Journal of Materials in Civil Engineering

Since most of the available data regarding fiber-reinforced polymer (FRP)-confined columns has been generated from tests on small-scale cylinders, it is important to ensure that the proposed equations are truly representative of the actual behavior of large-scale columns. In this paper, mechanics solutions have been developed to show the influence of specimen size, that is both diameter and height, on the stress–strain relationship of axially loaded FRP-confined concrete cylindrical specimens using shear-friction theory. Two distinct cylinder failure modes have been examined: that of the circumferential wedge that is common in standard cylinders with aspect ratios of $2:1$; and that of the single sliding plane that occurs at higher aspect ratios. It is often quite difficult, if not impossible, due to the capacities of the testing machines, to test large or large-scale FRP-wrapped specimens under pure compression to extract their axial-stress/axial-strain relationships. It is shown in this paper through the mechanics of shear friction, how small-scale FRP-wrapped specimens suitable for compression testing can be designed so that the stress–strain relationship of the large scale member under pure compression can be extracted from those of the small test specimen.

This paper presents the results of an experimental investigation on chloride diffusion in plain concretes and reinforced concretes. Concretes were exposed to chloride environment simulated by a self-designed tidal circulation device for 35, 70, and 100 days. Chloride concentrations (${\mathrm{Cl}}^{-}$) in powder samples which were milled layer-by-layer from plain concretes and drilled along the direction of rebar from reinforced concretes were measured. ${\mathrm{Cl}}^{-}$ at the apex of the rebar were compared to that at the corresponding depth in plain concretes to study the blocking effect of rebar. Meanwhile, diffusion coefficients ($D_x$) at different depths were determined by applying Fick’s second law to study the depth-dependent characteristic of ${\mathrm{Cl}}^{-}$ diffusion. The results show that along the direction of penetration, $D_x$ decreases first and then increases; rebar does change the distribution of ${\mathrm{Cl}}^{-}$, and the larger the diameter, the greater the effect. The effect of rebar is not only embodied in the physical obstruction but also in the variations in concrete composition. Based on the results obtained, a quantitative chloride diffusion model considering rebar presence, depth-dependent characteristics, and time is given.

The aim of this study was to link the molecular weight (MW) of polycarboxylate superplasticizer (PCE) with the performance of cementitious system for the purpose of developing new products; PCE synthesized by copolymerization of methacrylic acid and methyl poly(ethylene oxide) methacrylate was characterized by proton nuclear magnetic resonance (${}^1\mathrm{H}\text{-}\mathrm{NMR}$) and gel permeation chromatography (GPC). The polycarboylate (PC) was separated into four fractions with different MWs using an ultrafiltration method. The interaction behaviors between PC fractions and cement particles were investigated by measuring the adsorption, zeta potential, and hydration. Results showed that PC fractions with medium MW showed a good dispersion and dispersion retention owing to the adsorption amount continuously increasing with time and delayed the longest cement hydration time. The highest MW of PC exhibited poor dispersion and dispersion retention, having the greatest adsorption amount on the cement surface and poor adsorption capacity in the later period, and carried out to promote hydration of cement compared with other polymers. It can be deduced that there was an ideal MW for the best different performance of the PC investigated. This can provide an important reference for optimizing the process parameters in the preparation.

The use of additives is one of the effective techniques adopted to improve pavement properties. Recently, hydrated lime has been categorized as a major additive in asphalt pavement because of its wide availability and relatively cheap cost. The main purpose of this study is to quantify the effect of hydrated lime on asphaltic concrete performance under varied temperatures of weather and in the application of different pavement courses, i.e. wearing (or surface), leveling (or binder), and base. Five different percentages of the hydrated lime additive, which were used as partial replacement of the conventional limestone filler, were investigated. Tests were conducted to evaluate the resistance to the Marshall stability, and the volumetric properties, the resilient modulus, and permanent deformation at three different temperatures. The experimental results have shown an expected improvement on the mechanical properties for all the designed asphalt concrete mixtures when using hydrated lime additive. The optimum hydrated lime contents for different course applications have been suggested.

