高温后聚丙烯纤维增强水泥基复合材料导热的多尺度方法

姚秀鹏; 韩阳; 沈雷; 朱德; 曹茂森

doi:10.13801/j.cnki.fhclxb.20201211.001

高温后聚丙烯纤维增强水泥基复合材料导热的多尺度方法

doi: 10.13801/j.cnki.fhclxb.20201211.001

姚秀鹏^1,,
韩阳^1, ,,
沈雷^2,,
朱德¹,
曹茂森²

1.
河南工业大学　土木工程学院，郑州 450001
2.
河海大学　力学与材料学院，南京 210098

基金项目: 纤维加强混凝土介观热-湿-力耦合离散模型与高温爆裂防治机理研究(2020T130170)；混凝土介观热-湿-力耦合离散模型与高温爆裂机理研究(51908195)

详细信息

通讯作者:
韩阳，博士，教授，博士生导师，研究方向为混凝土高温性能与损伤　 E-mail：hanyangh@126.com

中图分类号: TU528
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出版历程
- 收稿日期: 2020-10-26
- 录用日期: 2020-11-30
- 网络出版日期: 2020-12-14
- 刊出日期: 2021-10-01

Multi-scale method for thermal conductivity of polypropylene fiber reinforced cementitious composites after high temperature

YAO Xiupeng^1
,,
HAN Yang^{1
, ,},
SHEN Lei^2
,,
ZHU De¹,
CAO Maosen²

1.
School of Civil Engineering, Henan University of Technology, Zhengzhou 450001, China
2.
Department of Engineering Mechanics, Hohai University, Nanjing 210098, China

摘要

摘要: 有效导热系数(ETC)是预测火灾下混凝土结构内部温度时空分布的关键物性参数，为此提出了基于考虑界面热阻和粒子形状系数的改进Maxwell-Eucken模型的多相复合材料多尺度均质化方法，以预测高温后纤维增强水泥基复合材料的ETC。首先针对经历不同温度(20、60、150、300、450和600℃)处理后的砂浆、普通高性能混凝土和聚丙烯纤维增强混凝土开展了导热系数和孔隙率的测量试验，随后利用部分试验数据确定所提方法关键参数。最终利用所提方法预测经历不同温度处理后掺加不同含量和尺寸纤维的混凝土的ETC，方法预测结果与其余试验结果吻合良好。研究发现：粒子形状(纤维长度)对水泥基复合材料ETC的影响甚微；界面热阻(粒子与基体脱粘)对ETC的影响显著，界面热阻系数与经历温度呈线性增长关系；聚丙烯纤维熔化蒸发后干燥空气填充，形成管状裂缝热阻，同时柔软的细聚丙烯纤维在浇筑过程中附着在粗骨料表面，蒸发后进一步增加骨料与砂浆之间的界面热阻效应。
- 聚丙烯纤维 /
- 水泥基复合材料 /
- 高温 /
- 有效导热系数 /
- 裂缝热阻
Abstract: The effective thermal conductivity (ETC) is a key physical parameter for predicting the temperature distribution of concrete structure under fire. Responding to this demand, a multi-scale homogenization method based on the improved Maxwell-Eucken model, considering interfacial thermal resistance and random particle shape, was proposed to estimate the thermal conductivity of cementitious composites after high temperature. Firstly, the thermal conductivity and porosity of mortar, high performance concrete and polypropylene fiber reinforced concrete with thermal treatment at different temperatures (20, 60, 150, 300, 450 and 600℃) were measured and a part of experimental data was used to calibrate the proposed method. Finally, the method was verified by good agreement between experimental data and numerical results of concrete with different heating temperatures and different fiber contents and size. The results show that: The particle shape (fiber length) has a marginal effect on the ETC; The interfacial thermal resistance (ITR) caused by particle and matrix debonding has a significant effect on the ETC, and the ITR coefficient is in direct proportion to the heating temperature; The polypropylene fiber melts and evaporates at high temperature and then the ‘tunnel crack’ filled with dry air forms a thermal resistance. In addition, the melting and evaporation of soft fine polypropylene fiber adhering on the coarse aggregate surface enhances the ITR effect between aggregate and mortar.
- polypropylene fiber /
- cementitious composites /
- high temperature /
- effective thermal conductivity /
- thermal resistance cracks

HTML全文

图 1 聚丙烯纤维/混凝土(PF/concrete)经历高温后热开裂和纤维热熔示意图

Figure 1. Schematic diagram of thermal cracking and fiber melting of polypropylene fiber reinforced concrete (PF/concrete) after high temperature

MOR—Mortar; ITZ—Interfacial transition zone; Agg—Aggregate; PF—Polypropylene fiber

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图 2 常温下和经历400℃高温后PF/concrete的SEM图像^[19]

Figure 2. SEM images of polypropylene PF/concrete at room temperature and after 400℃^[19]

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图 3 PF/concrete多尺度方法流程图

Figure 3. Illustration of the multi-scale method for PF/concrete

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图 4 常温(20℃)下PF/concrete中PF附着在骨料上的SEM图像

Figure 4. SEM images of PF attached to aggregate in PF/concrete at room temperature (20℃)

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图 5 水泥砂浆有效导热系数(ETC)计算值

Figure 5. Results of effective thermal conductivity (ETC) of cement mortar

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图 6 普通高性能混凝土(HPC)有效导热系数计算值

Figure 6. Results of ETC of high performance concrete (HPC)

