硅灰改性钢纤维增强地聚物再生混凝土力学性能试验

夏冬桃; 常闻捷; 李彪; 吴晨; 喻诗汀; 王煜; 高奥星

硅灰改性钢纤维增强地聚物再生混凝土力学性能试验

湖北工业大学　土木建筑与环境学院, 武汉 430068

基金项目: 国家自然科学基金项目 (52308248)；湖北省自然科学基金项目 (2023AFB309)

详细信息

通讯作者:
李彪，博士，副教授，硕士生导师，研究方向为结构工程与材料　E-mail: libiao@hbut.edu.cn

中图分类号: TU528
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- 文章访问数: 52
- HTML全文浏览量: 31
- 被引次数: 0
出版历程
- 收稿日期: 2024-05-14
- 修回日期: 2024-06-18
- 录用日期: 2024-07-10
- 网络出版日期: 2024-07-30

Experimental study on mechanical properties of silica fume modified steel fibre reinforced geopolymer recycled aggregate concrete

School of Civil Engineering, Architecture & The environment, Hubei University of Technology, Wuhan 430068, China

Funds: National Natural Science Foundation of China (NSFC) (52308248); the Natural Science Foundation of Hubei Province (2023AFB309)

摘要

摘要: 钢纤维增强地聚物再生混凝土(Steel fiber reinforced geopolymer recycled concrete, SFRGRAC)具有碳排放量低、节约天然矿物资源以及延性韧性好等优点，具有广泛应用前景。为改善SFRGRAC力学性能，本文以硅灰为增强材料，通过立方体抗压、劈裂抗拉、抗折和弹性模量试验，研究硅灰取代率、钢纤维体积掺量和再生骨料取代率等因素对SFRGRAC力学性能的影响规律，并基于SEM扫描电镜和低场核磁共振测试结果揭示硅灰的改性机制。结果表明：掺入硅灰可延长SFRGRAC的凝结时间，当硅灰取代率为15%时，初凝和终凝时间分别提高了29.68%和22.98%；由于硅灰与碱激发溶液快速发生发应，加快了水化反应的速度，SFRGRAC3d抗压强度和劈裂抗拉强度可达到28d强度的85%以上；随着钢纤维体积掺量从0%增至1.5%，其抗压强度可提高17.44%，随着再生骨料取代率从0%增至50%，其强度降低了9.79%。掺入10%硅灰，总孔隙率降低了37.38%，能显著提高其抗压、劈裂抗拉和抗折强度，但当硅灰掺量为15%时，因过量硅灰降低了基体的碱度，导致地聚物水化反应不完全，使其力学性能表现出下降趋势。研究成果为再生混凝土相关规范的修订和完善提供参考依据。
- 地聚物再生混凝土 /
- 钢纤维 /
- 硅灰 /
- 力学性能 /
- 改性机理
Abstract: Steel fiber reinforced geopolymer recycled concrete (SFRGRAC) presents several benefits, including reduced carbon emissions, conservation of natural minerals, and enhanced ductility and toughness, rendering it a promising material for broad applications. This study aims to augment the mechanical characteristics of SFRGRAC by incorporating silica fume as a reinforcing agent. It examines the influence of silica fume content, steel fiber volume fraction, and recycled aggregate substitution ratio on mechanical performance of SFRGRAC through cube compression, split tensile strength, flexural strength, and modulus of elasticity test. Additionally, the study elucidates the modification mechanism of silica fume via SEM and low field NMR test. The findings indicate that silica fume addition extends the setting time of SFRGRAC, with 15% substitution rate of silica fume leading to a 29.68% increase in initial setting time and a 22.98% increase in final setting time. The accelerated hydration reaction, prompted by the prompt pozzolanic reaction between silica fume and the alkali activator, results in the SFRGRAC achieving over 85% of its 28d compressive and tensile strengths within 3d. The compressive strength improves by 17.44% as steel fiber volume fraction increases from 0% to 1.5%, whereas a 50% substitution of recycled aggregate causes a 9.79% reduction in strength than 0% substitution rate. A 10% inclusion of silica fume diminishes total porosity by 37.38%, substantially enhancing compressive, tensile, and flexural strengths. When the silica fume substitution rate reaches 15%, the excessive silica fume reduces the alkalinity of matrix, resulting in an incomplete hydration reaction of the geopolymer. Consequently, this causes a decline in its mechanical properties. These findings offer valuable insights for the revision and enhancement of specifications related to recycled concrete.
- geopolymer recycled aggregate concrete /
- steel fiber /
- silica fume /
- mechanical properties /
- modification mechanism

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图 1 粗骨料和钢纤维

Figure 1. Coarse aggregate and steel fiber

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图 2 材料粒径累计分布图

Figure 2. Cumulative size distribution curve of raw materials

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图 3 硅灰掺量对SFRGRAC凝结时间的影响

Figure 3. Effect of silica fume content on the setting times of SFRGRAC

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图 4 SFRGRAC立方体抗压强度

Figure 4. Cubic compressive strength of SFRGRAC

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图 5 SFRGRAC劈裂抗拉强度

Figure 5. Splitting tensile strength of SFRGRAC

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图 6 SFRGRAC抗折强度

Figure 6. Flexural strength of SFRGRAC

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图 7 SFRGRAC弹性模量

Figure 7. Modulus of elasticity of SFRGRAC

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图 8 SFRGRAC的破坏形态

Figure 8. Typical failure surfaces of SFRGRAC

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图 9 不同硅灰取代率SFRGRAC的XRD图谱

Figure 9. XRD patterns of SFRGRAC with different contents of silica fume

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图 10 SFRGRAC孔隙分布

Figure 10. Pore size distribution of SFRGRAC

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图 11 SFRGRAC孔隙率与力学性能关系

Figure 11. Fitting relationship curve of porosity and mechanical characteristics of SFRGRAC

