Journal of Materials in Civil Engineering

Recently, single-crystal Cu-Al-Mn (CAM) superelastic alloy (SEA) bars have been developed to address the shortcomings of traditional Ni-Ti SEA bars, i.e., high cost, low workability, and lack of superelasticity at low temperatures. The CAM SEAs have a wide range of potential applications in biomedical, aerospace, mechanical, and civil industries. However, no quantitative information is available on the chemical stability of this relatively new metal alloy. This study quantified the chemical resistance of CAM SEA bars compared with that of mild steel bars in terms of mass loss and changes in mechanical and physical properties. Tensile testing was performed to estimate the reduction in the yield load of the samples after chemical aging. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were carried out to determine the oxidation potential of the material. Corrosion parameters of CAM SEAs were quantified through potentiodynamic polarization tests. The erosion rate of CAM SEAs was also estimated using these corrosion parameters to compare against the typical values reported for mild steel. The CAM SEAs had a chemical resistivity significantly superior to that of mild steel regardless of the environmental exposure conditions tested in this paper. It was also found that CAM SEAs have comparable corrosion resistance to another Cu-based shape memory alloy composition: Cu-Al-Ni.

The present study is an attempt to explore the use of reclaimed asphalt pavement (RAP) and recycled concrete aggregates (RCA) in dense bituminous macadam (DBM) mixes in a simple approach to the readjustment of the gradation of RAP aggregates with RCA and the modification of RAP bitumen by treatment with conventional low viscosity grade (VG) bitumens, namely, VG10 bitumen and VG30 bitumen. The primary objective of this study is to design the mix containing RAP, RCA, and low viscosity bitumen so as to have satisfactory characteristics. Based on penetration tests, corroborated by other tests, the optimum proportions of the VG30 bitumen or VG10 bitumen and RAP bitumen, are found to be $70:30$ and $60:40$, respectively. The modified RAP mixes are found to result in, respectively, a 22% and 28% increase in the Marshall stability as compared with the control mix. It is also seen that the RAP modified mixes in general satisfy all requirements of Marshall and moisture susceptibility criteria. Furthermore, the indirect tensile strength (ITS) of RAP modified mixes with the RCA show a direct relationship with the temperatures, indicating an advantage over the conventional mixes.

The physical, mechanical, and durability properties of glass fiber–reinforced concrete (GFRC) incorporating fly ash, slag, and acrylic polymer with different fiber contents were studied. The use of pozzolanic materials and polymer modified the fresh and physical properties by improving the workability and reducing the water absorption and density of the GFRC mixes. The flexural strength of mixes incorporating fly ash and slag improved with increasing fiber content. The inclusion of acrylic polymer improved the deformation capability of all mixes. Analysis of the fracture surface of the GFRC samples showed the dependence of toughness with the amount of fiber pullout. Wet–dry cycles and exposure to high temperature resulted in significant reductions in mechanical properties in terms of flexural strength and toughness. The normalized toughness values of mixes exposed to 800°C and wet–dry cycles are found to be correlated with each other. Therefore, exposure to high temperature might provide rapid results in predicting long-term GFRC degradation and might be an alternative to wet–dry cycles.

Physical salt attack (PSA) or salt weathering occurs as a result of the crystallization pressures in concrete pores exerted by phase changes of salts that penetrate the concrete. The crystallization pressures cause microcracking of the concrete and mass loss. Different concrete materials have been reported to affect the concrete resistance to PSA. This study examined the effect of incorporating supplementary cementitious materials (SCMs) in concrete on its transport properties and, ultimately, on its resistance to PSA. The effect of SCMs on PSA durability was found to be directly related to their role in altering the pore network. Moreover, results from field specimens were compared with those obtained in the lab. Correlations between the resistance to PSA and formation factor, absorption rate, and chloride migration coefficient were explored in this study. The results showed that slag and silica fume binary mixes had high resistance to PSA, and ternary mixes that included slag, in addition to Class F fly ash, were also resistant to PSA. The study found some correlation between the mass loss in full submersion tests with respect to their formation factors and transport properties. The field specimens were evaluated over a 1-year period, and the results showed PSA manifestation. It was found that the measured mass loss in PSA full submersion lab tests correlated well with the concrete formation factor. It was also found that the damage in some binary fly-ash specimens in the field and partially submerged lab tests was greater than expected based on the results in the fully submerged test.

This paper presents an experimental and numerical study on the global buckling behavior of welded thick H-section columns of Q460GJ steel under axial load. The thickness of the flange and web is 42 and 25 mm, respectively, and the slenderness ratios of the columns vary between 49.8 and 85.0. Six specimens with different section sizes were tested, and their overall buckling results showed significant lateral displacement. Test results and design values calculated in accordance with several national design codes were compared. Finite-element models that considered the initial inflexion and residual stress were established. The comparison between the finite-element calculation and test results confirmed the reliability and accuracy of the model. A parametric study of the bearing capacity of thick H-section columns was conducted on the basis of their slenderness ratio and section size. Design recommendations were provided on the basis of the comparative analysis of the finite-element calculation results and design curves obtained using different codes. Recommendations for selecting column curve types in national codes is given when designing global buckling of welded thick H-section columns of Q460GJ steel under axial loading.

This paper aims to investigate the influence of void characteristics on the uniaxial penetration strength (UPS) of asphalt mixtures using a three-dimensional (3D) discrete-element method (DEM). Three models for the uniaxial penetration test (UPT) for asphalt mixtures (namely, a model considering real void size and distribution, a model considering random void size and distribution, and a model without considering voids) were created using imaging techniques and 3D DEM embedded with a Burgers model. The UPS was predicted/simulated on the basis of the models. The simulation results were verified against known laboratory UPTs. Research results showed that the UPS of asphalt mixtures was able to be predicted by using 3D DEM, and void characteristics had a significant influence on the UPS. With the same model parameters, the UPS of the model without considering voids was the largest, followed by that of the model considering random void size and distribution, whereas the model considering real void size and distribution was the lowest but the closest to the experiment results. Furthermore, aggregate size, binder content, and temperature affected the UPS. The UPS grew with increasing nominal maximum aggregate size and declined with temperature. The UPS with low or high binder content was less than that with the optimum binder content at 60°C.

