Journal of Materials in Civil Engineering

A major concern with the application of water-foamed asphalt mixtures is the possible performance degradation caused by the presence of inclusion water during production. Inclusion water left in the asphalt mixture after compaction affects the performance of the asphalt mixture. The objectives of this study are to investigate the impact of different foaming conditions on the performance of water-foamed asphalt mixtures prepared using oven-dried aggregates, examine the freeze-thaw resistance of water-foamed asphalt mixtures, and assess the water-foamed asphalt mixture damage level after multiple freeze-thaw cycles through an ultrasonic direct test. The samples for this study were prepared in the laboratory based on the method of Superpave mix design. The control groups were mixed and compacted at 135°C and 148°C, respectively. The water-foamed asphalt binders were prepared at different foaming temperatures, i.e., 120°C and 135°C, and the amount of water agent used in this process was 0.0%–2.0% by mass of asphalt binder. The water-foamed asphalt samples were mixed at various foaming temperatures but compacted at 135°C. Based on the laboratory test results, the foaming temperature and the inclusion water from the foaming process significantly affected the air void and the tensile strength of the asphalt mixture and the void in the mineral aggregate. The freeze-thaw cycle accelerated the destruction of the internal structure of the asphalt mixture and resulted in an increase in porosity and decrease in cohesive strength between the asphalt binder and aggregate. The ultrasonic direct test method was found to be a feasible approach to assessing the potential damage in water-foamed asphalt mixtures.

In this study we analyzed the use of high-performance structural concrete reinforced with polypropylene fibers in applications requiring long exposure times to high temperatures, such as thermal energy storage systems. We analyzed the behavior of the concrete at different temperatures (hot tests: 100°C, 300°C, 500°C and 700°C), cooled-down states (cold tests) and exposure times (6, 24, and 48 h). We also experimentally determined the thermogravimetric analysis, fracture behavior, compressive strength, Young’s modulus, and tensile strength of concrete. Subsequently, we performed a comprehensive analysis of the thermal and mechanical behavior of high-performance concrete under different thermal conditions. We applied longer exposure times to broaden the available results on the behavior of high-performance fiber-reinforced concrete when subjected to high temperatures. Results show that, once thermal and moisture equilibriums are reached, exposure time does not have any influence on mechanical properties. They also provide useful information about the influence of high temperatures on the different parameters of fiber-reinforced concrete and its application for thermal energy storage structures.

Although corrosion of metal in soils has been intensively investigated in the past, a review of the published literature shows that limited research has been undertaken to understand how soil properties affect the corrosion behavior of cast iron pipes, owing to the scarcity of the reported information on buried metal corrosion in its backfill soil condition. In this paper, a methodology is proposed to statistically analyze the effects of soil properties on corrosion behavior, and a comprehensive and long-term historical corrosion database of buried cast iron pipes is thoroughly interpreted. The corrosion is characterized by two time-independent parameters in each sample, that is, the proportionality ($k$) and exponent ($n$) factors of the power law model. It is found that the exponent factor $n$ of power law model is closely associated with the level of soil aeration. It is also found that grouping corrosion data based on soil aeration produces stronger correlations between soil properties and corrosion rates compared with that when taking all soil samples as a whole. The authors conclude that an appropriate classification of soils can benefit the identification of key factors influencing corrosion of buried cast iron pipes at different exposure times. This research provides further knowledge for asset managers and engineers to accurately predict the failure of corrosion-affected cast iron pipes.

Rammed earth construction is an ancient technique using local soils that are compacted to form structural elements. This method has attracted renewed interest throughout the world due to its social, economic, and environmental benefits. This paper furthers the understanding of rammed earth as an engineering material. A local soil is selected as representative of readily available matrix material and its suitability is studied by conducting compression, tension, bending, and durability tests on the end product. The viability of using a natural soil with high fines content is adopted as one of the key target elements of this research. The effect of using varied percentages of two stabilizers, cement and natural lime, on the mechanical properties of rammed earth is also assessed. Additionally, the efficacy of reinforcement using hemp fibers to improve tensile properties is investigated. Experimental results show that natural soils with high fines content are a viable construction material when stabilized by a combination of lime and cement. For this optimal combination, the compressive strength improves roughly threefold and the durability performance is enhanced to acceptable levels. Furthermore, the combination of 6% chemical stabilization and 0.75% fiber reinforcement is found to provide optimal benefits in imparting tensile strength and toughness to rammed earth. The obtained improvements are on the order of 500% and 30,000% in the tensile strength and toughness, respectively.

The mechanical behaviors of rock under the combined action of high temperature and cyclic loading are a current concern in rock mechanics. In this study, biotite granite samples were thermally treated at the temperatures 20°C, 200°C, 400°C, and 600°C. Then, the samples were repeatedly impacted in a modified split Hopkinson pressure bar (SHPB) with the striking velocities 12, 15, and $18\mathrm{m}/\mathrm{s}$. The dynamic stress-strain curves were measured, and the failure modes were observed. The experimental results showed that the samples heat-treated at each temperature had a damage threshold and that the threshold was the lowest after the 600°C treatment. The damage induced by the repeated impact was not significant if the loading was less than some critical value. The stress-strain responses including the strain rate and peak stress under repeated impact were similar at treatment temperatures ranging from 20°C to 400°C. The stress-strain curve first went up and then shifted right. Within the range of this study, the average strain rate was the highest for the sample after the 600°C treatment whereas the peak stress was the lowest. An apparent deterioration of the mechanical properties was detected. The resistance to the repeated impact was the strongest for the sample heat-treated at 200°C. This showed that the hardening effect induced by temperature overtakes the damage-softening effect. The 600°C treatment sample had the most severe failure degree and the most complex failure mode, possessing the characteristics of axial splitting and dynamic crushing. Thus, a threshold temperature for biotite granite may exist between 400°C and 600°C.

