • C, resulting in a strong bond between the sand, but the strength of the actual mold body does not significantly increase.…”

Improving the green mechanical strength and thermal shock resistance of colloidal silica‐bonded castables using La2O3

“…Nevertheless, it has been reported that the chemical bonds formed by colloidal silica particles and external metal ions contribute to enhancing the green strength of corundum castables. [29][30][31] To determine if the La 3+ ions produced by the hydration of La 2 O 3 are involved with the build-up of a three-dimensional network structure. The effect of La 2 O 3 on the chemical bond reorganization during the gelation process of colloidal silica was investigated by FTIR and XPS.…”