Journal of Materials in Civil Engineering

Dynamic modulus of asphalt mixtures is one of the most important input parameters in design and rehabilitation of asphalt pavements. Dynamic modulus predictive models are alternative methods for laboratory determination of this parameter. These models were developed based on laboratory data. Due to sophisticated and laborious laboratory testing methods, there is a need to develop new models to determine dynamic moduli of in-service asphalt layers. In this study, nine different asphalt pavement sites were selected in two southern provinces of Iran. Falling weight deflectometer (FWD) testing was performed at each site and core samples were taken from the asphalt layers for volumetric analysis. Using the results, dynamic moduli of asphalt layers were determined using six predictive models, including Witczak, modified Witczak, Hirsch, Al-Khateeb, global, and simplified global models. Predicted dynamic moduli were compared with those determined from back-calculation analysis of FWD data. Existing predictive models were calibrated and new models were developed for the prediction of in situ dynamic modulus of asphalt layers in hot climate areas. Performance evaluation and validation of the new models showed high prediction accuracy and low prediction bias with very good correlations between the predicted and back-calculated values ($R^2=0.96$).

Engineered cementitious composites (ECC) possess outstanding mechanical properties which make them suitable for construction and repair applications. However, the high cost and limited supply of the special silica sand used as the only aggregate in ECC have limited its widespread use. A recent study has shown that recycled concrete fines can be used as a replacement for conventional sand in ECC without much detrimental effect on its mechanical properties. However, the corresponding effect of the recycled concrete as an aggregate on the durability of ECC is unknown. Therefore, this study was carried out to investigate the durability properties of ECC mixtures incorporating recycled concrete fines as aggregates. The durability of the mixtures was assessed in terms of shrinkage and permeability properties as these are very critical to its applications. This study showed that the use of recycled concrete as aggregate up to 100% replacement of the silica sand resulted in about a 40% reduction in drying shrinkage. However, chloride ion penetration, permeable voids, and water absorption of ECC mixtures incorporating 100% recycled concrete as aggregate increased by 19%, 28%, and 34%, respectively. Sustainability and cost assessments of the ECC mixtures indicate that the use of RC as aggregate in ECC mixtures is sustainable and economical.

The moisture damage on a bituminous road in tropical regions are proliferated only at the weakest aggregate-bitumen interfaces by adverse weathering conditions and propagates for the vehicular overloading condition. Therefore, an evaluation of the moisture damage resistance potency of hot mix asphalt (HMA) modified with different waste plastic fractions was considered as the state-of-art in this investigation. Fourier transform infrared (FTIR) spectroscopy, force spectroscopy using an atomic force microscope (AFM), modified Marshall immersion, and indirect tensile strength test methods were adopted to conduct this study. Study outcomes explored that 1% of different plastic waste fractions comprised of 2(PB): 0.25(PMP): 1(PC) to the HMA in a wet process indicated the highest moisture damage resistive potential due to the existence of strong nitrogenous chemical fraction. Hence, such a combination of plastic waste fraction may be used as an effective moisture resistive bitumen modifier to make a durable bituminous mix used in the wearing course of flexible pavements.

The available models for estimating the creep strains of concrete generally assume concrete as a homogeneous material. Since concrete is a composite, such models cannot take into account incompatible strains between cement paste and aggregates during creep loading. The main objective of this paper is to demonstrate that initial defects could increase the creep strain level and justify the application of a coupling between creep and damage at the macroscopic scale. To do so, different contents of air-entraining agent were used to simulate the internal defects of concrete and high-stress continuous load was applied to concrete samples with different initial defects. By analyzing the stress-strain curves of concretes containing different initial defects after compression, it was concluded that the existence of internal defects had a significant effect on the basic mechanical properties of concrete samples. Acoustic emission technology was used to obtain the internal acoustic emission response of concrete samples under high stress. Creep development rate is nonlinear to load holding level based on the analysis of experimental data and internal structure of concrete samples.

Rutting, one of the main failures in flexible pavements, is the result of permanent deformation aggregation in pavement layers under traffic loading. Rutting decreases the life of the pavement, and, by influencing control properties of vehicles, creates serious dangers for road users. Therefore, it is very important to predict the rutting potential of different types of asphalt mixtures (before construction and operation) based on the characteristics of the mixture ingredients (bitumen and aggregate), environmental conditions, and traffic loads. This study used genetic programming to represent flow number results of different asphalt mixtures. The models presented predict the flow number (as an index of rutting potential) based on parameters such as the index of aggregate particle shape and texture (particle index), bitumen rutting parameter ($G^{*}/\sin \delta$), and the stress level. Experimental data were collected from studies conducted on materials (gradation, dynamic shear rheometer, and particle index) and dynamic creep tests of asphalt samples at different levels of stress and temperature. The genetic programming models were compared with a multiple linear regression model. The results demonstrated that the genetic programming model predicted the flow number of asphalt mixtures with better accuracy rather than the regression model. The results of statistical studies revealed that three parameters, particle index, rutting potential, and stress level, influence the flow number, and the stress level is the most significant parameter.

It is widely known that concrete structures in cold and humid environments usually suffer frost damage and thus deteriorate faster, especially those structures without using air-entraining agents and with exposure to excessive moisture. Most available research on concrete under a freezing environment could be roughly categorized into: (1) intact concrete under freezing temperature where the ice-strengthening effect in pores was predominant; and (2) frost-damaged under room temperature where the damaging effect because of mesocracks was predominant. In fact, once the mesocracks of frost-damaged concrete are filled with water and the water freezes into ice under low temperature, the ice could provide an extra strengthening effect to the porous skeleton of concrete materials. In other words, both strengthening and damaging effect exist for frost-damaged concrete under freezing temperature. Specifically, it is of great importance to clarify such ice-strengthening effects in mesocracks so that the mechanical performances of the frost-damaged concrete under freezing temperature could be further studied. As the first step, the fully saturated case is the focus to develop rational and reliable models for further exploration and extension to the partially saturated case. In this paper, the authors develop comprehensive multiscale models that consider the damaging effect of ice formation on concrete as well as the strengthening effect of ice-filled pores and ice-filled mesocracks. The developed models are implemented into a discrete numerical application, then rigid body and spring model simulations are conducted. Experiments including uniaxial compression and splitting tension of concrete specimens are also executed to demonstrate the ice-strengthening phenomenon in mesocracks’ proposed models as well as the simulations by the developed program.

