Journal of Materials in Civil Engineering

This review paper gives a brief overview of moisture damage and the materials used to prevent it. It has been observed that bituminous mixes suffer from durability issues such as moisture damage and oxidation. Even the usage of conventional antistripping materials such as lime and liquid antistripping agents (LAS) are not able to prevent the moisture damage completely. The studies supporting the effect of particle sizes of additives on the moisture resistance of bituminous mixes was the motivation behind the investigation of the use of nanomaterials for this global problem. The scope of this review is to understand the mechanism of moisture damage and the use of nanotechnology for its prevention. This study is an effort to look into the recent use of some nanomaterials in bituminous mixes for the development of mixes with better durability against moisture-induced damages. This review also focuses on the important nanocharacterization tools that are employed to understand the moisture damage of bituminous mixes at the nanoscale.

The metal organic framework [MIL-101(Cr)] was used as a second modifier to prepare MIL-101(Cr)-styrene-butadiene styrene (MIL-101(Cr)/SBS) modified asphalt. The influence of MIL-101(Cr) addition and contents on rheological properties and the amount and nature of fumes produced during higher temperature applications of modified asphalt were studied. Dynamic shear rheometer and multistress creep recovery tests revealed that MIL-101(Cr)/SBS modified asphalt exhibited better viscoelasticity, high temperature stability, and rutting resistance relative to pristine SBS modified asphalt. Compared with the pristine SBS modified asphalt, the storage modulus and loss modulus of 0.05% MIL-101(Cr)/SBS modified asphalt at 46°C increased by 100.9% and 88.1%, respectively. GC-MS analysis concluded that the addition of MIL-101(Cr) effectively reduced the generation of harmful fumes (from 26 to 3) in MIL-101(Cr)/SBS modified asphalt; thus, it can significantly reduce environmental pollution. Fluorescence microscopy analysis showed that MIL-101(Cr) was evenly distributed in SBS modified asphalt, whereas TGA tests revealed higher thermal stability of MIL-101(Cr)/SBS modified asphalt than SBS modified asphalt. This study, based on the incorporation of MIL-101(Cr) into SBS modified asphalt that leads to the effective control of harmful fumes production and enhanced thermal stability, could offer significant potential for designing alternative types of asphalt that enable highway and construction industries to adhere to road and environmental agencies standards.

The corrosion behavior of a low chromium-content stainless steel, ASTM A1010 (also under the dual designation ASTM A709 Gr50CR), was investigated. This stainless steel has been identified as a candidate for bridges located in highly corrosive environments where other steels have exhibited poor corrosion resistance. Three conditions likely to occur in bridge environments were investigated: the galvanic corrosion of A1010 connected to dissimilar metals; the crevice corrosion of A1010 plates connected with other A1010 plates; and the effect of various surface preparation techniques on the corrosion behavior of A1010 plates. Each condition was studied during an accelerated cyclic corrosion test. The results from the accelerated corrosion tests are given in terms of rate-of-corrosion and plate thickness loss. The results indicate that the corrosion resistance of A1010 in corrosive environments was significantly different in near-horizontal orientations compared to vertical orientations, A1010 received localized galvanic protection in certain dissimilar steel plate connections, and A1010 was susceptible to pitting corrosion in plate connection details. Additionally, galvanic corrosion of certain common bridge steels connected to A1010 experienced accelerated corrosion rates up to 1.65 times greater than when galvanic corrosion was inhibited.

In recent years, the mechanical behavior of recycled aggregate concrete (RAC) under different condition has attracted great attention from researchers. As RAC can make full use of the concrete waste generated by the demolition of buildings, it can promote the development of green and sustainable construction technology. The true-triaxial compression tests of RAC with different replacement rates (0%, 50%, 100%) after high temperatures (200°C, 400°C) were carried out for the first time. Through the study, the triaxial compressive strength, deformation and stress-strain curve of RAC under different stress ratios are obtained. The improved failure criterion of concrete is established. It is found that the true-triaxial compressive strength and peak strain under high temperature are greater than those under uniaxial compressive strength and room temperature. The main failure modes of RAC specimens under true-triaxial test are sheet splitting and shear failure. The research results obtained in this work are the first to study the true-triaxial compression behavior of RAC after exposure to high temperatures.

Combustion of rice husk produces a supplementary cementing material known as rice husk ash (RHA). Current studies on enhancement of physical properties and durability of cementitious composites with RHA are limited to applications in conventional construction. Automation in construction using additive manufacturing technique—commonly known as construction three-dimensional (3D) printing—is an emergent strategy. Because the printing process is formwork-free and requires a continuous deposition of layers with structural stability, mix design of a 3D printable concrete is different from conventional concrete. Portland cement replacement by RHA improves the sustainability of a mixture as a construction material. In this work, 20% by weight of cement is replaced with RHA. Compressive strength and workability loss of designed mixes—with and without RHA—were studied at early age and compared with fresh properties of proven printable mortar available in market. Incorporation of RHA has shown significant improvement in rheology of mortar at the rate required for construction 3D printing at large scale.

Recycled concrete aggregate (RCA) is the result of the demolition of concrete structures and pavements. Using RCA to replace quarried aggregates in paving projects is one way to utilize the millions of tons of concrete waste that is produced annually and landfilled. However, RCA may have inferior physical properties when compared to virgin aggregates, such as the presence of recycled mortar and preexisting deficiencies. This study evaluated the potential use of RCA from D-cracked pavement for soil stabilization. D-cracking is a type of pavement deterioration that originates in the coarse aggregate particles due to freezing and thawing. The engineering properties of low-plasticity clay with RCA and three common regional stabilizers (i.e., lime, Class C fly ash, and a combination of portland cement and fly ash) were investigated. Clay mixtures with varying proportions of chemical stabilizers and RCA from D-cracked pavements were evaluated by comparing measured unconfined compressive strength, linear shrinkage, and the California bearing ratio. Laboratory test results indicated that RCA, in conjunction with all cementitious materials, except lime, improved clay strength, stiffness, and shrinkage properties. The results from this study highlight that RCA from D-cracked pavements can be used for clay subgrade stabilization.

