NaHCO<sub>3</sub>碳化后再生骨料混凝土早期力学性能试验研究

但宇; 梁莹; 许瑞天; 宁璠; 陈宗平

NaHCO₃碳化后再生骨料混凝土早期力学性能试验研究

但宇¹,
梁莹¹,
许瑞天²,
宁璠³,
陈宗平^{1, 2, ,}

1.
南宁学院　土木与建筑工程学院, 南宁 530200
2.
广西大学　土木建筑工程学院, 南宁 530004
3.
广西职业师范学院土木建筑工程学院, 南宁 530007

基金项目: 国家自然科学基金(51578163)、中央引导地方科技发展资金项目(桂科ZY21195010)、八桂学者专项研究经费项目([2019]79号)、广西科技基地与人才专项(桂科AD21075031)、广西重点研发计划项目(桂科AB21220012)、广西大学对口支援学科建设项目(2023N01)、广西研究生教育创新计划资助项目(YCBZ2024039)。

详细信息

通讯作者:
陈宗平，博士，教授，博士生导师，研究方向为再生混凝土材料及结构的力学性能　E-mail: zpchen@gxu.edu.cn

中图分类号: TU528.59；TB332
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- 被引次数: 0
出版历程
- 收稿日期: 2024-07-01
- 修回日期: 2024-08-13
- 录用日期: 2024-08-23
- 网络出版日期: 2024-09-06

Experimental Study on Early Mechanical Properties of Recycled Aggregate Concrete after NaHCO₃ Carbonation

1.
School of Civil and Architectural Engineering, Nanning University, Nanning 530200, China
2.
School of Civil and Architectural Engineering, Guangxi University, Nanning 530004, China
3.
School of Civil and Architectural Engineering, Guangxi Vocational Normal University, Nanning 530007, China

Funds: National Natural Science Foundation of China (No.51578163); Central guidance for local scientific and technological development funding projects (ZY21195010); Eight Gui Scholars Special Research Fund Project ([2019]79); Guangxi Science and Technology Base and Talent Special Project (AD21075031), Guangxi Key R&D Program Project (AB21220012); Counterpart Aid Project for Discipline Construction from Guangxi University (Grant No.2023N01); Innovation Project of Guangxi Graduate Education (YCBZ2024039).

摘要

摘要: 为提高再生骨料混凝土(Recycled Aggregate Concrete，RAC)的固碳效率和力学性能，采用碳酸氢钠(NaHCO₃)溶液对RAC进行浸泡养护和加速碳化，进行了立方体、棱柱体抗压试验和四点抗折试验，研究了三种碳化环境(自然碳化、碳化箱碳化、NaHCO₃溶液碳化)和碳化龄期(3~28 d)对RAC早期力学性能的影响。结果表明，相较于自然养护，NaHCO₃溶液碳化环境最大可以提高RAC的8.4%的早期抗压强度和12.4%的抗折强度，但会提高脆性；在21 d之前，NaHCO₃溶液碳化后的RAC的早期抗压强度和强度发展略低于碳化箱碳化环境，但在28d时显著提高；碳化龄期对RAC的抗折强度影响不大，但在相同龄期时，NaHCO₃溶液碳化后的抗折强度最高。通过热重分析发现，NaHCO₃溶液碳化后RAC的碳酸钙含量比碳化箱碳化后高10.3%，比自然碳化高16.5%。最后，提出了NaHCO₃溶液碳化后RAC的早期力学性能指标计算方法和本构方程。
- 再生骨料混凝土 /
- 固碳 /
- 碳酸氢钠溶液碳化法 /
- 早期性能 /
- 热重分析 /
- 本构方程
Abstract: In order to improve the carbon fixation efficiency and mechanical properties of recycled aggregate concrete (RAC), sodium bicarbonate (NaHCO₃) solution was used for soaking curing and accelerated carbonation of RAC. Cube and prism compression tests and four point bending tests were conducted to study the effects of three carbonation environments (natural carbonation, carbonation box carbonation, NaHCO₃ solution carbonation) and carbonation age (3-28 d) on the early mechanical properties of RAC. The results showed that compared to the natural environment, the carbonation environment of NaHCO₃ solution can increase the early compressive strength and flexural strength of RAC by up to 8.4% and 12.4%, respectively, but it can also increase brittleness. Before 21 days, the early compressive strength and strength development of RAC after carbonation of NaHCO₃ solution were slightly lower than those in the carbonation environment of the carbonation box, but significantly improved at 28 days; The carbonation age has little effect on the flexural strength of RAC, but at the same age, the flexural strength of NaHCO₃ solution after carbonation is the highest. Through thermogravimetric analysis, it was found that the calcium carbonate content in RAC after carbonation of NaHCO₃ solution was 10.3% higher than that after carbonation in the carbonation box, and 16.5% higher than that of natural carbonation. Finally, a calculation method and constitutive equation for the early mechanical properties of RAC after carbonation of NaHCO₃ solution were proposed.
- Recycled aggregate concrete /
- Carbon sequestration /
- Sodium bicarbonate solution carbonation method /
- Early performance /
- Thermogravimetric analysis /
- Constitutive equation

