Journal of Materials in Civil Engineering

Reflective cracking is one of the major forms of deterioration in pavements and is very common when hot-mix asphalt (HMA) overlays are constructed over a base with discontinuities in its surface. This issue has not received proper attention compared with classical fatigue cracking. However, it is a major concern during the selection of asphalt mixture surface courses for pavements with an underlying cracked base. This work identified the most appropriate testing device for investigating the resistance of asphalt mixtures to reflective cracking in the laboratory. An in-depth review of the available literature was conducted and 17 reflective cracking testing devices were evaluated, among which best three were chosen based on their availability, ease of use, variability, repeatability of the test results, and field validation. It was concluded that the Hamburg wheel tracking tester (HWTT), the wheel reflective cracking (WRC) apparatus, and the upgraded Texas Transportation Institute (TTI) overlay tester are the best available devices to examine resistance to reflective cracking in the laboratory.

The objective of this paper was to investigate the evolution of air voids (AV) and deformation and the failure mechanism of porous asphalt (PA) mixtures under high temperatures. An advanced repeated loading permanent deformation (ARLPD) test was used to investigate the high-temperature permanent deformation of PA mixtures. A staged ARLPD test (first stage test, secondary stage test, and third stage test) and a staged X-ray computed tomography (CT) scanning test were designed to evaluate the three-stage evolution of the AV and deformation in the ARLPD test. Total AV content ($A{V}_{\mathrm{total}}$) and interconnected AV content ($A{V}_{\mathrm{interconnected}}$) decrease in the first stage, and $A{V}_{\mathrm{total}}$, $A{V}_{\mathrm{interconnected}}$, and the number of AV ($A{V}_{\mathrm{num}}$) increase in the secondary stage. $A{V}_{\mathrm{total}}$ and $A{V}_{\mathrm{interconnected}}$ decrease and $A{V}_{\mathrm{num}}$ increases in the tertiary stage. Based on the changes of AV and intuitive image analysis, the failure mechanism of PA mixtures was discussed. The first stage is a densification stage, during which radial deformation develops faster than vertical deformation. Densification failure was observed in the tertiary stage, which shows that vertical deformation develops faster than radial deformation.

The novelty of the paper is to identify the scientific patterns of the selective effect of multicomponent fine mineral additives on the synthesis of new growths and the microstructure of gypsum composites. Gypsum binders obtained using the waste of wet magnetic separation of ferruginous quartzite, nano-dispersed silica powder, chalk, and superplasticizer were prepared as novel compositions, on the basis of which rational compositions of gypsum composites for various purposes are created. The strength characteristics of concrete mixes were researched by a series of tests (compressive strength and flexural strength). In addition, the durability characteristics (freeze-thaw resistance and water impermeability) as well as thermal conductivity were determined by standard techniques and confirm the creation of durable composites with high exploitation properties. Besides, the microstructural, morphological, and thermal properties of such composites at 28 days of curing were determined. The technology of composite gypsum binder preparation has been developed, contributing to the uniform distribution and optimization of the particle size distribution of its components. It also accelerates the process of microstructure formation and increases the compressive strength in the early periods of hardening by 40% and at 28 days old by 58% with compressive strength values of up to 26 MPa and a water resistance coefficient of 0.82–0.89. Rational compositions of gypsum composites are offered for various purposes with multicomponent fine-dispersed mineral additives and superplasticizer, reducing their water demand by 19% with little or no reduction in the strength of equal-moving mixes and slowing down the setting time by 3 times (up to 22 min 20 s).

Although the importance of the interfacial transition zone (ITZ) to sulfate attack is obvious, the relation between the ITZ and the rate of degradation is still unclear. The impact of ITZ volume content on the degradation of concrete, including length, mass, and elastic dynamic modulus ($E_d$) variation, fully immersed in magnesium sulfate solution were investigated in this work. The microstructure was analyzed by backscattered electron imaging (BSE) and energy dispersive X-ray spectroscopy (EDX) mapping analysis. The performance of concrete exposed to magnesium sulfate highly depended on the aggregate and the composition of raw materials. There was a trend toward more serious deterioration with increasing ITZ in the reference and limestone filler blended group after 12 months of exposure. The degradation of specimens made with slag was independent of the variation of ITZ content. Gypsum tended to precipitate in the ITZ under magnesium sulfate attack. The EDX analysis confirmed the decomposition of C-S-H, accompanied by the formation of degradation products M-S-H.

A method was investigated to determine concrete durability by measuring the carbonation depth and chloride ion (${\mathrm{Cl}}^{-}$) penetration depth. Under the proposed method, a 1- or 2-mm-diameter hole was drilled into a concrete surface and the hole’s walls were sprayed with either a phenolphthalein or silver nitrate solution to observe the carbonation depth or ${\mathrm{Cl}}^{-}$ penetration depths using an inserted 0.6-mm-diameter fiberscope. This method is intended to be a highly accurate, semidestructive test of concrete durability that causes minimum damage to the inspected concrete structure. It was found through visual observation and image analysis that when coloring the 1-mm drill holes with phenolphthalein, the holes had to be sufficiently dried before observation, whereas when coloring with silver nitrate, no special pretreatment was required. The results of the proposed method were compared with measurements using calipers on cut surfaces, demonstrating that the proposed method yields highly reliable measurements of parameters describing concrete durability.

Low temperature has a tendency to cause microdamage in asphalt concrete because of the relative thermal contraction of mastic and subsequent accumulation of thermal stresses. This paper presents the applicability of an energy-based micromechanical approach for assessing low-temperature damage and recovery in asphalt concrete based on a newly developed noncontact resonance testing. The principle of local energy balance and redistribution was applied to estimate average thermal microcrack length by considering local thermal strain energy release zones and surface energy of cracks initiated at preexisting air voids. A damage probing test was carried out by thermal loading and unloading of five different asphalt concrete specimens. The test was carried out by using a recently developed noncontact resonance method. The stiffness modulus was determined from the resonance test and utilized in the energy balance and redistribution formulation. Coefficients of thermal contraction of the specimens were also determined based on the noncontact resonance test and by applying the principle of the impact-echo method and calculating changes in thickness of the test specimens.