This study aims to develop a new type of road active deicing material that can efficiently and quickly remove ice/snow while meeting the mechanical properties requirements. A conductive ethylene–propylene–diene monomer (EPDM) rubber composite material with active deicing and snow melting is put forward. The composite material consisted of three layers: (1) a heat transfer layer prepared by adding graphite into EPDM rubber, (2) carbon fiber cloth sandwiched in EPDM rubber as a heat generating layer, and (3) an insulation layer composed of aluminum silicate fiber cloth and EPDM rubber. The three layers were vulcanized into one at high temperature and pressure. Tests for mechanical and electrothermal properties were carried out. The results show that graphite can improve the thermal conductivity and mechanical properties of EPDM rubber. The resistance of the composite material is low and stable. A large amount of heat can be generated in a short time at a low voltage. It is proven that the conductive EPDM rubber composite can be used as an active deicing material for roads.

The increased contribution of science-intensive clean materials and technologies to the total industrial production is one of the essential prerequisites for the future of sustainable industrial development. Chemical activation based on a nonfired or low-temperature approach for the production of cementitious materials from glassy aluminosilicates, including calcined clays, is an intensively developing and promising clean technology. This study investigated the potential of calcined clays as precursors of alkali-activated cements (AACs) by considering three types of low-grade multimineral clays (with a clay mineral content of $<20\%$). The alkali activation of the calcined clays was analyzed based on the type and content of clay minerals, presence of calcite, calcination temperature, type of alkali activator, and curing conditions. The results indicated that clays containing 20% of $2:1$ layer lattice clay minerals are not suitable as precursors of AACs, while those containing 9%–12% of $1:1$ and/or $2:1$ layer lattice minerals combined with 29%–32% calcite lead to hardened pastes displaying compressive strengths of up to 12.4 MPa after 2 days and 20 MPa after 28 days and after steam curing. The reaction products of 6M NaOH-activated systems determined by XRD, TG/DSC, and FTIR spectroscopy analyses were X-ray amorphous binder gel, calcite (${\mathrm{CaCO}}_3$), clinozoisite (${\mathrm{Ca}}_2{\mathrm{Al}}_3({\mathrm{SiO}}_4{)(\mathrm{Si}}_2{\mathrm{O}}_7)(\mathrm{O},\mathrm{OH}))$, and gaylussite (${\mathrm{CaNa}}_2({\mathrm{CO}}_3{)(\mathrm{H}}_2{\mathrm{O})}_5$).

In Central South of China, granite residual soil (GRS) is one of the main subgrade soils for transportation infrastructures. To further understand the effects of drying and wetting (D-W) cycles on the mechanical responses of GRS, this paper presents a series of experimental tests on the microscopic characteristics and mechanical behaviors of reconstituted GRS under different D-W cycles (0, 1, 2, 4). The particle size distribution curve of GRS exhibited an evident unimodal peak. However, the unimodal distribution gradually transformed into a bimodal form with an increase of D-W cycles. A novel designed consolidation apparatus equipped with paired bender elements in three orthogonal directions is developed to investigate the compression behavior and small-strain stiffness of reconstituted GRS. Test results show that the GRS exhibited complicated compression behaviors in response to the cyclic D-Ws. The preconsolidation stress reached a maximum value at the end of the 2nd cycle and then decreased with the subsequent D-W cycles. Cyclic D-Ws resulted in a drastic increase in the small-strain stiffness, and the beneficial effect was more pronounced in the 1st cycle. Stress-induced fabric anisotropy occurred during the compression test. Both the stiffness and stiffness anisotropy increased with increased loading. In the triaxial shearing test, the volume change of the GRS was characterized by coupling effects between the suction history and confining pressure.

Overburden (OB) generated from coal mining industries are a major source of environmental pollution as well as land degradation worldwide. Recycling of such waste products through effective application in the construction industry leading to environmental sustainability is the need of the hour. The present study focuses on the feasibility of recycling the OB as an alternate track subballast material. A series of tests have been conducted considering its shape, chemical composition, durability, stress–strain responses, and load-deformation behavior. Comparisons have been made with respect to standard subballast aggregates. It is observed that the OB can be used as a subballast material. The load-deformation behavior observed in the track model tests indicate that provision of geocell reinforcement can further enhance the performance of OB as subballast material.

To study the development of high-strength concrete creep under cyclic load as well as the distribution of moisture flow velocity, pore pressure, and equivalent stress, a concrete creep model based on a porous medium was used for creep simulation. At the meso-scale, the coupling of internal aggregate, mortar, and moisture under cyclic load was simulated to obtain the creep coefficients. Additionally, the theoretical values were compared with the experimental results. A finite-element program combined with a porous media theory can simulate the motions of aggregate, mortar, and moisture in concrete at meso-scale as well as predict the development of high-strength concrete creep. As the motions of internal moisture, aggregate, and mortar accelerate under cyclic loads, the high-strength concrete creep is larger than that under a constant load. The creep simulation program can be well applied to the research of concrete creep and the engineering design of concrete materials. It has important reference to study the micromechanism of high-strength concrete creep.

To reveal the damage evolution mechanism and dynamic mechanical performances of lightweight shale ceramsite concrete (LWSCC), the damage evolution process and dynamic impact characteristics of LWSCC were studied by acoustic emission monitoring and split hopkinson pressure bar (SHPB) testing. Results show that in the quasi-static unconfined compression test, the ringing count and energy value are closely related to the strain, and 60% strain is the transition point of the crack growth rate. The growth curve of acoustic emission events lags the stress growth. The inflection point appears at 65% strain of the stress-strain curve, and that in turn appears at 72% strain of the acoustic emission event-strain curve. With the increase of the strain rate, the stress peak, incident wave energy, absorbed energy, and specific energy absorption values all increase, and the strain-rate effect is obvious. Based on the monitoring data of acoustic emission, the damage evolution equation of LWSCC was established under uniaxial compressive testing, and the dynamic damage constitutive relation was constructed of LWSCC under high-strain-rate impact testing. The conclusions obtained in this study provide a theoretical basis for the design of antishock structures.

Effect of corrosion on the mechanical degradation of high-strength bolted steel connection is experimentally investigated in this study. Eleven high-strength bolt joints were fabricated and nine of them were subjected to accelerated corrosion tests to different levels of mass loss. After corrosion, tensile tests were conducted on these bolted connections, and a procedure was proposed to determine the slip coefficient and the clamping force of corroded specimens. Finite-element (FE) analysis was also conducted. Tensile test results demonstrated a five-stage load–displacement curve, and all the specimens fractured at the tensile plate across the bolt hole. Corrosion reduces the clamping force, slip coefficient, initial slip load (or friction shear strength), full slip load, yield load, ultimate load, and ductility, all of which are closely related to the corrosion loss of the entire specimen. FE analysis showed comparable characteristic loads with these from tensile tests.