Associations between polymer morphology and the properties of polymer-modified asphalt (PMA) have been widely reported. Fluorescence microscopy (FM) plays a key role in analyzing the morphology of polymers in PMA. However, two-dimensional (2D) fluorescence images may not reveal the true nature of polymer phase in PMA, because the image is a projection of the three-dimensional (3D) space on a 2D plane. This study reconstructs the 3D polymer phase in PMA by using confocal fluorescence microscopy and image processing techniques. The method is successfully used in analyzing the morphology of polymers in styrene–butadiene–styrene (SBS) PMA. A quantitative comparison is made between the results of the 3D volume fraction and 2D area fraction of the polymer phase. The findings indicate that 3D reconstruction is necessary to understand the true state of the polymer phase in PMA. This research contributes to the body of knowledge in civil engineering materials by developing the method for 3D reconstruction of the polymer phase in PMA and discovering the more realistic state of the polymer phase.

Calcium alginate capsule encapsulating rejuvenators are a new approach to enhance the self-healing property of asphalt, but the release and self-healing properties of calcium alginate capsules in asphalt concrete under cyclic loading conditions are still unclear. In this research, calcium alginate capsule encapsulating sunflower oil as a repair agent was synthesized and the oil release ratios of the capsules in asphalt concrete after compression loading were determined through a Fourier transform infrared test (FTIR). Then, strength and fracture recovery tests and DSR test were conducted to evaluate the effects of the released oil on the healing levels and rheological properties of asphalt concrete. Finally, computed tomography (CT) scan and SEM tests were conducted to study the morphology of the capsules to analyze the oil release mechanism of calcium alginate capsules. The test results showed that with the increase of the compression loading cycles, more oil was released from the capsules and the self-healing level of the asphalt concrete increased obviously. In addition, the oil released from the capsules softened the asphalt, decreasing the complex modulus and increasing the phase angle of the asphalt. CT scan images showed that after compression loading and healing, the capsules deformed slightly but maintained their spherical shape, indicating that the capsules could release the oil from the cavities due to shrinking and deformation upon compression loading and restore their original shape after compression loading.

An asphalt mixture has different tensile properties as compared with compressive ones due to the combined effect of aggregate interlock, binder stiffness, and aggregate-binder interactions. This study aims to investigate the dynamic tensile and compressive moduli of asphalt mixture through indirect tensile and four-point bending modulus tests. Firstly, methods for determining the tensile moduli of the mixtures in the preceding two tests are developed based on the bimodular theory. Then, the compressive and tensile moduli of one asphalt mixture are determined using the developed methods. It was found that the compressive moduli of the asphalt mixture exceed the tensile ones over the entire frequency domain in both types of test. In general, tensile moduli obtained from indirect tensile and four-point bending tests are in good agreement, especially at the intermediate- to high-frequency domain. The ratios between the compressive moduli and tensile moduli obtained from the two tests are also similar, regardless of test temperature and air-void content. The ratios are about 2.5 at low and intermediate temperatures and increase to approximately 4.0 at high temperatures. The conventional solution for the indirect tensile test based on a single-modulus assumption mainly reflects the compressive properties of the mixture but provides an unrealistic estimation for its Poisson’s ratio. Conversely, in the four-point bending test, the solution based on a single modulus well represents both the tensile and compressive properties of the mixture.

Understanding the diffusion of moisture in asphaltic materials is crucial because it yields key insights into the moisture-induced damages of asphalt pavement. In this work, the molecular dynamics simulation technique was adopted to characterize the diffusion and structural properties of moisture (water molecules) in both neat asphalt binder and asphalt mastic. Microstructural changes during the diffusion process, including free volume and hydrogen bond formation, were observed to clarify the mechanism of diffusion behavior at the atomistic level. The concentration dependence of moisture diffusion coefficient was revealed. Water molecules were well dispersed in the model and mainly formed hydrogen bonds with asphalt molecules at low concentrations. However, large water clusters were formed with the predominant formation of water−water hydrogen bonds and acceleration of diffusion at high concentrations. In the asphalt mastic system, silica particles not only introduced more free volume to speed up the diffusion of moisture but also intensified the affinity between moisture and the asphalt mastic system. Moreover, the relationship between the moisture diffusion and structural properties suggested that the diffusion of moisture in asphaltic materials is controlled by both the free volume and the cohesion property among asphalt chains. This relationship could be exploited to obtain information regarding diffusion behavior in the asphaltic material system and select materials to achieve excellent antistripping properties for the asphalt mixture.

This paper investigates the temperature–time evolution of the rheological properties of nanosilica (NS)-modified cement paste. A rheometer was used to determine the rheology curves of the paste at 20°C–40°C within 2 h and fitted to the Bingham model. Fluidity, free water content, isothermal calorimetry, and thermogravimetric analysis were used to explain the temperature–time evolution. The results showed that the temperature–time evolution of rheological parameters of NS-modified paste was linear. Both the yield stress and plastic viscosity of cement paste increased with increasing NS dosage and related to the free water content. On account of the flocculation of NS, the initial values of the rheological parameters became larger, and the higher the temperature, the larger the values. The evolution rate of yield stress over time was $\mathrm{NS}40°\mathrm{C}>\mathrm{NS}30°\mathrm{C}>\mathrm{NS}20°\mathrm{C}$. The initial value of the thixotropy with NS increased by orders of magnitude compared with the control group, while the development of thixotropy was very sensitive to temperature. There was a small initial thixotropic value and a fast increase rate at 30°C, which was an ideal evaluation model. The dominant factor in the dormant period of evolution was the destruction and reconstruction of C-S-H bridges.

