Journal of Materials in Civil Engineering

Recycled aggregate concrete is an eco-friendly material that is increasingly being used in new constructions. Nowadays, this application is mainly limited by user’s lack of confidence, as coarse recycled aggregate (CRA) is usually more porous, i.e., it has a higher water absorption, than coarse natural aggregate. This difference is a primary concern for practitioners when they have to comply with durability requirements. Although some uncertainties remain in this regard, significant progress has been made in the last few years concerning the assessment of durable recycled aggregate concrete. This paper reviews this topic and includes aspects related to chloride penetration, sulfate attack, freezing and thawing, high temperature, and alkali-silica reaction. Generally, although there are some particularities related to each type of attack, the high porosity of CRA is compensated by other features, such as different texture, increased mechanical compatibility with the matrix, or content of hydration products. Experimental results in the literature show that there are no reasons to consider that durable, sustainable structures cannot be built with recycled aggregate concrete.

In this paper, an experimental investigation was conducted to study the postannealing behavior of Iranian structural steel. Accordingly, 14 heating regimes were programmed to investigate the influence of peak temperature on the mechanical behavior of Iranian steel during the annealing process. Dumbbell specimens were cut out from a hot-rolled carbon steel profile section. Tensile test results showed that the section components (i.e., the flange and web) were affected in almost a similar way, however, the values of the affected mechanical properties were different. Also, the experiments revealed that the peak temperature experienced by the material has a considerable influence on the postannealing mechanical behavior. Below 600°C, there was seen a negligible decrease in yield and ultimate strength so that the material could regain almost all its nominal strength. The maximum ductility took place at 1,000°C, and the elongation ratios of the specimens were 1.26 and 1.37 times greater than the unheated specimens for the flange and web, respectively.

Granulated blast-furnace slag (GBFS) is one of the by-products generated during the process of the extraction of iron from iron ore. In order to use this by-product in a more sustainable manner, in-depth knowledge of engineering and environmental properties of GBFS is required. Consequently, an extensive suite of environmental and geotechnical tests was undertaken to thoroughly assess the feasibility of using this iron and steelmaking by-product as a road construction material. From an environmental perspective, there are no environmental risks regarding the use of GBFS, nor is there any leaching issue with it being used as an aggregate in construction applications. GBFS, with its high friction angle, free-draining nature, acceptable resilient modulus, and suitable CBR value, was found to be an ideal material for usage in nonstructural fill applications. The usage of GBFS as a nonstructural fill material would bring about a more practical end-of-life alternative for this by-product and will, furthermore, allow this material to be reused in a more sustainable way without further processing.

Investigation of the mechanical properties of steel rods at elevated temperatures is important for the fire-resistant design and fire simulation analysis of steel rod structures. In China, GLG650 denotes a steel rod whose yield strength is not less than 650 MPa. A 35CrMo-GLG650 steel rod is manufactured with 35CrMo alloy structural steel using quenching and tempering methods. To investigate the mechanical properties of 35CrMo-GLG650 steel rods at elevated temperatures, tensile tests of four specimens are performed at 100°C, 200°C, 300°C, 400°C, 500°C, 600°C, and 30°C. The test results show that the 35CrMo-GLG650 steel rods at 30°C and elevated temperatures exhibit typical nonlinear characteristics with no obvious yield plateau. The mechanical properties of the 35CrMo-GLG650 steel rods at elevated temperature are obtained, and they are compared with those of other high-strength steels. When the temperature is below 300°C, the reductions in the mechanical properties of the specimens are approximately 0.9. However, the mechanical properties of the specimens change significantly when the temperature exceeds 300°C. At 600°C, the reduction factors of the yield strength, ultimate strength, and elastic modulus are 0.56, 0.46, and 0.45, respectively. In this paper, equations for the nominal yield strength, elastic modulus, and ultimate strength of 35CrMo-GLG650 steel rods at elevated temperatures are proposed. Furthermore, a modified two-stage Ramberg–Osgood model for 35CrMo-GLG650 steel rods at ambient and elevated temperatures is proposed that can act as a reference for the steel rod structure at elevated temperatures.

Acrylic emulsion polymer–modified mortar (AEPM) is widely used for repairing and maintaining the surface of existing concrete structures. In this study, the durability of AEPM was improved by using slag and fly ash. Experimental investigations, including the underwater steel ball test, rapid chloride migration test, and accelerated carbonation test, were employed to characterize the effects of slag and fly ash on the abrasion resistance, chloride penetration resistance, and carbonation resistance of AEPM, respectively. The results showed that there was a strong relation between the use of slag and fly ash and the abrasion resistance, chloride penetration resistance, and carbonation resistance of APEM: (1) the abrasion resistance of APEM first increased and then decreased with the increase of slag and fly ash; (2) the chloride-penetration resistance of APEM increased linearly with the increase of slag, but first increased and then decreased with the increase of fly ash; and (3) the carbonation resistance of APEM decreased slightly with the increase of slag and fly ash. The proper quantity of slag could significantly improve the durability of AEPM, and a suitable content of slag is 6%–12%. A prediction equation of the abrasive strength of AEPM with slag and fly ash is proposed.

This article shows through the analysis of three independent tests that the presented new semidiscrete analytical (SDA) beam model is efficiently applicable in the evaluation of test results. The model is based on fracture mechanics, takes the real distribution of the macrofibers into consideration in the critical cross-section of the beam, and uses a precise approximation of the pull-out behavior of the fibers. The SDA model is applicable to evaluate synthetic and also steel fiber reinforced concrete beams. Furthermore, it is shown that the new method can predict the changes of the residual loadbearing capacity caused by the different length, diameter, tensile strength, maximal friction stress, or other features of the fiber with the use of only one series of experiments with given fiber parameters (e.g., tests with only one fiber length and diameter). Thus, the application of the SDA model can decrease the cost and time of testing new types of fibers because the required number of samples and, therefore, the total time of the lab tests can be radically decreased.

