水化硅酸钙力学性能的分子动力学模拟研究

发布时间：2018-02-12 09:42

本文关键词： 水化硅酸钙分子动力学温度钙硅比冲击力学性能　出处：《太原理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：水泥广泛应用于土木工程中,与此同时,水泥基材料的浪费和对环境的破坏也极为严重。对水泥浆的主要强度成分——水化硅酸钙(C-S-H)进行研究,有利于从本质上了解水泥基材料的强度机理和断裂破坏特性。随着模拟技术和计算机技术的发展,研究材料的尺度已经从宏观扩展到微观,从微观到纳米尺度,分子模拟技术的应用在揭示和预测材料的力学性能具有重要的实际意义。本论文在总结前人建模过程的基础上,重新构建了无定型C-S-H原子模型,并在此基础上开展了C-S-H力学性能的分子动力学模拟研究。首先,研究了温度对C-S-H层状方向拉压力学性能的影响。结果表明:随着温度的增加,C-S-H的抗拉强度显著减小,杨氏模量也随着温度的增加而下降;水层是影响C-S-H抗拉强度的一个重要因素,使得C-S-H抗拉强度明显小于抗压强度。其次,研究了在轴向载荷作用下钙硅比(C/S)对C-S-H力学性能的影响。当C-S-H的硅链以完整形态存在时,C-S-H的应力峰值最大,具有较好的抗拉力学性能;当C/S1.0时,游离的钙原子在缺陷处形成钙-氧相互作用,一定程度上能够弥补Si O2缺失对体系造成的不利影响,起到桥接硅链的作用,从而使得C-S-H的抗拉强度不再随着C/S的增大而明显下降;当C-S-H体系中存在水分子时,水分子的大量存在削弱了钙-氧间的相互作用,使得C-S-H的强度降低,尤其是z方向上的抗拉强度,并且甚至可能改变C-S-H的失效模式。最后,研究了C-S-H在冲击载荷下的动态力学响应。通过分子动力学模拟,得到了冲击雨贡钮曲线及质点速度分布图。模拟结果发现,冲击压缩载荷可引起C-S-H的弹性、弹塑性及冲击机制,其雨贡钮弹性极限约为7.5GPa。当质点速度小于0.5km/s时,C-S-H处于弹性状态,只有弹性波形成,且该弹性波属于连续波;当质点速度约为0.5km/s时,C-S-H开始屈服,一个新的波开始形成;当质点速度在0.5km/s和2.0km/s之间时,一个由弹性前驱波和后继塑性波组成的双波结构形成,且弹性区的范围在扩大;当质点速度超过2.0km/s时,相转变波占主导地位。这些结果为了解C-S-H在层状方向上的冲击行为提供了重要的基础。
[Abstract]:Cement is widely used in civil engineering. At the same time, the waste of cement-based materials and the damage to the environment are also very serious. The main strength component of cement slurry, calcium silicate Hydrate (C-S-H), is studied. With the development of simulation technology and computer technology, the scale of research materials has expanded from macro to micro, from micro to nano scale. The application of molecular simulation technology is of great practical significance in revealing and predicting the mechanical properties of materials. Based on the previous modeling process, an amorphous C-S-H atomic model is constructed in this paper. On this basis, the molecular dynamics simulation of C-S-H mechanical properties has been carried out. Firstly, the effect of temperature on the tensile and compressive properties of C-S-H layered direction has been studied. The results show that the tensile strength of C-S-H decreases significantly with the increase of temperature. The Young's modulus also decreases with the increase of temperature, and the water layer is an important factor affecting the tensile strength of C-S-H, which makes the tensile strength of C-S-H obviously smaller than the compressive strength. The effect of Ca / S ratio C / S on the mechanical properties of C-S-H was studied under axial loading. When the silicon chain of C-S-H existed as a complete form, the stress peak value of C-S-H was the largest and had better tensile mechanical properties. The free calcium atom forms the calcium-oxygen interaction at the defect, to some extent, it can make up the negative effect of the Sio _ 2 deficiency on the system and bridge the silicon chain. As a result, the tensile strength of C-S-H no longer decreases with the increase of C / S, and when there are water molecules in the C-S-H system, the existence of a large number of water molecules weakens the interaction between calcium and oxygen, which decreases the strength of C-S-H. In particular, the tensile strength in the z direction may even change the failure mode of C-S-H. Finally, the dynamic mechanical response of C-S-H under impact load is studied. The curve of impingement Yugong knob and the distribution diagram of particle velocity are obtained. The simulation results show that the elastic, elastic-plastic and impact mechanism of C-S-H can be induced by the impact compression load, and the elastic limit of the impingement knob is about 7.5 GPa.When the particle velocity is less than 0.5 km / s, the C-S-H is in an elastic state. Only elastic waves are formed, and the elastic waves are continuous waves; when the particle velocity is about 0.5 km / s, the C-S-H begins to yield and a new wave begins to form; when the particle velocity is between 0.5 km / s and 2.0 km / s, A two-wave structure consisting of elastic precursors and subsequent plastic waves is formed, and the elastic region is expanding; when the particle velocity exceeds 2.0 km / s, These results provide an important basis for understanding the impact behavior of C-S-H in the stratiform direction.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ172.1

【参考文献】