Geopolymer composite is an innovative and ecofriendly construction material and an alternative to portland cement. Geopolymer concrete is a multifunction material that can be used for different purposes. One of the applications that recently has attracted attention is in snowproof roadways. This paper studied the compressive strength and stiffness of fly ash–based geopolymer with different volume percentages of $0.5\text{-}\mathrm{in.}$-long (12.7 mm) steel-fiber reinforcement at different curing conditions. The formed geopolymer concrete was analyzed through compression testing, scanning electron microscopy (SEM) microstructural analysis, and measurement of electrical conductivity. The results showed that the fly ash–based geopolymer mortar can greatly improve the compressive strength and electrical conductivity by using a small amount of steel fibers. Curing at elevated temperatures for the first $24\mathrm{h}$ increased the geoploymer’s strength and stiffness. With improved mechanical properties and electrical conductivity, the developed geopolymer concrete could be used as a pavement material for snowproof roadways. Improved electrical conductivity can increase the heat generated in geopolymer through electricity and help to accelerate snow melting. Steel-fiber reinforcement enhances the geopolymer’s stiffness and strength and makes the geopolymer material satisfactory for the construction requirements for pavements.

This study reports the effect of fine sand addition on the properties of fired clay bricks. Fine sand was sieved to $-75\mathrm{\mu m}$ and incorporated at varied weight proportions (5, 10, 15, 20, 25, 30, 35, and 40 wt.%) to clay in the preparation of fired bricks. The samples produced were oven dried at 110°C for 12 h, and fired at a temperature of 1,200°C in an electric furnace. The samples were examined for physical, thermal, and mechanical properties. Result of the tests showed a reduction in porosity, water absorption, weight loss, and firing shrinkage with increasing sand addition, although the bulk density increased as the percentage weight content of sand increased. Thermal properties such as thermal conductivity, thermal diffusivity, and thermal emissivity increased with fine sand addition while reduction in coefficient of thermal expansion and specific heat capacity was observed. Also, the thermal shock resistance improved with increase in fine sand addition up to 25 wt.%, before further decline was observed. The hardness and impact value were enhanced with increasing additives. It is noted that samples immersed in rainwater were found to experience depreciation in hardness, resistance to impact, compressive and flexural strengths as the number of days of immersion increased. It was concluded that bricks produced are good for building in temperate region in which much flooding is not experienced.

In this research study, the stability of a hydraulic fill dam located in a newly declared seismically hazardous zone in north Texas was evaluated, incorporating the effect of geomaterial variability existing in the dam. Hydraulic fill dams exhibit highly variable geomaterial conditions due to the method of construction and are prone to stability issues during earthquakes. Hence, a comprehensive study was needed to account for such variations in geomaterial properties and assess the stability of the dam rather than performing routine analysis using representative geomaterial properties for the shell, core, and foundation of the dam. Cone penetration tests were performed on the dam to study geomaterial properties and their variabilities. These results were used to develop three-dimensional (3D) visualization models using kriging analysis. The geomaterial properties obtained from the visualization models were subsequently used in the slope stability analyses. The developed visualization models depicted the variation of geomaterial properties within the dam. The use of the visualization models has led to the development of an innovative approach for performing stability analyses of earthen dams with high geomaterial variability.

Geopolymer concrete is a sustainable material which can reuse industrial by-products and thereby minimize the emission of greenhouse gases during its production, unlike cement. Blended geopolymer concrete has been made from two industrial waste products, ground granulated blast furnace slag (GGBS) and dolomite, which are obtained from steel industries and rock crushing plants, respectively. This geopolymer concrete is found to develop high strength within a short period of ambient curing. It is observed that the addition of steel fibers enhances the strength and durability characteristics of this concrete. The paper highlights the engineering and durability properties of steel fiber–reinforced GGBS-dolomite geopolymer concrete and explains how the bond strength and impact resistance of GGBS-dolomite geopolymer concrete is improved by the inclusion of steel fibers. A comparison of improvement in durability characteristics between geopolymer concrete with and without steel fiber reinforcement and ordinary portland cement concrete is also presented. The development of GGBS-dolomite geopolymer concrete from industrial by-products minimizes the cost of construction and creates a solution to the waste disposal problems. The high durability of geopolymer concrete will help to reduce the maintenance cost of structures.

Concrete is considered an isotropic material for structural analysis and design purposes. However, during concrete placement and compaction, segregation and bleeding may occur. A water film is deposited around larger aggregate particles, especially on the bottom surface. This effect was already identified in the literature as a cause of anisotropy in compression strength, but there is no evidence of anisotropy of concrete in terms of elastic constants. In this paper, impact acoustics and ultrasound measurements were used to measure dynamic elastic properties in prismatic specimens ($125\times 125\times 400\mathrm{mm}$). The specimens were produced with two directions of concrete placement and compaction: longitudinal and transversal. Three concrete batches were produced with high, medium, and low percentages of cement. Five identical specimens were produced for each combination of concrete mix and direction of concrete placement. A pattern of anisotropy was identified for all specimens through natural frequencies of the specimens and measured ultrasonic wave velocities. Although this effect is small, it could be clearly identified by impact acoustics and ultrasonic tests.

