基于分子动力学模拟的过硫磷石膏矿渣水泥组成设计

Composition design of excess-sulfate phosphogypsum slag cement based on molecular dynamics simulation

原材料化学成分的组成设计是过硫磷石膏矿渣水泥(PPSC)水化反应与力学强度形成的基础,室内试验与分子动力学模拟(MD)为PPSC原材料的化学组成提供了多尺度调控设计依据。利用Materials Studio(MS)软件建立PPSC结构模型,采用MD与XRD等手段研究了化学成分摩尔比对PPSC抗压强度的影响规律。结果表明:随着CaO/SO_(3)摩尔比的增加和SiO_(2)/Al_(2)O_(3)的降低,PPSC的抗压强度呈增长趋势,当SiO_(2)/Al_(2)O_(3)摩尔比为3.5~3.7、CaO/SO_(3)摩尔比为1.8~2.0时,PPSC的抗压强度较高。分子动力学对PPSC孔结构的模拟结果与抗压强度试验结果规律相反,证明了模拟结果的可靠性。在原子尺度上,分子动力学模拟表明O、Ca、Al及S原子表现出较高的扩散能力,在碱性环境下,硫酸盐激发作用使S=O、Al−O及O=O键长增大而结构失稳水解,生成较多对强度起促进作用的钙矾石。通过调控原材料SiO_(2)/Al_(2)O_(3)摩尔比和CaO/SO_(3)摩尔比可使PPSC形成更加稳定的内部结构。化学成分摩尔比设计及分子动力学模拟方法对PPSC的组成设计和应用推广具有重要意义。

Chemical composition design of raw materials is the basis of hydration reaction and mechanical strength formation of excess-sulfate phosphorgypsum slag cement(PPSC).Laboratory experiments and molecular dynamics simulation(MD)provide a multi-scale regulation and control design basis for chemical composition of PPSC raw materials.The structural model of the PPSC was established by Materials Studio(MS).The effect of the molar ratios of chemical components on the compressive strength of PPSC was studied by means of MD simulation and XRD.The results show that with the increase of the CaO/SO_(3)molar ratio and the decrease of SiO_(2)/Al_(2)O_(3),the compressive strength of PPSC shows an increasing trend.When the SiO_(2)/Al_(2)O_(3)molar ratio is 3.5-3.7 and the CaO/SO_(3)molar ratio is 1.8~2.0,the compressive strength of PPSC is higher.The MD simulation result of PPSC pore structure is contrary to the compressive strength test result,which proves the reliability of the simulation result.At the atomic scale,MD simulation shows that O,Ca,Al and S atoms exhibit high diffusion ability.In the alkaline environment,sulphate activation increases the bond length of S=O,Al−O and O=O,and the structure is unstable and hydrolyzed,resulting in more ettringite that promotes strength.By adjusting the raw materials SiO_(2)/Al_(2)O_(3)molar ratio and CaO/SO_(3)molar ratio,PPSC can form a more stable internal structure.The design of chemical composition molar ratio and MD simulation methods are of great significance for the composition design and application promotion of PPSC.