This paper presents an experimental investigation on geopolymeric recycled aggregate concrete filled steel tubular (GRACFST) columns in fire. A total of 12 specimens were tested, including 6 circular columns and 6 square columns subjected to combined fire and loading. The test parameters include: (a) cross-section type (circular and square); (b) column load ratio (0.3, 0.4 and 0.6); and (c) fire scenario (all around fire exposure and two surfaces fire exposure). The failure mode, temperature development, deformation development and fire resistance of GRACFST columns were obtained and discussed. Finally, the fire resistance design method for conventional CFST columns proposed in Eurocode 4 was used to predict the ultimate cross sectional load bearing capacity of the GRACFST column at a specified fire exposure time, and the comparison between the prediction and the test results reported in this paper indicated that the Eurocode 4 method gave an overestimation to the GRACFST column. To improve the prediction accuracy, suitable material models for the passively confined GRAC in CFST columns should be developed in the future research.
The ultrafine silver powders were prepared by liquid reduction method using Arabic gum as dispersant. The effects of different dispersants, pH values, and temperature on the morphology and particle size of silver powders were investigated. It is found that Arabic gum can better adsorb on silver particles via chemical adsorption, and it shows the best dispersive effect among all the selected dispersants. The particle size of silver powders can be finely tuned from 0.34 to 4.09 μm by adjusting pH values, while the morphology of silver powders can be tuned by changing the temperature. The silver powders with high tap density higher than 4.0 g/cm3 were successfully prepared in a wide temperature range of 21.8–70 °C. Especially, the tap density is higher than 5.0 g/cm3 when the temperature is optimized to be 50 °C. The facile process and high silver concentration of this method make it a promising way to prepare high quality silver powders for electronic paste. 相似文献