A durable, high-performance concrete is important for sustainable construction. Organic admixtures, a fair contender against its traditional chemical counterpart, is being explored in response to the renewed interest in the production of green concrete. In this study, two types of starch, i.e., laboratory starch and arrowroot, were used as admixtures and their effects on different properties of cement paste and mortar were observed. Starch showed a considerable retarding effect without adversely impacting the compressive strength. Also, it increased the flow of cement mortar substantially. The mortar samples with starch also exhibited a reduction in water absorption. A small amount of starch admixture, ranging from 0.5% to 2.5% of cement content by weight, has been found to increase the flowability and setting time of cement mortar keeping the strength, durability, and shrinkage parameters within an acceptable range. Within the scope of this study, 1%–1.5% starch addition by weight of cement exhibited improved performance in terms of setting time and flow.

This study aimed to investigate the use of polymeric end-of-waste materials, including polyethylene-terephthalate (PET) and other plastic types that have not been comprehensively studied to date, namely, acrylonitrile-butadiene-styrene (ABS), polycarbonate (PC), ABS/PC blend, and polyoxymethylene (POM), to improve the durability of cement mortars. The evaluation of freeze-thaw and salt-crystallization resistance and endurance to cyclic changes in moisture and temperature for plastic aggregate (PA) mortars was carried out by measuring mass loss, compressive strength loss, and macroscopic damage following accelerated weathering testing. The PA mortars were prepared by replacing natural sand (5%, 15%, and 20% by volume) with PAs. The results show that PA mortars are more susceptible to thermal/moisture variations and salt crystallization than to frost action, with 4%–7% mass loss and up to a 31% reduction in strength. The damage caused by frost action is insignificant for plastic aggregate mortars, especially at low replacement levels. The damage to mortars done by salt attacks and moisture/thermal changes could be due to the dimensional instability of the PAs because their thermal expansion coefficients are well over those of the minerals with which they are mixed. The compressive strength of the PA mortars, even after weathering, is well above the minimum strength required for structural lightweight concrete.

High performance Chinese domestic structural steel (referred to as GJ steel) has been applied to many major construction projects due to its high performance, high yield strength, and good mechanical properties. In this paper, the variations of the static and low cyclic performances of Q460GJC thick plates at different layers in the transverse and $Z$-direction (along the plate thickness) are described and discussed. Static performance tests under monotonic tensile loading were conducted on the transverse and $Z$-direction specimens of 25-, 42-, and 80-mm thick steel plates to obtain the stress-strain curve, yield strength, tensile strength, elongation, and reduction of the cross-sectional area after fracture of each specimen. Low cyclic performance tests under equal-strain increase and equal-strain amplitude loading were also conducted on the transverse and $Z$-direction specimens of 80-mm thick steel plates to obtain the cyclic hysteresis curve, skeleton curve, cyclic strength, and cyclic hardening degree for each specimen. The main findings from this study are the following: (1) the closer the material is to the outer surface of the Q460GJC thick plates, the higher the yield strength and the better the ductility; (2) the yield strength and the reduction in the area of the transverse specimens are higher than those of the $Z$-direction specimens at the same layer; (3) Q460GJC thick plates have good seismic performance in both transverse and $Z$-directions at different plate layers; and (4) the closer the material is to the outer surface, the higher the cyclic strength.

Hydraulic conductivity of polyanionic cellulose (PAC)–amended bentonite (PB) in calcium chloride (${\mathrm{CaCl}}_2$) solutions was investigated to access its chemical compatibility in vertical cutoff walls application. PB was synthesized by mixing conventional bentonite (CB) powder with PAC (2% dry weight). The specific gravity ($G_s$), liquid limit ($w_L$), pH, swell index (SI), and cation exchange capacity (CEC) of CB and PB were measured, and hydraulic conductivities and microstructures of the PB and CB filter cakes were evaluated by performing modified fluid loss (MFL) tests and scanning electron microscopy–energy dispersive spectroscopy (SEM-EDS) analyses, respectively. The results showed that PB had higher $w_L$, SI, and CEC but lower $G_s$ and pH than CB; in particular, PB possessed higher SI in ${\mathrm{CaCl}}_2$ solution as compared to CB. Increase in the applied overall pressure and decrease in the ${\mathrm{CaCl}}_2$ concentration resulted in a decreased hydraulic conductivity for both PB and CB. However, the hydraulic conductivity of PB was found to be one to two orders of magnitude lower than that of CB when exposed to the same ${\mathrm{CaCl}}_2$ solutions, indicating superior chemical compatibility of PB. SEM-EDS image analyses demonstrated that polymer formed a three-dimensional net structure between bentonite particles, which could clog the intergranular pore space, resulting in a narrow and tortuous flow path for liquid and low hydraulic conductivity.

Experimental investigations were carried out on the thermal and mechanical properties of sleeve grouting materials subjected to elevated temperatures up to 900°C. The thermal properties, including thermal conductivity, specific heat, and thermal expansion, as well as the temperature-dependent compressive strength were obtained from the experiments. Simple calculation methods were proposed to predict the thermal properties and strength of the material subjected to elevated temperatures. The experimental results showed that the thermal conductivity and the compressive strength of the materials decreased while the heat capacity and thermal strain increased with the increase of temperature. Degradation of the sleeve grouting materials under elevated temperatures was investigated through microanalytical tests.