A total of 12 multielectrode array sensors were utilized to assess the individual effectiveness of two corrosion inhibitors and one coating under cyclic deicer exposure conditions. There were four sensor groups, and each group consisted of nine-pin probes that were fabricated from 1008 carbon steel, 304 stainless steel, and 1100 aluminum, respectively. A total of two environmental exposure tests were conducted, in which 2.3% NaCl and 3.0% ${\mathrm{MgCl}}_2$ solutions were used as salt, respectively. The two tests each included eight environmental cycles and with 24 h per cycle. For all the exposed sensors, the most severe corrosion occurred at the beginning of the humidity stage. For sensors in the control group, ${\mathrm{MgCl}}_2$ exhibited a corrosion attack throughout the exposure period, whereas NaCl only exhibited an apparent corrosion attack during the humidity stage. Both the sensor corrosion rates and mass loss results indicate that the inhibitors had a much greater effect for ${\mathrm{MgCl}}_2$ than for NaCl. Although the coating showed significant benefits in protecting the metallic substrates, the cyclic exposure to ${\mathrm{MgCl}}_2$ led to greater coating deterioration than did NaCl. For validation, impedance measurements were conducted on carbon steel panels subjected to similar exposures, and three-dimensional laser profilometer scans were performed to characterize their surface morphology after the exposures.

A mathematical model for the transport process of migrating corrosion inhibitor (MCI) in cement-based material and a two-dimensional numerical solution method using commercially-available software are proposed. The numerical analysis results are in a good agreement with experimental data obtained from the two-dimensional absorption tests for nonreactive MCI but do not coincide with the data for reactive MCI. The reason behind may be that the latter reacted with calcium hydroxide (CH) in cement mortar and hindered the transport process. Therefore a modified transport model involving the pore-blocking effect of reactive MCI in cement-based materials is established according to the chemometrics method. The numerical and test results prove that the amendatory model is reasonable to understand the mass transfer of reactive MCI in cement mortar. Variance analyses of the factors in the model are also performed to find the key factor affecting the MCI transport process. A basic transport model and numerical analysis method of MCI in concrete is proposed. The model is corrected involving pore-blocking effect for reactive MCI based on chemical metrology. The numerical calculation results of the proposed model have a fine agreement with experimental results.

Titanium dioxide (${\mathrm{TiO}}_2$) is a photocatalyst that has the capability of accelerating the oxidation of nitrogen oxides (${\mathrm{NO}}_{\mathrm{X}}$) and other pollutants under ultraviolet (UV) radiation. A number of studies have been conducted on applying ${\mathrm{TiO}}_2$ onto pavement surface to purify exhaust emissions from vehicles. However, it remains a challenging task to effectively coat ${\mathrm{TiO}}_2$ to asphalt pavements to achieve durable air-purifying performance. This study aims to develop an innovative method, based on the breath figure (BF) process and Pickering emulsion effect, to coat ${\mathrm{TiO}}_2$ particles onto asphalt pavement surfaces. With this method, asphalt binder with micro pores filled with ${\mathrm{TiO}}_2$ particles can be coated to asphalt pavement surfaces. The micro porous structure of the coating material helps to provide larger contact area between ${\mathrm{TiO}}_2$ and UV, thus enhancing ${\mathrm{NO}}_{\mathrm{X}}$ degradation efficiency. Microscopic analysis on the coating material prepared using the new method demonstrated that ${\mathrm{TiO}}_2$ particles distributed well on the pore walls of the coating material, indicating that UV can reach ${\mathrm{TiO}}_2$ to activate the photocatalytic process. The nitric oxides (NO) removal efficiencies of the asphalt mixture specimens coated using this new method and the traditional water solution–based method after various numbers of surface abrasions were also measured by a custom-designed environmental test setup. It was found that this new coating method provided not only better NO removal efficiency, but also improved durability to maintain the degradation efficiency after tire abrasion, compared to the traditional method.

Wearing surfaces are integral parts for long-span orthotropic steel deck bridges and well-designed wearing surfaces will be able to carry the traffic crossing the bridge smoothly and maintain the operation of the bridge. However, until now a systematic procedure has still been necessary for designing such wearing surfaces. In this paper, an integrated procedure is proposed for designing the epoxy asphalt concrete (EAC)–based wearing surfaces. The proposed design procedure includes five major steps: data collection and preparation, epoxy asphalt concrete design, structure design, tolerance determination, and empirical validation. The design details for each step are described accordingly. In a case study, the proposed design procedure is demonstrated through applying this procedure on designing the wearing surface for the Second Nanjing Yangtze River Bridge located in Nanjing City, China. The case study results show that the proposed procedure can be applied to design a feasible wearing surface system on top of the long-span orthotropic steel bridge decks. Further investigations are recommended on extending the proposed procedure to accommodate other surfacing materials, advanced testing approaches, and local regulations, and a set of designing charts based on empirical evidences is also suggested to simplify and systemize further the design procedure.