Chemically induced calcium carbonate precipitation (CCP) using calcium hydroxide (CH) and carbon dioxide (${\mathrm{CO}}_2$) was employed to clean sand for improving its strength. Joomunjin sand was mixed with 2% CH and 10% water, and then cured in a ${\mathrm{CO}}_2$ chamber under 100 or 200 kPa for 2 h. The treatments were repeated 1, 5, and 10 times. At the last treatment cycle, the treated sand was compacted into a mold for testing. A series of unconfined compression and direct shear tests were conducted on the treated sand to evaluate the effects of the CCP on the strength of the clean sand. Scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) analysis were performed to evaluate the CCP and microstructure of the treated sand. The experimental results indicated that the effect of change in the ${\mathrm{CO}}_2$ chamber pressure on the calcium carbonate content (CCC) was insignificant due to the low pressures applied. As the number of treatments increased from 1 to 10, the CCC increased from 2% to 23%, resulting in increases of the unconfined compressive strength (UCS), and friction angle of treated sand. The efficiency of converting CH to ${\mathrm{CaCO}}_3$ reached 87% after 10 cycles. The UCS increased from 51 to 364 kPa as the number of treatments increased from 1 to 10. The friction angle and cohesion of clean sand also increased from 32° and 0 kPa to 49° and 53 kPa, respectively.

The strength characteristics of bolts under ambient and fire conditions are among the major factors affecting the performance of bolted connections in steel structures. At present, the evaluation of fire resistance of steel bolts is done under the assumption that the mechanical properties of steel bolts are identical in both the heating and cooling phases of fire. The reason is the scarcity of data regarding the high-temperature properties of steel bolts in the cooling phase of fire. This paper is an attempt to experimentally study the high-temperature mechanical properties of Grade 10.9 high-strength steel bolts both in the heating and cooling phases of fire. The researchers carried out steady-state tension tests on bolt specimens in a temperature range of 20°C–800°C. The test results were used to assess the stress-strain response and the ultimate and yield strength as functions of temperature for Grade 10.9 bolts. Furthermore, the influence of the heating-cooling process on the microstructure and failure mode of bolts was investigated. The obtained data show that Grade 10.9 bolts experience rapid decrease in strength at temperatures exceeding 400°C and respectively reach 40% and 5% of their original strength when heated to 600°C and 800°C. Test data also indicate that Grade 10.9 bolts act differently in the cooling phase compared with the heating phase with respect to strength degradation. This is due to the irreversible transformations that occur in the microstructure of bolts when they are exposed to a heating-cooling cycle.

Asphaltic material is a kind of viscoelastic material, and its performance varies with test and materials conditions, such as stress states, temperatures, aging degree, gradations, and binders. The anti fatigue design of asphalt pavement has been stifled by these interferences. The objectives of this study are to reveal and compare the effects of loading frequency and aging degree on the fatigue performance of asphalt concretes. A series of tests for tensile fatigue on aged and unaged asphalt concretes were conducted at different loading frequencies. The theory of stress ratio considering different test conditions was proposed based on the conclusion that the stress ratio varies with stress loading rates. Then, the $S\text{-}N$ fatigue equation was modified based on the theory. The fatigue test results were analyzed with the modified $S\text{-}N$ fatigue equation to characterize the fatigue performance of asphalt concretes aged to different degrees under different loading frequencies. The different effects of these two factors on the fatigue characteristics of asphalt concretes were analyzed and compared. It could be found from the results that the influences of loading frequencies and aging degrees on fatigue characteristics of asphalt concrete were different. The fatigue test results of asphalt concrete under different loading frequencies could be characterized by one fatigue curve fitted by the modified $S\text{-}N$ fatigue equation. It meant that the effects of loading frequency on fatigue were equivalent to the stress level. The fatigue test results of asphalt concrete with different aging degrees were fitted into different fatigue curves, respectively. The asphalt concretes aged 1 day had better fatigue life and more stable stress sensitivity than unaged asphalt concrete. When the aging degree was over 1 day, the fatigue performance deteriorated with the increase of aging degree. Moreover, it could be observed that the strength increased with the aging degrees when it was measured by the standard test loading rates. However, when the loading rates increased to a certain range, the contrary conclusion could be obtained because the viscoelasticity of asphalt concretes changed due to aging.

The objective of this paper is to evaluate the effect of different aging times on the performance of styrene-butadiene-styrene (SBS) copolymer–modified asphalt. Two kinds of SBS-modified asphalt with different SBS contents were selected, and a self-developed indoor aging equipment simple-aging test (SAT) was used to age the SBS asphalt binder for different times and different temperatures. The penetration, softening point, ductility, and Brookfield viscosity of the aged samples were tested, and the rheological properties of the aged samples were tested by dynamic shear rheometer (DSR). It was found that the rheological behaviors of the aged samples at high, medium, and low temperatures were closely related to the aging time and SBS contents. In addition, during certain aging temperatures and times, different physical and rheological indexes showed that the performances of SBS-modified asphalt after SAT was similar to that after rolling thin-film oven test (RTFOT) and pressurized aging vessel (PAV).

This study investigates the performance of multiple sections of the interstate system in Arkansas through the laboratory testing of 270 field cores taken from ten sections of I-30 and I-40. These roadway sections are defined by the state agency as good, medium, and poor performed sections based on the agency’s guidelines, experience, and judgment. This study intends to use the fundamental properties to define the pavement condition and support the agency to assess the pavement condition. Intentionally, this study proposes a method to determine the pavement condition of the interstates and aims to support the agency to make the decision of future preservation, maintenance, or rehabilitation. The air voids, fracture energy, dynamic modulus, and bond strength are evaluated with the field cores taken from the selected sections. A ranking method using the results of the laboratory tests is proposed to divide the interstate sections into three groups. It is found that the groups generally match the agency defined good, medium, and poor conditions. However, there are exceptions in which the group method does not completely agree with the agency’s pavement condition. Finally, correlations among the laboratory test results of field cores and in-service pavement conditions such as the international roughness index (IRI) and rut depth have been established. The laboratory test results are statistically correlated with the rut depth, but no significant correlation between the laboratory test results and IRI has been observed. Specifically, the air voids and dynamic modulus of the bottom surface layer are related to the rut depth of the left lane. Interestingly, the weighted bond strength between bottom surface course and binder course layers at 54°C is found to be related to the rut depth of the right lane. The traffic volume has been found to be well-correlated with the IRI.

