基于CT技术的冷再生混合料冻融环境下损伤分析

王石; 赵宪锋; 米弘泽

doi:10.13801/j.cnki.fhclxb.20210601.004

基于CT技术的冷再生混合料冻融环境下损伤分析

doi: 10.13801/j.cnki.fhclxb.20210601.004

兰州交通大学　土木工程学院，兰州 730070

基金项目: 国家自然科学基金青年基金(11302091)

详细信息

通讯作者:
赵宪锋，博士，副教授，硕士生导师，研究方向为工程结构力学、电磁固体力学、颗粒介质力学　E-mail：zhaoxf@mail.lzjtu.cn

中图分类号: U414；TB33
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- 被引次数: 0
出版历程
- 收稿日期: 2021-04-20
- 修回日期: 2021-05-19
- 录用日期: 2021-05-27
- 网络出版日期: 2021-06-02
- 刊出日期: 2022-04-01

Damage analysis of cold recycled mixture under freeze-thaw environment based on CT technology

School of Civil Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China

摘要

摘要: 通过室内实验揭示冻融环境下水泥稳定冷再生混合料细观结构的损伤演化规律，并分析水泥和旧路面沥青材料(RAP)在不同的冻融循环时期对其损伤的影响。使用CT机对冻融循环后的试件进行扫描，获得二维断层扫描图像。利用图像处理技术对扫描断面进行分析，并以图像中CT均值的变化为基础引入损伤变量。研究结果表明：随着冻融循环次数n的增加，混合料断面的CT均值呈现出先增大后减小的变化规律；损伤变量则表现出先减小后增大的变化趋势，反映出了冻融环境下水泥稳定冷再生混合料从初始细观损伤到宏观破损的全过程，可分为4个阶段：即$N \leqslant 1$、$1 < N \leqslant 3$、$3 < N \leqslant 7$和$7 < N \leqslant 9$，且在N小于7次时水泥含量对试件损伤有显著影响，水泥可提高混合料的粘结性及早期强度；大于7次时试件的损伤主要受到RAP掺量的影响，过高的RAP含量会加剧混合料的损伤。
- 再生材料 /
- 冻融循环 /
- CT /
- 细观损伤 /
- 旧沥青路面材料
Abstract: The development of meso-damage of cement stabilized cold recycled mixture under freeze-thaw environment was revealed by indoor test, and the effects of cement and recycled asphalt pavement material (RAP) on its damage in different freeze-thaw cycles were analyzed. The specimen after freeze-thaw cycle was scanned by CT machine, and the batch of 2D slice images were obtained. The cross section was analyzed by using the image processing technology, and the damage variable was introduced based on the change of the CT mean value in the image. The results show that with the increase of the number of freeze-thaw cycles, the average CT of mixture cross section increases at first and then decreases. On the other hand, the damage variable first decreases and then increases, which reflects the whole process of cement stable cold recycled mixture from initial meso damage to macroscopic damage in freeze-thaw environment, which can be divided into four stages, i.e. $N \leqslant 1$, $1 <N \leqslant 3$, $3 < N \leqslant 7$ and $7 < N \leqslant 9$. When the number of freeze-thaw cycles is less than 7, the cement content has a significant effect on the specimen damage, and the addition of cement can improve the adhesion and early strength of the mixture. When the number of freeze-thaw cycles is more than 7 times, the damage of the specimen is mainly affected by the content of RAP, and the excessive content of RAP will aggravate the damage of the mixture.
- recycled materials /
- freeze thaw cycle /
- CT /
- meso-damage /
- recycled asphalt pavement material

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图 1 冻融循环CSCRM试件

Figure 1. Specimens of CSCRM before freeze-thaw cycle

下载: 全尺寸图片幻灯片

图 2 冻融循环后破损的CSCRM试件

Figure 2. Specimens of CSCRM damaged after freeze-thaw cycle

下载: 全尺寸图片幻灯片

图 3 3种冻融循环次数N下CSCRM (70wt%RAP)-CTS3试件距底面45 mm横断面等密度分割图像

Figure 3. Isodensity segmentation images of CSCRM (70wt%RAP)-CTS3 specimen 45 mm from the bottom under the conditions for three freeze-thaw cycles N