In this study, we evaluate the flame-retardant properties of styrene-butadiene-styrene (SBS)/layered double hydroxide (LDH-) –modified asphalt. We performed physical tests, dynamic shear rheological tests, and limit oxygen index measurements to evaluate basic physical properties as well as rheological and flame-retardant properties of SBS/LDH-modified asphalt samples. Fourier transform infrared spectrometry and fluorescence microscopy were performed to elucidate the mechanism reaction between LDH and SBS-modified asphalt. In addition, a novel flame-retardant analyzer was developed and used to analyze the changes in mass and temperature during asphalt combustion. Kinetics analysis and thermogravimetry measurements were performed to determine the most probable mechanism and activation energy. The microstructure of the combustion residue was analyzed using scanning electron microscopy. The results indicate that LDH increases the viscosity of SBS-modified asphalt and its resistance to deformation at high temperatures. However, when added in high concentrations, it has a negative effect on asphalt ductility. The $|G^{*}|$, $G^{\prime }$, and $G^{″}$ values for the SBS-modified asphalt increase with the addition of LDH. However, the effect is not statistically significant over the entire investigated frequency range. Moreover, the addition of 5% LDH reduces the phase angle of SBS-modified asphalt for frequencies greater than 30 Hz. Also, its effect is not statistically significant over the entire investigated temperature range. LDH increases the nonflammable grade and activation energy of SBS-modified asphalt and results in the formation of denser char, which significantly improves its flame-retardant properties.

Microbial-induced carbonate precipitation (MICP) is an innovative ground improvement technique that utilizes bacteria to induce calcium carbonate precipitation to cement soil particles. In this paper, the interface strength between calcareous sand and steel was improved using the MICP process. The interface shear behavior between MICP-treated calcareous sand and steel was investigated experimentally under different cementation levels and normal stresses. With the increase of ${\mathrm{CaCO}}_3$ content, the peak shear strength increased, accompanied by obvious volume dilation, and the corresponding shear displacement was reduced. The shear band thickness was suppressed greatly from $22.2d_{50}$ to $4.4d_{50}$, and the percentage interface slip increased from 77.8% to 95.7%. With the increase of normal stress, the thickness of shear band increased and then remained stable. Both the peak and mobilized strength at 5 mm increased. MICP products changed the interface morphology and led to shear dilation of the sand sample, especially for high cementation levels. However, if the normal stress is large enough, the raised edges on the interface will be cut off and obvious contraction in the local layer near the interface appears. MICP cementation was found to have a remarkable effect on improving the cohesion of the calcareous sand–steel interface according to the Coulomb criterion.

Recycled concrete self-insulating blocks (RCSBs) are an economic and environmentally friendly load-bearing building material that can save energy. In China, there is almost no systematic evaluations focusing on the shear performance of RCSB walls. To realize the effective utilization of RCSB, this paper makes a series of experimental research and theoretical analysis on the shear performance of 72 standard RCSB wall specimens. The key factors such as shear failure characteristics, shear strength calculation formula, and shear compression failure criterion are analyzed. The test results show that the shear strength of RCSB walls is higher than that of ordinary concrete block wall. Recommended formulas for the shear strength of RCSB walls are given, taking into account the actual situation, and having certain safety and reliability. The measured shear-pressure correlation curve of RCSB walls is given, including three modes of shear-friction, shear-compression, and diagonal compression. Additionally, an elastoplastic finite element analysis of RCSB walls is performed by separating the block model from the mortar model by using ABAQUS, which can accurately simulate the shear behavior of RCSB walls.

The intrusion of moisture into asphalt pavements affects the cohesion and adhesion properties, which in turn, can lead to several durability- and integrity-related problems, such as potholes and stripping, as well as several types of other distresses, such as fatigue cracking and rutting. The use of antistripping additives is one of the most commonly used techniques to enhance the resistance of asphalt pavements to moisture damage. In this research, the effects of five different types of antistripping additives (i.e., Zycotherm, WETMUL-950, GRIPPER L, Evonik, and TeraGrip) on the moisture resistance of asphalt pavements were evaluated and compared with each other. For this purpose, two series of experimental methods were used: (1) the surface free energy (SFE) to evaluate the adhesion and cohesion properties of the asphalt binders and aggregates, and (2) the indirect tensile stress (ITS) and resilient modulus tests to investigate the moisture susceptibility of asphalt mixtures. The results of the laboratory evaluation showed that all the additives used in this study improved the adhesion and cohesion properties and increased the resistance of the asphalt mixtures to moisture susceptibility. The asphalt mixtures containing Zycotherm and WETMUL-950 showed the highest resistance to moisture damage among all the additives studied in this research.

Self-compacting rubberized concrete (SCRC), as the primary material of road construction, is produced by adding rubber particles instead of sand to self-compacting concrete (SCC). Four kinds of concrete with different rubber contents (0%, 5%, 10%, and 15%) are tested in this study. The materials testing systems (MTS) and split Hopkinson pressure bar (SHPB) are employed to obtain quasi-static mechanical properties (compressive, splitting tensile, and bending) and dynamic mechanical properties at high strain rates ($100–250{\mathrm{s}}^{-1}$). The results reveal that quasi-static mechanical strength decreases with the increase in rubber content. Compared with SCC, SCRC is dramatically high in ductility. With the increase of the strain rate, the dynamic compressive strength, peak toughness, specific energy absorption (SEA), and dynamic increase factors (DIF) all rise. The dynamic compressive strength decreases with the ascending of rubber content, while the toughness index, peak toughness, and SEA increase with the increasing rubber content. Exponential and linear fittings are utilized to help further understand the influence of strain rates. The craze-shear band-cavitation theory can also help well explain the transition strain rate of peak toughness curves. The failure modes under high strain rates are observed. The results reveal that SCRC exhibits a stronger sensitivity to rubber content and has better impact toughness than SCC.