Limited investigations evaluated the synergistic effects between ceramic waste powder (CWP) and blast furnace slag (BFS) on the pozzolanic activity and thermal properties of cementitious materials. In this paper, tested binders were produced by substituting the cement by either 20% CWP, 40% BFS, or combinations of 20% CWP and 30% BFS; the physicochemical characterizations were performed at various hydration ages. Scanning electron microscopy (SEM) images showed that the calcium hydroxide crystals are particularly visible in the paste prepared with cement only, while these crystals are considerably reduced for the paste containing CWP and BFS additions. Such results were confirmed by the Frattini and strength activity index tests, reflecting the occurrence of synergistic reactions that enhanced the pozzolanic reactions and led to increased amounts of calcium silicate hydrates. Regardless of the firing temperature, mortars prepared with a ternary binder composed of cement, CWP, and BFS exhibited improved residual strength and thermal conductivity. Such data can be of particular interest to cement producers and concrete technologists seeking improved sustainability and recycling processes of CWP materials.

In this study, the effect of aggregate gradation on asphalt mixture compactability was investigated. Based on different combinations of coarse and fine aggregates, four gradation zones were defined: coarse pack, coarse dense pack, fine dense pack, and fine pack. Two main compaction parameters (the compaction slope and initial density) and three gradation parameters (chosen to describe the representative size and uniformity of the gradation) were compared. Statistical analyses indicated a significant correlation between the two compaction parameters as response variables and three gradation parameters as explanatory variables. These relationships were used to determine the optimum aggregate gradation with respect to asphalt mixture compactability and rutting performance. The models developed using the gradation parameters were used with two independent data sets (one from a laboratory experiment and one from a field project) to show that the parameters can predict the compactability behavior of asphalt mixtures.

The eco-binder with optimized fractions of ternary solid waste materials of ground granulated blast furnace slag (GBFS/slag), class F fly ash (FFA), and circulating fluidized bed combustion (CFBC) fly ash was successfully used to manufacture no-cement self-compacting/self-consolidating concrete (NC-SCC). In the current study, the enhancement of mechanical and durability properties of NC-SCC with FFA was evaluated using the experimental testing of compressive strength, water absorption, sorptivity, dynamic elastic properties, and ultrasonic pulse velocity. Experimental results showed that addition of FFA at 30 wt% as partial replacement of slag was considered as the optimum value to produce the NC-SCC with the highest mechanical properties including compressive strength, dynamic moduli, and superior durability properties due to the lowest water absorption and volume of permeable voids computed from the test on initial and secondary rate of capillary absorption. Microstructural performance detected by using scanning electron microscopy (SEM) obviously supported that the structure of interfacial transition zone between binder and aggregate of the NC-SCC with optimized FFA addition seemed to be strengthened by the extra hydration products contributed to the FFA particles.

The aim of this work was to investigate the influence of tribochemically activated biomass fly ash on a sulfate attack of cement stone. A weight of 5%, 15%, and 25% of the portland cement were replaced with biomass fly ash. The samples were hardened for 28 days in water and then soaked in a 5% sodium sulfate (${\mathrm{Na}}_2{\mathrm{SO}}_4$) solution for 9 months at 20°C. The sulfate attack process was investigated by an X-ray diffraction (XRD) and thermal analysis (TA) and by estimating the compressive strength and mass loss of the samples. It was found that the addition of biomass fly ash increases the resistance of cement stone to a sulfate attack. The modified cement samples displayed a higher compressive strength and lower weight loss if compared to the ordinary portland cement samples. The biomass fly ash, as a source of additional alkali and due to a better particle distribution, slows down the involvement of Portlandite into an ettringite formation reaction and the decalcification of the calcium silicate hydrates.

Quantification of the fatigue life of warm mix asphalt (WMA) is challenging due to various factors such as the extent of aging and moisture susceptibility, to mention a few. Hydrated lime as an antistripping material can enhance the fatigue life of moisture conditioned WMA mixture; however, due to the filler effect of lime, the fatigue life can be reduced. In this investigation, samples of hot mix asphalt (HMA) and WMA with and without hydrated lime were subjected to fatigue testing using four-point bending at three strain levels (400, 600, and 800 microstrain) for unconditioned and moisture damaged conditions. The collected data was analyzed appealing to various post-processing methods, and it was seen that the beneficial effect of warm mix additives or hydrated lime was seen at lower strain level (400 microstrain) and not at higher strain levels (600 and 800 microstrain) based on the evolution of flexural stiffness and energy dissipation.

This study aims to evaluate the effect of microwave radiation on the self-healing performance of asphalt mixture. Fracture-healing-fracture test was conducted via semicircular bending (SCB) test and microwave heating. The ratio of tensile strength before and after healing was defined as healing index ($HI$), which was used to evaluate the self-healing properties of asphalt mixture. The self-healing performance was investigated by considering heating time, microwave power, and temperature. Surface temperature of two kinds of specimens showed a good binary linear regression relationship with heating time and microwave power. The increase of heating time and microwave power could promote the self-healing behavior in a certain range, which was mainly related to the temperature of the asphalt mixture after microwave heating. The two kinds of specimens had good mechanical strength recovery when the surface temperature reached about 80°C.