This study investigated the effect of waste toner as a cost-effective enhancement modifier on short-term aging and moisture resistance of asphalt binders and mixtures. Moreover, the mechanism of asphalt binder aging and moisture resistance was reviewed, aiming to provide promising evaluation methods for assessing short-term aging resistance of asphalt binders as well as moisture resistance of asphalt binders and mixtures. First, the aging resistance of neat and toner-modified asphalt (TMA) binders was evaluated using three approaches: rheological aging index (RAI), viscosity aging index (VAI), and chemical functional group indices based on data obtained from Fourier transform infrared spectroscopy (FTIR) analysis. To measure viscoelastic and viscosity characteristics of neat and TMA binders, a dynamic shear rheometer (DSR) and a viscometer were employed, respectively. Second, the moisture resistance of asphalt binders and mixtures were investigated based on analyzing the infrared spectrum and tensile strength ratio (TSR), respectively. The findings indicated that modifying binder with low percentages of waste toner enhanced the short-term aging resistance. Also, TMA binders containing 12% of waste toner presented a significant improvement in moisture resistance of asphalt binders and mixtures.

In the design of reinforced soil structures, the pullout resistance of reinforcement embedded in the fill material is an important input parameter. Different pullout test setups have been proposed previously to determine the axial pullout resistances of reinforcements. In the present study, the details of a unique test apparatus with the ability to conduct both axial and transverse pullout testing of different types of reinforcement was highlighted. The pullout resistances of different geogrids embedded in uniform dense sand beds were presented. Based on extensive axial pullout testing on five different geogrids of varying tensile strengths and aperture sizes under three different normal stresses, empirical equations were proposed to estimate the axial pullout resistances of geogrids at two front-end pullout displacements. The estimated pullout resistances from the proposed equations were found to be in close agreement with the pullout resistances of a sixth geogrid considered in the present study and with the two other studies reported in the literature. A sensitivity analysis was carried out to determine the key parameters influencing the pullout resistance of the geogrid. For the different geogrids tested in dense sand, the axial pullout resistance factors were found to range from 0.34 to 1.97 and 0.52 to 2.05, corresponding to the reinforcement front-end displacements of 30 and 50 mm.

As an important mechanical property index, the interfacial bonding properties between coating and substrate are key factors in determining the corrosion resistance and reliability of the system. In this paper, the corrosion resistance performance and interfacial bonding properties of the Zn/Zn–Al multilayer coating/steel substrate system were studied. Neutral salt spray tests and electrochemical tests were conducted to evaluate the corrosion resistance of the coatings. Meanwhile, the three-point bending test with the acoustic emission (AE) technique was used to study the interfacial bonding properties of the multilayer coating/substrate systems. As a comparison, these tests were carried out on a Zn monolayer coating/substrate system and a Zn–Al monolayer coating/substrate system. The corrosion test results showed that the superposition of the Zn/Zn–Al coating/substrate system with different grain sizes hinders the transport path of corrosive ions, resulting in rust spots appearing later in the multilayer coating/substrate system than in the monolayer coating/substrate system. Given the increase in coating thickness, the defects, porosity, and corrosion through the holes of the coating increase, which aids in the corrosion process and reduces the corrosion resistance of the coating. The interfacial bonding strength of the system was analyzed using fracture toughness. The test results showed that the extent of the depreciation of the fracture toughness of the multilayer coating/substrate system before and after corrosion is lower than that of the monolayer coating/substrate systems. The interfacial bonding properties of the multilayer coating/substrate system are better than that of the monolayer coating/substrate systems because of the good material matching and dislocation effect between the multilayer coatings.

This paper investigates damage and healing of cementitious materials based on fly ash (FA) with a special focus on the effect of repeated loading on the self-healing performance. In total, 90 prism specimens and 33 cylinder specimens were prepared and tested. Variables including the FA replacement ratio and preloading level were considered. Different methods were adopted to evaluate the self-healing performance, i.e., mechanical tests, acoustic emission (AE) analysis, water absorption measurement, and scanning electron microscope (SEM) observation. Test results revealed that an appropriate amount of cement replaced by FA was beneficial to the self-healing performance of the specimens subjected to a high level of repeated preloading, where the strength increased by 11% and the water absorption rate decreased by 12%, in comparison with that of the undamaged specimens. This was attributed to the active hydration of FA, which was confirmed by an energy dispersive X-ray spectroscopy (EDS) analysis. This study extends understanding of the self-healing performance when subjected to repeated loading and provides some useful suggestions for the self-healing technique based on mineral additives.

This paper presents the results of experimental research on PBO (P-phenylene benzobisoxazole)-FRCM (fabric-reinforced cementitious matrix)-confined concrete elements with a variously shaped end PBO mesh overlap. In FRCM systems, the composite is bonded with the concrete using mortar as opposed to FRP (fiber-reinforced polymers) systems, and such bonding is effected using epoxy resin. Twelve confined concrete elements were tested. They were divided into four series, each comprising three elements. The elements were confined with a single layer of PBO mesh but differed in the shape (geometry) of the composite’s end overlap. The results of the tests, during which the effect of the shape of the end mesh overlap on the values and distribution of transverse (circumferential) strains was examined, are presented. On this basis, an optimal way of constructing the PBO-FRCM confinement of concrete elements is proposed. The mimicking of the inner steel winding concept in the outer confinement made of PBO mesh turned out to be the most effective. The transfer of the ends of the overlap to the element’s two ends also improves the load capacity of the support zones in which compressive stresses are concentrated.

Experiments were performed to investigate the fatigue properties of corroded high-performance steel (HPS). Ninety pieces of Q460D and 90 pieces of Q550E HPS specimens with five different corrosion levels were designed to investigate the effect of corrosion on their fatigue properties. Three-dimensional (3D) scanning and scanning electron microscope (SEM) were employed to observe the macroscopic and microscopic morphology. The $S\text{-}N$ curves in terms of various levels of corrosion damages were obtained, and the influences of different corrosion levels on the fatigue properties are discussed. The experimental results show that corrosion changes the characteristics of the fatigue crack source zone, crack development zone, critical transition zone, and instantaneous fracture zone. Compared with Q460D, the critical transition area of Q550E has a higher flatness. Progressing corrosion damage results in a linear decreasing fatigue life of the HPS specimens in the double logarithmic coordinate system. The fatigue life of steel specimens can be expressed as an exponential function of the cross-sectional corrosion loss level. The increasing stress level will aggravate the degradation of fatigue life.