This study was intended to evaluate how citric acid influences the time-dependent rheological properties of magnesium oxychloride cement (MOC). For this purpose, rheological parameters, setting time, electrodeless resistivity, crystal phases, morphology, hydration product, and compressive strength were investigated. The results show that the addition of citric acid can improve the time-dependent rheological properties of MOC pastes due to the retarding effect of the citric acid. The citric acid dosages of 0.15, 0.25, and 0.35% can stabilize the rheological properties of MOC paste in 1, 2, and 3 h, respectively. The addition of citric acid prolonged the setting stage by introducing free ${\mathrm{H}}^{+}$ that weakened the flocculated structure of MOC paste and delayed the formation of $5\mathrm{MgO}·{\mathrm{MgCl}}_2·8{\mathrm{H}}_2\mathrm{O}$. The early compressive strength was significantly decreased with increasing dosages of citric acid; however, the citric acid had less of a negative effect on the late compressive strength.

The influence of rubber crumbs on the dilatancy behavior and critical state of steel furnace slag (SFS), coal wash (CW), and rubber crumbs (RC) mixtures was investigated via a series of monotonic drained triaxial tests. These tests revealed that RC contents ($R_b$, %) have a significant influence on the dilatancy behavior and critical state of the aforementioned waste mixtures; in fact, as more $R_b$ is added, dilatancy and the slope of the critical state line in $e-\ln p^{\prime }$ space decreases. Within the framework of critical state soil mechanics, a dilatancy model for $\mathrm{SFS}+\mathrm{CW}+\mathrm{RC}$ mixtures was proposed and validated using experimental data. This model also captured the energy-absorbing property of RC using an empirical relationship between the total work input $W_{\mathrm{total}}$ and the critical stress ratio $M_{\mathrm{cs}}$.

Lignin is an organic industrial by-product, stockpiles of which are rapidly accumulating worldwide. A feasibility investigation was carried out with respect to the stabilization of silty soils using lignin. The fall cone test method was employed to determine the undrained shear strength ($s_u$) and Atterberg limits of the lignin-stabilized silty soil with 7 days of curing. In addition, scanning electron microscopy (SEM) was conducted to qualitatively evaluate the changes in the microstructure of silty soil after treatment and better understand the mechanisms controlling the improvement in $s_u$ of the stabilized silty soil. The study revealed that the $s_u$ of silty soil increased with an increase in lignin content. This was mainly attributed to the bonding effect of lignin-based cementing materials, which creates the aggregation of soil particles and fills the pores between detached particles. The liquid limit ($w_L$) increased remarkably with increasing lignin content and the maxium increment of 27% occurred at 12% lignin-stabilized soil. The chemical composition of added lignin had a considerable influence on the Atterberg limits of the stabilized silty soil. The $s_u$ was found to exhibit good exponential decreasing correlation with the moisture content ($w$) as well as the liquidity index ($I_L$). By comparing the $s_u$ values with the empirical models in the literature, the new relationships among $s_u$, $w$, and liquidity index ($I_L$) were finally proposed for estimating the $s_u$ value of the lignin-stabilized soils. It is concluded that the application of reclaimed lignin as a silty soil stabilizer can be one of many viable answers to the development of environmentally friendly soil stabilizer and the profitability of industrial by-products.

In the existent methods for investigating the potential of moisture damage based on thermodynamic concepts in asphalt mixes, the role of asphalt binder aging on thermodynamic parameters has not been considered. The current method described in this paper was developed to investigate the effect of asphalt binder aging on moisture sensitivity of asphalt mixes using mechanical and thermodynamic tests. Eight different asphalt mixes, including two types of asphalt binder with different penetration grades (60–70 and 85–100) and two types of aggregates (limestone and granite), were investigated using a liquid antistripping additive in two controlled and aged states. Thermodynamic parameters related to moisture sensitivity of asphalt mixes were calculated using surface free energy (SFE) components of aggregate, asphalt binder, and water (with and without considering aging). Then the relationship between debonding energy and the indirect tensile strength ratio of different specimens was investigated via statistical analyses. Results of SFE parameters of the aged and controlled asphalt binder showed that asphalt binder aging causes an increase in absolute value of debonding energy, adhesion free energy, and cohesion free energy of compounds made with Asphalt Binder 85–100 and leads to the reduction of adhesion free energy and cohesion free energy of compounds made with Asphalt Binder 60–70. The relationship between results of debonding energy in two controlled and aged asphalt binder states and the indirect tensile ratio showed that these two indicators are strongly correlated. The correlation coefficient between the moisture sensitivity indicator and debonding energy of specimens in two controlled and aged states was 0.65 and 0.77, respectively. The high correlation between results of the tensile strength ratio (TSR) and debonding energy with aged asphalt binder indicates the necessity of using SFE components of asphalt binder after aging in thermodynamic calculations.

This study compared two binder systems composed of reactive magnesite cement (RMC) and calcined dolomite (D800), which were produced via the calcination of magnesite and dolomite at 800°C, respectively. The environmental impacts of the production of both binders were supported with an investigation of their strengths and microstructural development in concrete samples subjected to different curing conditions. The lower energy and ${\mathrm{CO}}_2$ emissions associated with D800 production led to reduced damage to human health and the ecosystem in comparison with RMC production. The mechanical performance of both binder systems depended on their mix composition and curing conditions. Both benefited from the use of high humidity (90%), whereas elevated temperatures (60°C) presented an advantage only in RMC samples. The combination of high humidity and temperature enabled increased MgO dissolution and enhanced hydration/carbonation in RMC samples, thereby leading to higher strengths. D800 samples revealed lower strengths due to their lower initial MgO contents and initial porosities. Results of this study indicated the importance of customized curing conditions depending on the mix design and binder component.