A series of nine butt-welded coupons were tested dynamically following a sinusoidal load that reached 0.50, 0.60, and $0.70{\mathrm{F}}_{\mathrm{y}}$ for an A36 low-carbon steel. This load was applied at 5 Hz with an initial $0.10{\mathrm{F}}_{\mathrm{y}}$ offset to maintain a full-tension test at all times to avoid compression. Two main variables were of interest for the present research: (1) applied strain; and (2) surface magnetic field. Strain gages and magnetometers tracked the said variables at two locations: at the base metal and at the proximity of the heat affected zone (HAZ). The testing was aimed for fatigue at high-load levels, and it stopped once it reached 100,000 cycles. At lower levels, it remained a nondestructive test. The results present a semielliptical correlation between the strain and surface magnetic field similar to the classic mechanical correlation between stress and strain, presenting some type of magnetic hysteresis. The said semielliptical correlation is not steady in time, and it shows a presumable progression of damage accumulation through a second-order parameter extracted from the said correlation, which shows a clear agreement (by means of a complete reversal in magnitude) with classical S-N fatigue failure behavior. Also, when analyzing the behavior in time, complete reversals in phase or out-of-phase behavior between the semisinusoidal magnetic signals at early stages of the test differ from those at late stages. This particular change in time also indicates a physical change on steel as testing continues, and it can be traced in a timely fashion by tracking the magnetic response in both base metal and HAZ areas. This nondestructive analysis of surface magnetic fields suggests that magnetic fields, although small in magnitude (measured in $\mathrm{\mu T}$), can be used as a nondestructive means for determining damage accumulation and to separate safe stages from nonsafe stages of service for a butt-welded tension member.

The objective of this study is to investigate how exposure of concrete to organic acids affects its resistance to mechanical abrasion and to identify the most important factors contributing to its abrasion resistance under acid exposure. The abrasion resistance of both cement pastes and concrete materials with different water-to-cement ratios (w/c), coarse aggregate type, and proportions of aggregate were experimentally measured after exposure to organic acids. In addition, the effect of silica fume, latex, fibers, and chemical surface hardeners on the abrasion resistance of cement paste and concrete materials were investigated. The results indicate that in the absence or presence of an organic acid attack, the abrasion resistance of concrete is primarily a function of the hardness of the coarse aggregates and w/c plays a secondary role. While a secondary factor, the effect of w/c on the abrasion resistance is more significant in the presence of an organic acid attack.

One of the common distresses observed in asphalt concrete (AC) pavements under repeated vehicular and thermal loadings is cracking. Overlay placement is a quick remedy to rehabilitate these distressed surfaces. Unfortunately, this practice without treating the cracks will not resolve the cracking issue because the existing cracked surface soon propagates the cracks through the new layer, resulting in a phenomenon known as reflective cracking. Different types of geosynthetic interlayers have been used to retard the reflective cracks, thereby enhancing the overlay’s service life. The preliminary step in quantifying the service life improvement is measuring the fatigue life enhancement in the laboratory. This paper developed a test procedure to conduct four-point beam (4PB) fatigue tests, adapted a permanent deformation evolution model (PDEM) to predict the fatigue life of the 4PB specimens under laboratory testing conditions, and compared the fatigue life of beam specimens reinforced with three types of geosynthetics at 10°C, 20°C, and 30°C. The improvement factor measured using the PDEM model indicated that the geosynthetic reinforcement in AC beams increased the fatigue life on the order of 1.2–12 times depending upon the temperature at which the test was performed and the choice of the geosynthetic type. The best fatigue life outcome is expected when the improvement factor calculated for the geosynthetic-reinforced asphalt concrete’s bond strength and fracture energy meets the right combination of threshold values. The limitation of the study is that the improvement factors evaluated from the laboratory fatigue life require calibration factors to predict the field performance. Further field studies of the geosynthetic-reinforced pavements will help establish these calibration factors.

Owing to heavy toxic metal concentration such as copper, lead, zinc, sulfur, cadmium, and chromium, jarosite particles from the zinc industry are considered a hazardous waste material. Proper and safe disposal or converting this hazardous waste into nonhazardous material is vitally important. This study investigated the potential of utilizing jarosite as a substitute for portland cement in roller-compacted pavement (RCCP) mixes containing reclaimed asphalt pavement (RAP) material. Portland cement was partly replaced with jarosite in proportions of 5%, 10%, 15%, 20%, and 25% in mixes containing 50% RAP aggregates and tested for mechanical, durability, and microstructural properties. Based on test results and analyses, the incorporation of jarosite in RAP-RCCP mixes increased the fresh water demand owing to its hydrophilic nature, which in turn increased the porosity and water absorption and decreased the resistance to chemical attack. Jarosite incorporation level up to 5% may be recommended as the best mix because it exhibited 20% higher flexural strength than the recommended flexural strength of 3.67 MPa at 28 days for RCCP mixes, as well as enhanced abrasion resistance. Despite the inability to produce additional calcium silicate hydrate gels during the secondary pozzolanic reaction, the jarosite particles may have acted as a filler and resulted in a denser microstructure as revealed by scanning electron microscope images. Utilization of jarosite in RAP-RCCP mixes also would provide other ecological advantages, such as reduction of the burden on disposal landfills, lowering virgin aggregate and cement consumption, and lowering the carbon footprint.

Owing to the soaring environmental threats ensued by the ever-increasing quantities of end-of-life tires (ELTs) across the globe, today the issue of recycling and reusing these waste materials is being discussed by scientists of various fields more than ever. As a main industrial and scientific area, civil engineering is a consumer of new and waste materials and experts are striving to introduce new and sustainable ways of reusing ELTs as construction material. In this study, a series of static and cyclic laboratory tests were performed to contribute to managing and preventing the burial of a part of hazardous wastes produced during the recycling process of worn tires. Compaction, direct shear, unconfined compressive strength (UCS), California Bearing Ratio (CBR), and repeated load triaxial (RLT) tests under various stress levels were conducted after the addition of different contents of waste tire textile fibers (WTTFs) to a sandy soil. Fiber inclusion enhances all geotechnical properties of the soil under static state. Under dynamic state, especially when employed to reinforce the subgrade of a road, these fibers can increase the energy absorption and dissipation properties of the soil, as well as increasing the resilient modulus and damping ratio with an optimum fiber content of 1%–2%. An energy-absorbing layer could be established by using the fibers. A new model is also presented to accurately predict the resilient modulus of the reinforced soils. Moreover, the model is adapted for unreinforced soil and compared against some relatively precise models in the literature. The proposed model yields totally satisfactory results.

