纳米氮化硅激活粉煤灰对矿用水泥封孔材料早强性能的影响

Activation effect of the fly ash with nano silicon nitride on the early strength properties of the mining-left cement sealing materials

针对煤矿用封孔水泥的候凝时间长、早期强度低、流动性能差等问题,以粉煤灰取代部分水泥为研究对象,引入纳米氮化硅,通过抗压强度、流动度、凝结时间、XRD、扫描电镜(SEM)、热重(TG-DSC)等力学性能测试和微观结构表征,研究纳米氮化硅对粉煤灰水泥早期强度的影响以及废弃粉煤灰的有效利用。结果表明,单独添加纳米氮化硅能适当提高水泥试样的早期抗压强度,将纳米氮化硅与粉煤灰复配使用能表现出较好的协同作用。添加质量分数2%纳米氮化硅和10%粉煤灰时,水泥试样早强效果最为显著,1 d、3 d、7d抗压强度分别达到空白水泥试样的132.10%、145.30%、124.55%,且其候凝时间缩短,流动性良好。XRD和扫描电镜以及热重分析表明,纳米氮化硅的晶核作用激发了粉煤灰活性,加快了硅酸三钙的水化,生成更多水化硅酸钙凝胶吸附在纳米氮化硅颗粒及粉煤灰周围,使各凝胶相之间相互搭接形成均匀致密的空间网络结构,提高了水泥试样的早期强度和耐久性。

The given paper intends to introduce a nano-silicon nitride additive to solve the problems of the long waiting time,low early strength and the poor flow performance of the coal mine sealing cement. And,for the above said purposes,it would be necessary for us to test and examine the mechanical properties and microstructures of the cement by taking the fly ash cement as the testing sampling material in terms of its compressive strength,the fluidity,the setting time,as well as the XRD,SEM,TG-DSC items. For instance,we have examined the effect of the nano-silicon nitride on the early strength of the fly ash cement and the effective approach to the waste fly ash utilization. The results of our examination show that the early compressive strength of the cement samples can be improved by adding nano-silicon nitride,with the perfect synergistic effect to be gained by adding nano-silicon nitride and fly ash to it. For instance,when adding 2% of nano-silicon nitride and 10% of flyash to it,the early original strength of the cement sample would be able to produce the most significant effect,say,the compressive strength of the cement sample during the 1-st day,the 3-rd and the 7-th days,may tend to reach 132. 10%,145. 30% and124. 55% of that of the pure cement,respectively,with its setting time being shortened and its fluidity being nice. Besides,the XRD and SEM and the thermo-gravimetric analyses can also demonstrate that the nucleation of the nano-crystalline silicon nitride can stimulate the activity of the fly ash,and,in turn,accelerate the hydration of the calcium silicate,so as to bring about more calcium silicate hydrate gel. Moreover,the hydrated calcium silicate adsorbed by the nano-silicon nitride particles and the fly ash may tend to result in a uniform and dense spatial network structure to overlap each gel phase,which can promote the original strength and durability of the cement sample. In so doing,the innovation we have done in this paper can be said to bring about a new nano additive,which can provide for a brand-new way to stimulate the activities of the fly ash and then succeed in a substantial innovation of the performance of the mining sealing cement and transformation of the waste fly-ash into perspective profitable utilization.