In order to investigate the ultra-low cycle fatigue (UCLF) fracture in welded connections of high-strength steel (HSS) under earthquakes, this paper studies micromechanical fracture models for Q460C steel, which has wide application prospects in China. Notched round bars and smooth round bars, which were manufactured from base metal, heat-affected zone (HAZ), and weld metal of Q460C HSS, were tested under monotonic loading and cyclic loading, respectively. The fracture surface of tensile specimens were analyzed by scanning electron microscope (SEM) tests. This paper presents the results, including the skeleton curve, hysteresis loops, low cycle fatigue life, and characteristic length $l$. By comparing the experimental results with the finite-element analyses, the toughness parameters of the void growth model (VGM), the stress-modified critical strain (SMCS) model, and the cyclic void growth model (CVGM) of Q460C HSS and its weld were calibrated. Results indicate that the toughness parameters of various materials for HSS are generally lower than that of normal strength steel. Also, in the welded beam-to-column connections, the HAZ requires more attention. The results can be used to effectively and accurately evaluate the UCLF fracture in welded HSS connections.

Hardening stresses are generated as concrete hardens when the volume shrinkage of the concrete mortar is restrained by the aggregates. In the early stages of concrete curing, random cracking tends to occur because the structural strength of a concrete structure is relatively low and is likely exceeded by the concrete shrinkage-induced hardening stress. This is the primary cause of the initial damage in concrete. To investigate the initial damage in concrete, an exponential model for strain hardening is combined with a spline interpolation method to characterize the anisotropic hardening process in a three-phase structure that consists of aggregates, cement mortar and an interfacial transition zone (ITZ). A nonlinear analysis using a stress/strain softening damage model is then performed to analyze the characteristics of the shrinkage-induced initial damage in the concrete and the influence of the aggregates on the structural damage. To calculate the magnitude of the initial damage in concrete, damaged and undamaged concrete specimens are subjected to uniaxial loads. The results show that the shrinkage-induced damage initiates at the surfaces of aggregate particles and in the ITZs and then propagates into the cement mortar. The initial damage to the concrete is influenced by the volume fraction and geometric characteristics of the aggregate. These characteristics are analyzed using a random aggregate model and compared with computed tomography images of a cross section of concrete.

This paper reports the results of an investigation carried out to understand the influence of two different diatomaceous earths on the service life of natural fibers in cement composites. Deterioration of the embedded natural fiber was determined using two methods: development of flexural properties of natural fiber-reinforced mortar under accelerated aging, and direct investigation of fiber strength and components by means of micro-force tensile testing and thermogravimetric analysis. By replacing 20% cement with natural mineral admixture (diatomaceous earths), the cement hydration was enhanced and 24.4% calcium hydroxide was consumed, generating a mild environment for the natural reinforcement. The tensile strength of the aged natural fiber after 20 wetting and drying cycles was improved by 3.8 times. Due to fiber degradation, the flexural strength and toughness of fiber-reinforced cement mortar decreased by 90% and 98%, respectively, after 10 wetting and drying cycles. By incorporating diatomaceous earths, after 10 wetting and drying cycles, flexural strength and toughness as high as 5.3 and 7.9 times, respectively, of those of the control group were observed, suggesting that the degradation in the flexural properties of the cement composites was effectively mitigated. The influence of diatomaceous earths on the hydration of cement and its correlations with the durability of the fiber and composites were also studied. Investigations of the deterioration in interfacial bonding between cement matrices and aged natural fibers and the optimization of the pozzolanic activity of diatomaceous earths in cementitious systems are recommended as future work.

This study aims to develop a new self-deicing technology that can clear ice/snow with high efficiency and achieve rapid assembly on site. A prefabricated flexible conductive composite overlay for active deicing and snow melting is put forward. The overlay consists of three layers, including (1) a functional layer where carbon-fiber heating wires (CFHWs) are distributed in a polyurethane rubber sheet, (2) gravel bonded to the upper surface of the functional layer by epoxy resin as a wear layer, and (3) aluminum foil film adhered to the lower surface of the functional layer by pressure-sensitive adhesive as a heat-insulating layer. Experiments were performed to test the mechanical properties (e.g., flexibility, durability, and skid resistance) and snow-melting performance. The results indicate its mechanical properties meet the road performance requirements. This overlay can be used as a temperature-adjusting overlay that can effectively overcome the influence of ice and snow on pavement structures and road safety. Meanwhile, its flexibility makes it easy to carry and make an assembled pavement that is friendly to both old and new pavements.

Geosynthetics have been successfully used to stabilize granular aggregate over weak subgrade in recent years. In some actual applications, geosynthetics are first used to stabilize aggregates over weak subgrade as construction platforms to carry construction loads, and then the construction platforms become subgrade in pavement structures. Unfortunately, no commonly accepted method is available to quantify the benefit of construction platforms with geosynthetics in pavement design. This study aimed to quantify this benefit by treating the geosynthetic-stabilized construction platform as an “equivalent subgrade.” The quantification was based on the cyclic plate loading test results of nine test sections of nonstabilized and multiaxial geogrid-stabilized aggregate over weak subgrade and five test sections of homogeneous subgrade with California bearing ratios (CBRs) ranging from 2.9 to 9.5. The permanent deformations of these test sections were recorded and used to estimate the equivalent CBR values of the geogrid-stabilized aggregate over weak subgrade. The test sections that had the same performance (i.e., permanent deformation) under the same number of loading cycles were considered equivalent. The analysis of test results shows that the equivalent CBR values of the nonstabilized and geogrid-stabilized test sections decreased with the increase of the load intensity. The percent of equivalent CBR increase of the granular bases over the weak subgrade due to the inclusion of a geogrid ranged from 30% to 85%.

A long-term exposure test of reinforced concrete (RC) beams with different flexural loads in a tidal environment has been conducted by taking the influence of time-dependent chloride diffusivity into consideration. According to the calculated apparent chloride diffusion coefficients, a chloride transport model under the coupling stresses at different depths and chloride action was established. Results indicated that the influence of flexural loads on free chloride concentrations and apparent chloride diffusion coefficients was obvious in tensile concrete zones. However, it was not a simple inhibition in compressive concrete zones. When the flexural load is less than 30% of the ultimate bearing capacity ($F_{\max }$), its effect on apparent chloride diffusion coefficients in concrete is slight. However, when 45%–60% $F_{\max }$ is exerted, a critical compressive stress can be detected. After exceeding the critical compressive stress, the chloride transport in concrete will be accelerated. Moreover, when the flexural load reaches 60% $F_{\max }$, the critical compressive stress of accelerating chloride transport, which is 5.848 MPa, that is, 20% of the cubic compressive strength ($f_{\mathrm{cu}}$), appears.

