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16 pages, 2926 KiB

Open AccessArticle

Characterization of the Cracking Resistance Gradient of Bitumen Emulsion-Based Cold In-Place Recycling Mixtures over Curing by Semi-Circular Bending Test

by Zili Zhao, Jiwang Jiang and Fujian Ni

Coatings 2024, 14(1), 46; https://doi.org/10.3390/coatings14010046 - 28 Dec 2023

Viewed by 588

Abstract

To better reveal the performance development of bitumen emulsion-based cold in-place recycling (BE-CIR) mixture over curing, a semi-sealed laboratory curing method was proposed in this research to simulate the in situ moisture evaporation process and cracking resistance of the BE-CIR specimen at different [...] Read more.

To better reveal the performance development of bitumen emulsion-based cold in-place recycling (BE-CIR) mixture over curing, a semi-sealed laboratory curing method was proposed in this research to simulate the in situ moisture evaporation process and cracking resistance of the BE-CIR specimen at different depths during a curing time of 28 days, which was also investigated by the semi-circular bending (SCB) test. The influencing factors of cement content (1.5% to 2.5%), initial moisture content (3.5% to 4.5%), curing temperature (25 °C to 45 °C) and relative humidity were investigated, and the significance of different factors affecting the performance development was also analyzed. The results indicate significant variations in cracking performance parameters at different depths, with the top part exhibiting notably higher tensile strength and fracture energy compared to the bottom part, and a gradient index (GI) is proposed to describe the difference. Cement content affected early tensile strength and fracture energy, while the initial moisture content affected the development rate of the performance. The influence of curing temperature was extensive, and as the temperature increased beyond 40 °C, the strength of the effect decreased. High humidity during the early stage of curing inhibited the strength formation and development of fracture energy. The performance development of the BE-CIR mixture is more significantly influenced by the moisture migration process, which is governed by curing temperature and relative humidity, as opposed to the cement content and initial moisture content. Full article

(This article belongs to the Special Issue Surface Engineering and Mechanical Properties of Building Materials)

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17 pages, 4395 KiB

Open AccessArticle

An Investigation of the Dynamic Curing Behavior and Micro-Mechanism of a Super-Tough Resin for Steel Bridge Pavements

by Yajin Han, Jiwang Jiang, Jiahao Tian, Zhu Zhang, Fujian Ni and Sheng Zhang

Coatings 2023, 13(9), 1567; https://doi.org/10.3390/coatings13091567 - 7 Sep 2023

Cited by 1 | Viewed by 780

Abstract

To overcome challenging service conditions, a groundbreaking thermoset, “Super-Tough Resin” (STR), has been specifically designed for steel bridge deck paving. Currently, investigations of paving thermosets mainly focus on cured materials. Detailed investigations of the curing process and its impact on the evolving properties [...] Read more.

To overcome challenging service conditions, a groundbreaking thermoset, “Super-Tough Resin” (STR), has been specifically designed for steel bridge deck paving. Currently, investigations of paving thermosets mainly focus on cured materials. Detailed investigations of the curing process and its impact on the evolving properties of STR are lacking. Therefore, this study aims to explore the curing kinetics and the performance evolution of STR. Specifically, spectroscopy test, time sweep, linear viscoelastic region, and weight loss tests were conducted. Our results show that the curing degrees increase significantly with the curing durations and temperatures at the initial stage. When cured for 10 h, the curing degrees at four temperatures all exceed 80%. Then, a kinetic model with an nth-order of 1.551 was established. Upon increasing the temperature from 35 to 80 °C, the gel point time decreases from 480 to 189 min but the corresponding curing degree remains constant at 75.73%. When curing time is increased from 2.5 to 4 h, the linear viscoelastic regions decrease from 20% to 3%. Finally, after 400 h, the weight losses of STR at 35 and 80 °C are about 8% and 20%, respectively. These outcomes are beneficial to understanding the dynamic curing behaviors of STR and similar thermosets. Full article

(This article belongs to the Special Issue Surface Engineering and Mechanical Properties of Building Materials)

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21 pages, 5543 KiB

Open AccessArticle

An Evaluation of Asphalt Mixture Crack Resistance and Identification of Influential Factors

by Liheng Shu, Fujian Ni, Hui Du and Yajin Han

Coatings 2023, 13(8), 1382; https://doi.org/10.3390/coatings13081382 - 7 Aug 2023

Viewed by 983

Abstract

The crack resistance of asphalt pavement mixtures directly impact pavement service condition and pavement distress. And characterizing the crack resistance of a pavement mixture can reflect the crack resistance potential of asphalt pavement. This study analyzes several representative highway sections based on time, [...] Read more.