Recycled concrete aggregate (RCA) is a key tool for improving sustainability in the construction and demolition industries. The use of RCA in new concrete is, in part, obstructed by the dearth of research available on the durability of RCA systems. This paper investigates the efficacy of replacing portland cement with supplementary cementitious materials (SCM), known to mitigate alkali-silica reaction (ASR) in concrete with virgin aggregates, as a method for reducing expansions related to ASR from reactive RCA. Fly ash (Class F), silica fume, and metakaolin were all investigated for their ability to mitigate ASR. The results of modified accelerated mortar bar tests are presented for two different RCAs when using 100% portland cement, binary blends of portland cement and fly ash, and ternary blends of portland cement, fly ash, and either metakaolin or silica fume. The results indicated that SCM can mitigate ASR in concrete made with RCA, though not as effectively as for natural aggregate systems. Higher levels of mitigation may be required for some RCAs, compared to the level necessary to mitigate or prevent ASR in concrete made with the original aggregates, depending on composition of the RCA.

Data on temperature-dependent thermal properties of concrete are critical for fire-resistance evaluation of concrete structures. This paper presents the effect of temperature on thermal properties of different types of ultrahigh-performance concrete (UHPC). A set of thermal property tests were carried out on UHPC specimens in the 20°C–800°C temperature range for measuring thermal conductivity, specific heat, mass loss, and thermal expansion. The test variables included type of UHPC [with steel, polypropylene (PP), and hybrid fibers] and temperature range. Data from the tests were used to evaluate the effect of temperature on thermal conductivity, thermal expansion, specific heat, and mass loss variations in UHPC. Furthermore, the measured test data were utilized to propose relations expressing each thermal property as a function of temperature. The proposed relations can be used as input data for evaluating fire resistance of structures fabricated with UHPC. In addition, high-temperature thermal properties of UHPC were compared with those of conventional normal-strength concrete (NSC) and high-strength concrete (HSC). Data from these tests show that temperature has a significant influence on the thermal properties of UHPC, while the presence of steel or PP fiber reinforcement has very little influence on the thermal properties of UHPC. Also, the thermal conductivity and thermal expansion of UHPC is slightly higher and mass loss and specific heat are lower than that of NSC and HSC in the 20°C–800°C temperature range.

In this paper, a two-step model is proposed to predict the effective chloride diffusivity of cement paste and cement mortar. The prediction effective chloride diffusivity results of cement paste and cement mortar are compared with two different experimental method results. In the two-step model, the effective chloride diffusivity of cement paste is predicted based on the porosity and the effective diffusivity of the solid phase using the general effective media (GEM) model. Based on the GEM model, the effective chloride diffusivity of cement mortar is predicted by the composite spheres assemblage (CSA) model, which considers the aggregate volume fraction and the effective diffusivity of the interfacial transition zone (ITZ). As important inputs of the model, the porosities of cement paste and mortar are obtained by low field nuclear magnetic resonance (LF-NMR). The effective chloride diffusivities of cement paste and mortar are also determined by a newly proposed modified noncontact electrical resistivity measurement (MN-CM) based on the Nernst-Einstein equation and the rapid chloride migration test (RCMT). The results show that the effective chloride diffusivities from the proposed prediction model is in good agreement with the experimental results. The proposed prediction model could be used to predict the diffusivity of cement-based materials.

Polymers have been widely known as nontraditional soil stabilizers capable of replacing common soil additives to reach superior soil stabilization outcomes. While numerous studies represent the efficiency of polymers as one of the soil additives, there is still ambiguity about the optimum condition of curing, soil-polymer interaction, and effect of each property of the polymer on the final mixture. In this study, to investigate the effect of sample preparation on the strength of the clay, five different curing methods were examined to assess the unconfined compressive strength (UCS) of the stabilized clay with acrylic polymers. Since the glass transition temperature ($T_g$) is one of the most important characteristics of polymers that influences various mechanical properties of the polymer such as elastic modulus, in this study, it is considered by choosing two similar acrylic polymers with different glass transition temperatures. Two acrylic polymers with $T_g$ above and below the ambient temperature (i.e., $-13°\mathrm{C}$ and $+33°\mathrm{C}$) were used as soil stabilizers. Different curing variables including polymer concentration (0%–10%), curing time (immediately to 1 week), and curing temperature (ambient to 100°C) may control the clay-polymer composite behavior and were analyzed in this work. For Method I, samples were prepared, compacted, and tested immediately. For methods II and III, samples were oven-dried at 100°C for 1 day, air-dried at room temperature for 7 days, respectively, and subjected to UCS testing. Method IV consisted of curing the remolded samples in a double vinyl bag for 1 day before the UCS test. For Method V, the treated soil mix was oven-dried and then remoistened (using the original liquid: i.e., water or polymer solution) to reach the target moisture content followed by a UCS test. Samples cured at 100°C in the oven showed a significant increase in the UCS due to a complete moisture loss. There was no considerable difference between the samples cured in a vinyl bag and noncured samples. The results also showed that the polymer with a higher $T_g$ is more effective for soil improvement given all other conditions are kept unchanged.

The pullout response of basalt textile embedded in cementitious matrix specimens was investigated under different loading rates and temperatures. Two types of specimens, basalt single yarn and basalt textile, were tested. The pullout behavior of the specimens was evaluated in terms of initial pullout force, maximum pullout load (peak pullout load), work of pullout, and work of peak force. Pullout velocity ranged from quasi-static ($5.0\times {10}^{-5}\mathrm{m}/\mathrm{s}$) to dynamic (1, 2, 3, and $4\mathrm{m}/\mathrm{s}$); Temperature effects were studied under four temperatures ($-25°\mathrm{C}$, 0°C, 25°C, and 50°C) and dynamic loads. The experimental results indicated that pullout speed, temperature, and textile form obviously affected the pullout responses of the tested specimens. At each temperature, the initial and peak pullout forces under dynamic loading were higher than the same forces under static loading. In addition, pullout work and peak pullout work appeared to improve with increasing loading rate under each temperature. However, when pullout velocity was constant, initial pullout force, peak pullout force, work of pullout, and work of peak force decreased with increasing temperature. However, pullout work and peak pullout work appeared to improve with increasing pullout velocity under each temperature. Scanning electron microscopy (SEM) images were taken in order to observe the morphology of the interfaces and yarns after pullout.