One of the most widely used polymer-based modifiers in asphalt binders is styrene–butadiene–styrene (SBS), which results in binders of increased modulus, strength, toughness, and resistance to permanent deformation. These properties are further improved with the increase of SBS polymer content in asphalt binders, producing binders such as high-content polymer-modified asphalt (HCPMA). Although the HCPMA binders commonly are used in porous asphalt pavements, limited research has been conducted on their aging performance. This paper used gel permeation chromatography (GPC), Fourier transform infrared (FTIR) spectroscopy, and the dynamic shear rheometer (DSR) to explore the evolution of chemical and rheological properties of aging HCPMA binders. The study found that the aging of HCPMA is a combination of oxidation of the base asphalt binder and degradation of the SBS polymer, leading to modulus increase and phase angle decrease. The degradation of SBS happened mostly at the beginning and slowed after pressure-aging vessel (PAV) conditioning for 20 h, which resulted in the lowest rutting resistance of HCPMA binders. When SBS content was higher than 7.5%, more than half the SBS polymer remained after 80 h of PAV conditioning. Although the molecular weight of SBS decreased from 230,000 to 70,000 due to degradation, its modification effect was still significant. Moreover, high modification of SBS can retard the oxidation and hardening of base asphalt binder, especially after PAV conditioning for 20 h. Principal component analysis showed that 10 parameters used in this study could be explained by SBS content and asphalt binder aging extent. Based on PCA results, the complex modulus ($G^{*}$) and phase angle ($\delta$) of HCPMA binders can be well fitted by the exponential function of SBS content and aging index.

The stability and dispersion of aerogel in concrete is the key to evaluation of the thermal insulation performance of the aerogel/concrete system. This study focuses on the structural stability of aerogel under the effect of factors such as hydrophilic concrete system, mechanical mixing, and interaction between aerogel and the concrete matrix. Stable aerogel/concrete materials were prepared by regulating and controlling kinetic parameters of the surface of halloysite (HNT) aerogels. Characterizations of the samples were investigated using techniques such as Fourier-transform infrared spectrometer, thermogravimetric analysis, ${\mathrm{N}}_2$ adsorption-desorption isotherms, scanning electron microscope, and thermal constant analyzer. The results indicated that the surfactant successfully attaches to the surface of the HNT aerogels. Aerogel particles are stable in concrete and kept their original shape. The thermal conductivity of concrete becomes lower as the content of HNT aerogels increases.

This study aims to evaluate the durability and long-term performance of clayey soil treated with sludge ash of a wood and paper (SAWP) mill in response to wetting and drying (w-d) cycles to elucidate its efficiency as a sustainable construction material in earthwork applications. For this purpose, height change measurements, P-wave velocity (Vp), and unconfined compressive strength (UCS) tests were carried out at different w-d cycles. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were conducted to identify the mineralogical and microstructural changes in treated samples. The height change and Vp of the SAWP-treated samples were measured at each cycle and continued for 12 w-d cycles, or until the cycles ended were possible. The UCS tests were carried out after 0, 1, 3, 5, 7, and 12 w-d cycles. The height change ratio increased with the increased w-d cycles. Experimental results revealed that the Vp and UCS results generally decreased by increasing the number of w-d cycles. Crack propagation caused by desiccation kinetics and degradation of the cemented structure led to the formation of a weak plane and a significant reduction in Vp and UCS. Unique relationships were developed between Vp, UCS, and the number of w-d cycles for different SAWP contents and curing periods. These relationships can be considered as estimating the UCS based on Vp values with good accuracy to achieve sustainable design requirements. The XRD analyses demonstrated that calcite (CaCO3) was the main cementitious compound which is a key factor for the strength enhancement.

Permeable pavements are widely recognized as an effective way to improve the environmental and ecological aspects of conventional dense pavements. Based on traditional pavement materials, permeable pavements are often designed to be partially permeable or to consist of merely permeable surfaces. Recently, the development of novel polyurethane-bound pervious mixtures (PUPM) has made the widespread application of fully permeable pavement (FPP) structures possible, which will increase the environmental benefits of permeable pavements. In this case, the saturation of a pavement has a major influence on the performance of FPP. The generation and dissipation of pore pressure is recognized as a critical factor, influencing the bearing capacity of permeable pavement structures. In literature, only few studies focus on the pore pressure in permeable pavements under traffic loading. This study aims to measure and characterize the changes in pore pressure in a full-scale permeable pavement under various saturation conditions under traffic loading. To achieve this objective, pore pressure data was collected from laboratory testing as well as from a full-scale test track constructed with a polyurethane-bounded pervious mixture (PUPM) wearing course. Based on this study, it is found that when permeable pavement material is subjected to cyclic loading, the pore water pressure is much larger than the pore air pressure; in fact, the latter is found to be negligible. During the irrigation process and dynamic vehicle loading, the pore water pressure increases as the saturation increases. The changes of pore water pressure are not obvious in the PUPM surface layer when comparing the results to the pervious layers below the wearing course. Under cyclic vehicle loading, the accumulated pore water pressure of each layer increases with the number of loading cycles and also increases as the saturation increases. These findings support the quest for an in-depth understanding of the stress state and the degradation mechanisms in FPP. The results provide practical conclusions and recommend optimized design properties for a wide application of FPP.

With perspective to the precast industry, this paper is a study of superfine (SF) ground granulated blast-furnace slag (GGBS) as replacement (0%, 30%, 50%, and 70%) of rapid-hardening cement (CEM 1 42.5R) under two types of activation, namely discrete temperature activation (20°C–35°C for 16 h) and two accelerating admixtures. The thermal activation is found to provide the larger improvements in early-age strength as against use of the admixtures; however, the combined effect achieves measurably better performance at early age. Also, the novel admixture, designed to activate SFGGBS, is found to deliver definitive strength enhancement at both (low and moderate) temperature conditions during early ages. Further, the 28-day strength of mortars remains unaffected and is marginally improved under the combined effect of SFGGBS, the novel admixture, and temperature activation.