The crack resistance of asphalt pavement mixtures directly impact pavement service condition and pavement distress. And characterizing the crack resistance of a pavement mixture can reflect the crack resistance potential of asphalt pavement. This study analyzes several representative highway sections based on time, material, and service conditions to identify the mixture type of three layers. Semi-circular bending tests are conducted at 15 °C, and load–displacement curves are recorded. Factor independence analysis is performed, and combinations showcasing the cracking performance of the surface layer, middle layer, and bottom layer are selected. Analysis of variance (ANOVA) evaluating the indices versus selected factors for the three layers identifies significant influencing factors, and the crack resistance is analyzed based on these significant factors. The crack resistance of the middle layer with the highest truck loads is significantly lower than the two other lanes and the shoulder. Transverse crack spacing (TCS) can be used to directly evaluate the crack resistance of the mixture. The Factor dots upper rate (FUDR) and absolute Factor dots upper rate (absFUDR) indices are introduced to quantify the percentage deviation of a factor specimen from the average crack resistance index–fracture energy ratio, indicating whether the crack curve becomes sharper or flatter. The factor dots upper rate index is then applied to characterize the factors, and the results are reasonable. It is found only on the surface and middle layers that the service age has significant impacts on crack resistance, the Transverse crack spacing has significant impacts on crack resistance index, and the Factor dots upper rate can identify the brittleness of mixtures with different factors. Full article

(This article belongs to the Special Issue Surface Engineering and Mechanical Properties of Building Materials)

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17 pages, 4379 KiB

Open AccessArticle

Evaluation of Curing Effects on Bitumen Emulsion-Based Cold In-Place Recycling Mixture Considering Field-Water Evaporation and Heat-Transfer Conditions

by Zili Zhao, Fujian Ni, Junqiu Zheng, Zhiqiang Cheng and Shengjia Xie

Coatings 2023, 13(7), 1204; https://doi.org/10.3390/coatings13071204 - 5 Jul 2023

Cited by 3 | Viewed by 949

Abstract

The strength growth of a bitumen emulsion-based cold in-place recycling asphalt mixture (BE-CIR) is time-dependent and time-consuming due to the addition of water. There is a great difference between the curing conditions of specification in the laboratory and the in situ conditions, which [...] Read more.

The strength growth of a bitumen emulsion-based cold in-place recycling asphalt mixture (BE-CIR) is time-dependent and time-consuming due to the addition of water. There is a great difference between the curing conditions of specification in the laboratory and the in situ conditions, which often leads to a great discrepancy between the results of lab specimens and the field cores. The main objective of this paper is to evaluate the curing effect on laboratory BE-CIR considering field-water evaporation and heat-transfer conditions. Four different curing methods were designed by using different combinations of waterproof layers, heat insulation layers, and variable temperature modes. The variations in temperature indexes, moisture content, air void, and indirect tensile strength (ITS) with curing time were tested, and the mutual influence of these indicators was analyzed. Furthermore, the results of the laboratory samples were compared with the field cores. Testing results show that the performance of the BE-CIR mixture is significantly different from that with no treatment, which is manifested as higher moisture content and lower air void and ITS under the same curing time. The internal temperature of the mixture is the main factor affecting the variation of moisture content, especially on the first curing day. The air void of the mixture has a strong linear relationship with the moisture content. Moisture content and ITS under different curing methods showed similar trends and could be divided into two stages. Taking the field cores as a benchmark, it can be concluded that the field-water evaporation condition should be considered in the setting of indoor curing methods, while the heat transfer could not. Full article

(This article belongs to the Special Issue Surface Engineering and Mechanical Properties of Building Materials)

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19 pages, 5416 KiB

Open AccessArticle

Study on Soil Corrosion Resistance Reinforced with Reactive Powder Concrete in Chloride Environment

by Haozhen Wang, Xin Cai, Xi Peng, Hui Wang and Pengqian Wang

Coatings 2023, 13(7), 1134; https://doi.org/10.3390/coatings13071134 - 22 Jun 2023

Viewed by 1202

Abstract

The accumulation of residue soil (generally composed of soil, residue, or mud consolidation) is one of the important causes of damage to the environment limiting urban development. At present, the recycling rate of residue soil in developed countries is as high as 90%, [...] Read more.