Reclaimed asphalt pavement (RAP) mixes generally have good moisture and rutting resistance. However, the fatigue performance of the RAP mixes is a matter of concern because the RAP binder is generally brittle because of age hardening. Asphalt mixes can heal and recover from the fatigue damage caused by repeated wheel load application. The healing characteristics of the mix depend to some extent on the flow characteristics as well as the chemical makeup of the binders. Linear amplitude sweep (LAS) testing was performed for evaluating the fatigue performance of RAP binders. The fatigue and healing characteristics of different virgin-RAP binder blends were measured in an oscillation fatigue test conducted with varying rest periods using dynamic shear rheometer. The slopes of the fatigue life versus rest period plots were taken as indicators of the effect of rest period on fatigue life or healing indices (HI). Different rheological and chemical parameters measured in terms of surface free energy and the indices calculated using Fourier transform infrared (FTIR) spectroscopy correlated well with the healing potential of RAP binders.

Reclaimed asphalt pavement (RAP) has been used recently in warm-mix asphalt (WMA) as a part of sustainable and green pavement design. The main issue of using high RAP content in WMA is associated cracking. To optimize the use of RAP in WMA and reduce life cycle costs, a robust tool of testing to control the quality of asphalt mixtures in terms of cracking is vital. Among the available tests, the semicircular-bending (SCB) test is regarded as simple but useful to characterize the cracking behavior of asphalt concrete. The test has been standardized in a number of standards for 150-mm-diameter samples. Recently, the authors investigated and proved that the SCB test on 100-mm-diameter samples produced acceptable repeatability compared with standardized samples based on experimental and numerical tests, providing an alternative choice for practitioners and researchers with the tools and equipment available to conduct the test. However, the characterization ability of cracking behavior, in particular the fracture and fatigue, of asphalt mixtures using this nonstandardized test has not been studied yet. Thus, this study was conducted to investigate the potential for characterization of cracking behavior of nonstandardized SCB testing for asphalt mixtures. Laboratory tests were conducted on different mixtures, including hot-mix asphalt, WMA, and WMA with added RAP. A four-point bending fatigue test was also performed to compare with results from the SCB test. The study found that the SCB test on nonstandard samples could be used to evaluate the cracking resistance of asphalt mixtures. It was also found that production temperatures, WMA technologies, RAP contents, notch lengths, and air voids considerably affected the cracking behavior of asphalt mixtures.

The construction sector is mainly accountable for the diminishing of natural resources and environmental imbalances due to unplanned mining activities. In this context, use of recycled fine aggregate (RFA) from construction and demolition (C&D) waste can be considered as an effective elucidation. Conventional mix proportioning of RFA in concrete can not be used. To address this issue, a novel mix-proportioning method is developed using particle packing density and minimum paste theory. Fresh and hardened properties of newly developed mix were evaluated. Life-cycle cost analysis (LCCA) was also performed to evaluate the efficacy of the developed concrete using RFA. The result shows that the developed mix design uses lesser quantities of cement and fine aggregates. Replacement of about 30% river sand (RS) by RFA was found optimum. The increase in compressive, flexural, and splitting tensile strength and modulus of elasticity at 56 days was by 11.0%, 9.7%, 3.8%, and 4.0%, respectively. It is concluded that both RS and RFA concrete mix showed superiority in terms of ${\mathrm{CO}}_2\text{-}\mathrm{e}$ and cost compared with conventional concrete.

Liquefaction is a phenomenon where the soil mass behaves like a liquid due to the rise in excess pore-water pressure, which results in the complete loss of shear strength. Most of the conventional liquefaction-mitigation practices have several limitations, of which environmental issues are the most prevalent. Therefore, a sustainable and efficient technique needs to be developed. The use of biopolymers in the field of geotechnical engineering for improving various soil properties has been a popular research theme in recent years. Although its application in the enhancement of engineering properties of soil have been investigated, biopolymer-treated soils have not been much explored for sustaining dynamic loading or against liquefaction failure. In the current study, a series of consolidated undrained, strain-controlled cyclic triaxial tests were conducted on agar biopolymer–treated natural silty sand obtained from Kalpetta, Kerala, India. The treated soil at different curing times (3, 7, and 28 days) was subjected to dynamic loading at varying cyclic axial strains (0.3%, 0.5%, 0.8%, and 1%). The dynamic secant shear modulus was found to be enhanced significantly; shear modulus of 7-day-cured, 2% agar biopolymer–treated soil was 317% more than untreated soil samples at the 50th loading cycle. At the same time, the excess pore pressure buildup was reduced by a great extend due to treatment. The maximum excess pore pressure ratio was just 0.67 in treated soils, which was 33% less compared with untreated soils. This indicates the potential of using biopolymers as an environment-friendly alternative for mitigation of liquefaction-induced soil failure in view of their pore-filling and stiffness-enhancement properties.

In this study, the fatigue performance of asphalt binder and mastic containing nano-silica and synthesized polyurethane was evaluated. Modifiers were used in three values of asphalt binder weight. The asphalt binder does not work alone in the asphalt mixture, but its combination with the filler is known as an active substance in the reaction. Superpave fatigue parameter (${\mathrm{G}}^{*}\sin \delta$), time sweep (TS), and linear amplitude sweep (LAS) tests were used to evaluate the fatigue. The viscoelastic continuum damage (VECD) model has been successfully implemented for investigation of the fatigue damage in asphalt binder materials. The VECD method was utilized due to higher precision in measurement, less time consumption of test execution, and being model-based approach resulting in less number of tests required for each strain level. Fourier-Transform Infrared Spectroscopy (FTIR) was used to evaluate chemical structure. Johnson’s criteria cannot be used to estimate the fatigue life of mastic in this regard; the maximum shear stress criterion is reliable to evaluate fatigue performance of mastic. Results of this study indicated that damage mechanism in asphalt binder and mastic, especially in high strains, is different from that of modified and neat asphalt binder. Furthermore, the parameter of damage intensity is a good criterion for evaluation of fatigue performance in asphalt binder and mastic.