Ballast degradation (particle breakage and abrasion) induced by repeated train loads may lead to insufficient track stiffness and excessive track settlement. For safe operation and effective maintenance of ballasted railroad tracks, an accurate assessment of the initial ballast particle size and shape properties and the morphology evolution with usage is very beneficial. Nevertheless, commonly used ballast specifications dictate only particle-size distribution or gradation testing, which is not capable of describing ballast particle morphology characteristics and those changes induced by surface abrasion and particle breakage experienced during ballast service life. To obtain morphological characteristics of ballast particles, Los Angeles abrasion testing was performed on two types of ballast materials, tuff and granulite. An enhanced particle boundary roughness treatment method was implemented in a computer-aided ballast morphology analysis system to capture and reconstruct the three-dimensional ballast geometry. By adopting this method, the degradation of ballast particles during service were assumed to be associated with the Los Angeles abrasion testing in the laboratory. Test results clearly showed the trends observed during the process of particle degradation quantified through imaging-based morphology indexes; angularity index (AI) and flat and elongated ratio (FER) typically decreased, whereas particle sphericity and convexity increased. In relation to such morphological changes, ballast abrasion was found to significantly reduce ballast material’s angle of repose.

Aggregate gradation segregation in asphalt mixtures can result in early damage and reduced durability in asphalt pavement. However, presently, most methods of segregation detection can be performed only after the design of hot-mix asphalt (HMA) or asphalt paving is completed. To identify the segregation characteristics of different aggregate gradations in the mix design of HMA, a simple laboratory method was developed that includes the definition of evaluation indicator of segregation degree for coarse aggregate gradation and the corresponding testing apparatus. In addition, the model for evaluating coarse aggregate segregation was established using a multivariate nonlinear regression method. Based on the model for evaluating coarse aggregate segregation, a prediction method for HMA segregation was proposed. The results of an application case showed that the models for evaluating coarse aggregate segregation and prediction method for HMA segregation are feasible and reasonable. The method to characterize coarse aggregate segregation presented in this paper may help in optimizing the design of aggregate gradation in HMA.

This research aimed to evaluate the impact of aggregate characteristics on the skid resistance of pavement. Firstly, the mineral composition, wear-resistance property, angularity, and texture of five types of aggregates were determined. Then, the accelerated-wear test for asphalt mixtures was carried out by self-developed accelerated-wear equipment in the laboratory. Then, the degree of influence of each parameter was evaluated through gray correlation degree and linear regression methods. It was found that the mineral composition of different aggregate types is obviously diverse, and the mineral composition has an impact on the wear-resistance property of aggregate. With the increase of wear cycles, the textural depth of the asphalt mixture decreased, but the British Pendulum Number (BPN) increased slightly in the initial stage of wear. Based on the results, it was suggested that to improve the skid resistance of asphalt mixtures, the abrasion resistance index and shape index of aggregate should be taken into consideration. In addition, improving the aggregate processing technology to improve the angularity index (GA) and sphericity (SP) and to reduce flattening rate ($L/S$) will have great practical significance for improving the skid resistance of asphalt pavement.

Studies have shown that fine-aggregate matrices (FAM) are a good tool to assess fatigue cracking and moisture damage of hot-mix asphalt (HMA) mixtures. However, there is no consensus on the design method to produce FAMs that represent precisely the fine fraction of the HMA mixture. This study evaluates two design methods to determine the FAM binder content: one based on asphalt extraction by ignition and one based on the mineral aggregate specific surface area. The results led to the proposal of refinements in both methods regarding the crystallization water of the mineral aggregates, the use of more precise methods such as laser diffraction to estimate the filler specific surface area, and the estimation of the richness modulus of the FAM obtained from the full HMA mixture. A relationship between the richness modulus of the HMA mixture and the FAM binder content was established, which turns the method based on the specific surface area of fine aggregates into a viable and promising tool to estimate the FAM binder content.

Unhydrated cementitious materials in ultrahigh-performance concrete (UHPC) with a low water-to-binder ratio stop hydrating owing to water shortage but continue hydrating after re-exposure to water; this phenomenon is referred to as rehydration. Rehydration may either enhance or damage cement-based materials, and the mechanisms underlying it remain unclear. In this study, an accelerated rehydration test was conducted on an UHPC matrix to determine the chemically combined water contents and compressive strengths, and a rehydration model was developed based on the Krstuloviⓒ–Dabiⓒ hydration dynamics of cement and microstructure information of cement hydration; the model was used to analyze the mechanism behind the influence of rehydration on strength, combining the variations in micromorphology and pore structure. Results showed that the simulated values of rehydration model were in agreement with experimental values. During the early rehydration period, cement hydrated rapidly, and rehydration products filled and repaired the pores, improving the matrix properties. However, during the late rehydration period, cement hydrated slowly; and the volume expansion of rehydration products increased internal stress, resulting in microcracks and deterioration of the matrix properties.

The effect of nano-kaolinite clay (NKC) on the bond behavior between rebar and concrete was studied in a series of experiments. An electrical corrosion method was used to corrode the rebar embedded in concrete specimens. Chloride diffusion and chloride content tests were performed to evaluate the effect of nanoclay on the chloride diffusion depth and chloride ion content in concrete. Pullout tests were performed to assess the bond properties, including the bond-slip curve and ultimate bond strength, between concrete and rebar before and after corrosion. The results revealed that NKC improved the chloride resistivity and bonding in the concrete specimens. The specimens with a 5% nanoclay addition showed the lowest percentage of the rebar corrosion level and bond strength degradation due to corrosion. After 48 h of corrosion, the rebar corrosion ratio decreased by 52%, and the ultimate bond strength increased by 35% compared to the control specimen.