The phase structure and corrosion resistance of uncoated, pure enamel-, double-enamel- and triple-enamel-coated hot-rolled plain steel bars were investigated by X-ray diffraction (XRD), laser microscopic Raman spectroscopy, open-circuit potential (OCP), electrochemical impedance spectroscope (EIS), and potentiodynamic polarization curves. Raman spectroscopy tests demonstrated that the crystal phase is dominant on the surface, whereas the amorphous phase was observed in the cross-sectional area and decreased with an increase of distance from the steel-coating interface. The crystal phase decreased and there was almost no amorphous phase after immersion in 3.5% by weight NaCl solution. Electrochemical tests showed that both double-enamel- and triple-enamel-coated steel bars had approximately similar corrosion resistance, which was higher than that of pure enamel-coated steel bars.

Adding phase-change material (PCM) into the asphalt mixture has the potential to solve the temperature-related problem of asphalt pavement. During the phase transformation, NiTi alloy is still solid with good physical and mechanical properties. Therefore, no leakage and volatilization would occur, which are common problems occurring in the application of other kinds of PCMs. Equal volumes of NiTi alloy phase-change energy-storage particles are used to replace fine aggregates with corresponding particle diameter to prepare NiTi alloy phase-change heat storage asphalt mixture in the research. The admixture of NiTi alloy phase-change energy-storage particles could reduce the water stability of the asphalt mixture, but the adverse effect was not significant. When the phase change of NiTi alloy energy-storage particles occurred because of an increase in environment temperature, the heating rate of asphalt mixture was reduced due to the phase-change heat storage effect of NiTi alloy phase-change energy-storage particles. If there was more admixture, then the rate at which the mixture heats up would be slower. The indoor stimulated thermoregulation test showed that when the substitution rate of NiTi alloy phase-change energy-storage particles was 12% by weight, the maximum temperature difference between NiTi alloy phase-change heat storage asphalt mixture and ordinary asphalt reached 4.3°C.

Asphalt pavements on steep slope sections in regions with seasonal freezing are affected by loads and the environment, and the shear resistance and shear fatigue performance attenuation of interlayer adhesive materials become increasingly severe. To study the effect of freeze–thaw cycles on shear fatigue resistance of asphalt pavement interlayer adhesive materials, an asphalt pavement interlayer shear fatigue test device was designed and self-assembled. The ultimate shear strength test of asphalt mixtures was determined using a universal testing machine. The interlayer shear fatigue of asphalt mixtures was tested, and the single factor analysis of shear stress ratio, loading frequency, temperature, and freeze–thaw cycle influence on the interlayer shear fatigue were discussed. The frequency, temperature, freeze–thaw cycles, and practical application parameters were corrected based on a prediction model for shear fatigue life under different shear stress levels, and a prediction model for interlayer shear fatigue life was established. The results show that the shear fatigue failure life of the same adhesive layer specimen decreases with the increase of the stress ratio, and is very sensitive to changes in the stress level. Furthermore, shear fatigue failure life and the stress level are related linearly in double logarithmic coordinates. The interlayer shear fatigue failure life and loading frequency have an exponential change trend. The higher the loading frequency, the greater is the shear fatigue failure between layers of asphalt pavement. The interlayer shear fatigue failure life of the different types of specimens decreases with the increase of the number of freeze–thaw cycles, and has a linear trend. The study results can provide a theoretical basis and technical support for asphalt pavement material selection and structural design on steep slopes in regions with seasonal freezing.

The use of recycled concrete aggregate (RCA) has substantially grown over the last several decades. RCA is a composite material composed of original virgin aggregates (OVA) and residual mortar (RM); it has been found that accounting for RM as part of the total mortar volume in the design of RCA concrete can improve its mechanical and durability-related properties. Moreover, this impact might even be enhanced according to the RCA’s innate quality and features. Yet, there are currently very few quantitative data and evaluation protocols highlighting this influence, especially for eco-efficient RCA mixes. This work presents an experimental (i.e., chemical, mechanical, and nondestructive) characterization of 35-MPa RCA mixes incorporating distinct RCA qualities (i.e., 25, 35, and 45 MPa) and types (crushed limestone versus quartzite gravel) and proportioned through the equivalent volume (EV) method. Results indicate that RCA features may impact the overall performance of RCA concrete; however, RCA particles with distinct features may still be considered for structural applications whether or not a proper mix-design technique is adopted. Finally, the EV method seems to be a suitable strategy to design eco-efficient RCA concrete.

The mechanical properties of poroelastic road surface (PERS) govern road performance and service life. The objective of this research was to evaluate mechanical properties of PERS mixtures with nine different material compositions by laboratory tests and determine the effect of material compositions. Dynamic moduli and phase angles of PERS mixtures with different contents of rubber particle were compared with those of stone mastic asphalt (SMA). Also, high- and low-temperature stability and water susceptibility of PERS mixtures were measured and compared. The impact of material composition on the performance of PERS mixtures was determined. The results showed that PERS mixtures performed much better than the SMA mixture in all respects except for water susceptibility. The rubber particle content significantly affected mechanical properties of PERS mixtures, which determined the polyurethane content needed. The high air void of PERS mixtures reduced water susceptibility noticeably. The PERS mixture with proper material composition exhibited good balanced performance, which hopefully would lead to pavement with a long life.

The development of cross-laminated timber (CLT) technology has revolutionized the construction industry, enabling wood into new markets and exciting large-scale applications. The traditional 90° layup of CLT, however, is rudimentary compared to most laminated composite materials (e.g., for the aerospace industry or sports equipment) and could be viewed as just the starting point for the next generation of mass timber panels. This study examines the effect of varying fiber orientation of the mid-layer of three-ply CLT on the shear properties of the panel. Short-span shear specimens were fabricated from eastern hemlock boards where the mid-layer was oriented at 30°, 45°, 60°, and 90° with respect to the panel’s major axis direction. Shear strength and deformation of the panels were measured following the three-point bending test according to ASTM D198. In addition, predictions were made using a shear analogy method and a 2D linear elastic finite element model for comparison with experimental results. The results show a general tendency for both major axis bending and shear properties to increase when changing the fiber orientation of the mid-layer from 90° to 30°. Moreover, mean values of effective shear stiffness ($G{A}_{eff}$) and shear strength ($F_v$) obtained from the CLT panel with 30° fiber orientation were 828% and 48% higher, respectively, than those for traditional 90° CLT. Finite element simulations were in good agreement with the experiments for 90° CLT; however, for angled CLT specimens, the finite element model and shear analogy method predicted higher deformation due to the biaxial shear stresses from off-axis loading and bending-twisting coupling in the mid-layer, which these stresses are not taken into account by either prediction method.