The Superpave mix design is a process of repeatedly optimizing the aggregate gradation and asphalt content in accordance with specified limits. As one of the important design parameters, the number of design gyrations ($N_{\mathrm{des}}$) is adopted empirically to be a fixed number under a specific traffic level. Based on the concept of a performance-oriented approach, this study regarded $N_{\mathrm{des}}$ as a variable design parameter and evaluated the influences of two design cases on the performance of asphalt mixture: $N_{\mathrm{des}}$ variables and asphalt content (gradation unchanged) and $N_{\mathrm{des}}$ variables and aggregate gradation (asphalt content unchanged). Two groups of experiments were designed. The first group used $N_{\mathrm{des}}$ levels of 50, 75, and 100 gyrations, and less asphalt content was adopted with a higher $N_{\mathrm{des}}$. The second group used compaction levels of 50, 75, 100, and 125 gyrations, and coarser aggregate gradation was adopted with a higher $N_{\mathrm{des}}$. Both groups of experiments showed that with an increase in $N_{\mathrm{des}}$, rutting performance was increased and low-temperature performance was decreased. In addition, in the former group of experiments, fatigue performance was decreased with the increase of $N_{\mathrm{des}}$. Following these rules, this paper took Hainan province mix design as a case, and $N_{\mathrm{des}}$ was optimized to meet requirements. It can be seen that regarding $N_{\mathrm{des}}$ as design variable is necessary and can improve flexibility in the design.

In this research, an attempt was made to explore the possibility of using a stabilization and solidification ($\mathrm{S}/\mathrm{S}$) technique for the treatment of sandy soil contaminated with diesel and crude oil using different stabilizers. For this purpose, soil samples were collected and contaminated by diesel and crude oil at three different percentages (2.5%, 5%, and 10% by weight of dry soil). Effects of oil contamination of soil were evaluated, and then $\mathrm{S}/\mathrm{S}$ treatment was carried out using ordinary portland cement (OPC), cement kiln dust (CKD), and limestone powder (LSP). The performance of $\mathrm{S}/\mathrm{S}$-treated soils was evaluated by measuring the changes in compaction characteristics, unconfined compressive strength (UCS), permeability, and heavy metal and hydrocarbon contents. Toxicity characteristic leaching procedure (TCLP) and total petroleum hydrocarbons (TPH) tests on $\mathrm{S}/\mathrm{S}$-treated soil were conducted to observe the effect of the $\mathrm{S}/\mathrm{S}$ treatment on the reduction of the soil pollution potential. Scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) analyses were carried out to examine the changes in the microstructure and mineralogy of the soil after its $\mathrm{S}/\mathrm{S}$ treatment. Results of this investigation indicate that the $\mathrm{S}/\mathrm{S}$ treatment of the oil-contaminated soil improved the compaction characteristics, UCS, and resistance against permeability and leachability.

The thermal conductivity of soil is an important parameter that determines the geothermal properties of geotechnical engineering structures. In this research, a series of thermal needle tests were conducted to investigate the effects of water content, dry density, degree of saturation, and porosity on the thermal conductivity of mucky silty clay. Three models were used to predict the thermal conductivity of mucky silty clay in Nanjing, China. The results indicate that the critical water content of 25% can be attained by mucky silty clay, while its thermal conductivity is related linearly and exponentially to dry density and degree of saturation, respectively. Similarly, thermal conductivity is exponentially related to porosity. A modified predictive model of mucky silty clay that considers its high water content was established based on a parallel-series mixed model. By comparing it with three classic models and three sets of measured data from three sites in Nanjing, it is demonstrated that the modified predictive model can accurately estimate the thermal conductivity of mucky silty clay. This research contributes to a more comprehensive understanding of the heat transfer mechanism in mucky silty clay and provides thermal parameters for the design of geothermal-related structures in such soils.

This paper presents a study of the effect of curing on the salt-scaling resistance of concrete containing supplementary cementitious materials (SCMs) under lab conditions. Two curing methods were examined: moist curing and wrapping in a tight plastic sheet. Wrapping concrete slabs in plastic was adopted to represent curing methods that do not supply the concrete with additional water. The two curing methods produced different scaling results; however, the outcomes did not change in terms of meeting or failing the acceptance limit. Curing in plastic wraps produced higher carbonation depth prior to exposing the sample to the salt solution. This could have contributed, partly, to the higher scaling obtained in wrapped samples, other than the sample with 40% high-calcium fly ash. For this sample, there is evidence that curing using plastic wraps maintained high alkali concentration in the surface concrete, which could have enhanced the pozzolanic activity of the fly ash at the surface.

The improvement of soils that are not suitable for a particular purpose through techniques that combine densification and the incorporation of portland cement have been extensively done for decades in spite of the poor environmental performance related to such material. In this context, the development of alternative binders through the use of industrial byproducts may be an alternative to mitigate environment-related issues. Therefore, the current study aims to evaluate the performance of a gap-graded soil via incorporation of a binder composed of coal fly ash and hydrated lime. For this, strength, stiffness, and durability tests were carried out on compacted soil–coal fly ash–hydrated lime specimens molded at different porosities and with distinct coal fly ash and hydrated lime contents. Moreover, the stiffness of the specimens was also assessed during wetting-drying cycles. Results of all mechanical tests have shown the significant influence exerted by porosity, followed by the relatively minor impact of the amounts of binder (here composed of lime plus fly ash). Hence, good correlations between the response variables and the adjusted porosity/binder index ($\eta /B_{iv}^{0.28}$) were obtained. Furthermore, an innovative approach to replacing the laborious durability test is proposed.

This paper analyzed the eco-efficiency of concretes (water/cement ratio = 0.50; cement $\mathrm{content}=350\mathrm{kg}/{\mathrm{m}}^3$, and slump = 7 cm) with blended cement containing 25% by weight calcined pozzolan obtained from a low-grade kaolin (HKC) and an illitic shale (HIC) compared with ordinary portland cement concrete (HPC). The fresh, mechanical, and transport properties of these concretes were evaluated, as were the concrete efficiency parameters and the global warming potential (GWP) measured as ${\mathrm{CO}}_2\mathrm{eq}/{\mathrm{m}}^3$ concrete. The results classify both blended concretes as acceptable for use in construction, whereas HIC performs better as fresh concrete and has a slightly higher resistance to chloride penetration, HKC performs better regarding to mechanical and water transport properties. The suitability of clay or shale depends on the availability and distance from the production center of the materials. The results obtained in this paper are useful for defining the suitable use of each calcined material and for optimizing the concrete mix design based on its advantages and properties.