Rock mass is a structural system with intact rock cut by cracks. The properties and strength of cracks determine the macroscopic mechanical properties of rock mass. Improving the self-stability of rock mass by enhancing the shear strength of the cracks is currently a cutting-edge topic in the geotechnical field. As a new reinforcement method for cracks, biological healing technique has attracted much attention. This paper applies bacteria-induced calcium carbonate mineralization to heal cracks in migmatitic granite and conducts relevant mechanical tests. Sporosarcina pasteurii (lyophilized powder) is activated in the laboratory and used to induce calcium carbonate mineralization on a crack in migmatitic granite. Healing and reinforcement of cracks is realized. The mineralization products on the crack are observed using X-ray diffraction and scanning electron microscopy. The mineralization products are bacteria-induced calcium carbonate precipitates. The crystals are cubic in shape with a side length of about 5–10 μm and helical dislocation structure. At this moment, the cracks in migmatitic granite are completely cemented. Finally, shear tests are conducted on the healed and reinforced cracks. The tests results indicate that bacterially induced calcium carbonate mineralization can greatly improve the shear stiffness, peak shear strength, and residual strength of cracks, and the healing effect is time-dependent. The results of this study show that the bacterially induced mineralization technique not only can enhance the integrity of the rock cracks, but also can significantly improve the shear capacity of the cracks. This healing technique can provide new ideas in reinforcing cracks in rock masses.

The surface free energy (SFE) components obtained from the Good–van Oss–Chaudhury (GvOC) method have been demonstrated to depend strongly on the selected test liquid set. To address this issue, the condition number approach and the equation of state (EQS) approach were proposed previously to select appropriate test liquids. However, little work has been done to verify the consistency of the calculated energy parameters using the various liquid sets. This study was aimed at obtaining consistent energy parameters using different liquid sets designed by five test liquids, which are distilled water (W), formamide (F), glycerol (G), ethylene glycol (E), and diiodomethane (D). A new approach was proposed to make use of the Owens–Wendt (OW) model to calculate the energy parameters with WFED and WFGED considered as the optimum liquid sets. The calculation results indicate that the calculated energy parameters are consistent when using the optimum liquid sets and the rankings of energy ratios are consistent with the boiling water test results for different asphalt mixtures, which fully validates the feasibility of the proposed approach.

In this study, water transport in concrete was investigated using an environmental simulation test system, and the boundary conditions of water transport on the concrete surface are proposed in this paper. The water influential depth in concrete was deduced by analyzing the influence of several factors. Moreover, a numerical simulation method was proposed to analyze the influence of wind speed on the mass transfer coefficient and water distribution in concrete. Results indicated that the water distribution and transport process can be represented by the finite difference method and Fick’s diffusion law, but the corresponding water diffusion coefficient of Fick’s diffusion law differs between the wetting and drying processes. In addition, numerical simulation showed that environmental relative humidity can be considered the interface relative humidity when the value of wind speed multiplied by critical time exceeds a certain value. A good relationship between the equilibrium time ratio and influence factors (i.e., water-to-cement ratio, initial water saturation of the concrete, and environmental water saturation degree imposed on the concrete surface) manifested in terms of an exponential function. Furthermore, the water influential depth in concrete and the square root of the wetting time had a linear relationship.

The compressive creep of concrete is normally adopted to predict the stress or the time-dependent deformation of concrete members, without considering the difference of creep under different loading types, i.e., compressive, tensile, and flexural loads. This will inevitably lead to inaccurate prediction of stress and deformation, particularly at early ages when creep effect is pronounced. This study conducts a systematic creep comparison for early age concrete under different loading types and curing conditions. Three types of creep devices are developed for compressive, tensile, and flexural creep measurements of concrete under both sealed and drying conditions. Low-strength and high-strength concretes with water:cement ($w/c$) ratios of 0.3, 0.4, and 0.5 are tested at the age of 7 days. The measured creep is compared in terms of loading types and curing conditions (sealed versus drying). The ratios of different types of creep are quantified and compared with the literature. The rationality of using compressive creep to substitute tensile or flexural creep is justified. The results of this study provide quantitatively the creep difference under different conditions, which helps to gain confidence about the predicted stress and the strain when different creep models are used.

The sigmoidal master curve model can be used to obtain the value of dynamic modulus of asphalt mixtures at a high or low temperature, which cannot be obtained directly from laboratory tests. However, some studies indicated that the precision of this model should be investigated at a high temperature. Therefore, the objective of this study was to analyze the prediction precision of the sigmoidal master curve model on dynamic modulus of asphalt mixtures and find out the critical factors influencing the prediction precision for further calibration of the sigmoidal model. A database of dynamic modulus values, including different aggregate sources, types of layers, contents of reclaimed asphalt pavements (RAPs), antistripping agent types, warm additives, and aging states, was used for the analysis. Firstly, single-factor analysis was conducted with the analysis of variance (ANOVA) table. Furthermore, the interaction among variables was analyzed through coupling analysis by the software Minitab 17. The results indicate the temperature has an influence on two-factor and three-factor interactions. For further study, the sigmoidal master curve model should be calibrated by introducing new variables to improve its accuracy.

This study evaluated the self-healing capability of engineered cementitious composite (ECC) produced with 5% MgO expansive agent (MEA) compared with standard ECC counterparts. The efficiency of the proposed ECC-MgO self-healing system was studied based on the rapid chloride ion permeability (RCP) and sorptivity behaviors of the virgin and cracked specimens when exposed to water, natural, and autoclave curing conditions for different durations. Test results indicated better resistance to chloride ion penetration in addition to significant reduction in sorptivity indexes (considered as measures of self-healing capability) for water- and natural-cured preloaded cracked ECC-MgO specimens compared with their ECC counterparts. The higher self-healing ability of ECC-MgO system was attributed to the formation of healing compounds within the crack walls due to the delayed MEA hydration, as confirmed from microstructural characterization based on scanning electron microscopic (SEM) analyses. The study revealed the potential of using the self-healing ECC-MgO system as sustainable and durable material for infrastructure applications.