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图 1 试验所用再生粗骨料和机制砂

Figure 1. Recycled coarse aggregate and machine-made sand used in the experiment

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图 2 试块养护过程

Figure 2. Curing process of specimens

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图 3 碳酸氢钠溶液配制过程

Figure 3. Preparation process of sodium bicarbonate solution

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图 4 试验加载示意图

Figure 4. Experimental loading diagram

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图 5 试件受压和抗折破坏形态

Figure 5. Compression and flexural failure modes of specimens

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图 6 不同养护环境下RAC的轴压应力-应变曲线(σ为轴向应力，ε为轴向应变)

Figure 6. Axial compressive stress-strain curves of RAC under different maintenance environments (σ is axial stress, ε is axial strain)

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图 7 不同龄期下RAC的轴压应力-应变曲线(σ为轴向应力，ε为轴向应变)

Figure 7. Axial compressive stress-strain curves of RAC at different ages (σ is axial stress, ε is axial strain)

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图 8 RAC抗压强度变化图(f_cu为立方体抗压强度，f_ck为轴心抗压强度)

Figure 8. Compression strength variation chart of RAC (f_cu is the compressive strength of the cube, f_ck is the axial compressive strength)

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图 9 RAC抗压强度增长率(f_cu,28为28 d立方体抗压强度，f_ck,28为28 d轴心抗压强度)

Figure 9. Growth rate of compressive strength of RAC (f_cu,28 is the compressive strength of the cube at 28 d,f_ck,28 is the axial compressive strength at 28 d)

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图 10 RAC延性系数μ变化图

Figure 10. Ductility coefficient (μ) variation chart of RAC

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图 11 RAC抗折强度f_t变化图

Figure 11. Diagram of changes in flexural strength f_t of RAC

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图 12 RAC TG结果分析

Figure 12. TG result analysis of RAC

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图 13 RAC DTG结果分析

Figure 13. DTG result analysis of RAC

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图 14 不同养护条件下RAC的微观形貌

Figure 14. Microscopic morphology of RAC under different curing conditions

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图 15 RAC早期强度预测结果对比

Figure 15. Comparison of early strength prediction results of RAC

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图 16 NaHCO₃溶液碳化后RAC的轴心抗压强度f_ck和立方体抗压强度f_cu的关系

Figure 16. Relationship between axial compressive strength f_ck and f_cuof cube strength RAC after carbonation of NaHCO₃ solution

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图 17 NaHCO₃溶液碳化后RAC的抗折强度f_t和立方体抗压强度f_cu的关系

Figure 17. Relationship between flexural strength f_t and cube strength f_cu of RAC after carbonation of NaHCO₃ solution

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图 18 NaHCO₃溶液碳化后RAC的峰值应变ε_c和立方体抗压强度f_cu的关系

Figure 18. Relationship between peak strain ε and cube strength f_cu of RAC after carbonation of NaHCO₃ solution

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图 19 RAC本构方程计算结果对比

Figure 19. Comparison of constitutive equation calculation results of RAC

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表 1 试件设计参数

Table 1. Design parameters of specimens

Specimen number	Carbonation environment	Environmental parameters	Curing age T/d
RAC-3d	Natural carbonation	Natural environment	3
RAC-7d			7
RAC-14d			14
RAC-21d			21
RAC-28d			28
RAC-CB-3d	Carbonation box	Carbon dioxide concentration of 20%, temperature of 20℃, humidity of 70%	3
RAC-CB-7d			7
RAC-CB-14d			14
RAC-CB-21d			21
RAC-CB-28d			28
RAC-L10-3d	NaHCO₃ solution	10 g/L	3
RAC-L10-7d			7
RAC-L10-14d			14
RAC-L10-21d			21
RAC-L10-28d			28