This paper studies the impact of splitting tensile properties of fly ash concrete with a split Hopkinson pressure bar device. Three different water-cement ratios (0.45, 0.55, and 0.6) and six different fly ash contents (0%, 5%, 10%, 15%, 20%, and 30%) were designed in the experiment. Both quasi-static and impact tests were conducted to study the influence of strain rate, water-cement ratio, and fly ash content on the dynamic mechanical properties of concrete. The test results show that the dynamic splitting tensile strength and dynamic incremental factor of fly ash concrete have an obvious strain rate enhancement effect. Under impact load, the dynamic splitting tensile strength of fly ash concrete with a water-cement ratio of 0.45 and 0.6 achieves its maximum value when fly ash content is 10%, and that of fly ash concrete with a water-cement ratio of 0.55 achieves its maximum value when fly ash content is 5%. Finally, the constitutive model considering dynamic damage was established to fit the test curve. The results show that the constitutive model has a good fitting effect on the test curve.

In this study, the mixes prepared using crumb rubber (CR) and binders with warm mix additives were aged through various aging methods (1, 2, 3, and 4 weeks at 60°C in the laboratory; 2, 4, 6, 8, 10, and 12 months under the environmental conditions; and AASHTO R30) and examined in terms of performance and aging index. The indirect tensile strength (ITS), indirect tensile stiffness modulus (ITSM), and fatigue tests were applied to the pure and the CR, $\mathrm{CR}+\mathrm{Sasobit}$, and $\mathrm{CR}+\mathrm{Evotherm}$ modified aged and nonaged mixes, and the aging indexes were determined according to the results obtained. According to the test results, $\mathrm{CR}+\mathrm{Sasobit}$ was found to be the best mix in terms of mechanical properties. Using the warm asphalt additives in the CR modification was determined to decrease the aging indexes and retarded the aging. Also determined was that a high correlation exists between the aging at 60°C in the laboratory and the aging under the environmental conditions. Based on the fatigue test results, AASHTO R30 short-term aging (4 h at 135°C) was determined to cause structural deterioration in the mixes and yielded low load repetition relative to the pure mixes. Therefore, using this method for the short-term aging of the CR modified mixes would not be appropriate. When the tests applied were evaluated in terms of the aging indexes, the fatigue test was found to be the most sensitive method for detecting aging in the pure mixes and mixes with additives.

The increased proportion of traffic volumes on roads is often the cause of distress to the pavement structure. The use of strong and durable steel slag (S) as an aggregate material in asphalt concrete can enhance the load-bearing capacity while at the same time conserving natural resources, resulting in a sustainable asphalt pavement system. This research evaluated the feasibility of using S to replace natural limestone (L) at various aggregate sizes in asphalt concrete. The measured performance of the L-S asphalt concretes was compared with that of L asphalt concretes and granite (G) asphalt concretes. Two types of asphalt cements, Penetration Grade AC60/70 and polymer-modified asphalt (PMA), were utilized in this research project. The mix proportions were prepared by separating each original aggregate (S, L, and G) into four bins, Bin 1 ($<4.75\mathrm{mm}$), Bin 2 ($<12.50\mathrm{mm}$), Bin 3 ($<19.00\mathrm{mm}$), and Bin 4 ($<25.00\mathrm{mm}$), and trial mixing them together. Five types of aggregate included L:L:L:L, L:G:G:G, L:S:S:S, L:L:S:S, and L:L:L:S, where the first, second, third, and fourth letters denote the types of aggregates in Bins 1–4, respectively. The asphalt concretes were prepared at 4% air voids using the Marshall compaction method. The performance tests included indirect tensile, fatigue life, resilient modulus, dynamic creep, and wheel tracking tests. S was found to improve the Marshall stability properties of the asphalt concrete by a maximum of 50%. The fatigue life, resilient modulus, and rut depth resistance of the L:S:S:S-AC60/70 were found to be 1.6, 1.4, and 1.4 times higher than that of L:L:L:L-AC60/70, respectively. The fatigue life and resilient modulus values of the L:S:S:S-AC60/70 concrete were found to be close to those of L:L:L:L-PMA concrete. The performance of L:S:S:S-AC60/70 concrete was found to be comparable to that of the costly L:L:L:L-PMA concrete, and had a longer service life than L:L:L:L-AC60/70 concrete with the same thickness. The research outcomes of this study will promote the use of S as a sustainable aggregate for pavement concrete construction.

In this work, the discrete-element method was used to simulate crack propagation in asphalt concrete in two types of laboratory tests: the disk-shaped compact (DCT) test and the single-edge-notched beam (SEB) test with the three-point bending technique. The heterogeneous models were numerically simulated using the clump technique to represent the shapes of the aggregate, the particle size distribution, and the air voids in the asphalt concrete mixture. The overall mechanical behavior and the fracture propagation were simulated by the cohesive zone model, in the potential fracture area, and the viscoelastic Burger’s model, in the remaining region of the samples. To obtain the values of the micro parameters required for the discrete-element model, a trial and error process was carried out comparing the mechanical behavior observed when considering the macro parameters of the asphalt concrete determined in laboratory tests. The numerical and experimental results are in good general agreement.

Efforts have been made in the recent past to enhance the strength properties of reclaimed asphalt pavement (RAP) concrete via inclusions of supplementary cementitious materials (SCMs), but only some of the durability problems could be rectified. In this study, an attempt is made to improve the performance of a roller compacted concrete pavement (RCCP) matrix containing 50% combined RAP fraction (R50 mix) by adopting a nontraditional methodology, i.e., including SCMs in additions of portland cement. The studied SCMs were silica fume (SF), fly ash (FA), and bagasse ash (BA). The results indicated that inclusions of all the SCMs (except BA) would not affect the fresh properties of R50 mix to a great extent but could degrade the quality of RCCP considerably. Microstructural analysis confirmed that asphalt cohesion failure is mainly associated with RAP mixes, with or without SCMs, and therefore, attempts to enhance the performance of RAP concrete would not be possible without removing the asphalt film. Interestingly, the considered mixes demonstrated higher flexural strength than the permissible ACI 325.10R-95 (ACI 2001) limit of 3.67 MPa for pavement application. Also, the SF and BA mixes exhibited better durability properties, in fact, better than the reference conventional mix, in terms of abrasion resistance and resistance to aggressive sulfate and chloride ions, indicating their suitability, especially in regions of aggressive ions and high-speed moving vehicles.