This paper calls attention to important issues that have not been considered regarding linear amplitude sweep (LAS) test in previous publications: Is the relationship between the storage modulus logarithm [$\log G^{\prime }(\omega )$] and frequency logarithm [$\log (\omega )$] linear in the whole range of experimental frequencies? If not, what is the influence on the fatigue life of asphalt binders calculated using the AASHTO protocol? In which range of frequencies is the relation between the storage modulus logarithm [$\log G^{\prime }(\omega )$] and frequency logarithm [$\log (\omega )$] linear in the whole range of experimental frequencies? Does fatigue life follow a normal distribution? Several tests were conducted using three different types of asphalt binder [neat, crumb rubber–modified (CRM), and styrene–butadiene–styrene (SBS)–modified asphalt]. Residual analysis showed a lack of fit, indicating the inadequacy of the linear model in the whole range of experimental frequencies. This inadequacy may suggest that the protocol produces an overestimation of the binder fatigue life. In addition, a sequential search reveals that the relationship between $\log G^{\prime }(\omega )$ and $\log (\omega )$ is linear in a limited subset of frequencies. The empirical distribution of the fatigue life is built by an extensive Monte Carlo simulation.

Self-compacting lightweight aggregate concrete (SCLC) has attracted growing attention because of its self-compacting performance and good workability, thus the mechanical properties of SCLC and the structural performances of RC components made of SCLC have been widely studied. However, the bond behavior of deformed bars in SCLC at early ages has not been reported, which has hindered the application of this high-potential concrete. Therefore, in this study, a comprehensive experiment was conducted to investigate the bond behavior of deformed bars in SCLC at early ages, which involved a total of 135 pull-out specimens with different concrete strengths, bar diameters, and curing ages. Based on the experimental results, a criterion is proposed for determining whether the bond failure mode is the pull-out failure or the splitting failure. That is, for a given curing age, when the value of the ratio of the compressive-to-tensile strength is less than or equal to its critical value, which is related to the relative concrete protection thickness and the 28-day compressive strength of SCLC, the pull-out failure occurs, otherwise, the splitting failure occurs. On this basis, the calculation models for the bond parameters including the ultimate and residual bond strength and the slip at the ultimate bond stress, as well as a bond stress-slip constitutive relationship are proposed, which are in reasonable agreement with the experimental results. According to the results of this study, the bond characteristics of deformed bars in SCLC at early ages can be predicted well with only a measurement of the compressive strength of SCLC at 28 days, which are useful in assessing the early load bearing capacity and deformation capacity of the reinforced concrete structures constructed with SCLC.

This study investigates the chemical characteristics of rejuvenators and the effect of different rejuvenators on the morphology and fundamental behavior of rejuvenated asphalt binders. Gas chromatography-mass spectroscopy (GC-MS) and atomic force microscopy (AFM) were conducted to determine the chemical composition of rejuvenators and asphalt surfaces’ morphology. Also, surface free energy (SFE) measurements were performed to quantify the cohesive bond energy of rejuvenated binders. The thin film oven test (TFOT)-aged performance graded (PG) 58-28 binder was rejuvenated with waste cooking oil (UT), chemically modified waste cooking oil (TR), and Hydrolene H90T (HL) at concentrations of 3%, 6%, and 9% by weight of the total binder. To understand the compatibility, styrene-butadiene-styrene (SBS) was also blended with rejuvenated binders. The experimental study found the variability of free fatty acid compositions in rejuvenators, which is hypothesized to affect pavement performance. Results showed that rejuvenation alters the surface microstructure of binders, which provides insights into the overall performance of the binder. Also, rejuvenation improves the moisture damage resistance of binders significantly. This experimental study found a good correlation between the chemical, morphological, and fundamental behavior of the rejuvenated binders, which is expected to help quantify the performance of rejuvenated asphalt mixes.

The thermal and mechanical properties of coarse aggregates, cement mortar, and cement concrete specimens of varying mix proportions were studied after exposure to a range of high temperatures. For the tests, 70.6-mm mortar cubes, concrete cubes of 100 and 150 mm, and concrete cylinders of 100 and 150 mm diameters and 200 and 300 mm heights, respectively, were cast. The water to binder ratio was varied from 0.35 to 0.5. These specimens were exposed to a wide range of temperatures varying from room temperature ($24°\mathrm{C}\pm 2°\mathrm{C}$) to 1,000°C and tested to understand the degradation in strength and spalling behavior of normal-strength concrete (NSC) and high-strength concrete (HSC). The crack initiation and propagation was studied using micrographs obtained from scanning electron microscopy (SEM). Changes in the porosity of coarse aggregates and concrete at elevated temperatures is quantified by incorporating digital image processing on the SEM micrographs. The influence of high temperature on the physical and chemical properties of concrete and concrete constituents at the macroscale and microscale are discussed. Simple empirical relationships to compute residual compressive strength of NSC and HSC at elevated temperatures are proposed. It is concluded from the results that the degradation in the concrete strength at high temperatures is primarily a result of nonuniform thermal expansion of concrete and its individual constituents leading to porosity changes in the cement–sand matrix, coarse aggregates, and interface between the two.

The preparation of high-performance equal-sized–aggregate (HPESA) concrete has reversed current thinking about targets pertaining to high density and strength when designing traditional concrete materials. Maintaining the integrity of aggregates to prevent explosive failure at low strain, allowing use as an antiexplosion buffer filling layer in underground engineering works, is important. It is possible to repair the structures in situ after a disaster. Dynamic mechanical properties at different strain rates and obtaining optimal mix design parameters under impact loads were studied. According to the application requirement of antiexplosion buffer filling material in underground engineering, 16 groups of specimens were prepared with different mix designs. These were subjected to split Hopkinson bar (SHPB) testing at different impact-loading strain rates. The dynamic mechanical properties of HPESA concrete materials were correlated with impact-loading strain rates. At different strain rates, three types of stress–strain curves were exhibited: single-peak, double-peak, and transition types. The sensitivity of materials to strain rates was positively correlated with aggregate sizes. The energy dissipation of HPESA concrete materials under impact loading can be divided into damage fracture energy and inertial potential energy. The effects of four influencing factors (aggregate size, polymer–cement ratio, water–cement ratio, and cement–aggregate ratio) on energy dissipation in the specimens were explained theoretically. From the range analysis results of orthogonal tests, the primary and secondary order of the influencing factors on energy consumption indices was obtained, and the optimal energy-consumption ratio parameters of the material for antiexplosive buffer filling materials were determined, which lays a foundation for the subsequent application of this material.

