表面改性重组竹筋与竹炭砂浆界面粘结性能

郑皓月; 刘问

表面改性重组竹筋与竹炭砂浆界面粘结性能

郑皓月,
刘问^,

北京林业大学　水土保持学院, 北京 100083

基金项目: 中央高校基本科研业务费专项资金资助 (2021ZY53)

详细信息

通讯作者:
刘问，博士，副教授，硕士生导师，研究方向为竹木结构、低碳混凝土　E-mail: liuwen@bjfu.edu.cn

中图分类号: TB332
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- 文章访问数: 95
- HTML全文浏览量: 67
- 被引次数: 0
出版历程
- 收稿日期: 2022-11-17
- 修回日期: 2023-01-09
- 录用日期: 2023-01-10
- 网络出版日期: 2023-02-07

Bond performance between surface modified bamboo scrimber bar and bamboo biochar mortar

Haoyue ZHENG,
Wen LIU^,

School of Water and Soil Conservation, Beijing Forestry University, Beijing 100083, China

Funds: The Fundamental Research Funds for the Central Universities (2021ZY53)

摘要

摘要: 我国竹资源丰富，竹材作为天然的绿色建材，被誉为“植物钢筋”，原竹竹筋增强混凝土结构已有百余年的研究应用历史。重组竹是基于原竹的竹纤维增强复合材料，与原竹相比具有结构致密均匀、性能稳定、耐久性强等优点，将其改性处理后用于增强水泥基材料预期可改善原竹竹筋节点复杂、吸水易膨胀、表面锚固能力弱等问题；对于钢筋而言，重组竹的强重比低、生产耗能低，是可再生的绿色材料，具有良好的减排作用。此外，竹炭砂浆由竹炭替代部分水泥作为胶凝材料应用于砂浆中制备而成，相较于普通砂浆，其在保证力学性能的前提下可以减少水泥用量，降低碳排放，且在物理力学性能和耐久性等方面有诸多优势。考虑将重组竹和竹炭砂浆组合使用，既保证了结构的力学性能，又降低了钢筋混凝土结构的碳排放，解决了原竹竹筋混凝土结构不稳定、承载能力较差等问题。将重组竹筋作为增强筋应用于实际工程中，其与水泥基材料良好的界面粘结性能是基础。本文旨在研究表面改性的重组竹筋与竹炭砂浆的界面粘结性能，重点探究竹筋表面改性方法、等效直径、砂浆抗压强度、粘结长度等因素对界面粘结性能的影响。结果表明：在不同初始条件下，试件存在三种破坏形态，分别为砂浆劈裂破坏、竹筋拉断破坏、竹筋拔出破坏，其中砂浆劈裂破坏最为常见，破坏过程分为微滑移段、滑移段、下降段和残余段。对竹筋表面改性处理能显著提高界面粘结性能，粘结性能随竹筋粘结长度和等效直径的增大而降低，而砂浆强度对粘结性能的影响效果不显著。根据试验得到的粘结-滑移曲线，得到了表面经粘砂处理的重组竹筋-竹炭砂浆界面粘结-滑移本构模型，可准确预测重组竹筋与砂浆间的粘结行为。
- 重组竹筋 /
- 竹炭砂浆 /
- 中心拉拔试验 /
- 粘结-滑移本构模型 /
- 粘结性能
Abstract: In order to study the bonding performance of bamboo scrimber bar-bamboo biochar mortar interface, pull-out tests were carried out on 85 bamboo scrimber bar-bamboo biochar mortar specimens. The effects of surface modification methods of bamboo bar, equivalent diameter of bamboo bar, compressive strength of mortar and bond lengths on the bond properties were also taken into consideration. The different bonding failure modes of the pull-out specimens were observed. The bond-slip curve, bonding strength and slippage were obtained. The failure mechanism was analyzed. A bond-slip constitutive model of bamboo scrimber bar-bamboo biochar mortar interface was established, and the effective surface modification method of bamboo scrimber bar was obtained. The results of the study show that there are three failure modes of the specimens under different initial conditions, including mortar splitting failure, bamboo bar tensile failure and bamboo bar pulled-out failure, among which mortar splitting failure is the most common. The failure process can be divided into micro-slip stage, slip stage, descending stage and residual stage. The bonding strength of the mortar interface can be increased by 13-46 times by modifying the surface of the bamboo bar. The interfacial bonding performance decreases with the increase of bonding length and equivalent diameter, and the effect of mortar strength on bonding strength is not obvious. It is recommended to modify the bamboo scrimber bar through the two methods of sticking sand and coating epoxy mortar. On the basis of ensuring bonding performance, it can improve the peeling of water absorption and expansion of bamboo bands during the maintenance process and the problem of the structure failing in advance. According to the experimental bond-slip curve, the bond-slip constitutive model of bamboo scrimber bar-bamboo biochar mortar treated by sticking sand was proposed. The bond-slip constitutive model can accurately predict the bond behavior between bamboo scrimber bar and mortar. After verification, the model is also applicable to the bonding interface destruction in the test under the other modification of bamboo.
- bamboo scrimber bar /
- bamboo biochar mortar /
- center pull-out test /
- bond-slip constitutive model /
- bonding performance

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图 1 重组竹抗拉试样(单位：mm)

Figure 1. Bamboo scrimber tensile specimen (Unit:mm)

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图 2 竹筋不同改性方法

Figure 2. Different surface modification methods of bamboo scrimber bar

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图 3 拉拔试件示意图(单位：mm)

Figure 3. Sketch of pullout sample (Unit:mm)

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图 4 加载装置

Figure 4. Loading installation

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图 5 重组竹筋-竹炭砂浆拉拔试件三种破坏形态

Figure 5. Three types failure modes of bamboo scrimber bar-bamboo biochar mortar pull-out specimens