The accumulation of residue soil (generally composed of soil, residue, or mud consolidation) is one of the important causes of damage to the environment limiting urban development. At present, the recycling rate of residue soil in developed countries is as high as 90%, while in China it is less than 5%. In marine construction, reinforced concrete often suffers from corrosion, which leads to a decrease in the service life and durability of the structure. Reactive powder concrete (RPC) with high strength and good corrosion resistance can solve these problems. In order to efficiently dispose of residue soil, protect the environment, and promote urbanization development, this study uses residue soil as a raw material to replace some cement in RPC, and studies the corrosion resistance of it (under dry–wet alternations and freeze–thaw cycles). In this study, five types of reinforced RPC with different residue soil contents (0%, 2.5%, 5%, 7.5%, and 10%) are prepared. Firstly, the working performance of blank freshly mixed residue soil RPC slurry is analyzed. Then, the corrosion resistance of residue-soil-reinforced RPC under the dry–wet alternations with 3% NaCl and freeze–thaw cycles is analyzed through parameters such as mass loss rate, electrical resistivity, ultrasonic velocity, AC impedance spectroscopy, and Tafel. The results show that under the dry–wet alternations, when the residue soil content is 10%, the corrosion rate and corrosion depth of the residue-soil-reinforced RPC are the minimum, at 43,744.84 g/m²h and 640.22 mm/year, respectively. Under the freeze–thaw cycles, the corrosion rate and corrosion depth of the 10% residue soil content group are higher than that of the 5%, being 52,592.87 g/m²h and 769.71 mm/year, respectivley. Compared to the other groups, the reinforced RPC with 10% residue soil content shows good corrosion resistance in both dry–wet alternations and freeze–thaw cycles. Replacing some of the cement in RPC with residual soil to control the amount of residual soil at 10% of the total mass of RPC can effectively improve the corrosion resistance of residue-soil-reinforced RPC and maximize the consumption of residue soil. This plan provides a feasible method for residue soil treatment in the construction industry, while also providing inspiration for research on the corrosion resistance of concrete in marine buildings. Full article

(This article belongs to the Special Issue Surface Engineering and Mechanical Properties of Building Materials)

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15 pages, 3567 KiB

Open AccessArticle

Investigation of the Effect of Filler on Cohesive Bond Strength of Asphalt Mastic Using Binder Bond Strength (BBS) Test

by Xiang Ma, Jinquan Kan, Song Liu, Mingyuan Tu and Dongjia Wang

Coatings 2023, 13(6), 1001; https://doi.org/10.3390/coatings13061001 - 28 May 2023

Cited by 4 | Viewed by 1242

Abstract

Water damage leads to spalling and loosening of asphalt pavement, which is ultimately due to a reduction in the bond strength of the asphalt mastic. The filler, as an important component of the asphalt mastic, has a great impact on the various properties [...] Read more.

Water damage leads to spalling and loosening of asphalt pavement, which is ultimately due to a reduction in the bond strength of the asphalt mastic. The filler, as an important component of the asphalt mastic, has a great impact on the various properties of the asphalt mastic and even the asphalt mix itself. Therefore, it is important to study the influence of fillers on the performance of asphalt mastic. In this paper, the various properties of twelve types of fillers, including mineral powder, mineral powder partially replaced with cement, slaked lime, and recycled powder, and their effects on the bond strength of asphalt mastic are investigated. Binder bond strength (BBS) was used to evaluate the performance of the different asphalt mastics. The moisture resistance of the asphalt mastic was evaluated by measuring the bond strength of the asphalt mastic after treatment in a water bath. A grey correlation analysis was then carried out to derive the relationship between the filler index and the bond strength of the asphalt mastic. The results show that the addition of slaked lime and cement helped to improve the moisture resistance of the asphalt mastic. The fineness modulus and other indicators have a great influence on the bond strength of asphalt mastic. The interaction between hydrothermal coupling and filler type has a non-negligible effect on the moisture resistance of the asphalt mastic. Full article

(This article belongs to the Special Issue Surface Engineering and Mechanical Properties of Building Materials)

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12 pages, 3810 KiB

Open AccessArticle

Utilization of Fly Ash and Red Mud in Soil-Based Controlled Low Strength Materials

by Xianghui Kong, Gaoqiang Wang, Shu Rong, Yunpeng Liang, Mengmeng Liu and Yanhao Zhang

Coatings 2023, 13(5), 893; https://doi.org/10.3390/coatings13050893 - 9 May 2023

Cited by 1 | Viewed by 1298

Abstract

To reduce the harm caused by industrial solid waste to the environment, and solve the problem of excavated soil disposal in buried pipeline management projects, this study proposes a method to produce soil-based controlled low strength materials (CLSM) by using industrial solid wastes [...] Read more.