Buffer/backfill material is an important part of engineered barriers in deep geological repositories of high-level radioactive waste (HLRW). A good buffer material not only possesses good heat conductivity, expansion, and sealing characteristics, but also exhibits enough strength. Its thermomechanical performance can significantly influence the safety and stability of a HLRW repository. Polypropylene fibers were mixed with bentonite-based mixtures (bentonite–sand–graphite) to form a buffer material with high strength, good heat dissipation capacity, and strong isolation capacities. The effects of fiber content, fiber length, and sand particle size on the shear strength, swelling pressure, and thermal conductivity of fiber–bentonite-based (BSGF) mixtures were analyzed under given graphite and sand contents. Detailed analyses of the shear, expansion, and heat transfer mechanisms of BSGF mixtures were performed to understand the behavior. The results indicated that the strength of BSGF material improved significantly with the addition of fiber content, whereas swelling potential and thermal conductivity were reduced. With an increase in sand particle size, cohesion and maximum swelling pressure decreased, whereas internal friction angle and thermal conductivity increased. The optimum fiber content, fiber length, and sand particle size were determined based on the thermomechanical performance of BSGF mixtures. These findings help in the field application of buffer materials with different fiber contents, fiber lengths, and sand particle sizes.

Many techniques, most notably soil stabilization, have been developed to enhance soil characteristics due to the growing trend of constructing structures on clayey soils. Therefore, it is imperative that researchers address clay-related issues utilizing geotechnical engineering achievements. This study evaluated the effect of volcanic ash (tuff) as a natural pozzolan on the improvement of cement performance in the clay stabilization. Various compositions of cement (0%–6% by dry mass) and tuff (0%–20% by dry mass) were added to clay and cured for 7 and 28 days. Then a set of tests, including modified Proctor, Atterberg limits, electrical conductivity (EC), pH, unconstrained compressive strength (UCS), California bearing ratio (CBR), wet-dry durability, and scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses, were performed on the untreated and treated samples. The secant modulus ($E_{50}$) was measured to evaluate the stiffness of the specimens. The data showed that the incorporation of tuff into the studied cement-stabilized clay considerably enhanced the mixture mechanical properties and substantially reduced the plasticity index of the samples. After a 28-day period, the samples containing 6% cement and 15% tuff, as the optimum mixture, had increases of the UCS and CBR values of approximately twice those containing 6% cement. Moreover, the inclusion of tuff into the cement–soil blends increased the durability of the samples. According to the SEM and XRD analysis, the addition of tuff to the samples containing cement caused the formation of more cementitious compounds and fully changed the soil structure. The findings indicate that the use of tuff can lead to improved cement performance in the stabilization process.

Time-dependent chloride diffusivity can reflect the chloride transport in concrete, which is greatly affected by different factors such as material composition and environment condition. In this paper, three tests with eight kinds of concrete in different exposure environments (two natural tidal environments and one artificial simulated environment) were designed, and the profile of free chloride concentration at different depths and exposure times were obtained. The apparent and instantaneous chloride diffusion coefficients were determined, and their time-dependent properties were analyzed. The differences between apparent and instantaneous chloride diffusion coefficients were discussed, and the corresponding influencing factors were analyzed. Results show that under the similar climate environments, water salinity is the main factor affecting the age reduction factors of apparent and instantaneous chloride diffusion coefficients of ordinary concrete, i.e., age reduction factors increase with water salinity. Besides, the artificial simulated environment with characteristics of high temperature and high humidity has a significant effect on the age reduction factor of the instantaneous chloride diffusion coefficient. Moreover, the difference between apparent and instantaneous chloride diffusion coefficients of ordinary concrete decreases gradually with the increasing water-cement (w/c) ratio and the addition of silica fume (SF), but increases when adding fly ash (FA) and basalt fiber (BF) into concrete. Temperature is the most important factor affecting the difference between apparent and instantaneous chloride diffusion coefficients, but the effect of exposure time is not significant.

In this study, the effect of aggregate segregation on the performance of hot mix asphalt was studied. The possible levels of aggregate segregation were arrived from the field core samples. Considering the level of segregation observed in the field, four levels of segregation that range from very fine to very coarse were simulated in the laboratory. Both production and paving segregation were simulated to explore the effect on asphalt mixture performance. Production segregation was imitated by sieving aggregates through 2.36 mm and batching in different proportions. Alternatively, a loose hot asphalt mixture was sieved on a 4.75-mm sieve and combined in different proportions to mimic paving segregation. The performance of segregated mixtures was evaluated in terms of moisture susceptibility, cracking resistance, fatigue life, raveling, and rutting resistance. The results of the investigations indicated that finer mixtures due to production segregation and coarser mixtures due to paving segregation were highly susceptible to moisture damage, raveling, and fatigue. In addition, the rutting potential for both production and paving segregation was higher for finer mixtures than coarser mixtures. The overall ranking of the performance parameters showed that finer mixtures resulting from production segregation had an inferior performance, whereas coarser mixtures resulting from paving segregation performed poorly relative to the control asphalt mixture.

In this study, the cyclic behavior of steel slag ballast materials mixed with tire-derived aggregate (TDA) is experimentally investigated. To this end, a series of ballast box tests are carried out to investigate the behavior of different mixtures of TDA-slag ballast materials with similar gradation to American Railway Engineering and Maintenance-of-Way Association (AREMA) 4. The TDA is mixed with the slag at different gradations and weight ratios to determine the optimum percentage. According to the test results, the settlement and damping ratio increase with the increase in the TDA percentage, whereas the breakage index and the stiffness of the ballast decrease. TDA of 10% by weight (16.5% by volume) is selected as the optimum percentage for the mixture based on the dynamic stiffness and damping ratio. The same set of tests were also performed on the punched TDA-slag ballast samples to study the effects of the TDA shape on the behavior of the ballast.