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图 6 不同初始条件下重组竹筋-竹炭砂浆试件的平均粘结强度

Figure 6. Average bond strength of bamboo scrimber bar-bamboo biochar mortar specimens under different initial conditions

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图 7 重组竹筋-竹炭砂浆拉拔试件粘结-滑移曲线

Figure 7. Bond-slip curves of bamboo scrimber bar-bamboo biochar mortar pull-out specimens

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图 8 重组竹筋-竹炭砂浆拉拔试件粘结-滑移曲线简化模型

Figure 8. Bond-slip curve simplified model of bamboo scrimber bar-bamboo biochar mortar pull-out specimens

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图 9 重组竹筋-竹炭砂浆试件应变和应力分布规律

Figure 9. Strain and bonding strss distribution of bamboo scrimber bar-bamboo biochar mortar specimen

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图 10 重组竹筋-竹炭砂浆本构模型验证

Figure 10. Constitutive model verification of bamboo scrimber-bamboo biochar mortar

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表 1 竹炭砂浆配合比

Table 1. Mix proportion of bamboo biochar mortar

Water cement ratio	Cement/(kg·m⁻³)	Bamboo biochar/(kg·m⁻³)	Water/(kg·m⁻³)	Sand/(kg·m⁻³)	f_cu/MPa
0.45	549.45	5.55	250	1500	50
0.5	564.30	5.70	285	1500	45
0.58	500.94	5.06	300	1500	40

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表 2 拉拔试件明细

Table 2. Details of pull-out specimens

Specimen number	f_cu/MPa	L/mm	a/mm	b/mm	d/mm	Surface treatment method	Failure pattern	Average value of bond strength/MPa
A-0.5-50-360	45	50	20	18	24.19	Stick sand	P	7.67
A-0.5-70-360	45	70	20	18	24.19	Stick sand	P、S	6.02
A-0.5-100-360	45	100	20	18	24.19	Stick sand	S	4.36
A-0.5-140-360	45	140	20	18	24.19	Stick sand	S	3.47
A-0.5-180-360	45	180	20	18	24.19	Stick sand	S	2.80
A-0.58-100-360	40	100	20	18	24.19	Stick sand	S	4.24
A-0.45-100-360	50	100	20	18	24.19	Stick sand	S	4.31
A-0.5-100-216	45	100	18	12	19.10	Stick sand	F	4.21
A-0.5-100-270	45	100	18	15	21.01	Stick sand	F	4.73
A-0.5-100-500	45	100	20	25	28.65	Stick sand	S	3.82
B-0.5-100-360(20)	45	100	20	18	24.19	Nick	P	1.73
B-0.5-100-360(40)	45	100	20	18	24.19	Nick	F	2.53
B-0.5-100-360(60)	45	100	20	18	24.19	Nick	F	3.51
C-0.5-100-360(1)	45	100	20	18	24.19	Coat epoxy mortar	S	3.84
C-0.5-100-360(2)	45	100	20	18	24.19	Coat epoxy mortar	S	4.66
O-0.5-100-360	45	100	20	18	24.19	Untreated	P	0.13
O-0.5-180-360	45	180	20	18	24.19	Untreated	P	0.15
Notes: A, B, C, O represent the method of sticking sand, nicking, coating epoxy mortar and untreated bamboo scrimber surface modification methods; f_cu is the mortar pressure resistance intensity; L is the bonding length; a is the original thickness of bamboo scrimber bar; b is the original width of bamboo scrimber bar; d is the equivalent diameter of bamboo scrimber bar; "S" represents the spliting failure; "P" represents the pulling-out failure; "F" represents the tensile failure.

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表 3 竹筋膨胀率

Table 3. Expansion rate of bamboo scrimber bar

Specimen number	a/mm	a₁/mm	W_a/%	b/mm	b₁/mm	W_b/%
A-0.5-50-360	20.01	20.33	1.60	18.02	18.32	1.66
A-0.5-100-360	20.03	20.32	1.45	18.06	18.33	1.50
A-0.5-180-360	19.96	20.14	0.90	18.10	18.25	0.83
A-0.58-100-360	20.00	20.36	1.80	18.03	18.45	2.33
A-0.45-100-360	20.06	20.21	0.75	18.03	18.23	1.11
A-0.5-100-500	20.05	20.35	1.50	24.98	25.42	1.76
B-0.5-100-360(20)	20.03	20.93	4.49	17.97	18.78	4.51
C-0.5-100-360(1)	19.99	20.17	0.90	18.00	18.22	1.22
O-0.5-100-360	20.00	20.76	4.30	18.01	18.72	3.94
Notes: a is the original thickness of bamboo scrimber bar; a₁ is the thickness of bamboo scrimber bar after 28 days of maintenance; W_a is the expansion rate of the thickness direction of the bamboo scrimber bar; b is the original width of bamboo scrimber bar; b₁ is the width of bamboo scrimber bar after 28 days of maintenance; W_b is the expansion rate of the width direction of the bamboo scrimber bar.

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表 4 重组竹筋-竹炭砂浆试件粘结-滑移曲线拟合结果

Table 4. Bond-slip curves fitting results of bamboo scrimber bar-bamboo biochar mortar specimens

Specimen number	Rising stage		Descending stage
Specimen number	α	R²	n	R²
A-0.5-70-360	0.366	0.880	2.206	0.991
A-0.5-100-360	0.332	0.954	1.969	0.994
A-0.5-140-360	0.397	0.931	2.091	0.976
A-0.5-180-360	0.239	0.960	1.999	0.975
A-0.58-100-360	0.428	0.976	1.937	0.988
A-0.45-100-360	0.432	0.982	1.744	0.958
A-0.5-100-500	0.499	0.947	2.330	0.941

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