To reduce the harm caused by industrial solid waste to the environment, and solve the problem of excavated soil disposal in buried pipeline management projects, this study proposes a method to produce soil-based controlled low strength materials (CLSM) by using industrial solid wastes (including fly ash and red mud) as partial replacements for cement. The properties of CLSM were characterized in terms of flowability, unconfined compressive strength, phase composition and microstructure. The test results showed that fly ash could significantly improve the flowability of CLSM, while red mud had more advantages for the strength development. When 20% fly ash and 30% red mud were combined to replace cement, the fluidity of CLSM was 248 mm, and the unconfined compressive strength (UCS) at 3, 7 and 28 days was 1.08, 1.49 and 3.77 MPa, respectively. The hydration products of CLSM were mainly calcium silicate hydrate gels, ettringite and calcite. Fly ash provided nucleation sites for cement hydration, while the alkali excitation of red mud promoted the dissolution of SiO₂ and Al₂O₃ in fly ash. The filling and gelation of hydration products make the microstructure dense, which improves the mechanical properties of the mixture. Full article

(This article belongs to the Special Issue Surface Engineering and Mechanical Properties of Building Materials)

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14 pages, 7936 KiB

Open AccessArticle

The Influence of CO₂-Cured Incinerated Waste Fly Ash on the Performance of Reactive Powder Concrete

by Jianhu Xu, Hui Wang, Wanzhen Wang and Feiting Shi

Coatings 2023, 13(4), 709; https://doi.org/10.3390/coatings13040709 - 31 Mar 2023

Cited by 4 | Viewed by 1433

Abstract

Incinerated waste fly ash is a toxic solid, which can cause serious harm to the environment. CO₂-cured incinerated waste fly ash may be useful in decreasing the toxicity of waste fly ash and improving the corresponding mechanical properties of cement-based material [...] Read more.

Incinerated waste fly ash is a toxic solid, which can cause serious harm to the environment. CO₂-cured incinerated waste fly ash may be useful in decreasing the toxicity of waste fly ash and improving the corresponding mechanical properties of cement-based material with incinerated waste fly ash. Meanwhile, this technology can play a certain role in reducing the content of CO₂ in the atmosphere. In this study, the influence of CO₂-cured incinerated waste fly ash on the rheological parameters (the slump flow and plastic viscosity) and the setting time of fresh reactive powder cement concrete (RPC) is investigated. The flexural and compressive strengths of hardened RPC standard cured for 1 day, 3 days, and 28 days are measured. The leached amounts of Cr and Zn immersed in water for 6 months are measured. The scanning electron microscope photos, thermogravimetric analysis curves, and mercury intrusion curves are obtained. Our results show that the slump flow, the setting time, and the flexural and compressive strengths increased, and the plastic viscosity decreased by adding the waste fly ash with the maximum varying rates of 12.1%, 41.7%, 41.3%, and 61.2%, respectively. CO₂ curing on the waste fly ash can increase the setting time and the flexural and compressive strengths with the maximum varying rates of 19.2%, 13.1%, and 14.2%. The effect of CO₂-cured waste fly ash on the mechanical strengths of RPC is quite limited. Full article

(This article belongs to the Special Issue Surface Engineering and Mechanical Properties of Building Materials)

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13 pages, 4989 KiB

Open AccessArticle

Investigation of the Wet and Thermal Conditions Effect on the Micro-Scale Characteristics of Interfacial Transition Zone of Porous Asphalt Mixture

by Dong Zhao, Xiang Ma, Hao Wang and Chaolin Zhang

Coatings 2023, 13(3), 566; https://doi.org/10.3390/coatings13030566 - 6 Mar 2023

Cited by 2 | Viewed by 1213

Abstract

Complex environmental factors can significantly influence the micro-properties of porous asphalt (PA) mixture. Therefore, the effects of short-term and long-term thermal aging and moisture immersion on the micromechanics properties, micro-morphology, and chemical element distributions of the interfacial transition zone (ITZ) of PA mixture [...] Read more.

