炉底灰-粉煤灰胶凝体系的力学性能及微观分析

Mechanical properties and microscopic analysis of coal bottom ash-fly ash cementitious system

为实现炉底灰的大规模资源化利用,研究了原料掺量对炉底灰-粉煤灰胶凝体系力学性能的影响,采用X射线衍射、红外光谱、扫描电镜和能谱分析对胶凝体系水化产物的矿物组成、化学结构和微观形貌进行分析,结果表明:水泥掺量一定时,随着炉底灰掺量的提高,试样28 d抗压强度不断增大,而各龄期抗折强度及3,7 d抗压强度呈先增大后减小的趋势,粉煤灰对于提高胶凝体系早期强度具有不可或缺的作用,但掺量不宜过多;炉底灰可促进水泥中硅酸钙早期水化,生成更多氢氧化钙和钙矾石;水化后期,随着炉底灰掺量增大,C-S-H凝胶生成量增多并连接成密实的整体,针状文石晶体及纺锤形碳酸钙晶体桥接于水化试样微观裂隙两侧,阻碍裂隙的扩展,进一步提高胶凝试样的力学强度。

In order to realize large-scale resource utilization of coal bottom ash,the effect of raw material content on the mechanical properties of coal bottom ash-fly ash cementing system was studied.X-ray diffraction,infrared spectroscopy,scanning electron microscopy and energy dispersive spectroscopy were adopted to study the mineral composition,chemical structure and microtopography of the hydrated product of the cementitious system.The results indicated that when the amount of cement was fixed,with the increase of the amount of coal bottom ash,the compressive strength of the 28 d specimen continued to increase,and the compressive strength of binding system at each stage and the compressive strength of 3 d and 7 d cementitious system increased first and then decreased.Fly ash played an indispensable role in improving the early strength of cementitious system,but the amount should be controlled within a proper range.The coal bottom ash could promote the early hydration of calcium silicate in the cement to produce more calcium hydroxide and ettringite.In the later stage of hydration,as the amount of coal bottom ash increased,the amount of C-S-H gel increased and connected into a dense whole.The acicular aragonite crystal and spindle-shaped calcium carbonate crystal bridged on both sides of the micro-crack in the hydration samples,which hindered the expansion of the crack and further improved the mechanical strength of the cementitious samples.