During asphalt mixture production, the bulk specific gravity ($G_{sb}$) of the mixture aggregate is not routinely measured to determine voids in the mineral aggregate (VMA), because this requires multiple tests and extended testing time. Instead, state agencies have used several alternatives to determine the VMA of plant-produced asphalt mixtures. This study determined the effect of these methods on the VMA determination during production. Materials, including virgin aggregates, reclaimed asphalt pavement (RAP), and plant-produced mixtures were sampled from 10 projects in Florida. Four methods were employed to determine $G_{sb}$ of RAP aggregates, and six methods were used to calculate VMA of plant-produced mixtures. The study results indicated that $G_{sb}$ of ignition-extracted RAP aggregate and the total aggregate blend can be used to calculate the VMA of the mixes during mix design and production if they have been adjusted to account for the effect of the ignition method on the aggregate material.

With the help of ABAQUS, the acceleration responses of asphalt pavement with and without crack damage were simulated, and the change rate of vertical acceleration peak was proposed to characterize the effects caused by crack damage. The simulated results suggest that when there has been crack damage in road structure, the numerical values of the change rates of vertical acceleration peaks are positive at most depths in asphalt pavement, and the maximum change rates tend to appear near the crack tip, which indicates that the acceleration response of the entire road structure is improved due to crack damage and the vertical acceleration near the crack tip has the most growth. The deeper and longer cracks have greater influences on acceleration signals, and the effects of crack length on the acceleration response of asphalt pavement are larger than the effects of the crack position. The crack propagation will produce significant change rates of vertical acceleration peaks, which proves the potential of using acceleration signals to monitor the extension of cracks in asphalt pavement.

Polyurethane-bound porous mixture (PPM) is a new type of pavement material that has shown some potential for overcoming common asphalt mixtures mechanical failures. However, little research has been done on its skid resistance performance. This work presents a comparative study of the skid resistance development between PPM and asphalt mixtures at their early stage. In this study, the three mixtures were bonded by three type binders. The three type binders were polyurethane, 70# virgin bitumen, and styrene–butadiene–styrene (SBS) modified asphalt. In order to distinguished the three type mixtures, we named them PPM, BAM, and SAM respectively. A Taber abraser was used to test the polishing property of binders. A third-scale model mobile loading simulator (MMLS3) was used to simulate the traffic loadings on mixtures, and a British pendulum tester was used to measure the skid resistance of the three types of mixtures in the loading process. The binder polishing test results show a good linear relationship between the binder’s mass loss and the polishing cycle. The slope of the fitting line of the two parameters was defined as binder coefficient (BC) to characterize the polishing property of the binder. The mixture test results show that the skid resistance development trend of three mixtures is similar, as it first increases, then decreases, then finally flattens. However, the British pendulum number peak value and stable value of PPM are lower than that of SAM. The order of the number of loading times of peak (NLTP) of the three mixtures is $\mathrm{SAM}>\mathrm{PPM}>\mathrm{BAM}$. Another good linear relationship is found between BC and NLTP, and the $R^2$ of the fitting model is 0.85, which indicates that the polishing property of binder is effective for predicting the moment of occurrence of the mixture skid resistance peak.

Shear properties of the cross layer in cross laminated timber (CLT) panels are critical for design purposes, especially for applications with high concentrated loads and low span-to-depth ratios. Understanding how the shear properties of CLT lamstock vary with respect to fiber orientation—from perpendicular-to-grain (90°) to parallel-to-grain (0°)—can lead to new and innovative panel layups with superior shear performance. In this study, two-plate shear specimens (per the relevant standard) were fabricated with fiber orientations of 0°, 30°, 45°,60°, and 90° with respect to the shear load direction using eastern hemlock $2\times 4$ lumber. Both shear modulus and shear strength were measured as a function of fiber orientation. The influence of fiber orientation and the interaction of resisting components on the shear properties are discussed concerning observations of the types of failure modes. The results indicate that the effective shear stiffness ($G{A}_{eff}$) and the characteristic shear strength ($F_v$) for a traditional (90°) CLT panel made from eastern hemlock would satisfy grade E3 CLT per the relevant standard. Moreover, the shear strength of the angled cross layers with 30° and 45° fiber orientation with respect to the major panel axis would be 98% and 59% higher, respectively, than CLT with a 90° cross layer orientation.

The effect of methylcellulose, an organic admixture, on the mechanical properties and vibration characteristics of newly developed geopolymer paste (GP) and hybrid fiber-reinforced geopolymer (FRG) composite is investigated in this study. Fly ash and slag are applied to manufacture both the GP and FRG. Short fibers, including 1% copper-coated micro steel fiber, 1% high-strength polyethylene fibers in volume fraction, and 0.4%, 0.8%, and 1.2% methylcellulose in weight fraction, are added to reinforce the geopolymer matrix to develop a new FRG. The addition of methylcellulose can increase the compressive strength and flexural strength of GP and FRG and the load-carrying capacity and toughness with the deflection hardening for FRG, while slightly decreasing the static modulus of elasticity (SMOE) of GP and FRG. The increase in the toughness of FRG can reach 80% by adding 0.8% methylcellulose. In addition, the dynamic modulus of elasticity (DMOE) and the damping ratio of GP and FRG are investigated by conducting hammer impact forced vibration test. The results demonstrate that the addition of methylcellulose to GP and FRG significantly increases the damping ratio by up to 15% and 25%, respectively, while slightly decreasing the DMOE of both GP and FRG.

