基于分子动力学模拟的过硫磷石膏矿渣水泥组成设计

徐方; 李恒; 孙涛; 水中和; 丁超

doi:10.13801/j.cnki.fhclxb.20210816.005

基于分子动力学模拟的过硫磷石膏矿渣水泥组成设计

doi: 10.13801/j.cnki.fhclxb.20210816.005

徐方^1,,
李恒¹,
孙涛^2, ,,
水中和²,
丁超²

1.
中国地质大学(武汉)　工程学院，武汉 430074
2.
武汉理工大学　硅酸盐建筑材料国家重点实验室，武汉 430070

基金项目: 2020年度中山市第三批科技发展专项资金资助项目(2020-18)；中山市武汉理工大学先进工程技术研究院科研项目(WUT202011)；湖北省交通运输厅科技项目(2020-2-1-10)

详细信息

通讯作者:
孙涛，博士，副研究员，研究方向为水泥与混凝土　 E-mail：sunt@whut.edu.cn

中图分类号: TU528
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出版历程
- 收稿日期: 2021-05-17
- 修回日期: 2021-07-29
- 录用日期: 2021-07-30
- 网络出版日期: 2021-08-17
- 刊出日期: 2022-06-01

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

XU Fang^1
,,
LI Heng¹,
SUN Tao^{2
, ,},
SHUI Zhonghe²,
DING Chao²

1.
Faculty of Engineering, China University of Geosciences, Wuhan 430074, China
2.
State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, China

摘要

摘要: 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/SO₃摩尔比的增加和SiO₂/Al₂O₃的降低，PPSC的抗压强度呈增长趋势，当SiO₂/Al₂O₃摩尔比为3.5~3.7、CaO/SO₃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SiO₂/Al₂O₃摩尔比和CaO/SO₃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。
- 过硫磷石膏矿渣水泥 /
- 分子动力学模拟 /
- 摩尔比 /
- 化学成分 /
- 抗压强度
Abstract: 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/SO₃ molar ratio and the decrease of SiO₂/Al₂O₃, the compressive strength of PPSC shows an increasing trend. When the SiO₂/Al₂O₃ molar ratio is 3.5-3.7 and the CaO/SO₃ 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 SiO₂/Al₂O₃ molar ratio and CaO/SO₃ 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.
- excess-sulfate phosphogypsum slag cement /
- molecular dynamics simulation /
- molar ratio /
- chemical components /
- compressive strength

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图 1 过硫磷石膏矿渣水泥(PPSC)制备流程图

Figure 1. Flow chart of preparation of excess-sulfate phosphogypsum slag cement (PPSC)

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图 2 PPSC抗压强度

Figure 2. Compressive strength of PPSC

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图 3 PPSC模型基本单元 (a) 和最终模型 (b)

Figure 3. Basic unit of PPSC model (a) and final models (b) of PPSC

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图 4 PPSC的XRD图谱

Figure 4. XRD pattens of PPSC

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图 5 PPSC模型总径向分布函数

Figure 5. Total radial distribution function of PPSC models

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图 6 PPSC模型各原子键的径向分布函数

Figure 6. Radial distribution function of each atomic bond in PPSC models

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图 7 PPSC模型原子表面积和孔结构分布

Figure 7. Distribution of atomic surface and pore structure of PPSC models

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图 8 PPSC模型原子表面积和孔结构体积

Figure 8. Atomic surface area and pore volume of PPSC models

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图 9 PPSC模型中各原子扩散系数

Figure 9. Diffusion coefficient of each atom in PPSC models

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表 1 磷石膏(PG)、水泥和矿粉(GGBS)的化学组成

Table 1. Chemical compositions of phosphogypsum (PG), cement and granulated blast furnace slag powder (GGBS) wt%

Composition	SiO₂	Al₂O₃	SO₃	CaO	MgO	Fe₂O₃	TiO₂	P₂O₅	Loss
PG	2.26	0.40	49.38	38.89	0.06	0.38	0.35	0.43	7.71
Cement	19.14	5.11	4.42	59.03	1.96	3.74	0.33	−	5.52
GGBS	34.74	16.45	3.62	33.55	6.42	1.77	1.75	−	1.64

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表 2 PPSC配合比设计

Table 2. Mix design of PPSC

Sample	Mass fraction/wt%			Molar ratio
Sample	PG	GGBS	Cement	SiO₂/Al₂O₃	CaO/SO₃
P70G25C5	70	25	5	3.5	1.6
P60G35C5	60	35	5	3.5	1.8
P50G45C5	50	45	5	3.5	2.0
P70G20C10	70	20	10	3.7	1.6
P60G30C10	60	30	10	3.7	1.8
P50G40C10	50	40	10	3.7	2.0
P70G15C15	70	15	15	3.9	1.6
P60G25C15	60	25	15	3.9	1.8
P50G35C15	50	35	15	3.9	2.0
Notes: P—Phosphogypsum; G—Granulated blast furnace slag powder; C—Cement. The number after the letter indicates the percentage content; Abbreviations in this table do not contradict other abbreviations in this paper.

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表 3 PPSC分子动力学模型中基本单元个数

Table 3. Number of basic units in PPSC molecular dynamics models

Sample	Si/Al	Ca/S	Ca	SO₃	H₂O	SiAlO₇	Si₂AlO₁₀
P50G45C5	1.75	2.0	86	43	86	5	15
P70G20C10	1.85	1.6	180	112	224	3	17
P50G40C10	1.85	2.0	92	46	92	3	17
Note: Si/Al and Ca/S—Ratio of atomic amount.

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表 4 PPSC模型中各原子键键长

Table 4. Bond length of each atomic bond in PPSC models nm

Sample	Si/Al	Ca/S	Ca—O	Al—O	Si—O	S=O	H—O	O=O
P50G45C5	1.75	2.0	0.221	0.167	0.165	0.163	0.095	0.271
P70G20C10	1.85	1.6	0.221	0.169	0.167	0.143	0.097	0.247
P50G40C10	1.85	2.0	0.221	0.219	0.167	0.163	0.097	0.271
Reference	−	−	0.251	0.163	0.159	−	0.097	0.269-0.271

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