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表 2 再生混凝土(RAC)配合比(kg/m³)

Table 2. Mix ratio of recycled aggregate concrete (RAC) (kg/m³)

Cement	Recycled coarse aggregate	Machine-made sand	Water	Mineral powder	Water reducing agent	Limestone
340	1060	735	145	70	9.45	40

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表 3 再生粗骨料和机制砂的基本性能

Table 3. Basic properties of recycled coarse aggregate and machine-made sand

Types of aggregates	Density/ (kg∙m⁻³)	Bulk density/ (kg∙m⁻³)	Loose packing porosity/%	Mud content/%	Stone powder content/%	Clay lump/%	Total content of needle shaped particles/%	Crushing index
Recycled coarse aggregate	2720	—	45	0.7	—	0.1	8	9
Machine-made sand	2710	1610	41	—	5.5	0.8	—	—

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表 4 力学性能指标

Table 4. Mechanical performance indicators

Specimen number	f_cu/ MPa		f_ck/ MPa		f_t/ MPa		μ
Specimen number	Measurement value	Average	Measurement value	Average	Measurement value	Average	Measurement value	Average
RAC-3d	50.1	51.3	27.9	26.5	4.96	5.11	1.21	1.42
	53.0		25.8		5.36		1.59
	50.7		25.7		5.02		1.46
RAC-7d	62.4	60.7	31.6	32.2	4.41	5.05	1.56	1.45
	58.8		33.4		5.50		1.46
	60.9		31.6		5.26		1.33
RAC-14d	64.9	64.9	31.8	34.8	5.05	5.10	1.44	1.41
	64.9		39.2		3.99		1.36
	54.2		33.5		5.21		1.43
RAC-21d	64.9	67.9	36.2	37.5	5.10	5.21	1.38	1.34
	70.9		35.7		5.34		1.34
	37.8		40.7		5.18		1.31
RAC-28d	71.4	72.1	38.6	39.0	5.22	5.18	1.33	1.26
	72.4		36.1		5.16		1.36
	72.7		42.3		4.96		1.10
RAC-CB-3d	59.5	53.3	27.8	28.4	3.79	3.99	1.44	1.40
	49.7		27.8		2.64		1.46
	50.8		29.7		4.19		1.3
RAC-CB-7d	61.6	62.8	34.6	31.6	3.99	4.22	1.28	1.39
	65.2		30.2		4.35		1.33
	61.7		30.1		4.33		1.56
RAC-CB-14d	72.3	71.5	34.6	34.6	3.45	3.67	1.42	1.37
	60.7		35.7		3.89		1.31
	70.7		33.6		3.68		1.39
RAC-CB-21d	69.5	71.8	38.9	37.0	4.29	4.44	1.18	1.27
	71.4		34.1		4.62		1.39
	74.6		37.9		4.43		1.25
RAC-CB-28d	73.7	73.2	40.1	40.0	4.44	4.12	1.32	1.20
	74.5		37.7		3.86		1.33
	71.3		42.2		4.07		1.23
RAC-L10-3d	52.8	52.0	26.3	26.6	4.63	4.33	1.47	1.29
	50.6		27.6		4.95		1.20
	52.6		25.9		3.43		1.42
RAC-L10-7d	58.1	62.4	22.5	31.7	5.81	5.03	1.14	1.36
	66.4		31.7		4.84		1.46
	62.8		31.8		4.44		1.28
RAC-L10-14d	64.1	66.0	38.8	35.3	4.88	4.80	1.26	1.29
	67.4		32.8		5.05		1.22
	66.4		34.2		4.48		1.28
RAC-L10-21d	72.1	68.6	34.1	36.9	5.86	5.86	1.19	1.25
	63.9		38.7		5.94		1.18
	69.8		37.8		5.80		1.09
RAC-L10-28d	79.5	78.2	38.4	40.8	4.94	5.26	1.32	1.15
	63.9		40.9		5.33		1.33
	76.9		43.0		5.54		1.23
Notes: f_cu, f_ck, and f represent the compressive strength of cubes, the compressive strength of prisms, and the flexural strength, respectively. μ is the ductility coefficient, which is calculated through the compressive stress-strain curve of a prism using the "equal energy" method^[25]. The data in the table is taken as the average of the same operating conditions.

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