Two most common distresses found in chip seals are raveling and bleeding. Although raveling is a process that continues throughout the whole service life of chip seals, current performance tests available for chip seals focus mainly on early raveling and bond maturation. In this study, chip seals binders from the field were extracted and recovered for two consecutive years. Rheological properties of original, field-aged, and laboratory-aged binders were compared. Results showed that pressurized aging vessel (PAV-) aging simulates 3 to 4 years of field-aging for hot asphalt and less than 3 years for emulsion. Strain tolerance, shear stress at failure, oxidative aging index, and yield energy of the binder were correlated with long term field performance (raveling). Shear stress at failure of field-aged binders showed strong correlation with long-term field performance, exhibiting an $R^2$ value of 0.95. However, yield energy (a product of strain tolerance and shear stress at failure) of original binder, which showed an $R^2$ value of 0.83 with long-term field distress rating (raveling), was recommended as performance parameter for chip seals binder.

Studded tire wear can lead to the severe deterioration of asphalt pavement; therefore, the reduction of studded tire wear is urgently needed to improve asphalt pavement conditions and save repair costs. Steel slag is a coproduct of the steel industry and features high hardness compared to conventional crushed aggregate, such as granite and limestone. This study evaluated the performance of hot-mix asphalt (HMA) that contains steel slag aggregate (SSA) as a surface material to mitigate studded tire wear. The physical properties of the SSA were assessed to determine its suitability in HMA. Four percentages (0, 20, 40, and 60%) of SSA were used in asphalt mixes, and the mix designs for the HMA were conducted in accordance with Superpave mix design. The performance of the mixes was evaluated comprehensively in terms of studded tire wear resistance, thermal cracking resistance, moisture susceptibility, and rutting. The results indicate that the addition of steel slag increased the mixtures’ studded tire wear resistance, dynamic modulus values, thermal cracking resistance, and rutting resistance. The inclusion of SSA had no effect on top-down fatigue cracking resistance and moisture susceptibility. Based on these laboratory test results, SSA could be especially beneficial in the northwest region of the United States in surface courses where studded snow tires are used regularly, and could be used to extend the service life of the pavement.

In this paper an energy-based approach has been proposed based on the principals of nonlinear viscoelastic fracture mechanics to determine the thermal fatigue life of asphalt mixes for the short-term aging condition at a constant temperature. The approach, presented in this paper for only one aging condition at one temperature, is considered in another paper as the basis for the development of a comprehensive model (TFCMODEL) by which the thermal fatigue life of various asphalt mixes may be predicted analytically for varying aging conditions and temperatures. To this end, a modified uniaxial test setup was designed to account for the effects of the bonding/friction condition between asphalt and base layers, and nonuniform distribution of stresses/strains within the asphalt layer depth. To characterize the thermal fatigue behavior of asphalt mixes, uniaxial thermal fatigue tests were carried out on the beam specimens at two aggregate gradations, two binder contents, two air void contents, one aging condition, one temperature, two bonding/friction conditions between the asphalt and base layers, and four cyclic loading patterns in both tension and compression, with three replicates. After determining the crack growth rate for the successive cycles, some empirical models were formed to predict the crack length and the maximum measured tensile/compressive loads as functions of the cycle number. Rate of dissipated pseudostrain energy, pseudo $J$-Integral, and the fracture parameters ($A$ and $n$) were then calculated for all the experimental combinations, and two empirical models were developed to predict the fracture parameters based on the viscoelastic properties of asphalt mixes. Finally, the thermal fatigue lives of asphalt mixes were obtained based on the change in the ratio of cumulative dissipated pseudostrain energy as the criterion identifying the thermal fatigue crack initiation and propagation.

Currently, the fatigue performance of asphalt concrete (AC) is predicted according to repeated traffic-induced tensile strain at the bottom of AC layer. Cyclic thermal strain caused by day-night temperature fluctuation is not considered because of the fact that there is no closed-form solution or model available for calculating thermal fatigue damage. This study, for the first time, develops a closed-form equation for calculating the temperature-induced fatigue damage of AC. To generate data, beam fatigue testing was conducted on three Superpave mixtures in the laboratory. The mechanical beam fatigue test data were correlated with the actual cyclic temperature loading test data. The developed model was then calibrated for field condition. Finally, the model was used to evaluate fatigue damages of randomly chosen 34 long-term pavement performance (LTPP) test sections from 19 states in the United States. Fatigue damage determined by the traditional pavement design software (which considers traffic-induced fatigue damage only) is compared with that by the combined traffic- and temperature-induced fatigue. The results show that the error may decrease by 14% through the incorporation of temperature-induced fatigue damage in the current design approach. Therefore, it is suggested to include the temperature-induced fatigue damage in the pavement design software.