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图 12 硅灰改性SFRGRAC微观机理

Figure 12. Microscopic mechanism of silica fume modified SFRGRAC

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表 1 胶凝材料主要化学成分

Table 1. Chemical composition of cementitious materials

Binder	Compositions/%										Specific surface area/(cm²·g⁻¹)	Density/ (kg·m⁻³)
Binder	CaO	SiO₂	Al₂O₃	Fe₂O₃	MgO	SO₃	K₂O	Na₂O	MnO	TiO₂	Specific surface area/(cm²·g⁻¹)	Density/ (kg·m⁻³)
Slag	36.82	26.75	19.66	0.32	11.1	2.65	0.29	0.84	0.37	0.94	428	2.9
Silica fume	0.12	96.65	0.31	0.07	0.11	1.21	0.22	0.67	0.17	0.83	200000	2.1

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表 2 SFRGRAC设计配合比

Table 2. Designed mix proportions of SFRGRAC

No.	Specimen	Proportions/(kg·m⁻³)
No.	Specimen	Slag	Sand	Natural aggregate (NA)	Recycled aggregate (RA)	Silica fume	Steel fiber	Water	Sodium silicate	Sodium hydroxide	Plastisizer
1	R50F00S00	417	724	724	543	0	0	61.08	161.75	3.59	3.3
2	R50F00S05	396.15	724	724	543	20.85	0	66.77	168.68	12.08	3.3
3	R50F00S010	375.3	724	724	543	41.70	0	72.47	159.80	11.45	3.3
4	R50F00S15	354.45	724	724	543	62.55	0	78.17	150.93	10.81	3.3
5	R50F10S00	417	724	724	543	0	78.5	61.08	161.75	3.59	3.3
6	R50F05S10	375.3	724	724	543	41.7	39.25	72.47	159.8	11.45	3.3
7	R50F10S05	396.15	724	724	543	20.85	78.5	66.77	168.68	12.08	3.3
8	R50F10S10	375	724	724	543	41.7	78.5	72.47	159.8	11.45	3.3
9	R50F10S15	354.45	724	724	271.5	62.55	78.5	78.17	150.93	10.81	3.3
10	R25F10S10	375.3	724	724	271.5	41.7	78.5	72.47	159.8	11.45	3.3
11	R00F10S10	375.3	724	818	0	41.7	78.5	72.47	159.8	11.45	3.3
12	R50F15S10	375.3	724	626	543	41.7	117.75	72.47	159.8	11.45	3.3
Notes：R—Addition of recycled aggregate; F—Volume fraction of steel fiber; S—Addition of silica fume. R50F10S10represent the 50% recycled aggregate content, 1.0% steel fiber volume fraction and 10% silica fume content.

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表 3 SFRGRAC强度和弹性模量测试结果

Table 3. Test results of machine strength and elastic modulus of SFRGRAC

Specimen	Compressive strength/MPa			Splitting tensile strength/MPa			Flexural strength/MPa	Modulus of elasticity/GPa
Specimen	3d	7d	28d	3d	7d	28d	28d	28d
R50F00S00	38.07	43.05	47.51	3.39	3.71	4.16	3.79	13.02
R50F00S05	39.15	48.53	51.24	3.72	4.10	4.41	4.18	13.35
R50F00S10	41.36	48.60	53.96	3.91	4.27	4.32	4.26	14.75
R50F00S15	28.95	36.39	47.80	2.66	3.10	3.19	3.64	11.29
R50F10S00	40.30	48.44	54.05	3.98	4.42	4.91	4.30	13.85
R50F05S10	47.78	49.31	55.68	4.57	5.26	5.80	4.48	18.48
R50F10S05	49.15	53.75	57.25	5.54	5.91	6.26	4.83	16.43
R50F10S10	49.85	54.3	58.76	5.61	6.15	6.61	5.18	22.51
R50F10S15	40.75	46.93	55.91	5.00	5.51	6.16	4.06	14.22
R25F10S10	52.15	56.62	60.21	5.64	6.56	6.88	5.32	24.37
R00F10S10	55.91	61.27	65.14	6.16	7.01	7.24	5.68	27.52
R50F15S10	53.49	58.95	65.39	5.75	6.46	6.68	5.34	24.35

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表 4 混凝土基质中孔隙率的总体积分数

Table 4. Total volume fraction of porosity in the concrete matrix

Specimen	Curing age	Small pores (＜4μm)	Medium pores (4~6μm)	Large pores (≥10μm)	Total
R50F10S00	3d	3.15	0.29	0.61	4.05
R50F10S00	28d	2.31	0.08	0.94	3.32
R50F10S05	3d	3.06	0.12	0.72	3.91
R50F10S05	28d	2.11	0.06	0.61	2.78
R50F10S10	3d	3.13	0.061	0.86	4.06
R50F10S10	28d	2.07	0.08	0.37	2.53
R50F10S15	3d	4.01	0.38	0.80	5.19
R50F10S15	28d	2.71	0.12	0.88	3.71

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