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Microstructural analysis of freeze–thaw degradation in rubber-modified cement-stabilized crushed stone using X-ray computed tomography

Shuai Mao

Shuai Mao

  • School of Traffic and Transportation, Shijiazhuang Tiedao UniversityShijiazhuang, China
  • State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures, Shijiazhuang Tiedao UniversityShijiazhuang, China
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Mao, Shuai
, 
Yongqing Lin

Yongqing Lin

Beijing Jiaotong Vocational Technical CollegeBeijing, China
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Lin, Yongqing
 et 
Zurun Yue

Zurun Yue

State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures, Shijiazhuang Tiedao UniversityShijiazhuang, China
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Yue, Zurun
  
16 sept. 2025
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Catégorie d'article: Research Article
Publié en ligne: 16 sept. 2025
Pages: 50 - 63
Reçu: 10 juil. 2025
Accepté: 01 sept. 2025
DOI: https://doi.org/10.2478/msp-2025-0029
Mots clés
© 2025 Shuai Mao, published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Figure 1

Flow chart of unconfined compressive strength test: (a) sample preparation, (b) sample curing, (c) sample soaking, and (d) unconfined compressive strength test.
Flow chart of unconfined compressive strength test: (a) sample preparation, (b) sample curing, (c) sample soaking, and (d) unconfined compressive strength test.

Figure 2

Sample preparation for CT analysis: (a) core drilling from the larger cured specimen and (b) final cylindrical sample (Φ50 mm × 50 mm).
Sample preparation for CT analysis: (a) core drilling from the larger cured specimen and (b) final cylindrical sample (Φ50 mm × 50 mm).

Figure 3

Representative grayscale histogram used for phase segmentation.
Representative grayscale histogram used for phase segmentation.

Figure 4

Industrial CT gray image underlying database processing: (a) extracting pore from original image, (b) extracting rubber powder from original image, and (c) the original figure distinguishes the pores and rubber powder.
Industrial CT gray image underlying database processing: (a) extracting pore from original image, (b) extracting rubber powder from original image, and (c) the original figure distinguishes the pores and rubber powder.

Figure 5

Change in porosity of specimens during F–T cycling. The black bars represent the porosity increase after 5 cycles (compared to 0 cycles), and the red bars represent the additional increase after 10 cycles (compared to 5 cycles).
Change in porosity of specimens during F–T cycling. The black bars represent the porosity increase after 5 cycles (compared to 0 cycles), and the red bars represent the additional increase after 10 cycles (compared to 5 cycles).

Figure 6

Volume proportion of rubber powder in each slice.
Volume proportion of rubber powder in each slice.

Figure 7

Correlation analysis of progressive versus initial pore expansion under F–T cycling for specimens with varying rubber content. Each point represents a single CT slice. The POEI, defined as the coefficient of determination (R 2), is shown for each specimen, along with the corresponding p-value indicating statistical significance. (a) C5R0 (0% rubber), (b) C5R10 (10% rubber), (c) C5R20 (20% rubber), (d) C5R30 (30% rubber), and (e) C5R45 (45% rubber).
Correlation analysis of progressive versus initial pore expansion under F–T cycling for specimens with varying rubber content. Each point represents a single CT slice. The POEI, defined as the coefficient of determination (R 2), is shown for each specimen, along with the corresponding p-value indicating statistical significance. (a) C5R0 (0% rubber), (b) C5R10 (10% rubber), (c) C5R20 (20% rubber), (d) C5R30 (30% rubber), and (e) C5R45 (45% rubber).

Figure 8

Comparative trend chart illustrating the trade-off between 28-day unconfined compressive strength and BDR after 30 F–T cycles.
Comparative trend chart illustrating the trade-off between 28-day unconfined compressive strength and BDR after 30 F–T cycles.

Figure 9

Correlation between the POEI (R 2) and the BDR (ten cycles) for materials with varying rubber content.
Correlation between the POEI (R 2) and the BDR (ten cycles) for materials with varying rubber content.

Figure 10

Quadratic model of the POEI (R 2) as a function of rubber content.
Quadratic model of the POEI (R 2) as a function of rubber content.