The study investigated the bond behavior of reinforcing bar and geopolymer concrete as a function of rebar diameter, embedment length, concrete cover and compressive strength. The effect of rebar surface (plain and ribbed) and coating on bond performance of geopolymer concrete also was studied. The pull-out behavior under monotonic loading, ultimate bond stress, slip, and load at failure were evaluated. Embedment length to bar diameter ($L/\varphi$) ratio was optimized and found to be 5. The $L/\varphi$ ratio of 5 was used to study the pull-out behavior. The specimens were reinforced with helixes to avoid splitting of concrete before attaining the ultimate strength. The ultimate bond stress of ribbed bars was 234% higher than that of plain bars. The rebars were coated with fusion-bonded epoxy and zinc alum spray coating to study the effect of coating on bond behavior. The coated bars slipped more than uncoated bars due to the reduction in the coefficient of friction. The bond performance of geopolymer concrete was effective compared with that of the control cement concrete. The bond strength of geopolymer concrete exposed to elevated temperatures increased with an increase of temperature up to 400°C and then decreased. The decrease in bond strength was about 69% at 800°C. The accelerated corrosion test was carried out using the impressed voltage method at 65 V in 5% saturated sodium chloride (NaCl) solution. It was observed that increasing corrosion levels from 0.2%–0.69% decreased the ultimate bond strength from 16 to 9.5 MPa.

This article presents a study evaluating the adhesion properties between asphalt and calcined bauxite. Limestone and granite were also compared with calcined bauxite. For this purpose, asphalt bond strength, surface free energy, and phase angle of asphalt and aggregate were tested. The chemical reaction and mechanical adhesion of asphalt–aggregate were also investigated using Fourier transform infrared spectroscopy (FTIR) and a surface roughness test. The results showed that the higher the alumina content of the calcined bauxite, the greater the adhesion. The adhesion properties of asphalt and aggregate were ranked as follows: limestone > calcined bauxite > granite. Based on the results of the gray correlation analysis, it can be concluded that the intermolecular interactions between asphalt and aggregate play a major role in adhesion. The interlocking caused by surface texture also affects adhesion to some extent. The larger work of adhesion and the more complex surface texture of calcined bauxite with higher alumina content are the main reasons for its higher adhesion. Calcined bauxite with low alumina content should be treated to enhance adhesion before it is used in asphalt mixtures for wearing courses.

Ballasted track progressively deteriorates due to ballast degradation and track deformation under dynamic loading, and this process accelerates when train speeds increase and axle loads become heavier as the railways are seeking to serve the enhanced productivity of the mining and agriculture sectors; on this basis, improving track performance is imperative. One effective solution is to incorporate energy-absorbing materials in the rail track, particularly when these materials are recycled from mining waste and recycled rubber. In this paper the performance of the track specimen with a synthetic energy absorbing layer (SEAL) (i.e., a matrix of recycled rubber crumbs with mining waste) is investigated by a series of large-scale (prototype) cubical triaxial tests. The test results indicate that the inclusion of rubber inside the SEAL matrix has a significant influence on the lateral movement, vertical deformation, ballast degradation, and energy distribution of the track specimen. To facilitate a better understanding of the energy-absorbing mechanism with the addition of rubber, an energy-based analysis has been adopted to identify the critical amount of rubber crumbs needed to efficiently distribute the accumulated energy, hence improve track performance. It is shown that adding 10% of rubber into the SEAL matrix will provide superior performance with less ballast breakage, less vibration (as reflected by the elastic energy), and comparable settlement compared to traditional track.

This paper presents experimental investigations to compare the effect of three environmental solutions on the degradation of tensile performance of fiber reinforced polymer (FRP) bars. Three kinds of FRP bars, basalt FRP (BFRP), carbon FRP (CFRP), and E-glass FRP (GFRP), were tested in tension after conditioning in tap water, artificial seawater, and alkaline solutions at room temperature for different exposure periods of 0, 45, 90, 135, and 180 days. The test results showed that the changes of the surface appearance of GFRP bars were more obvious that those of BFRP and CFRP bars after 180 days of exposure to three environmental solutions. The tensile failure mode and load-displacement curves of all tested FRP bars exhibited similar characters regardless of the immersion solution, the exposure period, or type of FRP bars. By comparing the residual mechanical properties of three kinds of FRP bars tested in this study, it has been found that the chemical attack of harsh environments simulated by immersion in seawater solution and alkaline solution resulted in a significant damage to BFRP bars. The effect of the seawater solution on the strength loss of CFRP bars was more obvious than those of the other two solutions. While the alkaline solution caused the greatest strength damage on GFRP bars. These findings were in accordance with the properties of material susceptibility to aggressive solutions and the moisture absorption of the matrix. No significant degradation of the elastic modulus of the three kinds of FRP bars had been found after exposure to aggressive solutions because their glass transition temperatures were kept unchanged in the experiment. Finally, based on the Arrhenius theory, the time-dependent tensile strength retention of all tested FRP bars exposed to the three aggressive solutions were fitted with experimental data obtained in this study. They were also compared with various test results collected from previous studies. The comparison results indicated that our experimental data were in good agreement with the predictions and most of the existing results.

The deterioration of conventional cement (CC) and alkali-activated (AA) cementitious materials when exposed to sulphuric acid is influenced by the scale, both in terms of scale of manufacture (paste, mortar, and concrete) and level of observation (microscopic to macroscopic). The degradation of samples at the microscale was examined using scanning electron microscopy, energy dispersive x-ray, x-ray diffraction, Fourier transform infrared spectroscopy, and microcomputed tomography. Macroscopic measurements were used to establish the cross-section change, mass loss, and compressive strength. In addition, the ion change in the reservoir solution was examined using inductively coupled plasma mass spectroscopy. Microscale and macroscale measurements highlight the fundamental difference in the degradation of CC and AA materials, and therefore current simple indicator tests are inadequate for comparing the performance of materials.