This study discusses the effect of utilizing coarse reclaimed asphalt pavement (RAP) aggregates as a replacement to natural coarse aggregates (NCAs) for the production of pervious concrete pavement (PCP) mixes. Coarse RAP (RC) aggregates were utilized in proportions of 0%, 25%, 50%, 75%, and 100%, respectively. It was observed that the porosity and permeability coefficient of the PCP mixes increases considerably as the RAP replacement level increases. Meanwhile, the incorporation of RC was also found to negatively affect the mechanical properties of the PCP mixes. However, the compressive and flexural strength values were noted to be well within the prescribed limits ($5–25\mathrm{MPa}$ and $1–3.2\mathrm{MPa}$) required for a PCP mixture. On the other hand, the incorporation of RC was observed to reduce the hardened density, resistance to abrasion, and resistance against aggressive environment of chlorides and sulfates. Therefore, in order to prepare a PCP mixture such that there exists a fine balance in various properties, it is recommended that RC up to 50% may be utilized as a replacement to NCA. In view of achieving maximum sustainability, RC up to 100% may be completely utilized for the production of PCP mixes provided a binary gradation is adopted. Utilization of RAP in preparation of pervious concrete pavement mix will not only resolve the issues related to clearance of an enormous amount of RAP dumps, but would go a long way in dealing with various other environmental and ecological impacts.

The ductile performance of engineered cementitious composite (ECC) mixtures allows them to have a better fatigue life compared to traditional concrete. In this work, the effects of mineral admixtures and the aggregate size on the fatigue performance of ECC under bending were experimentally investigated. In addition, the failure probabilities under fatigue loading were also determined using the Weibull distribution. Finally, in order to shorten the process of fatigue testing, a prediction method for the fatigue life of ECC mixtures was proposed. It was found out that the use of ground granulated blast furnace slag instead of fly ash and the use of a larger aggregate size reduced the fatigue life of the original ECC mixture (ECC-M45). Moreover, the fatigue life estimated using the proposed method was in a good agreement with the experimentally-determined ones.

Despite the recent efforts in characterizing and investigating the dynamic properties of tire-derived aggregates (TDA) and its use in civil engineering applications, the size of TDA used in most of the previous work was significantly smaller than the TDA size range mentioned in ASTM D6270 standards. There are two types of TDA, Type A and Type B, in which the maximum aggregate size of Types A and B are 200 and 450 mm, respectively. Thus, the availability of experimental data and shear modulus reduction curves for the dynamic behavior of TDA of larger sizes are deemed necessary for practical engineers to assess and investigate the behavior of such material under dynamic loads. This paper provides the results of large-scale undrained cyclic triaxial tests performed on Type A TDA at large strain amplitudes. The tests were performed under confining pressures ranging from 25 to 200 kPa and shear strain levels ranging from 0.1% to 10%. Furthermore, each test consisted of successive stages in which the number of cycles and axial strain levels varied. The shear modulus of Type A TDA has a range of 245–1,796 kPa, with a decreasing trend with increasing shear strain amplitudes. Furthermore, the dampening ratios were found to range from 11% to 23.5%. Finally, the shear modulus reduction curves were obtained through curve fitting techniques and nonlinear regression.

The safe disposal of waste tires has been seen as having a negative impact on the environment. To mitigate this impact, the components of waste tires can be used in the production of green concrete. This study explores the effects of the curing and drying regime on the mechanical properties and permeation characteristics of concrete containing both crumbed rubber and steel fibers that are removed from waste tires. Five concrete mixes were designed, and concrete cubes, cylinders, and prisms were cast using waste tires extracts. Crumb rubber was treated by submersion in sodium hydroxide and then used to partially replace 10% and 30% of fine aggregates in the concrete mix. Extracted steel fibers were added at the rate of 1% and 2% per volume of each mix. Compressive and indirect splitting tensile as well as flexural strengths were conducted after normal curing while observing several drying conditions. Additionally, air permeability was assessed using a portable apparatus that was developed to assess permeability easily. For the concrete test specimens containing 10% partial replacement of fine aggregate by crumb rubber and 1% steel fibers, it was discovered that the splitting tensile strength and flexural strength were higher than that of the control mix by 21% and 22.6%, respectively. For specimens that included the 10% crumb rubber and 1% steel fibers, when exposed to oven drying at 105°C for 12 h, the compressive strength results increased by 17% compared with the control specimens exposed to the same conditions. Unlike the compressive strength results, the splitting tensile and flexural strength results decreased after exposing the specimens to elevated temperature. The addition of crumb rubber and steel fibers as a partial fine-aggregate replacement resulted in increasing the air permeability of the concrete to different degrees depending on the percentages used. The oven-drying curing regime improved the permeability by reducing it in specimens containing the 10% crumb rubber and 1% steel fibers as indicated by increasing their permeability time index by 15% when compared with air-dried specimens. Using waste tire extracts as a partial replacement of concrete fine aggregate can be recommended for both indoor and outdoor applications. This study showed that this was a viable, economic, and environmentally friendly method for reducing carbon footprint.

The aim of this study is to develop a time-dependent model for determining the chloride binding capacity of concrete with crystalline material (CM) with different water to binder ($\mathrm{w}/\mathrm{b}$) ratios, fly ash replacement proportions, curing times, and chloride exposure periods. The effect of CM on chemical and physical binding processes was considered in the development of the model. The model was developed based on the results of experimental analysis conducted by the authors. The values of chloride binding capacity predicted using the model fell within the R-squared values ranged from 0.842 to 0.982, which indicates satisfactory agreement with the experimental results.

