Study on Fresh Properties of Alkali-activated Concrete with Slag and Fly Ash

• Main Authors: Jyun-Jie Huang, 黃俊傑
• Other Authors: Ta-Peng Chang
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/92482171932003818373

碩士 === 國立臺灣科技大學 === 營建工程系 === 104 === In this study, the sodium silicate and sodium hydroxide were used as the alkali activator. After trial mixes, the liguid-solid ratio was fixed as 0.5, and the experimental parameters including different dosages of activator, silicon-sodium ratio and proportions of slag-fly ash mixtures were used to investigate the effects of various combinations of parameters on the fresh, physical, durable and microstructural properties of the alkali-activated concrete with slag and fly ash. The research results show that: (1) For the fresh properties, the slump of alkali-activated slag-fly ash concrete were in the range from 220 to 270 mm, and the slump flow were in the range from 360 to 600 mm, and the initial and finial setting times of concrete were from 529 to 684 and 556 to 745 min, respectively. Increase of dosages of activator could not significantly change the workability and setting times. (2) The air content of alkali-activated slag-fly ash concrete was in the range from 0.3 to 2.8 %. Increase of dosages of activator and silicon-sodium ratio could decrease the air content. (3) The increase of dosages of activator could enhance the material strength such that the compressive strength of all mixture at 28 days were in the range from 21.43 to 48.03 MPa. However, when the slag powder mixed with fly ash being the inert ingrident, the concrete had lower compressive strength at 28 days by a decreaseof 13.1 to 38.3% if the amount of fly ash replacement replaced 50 wt. % of slag. (4) The thermal conductivities of all mixtures were in range from 1.227 to 1.854 w/m•k, which were lower than these of normal concrete by 18.2 to 47 %, that in turn showed that thealkali-activated slag-fly ash concrete had much better insulation properties. In addition, the properties of thermal conductivity were primarily controlled by composition of powder material rather than by the mixing liquid. (5) The increase of dosages of activator and and silicon-sodium ratio could increase the drying shrinkage of alkali-activated slag-fly ash concrete. (6) The increase of dosages of activator and and silicon-sodium ratio could increase the surface resistivity of alkali-activated slag-fly ash concrete. (7) The increase of dosages of activator and and silicon-sodium ratio could reduce the water absorption of alkali-activated slag-fly ash concrete. The higher the water absorption is, the higher the internal voids of concrete will be.