Figure 11

Change of the proportion of each pore number under the action of the F–T cycle.
Change of the proportion of each pore number under the action of the F–T cycle.

Figure 12

Change of the pore volume ratio: (a) under F–T cycles and (b) proportion of ultra-large pore volume.
Change of the pore volume ratio: (a) under F–T cycles and (b) proportion of ultra-large pore volume.

Figure 13

Changes in microstructure of CSCS before and after F–T cycles: (a) Cement stabilized macadam material five times F–T and non-F–T 3D pore diagram comparison chart. (b) Comparison of 3D pore diagram of cement stabilized macadam material between ten F–T cycles and five F–T cycles. (c) The 3D pore diagram comparison diagram of cement stabilized macadam with 30% rubber powder content after five F–T cycles and no F–T cycles. (d) The 3D pore diagram comparison of ten F–T cycles and five F–T cycles of CSCS materials with rubber powder content of 30%.
Changes in microstructure of CSCS before and after F–T cycles: (a) Cement stabilized macadam material five times F–T and non-F–T 3D pore diagram comparison chart. (b) Comparison of 3D pore diagram of cement stabilized macadam material between ten F–T cycles and five F–T cycles. (c) The 3D pore diagram comparison diagram of cement stabilized macadam with 30% rubber powder content after five F–T cycles and no F–T cycles. (d) The 3D pore diagram comparison of ten F–T cycles and five F–T cycles of CSCS materials with rubber powder content of 30%.

Figure 14

Schematic illustration of the proposed micro-mechanical model for F–T degradation. (a) In the low-content regime, isolated rubber particles act as stress concentrators, leading to the nucleation of new, disordered microcracks (low POEI). (b) In the high-content regime, an interconnected rubber network absorbs frost-heave energy, resulting in a more benign, orderly expansion of existing pores (high POEI).
Schematic illustration of the proposed micro-mechanical model for F–T degradation. (a) In the low-content regime, isolated rubber particles act as stress concentrators, leading to the nucleation of new, disordered microcracks (low POEI). (b) In the high-content regime, an interconnected rubber network absorbs frost-heave energy, resulting in a more benign, orderly expansion of existing pores (high POEI).

CSCS sample particle size gradation (C5P0_1)_

Square hole screen aperture (mm) 45 31.5 22.4 7.1 1.7 0.5 0.1
Percentage of screen mass 100 91 79 58 30 19 0

Evaluation index of BDR_

Sample C5R0 C5R10 C5R20 C5R30 C5R45
5 F–T cycles BDR (%) 93.9 60.3 69.3 95.3 105.7
10 F–T cycles BDR (%) 89.5 58.2 61.5 92.4 97.7
30 F–T cycles BDR (%) 72.3 53.4 53.6 87.0 94.8

Basic parameters of crushed stone_

Parameter type Test value (%) Limit (%)
Los Angeles attrition rate (>1.7 mm) 21.4 ≤30
Plasticity index (<0.5 mm) 4.8 <6
Loss rate of sodium sulfate solution 5.6 ≤6

Unconfined compressive strength test results for extended F–T cycles_

Sample description C5R0 (MPa) C5R10 (Mpa) C5R20 (Mpa) C5R30 (Mpa) C5R45 (Mpa)
7 days UCS 10.48 4.56 2.72 1.68 1.35
28 days UCS 11.62 7.41 5.24 2.38 1.74
5 F–T cycles UCS 10.91 4.47 3.63 2.27 1.84
10 F–T cycles UCS 10.41 4.31 3.22 2.21 1.70
15 F–T cycles UCS 9.40 4.10 3.11 2.15 1.69
20 F–T cycles UCS 8.80 4.02 2.93 2.11 1.67
30 F–T cycles UCS 8.40 3.96 2.81 2.07 1.65

X-ray CT equipment parameters_

Equipment parameters Specific range and values
Maximum sample size Φ50 mm
Scanning voltage 150 kV
Current 60 μA
Exposure time 0.55 s
Voxel resolution 30 μm/pixel
Langue:
Anglais
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