This paper studies the response of Cu-Al-Mn superelastic alloy (SEA) bars to repeated tensile load at room temperature. The test specimens are three polycrystalline and one single crystal SEA bars of 11 mm diameter and 100 mm length. Strain-controlled tensile load is applied for 1,000 cycles with target strain amplitudes of 6–7%. In the test, variations are monitored in the stress-strain curve, recovery strain, elastic modulus, forward transformation stress, and damping ratio. All bars showed functional fatigue, or gradual loss of superelasticity, while they did not fracture by the end of the loading cycles. Full strain recovery was observed up to 50–100 cycles without any training beforehand, while a slight decrease of forward transformation stress was observed during these cycles. Then, a gradual loss of stress plateau and gradual increase of residual strain were observed up to 200–400 cycles. Afterward, a nearly linear response was observed. Microstructure and texture analyses suggest that both the grain sizes larger than the bar diameter and the uniform distribution of crystallographic orientations are possible reasons for avoiding premature fracture, which is often seen in polycrystalline Cu-based SEAs.

Accurate characterization of mechanical properties of asphalt binders plays an important role in the evaluation and selection of binders, and in the design and analysis of mixtures. In this study the modified Havriliak-Negami model previously proposed for complex modulus of asphalt concrete is extended to account for the steady-state flow behavior of viscoelastic liquid materials. The analytical forms of storage and loss modulus master curves are derived from the complex modulus model through complex algebra. The Kronig-Kramers relations of the model are satisfied so that various LVE functions are equivalent and the causality of the model is fulfilled. In addition, the same time-temperature shift factor applies to various LVE functions. Thus, the model is consistent with the LVE theory. The model is fitted to complex modulus test results of various asphalt binders. The results show that the model can accurately characterize the properties of asphalt binders, regardless of whether they show viscoelastic liquid or viscoelastic solid behavior. The results presented in this study together with those presented previously for mixtures indicate that the model provides a consistent and effective approach of characterizing the LVE properties of both asphalt binders and mixtures.

The dynamic compressive behavior of concrete is investigated using a $\mathrm{\Phi }74\text{-}\mathrm{mm}$ variable cross section straight taper split Hopkinson pressure bar (SHPB) apparatus in this study. In order to reduce and eliminate the waveform dispersion effect, two pulse shaping techniques are adopted to improve the incident wave shape. The two techniques include changing the striker (length, shape) and copper pulse shapers (diameter, thickness, shape). Experimental results show that the pulse shaping effect with the small diameter of copper shaper is better than that of the tapered striker and annular pulse shaper, all of which could reach dynamic stress equilibrium, and reduce the high-frequency oscillation, and achieve constant strain-rate deformation approximately.

The drinking of coffee forms a deep-rooted pastime in many communities worldwide. However, the culture of coffee drinking generates vast quantities of organic waste that ends up in landfills. Current research trends are inclined towards recycling of waste materials into alternative construction materials, hence the need to research sustainable uses for spent coffee grounds. Coffee grounds (CG) are highly organic with a very high percentage of biodegradable material. The objective of this research was to study the strength development of CG when used as a geopolymer stabilized embankment structural fill material aiming for a better understanding of geopolymer stabilization of highly organic material. Fly ash (FA), being a silica and alumina rich material, was used as a precursor. A liquid alkaline activator, L, being a sodium hydroxide-sodium silicate solution was used for alkali activation of FA in the CG-FA geopolymer. Factors found to affect strength development of the CG-FA geopolymer were: (1) the ratio of sodium hydroxide and sodium silicate in the activator liquid; (2) the curing time; (3) the replacement ratio of FA in the CG; (4) the alkalinity of the activator liquid used; and (5) the curing temperature. Optimally, FA can constitute up to 30% of the CG-FA mix for efficient geopolymerization to occur. The concentration of sodium hydroxide can be increased up to 12 mol before the strength development-to-alkalinity ratio decreases. The highest strength was found to occur when the curing temperature was 50°C. By introducing 30% of FA into CG, an efficient geopolymer can be synthesized with a $\mathrm{L}/\mathrm{FA}$ ratio of 1.8 and a ${\mathrm{Na}}_2{\mathrm{SiO}}_3:\mathrm{NaOH}$ ratio of $50:50$, which provides the maximum 7-day strength. California Bearing Ratio tests conducted on the CG-FA geopolymer, confirm that it is possible to use geopolymer stabilized CG as an embankment structural fill or subgrade material. Geopolymerization products will further encapsulate and bind the organics in CG, eliminating their potential to biodegrade, which attest to the efficacy of geopolymers as an alternative stabilization agent for highly organic soils.