Fatigue damage and accumulation of permanent deformation or rutting are the two most prevalent distress mechanisms in flexible pavements. The aim of this study was to investigate rutting resistance and fatigue cracking in Gilsonite-modified asphalt binders. In this regard, the primary objective was to study the effect of Gilsonite content, binder type, and temperature on permanent deformation of asphalt binders. The Superpave rutting parameter ($|G^{*}|/\sin \delta$) was calculated and the multiple stress creep and recovery (MSCR) test was performed for this purpose. The secondary objective was to evaluate the effect of Gilsonite content, binder type, and strain level on fatigue performance of asphalt binders. This was achieved using the linear amplitude sweep (LAS) test. According to the results, the addition of Gilsonite improved rutting resistance and fatigue properties of the asphalt binder. In addition, the results of evaluating the rutting parameter showed a good correlation between MSCR creep compliance ($J_{\mathrm{nr}}$) and Superpave rutting parameter ($|G^{*}|/\sin \delta$) in Gilsonite asphalt binders. The findings of this study indicate that Gilsonite-modified binders have better fatigue and rutting performance than the base binder, and Gilsonite is an economical choice and a suitable alternative for improving the asphalt binders’ properties at high and medium temperature ranges.

Geotextiles are commonly used in road design to provide mechanical and hydraulic functions due to their high strength and porous properties. The long-term performance of a soil–geotextile system is not solely determined by the soil or the geotextile itself; it also depends upon their interactions. Emphasizing only the geotextile mechanical functions cannot solve all engineering issues. The performance of a soil–geotextile system can be disappointing when the soil moisture content increment is small. Capillary water exists in a variety of soils and can be difficult to drain under unsaturated conditions. Unfortunately, the existing subsurface drainage design methods can only deal with free water (water that flows under the influence of gravity) and conventional capillary barriers cannot wick water out of pavement structures, resulting in overestimating the long-term performance of the pavement. A new geotextile with wicking fabrics has the potential to solve this issue. Preliminary laboratory and field tests have proved its effectiveness to wick both gravitational and capillary water under unsaturated conditions. This paper further explores some potential concerns regarding the future extensive applications of this new geotextile. A series of lab tests were performed to study the working mechanism of the new geotextile, evaluate its drainage efficiency, and assess the effects of splice and clogging on the drainage performance of the new geotextile. Test results indicate that the new geotextile can effectively drain both gravitational and capillary water out of pavement structures; however, splices may reduce the drainage efficiency. The clogging effect should not be a major concern for the long-term performance of the new geotextile in soils with fine content lower than 14.5%.

This paper features the development of a probabilistic model linking freeze–thaw (F-T) performance of concrete mixtures to their composition. A sensitivity analysis was performed on several concrete mixture parameters to identify the factors that have strong correlations with F-T resistance of concrete. The F-T performance level was defined as a discrete measure of the frost resistance of concrete. Finally, a new model to predict F-T damage incorporating the variability in concrete mix parameters (as selected from sensitivity analysis) was developed. This model was developed using only those data sets that contained the results of the relative dynamic modulus of elasticity (RDME) testing performed according to ASTM and AASHTO specifications. Concrete mixtures containing only ordinary portland cement (OPC) as the sole binder (i.e., mixtures that did not contain any supplementary cementitious materials) were considered. The reliability of the model was demonstrated using several examples of concrete mixtures of various compositions. Accordingly, this model provides the opportunity to optimize the concrete mix proportion for the required performance level of concrete under F-T exposure condition.

The fracture behavior and the dilatant crack opening in the shear response of self-consolidating concrete (SCC) with discrete steel fiber reinforcement were investigated. The volume fraction of hooked-end steel fibers in concrete was 0.75%. The fracture behavior of steel fiber reinforced SCC (SFRSCC) was investigated using notched beams tested in flexure. In SFRSCC, there was a significant increase in fracture energy at a small crack opening. The significant postcracking resistance to crack opening provided by fibers in an SCC matrix resulted in a twofold increase in energy up to 0.1 mm crack opening. In SFRSCC, there was a tenfold increase in energy up to 1.0 mm crack opening, which was associated with multiple cracking in the matrix. In the second stage of the experimental evaluation, the shear behavior of SCC with and without steel fibers was investigated using a shear beam arrangement. The dilatant behavior of the shear crack was established from in situ full-field displacement measurements from across the primary shear crack, obtained using digital image correlation (DIC). There was a continuous slip between the faces of the shear crack, which produced a continuous increase in the crack opening. Shear crack in SCC beams curves in a direction governed by the applied stress field. Failure in SCC is very brittle and occurs at small crack openings which are less than 0.1 mm. The sudden loss of internal stress transfer across the primary shear crack produces failure in SCC beams. In SFRSCC, the primary shear crack formed at a load that was nearly double the load at the formation of the shear crack in SCC. The dilatant behavior in SFRSCC was identical to the dilatant behavior obtained from SCC without fibers. In SFRSCC, there was an increase in load-carrying capacity with a continued opening of the shear crack, and load transfer across the primary shear crack was sustained for a larger crack opening. Due to increased contact stress on the crack faces induced by high cohesive crack closing stress produced by fibers, the shear crack at the neutral axis continued to propagate along the initial angle, resulting in a straight crack path without curvature. There was a stress transfer across primary shear crack openings up to 1 mm due to the crack closing stress provided by the fibers. A secondary shear crack in SFRSCC beams led to failure. The improvement in the fracture response of SCC with the addition of fibers results in an increase in shear capacity through better crack control.

