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Ceramsite concrete is one of the most widely used lightweight concretes at present. Although mechanical properties of ceramsite concrete have been extensively discussed, its permeability characteristics are neglected in previous studies. Considering the importance of permeability resistance to concrete, the permeability grade and residual compressive strength after permeability of ceramsite concrete are analyzed in this study. The influence of ceramsite content and size on the permeability grade and residual strength of ceramsite concrete were investigated by the orthogonal experimental method. To further understand the above influence, an improved Bayesian framework for small sample data is also established to analyze the permeability grade and residual strength. Results show that the water–binder ratio and the content of 20–30 mm ceramsite aggregates are the most and least significant influencing factors affecting the permeability characteristics, respectively. The 5–10 mm and 10–20 mm ceramsite aggregates play secondary roles. Increasing 5–10 mm and 10–20 mm ceramsite aggregates is not helpful for improving the permeability resistance of ceramsite concrete. Compared with the orthogonal method, the proposed Bayesian framework is a useful tool for revealing the effects of various factors, which can cut the time cost and provide parameter visualization for the analysis process. Results show that the permeability resistance and residual strength of ceramsite concrete are improved significantly under optimal conditions. The permeability grade and residual strength are increased 200% and 80.3%, respectively. In addition, the residual strength may be more suitable for evaluating the permeability characteristics than the permeability grade. [ABSTRACT FROM AUTHOR]

Fly ash–slag-based alkali-activated materials have excellent mechanical performance and a low carbon footprint, and they have emerged as a promising alternative to Portland cement. Therefore, replacing traditional Portland cement with slag–desulfurization gypsum-based alkali-activated materials will help to make better use of the waste, protect the environment, and improve the materials' performance. In order to better understand it and thus better use it in engineering, it needs to be characterized for performance and compositional design. This study developed a novel framework for performance characterization and composition design by combining Categorical Gradient Boosting (CatBoost), simplicial homology global optimization (SHGO), and laboratory tests. The CatBoost characterization model was evaluated and discussed based on SHapley Additive exPlanations (SHAPs) and a partial dependence plot (PDP). Through the proposed framework, the optimal composition of the slag–desulfurization gypsum-based alkali-activated materials with the maximum flexural strength and compressive strength at 1, 3, and 7 days is Ca(OH)2: 3.1%, fly ash: 2.6%, DG: 0.53%, alkali: 4.3%, modulus: 1.18, and W/G: 0.49. Compared with the material composition obtained from the traditional experiment, the actual flexural strength and compressive strength at 1, 3, and 7 days increased by 26.67%, 6.45%, 9.64%, 41.89%, 9.77%, and 7.18%, respectively. In addition, the results of the optimal composition obtained by laboratory tests are very close to the predictions of the developed framework, which shows that CatBoost characterizes the performance well based on test data. The developed framework provides a reasonable, scientific, and helpful way to characterize the performance and determine the optimal composition for civil materials. [ABSTRACT FROM AUTHOR]

The orthogonal experimental method is currently the most commonly used tool for determining an appropriate composition of modified asphalt binders. However, it cannot automatically output a reasonable composition when dealing with multi objective optimization and must go through the process of repeated comparison manually. Obviously, the accuracy and efficiency of the orthogonal method are easily affected by subjective factors, which grow tremendously as the sizes of the experiments and data increase. In order to enrich the design method, the objective of this study is to develop a new framework to determine reasonable compositions of modified asphalt binder automatically, accurately, and efficiently. Hence, a data-driven multiobjective optimization method is established based on the experimental data, reduced order model (ROM), and simplicial homology global optimization (SHGO). The ROM is utilized to characterize the complex relationship between material composition and the corresponding performance. The average relative errors between experimental results and prediction values of the ROM are less than 1.5%, and the maximum relative errors are less than 8.7%. The SHGO is selected to determine the reasonable compositions in the global space. Finally, the properties and costs of the SBS-modified asphalt binders, orthogonal-based modified asphalt binder, and ROM-SHGO-based modified asphalt binder are tested to verify the feasibility of the developed method. The ROM-SHGO-based modified asphalt binder has the lowest cost under the premise of similar performance when taking the cost as the constraint. The developed ROM-SHGO method provides feasible, useful, and promising tools for composition design of modified asphalt binder based on laboratory test data. [ABSTRACT FROM AUTHOR]

During the course of building asphalt pavement, a lack of quality control will lead to the abandonment of the asphalt mixtures. One of the most common problems with asphalt pavement is rutting. Improving the construction's quality is an important measure to reduce rutting. The purpose is to ensure the high-temperature durability of asphalt mixtures during the construction workflow to reduce the waste of asphalt mixtures, as well as to provide a methodology for the current monitoring of the quality based on the building information modeling (BIM). Rutting resistance was appraised utilizing the static uniaxial creep examination. Oblique photography technology was used to obtain terrain data. The software of Revit 2016 was used to build the spatial model of highways and bridges. The results show that the size distribution of particles, the asphalt proportion, and the forming specimen's temperature are the vital elements influencing the high-temperature behavior. The gradation was identified as the most important factor. The second was the asphalt binder content. Gradation variation should be given more consideration during paving using asphalt mixtures. Furthermore, the developed BIM platform can also monitor rutting resistance to reduce rework during construction. [ABSTRACT FROM AUTHOR]

