直剪作用下再生混凝土力学性能及强度指标换算

陈宇良; 刘杰; 吴辉琴; 晏方

doi:10.13801/j.cnki.fhclxb.20210122.001

直剪作用下再生混凝土力学性能及强度指标换算

doi: 10.13801/j.cnki.fhclxb.20210122.001

广西科技大学　土木建筑工程学院，柳州 545006

基金项目: 国家自然科学基金(51908141)；广西科技基地和人才专项(AD19110068)；广西自然科学基金(2019GXNSFBA245030)；广西水工程材料与结构重点实验室(GXHRI-WEMS-2020-05)；广西科技大学博士基金项目(校科博18Z09)

详细信息

通讯作者:
吴辉琴，教授，硕士生导师，研究方向为绿色建材、先进材料及其应用　E-mail：whq6329@163.com

中图分类号: TU528.01 TU317.1
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- 文章访问数: 1151
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- 被引次数: 0
出版历程
- 收稿日期: 2020-11-26
- 录用日期: 2021-01-11
- 网络出版日期: 2021-01-22
- 刊出日期: 2021-11-01

Mechanical properties and strength index conversion of recycled aggregate concrete under direct shear

College of Civil and Architecture Engineering, Guangxi University of Science and Technology, Liuzhou 545006, China

摘要

摘要: 以再生粗骨料取代率为变化参数，通过75个再生混凝土(RAC)试件的直剪、抗压与劈裂抗拉试验，揭示了RAC的直剪破坏机制及不同强度指标之间的换算规律。结果表明：RAC在直剪作用下为明显的脆性破坏，粗骨料和水泥基体均被剪断；随着取代率的增加，RAC直剪强度较普通混凝土变化不大，总体上呈降低趋势，但50%取代率(按质量)时直剪强度有所增大；峰值剪切变形随取代率的增大，总体呈增大趋势，平均提高了18.85%；初始剪切变形模量随取代率的增大，总体呈降低的趋势，平均降低了8.97%；最后，基于试验数据提出了RAC剪切强度与抗压、劈裂抗拉强度的换算关系式，计算结果与试验值吻合较好。
- 再生混凝土 /
- 直剪 /
- 抗剪强度 /
- 力学性能 /
- 强度指标
Abstract: In order to study the effect of replacement rate of recycled aggregate concrete (RAC) on the direct shear performance of concrete, 75cubic specimens incorporating different replacement rates of RCA were fabricated. The direct shear test, compressive strength test and splitting tensile strength test were carried out. The failure mechanism of direct shear and the conversion rule between different strength indexes of RAC were revealed. The results show that RAC is obviously brittle failure under direct shear and both the coarse aggregate and cement matrix are sheared. With the increase of the replacement rate, the direct shear strength of RAC has little change compared with the ordinary concrete, and shows a decreasing trend in general. However, the direct shear strength of RAC increases when the replacement rate is 50% (by mass). The peak shear deformation generally increases by 18.85% and the initial shear deformation modulus decreases by 8.97% on average. Finally, based on experimental data, the conversion relationship of RAC between the shear and the compressive and split tensile strength was proposed. The calculated results are in good agreement with the experimental values.
- recycled aggregate concrete /
- direct shear /
- shear strength /
- mechanical properties /
- strength index

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图 1 直剪加载装置示意受力模型

Figure 1. Direct shear loading device force model

1—Vertical actuator; 2—Spherical; 3—Platen; 4—Rollers on the plate; 5—Roller transfer plate; 6—Limit plate; 7—Upper shear box; 8—Horizontal actuator; 9—Specimen; 10—Lower shear box; 11—Lower roller plate; 12—Horizontal rod; 13—Self-adjusting rod

