镁渣制备可控膨胀性胶凝材料的研究
发布时间：2018-08-30 20:53
【摘要】：镁渣是镁厂冶炼金属镁时产生的固体废弃物,但因出炉镁渣采取自然冷却的方式,导致镁渣料的活性低,并且存在滞后膨胀的现象,这一直是制约镁渣料应用的关键所在,如何提高镁渣料的活性,消除滞后膨胀危害对充分有效的利用镁渣有着重要的意义。本文通过对镁渣产生的条件及镁渣的机理分析后,制定先采用自制小型冷却设备对出炉镁渣进行冷却,并通过控制风量制备出不同冷却速率镁渣,分别为急冷镁渣、半急冷镁渣和自然冷镁渣,对比分析三种冷却速率镁渣物化性能后,得出改变出炉镁渣的冷却速率对镁渣物化性能的影响,并为制备可控膨胀性镁渣胶凝材料提供适合的冷却速率镁渣。然后采用适合的冷却速率镁渣与水泥在不同比例下分别制备了镁渣水泥胶凝料标准试块及膨胀试块,并通过物理性能检测,膨胀量测量,化学分析,XRD,SEM,压汞等方法对比研究不同配比下镁渣水泥胶凝料的物化性能及膨胀性,得到了以下结论:(1)改变冷却速率会影响镁渣中MgO的晶粒尺寸,自然冷镁渣中MgO晶粒尺寸为98.32nm;半急冷镁渣中MgO晶粒尺寸为10.534nm;急冷镁渣中MgO晶粒尺寸为3.04nm。因此,随着冷却速率加快,MgO晶粒尺寸迅速减小,活性增大,有益于MgO早期水化。在急冷镁渣与水泥制备的胶凝材料中,养护3d的衍射图中有MgO衍射峰的出现,但养护至28 d后,衍射图中已几乎不存在MgO衍射峰强。(2)随着冷却速率加快,镁渣的物化性能均有所改变,自然冷镁渣养护3d后基本未发生水化,抗压强度值仅为3.75MPa,养护至28d后水化程度依然不明显,抗压强度值为13MPa;而急冷镁渣养护3d后,抗压强度值为11.33 MPa,并且在SEM图像上可以观察到大部分颗粒表面均覆盖了一层薄薄的互连网状的C-S-H凝胶,养护28d后抗压强度值为21.7 MPa,其SEM图像上可以观察到C-S-H凝胶互相胶结的现象。(3)养护3d至28d过程中,自然冷镁渣的内部孔隙率由48.92%增加到67.72%,小孔占有的体积由55.95%下降到23.57%,最可几孔径尺寸几乎没有变化,约为91μm;半急冷镁渣的内部孔隙率由52.62%减小到42.63%,小孔所占体积由44.55%增加到67.53%,最可几孔径尺寸由91.25μm降至60.70μm;急冷镁渣的内部孔隙率由39.13%下降到31.32%,小孔所占体积由69.51%增加到97.27%,最可几孔径尺寸由60.75μm下降到0.83μm。(4)随着镁渣掺量的增加,急冷镁渣水泥胶凝材料的水化程度减弱,膨胀性能增强,当镁渣掺量为30%时,胶凝材料一直表现出负膨胀现象,并且养护200d内的负膨胀率最后稳定在1.08%,这说明胶凝材料依然存在很大的收缩行为;镁渣掺量为40%时,胶凝材料在养护200d内先负膨胀,后正膨胀,并且最后稳定在正膨胀0.12%,这表明胶凝材料的收缩行为被完全抵消了,且最终胶凝材料处于一种微膨胀状态;若将镁渣掺量继续增加到50%时,胶凝材料的压蒸安定性不合格。(5)随着镁渣掺量的增加,急冷镁渣水泥胶凝材料的抗压、抗折性能和密实度均降低,并且胶凝材料的孔隙率随着养护时间的增加也逐渐下降,养护3d至28d过程中,胶凝材料的内部孔径尺寸变化范围均在0~120μm内,其中,掺50%镁渣胶凝材料的孔隙率由32.39%减小到26.76%,最可几孔径尺寸由60.67μm减小到1.3μm,小孔所占体积由66.51%增加至94.82%;掺40%镁渣胶凝材料的孔隙率由28.48%减小至16.08%,最可几孔径尺寸由45.37μm减小到0.18μm,小孔所占体积63.67%增加至94.34%;掺30%镁渣的胶凝材料养护3d后孔隙率是最小的,为26.98%,最可几孔径尺寸为45.45μm,小孔所占体积在为70.58%,养护至28d后,孔隙率下降至16.64%,最可几孔径减小至0.18μm,小孔所占体积增加到93.85%。
[Abstract]:Magnesium slag is a solid waste produced in magnesium smelting. However, the activity of magnesium slag is low and the phenomenon of delayed expansion exists because of the natural cooling of magnesium slag. This has always been the key to restrict the application of magnesium slag. The slag is of great significance.After analyzing the conditions of producing magnesium slag and the mechanism of magnesium slag,this paper establishes a self-made small-scale cooling equipment to cool the magnesium slag from the furnace,and prepares magnesium slag with different cooling rates by controlling the air flow rate,which are quenched magnesium slag,semi-quenched magnesium slag and naturally cooled magnesium slag.The three cooling rates are compared and analyzed. After the physicochemical properties of magnesium slag were studied, the influence of cooling rate of magnesia slag on the physicochemical properties of magnesia slag was obtained, and the suitable cooling rate of magnesia slag was provided for the preparation of magnesia slag cementitious material with controllable expansibility. The physical and chemical properties and expansibility of magnesia slag cement cementitious materials with different ratios were studied by physical properties testing, expansion measurement, chemical analysis, XRD, SEM and mercury intrusion test. The following conclusions were obtained: (1) Changing the cooling rate will affect the grain size of MgO in magnesia slag, the grain size of MgO in natural cooled magnesia slag is 98.32 nm; The grain size of medium MgO is 10.534 nm and that of quenched MgO is 3.04 nm. Therefore, with the increase of cooling rate, the grain size of MgO decreases rapidly and the activity of MgO increases, which is beneficial to the early hydration of MgO. There is almost no MgO diffraction peak strength. (2) With the acceleration of cooling rate, the physical and chemical properties of magnesium slag have changed. The natural cold magnesium slag has not been hydrated after 3 days of curing, the compressive strength value is only 3.75 MPa, and the hydration degree is still not obvious after 28 days of curing, the compressive strength value is 13 MPa; but the compressive strength value is 11.33 MPa after 