This paper investigates the mechanical properties under laboratory and field conditions of a concretelike blend made of fluorogypsum (FG), fly ash, and portland cement for artificial-reef construction, which is referred to as a FG-based blend. The 28-day compressive strength and relative volumetric expansion of the FG-based blend were statistically characterized. After 1 year of immersion in brackish water under field conditions, the compressive strength of the FG-based blend experienced a moderate reduction when compared with material under laboratory conditions but did not degrade below its 28-day value. Visual examination of the immersed specimens indicated that aquatic organisms are attracted to the proposed material. Field investigation of a small artificial-reef structure made of a FG-based blend indicated that sea floor settlement due to the weight of the structure was small. A preliminary cost analysis comparing the cost of artificial reefs constructed with different materials suggests that the proposed FG-based blend is a promising environment-friendly economic material for artificial-reef construction.

Prediction of the mechanical properties of cement-based materials across scales according to micromechanics-based homogenization is affected by many factors, which include the homogenization scheme, the mechanical property, volume fraction, and geometry of each phase, and the interface property between different phases, and so on. In this study, the micro creep properties of cement pastes with $w/c$ ratios of 0.3, 0.4, and 0.5 were homogenized from the calcium silicate hydrate scale. The influences of the homogenization scheme, phase geometry, and interface property were assessed. The homogenized creep results were then compared to the measured ones by the microindentation technique. It was found that the creep property is underestimated significantly under the perfect interface condition, and the poor assessment cannot be improved effectively by using different homogenization schemes or considering different phase geometries. However, the measured creep of cement pastes by microindentation test can be reproduced by considering the proper imperfect interface between different phases. The imperfect interface is modeled as spring layers of vanishing thickness in the tangential directions for simplicity, which is characterized by only one interface parameter. The larger the interface parameter, the more imperfect the interface, and the interface parameter increases with increasing $w/c$ ratio. The findings in this study suggest that the imperfect interface might be a key factor during the creep upscaling of cement pastes from nanoindentation to microindentation scales.

The valorization of residue from industrial processes for their use as components of other materials is seen as a highly effective solution for environmental problems associated with the building industry. The manufacture of bituminous hot mixtures generates a residue, known as recovered filler (RF) that holds a high potential for use as a fine aggregate in the production of concrete. Self-compacting concrete (SCC) needs a large amount of fine aggregate to attain the properties of self-compacting required. This study examines a SCC made with this recovered filler as fine aggregate (SCC-RF). Mechanical properties and delayed strains such as creep and shrinkage among others, not analyzed in previous studies, are determined in order to verify the aptitude of this material as a component of concrete and identify any possible influence of this filler on the behavior of this SCC, given that it was dried in an oven at approximately 150°C. In parallel, a second SCC with commercial filler (CF) was prepared, named SCC-CF, for a comparative analysis of these properties. The results obtained allow us to conclude that, although SCC-RF demands more superplasticizing content to get the self-compactibility requirements, the levels reached by the studied properties are satisfactory, guaranteeing the sound behavior of reinforced concrete (RC) structures built using this concrete.

Climate change is expected to impact both the operational and structural performance of infrastructure such as buildings, roads, and bridges. However, infrastructure design guides widely rely on historical climate data, if any, for informing design requirements. The goal of this research was to explore a methodology for modeling bridge deck design against corrosion attack in a changing climate. Three deterioration stages were simulated to understand the time to deck failure. Corrosion initiation of reinforcing steel was considered by utilizing a deterministic diffusion-based model predicting the time to reinforcement corrosion initiation. Crack initiation and crack growth were also simulated using mechanistic approaches to illustrate the sensitivity of bridge deck deterioration and design service life to changes in bridge deck design and a changing climate across major cities in Canada. The findings indicate that a changing climate has the potential to significantly alter the service life of a bridge deck, but the effect is strongly dependent on the durability design of the bridge deck. It is recommended that bridge designers strive to utilize mechanistic-empirical models that incorporate high-resolution climate data as inputs for better understanding changes in deterioration as a consequence of a nonstationary climate.

Ornamental stones weaken with exposure to weathering. Consequently, anomalies such as disintegration and cracks appear, making degradation studies necessary. Durability studies are necessary to determine the useful life of the material. In this study, gneiss specimens were divided into three lots: the first was a standard specimen, not aged, used as a control; the second was subjected to accelerated degradation in the laboratory; and the third was degraded naturally under local weathering conditions. After the two degradation processes, the weakening of the stone from wear and flexing was evaluated in relation to the control specimen over time, yielding correlation coefficients greater than 0.90. The correlation curve fit indicated that it is possible to evaluate the durability of the materials by determining the susceptibility of the material to alterations. A loss of flexural strength of up to 34% was observed after 5 years of local weathering, and was also simulated in 70 days of accelerated laboratory tests. This decline also was correlated by means of porosimetry of the stone after being subjected to the degradation processes, which exhibited a reduction in rigidity over a short period in the built environment.