In order to reproduce the atmospheric corrosion process of weathering steel (WS), a three-dimensional (3D) cellular automata (CA) based method is proposed. Firstly, the atmospheric corrosion mechanism of WS is described. Basic assumptions are made with the purpose of simplifying the complicated corrosion process. The evolution rules of atmospheric corrosion are then proposed and the software program is developed. Secondly, the results obtained from the CA model are compared with the basic corrosion laws verified by several experiments. Results show that the basic hypotheses and evolution rules are reasonable and the model is reliable, and thus can be used to describe and to identify the corrosion kinetics, corrosion morphology, and distribution characteristics of pits for WS in atmosphere. Finally, the parameter analysis is performed and the relationship between CA model and atmospheric exposure test is established to achieve the model application. Based on the relationship, the CA model can be used to continuously predict the corrosion behaviors of WS in the long-term atmospheric corrosion process. Good agreement is obtained between the experimental and numerical results.

This paper presents a probabilistic approach for evaluating the lifetime of reinforced concrete (RC) pipe piles subjected to chloride environments. A predictive model is developed for modeling the deterioration process of RC pipe piles in order to estimate the probabilistic lifetime of RC pipe piles subjected to chloride environments. The time-dependent probabilistic lifetime analysis of RC pipe piles is carried out in the framework of Monte Carlo simulation. An illustrative example of the proposed approach is demonstrated to estimate the probabilistic lifetime of RC pipe piles, and subsequently the sensitivity analysis of governing parameters is conducted to study the effect of the random variables on the probabilistic lifetime of RC pipe piles. The analysis results show that the lifetime depends highly on the governing parameters for corrosion initiation. The failure probability over the lifetime is more sensitive to variations of the governing parameters for corrosion initiation than to variations of the governing parameters for crack initiation.

Fatigue cracking performance of asphalt mixtures is highly influenced by the binder and air-void contents, binder grade, binder modification, volumetrics, recycled asphalt pavement/reclaimed asphalt shingles (RAP/RAS) content, and aging. In Oregon, asphalt pavements commonly fail prematurely due to cracking-related distresses, necessitating costly rehabilitation and maintenance at intervals of less than half of the intended design lives in some cases. This study focuses on characterizing the cracking performance of asphalt mixtures used in Oregon by evaluating the impact of asphalt mixture variables, such as binder content, air-void content, aggregate gradation, and polymer modification, on cracking and rutting performance using semicircular bend (SCB) and flow number (FN) tests, respectively. The goal of this study is to provide a better decision-making structure during the pavement design stage to address fatigue cracking susceptibility, with the intent of avoiding premature pavement failure and expensive early maintenance and rehabilitation. Increased binder content improved the cracking performance, suggesting that increasing binder content of asphalt mixtures currently used in Oregon can create significant savings by improving pavement longevity. Additionally, reducing the density increases cracking performance; therefore, producing asphalt mixtures that are easy to compact and utilizing intelligent compaction technologies that are currently being implemented in Oregon can potentially create a significant improvement in the fatigue cracking resistance of asphalt mixtures.

This paper reports a novel methodology to manufacture geopolymer coarse aggregate (GPA) using low calcium fly ash. The developed methodology is outlined together with a systematic experimental study undertaken to examine a viable manufacturing process for GPA production and the consideration of key mechanical properties and durability characteristics of GPA concrete up to 90 days. GPA with a dry compressive strength in excess of 50 MPa can be manufactured using a solid cylindrical mould with compression applied using a cylindrical piston. The key mechanical properties investigated for GPA concrete demonstrate a good correlation with the compressive strength to conventional crushed aggregate concrete. Concrete with mean compressive strength up to 37 MPa can be produced using the innovative GPA concrete. The GPA concrete demonstrates low water and air permeability indicating that the material is a high-quality concrete with a dense pore structure. Overall, GPA investigated in this research shows potential as a lightweight coarse aggregate in portland cement concrete, with the significant additional benefit of addressing and reducing the environmental impact of fly ash from coal fired power generation.

In the present investigation, asphalt pellets containing steel grit have been prepared and tested as an energy-efficient and durable alternative to conventional road construction materials, such as hot- and cold-asphalt mixtures. Among other advantages, this technology is highly energy-efficient and could reduce traffic disruption and improve health and safety conditions for operators. Pellets are simply used in the road by laying, induction-heating, and compacting them. In the paper, their heating potential under the action of electromagnetic induction, and volumetric and mechanical properties of the material resulting after compaction, such as tensile strength, shear strength, and resistance to permanent deformation, were obtained to assess the proposed technology and compare it with hot- and cold-mix asphalt. The results have shown that the technology can be a strong competitor among current repairing materials for isolated and punctual potholes but still cannot be offered as a substitute for major maintenance operations, such as road milling and repaving.

Sand solidification technology is widely applied in engineering. This paper presents experimental methods to analyze the effect of adding urea to a culture medium for sand solidification. The results show that adding urea to the culture medium increases urease activity and inhibits bacterial growth, and the optimal amount of added urea is between 5 and $20\mathrm{g}/\mathrm{L}$. Adding urea after sterilization markedly increases the strength of the injecting path for sand column solidification. However, a long injecting path leads to differences in strength between the entrance section and middle section, resulting in lower overall strength. The faster the injection speed, the higher is the overall strength of the sand columns. When $20\mathrm{g}/\mathrm{L}$ of urea is added, the overall strengths of the solidified sand columns increase with larger sand particle size. Adding different amounts of urea is suitable for the solidification of corresponding sand column sizes. Therefore, adding urea to the culture medium for sand solidification is significant for various sand particle sizes. The results will act as a guide for the application of sand solidification technology.

This study investigated the shear strength of asphalt mixtures and its influence factors by using a three-dimensional (3D) discrete-element method (DEM). The uniaxial penetration test, a shear strength test method for asphalt mixtures, was briefly introduced. A 3D micromechanical model for predicting asphalt mixture shear strength was established by using Particle Flow Code in Three Dimensions. The effects of aggregate size, temperature, asphalt content, and loading rate on asphalt mixture shear strength were simulated based on this model. Simulation results were verified via an actual uniaxial penetration test. The results showed that asphalt mixture shear strength could be effectively simulated based on 3D micromechanical DEM. Aggregate size, temperature, asphalt content, and loading rate significantly affected asphalt mixture shear strength. Shear strength increased with an increase in nominal maximum aggregate size (NMAS) or loading rate, decreased with an increase in temperature, and was the highest with the optimal asphalt content at 60°C.

