基于自修复效应的封孔材料裂隙自愈合特性

Self-healing characteristics of fracture in sealing materials based on self-healing effect

水泥基材料是煤矿井下最常用的注浆封孔材料,但是受应力扰动、水泥材料失水收缩等影响,传统水泥基材料容易形成再生裂隙,导致钻孔内瓦斯抽采率降低。为了减小再生裂隙对瓦斯抽采效果的影响,研发一种自修复水泥封孔材料,当注浆位置再次产生裂隙后可实现裂隙的自愈合。首先,通过裂隙自修复实验研究了自修复水泥在空气条件下的裂隙自修复性能,采用高倍测量显微镜记录裂隙在不同时间内的宽度变化规律,发现在自然空气条件下,自修复水泥在4 d内能够修复最大宽度为0.46 mm的裂隙,裂隙处生成大量白色矿物,14 d内修复物体积仍有明显增长。刮去修复产物后,仍有白色矿物生成。为进一步研究自修复产物的生成机理,通过SEM-EDS对比分析了自修复水泥以及不加修复剂的净水泥2种水泥水化7、21 d的微观形貌和微观元素分布,并通过XRD、拉曼光谱仪对比分析了2种水泥的物相信息。SEM-EDS结果显示,净水泥中针状物质和絮状物质相互交联,整体结构致密,而自修复水泥中分布大量多孔状物质,结构比较疏松。相较于净水泥,自修复水泥水化产物中C、Na、Al、Si四种元素的质量分数明显较高。裂隙修复物表面分布大量排列紧密的长条状物质,主要元素组成为C、O、Na、Ca。XRD结果显示,和净水泥相比,自修复水泥中出现更多未水化硅酸三钙的衍射峰,相同水化时间,净水泥水化产物主要是氢氧化钙和钙矾石,而自修复水泥中出现了钠长石、沸石等铝硅酸盐矿物。裂隙修复物由沸石、钙霞石、硅灰石等多种硅酸盐矿物以及碳酸钙组成,其中碳酸钙的衍射峰数目最多。拉曼光谱结果显示,同净水泥相比,自修复水泥在2860~2960 cm^(-1)处具有明显拉曼谱峰,水化7 d,净水泥拉曼峰普遍尖锐,而自修复水泥拉曼峰明显更宽。净水泥中出现较多高强度氢氧化钙的拉曼峰,而自修复水泥中则出现更多CO_(3)^(2-)中C—O振动的拉曼峰,峰面积更大,由此可知自修复水泥更易和空气中CO_(2)反应发生碳化。水化21 d,2种水泥的拉曼峰都很尖锐,主要物相都是水化硅酸钙和氢氧化钙,而自修复水泥中还包括了大量未水化硅酸三钙。最终,分析了二次水化作用及碳化作用对裂隙自修复的影响,并结合实验结果推导了裂隙修复产物的生成方程式。

Cement-based materials are the most commonly used grouting and sealing materials in underground coal mines,but due to the effects of stress perturbation as well as water loss and shrinkage of cementitious materials,the traditional cementitious materials are prone to regeneration cracks,which leads to the reduction of gas extraction rate in the boreholes.In order to reduce the influence of regenerated fissures on the gas extraction effect,a self-repairing cement sealing material is developed,which can realize the self-healing of fissures when the fissures are generated again at the grouting location.Firstly,the self-healing performance of self-healing cement under air conditions was studied through the fissure selfhealing experiment,and a high-magnification measuring microscope was used to record the change rule of the fissure width over time.It was found that the self-healing cement was able to repair the fissure with the maximum width of 0.46 mm in 4 d under the natural air conditions.A large amount of white minerals were generated at the fissure,and the volume of repaired material still increased significantly in 14 d.After scraping off the repair products,white minerals were still generated.In order to further study the generation mechanism of the self-repair products,the microscopic morphology and microelement distribution of the two kinds of cements hydrated for 7 and 21 d were comparatively analyzed by SEM-EDS,and the physical phase information of the two kinds of cements was comparatively analyzed by XRD and Raman spectroscopy.The SEM-EDS results showed that,for the traditional cement,the needle-like and flocculent materials were crosslinked with each other and the overall structure was dense,whereas a large number of porous materials were distributed in the self-healing cement and the structure was relatively loose.Compared with the traditional cement,the mass fractions of four elements,C,Na,Al and Si,in the hydration products of the self-repairing cement were significantly higher.A large number of tightly arranged long strips are distributed on the surface of the fissure repair products,and the main elemental compositions are C,O,Na,and Ca.The XRD results showed that more diffraction peaks of unhydrated tricalcium silicate appeared in the self-healing cement compared with the traditional cement,and the hydration products of the traditional cement were mainly calcium hydroxide and calcium alumina for the same hydration time,while aluminosilicate minerals such as sodium feldspar and zeolite appeared in the self-healing cement.The fracture restorations consisted of various silicate minerals such as zeolite,calcium chalcocite and wollastonite as well as calcium carbonate,of which calcium carbonate had the highest number of diffraction peaks.The Raman spectral results showed that compared with the traditional cement,the self-healing cement had obvious Raman spectral peaks at 2860-2960 cm-1.At 7 d of hydration,the traditional cement Raman peaks were generally sharp,while the self-healing cement Raman peaks were significantly broader.More Raman peaks of high-intensity calcium hydroxide appeared in the traditional cement,while more Raman peaks of C—O vibration in CO_(3)^(2-)appeared in the self-healing cement with larger peak area,which shows that the self-healing cement is more likely to react with CO_(2)in air to carbonize.At 21 d of hydration,the Raman peaks of both cements were sharp,and the main phases were hydrated calcium silicate and calcium hydroxide,while the self-healing cement also included a large amount of unhydrated tricalcium silicate.Finally,the effects of secondary hydration and carbonation on fracture self-healing were analyzed,and the equations for the generation of fracture repair products were deduced combining the experimental results.