Through the process of extracting iron from iron ore, a by-product is generated known as granulated blast furnace slag (GBFS). Traditional stabilization methods such as cement stabilization are not entirely sustainable options. This research investigates the engineering properties of geopolymer-stabilized GBFS and their viability for usage as a construction material. A combination of sodium hydroxide (NaOH) and sodium silicate (${\mathrm{Na}}_2{\mathrm{SiO}}_3$) was used as the liquid alkaline activator (L) along with low-carbon pozzolanic binders, namely, fly ash (FA) and slag (S). The L was prepared with a ${\mathrm{Na}}_2{\mathrm{SiO}}_3:\mathrm{NaOH}$ ratio of $70:30$ and binders were added up to 30%. The effect of different curing regimes on the strength of geopolymerized GBFS was evaluated using scanning electron microscopy (SEM) and unconfined compressive strength (UCS) tests. The effect of both the temperature and duration of curing had a vital role in the strength development of the mixtures. The test results indicated that the combination of $\mathrm{FA}+\mathrm{S}$ as a geopolymer binder could perform better than FA or S alone. With the lowest UCS value of 7.8 MPa and highest value of 43 MPa, all the geopolymer-stabilized GBFS were found to be suitable for a variety of civil and construction applications.

The construction of the future is moving in the direction of environmentally friendly materials and the use of various types of industrial byproducts and wastes. The use of blast furnace slag (BFS) for the production of concrete is one of those alternatives. In this study, pastes and concretes based on high-MgO BFS were alkali activated with 10% by weight sodium carbonate, sodium silicate, and a combination of both. Heat treatment and laboratory curing were applied. The results showed that heat treatment was effective at reducing the drying shrinkage of alkali-activated slag concretes and promoting high early strength. However, the sodium carbonate–activated slag concrete specimens showed a reduction in compressive strength at later ages. All concrete specimens tested exhibited high drying shrinkage; the highest values were for sodium silicate–activated concretes and the lowest were for sodium carbonate–activated concretes. All concretes tested showed very large creep, which was partly related to the small maximum aggregate size (8 mm) and the effects of carbonation. The carbonation depth after $12–24\mathrm{months}$ was significantly smaller for the heat-treated specimens and for concrete activated with sodium silicate. The carbonation process resulted in a more porous binder matrix, leading to long-term strength loss and increased creep, especially for sodium silicate–activated mixes.

Embedment strength is an important parameter that governs the ductile load-carrying capacity of timber joints with dowel-type fasteners. This property is dependent upon several factors, especially on the surface conditions of fasteners. In current design standards, however, the embedment strength depends only on the timber density and the diameter of fastener, though the surface conditions of dowels and fully threaded bolts are different. In this study, embedment tests for dowels, fully threaded bolts and glued-in rods in the direction parallel to the grain were carried out. Comparisons with the existing design equations in Eurocode 5 Design of Timber Structures (EC5) and American National Design Specification (NDS) were performed. It is found that the embedment strength in timber for dowels can be accurately predicted by EC5 and NDS, while the embedment strength for fully threaded bolts is underestimated. In addition, the embedment strength for glued-in rods is not addressed in the current design standards. Based on the presented experimental results, new empirical expressions for the embedment strength parallel to the grain in timber for fully threaded bolts and glued-in rods were proposed.

Studies have examined the environmental impacts of soil stabilization; however, the costs of distinct dosages in such methods remain unexplored. Indeed, it is not yet clear whether there is a trade-off between cost and environmental impacts for soil stabilization dosages. This technical note seeks to address this gap by performing an economic analysis of three dosage strategies (high binder/low dry unit weight, medium binder/medium dry unit weight, and low binder/high dry unit weight) considering five values of a porosity-binder index and strength and stiffness as performance parameters. Such results are then combined with environmental impact data to create a decision-making model for optimal dosages considering the economic and environmental dimensions of sustainability. An example of a road base ($q_u=\mathrm{1,034}\mathrm{kPa}$) is presented to illustrate how the model can be applied in real-world projects. This $q_u$ corresponds to a porosity-binder index of 32.44, which can be attained by different combinations of dry unit weight and binder content ranging respectively from $16–19\mathrm{kN}/{\mathrm{m}}^3$ to 3%–7%. The proposed model makes it possible to determine the dosage with minimal cost and environmental impacts: a lime content of 3% and dry unit weight of $17.44\mathrm{kN}/{\mathrm{m}}^3$. The binder was found to be the main contributor to cost and environmental impacts, indicating that dosages with minimal binder content and maximum dry unit weight should be preferred. The findings presented suggest that there is no trade-off between environmental and economic pillars, and dosages with minimal cost and impacts can be created.

Recently, the use of light weight deflectometers (LWDs) for in-situ measurement of soil/aggregate layer moduli has gained significant popularity. A recent study sponsored by the Idaho Transportation Department (ITD) involved extensive laboratory characterization of eight different subgrade soil materials to establish a database of inputs to be used during mechanistic-empirical (M-E) pavement design. Along with commonly used soil index and strength tests, as well as resilient modulus tests, this study also performed LWD testing in Proctor molds to establish $E_{\mathrm{LWD},\mathrm{MOLD}}$ as a representative soil modulus value. The objective was to evaluate the suitability of LWD testing of soils in the laboratory to establish representative resilient modulus values for use during M-E pavement design. The $E_{\mathrm{LWD},\mathrm{MOLD}}$ value exhibited very strong correlations with the summary resilient modulus value [defined by the National Cooperative Highway Research Program (NCHRP) 1-28A] at three different moisture contents. This approach of LWD testing inside Proctor molds deserves further exploration as it can potentially enable highway agencies to predict soil resilient modulus values without the need to perform cumbersome and resource-intensive repeated load triaxial testing.