The stiffness of asphalt mixes is a fundamental property that plays an important role in determining the performance of asphalt pavement under traffic loading. The resilient modulus (stiffness) of asphalt mixes can be either determined using laboratory experiments or predicted through empirical methods based on asphalt components’ properties. This paper characterized the effect of recycled materials including recycled construction aggregate (RCA) and glass on the resilient modulus of asphalt mixes using both an empirical method and a series of laboratory experiments. In addition, the resilient moduli obtained from different methods for different asphalt mixes were compared, and the accuracy and reliability of different empirical methods were discussed accordingly. The outcomes indicated that in cases in which the value of resilient modulus cannot be obtained experimentally, empirical equations cannot well predict the actual resilient modulus. Furthermore, the addition of RCA and glass at a certain amount was shown to improve the resilient modulus of the asphalt mix. This may be attributed to the basic properties of RCA due to its smaller flakiness index and particle shape compared with virgin aggregates. These two parameters significantly affected the final performance of asphalt mixes.

The permeability of porous asphalt pavement is an important hydraulic property that is affected by the microstructure of connected pores. This paper investigates the pore characteristics and water flow pattern of open-graded friction course (OGFC) mixture using image analysis and numerical simulation. Firstly, four groups of OGFC samples were scanned by computational tomography (CT) to obtain the pore distributions and the shape parameters of voids (number of voids per unit area, the area ratio of voids to cross section, the equivalent circle diameter, and the ratio of the long and short axis in equivalent ellipse) along both horizontal and vertical directions. Secondly, the three-dimensional (3D) pore structure of the OGFC mixture was reconstructed by an image-processing technique. The connected pores were separated, and the pore length, pore curvature, and hydraulic diameter were calculated and analyzed. Finally, the two-dimensional (2D) water flow in pore structures was simulated. The results showed that the length and curvature of horizontal pores were larger than those of vertical pores, but the diameter was smaller for horizontal pores. It was found that pores had different distribution characteristics in the horizontal and vertical directions. The pore length and curvature along the vertical direction of the OGFC mixture were smaller than those along the horizontal direction, but the hydraulic diameter along the vertical direction was larger than that along the horizontal direction. The simulation results showed that the water flow rate in the horizontal direction was greater than that in the vertical direction when the gravity is not considered. With the increase of water pressure and the decrease of void ratio, the difference between horizontal and vertical flow rates became greater.

Durability has always been a major concern in concrete-based infrastructures. Alkali–silica reaction (ASR) is the result of a chemical reaction between hydroxyl ions in pore water and silica from aggregates and cement of the concrete matrix. Geopolymer is a type of alkaline reactivated binder which can be synthesized by a polycondensation reaction of geopolymeric precursors and alkali polysilicates. Due to the alkaline solution brought in by alkali polysilicates, it is intuitive that a higher alkaline concentration in pore solutions of geopolymer concrete will adversely affect long-term performance. This study researched the preceding hypothesis and reports the finding of an experimental investigation of alkali–silica reaction between reactive aggregates and the geopolymer matrix. Specimens were prepared using Class C fly ash with a high CaO content and three types of aggregates (granite, carbonate, and gravel), each with different alkaline activator ratios and ${\mathrm{Na}}_2\mathrm{O}$ doses. Each aggregate also had different percentages of silicate and aluminum content. Mechanical testing of potential resistivity of the aggregates was performed via length change. Pore solution of the hardened geopolymer concrete was extracted and the pH value of the pore solution was determined. Results suggest that the extent of ASR reaction based on the presence of all three types of aggregates in fly ash–based geopolymer concrete is substantially smaller than that of ordinary portland cement (OPC)-based concrete. Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) tests also revealed that the amount ASR gel formed in geopolymer is less than that formed in ordinary portland cement concrete. Hence, utilizing ASR vulnerable aggregates in the production of geopolymer concrete might be permissible.

This paper presents the influence of the loading velocity on the fracture response of mortars with both natural hydraulic and aerial limes under three different rates (loading-point displacement rates, $5.0\times {10}^{-4}$, $5.0\times {10}^{-1}$, and $1.6\times {10}^1\mathrm{mm}/\mathrm{s}$). According to the results, the fracture energy and the peak load are sensitive to the loading rate. The maximum dynamic increase factors (DIF), of the peak load are 1.4 and 1.6 for the natural hydraulic and aerial lime mortars, respectively, while it is 1.9 for the fracture energy for both mortars. Moreover, the increase in the peak load and fracture energy of the natural hydraulic lime mortar is basically the result of the viscous effect of free water in the mortar. However, for the aerial lime mortar, the rate effect is chiefly related to the crack path and propagation velocity.

An innovative masonry building system, the semi-interlocking masonry (SIM) building system, is being developed in the Centre for Infrastructure Performance and Reliability at The University of Newcastle, Australia. The major motivation in developing the system was to improve the seismic performance of masonry infill panels in framed construction. In seismic areas, SIM can be used as framed mortarless engineered panels, which have significant energy dissipation capacity due to friction on sliding bed joints between units induced during an earthquake. The mortarless joints of SIM can be laid dry or, to improve thermal insulation and water resistance of SIM panels, can have some nonadhesive joint filler. This study focuses on the frictional behavior of three different mortarless SIM bed joint surfaces (dry surface, surface with linseed oil–based putty, and surface with rubber foam tape) for two different types of SIM units (topological and mechanical SIM units). The investigation aims to replicate realistic boundary conditions and loading regime using a modified couplet shear test setup. The constant precompression potentially induced in a masonry infill panel was applied by the static gravity load. Tests were designed to simulate relative sliding of SIM units during earthquakes over the service life of a panel: 160 sliding cycles of $\pm 1.0\text{-}\mathrm{mm}$ relative displacement applied dynamically ($100\mathrm{mm}/\min$). In addition, one cycle of $\pm 10.0\text{-}\mathrm{mm}$ displacement was also applied statically ($10\mathrm{mm}/\min$) for comparison to dynamic frictional behavior. The load-displacement history was recorded. The paper expands significantly from the previously published conference paper and reports the results of this testing program in terms of the friction coefficient (based on Mohr-Coulomb failure criterion) and the energy dissipation characteristics for each type of joint (only for topological SIM unit).

