【作者】 刘畅；

【导师】 刘军；

【作者基本信息】 沈阳建筑大学 ， 材料工程（专业学位）， 2019， 硕士

【摘要】 磷酸镁水泥(MPC)具有早强、快硬、粘结性好的特点,是一种应用广泛的快速修补材料。但其突出的脆性问题也在一定程度上制约着材料的推广与应用。本文借鉴纤维增强混凝土的韧性研究,采用玻璃纤维改善磷酸镁水泥的力学性能,包括抗压、抗折以及韧性性能。玻璃纤维具有弹性模量高、抗拉强度好、耐碱腐蚀等特点,曾在增强混凝土材料中推广应用。研究镁磷比(M/P),水灰比(W/C)以及不同烧结温度下的氧化镁对MPC力学性能的影响;在此基础上采用玻璃纤维增韧改性MPC水泥,研究玻璃纤维预处理方式、掺量、长度对MPC的力学性能的影响;并结合XRD和SEM分析研究玻璃纤维对MPC水泥的表观形貌及水化产物的影响。主要研究内容如下:首先,研究了不同烧结温度下的氧化镁、不同的镁磷比、不同的水胶比对磷酸镁水泥流动性能及抗压抗折强度的影响的影响。研究结果表明,与1400℃烧结温度下的氧化镁相比,采用1800℃烧结温度下的氧化镁制备的磷酸镁水泥放热量低,水化速率合适,并且可以获得较高的抗压、抗折强度。镁磷比是4:1,水胶比是0.16时,制备的磷酸镁水泥具有较好的流动性能,可以达到270mm,并且磷酸镁水泥可以获得较好抗压、抗折强度。其次,研究了玻璃纤维对磷酸镁水泥的抗压、抗折强度及韧性性能的影响方式,采用不同掺量、长度及经过表面预处理前后下的玻璃纤维。研究结果表明,掺入玻璃纤维可有效提高磷酸镁水泥的力学性能及韧性性能,并且随着纤维掺量的提高,磷酸镁水泥的力学性能及韧性性能也随之得到改善。但由于玻璃纤维自身表面光滑的原因,在胶凝材料的内部粘结性能相对较差,受力过程中容易因脱粘拔出,而削弱纤维增韧的效果,而经过预处理后,玻璃纤维与磷酸镁水泥之间的粘结性能有明显的提升,力学性能及韧性性能都可以提高30%左右。最后,研究磷酸镁水泥的微观形貌,采用XRD和SEM,表征玻璃纤维对MPC水的表观形貌及水化产物的影响。研究结果表明,磷酸镁水泥中的主要水化产物是KMgPO4·6H2O,以及未水化的MgO和SiO2,经过硅烷偶联剂改性的纤维不会对MPC水化产物产生明显影响。同时,经过表面改性预处理的玻璃纤维,从磷酸镁水泥中拔出后表面粘结的胶凝材料的颗粒较多,而未进行改性的玻璃纤维表面则比较光滑干净,经过改性预处理后的玻璃纤维与此胶凝材料间具有更好的胶结性能。更多还原

【Abstract】 Magnesium phosphate cement(MPC)has the characteristics of early strength,fast hardness and good adhesion.But its outstanding brittleness also restricts the popularization and application of materials to a certain extent.In this paper,the mechanical properties of magnesium phosphate cement,including compressive strength,flexural strength and ductility,are improved by using glass fiber for reference.Glass fiber has the characteristics of high elastic modulus,good tensile strength and alkali corrosion resistance.The effects of magnesium to phosphorus ratio(M/P),water to cement ratio(w/c)and magnesium oxide at different sintering temperatures on the mechanical properties of MPC were studied.Glass fiber toughened MPC cement was used to study the influence of glass fiber pretreatment,content and length on the mechanical properties of MPC.Combined with XRD and SEM,the effects of glass fiber on the apparent morphology and hydration products of MPC cement were studied.The main research contents are as follows:Firstly,the effects of different sintering temperatures on the flow properties and compressive and flexural strength of magnesium phosphate cement were studied.The research results show that compared with 1400 0C sintering temperature of magnesium oxide,with 1800 ℃ sintering temperature of the preparation of magnesium oxide magnesium phosphate cement quantity of heat low,hydration rate,and can obtain high compressive strength,bending strength.When the ratio of magnesium to phosphorus is 4:1 and the ratio of water to binder is 0.16,the prepared magnesium phosphate cement has better flow performance,reaching 270mm.In addition,magnesium phosphate cement can obtain better compressive strength and flexural strength.Secondly,the influence of glass fiber on the compressive strength,flexural strength and ductility of magnesium phosphate cement was studied.Glass fiber was used before and after surface pretreatment with different content and length.The results show that adding glass fiber can effectively improve the mechanical properties and toughness of magnesium phosphate cement,and with the increase of fiber content,the mechanical properties and toughness of magnesium phosphate cement are also improved.But because of smooth surface glass fiber itself,in the interior of the gelled material bonding performance is relatively poor,the stress in the process of easy for debonding pulled up,and weaken the toughening effect of fiber,and after pretreatment,the bond performance between glass fiber and magnesium phosphate cement has obvious improvement,mechanical properties and toughness propertiescan be improved by about 30%.Finally,the microstructure of magnesium phosphate cement was studied,and the influence of glass fiber on the apparent structure and hydration products of MPC water was characterized by XRD and SEM.The results show that the main hydration products of magnesium phosphate cement are KMgPO4·6H2O,as well as unhydrated MgO and SiO2.The fiber modified by silane coupling agent will not have a significant impact on the hydration products of MPC.At the same time,the surface of the glass fiber after modified pretreatment,pulled out from magnesium phosphate cement after the surface of the cementitious material more particles,while the surface of the unmodified glass fiber is relatively smooth and clean,after modified pretreatment of the glass fiber and this cementitious material has better cementitious properties.更多还原