下载: 全尺寸图片幻灯片

图 4 CSCRM(30wt%RAP)-CTS1试样距顶面12 mm横断面不同冻融次数N下的CT图像

Figure 4. CT images of CSCRM(30wt%RAP)-CTS1 specimen with different freeze-thaw times N in cross-section 12 mm from the top surface

下载: 全尺寸图片幻灯片

图 5 CSCRM(50wt%RAP)-CTS1试样距顶面12 mm横断面不同冻融次数N下的CT图像

Figure 5. CT images of CSCRM(50wt%RAP)-CTS1 specimen with different freeze-thaw times N in cross-section 12 mm from the top surface

下载: 全尺寸图片幻灯片

图 6 CSCRM(70wt%RAP)-CTS1试样距顶面12 mm横断面不同冻融次数N下的CT图像

Figure 6. CT images of CSCRM(70wt%RAP)-CTS1 specimen with different freeze-thaw times N in cross-section 12 mm from the top surface

下载: 全尺寸图片幻灯片

图 7 CSCRM的CT数均值随冻融次数变化曲线

Figure 7. Curves of the mean value of CT number with the number of freezing and thawing

$\Delta \bar{H}$—Average CT number

下载: 全尺寸图片幻灯片

图 8 CSCRM损伤度随冻融次数变化曲线

Figure 8. Change curves of damage degree of CSCRM with freeze-thaw cycles times

ΔD—Damage degree changes

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图 9 CSCRM的损伤度与劈裂强度的关系

Figure 9. Relationship between damage degree and splitting strength of CSCRM

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表 1 试件材料参数

Table 1. Material property parameters of specimen

Item	Apparent density/(kg·m⁻³)	Voidage/%	Needle-like particle content/%	Mud content/%
RAP	2.653	47.3	16.4	0.3
0-5 mm aggregate	2.574	42.3	5.3	15.2
Note: RAP—Recycled asphalt pavement.

下载: 导出CSV

表 2 水泥稳定冷再生混合料(CSCRM)级配

Table 2. Gradation of cement stabilized cold recycled mixture (CSCRM)

Specimen	Gradation of mixture/%
Specimen	0.15 /mm	0.60 /mm	2.36 /mm	4.75 /mm	9.50 /mm	19.0 /mm	26.5 /mm	31.5 /mm
CSCRM(30wt%RAP)	11.1	37.5	53.9	71.5	84.2	96.7	99.8	100
CSCRM(50wt%RAP)	18.1	26.3	40.1	56.5	73.5	94.0	99.4	100
CSCRM(70wt%RAP)	5.0	16.9	26.5	40.7	62.1	91.9	99.2	100

下载: 导出CSV

表 3 CSCRM配合比

Table 3. Mix ratio of CSCRM

Specimen	RAP test value /wt%	Aggregate/wt%	Cement /wt%	Water /wt%
CSCRM(30wt%RAP)	27.65	64.52	2.76	5.07
CSCRM(50wt%RAP)	46.17	46.17	2.76	4.90
CSCRM(70wt%RAP)	63.87	27.37	4.56	4.20

下载: 导出CSV

表 4 CT机扫描参数

Table 4. Scanning parameters of CT machine

Voltage /kV	Electric current/mA	Layer thickness/mm	Reconstruction matrix	Magnification
120	185	3	1024×1024	1

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表 5 劈裂夹具参数

Table 5. Parameters of splitting fixture

Maximum bracket block/mm	Width of left and right gear of bracket/mm	Length/ mm
50×20	151, 101	305

下载: 导出CSV

表 6 3种不同配合比CSCRM的冻融劈裂强度

Table 6. Freeze-thaw splitting strength of CSCRM with three different combinations under different cycles

Freeze-thaw time	Splitting strength/MPa
Freeze-thaw time	CSCRM (30wt%RAP)	CSCRM (50wt%RAP)	CSCRM (70wt%RAP)
0	0.62	0.53	0.71
1	0.58	0.49	0.66
3	0.53	0.45	0.62
5	0.50	0.42	0.58
7	0.48	0.40	0.55
9	0.47	0.39	0.53

下载: 导出CSV

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