Low-pressure cold spraying was used to deposit A5052 and Al coatings on structural Q355B steel to improve its fatigue performance. Through the experiments and finite-element simulation, the fatigue crack growth behavior of Q355B steel substrate after polishing, grit blasting, and cold spraying with A5052 and Al powders were compared and analyzed. The bonding strengths of coatings to the substrate surfaces were measured through tensile testing. Three-point bending testing, with fracture morphology analysis and extended finite-element simulation, was conducted to analyze the effects of cold spraying coatings on the crack growth of Q355B steel. Results showed that the effects of grit blasting and cold spraying with A5052 and Al powders, and their combined effect, were conducive to the enhanced fatigue performance of Q355B steel.

The pullout tests are performed to investigate the bond performance of steel bar in recycled coarse aggregate concrete (RAC) under salt-frost (S-F) and repeated loading, and compared with the bond performance of steel bar in RAC under S-F and monotonic loading by the authors. The results show that the ultimate bond strength for repeated loading decreased after S-F cycles, and the ultimate bond strength for repeated loading is lower than that for monotonic loading after the same S-F cycles. The peak slip for repeated loading increased after S-F cycles, and the peak slip of the specimens for repeated loading is higher than that for monotonic loading after S-F cycles. The ultimate bond strength prediction equation of steel bar in RAC under S-F and repeated loading is presented. The S-F cycle causes the bond stress to move toward the free end, and the repeated loading accelerates the transfer of bond stress to the free end.

Enamel coating is a novel type of coating for the corrosion protection of reinforcement in concrete. Recently, improved enamel coating was achieved using low-temperature sintering. This study aims to investigate the effect of coating cycles on the microstructure, adhesion, and corrosion resistance of a lower temperature sintered enamel coating. Enamel coated steel bars with single, double, and triple coatings (SC, DC, and TC, respectively) and uncoated (UC) steel bars were prepared. X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray (EDX) spectroscopy, and pull-off and salt spray tests were performed. The results showed that both the DC and TC had fewer defects and exhibited excellent corrosion resistance compared with that of the SC. However, the transition layer formed at the enamel/steel interface for the DC and TC steel bars weakened the coating adhesion. The related corrosion mechanism was illustrated based on two different corrosion modes: corrosion that occurred at holes (COH) and corrosion that occurred at microcracks (COM).

To investigate the corrosion characteristics of steel bars embedded in recycled concrete beams under static loads, 12 recycled concrete beams were designed for electrochemical corrosion test taking into consideration a combination of 3 types of recycled coarse aggregate (RCA) replacement ratios (i.e., 0%, 50%, and 100%) and 4 levels of static load (i.e., 0, 0.2, 0.4, and 0.6). The results indicate that the mass losses of longitudinal tensile reinforcement and stirrup increase with both the RCA replacement ratio and the applied static load level. For corroded beams with a 50% RCA replacement ratio, the effect of an increase of 0.2 in the applied static load level on the corrosion of longitudinal tensile steel bars is greater than that of an increase of 50% in the RCA replacement ratio. For corroded beams with the same RCA replacement ratio, the maximum mass losses of longitudinal tensile reinforcement and short limbs of stirrups in the tension zone of the beams have a linear relationship with their average mass losses, and there is a positive correlation in the corrosion degree between the short limbs of stirrups in the tension zone of the beams and the longitudinal tensile steel bar. There exists a linear relationship between the pitting factor of longitudinal tensile reinforcement and its average mass loss, and the pitting factor decreases with the increase in average mass loss, which indicates that the corrosion of longitudinal tensile reinforcement tends to be uniform along the length with its increasing average mass loss.

This work assessed the durability performance of concrete made with ordinary portland cement (OPC), portland pozzolana cement (PPC), OPC $+20\%$ fly ash, and OPC $+30\%$ fly ash subjected to sulfate-only and to conjoint chloride–sulfate environments. Results indicated that the degree of surface deterioration of the concrete was mitigated in concrete specimens kept in conjoint chloride–sulfate solutions compared with those kept in sulfate-only solutions. Reduction of compressive strength of concrete decreased with the increase of NaCl concentration in conjoint chloride–sulfate solutions. Blended cement concretes had better immunity to sodium sulfate attack, whereas OPC concrete had better immunity to magnesium sulfate attack. In the presence of sulfate and conjoint chloride–sulfate ions, the formation of various compounds in concrete which produce variations in concrete compressive strength was corroborated by the results of XRD and FESEM analyses. Reduction of the compressive strength of concrete in exposure solutions decreased in the order ${\mathrm{MgSO}}_4{>\mathrm{Na}}_2{\mathrm{SO}}_4>\mathrm{NaCl}+{\mathrm{MgSO}}_4{>\mathrm{NaCl}+\mathrm{Na}}_2{\mathrm{SO}}_4$.

Permeability of concrete is usually measured in laboratory conditions without loading, which can be completely different from that in service. This paper presents a new method to determine the permeability coefficient of concrete under applied loading, considering concrete plasticity. A dissipated energy–based approach is proposed to determine the damage variables for the concrete damage plasticity model. The developed method is verified with experimental results, after which a parametric study is conducted to identify the factors that affect the permeability degradation. It is found in the paper that the applied load is the governing factor for permeability degradation of concrete, and that the permeability degradation is influenced by grade of concrete, aggregate size, thickness of the interfacial transition zone, and the shape of aggregates. The significance of the developed method is that it can determine the permeability coefficient of concrete as a function of time with various constituent combinations and under any applied stresses, which would otherwise be impractical with experimental techniques.