The present study aims to quantify the fatigue characteristics of nanoclay-modified binders, considering different analysis procedures in the linear amplitude sweep (LAS) test. Four unmodified and modified asphalt binders were subjected to the LAS test at 10°C, 20°C, and 30°C. The fatigue life obtained using five different analytical methods were assessed and compared. The effect of controlled strain rate (CSR) used in the LAS test was not found to be significant in changing the fatigue ranking of asphalt binders. Different analytical methods produce different fatigue curves with no change in the relative ranking of the binders at each temperature. The model parameters ($a$ and $b$) obtained by fitting the relationship between average released pseudostrain energy ($G^R$) and the number of cycles to failure ($N_f$) can significantly impact fatigue life, resulting in a discrepancy in the results. This discrepancy, across different temperatures and binder types, can be removed by smoothening of the model with $b=-2$. The unified $G^R–R\text{-}\text{based}$ analysis, as is proposed in this study, results in a lower value of fatigue life at lower strain susceptibility in the standard fatigue model. Statistical analysis reveals that there is no distinct influence of nanoclay on the fatigue life of asphalt binders. Inclusion of nanoclay results in either similar or marginally higher fatigue life at all the temperatures. The analysis and results support the use of a $G^R–R\text{-}\text{based}$ approach for quantifying the fatigue life of asphalt binders.

Transverse cracking is one of the major distresses of asphalt pavements with a semirigid base. After subjected to the loading, aging, and other factors, the materials properties of in-service asphalt pavements are quite different from the initial properties, so it is important to directly use the layer core samples to evaluate the crack resistance for the in-service pavements. In this paper, five expressways were selected, and 195 core samples were obtained from the different asphalt layers in 13 road sections. The field transverse cracking survey results show that almost 80% transverse cracks are bottom-up transverse reflective cracking. The semicircular bending (SCB) tests were performed on the layer core samples, and analysis of variance (ANOVA) analysis was applied to reveal the sensitivities of tensile strength and fracture energy to equivalent single axle load (ESAL), service age, aggregate gradation, air voids, and specimen location. The results of the ANOVA analysis indicate that ESAL and service age significantly affect tensile strength of surface and middle asphalt layers, and fracture energy of surface and middle asphalt layers are sensitive to aggregate gradation and service age. ESAL only acts on the upper two asphalt layers, not the bottom asphalt layer, and SCB test results of the bottom asphalt layer are only sensitive to air voids. Then the field investigation of pavement transverse cracks were launched, and the results present that there are three stages of process for transverse cracking development, including (1) crack initiation stage, which occurs during the first few in-service years, (2) crack explosive growth stage, in which the total length of transverse cracks sharply rises, and (3) crack stabilization stage, in which the total length of transverse cracks tends to be stable with a much slower growth speed than the second stage. The critical service age point between the latter two stages could be considered as the appropriate maintenance time for transverse reflective cracking. Furthermore, the correlation analyses were conducted between laboratory SCB test results and field cracks investigation. The results show that field transverse cracks performance have a better correlation relationship with fracture energy of the core samples, and a limit fracture energy value of $\mathrm{2,500}\mathrm{J}/{\mathrm{m}}^2$ is proposed to prevent reflective cracking in this study.

This research aimed to apply different models on electrochemical impedance spectroscopy to study the influence of grain refinement and straining obtained from surface mechanical attrition treatment on the passivation of carbon steel in an alkaline solution at open circuit and different passivating potentials. Based on the power law model, the graphical presentation of capacitances at high frequencies and the SIMPLEX method at low frequencies were used to evaluate the electrochemical properties of the interface. The point defect model was used to estimate point defects diffusivity of the passive film in the passivating potential range. Results showed the oxide layer formed on a more strained and grain refined surface was thinner but less porous.

Cracking of concrete structures during hydration often occurs during construction. This study investigated the expansive property of concrete with an unstrained expansive agent to reduce cracking. Laboratory tests, field measurement, and numerical simulations on deformation during hydration were investigated. The test results of the unstrained specimen indicated that the expansive ratio reached a peak in the first 14 h for the water–binder ($w/b$) ratios of 0.43 and 0.6. However, when $w/b=0.3$, the expansion ratio needed a long time to reach the peak (30 h). The expansion ratio remained unchanged after the peak. The amount of the expansive agent and the water–binder ratio show a significant correlation with the expansive capacity. The relative favorable content of the expansive agent and $w/b$ ratio of concrete with the expansive agent were 10% and 0.43, respectively. A concrete floor with the expansive agent showed an overall compressed state, which indicates that concrete shrinkage was fully compensated by the addition of the expansive agent.

To better predict ductile fracture (DF) of structural steels under complicated stress states, the DF of an A36 steel was experimentally and numerically investigated within a wide range of stress states. Meanwhile, a scanning electron microscope (SEM) analysis was performed to shed more light on the DF microscopic mechanism of the material tested. The correlations between the ductility and the stress states for the A36 steel were identified using four representative uncoupled DF models, which are endowed with different stress triaxiality ($\eta$) and Lode parameter ($L$) dependence. In addition, the experimental results of an AISI 1045 steel, covering a wider range of stress states ($-0.255<\eta <0.986$; $-1<L<0.571$), were revisited. By evaluating the three-dimensional (3D) fracture loci of the A36 and AISI 1045 steels using distinct models, it was concluded that an appropriate model should be featured with flexible $\eta$ and $L$ dependence as well as the asymmetry with respect to the plane of $L=0$.

Diaphragm design provisions in North America were originally developed based on the performance of diaphragms constructed with sawn lumber framing members. Although these design guidelines have been applied to diaphragms built with wood I-joists, questions were raised as to whether they are equally applicable. More recently, the height limit of light wood frame buildings was increased across North America from four to six stories, leading to the need for high capacity diaphragms. This change raises further questions on the validity of using existing lumber diaphragm design provisions for diaphragms built with wood I-joists. In this study, tests were conducted to investigate the lateral load resistance of diaphragms built with wood I-joists by comparing with those built with solid sawn lumber joists. Since the lateral load resistance of wood diaphragm is highly dependent on the behavior of their individual nail connections, tests were first performed to examine the strength of nailed joints with point-side penetration into solid sawn lumber and flange of wood I-joists. After that, small-scale diaphragm tests were conducted to investigate the effect of multiple-row fastening on potential diaphragm performance in relative terms. Based on these results, it is tentatively recommended that the fastener row factor for diaphragms built with I-joists can be obtained by applying a 10% reduction to the corresponding value for sawn lumber diaphragm.