Magnetorheological (MR) fluid is a kind of typical smart material whose stability, viscosity, and shear yield stress are three important performance indexes. In this study, in order to acquire high performance MR fluid, two kinds of coated magnetic particles, multiwalled carbon nanotubes– (MWCNTs-) coated magnetic particles and surfactant-modified magnetic particles, are prepared and their performances, such as density and magnetic properties, are investigated. A group of MR fluids based on mixing coated magnetic particles with different mixing ratios of coated magnetic particles, different volume fractions, and different dosages of thixotropic agent are experimented considering their sedimentation stability, rheological properties, and shear yield stress. The results show that the coated magnetic particles have a lower density and relatively high saturation magnetization, which will benefit the antisettlement behavior of MR fluids; and the mixing ratio of coated magnetic particles, volume fractions, and dosage of thixotropic agent all have effects on the properties of MR fluids. At the same time, an initial tilt chain model of MR fluids based on mixing coated magnetic particles is proposed to describe the properties of MR fluids at the microlevel, and the numerical values of the shear yield stress fit well with the experimental values.

Ordinary portland cement (OPC) has been extensively used in cold recycling asphalt and cold-mix asphalt as an additive in order to improve the early age performances of these mixtures. The main purpose of its application is that cement hydration benefits the strength development by consuming water and by accelerating the bitumen emulsion breaking. The aim of this study is to investigate the influence of cement on the rheology and stability of rosin-emulsified anionic bitumen emulsions. With this purpose, an anionic bitumen emulsion blended with various amounts of cement and limestone filler was studied by means of a Brookfield viscometer. Optical microscopy was used to investigate the breaking process of the bitumen emulsion and the morphology of bitumen droplets in the presence of cement and filler. In addition, the stability of anionic bitumen emulsions was studied in dependence of the pH and the calcium ion concentration. The results indicate that, unlike limestone filler, which has no significant influence on anionic bitumen emulsion, cement reacts with rosin emulsifiers and causes flocculation and partial coalescence of bitumen emulsions. This gelation of cement-bitumen emulsion blends appears to be caused by the interaction between cement grains and emulsifiers. While a decrease of the pH would lower the solubility of the emulsifiers, this is not a concern since cement dissolution increases the pH.

Foam concrete incorporated with nitrogen-doped ${\mathrm{TiO}}_2$ ($\mathrm{N}\text{-}{\mathrm{TiO}}_2/\mathrm{FC}$) was fabricated, characterized, and tested for the sorption and degradation of trichlorfon. The removal performance of trichlorfon under visible-light irradiation by using this concrete was compared with that using pure foam concrete (FC) and foam concrete incorporated with ${\mathrm{TiO}}_2$ (${\mathrm{TiO}}_2/\mathrm{FC}$). Factors including the amount of photocatalysts and curing age were investigated. The $\mathrm{N}\text{-}{\mathrm{TiO}}_2/\mathrm{FC}$ exhibited a higher removal efficiency of trichlorfon but a lower sorption than FC and ${\mathrm{TiO}}_2/\mathrm{FC}$. The sorption and photocatalytic activity decreased with curing age and the amount of incorporated nanoparticles. Seventy-five percent of $20\mathrm{mg}/\mathrm{L}$ trichlorfon was absorbed by $\mathrm{N}\text{-}{\mathrm{TiO}}_2/\mathrm{FC}$ (6% incorporation and 1-day curing) in 540 min, and 19% of the sorbed trichlorfon was degraded in 180 min with a compressive strength of 4.9 MPa. The FC could absorb nearly 83% of trichlorfon in 540 min but degrade less than 1% in 180 min. Moreover, 6% $\mathrm{N}\text{-}{\mathrm{TiO}}_2/\mathrm{FC}$ exhibited the best performance (removed almost 100% of trichlorfon in 2 weeks) in pilot-scale experiments, indicating its potential use in nonpoint pollution control.

Stone masonry buildings provide evidence of the cultural and historical values at the time. Therefore, it is important to preserve the stone of these buildings to harmful environment conditions like freeze-thaw and salt crystallization cycles, air pollution, and excessive and frequent rain or snowfall, which can lead to decay processes that endanger the future of architectural heritage. Thus, it is important to understand how environmental actions act on the physical and mechanical properties of building stones. In Portugal, the most used building stone, particularly in the north region, is granite, both in the vernacular and historical buildings. Therefore, this research aims at evaluating the performance of different types of granite, characteristic of the northeastern region of Portugal to the action of freeze-thaw cycles, for which this environmental action is relevant, given the wide temperature range and the possibility of occurrence of negative temperatures. Frost resistance is important for the durability of the building stone since the freezing-thawing cycles of the water inside the stone pores result in the development of internal stresses, which can lead to cracking and progressive desegregation of material. The analysis of the influence of the freeze and thaw environmental action in the granites belonging to Portuguese vernacular buildings was carried out, based on an enlarged experimental program to obtain the physical and mechanical properties of distinct types of granites before and after the freeze and thaw cycles. This paper presents the experimental campaign of freeze-thaw cycles on three types of granites and discusses the main results analyzing the standard damage indexes associated with the weathering process. Additionally, an analysis of the physical and mechanical properties and the variation of the ultrasonic pulse velocity (UPV) are provided. The freeze-thaw tests showed a considerable influence on the physical properties of granites. The UPV, dry mass, and compressive strength decrease as the result of the material breakdown. The porosity of the granite presents values significantly higher after the cycles of freeze-thaw, which also leads to the increased on the absorption by immersion and capillary absorption coefficient.