This paper presents the results of a laboratory study on evaluating the behavior of highly expansive clay that was treated with copper slag and lime under static and cyclic loading. The copper slag, obtained as a by-product from the smelting and refinery process of copper, was used as a stabilization agent in this study. In order to stimulate the pozzolanic activity of the copper slag, hydrated lime powder was used as a supplementary additive. Comprehensive laboratory tests including Atterberg limits, free swell, California bearing ratio (CBR), and unconfined compressive strength (UCS) tests were carried out to study the behavior of the clay treated with different proportions of copper slag and lime in the admixture content. Morphological change of soil after the stabilization was analyzed using the X-ray diffraction test. The optimum quantity of admixture was decided based on the CBR and UCS test results. Based on the strength criterion, the optimum stabilizer content that resulted in maximum strength improvement was found, i.e., copper (Cu) slag and lime at a $1:1$ proportion forming 12.5% admixture content by weight. The results of X-ray diffraction (XRD) test indicated substantial changes in the soil structure over the curing period. The stabilized soil samples were also subjected to dynamic loading to determine their dynamic properties. The study shows that the use of copper slag and lime for stabilizing expansive soil not only improves its static properties by reducing swelling and increasing the shear strength, but also increases its dynamic properties. Further, the behavior of the stabilized soil under fatigue load was analyzed by measuring the resilient modulus. The results have shown that the clay soil when stabilized with 12.5% admixture (Cu slag + lime at $1:1$) resulted in an increase in dynamic shear modulus of about 30%, a decrease in damping ratio of about 56%, and increase in resilient modulus of about 104%, proving the enhanced dynamic behavior of the soil.

The objective of this study was to evaluate the effect of an innovative UV light-activated self-healing polyurethane prepolymer (SPP) on the rheological, mechanical, and self-healing properties of asphalt mixture. This new additive combines polymer modification and self-healing capability into one modifier in order to enhance the mechanical properties of asphalt mixture, while increasing its crack healing rate. For this purpose, asphalt mixtures were prepared with asphalt binder modified with three percentages (5%, 10%, and 15%) of self-healing polyurethane prepolymer. A self-healing test was performed to evaluate the rate of crack healing in asphalt mixtures prepared with or without self-healing polyurethane. Furthermore, a Semi-Circular Bending test and a Loaded Wheel Tracking test were conducted to study the fatigue and rutting resistances of the prepared samples. Asphalt binder was also extracted from the samples and was tested using the dynamic shear rheometer and bending beam rheometer. An increase in the crack healing rate was observed with 5% and 10% self-healing polymer; however, when the SPP percentage was increased to 15%, the healing efficiency was affected adversely. The addition of SPP also led to an improvement in the cracking and rutting resistances. Results from the rheological test showed that SPP resulted in an increase in the high-temperature grading while the low-temperature grading was not affected. Furthermore, multiple stress creep recovery test results showed an improvement in the elastic recovery and rutting resistance of the binder extracted from aged and unaged asphalt mixtures.

This study investigates the mutual effects of binding and pretreatment procedure (coating) on the structural performance of textile-reinforced concrete (TRC) composite beams under flexural loading. The goal is to choose an optimal reinforcing textile configuration that yields a better design of the textile performance. The investigation was performed by correlating between the microstructural mechanism, which is associated to the textile configuration, and the macrostructural response according to various structural parameters, such as the ultimate load, the relative structural ductility, and the equivalent fracture energy. An experimental investigation is presented on four different binding types of warp-knitted structures: pillar and counterlaid tricot, characterized by relatively circular roving cross section, and plain and tricot, characterized by elliptical roving cross section. Each type was investigated in uncoated configuration and by coating with 50% styrene-butadiene rubber (SBR). In total, 32 TRC beam specimens were designed, cast, and monotonically loaded. Results demonstrated that generally the type of binding is significantly pronounced in uncoated textiles and that coating considerably improves the structural performance of all types of textile binding. It is also concluded that relatively flat and elliptical cross-sectional areas of the rovings are preferable in the case of uncoated textile, while in the case of coated textile the preferable binding configurations are the ones characterized by a relatively circular roving cross section.

Hollow concrete blocks can be thermally improved either by modifying their cavities shapes or by adding insulation materials into these cavities. It is also possible to improve the thermal conductivity of solid concrete matrix by incorporating some materials to its composition like recycled solid wastes for example. This paper offers a solid and comprehensive study for thermally improved hollow blocks through a case study from the Lebanese context and provides a scientific basis for improving the thermal performance of these blocks. The effect of adding expanded polystyrene (EPS) beads to the concrete solid mixture was investigated in this study through numerical and experimental approaches. The experimental and numerical results were in good agreement and the potential thermal improvement by adding EPS beads to concrete mixture was examined on both numerical and experimental levels. The numerical results for the three-dimensional (3D) model allow the visualization of the heat flux and temperature distribution in the block as well as the air velocity and convective heat exchanges inside the cavities of the block. The results showed that the block thermal resistance can almost double by adding 18 g of polystyrene beads to the concrete mixture.

In order for the concrete industry to become more efficient and sustainable, there is an urgent need to reduce emissions of carbon dioxide (${\mathrm{CO}}_2$) from cement manufacture. The innovative scheme described here for the linked production of cement and concrete with a low-carbon footprint follows a three-stage process. First, a Portland-like cement composition is calcined at reduced temperature and cooled under controlled conditions so that it self-pulverizes spontaneously to a powder of normal fineness without grinding. Second, ${\mathrm{CO}}_2$-rich gas is extracted directly from the cement kiln flue and used to activate this poorly hydraulic cement by carbonation in the third stage for making precast concrete products. The feasibility study described here aims to provide proof of the principle of this scheme. Considerable energy savings and sustainability gains are anticipated, and the challenges of process enhancements and scale-up are currently being addressed. In addition to its use in precast concrete items such as blocks, roof tiles, and pipes, other potential on-site applications are foreseen for this cement where low-carbon concrete or controlled setting are required.