This study presents a partially nondestructive testing (PDT) method, the innovative double-shear test method (DSTM), to improve the accuracy of concrete strength tests in situ and reduce structural damage. This method involves double-shear faces of the concrete core, on which the load is exerted by a specified DSTM apparatus to produce approximately pure shear stress and obtain the shear strength of the concrete core. The DSTM test indicated that some factors (core-drilling direction, specimen diameter, core length, aggregate type, and concrete moisture) do not influence concrete strength, and a strong relationship between DSTM strength and cube compressive strength ranging from 20 to 40 MPa is proposed for testing concrete samples. The reliability and repeatability of the DSTM are greater than those of other in situ test techniques, such as the Schmidt rebound hammer (SRH) and pull-off test method. Features of the visible failure mode of concrete samples certify the correctness of the test results. Test results demonstrated that the DSTM is applicable to in situ tests of concrete compressive strength with much higher accuracy than the core-drilling method, and causes less damage to structures.

Current specifications for asphalt–rubber (AR) binders is designate the degree of rubberized modification of the asphalt cement at a specific temperature. It is necessary to investigate the performance-based properties of the AR binders by means of advanced test methods. In this research, three types of asphalt binder with different crumb rubber concentration levels were produced and tested. The base asphalts chosen for the study were $60/70$ penetration-grade (Pen $60/70$) and $20/40$ penetration-grade (Pen $20/40$) asphalts and a polymer-modified bitumen (PMB). Test results showed that penetration-grade asphalt blended with rubber appeared to have improved toughness with increasing rubber content, whereas a reduction in toughness was found for the PMB mixed with rubber. At high temperatures, the addition of rubber improved the resistance to permanent deformation of the asphalt binders. However, the AR binders showed relatively poorer delay elastic behavior compared to the PMB, reflecting that the crumb rubber acted mainly as flexible filler. In addition, equiviscous temperature (EVT) was used for grading asphalt binders because it took slow-moving traffic into account at high pavement service temperatures. In terms of balanced design method, the results demonstrate that the performance of the AR binder was asphalt dependent. The Pen $20/40$ asphalt modified with rubber was found to be more rut-resistant than the AR binder including the Pen $60/70$ asphalt, but little difference in crack resistance was shown between them. The PMB modified with rubber had good resistance to rutting, but a decline in fatigue performance was found with increasing rubber content.

Fatigue cracking is a major distress in asphalt concrete and has a significant influence on material performance. A coupled extended finite element method (XFEM)-continuum damage mechanics (CDM) model was developed in this paper to investigate fatigue cracking behavior of asphalt concrete. The model was then implemented in commercial finite element software using user-defined subroutines (UMAT and UDMGINI). This model successfully simulated the fatigue damage accumulation stage and crack propagation stage as a continuous process. Determination of model parameters are discussed, and then fatigue crack growth in a semicircular bending (SCB) beam is analyzed. Numerical results of fatigue crack growth in the SCB quantitatively matched well with experimental records. This indicates that the coupled XFEM-CDM method developed in this paper can serve as an effective tool for predicting fatigue cracking behavior of asphalt concrete. Fatigue cracking behavior and mechanical response of a three-point bending beam are also studied. Numerical findings of fatigue cracking lives and stiffness evolution are qualitatively consistent with laboratory results.

Additives enhancing the fracture resistance of clay are of great importance to decrease cracking potential of earth structures. With the promotion of environmental protection, eco-friendly biopolymers have shown their competitiveness as additives in different engineering fields. This research deals with the findings of an experimental investigation carried out on single-edge notched beams manufactured from compacted clay. Three-point bending (flexure beam) tests were performed to evaluate the effect of xanthan gum biopolymer, a common fluid thickener biopolymer in the food industry, on fracture behavior of clay during drying. Particle size analysis (PSA) and scanning electron microscopy (SEM) were carried out to study the microinteractions of clay–xanthan gum mixtures. The results showed that although xanthan gum biopolymer has limited effects on nominal flexural strength and fracture toughness at high water contents, it increases clay fracture energy and final displacement at zero external load in all water contents. With the evaporation of water, the strength and fracture toughness of biopolymer-treated clay increases more significantly in comparison with the pure clay. In addition, although the fracture energy of clay reduces during drying, for biopolymer-treated clay the fracture energy not only does not decrease significantly but also increases at the dry state.

Alternative materials are becoming the substances of choice for designers over conventional materials due to cost and availability constraints. The sustainability and maintenance of the supply of conventional construction materials often becomes a limiting factor. This calls for the utilization of industrial refuse and agricultural by-products. Recycling of this waste can be an effective tool to decrease the levels of pollution and enhance the economy. Different materials like rice husk ash (RHA), fly ash (FA), silica fume (SF), and slag can be substituted in cement owing to their pozzolainic behavior. However, their use may make the concrete more prone to carbonation than ordinary portland cement (OPC) concrete. This research is aimed at knowing the influence of RHA on carbonation at distinct conditions. Concrete samples with varied fractions of RHA (0%–20%) with interval of 5% under three different relative humidity levels (30%, 45%, and 60%) were made to undergo accelerated carbonation tests at 5% ${\mathrm{CO}}_2$ content after being cured for 7, 14, and 28 days. It was found that there was no carbonation observed in relative humidity level of 30%. However, the depth of carbonation was directly proportional to the RHA replacement level for humidity levels of 45% and 60% and the increase was nearly the same corresponding to 15% and 20% replacement for curing age of 28 days. Hence, without compromising the carbonation resistance, greater RHA fractions can be used with a longer curing period. Besides, the results also revealed that the depth of carbonation decreased with an increase in relative humidity levels from 45% to 60%. The effect of compressive strength on carbonation depth of RHA concrete was also studied and it was found that the carbonation depth decreased as the compressive strength of concrete increased.