This paper presents the results of a laboratory investigation on the performances and mixture combination parameters of railway asphalt concrete (RAC) for supporting high-speed railway slab track. To apply the RAC effectively to high-speed railway infrastructures, modified highway asphalt pavement material tests are conducted to verify mixture parameters. A suitable gradation is recommended based on the test results. The air voids of the material RAC-25 used for railway infrastructure should be controlled from 1 to 3%. The results presented in the paper demonstrate that asphalt content can be determined based on modified mixture parameters. To verify the performance and analyze the mechanistic response of RAC infrastructure, full-scale laboratory dynamic models are established under different environmental temperatures and loading levels. Based on model testing, the reinforced RAC foundation with a 12 cm deep graded gravel layer replaced by RAC-25 shows much better performance compared with the traditional design.

This work investigates a novel bitumen modification by use of organic expanded vermiculite (OEVMT) and a nano-zinc oxide (nano-ZnO) compound. The content of OEVMT is 1% by mass of bitumen, while that of nano-ZnO is 1, 2, 3, and 4% by mass of bitumen. The binders were aged according to the thin-film oven test (TFOT), pressure aging vessel (PAV) test, and ultraviolet (UV) radiation, respectively. The effect of the OEVMT and nano-ZnO compound on the physical and rheological properties of bitumen before and after aging was investigated. The results show that the high-temperature stability of bitumen can be enhanced, while the other physical properties of bitumen are slightly influenced with the introduction of OEVMT and the nano-ZnO compound. As a result of TFOT, PAV, and UV aging, OEVMT and nano-ZnO modified bitumens show lower viscosity aging index, softening-point increment, phase angle aging index, and complex modulus aging index, and higher retained penetration in comparison with base bitumen, indicating their good thermal-oxidation and UV-aging resistance. However, this improvement depends on the OEVMT and nano-ZnO content. The recommended content is 1% OEVMT plus 3% nano-ZnO by combining the physical and rheological properties results before and after three aging methods. Such a result suggests that the OEVMT and nano-ZnO compound can be effectively used as modifiers to improve both the thermal-oxidation and UV-aging resistance of bitumen, which will remarkably extend the service time of asphalt pavement.

Fibers have been used to improve the mechanical and physical properties of cement-based material since the late 1960s. The inclusion of high-dosage and high-aspect ratio microfibers, however, introduces new interfaces between the fiber phase and the matrix phase that may alter the transport properties of fiber cement composites. This paper reports the effects of microbial carbonate precipitation (MCP) on the transport properties of fiber cement composites (FCCs). The results show that the transport properties of untreated FCC increase with fiber dosage as well as fiber aspect ratio due to higher porosity and better pore connectivity. MCP treatment greatly reduced the transport properties of FCC. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) analyses confirm the precipitates were in the form of rhombohedral calcite, which suggests slower MCP due to the growing environment and culturing condition used in this study.

The properties of asphalt concrete are the result of many interdependent physical and chemical mechanisms occurring across multiple length scales. Admixtures such as hydrated lime (HL) and portland cement (PC) are known to affect the behaviors of asphalt concrete at the macroscale, but their contribution at other scales and influences on overall performance of the material are not well understood. This paper presents the findings of a study that evaluates the potential for HL and PC for mitigating the effects of asphalt concrete aging with respect to modulus and fatigue resistance. The properties of interest were evaluated at multiple scales, which involved binder, mastic, and mixture testing. Rheological analyses of aged and non-aged control, HL modified, and PC modified mastics indicate that HL possesses greater potential to mitigate aging than PC. In mixture testing, the modulus results showed trends similar to that of mastics, in which the HL-modified samples were the stiffest and showed greater potential to mitigate aging. As expected, the relative increase in stiffness and relative potential to mitigate aging, averaged across temperatures, was found to be higher in mastics than the mixtures. The results from the uniaxial fatigue test show that HL mixtures possess higher fatigue resistance when aged, thus less negative effects from the oxidation process. Magnification of aging mitigation potential at the mastic scale, and its direct correlation to fatigue behavior, explains why multiple scale evaluations can be useful in evaluating the true benefits of the admixtures.

