Pub Date : 2024-09-11DOI: 10.1617/s11527-024-02456-1
Duygu Demirtürk, Hande Isik Ozturk, Murat Guler
The structural performance of asphalt concrete is highly dependent on its thermal properties, especially in regions where daily or seasonal temperature variations are significant. In mechanistic design methods, thermal properties (specific heat, thermal conductivity, and coefficient of thermal expansion) are necessary to estimate the thermal behavior of asphalt concrete. However, the measurement of these properties is still a challenge, not only because of the heterogeneous structure of asphalt concrete but also because of the limitations imposed by the size of the test samples and the reliability of the measurement methods. In this study, a practical method, the Transient Plane Source (TPS), is proposed to measure the thermal conductivity of laboratory-produced asphalt concrete samples. To determine how thermal conductivity is affected by the maximum aggregate size, air voids, and aggregate source, a series of asphalt mixtures are compacted using the Superpave gyratory compactor to produce test samples. To determine the possible relationship between microstructural and thermal properties, which has not been investigated in previous studies, an image analysis is also performed to calculate the number of contact points and the total aggregate area in each sample. The statistical analyses show that all mixture properties, i.e., maximum aggregate size, air void content, and aggregate source, are significant, with the aggregate source having the greatest influence on the thermal conductivity of the samples. It is also shown that the TPS method is sensitive to the properties of the contact area, which significantly affects the reliability of the measurements.
{"title":"Investigation of the influence of mixture and microstructural properties on the thermal conductivity of asphalt concrete using the transient heat transfer method","authors":"Duygu Demirtürk, Hande Isik Ozturk, Murat Guler","doi":"10.1617/s11527-024-02456-1","DOIUrl":"https://doi.org/10.1617/s11527-024-02456-1","url":null,"abstract":"<p>The structural performance of asphalt concrete is highly dependent on its thermal properties, especially in regions where daily or seasonal temperature variations are significant. In mechanistic design methods, thermal properties (specific heat, thermal conductivity, and coefficient of thermal expansion) are necessary to estimate the thermal behavior of asphalt concrete. However, the measurement of these properties is still a challenge, not only because of the heterogeneous structure of asphalt concrete but also because of the limitations imposed by the size of the test samples and the reliability of the measurement methods. In this study, a practical method, the Transient Plane Source (TPS), is proposed to measure the thermal conductivity of laboratory-produced asphalt concrete samples. To determine how thermal conductivity is affected by the maximum aggregate size, air voids, and aggregate source, a series of asphalt mixtures are compacted using the Superpave gyratory compactor to produce test samples. To determine the possible relationship between microstructural and thermal properties, which has not been investigated in previous studies, an image analysis is also performed to calculate the number of contact points and the total aggregate area in each sample. The statistical analyses show that all mixture properties, i.e., maximum aggregate size, air void content, and aggregate source, are significant, with the aggregate source having the greatest influence on the thermal conductivity of the samples. It is also shown that the TPS method is sensitive to the properties of the contact area, which significantly affects the reliability of the measurements.</p>","PeriodicalId":691,"journal":{"name":"Materials and Structures","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142220017","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-10DOI: 10.1617/s11527-024-02438-3
Grace A. Blackshaw, Jessica C. Forsdyke, Janet M. Lees
In a variety of applications, such as in tidal zones, abutments of bridges and concrete tunnel linings, reinforced concrete is exposed to both carbonation and chloride ingress. The exposure can be either simultaneous or sequential. However, durability design rarely considers synergistic effects due to carbonation and chloride ingress, even though this may have detrimental consequences for performance. Comparative implications of exposure sequence across different concrete compositions are also unknown. In this study, an experimental investigation on the effects of the sequence of carbonation and chloride ingress was conducted, using two concretes which differ by 50% cement replacement with ground granulated blast furnace slag (GGBS). Specimens were exposed to a combination of 10% CO2 accelerated carbonation and immersion in 3% sodium chloride solution, in either sequence, and compared with companion samples subjected to only one of these aggressive environments. The extent of carbonation was measured using phenolphthalein indicator solution, while silver nitrate and Rapid Chloride Testing provided indicators of the chloride ingress. For both concrete mixes, specimens with prior chloride ingress exhibited a decreased rate of carbonation when compared to specimens with no prior exposure. Conversely, specimens with prior carbonation displayed an increased rate of chloride ingress compared to non-carbonated counterparts and a step in the acid soluble chloride content in the region of the carbonation front. The concrete composition appeared to play a role since a greater increase in chloride diffusion coefficient due to prior carbonation was observed in the mix with 50% GGBS replacement than the mix without. These findings suggest that in concrete structures exposed to air and saline environments, the effects of sequential exposure should be characterised.