Asphalt pavement cracks easily in low-temperature environments. In order to address the problem, phase-change material (PCM) microcapsules working at 0–10°C are used to replace some of the aggregates in asphalt. In this study, PCM microcapsules with a high-temperature epoxy resin adhesive as reinforcement phase were prepared by using $n$-tetradecane/tetradecanol as the core material and melamine-urea-formaldehyde as the wall material. The reinforced PCM microcapsules were blended into the asphalt modified by styrene-butadiene-styrene block copolymer (SBS) modified asphalt, the PCM microcapsules were used to replace part of the same amount of the coarse aggregate. The results depict that the reinforced PCM microcapsules can satisfy the requirements of both immersion Marshall test and freeze-thaw splitting test. Above all, asphalt mixtures containing reinforced PCM microcapsules have been proved acceptable via dynamic stability tests. The bending beam rheometer test results imply that asphalt mixture containing PCM microcapsules revealed good crack resistance at low temperatures. Compared with the asphalt mixture sample in the reference experiment, the temperature difference of that containing the reinforced PCM microcapsules could reach 2.1°C, indicating a promising application prospect.

Accurate, quick, and nondestructive in situ tests for measuring pavement stiffness, or elastic modulus, are an increasingly important element in pavement management systems. This is due to the increasing number of aged road networks and the limited budget allocated by the government for pavement monitoring and maintenance. This paper aims to propose a new wavelet-spectrogram analysis of surface wave (WSSW) technique for nondestructive testing and in situ measurement of pavement surface layers. The proposed technique was developed on the basis of the spectral analysis of surface wave (SASW) and modified data analysis of the ultrasonic surface wave (USW) methods. This technique uses two receivers to detect and record the signals of the surface wave propagating on a pavement surface. In wavelet analysis, the received signals are transformed into a time-frequency domain and displayed in a spectrogram. The spectrogram was generated on the basis of the mother wavelet of the Gaussian derivative (GoD). A wavelet filtration technique was also used in the time-frequency spectrogram to diminish the effect of the noise signal recorded during field measurement. The unwrapped phase of a different spectrum was generated from a selected wave energy in the spectrogram to obtain a phase velocity; this was performed through a linear regression analysis for calculating the value of the slope of a phase velocity. The elastic modulus of the pavement surface layer can be obtained via a linear relationship of assumed density, measured phase velocity, and assumed Poisson’s ratio of pavement materials. The results can be used to show that the proposed technique can be of practical use for in situ elastic modulus measurement on flexible and rigid pavements. It can also be used to determine any changes that might occur in the stiffness of the pavement surface layer.

Eiffage developed a high-performance bituminous mixture known as GB5. It is based on aggregate optimization method. This paper presents the results of a research project checking whether, in the small strain domain, this type of mixture behaves like the more conventional asphalt mixture GB3 currently used as a base layer in French bituminous pavements. Three-dimensional complex modulus tests are performed on GB5 and GB3, two hot mixtures asphalt (HMA) made with the same bitumen but produced with different aggregate skeletons. Tension-compression sinusoidal testing is applied to the specimens over a wide frequency and temperature range. Both axial and radial strains are monitored, thereby allowing the computation of the complex Young’s modulus and complex Poisson’s ratios. From the experimental results, the time–temperature superposition principle (TTSP) is verified for both complex Young’s modulus and complex Poisson’s ratios in two directions. The obtained shift factors and normalized complex modulus curves for the two mixtures indicate that the bitumen phase drives the viscoelastic behaviour of the asphalt mixture, regardless of the granular skeleton. The effect of air-void content on the static, glassy, and characteristic time values of modulus and Poisson’s ratios, which is obtained from simulation using a linear viscoelastic model with two springs, two parabolic elements, one dashpot, is analyzed. The anisotropic properties of the two mixtures and the reproducibility between the two laboratories is also checked.

The effects of hammer peening on the fatigue performance of roof and U-rib welds in orthotropic steel bridge decks were studied by fatigue testing and finite element analysis simulation. Eight specimens of roof and U-rib welds were manufactured. The changes in weld geometry and microstructure after hammer peening were measured by the reverse mold and metallographic test. The effects of hammer peening on fatigue life were compared. Through the use of finite element models, the stress and deformation after hammer peening, and the effects of hammerhead radius and hammer depth were investigated; operational suggestions regarding hammer peening were also proposed. The results indicated that hammer peening reduced the geometric mutation of welds and generated a stratiform microstructure near the surface. The fatigue life of roof and U-rib welds increased significantly after hammer peening. The influence depth of residual compressive stress induced by hammer peening increased as the hammerhead radius increased, while the maximum compressive stress decreased without changes to its distribution. The principal stress and influence depth of the applied compressive stress increased with increasing hammer depth as well. The Hammer peening parameters of a 4 mm hammerhead radius and a 0.5 mm hammer depth were suggested.

This study evaluates the behavior of fiber-reinforced asphalt mixtures using advanced material characterization and performance prediction models. The polymeric nature of the proprietary blend of polyolefin and aramid fibers used warrants examining the contribution of the fibers not only to the physical network of the mixture but also to the extent of modification of the asphalt binder upon mixing. The effect of adding these synthetic fibers on the performance of asphalt concrete mixtures is assessed in the state of compression to investigate the resistance to rutting by (1) using a viscoelastoplastic continuum damage (VEPCD) model to provide an accurate and realistic assessment, and (2) by conducting a mechanistic-empirical (ME) analysis using Pavement ME software because it is the state of practice in pavement design and analysis. Upon addition of fibers, the developed VEPCD models indicate an overall improvement in the performance in terms of predicted strain in response to a given stress profile. Fibers are found to impose a faster recovery of viscoelastic strains during rest periods and lower strains during loading when added to a warm mix asphalt (WMA) mix containing unmodified binder. Fibers are also found to reduce the viscoplastic strains of both hot mix asphalt (HMA) and WMA mixtures at 5°C and of HMA mixture at 35°C. The performance improvement due to fibers is enhanced when using fibers of shorter length, using fibers in mixtures with wax-based additives, or in mixtures with coarser gradations.