This paper investigates the resilient moduli of reclaimed asphalt pavement (RAP) and virgin aggregate blends obtained from the subbase of a segment of Route 165 in Rhode Island, U.S. The materials included RAP and virgin aggregates that were blended off-site using cold recycled RAP, as well as RAP blends that were generated in situ from full-depth reclamation (FDR). Cyclic triaxial tests were performed on compacted specimens of the RAP blends to assess their resilient modulus ($M_R$) behavior. Selected FDR RAP blends were mixed with various stabilizer treatments including liquid calcium chloride, asphalt emulsion, or portland cement. A three-parameter material model was fit to the laboratory test data and used to interpret the $M_R$ behavior. The $M_R$ values of the untreated cold recycled RAP blends and the untreated FDR RAP blends ranged from 120 to 502 MPa and 171 to 578 MPa, respectively. The $M_R$ values of the calcium chloride-treated and asphalt emulsion-treated FDR RAP blends were within the range of the untreated FDR RAP blends, but permanent strains were higher. The $M_R$ values of the portland cement-treated FDR RAP blends were significantly higher than the untreated FDR RAP blends and had lower permanent strains.

The use of cement as an additive to natural soil has been practiced for a long time in engineering projects. Chemical bonds generated as the result of cement hydration and pozzolanic reactions have been responsible for the increase in strength of cemented soils. The purpose of this research is to evaluate the effect of cement on residual strength of overconsolidated soil. Drained shear strength of overconsolidated compacted soil and soil-cement specimens consisted of 50% bentonite, 50% Aeolian sand with 3% by dry weight cement in as compacted (unsheared or intact); precut (residual) conditions were measured in a direct shear device after varying curing time. The cementation that occurred because of the addition of cement and the increase of curing time caused a remarkable increase of mobilized drained shear strength in both intact and residual conditions. A remarkable increase in cohesion intercepts $c^{\prime }$, a negligible decrease in ${\varphi }_{(oc)}^{\prime }$ in intact condition, a negligible cohesion and noticeable increase in ${\varphi }_r^{\prime }$, and a decrease in drained shear strength parameters $m$ and $m_r$ occurred as a result of cement addition and increased curing time.

Recently, ultra-high performance concrete (UHPC) has been utilized in highway bridge connections, where its superior strength and durability help to reduce joint cracking and enhance transverse load transfer. According to the load and resistance factor design (LRFD) bridge design procedure specified by AASHTO, the strength of the connections is dependent on the adhesion and friction between the connected materials. The objective of the present research is to identify the adhesion value between UHPC and high-strength concrete (HSC) with varying degrees of roughness. To this end, UHPC-HSC specimens were tested in direct tension according to ASTM protocols, and the maximum tensile stress at failure was obtained. Test results show that the average maximum tensile stress for the UHPC-HSC specimens with a smooth interface exceeds that determined from past research for any degree of roughness. Furthermore, the average maximum tensile stress increases with the degree of roughness. The results from the direct tension tests, along with those from slant-shear tests performed on similar materials in a previous study, were then used to back-calculate the friction coefficients using Mohr-Coulomb theory.

In glued-laminated timber (glulam), fracture may occur at the interface of two adjacent laminae that mostly have different growth ring orientations. The double cantilever beam (DCB) tests for Mode I fractures and three-point bending end-notched flexure (3ENF) tests for Mode II fractures were performed to obtain the interlaminar fracture toughness of glulam with focus on the influence of growth ring orientations. Experimental and numerical results show that the effect of growth ring orientations of two adjacent laminae on Mode I and Mode II interlaminar fracture toughness is slight.

This paper focuses on the influence of exposure temperature (21, 30 and 50°C) on chloride diffusion into reinforced concrete (RC) pipe pile exposed to atmospheric corrosion. The governing equation of chloride diffusion into RC pipe pile is described and solved analytically by using the Bessel functions. The salt spray tests are set up to simulate the environment of atmospheric corrosion. RC pipe piles with three different water-to-cement ($w/c$) ratios (0.30, 0.45, and 0.55) are exposed to 5% chloride salt spray for 32 days at the three levels of exposure temperatures. The chloride concentration profiles, surface chloride concentration, apparent and effective diffusion coefficients, activation energy, and binding capacity values of RC pipe piles with different $w/c$ ratios at different exposure temperatures are presented. The results of the present study indicate that an increase in exposure temperature results in higher free chloride concentration. The surface chloride concentration and apparent and effective diffusion coefficients increase with the increase in temperature for a certain relative humidity. The binding capacity increases significantly with the increase of exposure temperature from 21 to 30°C; however, the binding capacity decreases slightly with the increase of exposure temperature from 30 to 50°C. The log-variation of apparent diffusion coefficient with the inverse of absolute temperature is linearly distributed. Therefore, it could be concluded that the chloride diffusion into RC pipe pile follows the Arrhenius theory.