3 days of quenching magnesium slag curing. The surface of most particles was covered with a thin layer of interconnected C-S-H gel, and the compressive strength was 21.7 MPa after 28 days of curing. The phenomenon of C-S-H gel cementation could be observed on the SEM images. (3) The internal porosity of natural cold magnesium slag increased from 48.92% to 67.72% during 3 to 28 days of curing. The volume of the pores decreased from 55.95% to 23.57%, and the most probable pore size almost remained unchanged, about 91 micron; the internal porosity of the semi-quenched magnesium slag decreased from 52.62% to 42.63%, the volume of the pores increased from 44.55% to 67.53%, the most probable pore size decreased from 91.25 micron to 60.70 micron; and the internal porosity of the quenched magnesium slag decreased from 39.13% to 31.32 micron. (4) With the increase of magnesia slag content, the hydration degree of the quenched magnesia slag cement cementitious material decreases, and the expansion performance increases. When the magnesia slag content is 30%, the cementitious material always shows negative expansion phenomenon, and the negative expansion rate of the cured 200 days. At last, it stabilized at 1.08%, which indicated that the cementitious material still had a large shrinkage behavior; when the content of magnesium slag was 40%, the cementitious material expanded negatively, then positively, and finally stabilized at 0.12% of the positive expansion within 200 days of curing, which indicated that the shrinkage behavior of the cementitious material was completely offset, and the final cementitious material was in a micro-expansion state; (5) With the increase of magnesium slag content, the compressive strength, flexural strength and compactness of the quenched magnesium slag cement cementitious materials decrease, and the porosity of the cementitious materials decreases gradually with the increase of curing time. During the curing period from 3 to 28 days, the internal properties of the cementitious materials decrease. The pore size ranges from 0.39% to 26.76%, the most probable pore size decreases from 60.67 to 1.3 micron, the volume of small pore increases from 66.51% to 94.82%, the porosity of 40% magnesium slag cementitious material decreases from 28.48% to 16.08%, and the most probable pore size decreases from 45.37 micron. The porosity of the cementitious material with 30% magnesium slag is the smallest, 26.98%, the most probable pore size is 45.45 micron, the volume of the pore is 70.58%. After 28 days, the porosity decreases to 16.64%, the most probable pore diameter decreases to 0.18 micron, and the volume of the pore increases to 93.85%.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ177
本文编号：2214261
[Abstract]:Magnesium slag is a solid waste produced in magnesium smelting. However, the activity of magnesium slag is low and the phenomenon of delayed expansion exists because of the natural cooling of magnesium slag. This has always been the key to restrict the application of magnesium slag. The slag is of great significance.After analyzing the conditions of producing magnesium slag and the mechanism of magnesium slag,this paper establishes a self-made small-scale cooling equipment to cool the magnesium slag from the furnace,and prepares magnesium slag with different cooling rates by controlling the air flow rate,which are quenched magnesium slag,semi-quenched magnesium slag and naturally cooled magnesium slag.The three cooling rates are compared and analyzed. After the physicochemical properties of magnesium slag were studied, the influence of cooling rate of magnesia slag on the physicochemical properties of magnesia slag was obtained, and the suitable cooling rate of magnesia slag was provided for the preparation of magnesia slag cementitious material with controllable expansibility. The physical and chemical properties and