Despite ongoing research efforts, we continue to fall short of arriving at a consistent representation of fire-induced spalling of concrete. This is often attributed to the complexity and randomness of spalling as well as our persistence in favoring traditional approaches as a sole mean to examine this phenomenon. With the hope of bridging this knowledge gap, this paper demonstrates how utilizing surrogate modeling via data science and machine learning algorithms can provide us with valuable insights into fire-induced spalling. In this study, nine algorithms, namely naive Bayes, generalized linear model, logistic regression, fast large margin, deep learning, decision tree, random forest, gradient boosted trees, and support vector machine, are applied to analyze observations obtained from 185 fire tests (collected over the last 65 years). The same algorithms were also applied to identify key features that govern the tendency of fire-induced spalling in reinforced concrete columns and to develop tools for instantaneous prediction of spalling. The results of this comprehensive analysis highlight the merit in utilizing modern computing techniques in structural fire engineering applications given their extraordinary ability to comprehend multidimensional phenomena with ease, high predictivity, and potential for continuous improvement.

This study examines the use of brick powder (BP) reclaimed from construction and demolition waste as a filler in a hot-mix asphalt (HMA) in hot and desertic areas. For this research, two HMA mixtures were designed using different fillers: one using BP and the control using limestone powder (LSP). Readily available natural desert sand was also used in the mix. The samples were subjected to rutting, creep compliance, indirect tensile strength modulus (ITSM), and moisture susceptibility tests. The results were that the mixtures using BP had superior mechanical characteristics to mixtures using LSP. BP showed a marked improvement on asphalt pavement performance, and it resulted in a flexible road pavement with a long expected lifespan.

This paper aims to investigate the distribution characteristics of the partial carbonation zone of concrete. A series of experimental carbonation tests considering the effect of external temperature, concentration of ${\mathrm{CO}}_2$, and relative humidity were implemented. The pH values of the simulated pore solution of the powder sample of concrete are presented. The carbonation model based on the mass-transfer theory is proposed. The results indicate that the pH value of the simulated pore solution can be applied to demarcate the complete and partial carbonation zones of carbonated concrete. The numerical model can be used to preferably simulate the distribution of complete and partial carbonation zones. The length of the partial carbonation zone increases with the increase of temperature and decreases with the increase of relative humidity. The lengths of the partial carbonation zone generally increase with the increase of concentration of ${\mathrm{CO}}_2$. Concrete with a high initial diffusion coefficient is conducive to the diffusion of carbon dioxide. The length of the complete and partial carbonation zones can be sensitively affected by the activation energy.

Rutting is one of the most important distresses in asphalt mixed pavement. As for flexible pavements, stone matrix asphalt is the best option for reducing this failure despite its demerits, e.g., the risk of draining down and fat spots. There are several ways to decrease rutting potential, including by the use of fiber as asphalt binder modifier or asphalt mixture additive. Accordingly, in this study, the rheological and mechanical properties of asphalt binder and stone-matrix asphalt were examined at different percentages of ceramic fibers as an asphalt binder modifier. A rolling thin-film oven test was conducted to simulate the short-term aging of asphalt binder and obtain a binder that has reliable similarity to binders found in the field. Also, a dynamic creep test was performed at 40°C and 60°C at two stress levels (100 and 300 kPa), and a dynamic shear rheometer test was conducted at 58°C, 64°C, 70°C, and 76°C. The results revealed that the use of 3% and 5% ceramic fibers results in the best performance in terms of reducing the potential of rutting in stone-matrix asphalt. The results obtained in terms of the rheological properties of asphalt binder based on the dynamic shear rheometer test also showed that the incorporation of ceramic fibers increased the rutting parameter (${\mathrm{G}}^{*}/\sin \delta$) of asphalt binder. Moreover, the results of statistical tests indicated that the use of ceramic fibers up to 3% in all the utilized stone-matrix asphalt samples improved the performance against rutting.

The comparative performance between steel slag (S) and limestone (L) as aggregates in dense-graded asphalt concretes were investigated in this research. The performance tests for fatigue cracking were undertaken using indirect tensile strength (ITS) tests, indirect tensile fatigue life (ITFL) tests, and indirect tensile resilient modulus (${\mathrm{M}}_{\mathrm{R}}$) tests. Dynamic creep tests and wheel tracking tests were also performed to assess the rutting behavior of these pavement materials. A heavy metal leaching test was also carried out to ensure that asphalt concrete with the usage of S, as a sustainable aggregate, was safe for the environment. The results indicated that asphalt concretes with S had better Marshall’s stability than the asphalt concretes with L, even though they had slightly less ITS values. The ITFL and ${\mathrm{M}}_{\mathrm{R}}$ of S asphalt concretes were higher than those of L asphalt concretes, indicating higher fatigue cracking resistance. The ${\mathrm{M}}_{\mathrm{R}}$ of S asphalt concretes were found to be higher than the required 3,100 MPa value recommended by AASHTO, while L asphalt concretes did not meet this requirement. In addition, the dynamic creep and wheel tracking test results showed that the S asphalt concretes had superior resistance to permanent deformation as compared to the L asphalt concretes. The usage of medium-sized S aggregate in developing asphalt concrete was evidently more sustainable in terms of engineering and economic perspectives than the usage of large-sized S aggregate. The research results indicated that the sustainable usage of S in asphalt concrete was suitable for the development of heavy traffic volume roads.

This paper investigates the influence of corrosion on the postyielding performance of steel reinforcement. Artificial corrosion was induced to the steel reinforcement based on mechanical methods. Different corrosion morphologies were considered in the investigation, including pitting (nonuniform) corrosion and uniform corrosion. The impact of artificial corrosion on the postyielding performance of the steel reinforcement was analyzed according to the experimental tests. The results show that the corrosion morphologies and corrosion degrees influenced the configuration of stress-strain curves significantly. For the uniform corrosion, the configuration of the postyielding curves consisted of the yield plateau and the strain hardening stages even though the corrosion degree reached 50%. While for the pitting corrosion, the postyielding behavior of the steel reinforcement got degraded even more seriously than that of the specimens with uniform corrosion corresponding to the same corrosion degree. Moreover, when the corrosion degree got over 15%, the yield plateau disappeared due to the pitting corrosion.