Loess, which primarily consists of wind-transported silt and clay particles, is widely distributed around the world, including the central Asia, central Europe, the northwestern and central United States, Alaska, and South America. The metastable structure of natural loess has resulted in construction delays and catastrophic failures. To explore the potential applications of soil improvement with green materials, this paper presents an experimental study of applying fly ash–based geopolymers for the loess stabilization. Two different precursors are employed to the investigation. It is found that potassium hydroxide renders a higher unconfined compressive strength than sodium hydroxide to the samples when the same fly ash/loess ratio is applied. This agrees with the results of the mechanical properties of the two different geopolymers. With an increasing fly ash/loess ratio, the compressive strength and Young’s modulus increase. The microstructural characterization unveils that a compact and stable microstructure has been developed in the stabilized loess. With the aid of energy dispersive X-ray spectroscopy and X-ray diffraction, it is observed that it is the binding effect of geopolymer gel that contributes to the improvements in the mechanical properties of stabilized loess samples.

This paper investigates the statistical characteristics of ethylene tetrafluoroethylene (ETFE) foils’ uniaxial and biaxial mechanical properties and suggests optimal partial safety factors of this material. Ten groups of uniaxial tensile tests and nine groups of biaxial tensile tests were performed. The test results indicated that two yield points of ETFE foils were more stable than the ultimate yield point, and then these two yield points were recommended as the reference points for single-layer pretensioned and cushion foil types. Moreover, a probabilistic limit state design method was adopted to calculate partial safety factors of ETFE foils. The statistical characteristics of an ETFE foil’s resistance and the partial safety factors of this material under three load effect combinations were determined. Reliability indexes were finally checked on the basis of the central point method and the Rackwitz–Fiessler method, whose results showed that the suggested partial safety factors could satisfy the target reliability index. These data offer a deeper understanding of ETFE foil mechanical properties and could be conveniently adopted in ETFE structural design.

The low-cycle fatigue (LCF) behavior of steel in energy-dissipating seismic connections is an important consideration, especially in light of the interest in performance-based seismic design. In this study, the LCF performance of seven steel bar types (AISI 8620, 1018, 1045, 1117, 1215, 4140 and ASTM A36 steel) was experimentally examined and compared. The bar specimens were subjected to sinusoidal strains of constant amplitude from zero to peak strains of 4%, 6%, or 8%. Equations that relate the applied strain amplitudes with the number of cycles to failure were developed and compared. In addition, relationships for calculating the total dissipated energy corresponding to the applied strain amplitude were proposed based on the experimental results. This study demonstrated that, in general, the LCF resistance of AISI 1045 steel type outperformed the other steel materials at a strain amplitude of $\pm 2\%$. However, at $\pm 3$ and $\pm 4\%$ strain amplitudes, the LCF lives of ASTM A36 and AISI 1117 bars outperformed all others, respectively. The results also showed that steel types of similar strength could have varying LCF resistance. The impact of chemistry on the LCF life at different strain amplitudes was assessed by correlating the contents of various elements with the LCF resistance data. The results indicated that the sum of Si, Cr, and Mn contents had the highest negative correlation with LCF life. The selection of steel types used in seismic detailing in buildings should consider LCF performance, particularly in designated yielding elements within seismic connections (such as in precast hybrid frames), which rely on repetitive yielding of bars for energy dissipation.

Asphalt concrete is a complex mixture, the behavior of which is dependent on its components while showing different nonlinear behaviors under various conditions. Application of rest time between compressive loading cycles causes hardening-relaxation (H-R) behavior in the sample and increases the deformation potential of the sample. This process might induce changes in the microstructure and the pattern of the placement and rotation of the aggregates. These changes cause a relaxation in the hardening of the material, pose a higher potential of reception of viscoplastic strain in the following cycles, and increase the rate of accumulation of the permanent deformation in contrast with creep loading. On the other hand, corresponding to the inherent properties of bitumen, it causes improvement (healing) in material properties which ultimately will increase the fatigue life. Thus, the aim of this study is to investigate the deformation of asphalt concrete material under compressive loading along with different rest times, by considering both H-R and healing (h) behaviors. In this experimental study, the behavior of hot mixed asphalt (HMA) under different loading conditions is investigated (at 25°C temperature). This study shows that application of longer rest times reduces the effect of H-R behavior and increases the potential of healing, thereby reducing the amount of deformation in the samples, while with shorter rest times the effect of H-R is more prominent and HMA samples experience more permanent deformation.