The difficulty of standardizing the test conditions for the contact angle (CA) of a mineral powder (MP) leads to results with poor repeatability. To solve this issue, external factors that influence the CA test of a MP were investigated, and methods for controlling these factors are proposed. According to the test results, the compactness of the powder column impacts the discreteness of the MP CA remarkably in such a way that more stable compactness results in a more discrete CA. Furthermore, the number of layers and height of filter papers wrapped around the bottom of the glass tube and the selection of liquids with known surface-energy parameters impact the CA measurement of the MP directly, particularly for MPs with larger grains. More layers of wrapped filter paper are needed when MPs with larger grains are tested. The top of the filter papers wrapped around the bottom of the glass tube must be higher than the liquid level. Polar liquids with zero dispersive component of the surface-energy parameter should be selected to test MPs with larger grains.

It is of importance to study the dynamic flexural tensile fracture behavior of pervious pavement concrete under static preloading. In this study, semicircular pervious concrete specimens with pre-cracks were subjected to static bending tests at different preloading levels and then loaded by dynamic bending tests at different loading rates. According to the experimental results, as the loading rate increases under the same preloads, both the total fracture toughness and the dynamic fracture toughness increase. However, when the loading rate remains unchanged, the total fracture toughness increases as static preloading level increases while the dynamic fracture toughness decreases. In addition, the dynamic fracture toughness increase factor is defined as the ratio of dynamic fracture toughness to static fracture toughness. In order to consider the effects of static preloading levels and loading rates on the dynamic fracture toughness of pervious concrete, the dynamic fracture toughness increase factor model was proposed. The fitting results show good agreement with test data.

Engineering behavior of fine-grained porous media, predominantly encountered in dredged sediments from ports, tailings from mining operations, and geoenvironmental barrier systems, are dictated by their microstructural parameters. As such, alteration in pore fluid chemistry induces changes in the fabric of fine-grained soils, which contributes to a modified geoengineering response. The present study assessed pore fluid salinity effects on gradational and index properties, linear volume change, and free swell behavior of a reference fine-grained geomaterial, kaolin. Flocculation of kaolin in saline pore fluids and subsequent changes in some of its properties are discussed in this paper. Furthermore, for studies involving geomaterials with saline pore fluids, differences arising out of results reported with reference to three-phased (soil solid–water–air) and four-phased (soil solid–salt–water–air) idealizations are also highlighted.

This research investigated the effect of lime treatment on the static liquefaction behavior of sand–bentonite (SB) mixture by conducting a series of undrained monotonic triaxial compression tests. The effects of two bentonite contents (i.e., 0% and 10%), four lime contents (i.e., 0%, 3%, 5%, and 7%), and three initial relative densities (10%, 20%, and 30%) under an effective confining stress of 150 kPa were investigated. The results showed that lime treatment is effective in improving the static liquefaction strength of the tested specimens. In addition, lime treatment changed the SB liquefaction behavior from limited liquefaction to nonflow.

Morphological characteristics of aggregates have been regarded as a significant factor related to the high-temperature performance of asphalt mixtures. Fractal theory was used to calculate the fractal dimension to evaluate the morphological characteristics of aggregates. Dynamic creep test was selected to estimate the high-temperature performance of asphalt mixtures in terms of gradation types, nominal maximum aggregates sizes (NMAS), asphalt binders, and gyration levels. For each of these factors, correlation analysis between high-temperature indicators and fractal dimension was conducted. The results indicate that the flow number (FN) Index, that is, the ratio of maximum microstrain to flow number, is well-correlated with the fractal dimensions of asphalt mixtures in terms of gradation types and NMAS. Strain rate was a more comprehensive indicator linked with the morphologies of aggregates. According to fractal analysis, the specimen of AC-13 revealed optimal high-temperature resistance in terms of morphology. The AC-13 mixture with 75 gyrations had the largest value of fractal dimension and exhibited the best high-temperature performance. In addition, fractal dimensions measured by box-counting and sandbox methods were well-correlated with indicators of high-temperature ability; box-counting presented advantages for computing the fractal dimension of asphalt mixture.

The influence of refractory gravel amount and thermal resistance performance on a stone mastic asphalt-13 (SMA-13) road was studied through an indoor simulated light test. Thermal resistance friction course-13 (TRFC-13) was developed, and its antirutting performance was evaluated. The simulated illumination time should be 3 h when the surface temperature of an ordinary SMA rut board can reach 75°C, thereby corresponding to an extreme temperature of 41°C in summer. The replacement of single- and two-stage aggregates was explored. In comprehensive thermal resistance, road, and economic performances, 4.75–9.5 mm refractory gravel is recommended to replace the same particle size of 60% ordinary aggregate. The dynamic stability of TRFC-13 can be increased by 1.23, 1.56, 2.14, and 3.55 times at 38°C, 39°C, 40°C, and 41°C, respectively, compared with ordinary SMA-13. The low temperature and water stability satisfy the specification requirements.

Concrete undergoing volumetric changes is likely to be met with sustained restraint. This restraint leads to stresses which are reduced by tensile relaxation, in turn enabling the mitigation of cracks. Although creep and relaxation are said to be related, creep is well understood, while relaxation is not. In addition, relaxation is predicted from creep values because of the difficulty involved in performing relaxation experiments. This study validates approximate relaxation prediction models by comparing predicted values with experimental results. Two related methods are used: the effective modulus method and the age-adjusted effective modulus method (AAEM). Results indicate that using approximate relaxation models to predict early-age relaxation is valid. The accuracy of prediction increases as ultimate relaxation is reached, i.e., after 72 h for both the effective modulus method and the AAEM. No improvements in predictions are observed when the AAEM is used. The nature of load application does not seem to influence predictions.