In this paper, the effectiveness of different chemical stabilizers in improving the engineering properties of expansive soils is investigated. Three different soils with variable sulfate contents were treated with Type I/II portland cement, lime, Class C fly ash (FA), and Class C FA–cement and Class F FA–cement blends. Specimens were subjected to Atterberg limits (LL/PI), pH, unconfined compressive strength, and volumetric swell tests. Test results indicated that cement was preferable for higher strength at shorter curing times (7 days), while lime produced the maximum strength at longer curing periods (90 days). It was deemed that 10% to 12% calcium oxide (CaO) in stabilizers was optimum for stabilizing expansive soils. In addition, ${\mathrm{CaO}/\mathrm{SiO}}_2$ and $\mathrm{CaO}/({\mathrm{SiO}}_2+{\mathrm{Al}}_2{\mathrm{O}}_3)$ ratios were found to be good indicators of pozzolanic activities at longer curing periods, and higher strengths were obtained when the ratios were between 2 and 2.5. Both cement and lime were prone to sulfate attack, which decreased the strength of soils (31% and 42% decrease, respectively) significantly, whereas strength reductions were lowered by treatments with FA and cement blends. Volumetric swelling of the soils decreased during the stabilization process depending on moisture, density, pH, clay content, curing time, stabilizers’ constituents, and addition rates. Class C FA– and $50/50$ FA–cement blends reduced the volumetric swellings of sulfate-rich expansive soils compared to those stabilized with cement and lime alone.

This paper investigates the possibility of using waste materials such as quarry dust and fly ash in the manufacture of cold-bonded aggregates. The artificial aggregates were prepared by varying the waste quarry dust content between 0% and 75% by weight. Fly ash activated using lime was used as a binder. The comparable strength property was obtained for an aggregate made of 37.5% quarry dust and 62.5% activated fly ash. Hence, the aggregates with this proportion were used to prepare the concrete specimens. The concrete was cast by varying the coarse aggregate replacement ratio of 0%, 25%, 50%, 75%, and 100%. A few specimens were tested without exposure to elevated temperatures, and the remaining specimens were tested after exposure to elevated temperatures. The elevated temperatures of 200°C, 400°C, and 600°C were considered in this study. The strength and durability properties of concrete containing cold-bonded aggregate were investigated. Compressive and tensile strength and modulus of elasticity, mass and strength loss due to acid and sulfate attack, and bulk diffusion tests were carried out. The concrete containing quarry dust–fly-ash (QDFA) aggregate alone exhibited low strength reduction when exposed to elevated temperature. A prediction model for the strength properties of QDFA aggregate concrete was proposed. The study showed that QDFA cold-bonded aggregate is a promising material for green construction.

A new semiempirical creep and shrinkage model is proposed wherein basic creep, drying creep, and drying shrinkage are all considered to age according to solidification theory. Applied to basic creep, this proposed formulation results in a closed-form expression for the compliance function when using two different volume growth functions: one approximating typical strength gain of concrete, and a second matching the slower aging from the B4 model. Drying shrinkage and drying creep, which is treated as a load-induced shrinkage, are combined into total drying strains while still accounting for aging through solidification. The model for drying strains satisfies all asymptotic conditions required by diffusion analysis. Approximations appropriate for design purposes are proposed for the drying strains, and the associated creep and shrinkage strain rates also are provided. The proposed model was compared with measured experimental data and contrasted with the B4 model.

There has been limited research in the past on the effect of varying soil’s acidity measured as pH and saturation measured as moisture content on the fracture toughness of buried cast iron as per comprehensive literature review. This paper presents findings obtained from a long-term test designed to investigate the combined effect of varying levels of soil’s acidity and saturation on the fracture toughness of buried cast iron over time. Relations for the change in candidature fracture toughness of the corroded cast iron over time as a function of soil’s pH, moisture content, and corrosion pit depth are developed. Moreover, a relation correlating the change in microstructure and the fracture toughness of the corroded cast iron is also developed. The significance of the current paper is that it reports that soil’s corrosivity induces a change in the microstructure and composition of cast iron, which consequently affects the fracture toughness of the corroded cast iron.

Several problems exist in the use of cement to treat soft soils, such as high treatment cost, air pollution in the cement production process, possible groundwater contamination by cement in the ground, and so on. In this paper, steel slag powder is used to replace a portion of the cement to form a new curing agent. The soft soil is solidified by the agent and soaked in seawater. In order to simulate the seawater erosion environment, three kinds of ions that greatly influence solidified soil erosion in seawater were selected, and the strength degradation properties of solidified soil caused by a single ion were studied. Through physical and mechanical tests, the fluctuation of unconfined compressive strength (UCS) for each group under different conditions of seawater and distilled water curing conditions was obtained. The microscopic morphology of the solidified soil and the mineralogy difference in accordance with the erosion time were obtained via the X-ray diffraction (XRD) and scanning electron microscopy (SEM) tests.

The degradation mechanism of ethylene–propylene–diene monomer (EPDM), when used as a sealant material for shield tunnels, must be known to assess of the service life of sealant gaskets. This paper presents a series of experimental investigations on the degradation performance of EPDM due to aging under artificial seawater and hot air conditions. The mechanical properties of EPDM (such as hardness, tensile strength, and elongation at break) are investigated first. Then, microchemical analyses, such as scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR), are conducted to investigate the variations in the microstructure during aging. The tensile strength and elongation at break under hot air or artificial seawater conditions at different temperatures decrease with aging time, whereas the hardness of EPDM under hot air or artificial seawater conditions increases with aging time. However, at 25°C, the hardness decreases gradually with aging time under artificial seawater conditions. The microscopic results show that the microstructure changes can be attributed to the fracture degradation of the molecular chains, oxidation reactions, and the formation of $\mathrm{C}═\mathrm{O}/\mathrm{C}─\mathrm{O}─\mathrm{C}$.

This study aims to investigate the shear fatigue performance of asphalt mixture and factors influencing performance using a three-dimensional (3D) discrete element method (DEM) incorporated with the Burgers model. The repeated uniaxial penetration test (RUPT), which is a shear fatigue test method for asphalt mixtures, was succinctly described. A 3D micromechanical model for the prediction of asphalt mixture’s shear fatigue life was built using particle flow code in three dimensions. The influence of aggregate size, temperature, binder content, air void, and loading/penetration frequency on the shear fatigue life were simulated based on this model. Simulation results were validated by performing a laboratory RUPT. Research results revealed that an asphalt mixture’s shear fatigue life could be simulated well using a 3D DEM. Aggregate size, temperature, binder content, air void, and loading frequency considerably affected the asphalt mixture’s shear fatigue life. Shear fatigue life increased with the nominal maximum aggregate size or loading frequency and decreased with the increasing temperature or air void. At 60°C, shear fatigue life was the largest with optimal binder content.

