本文關(guān)鍵詞： 水化硅酸鈣 分子動力學 溫度 鈣硅比 沖擊 力學性能　出處：《太原理工大學》2017年碩士論文　論文類型：學位論文

【摘要】：水泥廣泛應(yīng)用于土木工程中,與此同時,水泥基材料的浪費和對環(huán)境的破壞也極為嚴重。對水泥漿的主要強度成分——水化硅酸鈣(C-S-H)進行研究,有利于從本質(zhì)上了解水泥基材料的強度機理和斷裂破壞特性。隨著模擬技術(shù)和計算機技術(shù)的發(fā)展,研究材料的尺度已經(jīng)從宏觀擴展到微觀,從微觀到納米尺度,分子模擬技術(shù)的應(yīng)用在揭示和預測材料的力學性能具有重要的實際意義。本論文在總結(jié)前人建模過程的基礎(chǔ)上,重新構(gòu)建了無定型C-S-H原子模型,并在此基礎(chǔ)上開展了C-S-H力學性能的分子動力學模擬研究。首先,研究了溫度對C-S-H層狀方向拉壓力學性能的影響。結(jié)果表明:隨著溫度的增加,C-S-H的抗拉強度顯著減小,楊氏模量也隨著溫度的增加而下降;水層是影響C-S-H抗拉強度的一個重要因素,使得C-S-H抗拉強度明顯小于抗壓強度。其次,研究了在軸向載荷作用下鈣硅比(C/S)對C-S-H力學性能的影響。當C-S-H的硅鏈以完整形態(tài)存在時,C-S-H的應(yīng)力峰值最大,具有較好的抗拉力學性能;當C/S1.0時,游離的鈣原子在缺陷處形成鈣-氧相互作用,一定程度上能夠彌補Si O2缺失對體系造成的不利影響,起到橋接硅鏈的作用,從而使得C-S-H的抗拉強度不再隨著C/S的增大而明顯下降;當C-S-H體系中存在水分子時,水分子的大量存在削弱了鈣-氧間的相互作用,使得C-S-H的強度降低,尤其是z方向上的抗拉強度,并且甚至可能改變C-S-H的失效模式。最后,研究了C-S-H在沖擊載荷下的動態(tài)力學響應(yīng)。通過分子動力學模擬,得到了沖擊雨貢鈕曲線及質(zhì)點速度分布圖。模擬結(jié)果發(fā)現(xiàn),沖擊壓縮載荷可引起C-S-H的彈性、彈塑性及沖擊機制,其雨貢鈕彈性極限約為7.5GPa。當質(zhì)點速度小于0.5km/s時,C-S-H處于彈性狀態(tài),只有彈性波形成,且該彈性波屬于連續(xù)波;當質(zhì)點速度約為0.5km/s時,C-S-H開始屈服,一個新的波開始形成;當質(zhì)點速度在0.5km/s和2.0km/s之間時,一個由彈性前驅(qū)波和后繼塑性波組成的雙波結(jié)構(gòu)形成,且彈性區(qū)的范圍在擴大;當質(zhì)點速度超過2.0km/s時,相轉(zhuǎn)變波占主導地位。這些結(jié)果為了解C-S-H在層狀方向上的沖擊行為提供了重要的基礎(chǔ)。
[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.
【學位授予單位】：太原理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TQ172.1

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本文編號：1505336