Dry-lean concrete (DLC) lies below the wearing course of the rigid pavement section to overcome the major reasons for its failure, such as improper base support, seepage of underground water, and frost action. DLC is generally manufactured with a huge aggregate-to-cement ratio, which lies below the wearing course of the rigid pavement section. In this study, reclaimed asphalt pavement (RAP), a waste material, derived from the milling process of flexible pavement wearing course, has been used as a partial replacement of natural coarse aggregates in DLC made from portland pozzolana cement (PPC). Initially, the feasibility of using washed reclaimed asphalt pavement (WRAP) and comparing the results with dirty reclaimed asphalt pavement (DRAP) as a partial replacement of natural coarse aggregate has been investigated. It was found that WRAP gave better results as compared to DRAP for satisfying DLC conditions. The reason is demonstrated using SEM images showing variation in formation of CSH gel due to the presence of dust particles. Further, strength and durability properties (acidic environment, water absorption, and alkalinity) were determined to check its durability of WRAP-incorporated concrete (WRAPC). The percentage of WRAP and DRAP was varied from 0%–50% by weight of natural aggregate. Also, nondestructive tests like ultrasonic pulse velocity (UPV) and rebound hammer test were performed to determine the quality and dynamic young’s modulus of WRAPC. It was found that the optimal curing period and optimum WRAP addition were 21 days and 20% respectively. An equation has been developed to determine the optimum moisture content (OMC) for varying percentage of moisture and RAP content. The equation was validated with the results of researchers and a variation of only 3.3% was found. It was observed that 20% WRAP incorporated in DLC gives optimal results in terms of strength and durability.

The porous volume of cement-based concrete is the key to understand its mechanical properties and durability. In this research, we apply X-ray tomography (XRT) and focused ion beam/scanning electron microscopy (FIB/SEM) to scan the multiscale porous volume of concrete with a resolution from 25 μm down to 10 nm. Based on the three-dimensional (3D) images, the pore morphology, pore network representativity, porosity, pore network connectivity, and pore size distribution (PSD) in different scales are analyzed and further discussed. Results show one sample can hardly be representative for observed zones, especially for the FIB/SEM and XRT1 samples. Thus, three samples are applied to FIB/SEM and XRT1 imaging, which reduce the relative error of porosity from 31%–33% in the micron scale and 15%–36% in the nanoscale to 18%–19% and 9%–21%, respectively. The combination of porosity in a multiscale has a similar value with that measured by mercury intrusion porosimetry (MIP). Meanwhile, the combined PSD has a similar curve form and peak size to that of MIP, which implies that the combination of image analysis in a multiscale provides a preliminary view of a multiscale porous volume of concrete.

The use of reclaimed asphalt pavement (RAP) in neat asphalt mixtures has received significant attention because of its economic and environmental advantages. However, bitumen contained in RAP is severely aged; when RAP is blended with virgin asphalt at a high percentage, it can negatively affect the properties of the resulting blend. Therefore, recycling agents have been used to improve the properties of aged asphalt and consequently the performance of the mixture. This paper uses computational modeling and laboratory experiments to examine the role of chemical structure and the composition of recycling agents on their interactions with oxidized bitumen. To do so, rheometry as well as Fourier transform infrared spectroscopy, thin-layer chromatography with flame ionization detection, gel permeation chromatography, and contact-angle measurements were used to track changes in physicochemical and surface properties of oxidized bitumen in the presence of four recycling agents with widely different compositions. The study results show that oxidized bitumen became softer after adding recycling agents (regardless of their source) and that all recycling agents were able to increase the phase angle and the colloidal stability index of aged bitumen. However, not all the recycling agents restored molecular conformation. The most effective recycling agent was found to be recycling agent A, which led to a concurrent increase in the crossover modulus and crossover frequency of aged bitumen. In contrast, recycling agent C had the least effect on crossover values. Molecular dynamics simulation showed that recycling agent A restored molecular conformation and reduced the size of asphaltene nanoaggregates, while recycling agent C promoted agglomeration, causing an increase in the size of nanoaggregates. Recycling agent A was also effective in reducing the moisture susceptibility of aged bitumen, as shown by a smaller change in contact angle of aged bitumen between wet and dry, compared to other recycling agents. Based on the study results, the efficacy of a recycling agent in the deagglomeration of oxidized asphaltenes is shown by a concurrent increase in both the crossover modulus and the crossover frequency; these two rheology-based indicators can be used to distinguish recycling agents that can accurately be called rejuvenators.

The rheological behavior of dredged clays at various pore water salinities treated with portland cement was investigated for beneficial use in structural fill applications. The focus was on evaluating the effect of salinity on flowability and viscosity of dredged clays as fills. Flow and viscosity tests were conducted on clay specimens at high water contents prepared using a sodium salt solution at various salinities and blended with cement in different proportions. Results suggest that the increase in salinity can reduce the liquid limit and viscosity while increasing the flowability. The slump flow value systematically increases with the increase in salinity. All specimens exhibited Bingham plastic behavior when the shear rate was greater than approximately $10{\mathrm{s}}^{-1}$. The two parameters of the Bingham plastic model including dynamic viscosity and yield stress consistently decrease with increasing salinity. Moreover, the two parameters were found to markedly decrease with salinity when salinity is less than 4% and less significantly when salinity exceeds 4%. The empirical power-law function between dynamic viscosity and liquid index cannot fully characterize the viscosity of cement-treated dredged clays at various salinities. Two power function curves can be fit to data of slump flow values corresponding to two parameters, indicating that the slump flow uniformly decreases with the increase in each parameter.