Severe localized corrosion of submerged steel bridge piles in Florida was associated with fouling and microbial-influenced-corrosion (MIC). The research in this study evaluated the efficacy of cathodic protection (CP) in those environments. Field tests were conducted in two natural rivers with different marine fouling morphologies. The test steel arrays were coupled to a zinc-sacrificial anode, and system potentials of approximately $-923\mathrm{mV}$ with respect to the saturated-calomel electrode (SCE) developed. Global CP currents to the steel exceeded $3\mathrm{\mu A}/{\mathrm{cm}}^2$ and generally reduced the overall corrosion rate. The CP current was related to cathode surface availability under fouling, and portions of the array did not receive sufficient cathodic polarization. Laboratory tests were conducted using specimens with different surface crevice morphologies that were cathodically polarized at $-850$ and $-950{\mathrm{mV}}_{\mathrm{SCE}}$ and immersed in solutions inoculated with sulfate-reducing bacteria. Tests confirmed that the presence of crevices reduce CP effectiveness. Fouling environments caused insufficient levels of CP and supported the growth of bacteria associated with MIC. CP alone may not be adequate to mitigate crevice corrosion and MIC under heavy fouling.

Different types of concrete mixtures are used as building materials. The manufacturing process of two-stage concrete (TSC) differs from that of conventional concrete. This study investigated conventional mechanical properties derive empirical relations for estimation of the mechanical parameters of TSC and conventional concrete mixtures. TSC was used to prepare 216 specimens and conventional concrete was used to prepare 108 specimens that then were aged for 28 days. Uniaxial compression, Brazilian tensile strength, and point load tests were carried out as destructive testing. Schmidt hammer and ultrasonic pulse velocity tests were carried out as nondestructive testing. The data from testing were categorized as regression or test data. Empirical relations were derived between the parameters for the two types of concrete, and these relations were validated. It was concluded that indirect, nondestructive testing of engineering materials, including concrete, considerably increases the speed and decreases the estimation cost of determining the mechanical parameters. This method can be recommended for estimation of these mechanical parameters.

Under the comprehensive action of environmental temperature and vehicle loads, asphalt pavement is prone to certain issues, such as high-temperature wheel ruts. Thermally activated shape-memory epoxy (SMEP) resin is a new kind of intelligent polymer material that can sense temperature changes and respond by adjusting the mechanical parameters back to their initial state. Adding thermally activated shape-memory epoxy resin to an asphalt mixture can improve its high-temperature performance and water stability. This paper incorporated shape-memory epoxy resin fibers into asphalt mixtures. First, AC-13 asphalt mixtures mixed with and without SMEP were tested with a Marshall experiment. The results showed that the AC-13 asphalt mixture mixed with SMEP swells. To solve this problem, an interlocking filling–graded composition is proposed. A local optimization algorithm was used to study the graded composition, and the corresponding equations and processes are proposed. The Marshall test of the interlocking filling–graded composition indicated that the values of porosity and voids in mineral aggregate (VMA) of the asphalt mixture produced with 4.75-mm sieve pores were greater than the values obtained for the asphalt mixture produced with 2.36-mm sieve pores. Moreover, the bulk density and stability of the asphalt mixture produced with 4.75-mm sieve pores were less than those obtained for the asphalt mixture produced with 2.36-mm sieve pores. The optimal interlocking filling–graded composition was produced with 2.36-mm sieve pores and a 6% mineral powder. The interlocking filling–graded composition in this paper solves the aforementioned expansion problem when incorporating SMEP into an ordinary graded composition, enriching the graded composition design method of asphalt mixtures.

This research aims to evaluate the performance of flexible base asphalt pavement compared with traditional semirigid base asphalt pavement in practical application in central China under heavy load conditions. Four different flexible base structures were constructed in the field, and the material design and performance test of flexible base asphalt pavement were carried out. The experimental section was built on a highway in Henan Province with semirigid base asphalt pavement in the main-line, and the performance was evaluated by follow-up tracking and observation. Through 10 years (2009–2018) of field performance observations, a total of five indexes of pavement performance [International Roughness Index (IRI), Rutting Depth Index (RDI), Skid Resistance Index (SRI), Pavement Structural Strength Index (PSSI), and Pavement Condition Index (PCI)] were collected. The results show that the IRI was not sensitive to the base structure but the PSSI and PCI were greatly impacted by the strength of the base structure; the result found that proper designed flexible base asphalt pavement using AH-30 asphalt with four different structural types had better or comparable performance over traditional used semirigid base asphalt pavement in terms of temperature stability, crack reduction, and fatigue resistance under the heavy loaded conditions. This research suggested designing a layer of stabilized macadam or ATB at the base to improve the overall strength and performance of the structure.

This paper presents the effect of temperature and tensile-strain rate on the mechanical properties of high-strength low-alloy structural Q460 steel. Standard coupon tensile tests were carried out to obtain the stress-strain curves of Q460 steel subjected to a temperature range of $25\mathrm{°C}–800\mathrm{°C}$. Three tensile-strain rates, namely, $0.001/\min$, $0.02/\min$, and $0.2/\min$, were selected to investigate the effect of strain rate on mechanical properties. Based on the stress-stain curves, the yield strength at different strain levels, tensile strength, and elastic modulus were determined. The reduction factors of mechanical properties of Q460 steel were calculated as the ratio of properties at elevated temperature to those at ambient temperature. The test results show that the strength and elastic modulus of Q460 steel remains 80% at temperatures lower than 500°C, and higher tensile-strain rate yields lower strength and elastic modulus properties. The reduction factors of mechanical properties decline significantly when the temperature exceeds 500°C, and the higher tensile-strain rate yields higher strength and elastic modulus properties. All the specimens experienced obvious necking before fracture and showed good ductility. Different high-strength steels exhibit different reduction factors even though the nominal strength of these steels is similar. The reduction factors suggested by other standards were not suitable to predict the properties deterioration of high-strength Q460 steels at elevated temperatures.