expansibility of magnesia slag cement cementitious materials with different ratios were studied by physical properties testing, expansion measurement, chemical analysis, XRD, SEM and mercury intrusion test. The following conclusions were obtained: (1) Changing the cooling rate will affect the grain size of MgO in magnesia slag, the grain size of MgO in natural cooled magnesia slag is 98.32 nm; The grain size of medium MgO is 10.534 nm and that of quenched MgO is 3.04 nm. Therefore, with the increase of cooling rate, the grain size of MgO decreases rapidly and the activity of MgO increases, which is beneficial to the early hydration of MgO. There is almost no MgO diffraction peak strength. (2) With the acceleration of cooling rate, the physical and chemical properties of magnesium slag have changed. The natural cold magnesium slag has not been hydrated after 3 days of curing, the compressive strength value is only 3.75 MPa, and the hydration degree is still not obvious after 28 days of curing, the compressive strength value is 13 MPa; but the compressive strength value is 11.33 MPa after 3 days of quenching magnesium slag curing. The surface of most particles was covered with a thin layer of interconnected C-S-H gel, and the compressive strength was 21.7 MPa after 28 days of curing. The phenomenon of C-S-H gel cementation could be observed on the SEM images. (3) The internal porosity of natural cold magnesium slag increased from 48.92% to 67.72% during 3 to 28 days of curing. The volume of the pores decreased from 55.95% to 23.57%, and the most probable pore size almost remained unchanged, about 91 micron; the internal porosity of the semi-quenched magnesium slag decreased from 52.62% to 42.63%, the volume of the pores increased from 44.55% to 67.53%, the most probable pore size decreased from 91.25 micron to 60.70 micron; and the internal porosity of the quenched magnesium slag decreased from 39.13% to 31.32 micron. (4) With the increase of magnesia slag content, the hydration degree of the quenched magnesia slag cement cementitious material decreases, and the expansion performance increases. When the magnesia slag content is 30%, the cementitious material always shows negative expansion phenomenon, and the negative expansion rate of the cured 200 days. At last, it stabilized at 1.08%, which indicated that the cementitious material still had a large shrinkage behavior; when the content of magnesium slag was 40%, the cementitious material expanded negatively, then positively, and finally stabilized at 0.12% of the positive expansion within 200 days of curing, which indicated that the shrinkage behavior of the cementitious material was completely offset, and the final cementitious material was in a micro-expansion state; (5) With the increase of magnesium slag content, the compressive strength, flexural strength and compactness of the quenched magnesium slag cement cementitious materials decrease, and the porosity of the cementitious materials decreases gradually with the increase of curing time. During the curing period from 3 to 28 days, the internal properties of the cementitious materials decrease. The pore size ranges from 0.39% to 26.76%, the most probable pore size decreases from 60.67 to 1.3 micron, the volume of small pore increases from 66.51% to 94.82%, the porosity of 40% magnesium slag cementitious material decreases from 28.48% to 16.08%, and the most probable pore size decreases from 45.37 micron. The porosity of the cementitious material with 30% magnesium slag is the smallest, 26.98%, the most probable pore size is 45.45 micron, the volume of the pore is 70.58%. After 28 days, the porosity decreases to 16.64%, the most probable pore diameter decreases to 0.18 micron, and the volume of the pore increases to 93.85%.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ177
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