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图 2 RAC直剪破坏形态

Figure 2. Damage patterns of direct shear of RAC

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图 3 RAC的抗压和劈裂破坏形态

Figure 3. Damage patterns of resist compression and tensile strength of RAC

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图 4 RAC的剪切荷载-位移曲线

Figure 4. Shear load-displacement curves of RAC

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图 5 RAC劈拉荷载-变形曲线

Figure 5. Split tensile load-deformation curves of RAC

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图 6 RAC受压荷载-变形曲线

Figure 6. Compression load-deformation curves of RAC

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图 7 RAC直剪和抗压强度对比

Figure 7. Comparison of direct shear and compressive strength of RAC

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图 8 RAC峰值剪切位移

Figure 8. Peak shear displacement of RAC

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图 9 RAC初始剪切变形模量

Figure 9. Initial shear deformation modulus of RAC

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图 10 RAC抗压-抗剪强度拟合曲线

Figure 10. Fitting curves of compressive-shear strength of RAC

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图 11 RAC劈裂抗拉-抗剪强度拟合曲线

Figure 11. Fitting curves of splitting strength-shear strength of RAC

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表 1 粗骨料基本物理性能

Table 1. Physical properties of coarse aggregates

Coarse aggregate	Water content (by mass)/wt%	Water absorption (by mass)/wt%	Apparent density/ (kg·m⁻³)	Stacking density/ (kg·m⁻³)	Crushing indicators/%
NCA	0.098	0.309	2714	1412	19.89
RCA	0.715	1.680	2579	1274	22.80
Notes: NCA—Natural coarse aggregate; RCA—Regenerate coarse aggregate.

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表 2 再生混凝土(RAC)配合比

Table 2. Mix proportions of recycled aggregate concrete (RAC)

Code	r(by mass)/wt%	m_w/m_b	Sand ratio/%	Mix proportion/(kg·m⁻³)
Code	r(by mass)/wt%	m_w/m_b	Sand ratio/%	C	W	W_a	S	NCA	RCA
RAC-0	0	0.55	0.36	353.9	195	0	666.4	1 184.7	0
RAC-10	10	0.55	0.36	353.9	195	2.0	666.4	1 066.2	118.5
RAC-20	20	0.55	0.36	353.9	195	4.0	666.4	947.8	236.9
RAC-30	30	0.55	0.36	353.9	195	6.0	666.4	829.3	355.4
RAC-40	40	0.55	0.36	353.9	195	8.0	666.4	710.8	473.9
RAC-50	50	0.55	0.36	353.9	195	10.0	666.4	592.4	592.4
RAC-60	60	0.55	0.36	353.9	195	11.9	666.4	473.9	710.8
RAC-70	70	0.55	0.36	353.9	195	13.9	666.4	355.4	829.3
RAC-80	80	0.55	0.36	353.9	195	15.9	666.4	236.9	947.8
RAC-90	90	0.55	0.36	353.9	195	17.9	666.4	118.5	1 066.2
RAC-100	100	0.55	0.36	353.9	195	19.9	666.4	0	1 184.7
Notes: r—Replacement rate; m_w/m_b—Water-binder ratio; C—Cement; W—Water; W_a—Additional water; S—Sand.

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表 3 RAC试件特征点参数

Table 3. Feature parameters of RAC specimens

Code	r/%	f_cu/MPa	f_t/MPa	τ_p/MPa	s_p/mm	G_s/(10²kN·mm⁻¹)
RAC-0	0	30.93	2.71	3.33	0.704	1.155
RAC-10	10	28.01	—	3.15	0.657	1.286
RAC-20	20	27.46	—	3.35	0.693	1.202
RAC-30	30	30.63	—	3.25	0.762	1.211
RAC-40	40	28.85	—	3.29	0.849	1.033
RAC-50	50	27.45	3.21	3.49	0.777	1.086
RAC-60	60	26.04	—	3.12	0.794	1.057
RAC-70	70	25.74	—	3.33	0.893	0.836
RAC-80	80	27.96	—	3.25	0.981	0.946
RAC-90	90	27.52	—	3.20	0.957	0.835
RAC-100	100	26.67	1.61	3.19	1.004	1.022
Notes: f_cu—Compressive strength; f_t—Splitting tensile strength; τ_p = V_P/A_s, τ_p—Shear strength, V_P—Direct shear peak load; A_s—Shear area (150 mm×150 mm); s_p—Specimen reaching the peak deformation corresponding to the peak shear load; G_s—Secant modulus corresponding to 0.4V_P.

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表 4 RAC抗剪强度的计算值与实测值对比

Table 4. Comparison of calculated and measured direct shear strength of RAC

r(by mass)/ wt%	Measured value/ MPa	Calculated value/MPa	Calculated value/ Measured value	r(by mass)/ wt%	Measured value/ MPa	Calculated value/MPa	Calculated value/ Measured value
0	3.33	3.43	1.03	60	3.12	3.10	0.99
10	3.15	3.16	1.00	70	3.33	3.08	0.92
20	3.35	3.15	0.94	80	3.25	3.35	1.03
30	3.25	3.56	1.09	90	3.20	3.30	1.03
40	3.29	3.39	1.03	100	3.19	3.19	1.00
50	3.49	3.25	0.93	−	−	−	−

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