With several countries halting coal combustion in favor of clean and renewable energy production, there is need for alternative mineral additions that can substitute for fly ash in concrete and bring about similar benefits. This study explores using waste-marble powder (WMP) as an economical and eco-friendly method for controlling the alkali-silica reaction (ASR). Reactive aggregates were used with WMP from the local marble industry (Pakistan) at various proportions ranging from 5% to 50% by cement mass. Strength activity index and thermal analysis tests were performed to examine the mechanical strength and hydration kinetics in mortar mixtures incorporating WMP. ASR expansion in mortar incorporating reactive aggregates decreased owing to WMP addition and was lower at 28 days than the limit of 0.20% for mixtures incorporating 30% or more WMP given in current standards. Whereas control specimens without WMP incurred surface microcracking due to ASR, specimens incorporating WMP remained intact. Scanning electron microscopy with energy disperse X-ray spectroscopy analysis showed reduction of ASR in specimens with WMP. Thus, it can be envisioned that using WMP as partial cement replacement creates an added-value application for an otherwise landfilled by-product and reduces harmful emissions from cement production, with the further advantage of mitigating ASR in concrete structures.

Engineered geomaterials are designed with functionalities on demand to address practical problems in the geoenvironment, such as filtration and/or retardation of environmentally hazardous substances. In this study, an engineered soil was introduced with controllable and reversible wettability stimulated by external temperature variation. This new geomaterial was envisioned to retard or accelerate water percolation through its mass with external stimulation when used as a barrier or a filter ex situ or in situ. The tunable wettability was implemented by grafting a thin film of thermal stimuli-responsive polymer [$\mathrm{poly}(N\text{-}\mathrm{isopropylacrylamide})$ (PNIPAAm)] on sand particles using the surface-initiated atom transfer radical polymerization (SI-ATRP) technique. The PNIPAAm has an easily accessible lower critical solution temperature (LCST), $\approx 32°\mathrm{C}$. The polymer-coated surface has hydrophilicity at temperatures below the LCST, and changes to hydrophobicity above the LCST. The material composition and structural conformation of synthesized polymer were examined by Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The roughness and thickness and the coverage of the polymer film on substrates were assessed by atomic force microscopy (AFM) and optical ellipsometry. Solid–liquid contact angles and water percolation behavior were examined to verify the wettability change on a surface-modified sand pack triggered by changing temperature externally. The thermal-sensitive wettability demonstration of the synthesized sand particles implies proof of concept for innovative applications of the technique in proactive hazard mitigation such as use as a tunable granular valve, barrier, intelligent fluid separator, or biofilter.

To study the cracking behaviors and deformation damage process of single-flawed red sandstone with different wavilness angles, a series of uniaxial compression tests are conducted to investigate the effect of wavilness angles on the mechanical characteristics of the flawed red sandstone as well as crack initiation modes and ultimate failure modes. The real-time cracking behaviors of single-flawed red sandstone specimens with different wavilness angles are monitored using acoustic emission (AE) and photographic capturing technologies. The relationship among the AE rate curve, axial stress-time curve, and cracking process is constructed to evaluate the macroscopic deformation characteristics of preflawed rock. Moreover, the deformation damage process of single-flawed red sandstone with different wavilness angles is studied by using multifractal theory. A quantitative criterion is developed based on multifractal parameters of the AE time series, and the combined application of multifractal parameters can be considered as a precursor in the deformation and fracture damage process of flawed rocks.

In order to improve the recycling efficiency of waste ceramic powder, the effect of ceramic powder on the freeze–thaw resistance of recycled concrete under different substitution rates is studied in view of the poor frost resistance of recycled concrete. Six groups of mixtures with ceramic powder substitution rates of 0%, 10%, 20%, 30%, 40%, and 50% are designed. Before the test, the porosity distribution, porosity, and permeability of each group of specimens are calculated based on the principle of nuclear magnetic resonance (NMR), and the relationship between porosity and permeability of recycled concrete with ceramic powder is established by MATLAB. After a round of freeze–thaw cycle, the mass loss rate and relative dynamic modulus of each group of specimens are measured. Based on the Palmgren theory, the reliability calculation model of freeze–thaw damage is established, and the residual life of each group of specimens is predicted. The results show that the dynamic modulus of elasticity decreases, and the mass loss rate first increases and then decreases. When the replacement rate of ceramic powder is 20%, the porosity and permeability of recycled concrete with ceramic powder are the smallest, and the freeze–thaw cycle resistance is the strongest. In addition, the reliability calculation model of freeze–thaw damage based on the Palmgren model has high reliability, which can directly reflect the relationship between the reliability of recycled ceramic powder concrete and freeze–thaw cycle and can be well applied in practical application.

Dynamic fragmentation of hot mix asphalt (HMA) under high strain rate loading can be expected under various situations, such as milling, earthquakes, or explosions. This paper reports on an empirical study that was conducted to investigate the dynamic fragmentation of HMA, specifically with respect to energy of impact during loading. Samples of a surface course HMA, compacted to similar densities, were subjected to a series of impact loadings with different energies. The depth of penetration into the sample, strains during loading, and the resulting fragment sizes were evaluated. Impacts with higher energy levels produced more fragmentation and larger fragments. Both penetration and strains showed significant effects of impact energies. The size of the fragments showed good correlation with impact energy. These results can be utilized for controlling reclaimed asphalt pavement (RAP) gradation from milling and, hence, among other things, for constructing longer-lasting pavements.

In the present study, a novel model is introduced for the prediction of a resilient modulus ($M_R$) of cohesive subgrade soils considering cone-penetration test parameters to establish correlations with the $M_R$. A reliable previously published database composed of 124 datasets was utilized for the development of the proposed model, which incorporates both cone penetration test (CPT) parameters and laboratory indices. In order to generate the predictive model, a hybrid algorithm combining a firefly algorithm with a multilayer perceptron neural network (FA-MLP) is proposed. The FA algorithm is employed in the MLP network structure to adjust the weights and the bias of the network and, hence, improve the overall performance of the network. The proposed FA-MLP formulation was found to have the capacity to predict, satisfactorily, the $M_R$ of cohesive subgrade soils using the results of the CPT test.