| With the rapid development of China's steel industry,steel slag is a by-product of the steelmaking process,and its output is gradually increasing.In 2018,about 121 million tons of steel slag were produced in China,and the comprehensive utilization rate was only 30%.More steel slag was used as a solid Waste accumulates,so the reuse of steel slag is urgent.As the cement admixture,steel slag is the most efficient and green utilization route,but it has not been widely used because of its hydration activity and volume expansion.In order to solve the problem of low early strength and expansion of steel slag as a cement admixture,This paper mainly studies the effect of the incorporation of Al2O3 and Al(OH)3 with different particle sizes and different crystal forms on the hydration and mechanical properties of steel slag cement composite cementitious materials.By comparing and studying the pozzolanic activity of Al2O3 and Al(OH)3 with different particle sizes and different crystal forms,and its influence on the strength and expansibility of steel slag cement composite cementitious materialsThe results show that the effect of nano-?-Al2O3 and nano-?-Al2O3 on the strength of the sample is significantly better than that of micro-?-Al2O3 and nano-Al(OH)3,and the addition of Al2O3 and Al(OH)3 has a much greater influence on the 3d and 7d strength of the sample than on the 28d strength of the sample,indicating that the addition of different particles significantly improves the early strength of the sample.Among them,the sample strength of nano-?-Al2O3 is the largest when the content is 5%,the sample strength of nano-?-Al2O3 is the largest when the content is 1%.Nano-?-Al2O3,nano-?-Al2o3 and nano-Al(OH)3 nanoparticles have a better effect on reducing the expansion rate of the sample than micro-?-Al2O3,and nano-?-Al2O3 has the best effect.According to the content of Ca(OH)2 in the hydration product of the sample,it can be obtained that:among micro-?-Al2O3,nano-?-Al2O3 and nano-?-Al2O3,nano-?-Al2O3 has the strongest pozzolanic activity and nano-?-Al2O3 activity Second,the activity of micro-?-Al2O3 is the weakest,and the reaction activity of nano-Al(OH)3 is similar to that of nano-?-Al2O3.With the increase of the amount of four different particles,the reactivity and degree will further increase.With the addition of different particles,the flaky Ca(OH)2 in the microstructure decreases,while the hydration gel products increases significantly,and the pores decrease,especially the macropores.Among them,the phenomenon of adding nano-?-Al2O3 and nano-?-Al2O3 is more obvious than that of micro-?-Al2O3.Nano-?-Al2O3 is due to its porous structure and its small particle size,which results in a large specific surface area and strong pozzolanic activity.At the same time,the particles are more likely to agglomerate,and the resulting sample requires a large amount of water,resulting in large viscosity of samples,and the sample is difficult to stir and shape and the particles are unevenly distributed in the sample after molding.While the agglomeration of the other three particles is significantly weaker than nano-?-Al2O3,making it more uniformly dispersed in the sample,and the resulting the water requirement of sample is small,and the high content will not cause the sample viscosity to rise sharply,and the sample is easy to stir and form. |
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