Complex environmental factors can significantly influence the micro-properties of porous asphalt (PA) mixture. Therefore, the effects of short-term and long-term thermal aging and moisture immersion on the micromechanics properties, micro-morphology, and chemical element distributions of the interfacial transition zone (ITZ) of PA mixture were studied to reveal the mechanisms by which environmental degradation impact performance by means of nanoindentation (NI), backscattering scanning electron microscope (BSEM), and energy-dispersive X-ray spectroscopy (EDS) analysis techniques. The results show that the ITZ is not the softest part of the PA mixture, and the order of modulus is aggregate > ITZ > asphalt mastic. ITZ thickness is about 10–20 μm. Thermal aging has negligible effect on the width of ITZ. With increasing aging degree, the asphalt mastic and ITZ modulus increase, while water damage reduces the modulus of ITZ and slightly increases the width of ITZ. Thermal aging has little effect on the morphology of ITZ, while water damage will lead to microcracks and micropores in ITZ. Compared with thermal aging, water damage has a greater effect on the morphology of ITZ and leads to softening of the interfacial transition zone and asphalt mastic phase. The width of ITZ obtained by EDS line scanning is basically consistent with that of nanoindentation. Overall, external environmental factors have a more significant effect on the mechanical properties than the micro-morphology of ITZ. The outcomes of this research provide a better understanding of the impact of the service environment on the microscopic characteristics of PA mixture. Full article

(This article belongs to the Special Issue Surface Engineering and Mechanical Properties of Building Materials)

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18 pages, 6340 KiB

Open AccessArticle

Long-Term In Situ Performance Evaluation of Epoxy Asphalt Concrete for Long-Span Steel Bridge Deck Pavement

by Yajin Han, Zhu Zhang, Jiahao Tian, Fujian Ni and Xingyu Gu

Coatings 2023, 13(3), 545; https://doi.org/10.3390/coatings13030545 - 2 Mar 2023

Cited by 6 | Viewed by 1558

Abstract

Suitable evaluation of distress is beneficial to understanding the in situ performance of deck pavement. This study attempts to evaluate the long-term in situ performance of American ChemCo epoxy asphalt concrete on the Xihoumen Bridge (XHMB) after 12 years of service. The traditional [...] Read more.

Suitable evaluation of distress is beneficial to understanding the in situ performance of deck pavement. This study attempts to evaluate the long-term in situ performance of American ChemCo epoxy asphalt concrete on the Xihoumen Bridge (XHMB) after 12 years of service. The traditional performance indexes were adopted to reveal the performance of XHMB. Then, based on the typical distresses, a new pavement performance index (PPI) was proposed to characterize the authentic distress condition. Finally, the performance evaluation and evolution were conducted. According to the results, the rutting depth indexes and riding quality indexes of all lanes are higher than 97 and 94, respectively. The pavement condition indexes of the pass lanes and drive lanes in 2021 are greater than 94 and 86, respectively, which is contradictory to the distribution of numerous distresses on the pavement. According to the PPI results, the PPIs of the down direction pass lane are mostly 100. However, for the down direction drive lane, the PPIs of about 30% of segments are below 80 or 60. Finally, based on the limited data, the distress of American ChemCo epoxy asphalt concrete may initiate after serving for 4–5 years and then escalate after about 10 years. Full article

(This article belongs to the Special Issue Surface Engineering and Mechanical Properties of Building Materials)

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11 pages, 3665 KiB

Open AccessArticle

Effect of Strain Levels on the Corrosion Resistance of an Enamel-Coated Steel Rebar

by Fujian Tang, Hao Cui, Gang Li and Shangtong Yang

Coatings 2023, 13(3), 510; https://doi.org/10.3390/coatings13030510 - 25 Feb 2023

Viewed by 1535

Abstract

The effect of strain levels on the corrosion resistance of an enamel-coated steel rebar is experimentally investigated in this study. Enamel coating was applied on the surface of a steel rebar by using the wet process. A strain gauge was attached on the [...] Read more.

The effect of strain levels on the corrosion resistance of an enamel-coated steel rebar is experimentally investigated in this study. Enamel coating was applied on the surface of a steel rebar by using the wet process. A strain gauge was attached on the surface of the coated steel rebar to record the strain levels and a plastic container was mounted for electrochemical corrosion tests. A stress-corrosion test set-up was designed to conduct corrosion and tensile tests simultaneously. The strain levels considered include 0 µε, 300 µε, 600 µε, 900 µε and 1200 µε, and the electrochemical techniques employed include open circuit potential, linear polarization resistance and electrochemical impedance spectroscopy. The microstructure of the enamel coating was also examined with scanning electron microscopy. Results show that the enamel coating has a thickness of ~150 µm, and there are some air bubbles in the coating. The average corrosion current density of the uncoated steel rebar decreases from 18.64 µA/cm² to 14.39 µA/cm² in NaCl solution due to the generation of corrosion products. The corrosion current density of the enamel-coated steel rebar gradually increases from 0.49 µA/cm² when the strain is zero to 0.65 µA/cm² as strain reaches 1200 µε, which is almost 40 times lower than that of the uncoated steel rebar. Impedance spectrum results show that the corrosion resistance of enamel coating decreases with an increase in the tensile strain level; however, it still protects steel rebar from corrosion to some degree. Full article