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图 7 四种PF/concrete的ETC计算值

Figure 7. Results of ETC of PF/concrete

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图 8 骨料和水泥砂浆之间界面热阻(ITR)对HPC的ETC的影响

Figure 8. Interfacial thermal resistance (ITR) effect on ETC of HPC

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图 9 骨料的形状系数对HPC的ETC的影响

Figure 9. Shape effect of aggregate on ETC of HPC

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图 10 水泥基复合材料ETC与温度的关系

Figure 10. Relationship between ETC and temperature of cementitious composites

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图 11 PF含量对PF/concrete的ETC的影响

Figure 11. Effect of PF content on ETC of PF/concrete

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表 1 水泥基复合材料配合比

Table 1. Mix in experiment of cementitious composites kg/m³

Material	MOR	HPC	0.1%PF_L12/HPC	0.2%PF_L6/HPC	0.2%PF_L12/HPC	0.2%PF_L19/HPC	Detail
Cement	500	500	500	500	500	500	Poland cement 42.5
Water	150	150	150	150	150	150	Ordinary tap water
Fine aggregate	713	713	713	713	713	713	Dried river sand; Diameter: 3-2.7 mm
Coarse aggregate	0	1027	1027	1027	1027	1027	Crushed limestone; Diameter: 5-20 mm
Admixture	13.5	13.5	13.5	13.5	13.5	13.5	Polycarboxylic acid
PF	0	0	0.91	1.82	1.82	1.82	Length:6,12,19 mm; Diameter: 18-48 μm
Notes: HPC—High performance concrete; 0.1%PF_L12/HPC, 0.2%PF_L6/HPC, 0.2%PF_L12/HPC and 0.2%PF_L19/HPC are different types of polypropylene fiber reinforced concretes, 0.1% and 0.2% represent the volume ratios of polypropylene fibers, PF—Polypropylene fiber; Letter L stands for fiber length, which are 6, 12 and 19 mm, respectively.

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表 2 水泥基复合材料试验结果

Table 2. Experimental data of cementitious composites

Mixture	T/℃	Porosity	ETC/ (W∙(m∙℃)⁻¹)
Mixture	T/℃	Porosity	Average	Max	Min
MOR	20	0.0237	1.258	1.350	1.125
	60	0.0237	1.225	1.299	1.083
	150	0.1000	1.023	1.205	0.963
	300	0.1737	0.896	0.951	0.834
	450	0.2194	0.741	0.771	0.719
	600	0.2637	0.676	0.731	0.653
HPC	20	0.0250	1.606	1.763	1.434
	60	0.0250	1.452	1.672	1.371
	150	0.0770	1.409	1.543	1.306
	300	0.1186	1.269	1.384	1.032
	450	0.1594	1.124	1.235	0.947
	600	0.1729	0.964	1.053	0.867
0.1%PF_L12/HPC	20	0.0149	1.599	1.695	1.470
	60	0.0149	1.414	1.630	1.323
	150	0.0802	1.341	1.425	1.284
	300	0.1132	1.230	1.386	1.160
	450	0.1514	1.045	1.175	0.924
	600	0.1713	0.908	1.003	0.841
0.2%PF_L6/HPC	20	0.0167	1.472	1.642	1.381
	60	0.0167	1.379	1.697	1.334
	150	0.0730	1.285	1.473	1.125
	300	0.1076	1.187	1.346	1.036
	450	0.1492	1.022	1.306	0.862
	600	0.1636	0.887	1.037	0.829
0.2%PF_L12/HPC	20	0.0200	1.585	1.680	1.470
	60	0.0200	1.391	1.602	1.235
	150	0.0907	1.255	1.489	1.177
	300	0.1105	1.191	1.350	1.055
	450	0.1399	1.011	1.156	1.000
	600	0.1842	0.877	0.963	0.735
0.2%PF_L19/HPC	20	0.0182	1.541	1.685	1.347
	60	0.0182	1.445	1.654	1.247
	150	0.0697	1.334	1.523	1.113
	300	0.1089	1.190	1.308	1.009
	450	0.1460	0.969	1.030	0.869
	600	0.1585	0.874	1.024	0.807
Notes: T—Temperature; ETC—Effective thermal conductivity.

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表 3 水泥基复合材料多尺度方法参数

Table 3. Parameters for multi-scale method of cementitious composites

	Temperature/℃	Matrix		Particles
	Temperature/℃	Material	${\lambda _{\rm{m}}}$/(m∙℃)⁻¹	Material	${\lambda _{\rm{p}}}$/(m∙℃)⁻¹	${V_{\rm{p}}}$	$n$	$\alpha $
Step1	20-600	Cement paste solid skeleton	0.56 Identified	Water dry air	0.6 0.026^[31-32]	Porosity measured	3 Assumed	0 Assumed
Step2	20-600	Cement paste	Calculated by Step1	Fine aggregate	3.1^[33]	0.43 mixture	3 Assumed	(0.21/600) T Identified
Step3	20-600	Mortar	Calculated by Step2	Coarse aggregate	2.4^[33]	0.386 mixture	3 Assumed	(0.27/600) T Identified
Step4	20-600	Plain concrete	Calculated by Step3	Polypropylene fiber	0.22^[34]	1% or 2% mixture	Details in the paper	Details in the paper
Notes: ${\lambda _{\rm{m}}}$—ETC of the matrix; ${\lambda _{\rm{p}}}$—ETC of the particles; ${V_{\rm{p}}}$—Volume fraction of the particles, $n$—Shape coefficient of the particles; $\alpha $—Interfacial thermal resistance coefficient between matrix and particles.

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