防灭火水泥基泡沫的凝结特性测试新方法及应用

New Method to the Test Setting Time of Foam Cement for Mine Fire Control and Its Application

水泥基泡沫流体具有良好的裂隙渗流、向上堆积性,且在凝结固化后拥有优越的隔热能力,已成为防治煤自燃的主要技术支撑材料。其在高温煤岩裂隙中的渗流扩散形态、现浇施工中灌注量、灌注范围的界定很大程度上取决于其凝结特征。针对目前关于水泥基泡沫流体凝结特性测试方法的不足,本研究对水泥基泡沫流体凝结过程水化产物进行微观分析,得出泡沫流体凝结过程为泡沫壁凝结,稳定性增强,结构不易变形,单个泡沫体流动阻力加大,流动困难的工作机理;进而提出了一种失去流动时间(Loss fluidity time,LFT)指标,用于表征水泥基泡沫流体的凝结特性,并发明了相应的测试装置及方法。实验研究了防灭火用水泥基泡沫的LFT和水基泡沫掺量(1V,2V,……7V)、促凝剂种类(AC1、AC2、AC3、AC4)、促凝剂掺量(3wt.%、5wt.%、7wt.%,……15wt.%)之间的关系,得出了采用5次多项式描述凝结时间与水基泡沫添加量及促凝剂浓度之间的耦合规律,并根据现场灭火工程要求,优选出促凝剂种类为AC3。

Foam cement has been the main technique for preventing the coal from spontaneous combustion because of its good seepage through the fresh cracks and thermal insulation ability after solidification.The seepage pattern,perfusion quantity and spread range in the mining fractures with high temperature all depends largely on the setting property of foam cement.Aiming at the deficiencies of the current test methods of foam cement,microscopic process of setting was analyzed by scanning electron microscope（SEM）.The results showed that the coagulation of single bubble wall and bubbles interconnecting led ISF to lose fluidity gradually.The lose fluidity time（LFT）index was then proposed on the basis of field process requirements and aforementioned microscopic analysis.Effects of aqueous foam volume（1 V,2 V,……7 V）and accelerator type（AC1、AC2、AC3、AC4）along with its addition quantity（3 wt.%,5 wt.%,7 wt.%,……15 wt.%）on the LFT of foam cement were investigated on a homemade instrument.The relationship equation may provide a theoretical foundation for steerable adjustment on LFT,and the AC3 was selected as the best accelerator according to the site fire-fighting engineering requirement.