The danger of high-strength steel wire (HSSW) under high temperatures is twofold. One is the significant degradation of the material properties of high-strength steel (HSS), which has been extensively studied. The other, which appears to be important in some issues but has not been investigated, is that the breakage of HSSW is very hazardous from the perspective of dynamics because enormous stress can be released within a very short time. This paper reports an experimental study to quantify the transitory breakage instant. HSSW specimens with different section dimensions (intact 7.0 mm, intact 5.3 mm, and damaged 7.0 mm) were heated to failure under various steady prestressing forces at two constant temperature rates ($50°\mathrm{C}/\min$ and $25°\mathrm{C}/\min$). High-speed sampling technology was applied to capture the axial force variation before and during the rupture process. Through data regression, the breakage instant caused by high temperature was quantified by three elements, i.e., the ratio of initial force of breakage to prestressing force, the time history, and the breakage duration. The results showed that the parametric characteristics of rupture instant is dominated by the ratio of the prestressing force to the ultimate force at room temperature. In addition, the extent of the initial section damage has a positive relation with the initial force which indicates the start of the breakage.

Gas breakthrough pressure is of great importance for evaluating the sealing efficiency and assessing the long-term performance of saturated buffering materials with low permeability in the deep geological disposal of high-level radioactive waste. In this study, to investigate gas breakthrough properties, step-by-step (SBS), residual capillary pressure, and mercury intrusion porosimetry tests were conducted on saturated Gaomiazoi (GMZ) bentonite specimens. Results show that, compared with the other two methods, only SBS tests can accurately measure the gas breakthrough pressure. Meanwhile, the results of gas injection tests by the SBS method indicate that gas intrusion into a specimen in the inlet accompanied by water displacement at the outlet is not an instantaneous process. Therefore, the time required for pore pressure equilibrium during each pressure step was calculated, which is in inverse proportion to the intrinsic permeability of the compacted bentonite materials. Furthermore, the gas injection tests also show that gas breakthrough could also occur at lower pressure levels, i.e., snap-off pressure, which is far below the value of the breakthrough pressure. The differences between the breakthrough pressure and the snap-off pressure could be induced by the hysteretic behavior of the bentonite material during the drainage and imbibition processes. The delayed re-imbibition of water will induce further gas migration through the interconnected pore space and a lower capillary pressure. Experimental results in this work are very useful for the engineering design and safety assessments of the repository.

This paper investigates the critical impacts of the void morphology on the strength and damage responses of asphalt concrete as a time-dependent heterogeneous medium. First, efficient algorithms are developed to randomly fabricate the void morphology within a realistic microstructural representation of asphalt concrete. The algorithms take voids’ fundamental characteristics such as the content, shape, and size distribution into account to generate random void morphologies. Then, a nonlinear viscoelastic-viscodamage formulation based on principles of damage mechanics is used to run finite element simulations of the fabricated microstructures. The effects of varying the characteristics of voids are assessed in terms of stress distribution and damage evolution. Finally, a probabilistic analysis is conducted to evaluate the impacts of random void morphologies on the mechanical responses of asphalt concrete microstructural representations. The results indicate that unrealistic void representations lead to an overestimate in the strength of this time-dependent heterogeneous medium, and emphasize the importance of considering realistic void morphologies in mechanical analyses. The outcome shows that the developed algorithms provide a viable numerical tool to produce realistic representations of asphalt concrete.

This research presents a practice for quick treatment of voids in airport concrete pavements. Through combining two nondestructive test technologies, heavy weight deflectometry and ground penetrating radar, and polymer grouting materials, the current structural conditions of the pavement were evaluated, diseases were identified, and voids in the pavements were treated and filled. Accordingly, the damaged airport pavement was quickly rehabilitated, providing a practical method for the rapid treatment of voids in the concrete slab.

This research investigates the mechanical properties of asphalt concrete using aggregates consisting of limestone (L) and steel slag (S) blends. The properties of the L/S asphalt concrete were compared with those of L asphalt concrete. Two commercially available asphalt cements were used: asphalt cement penetration grade AC60/70, and polymer-modified asphalt (PMA). Test results indicated that S replacement improves the stability of L asphalt concrete. The flow value and the strength index were found to be insignificantly affected by the asphalt cement and aggregate. The stability of L/S asphalt concrete was higher than that of L asphalt concrete for both AC60/70 and PMA. The L/S asphalt concrete using AC60/70 exhibited a high stability compared with the limestone asphalt concretes using PMA. This indicates that the L/S asphalt concrete using AC60/70 can be used as a green and economical pavement surface for a high-traffic-volume road alternative to L asphalt concrete using PMA.

Reduction of water demand of cement pastes results in the decrease of the cement matrix porosity and, accordingly, in the increase of its strength and durability. The fluidity increase of the paste based on low-clinker binders with low water demand is one of the main problems in the production of cement composites with high strength and durability. This paper proposes a comprehensive approach to significantly reduce the water demand of low-clinker binders by using multicomponent supplementary cementitious materials of different origins as well as different methods of superplasticizer addition. Experimental studies determined practical possibilities of enhancing the superplasticizer effect in a wide range of low-clinker binders and combinations of supplementary cementitious materials (SCMs). Experimental results can be used to extend the classification of rheologically active SCMs for low-clinker binders.