The present paper aimed at studying the effectiveness of waste vegetable oil (WVO) as rejuvenator in restoring the desired properties of recycled asphalt mixes. The effectiveness of rejuvenators was first evaluated based on aging resistance, rutting, and fatigue performance of rejuvenated bitumen blends of recovered reclaimed asphalt pavement (RAP) bitumen and virgin bitumen. Bitumen was also characterized chemically by conduction thin layer chromatography–flame ionization detector (TLC–FID) analysis and Fourier transform infrared spectroscopy (FTIR) analysis. The rutting and fatigue resistance of asphalt mixes with high RAP content (60% and 90%), and rejuvenator was also evaluated. Comparison of the results of TLC–FID analysis on RAP bitumen and rejuvenated bitumen suggested that the WVO was able to reinstate the lighter fractions of bitumen. Two new peaks were observed in rejuvenated bitumen FTIR absorbance spectrum at 1,744 and 1,160 cm^-1. These peaks respectively correspond to C═O and C─ O─ C stretches of saturated fatty acid ester, which is a major component of WVO. Multiple stress creep and recovery test on bitumen and a wheel-tracker test on asphalt mixes suggest that the rutting performance might not be an issue if the rejuvenator dosage selection is based on the target viscosity (at 60°C) or the softening point of the virgin bitumen type that is commonly adopted by the applicable road agency. Rejuvenated bitumen, when evaluated based on a linear amplitude sweep test, has shown inferior fatigue resistance compared to virgin bitumen. Such behavior of rejuvenated bitumen could be attributed to the presence of a high concentration of more reactive unsaturated fatty acids inherited from WVO. However, from indirect tensile fatigue tests on the asphalt mixes, it was found that the fatigue performance of rejuvenated recycled asphalt mixes is satisfactory.

Millions of cubic meters of marine sediment are dredged from Chesapeake Bay waters in Maryland each year. Due to their low-strength characteristics, the sediments often need to be amended with other geomaterials for potential use in earthworks projects. However, the environmental effects of the blend need to be thoroughly investigated prior to such use. In an effort to alleviate storage challenges for these dredged sediments, the current study investigates their potential use in highway embankments upon amending them with recycled concrete aggregate (RCA). The laboratory compaction test data indicate that RCA amendment causes an increase in gravel content, decreases the liquid limit, and increases the unit weight of the virgin sediments, resulting in a typical material for embankment construction and satisfying the minimum unit weight requirements set by the local highway authority. ${\mathrm{pH}}_{\mathrm{stat}}$ tests and sequential column leaching tests were carried out to evaluate variations in leachate concentrations across pH and time. The RCA addition causes a slight increase in leached metal concentrations; however, all metals except copper remain below water quality limits. The numerical simulations showed that, while contaminant concentrations in leachate from the sequential column leaching tests at times exceed the water quality limits, those concentrations are dissipated and diluted rapidly in situ both in surface waters and in groundwater, and thus are not likely to be of concern.

Due to massive development, population explosion, and urbanization, an enormous amount of plastic waste is generated, mainly consisting of bottles made of polyethylene terephthalate (PET). The disposal of these PET bottles is a challenge to society. This paper studied bituminous concrete (BC) mix modified with PET bottles in shredded form with variable size and content by the dry process. The PET content ranged from 3% to 10% of bitumen content and was studied in three sizes (4.75–2.36, 2.36–1.18, $0.60–0.30\mathrm{mm}$). Performance tests such as Marshall stability, flow value, indirect tensile strength (IDT), and moistness vulnerability of the modified BC mix were performed, and the outcomes were compared with those of untreated bituminous concrete mix without PET. The modified BC mix had a higher resistance to moisture and improved performance against deformation and cracking, because the Marshall stability and IDT improved.

The modulus of the asphalt layer in a pavement structure subjected to vehicular loading is different from that subjected to falling weight deflectometer (FWD) loading. A comprehensive approach is developed in this study to investigate the relationships between asphalt layer moduli under the two loading conditions. Two full-scale asphalt pavements named flexible pavement and semirigid pavement were constructed. The structural responses of these two pavements under vehicular and FWD loadings were measured. The modulus master curves of asphalt layers in field pavements were developed based on the measured responses and the finite-element model. The developed master curves were found to be able to accurately predict asphalt layer moduli under either vehicular or FWD loading. Based on the obtained master curves, the ratios of asphalt layer moduli under vehicular loading to those under FWD loading were calculated under various conditions. The calculated ratios are mostly lower than 1.0 in a wide range of vehicular speeds, regardless of temperatures. The ratio increases with rising vehicular speed, but does not show a consistent trend with pavement temperature. In particular, the ratios are noticeably lower at intermediate temperatures than those at either high or low temperatures. Hence, the use of FWD to determine the stiffness moduli of asphalt layers may significantly overestimate their true stiffness in typical in-service conditions. The methods and findings in this study may provide a useful reference to correlate asphalt layer moduli between vehicular loading and FWD loading.

Temperatures above 160°C are usual to obtain adequate viscosity of the asphalt binder in the mixture to coat and compact the mineral aggregate. However, there is higher fuel consumption, greater exposure of workers to fumes, and higher emission of greenhouse gases. As a solution to this high working temperature, the proposal to use warm mix asphalt (WMA) mixtures emerged. Studies show the effectiveness of WMA mixtures modified with additives capable of lowering the mixing and compaction temperatures of asphalt mixtures without changing their characteristics. This study investigates the possibility of producing WMA mixtures modified with the CCBit additive and carnauba wax by studying their rheological properties. The experimental results obtained reveal that both additives used obtained a reduction in the compaction and mixing temperatures, with the ideal content for CCBit mixtures between 2.0% and 2.5% and 2.0% content for carnauba wax, which presented better workability and increased the asphalt binder strength.

Industrially produced metakaolin may contain raw kaolin residues. Therefore, the aim of this work was to determine the influence of kaolin remains in the metakaolin on the final geopolymer quality. A series of mixtures based on metakaolin (Mefisto L05 by CLUZ Nove Straseci, Czech Republic) was prepared with the 0%–50% by weight gradual addition of raw kaolin, and the mechanical strength of the final geopolymer products was tested. It was found that up to a 20% by weight amount of kaolin in metakaolin does not weaken the geopolymer’s performance. Moreover, a geopolymer made of metakaolin with 2%–4% by weight of kaolin showed slightly better mechanical properties than the geopolymers made from metakaolin itself.