(This article belongs to the Special Issue Surface Engineering and Mechanical Properties of Building Materials)

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13 pages, 5123 KiB

Open AccessArticle

Study on Key Mechanical Parameters of High-Strength Grouting Material

by Yueran Zhang, Baoyong Cao, Heng Zhang, Xiong Zhang and Yan He

Coatings 2023, 13(2), 440; https://doi.org/10.3390/coatings13020440 - 15 Feb 2023

Cited by 1 | Viewed by 1101

Abstract

In order to better design and calculate in infrastructures, it is necessary to clarify the key mechanical parameters of structural materials, such as axial compressive strength, elastic modulus and Poisson’s ratio. High-strength grouting material (HSGM) have begun to be used as structural materials [...] Read more.

In order to better design and calculate in infrastructures, it is necessary to clarify the key mechanical parameters of structural materials, such as axial compressive strength, elastic modulus and Poisson’s ratio. High-strength grouting material (HSGM) have begun to be used as structural materials with the development of large and complex structures. A large number of test dates were used to analyze the relationship between the axial compressive strength and the cubic compressive strength of HSGM in the paper. ABAQUS software was used to model the specimens of axial compressive strength, and the strain cloud maps of concrete and HSGM were compared and analyzed. By considering HSGM as two-phase (sand and paste) composites, the relationship between elastic modulus of HSGM and mechanical parameters of component materials was derived, and the test results of the mechanical properties of HSGM with different ratios of sand to cement were used for verification. The test results show that the axial compressive strength of the HSGM is closer to the cubic strength than that of the concrete material, which accords with the finite element analysis results. The elastic modulus of high-strength grouting material conforms to the theoretical derivation of two-phase material. The material composition is one of the main factors affecting the elastic modulus. Poisson’s ratio range of high-strength grouting material is 0.25 ± 0.01 by statistical analysis. Full article

(This article belongs to the Special Issue Surface Engineering and Mechanical Properties of Building Materials)

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15 pages, 5076 KiB

Open AccessArticle

Investigation of Factors Affecting the Intermediate-Temperature Cracking Resistance of In-Situ Asphalt Mixtures Based on Semi-Circular Bending Test

by Duo Xu, Fujian Ni, Hui Du, Zili Zhao, Jingling Wang and Sheng Chen

Coatings 2023, 13(2), 384; https://doi.org/10.3390/coatings13020384 - 7 Feb 2023

Cited by 1 | Viewed by 1540

Abstract

Cracking is one of the main distresses in asphalt pavement. At present, few studies have been conducted on the cracking performance of asphalt mixtures from the field due to the difficulty of sample collection. Therefore, this study aims to assess the cracking resistance [...] Read more.

Cracking is one of the main distresses in asphalt pavement. At present, few studies have been conducted on the cracking performance of asphalt mixtures from the field due to the difficulty of sample collection. Therefore, this study aims to assess the cracking resistance of in-service asphalt pavement at intermediate temperature using a large number of field cores in Jiangsu province, China. A semi-circular bending (SCB) test at 25 °C was conducted on field-cored samples covering three asphalt layers from 16 in-service road sections that represent a combination of influencing factors, including air void, mixture type, service age, cumulative number of equivalent single-axle loads (ESALs), and overload rate. The flexibility index (FI) and tensile strength were calculated from the experimental data as cracking performance evaluation indices. According to the analysis of variance results, at the top layer, ESALs and service age had a strong influence on cracking resistance. The decline rate of FI became slower with increasing ESALs. The most rapid decline in crack resistance with service age occurred on medium-traffic-level sections that served for over 14 years. At the middle layer, the overload rate replaced service age as a significant factor for FI. At the bottom layer, the air void was the only significant factor affecting the cracking resistance. In general, as the depth of layer increased, the effect of traffic load and service age decreased, whereas the effect of material properties increased. In addition, the FI and tensile strength were more sensitive to traffic load and air void, respectively. Full article

(This article belongs to the Special Issue Surface Engineering and Mechanical Properties of Building Materials)

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