High-modulus asphalt mixtures (HMAM) have been widely used in asphalt pavement in high-temperature areas of China, owing to their advantages in rutting and fatigue resistance. However, moisture and temperature interdependently determine the degradation of pavement performance of the HMAM, owing to the unique climatic conditions in summer in some high-temperature areas of China. There were few studies on the rutting and fatigue properties of the HMAM under the combined action of moisture contents and temperatures. Hence, the moisture absorption characteristics of the HMAM at different temperatures were analyzed. The rutting performance of the HMAM was investigated under different moisture contents and temperatures. The fatigue performance of the HMAM was investigated under different moisture contents, temperatures, and stress levels. Results show that: the rutting and fatigue resistance of the HMAM decrease with the increase in temperature and moisture content. The dynamic stability decreases by 8.9% at 40 °C and by 7.0% at 60 °C on average per 10% increase in moisture content and decreases by 22.7% on average per 10 °C increase in temperature. The fatigue life decreases by 4.1% at 15 °C and by 3.1% at 40 °C on average per 10% increase in moisture content and decreases by 31.3% on average per 10 °C increase in temperature. Finally, a prediction equation was established to predict the fatigue life under different moisture contents and temperatures. [ABSTRACT FROM AUTHOR]

Rock asphalt has been widely used to improve the performance of asphalt concrete, owing to its cost efficiency and beneficial modification effect. However, the moisture and high-temperature effects interdependently determine the degradation of fatigue resistance of rock asphalt concrete, owing to the unique climatic summer conditions in most high-temperature regions of China (e.g. southeastern coastal and south regions). Accordingly, the water absorption characteristics of rock asphalt concrete at different temperatures were analysed. Based on this analysis, 75 groups of modified three-point bending fatigue tests were implemented to investigate the combined effect of moisture, high-temperature, and stress level on the fatigue life of rock asphalt concrete. The moisture, temperature, and stress level conditions significantly influence the fatigue resistance of rock asphalt concrete. Finally, fatigue equations considering moisture and stress level were established to predict the fatigue life of rock asphalt concrete at different temperatures. [ABSTRACT FROM AUTHOR]

The dynamic analysis has been successfully used to predict the pavement response based on the finite element modeling, during which the stiffness and mass matrices have been established well, whereas the method to determine the damping matrix based on Rayleigh damping is still under development. This article presents a novel method to determine the two parameters of the Rayleigh damping for dynamic modeling in pavement engineering. Based on the idealized shear beam model, a more reasonable method to calculate natural frequencies of different layers is proposed, by which the global damping matrix of the road pavement can be assembled. The least squares method is simplified and used to calculate the frequency-independent damping. The best-fit Rayleigh damping is obtained by only determining the natural frequencies of the two modal. Finite element model and in-situ field test subjected by the same falling weight deflectometer pulse loads are performed to validate the accuracy of this method. Good agreements are noted between simulation and field in-situ results demonstrating that this method can provide a more accurate approach for future finite element modeling and back-calculation. [ABSTRACT FROM AUTHOR]

This article investigates the potential usage of eggshell powder as a bio-modifier for asphalt binder and mixture with the consideration of workability and mechanical properties. The effects of varying dosages (3%, 6%, 9%, and 12%) of eggshell powder on workability, rutting, and moisture damage of asphalt binder and mixture were investigated. Viscosity, multiple stress creep recovery, and bitumen bond strength tests were performed on asphalt binders. Subsequently, Superpave gyratory densification indices (Locking point method), wheel tracking, and indirect tensile strength (Modified Lottman) tests were performed on asphalt mixtures. Results show that incorporation of eggshell powder makes asphalt binder stiffer, increases moisture susceptibility, and reduces pumping ability irrespective of dosage rate. Furthermore, the incorporation of eggshell powder reduces workability but increases resistance to rutting and moisture damage properties of asphalt mixtures irrespective of dosage rate. [ABSTRACT FROM AUTHOR]

The reinforced concrete invariably involves some diseases (e.g., crack, void, etc.) due to the complex service conditions. These diseases are usually repaired to extend the service life of reinforced concrete by using cement grouting materials. In order to meet a certain color need of reinforced concrete, toner is mixed into the cement grouting materials. However, the toner has a negative effect on the early strength of cement grouting materials. Unfortunately, the mechanism of the negative effects of toner is still unclear, and no effective and targeted measures have been put forward. Hence, the main work of this paper reveals the mechanisms of the toner and nano-SiO2 (N-S) in the hydration process and the strength generation of the cement grouting materials in the case of different curing ages and nano-SiO2 contents via the scanning electron microscopy test (SEM), X-ray diffraction test (XRD), differential scanning calorimetry test (DSC), and Fourier transform infrared spectroscopy test (FTRI). Results show that: (a) the toner hinders the generation of AFt and CH crystals (especially for 1-day and 3-day), which delays the hydration process and weakens the early performance of cement grouting materials; (b) the N-S promotes the hydration process and the formation of C-S-H gels, so as to effectively increasing the early strength and reducing (but not eliminate) the adverse effect of toner on cement grouting materials; (c) With the increase of every 1% N-S, the flexural strength of 1-day, 3-day, and 7-day average increased by 11.3%, 2.9%, and 0.9%, respectively, and the compressive strength of 1-day, 3-day, and 7-day average increased by 0.8%, 0.3%, and 0.1%. [ABSTRACT FROM AUTHOR]

Aggregate structure plays a significant role in the pavement performance of road materials. However, there is a lack of fundamental understanding of mechanical characteristics and evolution characteristics of the aggregate structure in the existing research. To understand this complex structure, laboratory tests and numerical simulations using the discrete element method were used to investigate macroscopic mechanical properties of aggregate structure and microscopic aggregate contact forces, thus revealing the mechanical role of each size aggregate and evolution characteristics of the aggregate structure. Based on this, the specification gradations of road materials were optimised to build a strong aggregate structure. Laboratory tests and engineering application show that road materials using the proposed gradation can exhibit improved pavement performance and engineering effects. [ABSTRACT FROM AUTHOR]