不同温度下水化硅酸钙复合材料力学性能的分子动力学研究

发布时间：2018-01-30 04:53

本文关键词： C-S-H复合材料分子动力学力学性能孔隙率温度　出处：《深圳大学》2017年硕士论文　论文类型：学位论文

【摘要】：目前水泥水化研究者们提出了很多水泥水化单粒模型和水泥水化模型来揭示水泥水化机理,但均没有基于分子动力学理论的支撑。水泥水化主要产物是水化硅酸钙,其力学性能及发展机理仍没有统一的结论。在众多从分子动力学角度进行水化硅酸钙力学性能的研究中,不同学者选用的模拟系综和控压方法不尽相同,系综和控压方法对水化硅酸钙力学性能的影响也尚不明确。高温下混凝土的力学性能严重下降,在众多影响因素中,温度对水化硅酸钙力学性能的影响不容忽视。加之,由于水化硅酸钙中Tobermorite9?、Tobermorite 11?、Tobermorite 14?和Jennite四种晶体所占的比例并不确定,导致C-S-H复合材料的力学性能不能直接通过这四种晶体的力学性能推出,这就需要对考虑孔隙率的情况下将这四种晶体按照不同的比例进行分组来分析C-S-H复合材料的力学性能。因此,有必要对常温下C-S-H复合材料力学性能展开研究,同时,不同温度下不同系综对C-S-H复合材料力学性能影响的也迫切需要研究。为建立水泥水化模型提供一定的参考价值和理论依据。本文对不同温度下C-S-H复合材料的力学性能进行分子动力学模拟研究,同时考虑C-S-H凝胶中不同晶体所占比例、孔隙率和温度对C-S-H复合材料力学性能的影响,以Tobermorite 9?、Tobermorite 11?、Tobermorite 14?和Jennite晶体为基础,采用Materials Studio软件建立结构模型,进行结构优化,在常温下分子动力学弛豫,求解力学参数。按照23组4种晶体在水化硅酸钙中不同比例来分析这4种晶体所占比例对水化硅酸钙凝胶复合材料力学性能的影响,并利用SC方法、MT方法和Voigt上限值法等细观力学方法研究了C-S-H复合材料在不同比例组分的情况下力学参数。考虑到孔隙率的作用,分别对高浓度和低浓度的C-S-H微多孔介质的力学性能进行研究,使之与C-S-H的真实情况更加接近,并将计算结果与纳米压痕试验结果进行对比后发现,在一定范围内,C-S-H复合材料的力学性能随着其孔隙率和成分的变化而波动。同时,还发现各项力学性能的变化趋势与是否考虑孔隙率的影响无关;C-S-H复合材料的不同力学参数随着晶体成分比例和孔隙率的变化规律不同。以前面的初始结构模型为基础,对晶体结构的3a×3b×3c超胞模型进行结构优化,选用NVT和NPT系综分别在25℃、80℃以及200℃~1500℃每隔100℃设置一个温度点进行动力学弛豫,求解晶体力学参数,分析分子间相互作用、晶体晶胞参数的变化和在不同温度下四种晶体的力学性能。采用SC方法、MT方法和Voigt上限值法,分析五个代表性温度下四种晶体成分比例和孔隙率对C-S-H复合材料力学性能的影响,得到了三种分析方法结果间的关系和C-S-H复合材料力学性能随温度的变化趋势。通过分析两个系综结果间的差异后发现,C-S-H复合材料的体积模量、剪切模量和杨氏模量等参数随着温度的升高而变小,而泊松比随着温度的升高却略微增大。在NPT和NVT两种系综下,同种晶体的力学参数随温度变化趋势基本一致,但是数值相差较大,系综对C-S-H复合材料力学性能的影响较大。考虑孔隙率的影响时,SC方法和MT方法所得到的结果与Voigt上限值法的结果间存在一定的比例关系。
[Abstract]:At present, the study of cement hydration have proposed many cement hydration model of single particle and cement hydration model to reveal the mechanism of cement hydration, but did not support the theory of molecular dynamics based on cement hydration are the main products of calcium silicate hydrate, its mechanical properties and development mechanism is still no unified conclusion. The Research of silicate the mechanical properties of hydrated calcium from the view of molecular dynamics in the ensemble simulation, different scholars use and pressure control methods vary, ensemble and control effect of calcium silicate pressure method mechanical properties of water are not clear. The mechanical properties of concrete under high temperature declined seriously, there are many factors, the effect of temperature on the mechanical properties of hydrated calcium silicate can not be ignored. In addition, due to the hydration of calcium silicate in Tobermorite9? Tobermorite, 11? Tobermorite, 14? Jennite and four kinds of crystal proportion is uncertain, resulting in C-S-H The mechanical properties of composite materials cannot be directly through the introduction of mechanical properties of the four kinds of crystals, it is necessary to consider the case of porosity of the four crystals were grouped according to the different proportion of mechanical properties of C-S-H composites. Therefore, it is necessary to conduct research on the mechanical properties of C-S-H Composites at room temperature at the same time, influence in different lines of different temperatures on mechanical properties of C-S-H composites is also an urgent need to study. To provide some reference value and theoretical basis for the establishment of cement hydration model. The C-S-H composite materials under different temperature and mechanical properties of molecular dynamics simulation study, considering the C-S-H gel in different crystal proportion, the effect of porosity and temperature on the mechanical properties of C-S-H composites, Tobermorite 9? Tobermorite, 11? Tobermorite, 14? Jennite and crystal based, by Materials Stu Dio software to establish the structural model, structure optimization, relaxation in molecular dynamics under normal temperature Henan, solving mechanics parameters. According to the 23 group of 4 kinds of crystals in the hydration of calcium silicate in different proportion to the analysis of the 4 kinds of crystals for influence on the hydration ratio of calcium silicate gel mechanical properties of composite materials, and using the SC method, MT method and Voigt method etc. upper limit of mechanical parameters of micromechanical methods of C-S-H composites with different proportion of components. Considering the porosity effect, were studied on the mechanical properties of micro porous medium with high concentration and low concentration of C-S-H, the real situation and C-S-H closer, and the calculation the nano indentation test results, in a certain range, the mechanical properties of C-S-H composite materials fluctuate with the porosity and composition. At the same time, also found that the changing trend of the mechanical properties of the Regardless of whether consider the effect of the porosity; different mechanical parameters of C-S-H composites with the variation of crystal composition and porosity. In different initial structure in front of the model based on the crystal structure of 3A * 3B * 3C super cell model was used to optimize the structure, using NVT and NPT ensemble respectively at 25 degrees, set a a temperature of 80 DEG C and 200 DEG ~1500 DEG C every 100 dynamic relaxation, solving crystal mechanical parameters, analysis of interaction between molecules, the change of mechanical properties of crystal lattice parameters and at different temperatures of four kinds of crystal. By using SC method, MT method and Voigt value method of limit analysis of four five a representative temperature crystal composition and porosity on the mechanical properties of C-S-H composites, the mechanical properties of C-S-H composites and the relationship between the three methods of analysis between the variation with temperature. Through the analysis of two The difference between the results of ensemble and found that the bulk modulus of C-S-H composites, shear modulus and Young's modulus with temperature increases, while the Poisson's ratio with the increase of temperature is slightly increased. In NPT and NVT two kinds of ensemble, the same trend with the mechanical parameters of the crystal temperature changes consistent, but the numerical difference, the ensemble effect on mechanical properties of C-S-H composites greatly. Considering the effect of the porosity, there is a certain proportion of the value of SC and MT methods the results obtained with the Voigt limit between the results.

【学位授予单位】：深圳大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528

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