{"title":"Effects of exposure sequence and GGBS cement replacement on performance of concrete subjected to carbonation and chloride ingress","authors":"Grace A. Blackshaw, Jessica C. Forsdyke, Janet M. Lees","doi":"10.1617/s11527-024-02438-3","DOIUrl":"https://doi.org/10.1617/s11527-024-02438-3","url":null,"abstract":"<p>In a variety of applications, such as in tidal zones, abutments of bridges and concrete tunnel linings, reinforced concrete is exposed to both carbonation and chloride ingress. The exposure can be either simultaneous or sequential. However, durability design rarely considers synergistic effects due to carbonation and chloride ingress, even though this may have detrimental consequences for performance. Comparative implications of exposure sequence across different concrete compositions are also unknown. In this study, an experimental investigation on the effects of the sequence of carbonation and chloride ingress was conducted, using two concretes which differ by 50% cement replacement with ground granulated blast furnace slag (GGBS). Specimens were exposed to a combination of 10% CO<sub>2</sub> accelerated carbonation and immersion in 3% sodium chloride solution, in either sequence, and compared with companion samples subjected to only one of these aggressive environments. The extent of carbonation was measured using phenolphthalein indicator solution, while silver nitrate and Rapid Chloride Testing provided indicators of the chloride ingress. For both concrete mixes, specimens with prior chloride ingress exhibited a decreased rate of carbonation when compared to specimens with no prior exposure. Conversely, specimens with prior carbonation displayed an increased rate of chloride ingress compared to non-carbonated counterparts and a step in the acid soluble chloride content in the region of the carbonation front. The concrete composition appeared to play a role since a greater increase in chloride diffusion coefficient due to prior carbonation was observed in the mix with 50% GGBS replacement than the mix without. These findings suggest that in concrete structures exposed to air and saline environments, the effects of sequential exposure should be characterised.</p>","PeriodicalId":691,"journal":{"name":"Materials and Structures","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142220019","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-10DOI: 10.1617/s11527-024-02455-2
Alessandro P. Fantilli, Barbara Frigo, Farmehr M. Dehkordi
The use of ice as structural material has two main concerns: the low strength and the brittle failure of the structures. With the aim of finding a solution to these problems, an experimental campaign, performed on fiber-reinforced ice (FRI) samples, made with plain water and bio-fibers, is presented in this paper. In total, 12 ice prisms were cast at − 18 °C with a different content of fibers, and then tested in three-point bending and uniaxial compression. Test results indicate that the presence of a reinforcement increases both flexural and compressive strength with respect to plain ice. Moreover, FRI is a tougher material, as multiple cracking and deflection hardening behavior can be observed in the flexural tests. However, the mechanical performances of plain ice are not always enhanced by the fiber-reinforcement. Therefore, an empirical model, capable of predicting the optimal content of bio-fibers, is also proposed.
使用冰作为结构材料有两个主要问题:结构强度低和脆性破坏。为了找到解决这些问题的方法,本文介绍了一项针对纤维增强冰(FRI)样品的实验活动,该样品由清水和生物纤维制成。总共在零下 18 °C 的温度下浇铸了 12 块不同纤维含量的冰棱柱,然后进行了三点弯曲和单轴压缩测试。测试结果表明,与普通冰相比,增强材料的存在提高了抗弯强度和抗压强度。此外,FRI 是一种韧性更强的材料,因为在抗弯试验中可以观察到多重开裂和挠曲硬化行为。然而,普通冰的机械性能并不总是因为纤维增强而得到提高。因此,我们还提出了一个能够预测生物纤维最佳含量的经验模型。
{"title":"Optimal content of bio-fibers in structural ice","authors":"Alessandro P. Fantilli, Barbara Frigo, Farmehr M. Dehkordi","doi":"10.1617/s11527-024-02455-2","DOIUrl":"https://doi.org/10.1617/s11527-024-02455-2","url":null,"abstract":"<p>The use of ice as structural material has two main concerns: the low strength and the brittle failure of the structures. With the aim of finding a solution to these problems, an experimental campaign, performed on fiber-reinforced ice (FRI) samples, made with plain water and bio-fibers, is presented in this paper. In total, 12 ice prisms were cast at − 18 °C with a different content of fibers, and then tested in three-point bending and uniaxial compression. Test results indicate that the presence of a reinforcement increases both flexural and compressive strength with respect to plain ice. Moreover, FRI is a tougher material, as multiple cracking and deflection hardening behavior can be observed in the flexural tests. However, the mechanical performances of plain ice are not always enhanced by the fiber-reinforcement. Therefore, an empirical model, capable of predicting the optimal content of bio-fibers, is also proposed.</p>","PeriodicalId":691,"journal":{"name":"Materials and Structures","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142220018","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-05DOI: 10.1617/s11527-024-02449-0
Tao Wang, Jiaxu Ma, Jie Ma, Xiaopei Cai, Yaping Cui, Ruilin Ning, Jin Li
Bitumen-rubber composite binder (BRCB) has great potential to construct durable road pavement infrastructures that can withstand the environmental aging. However, the aging behavior of BRCB has not been fully investigated so far, especially from the perspective of biphase system with the phase interactions consideration. Therefore, this study investigated the progressive aging behavior of BRCB in terms of separate bitumen phase and rubber phase as well as the biphase interactions, to further understand the mechanisms behind. The results showed that the bitumen phase gradually dominated rheological performance of BRCB with the progressive aging. On the contrast, the fatigue resistance of BRCB was constantly controlled by its rubber phase in the aging process. Secondly, the rubber phase gradually dissolved during the aging with a decrease in the crosslinking density, although the change rate slowed down with the aging duration. The breakdown pattern of rubber structure was further identified as the simultaneous scission of crosslinking bonds and main chains. Besides, biphase interactions during progressive aging primarily included the absorption of light components from bitumen phase into rubber phase and the release of long rubber molecular chains and fillers from rubber phase into bitumen phase. Overall, the progressive aging of BRCBs can be considered as the combined effect of the secondary bitumen-rubber biphase interactions after the first-stage production and thermal oxidation of the bitumen phase.