Journal of Materials in Civil Engineering

The development trend of building materials science directs at on energy and resource conservation, as well as the creation of green composites. An important step in this direction is the disposal of waste of various origins, including mine waste. This study is aimed to improve the hardened properties of nonautoclaved silicate materials using nanodispersed mine waste for the use of the structural formation of wall silicate products. Binder composites obtained from sand-clay rocks of an incomplete stage of clay formation were prepared in the form of new compositions, using a modified calcareous-sandy-clay binder, based on which silicate products with improved strength properties and durability characteristics were developed. Using differential thermal analysis (DTA) and X-ray diffraction patterns, as well as scanning electron microscopy images, the synthesis of hydration products in the system sandy clay rocks–calcium hydroxide–water without a traditional autoclave treatment was also studied. The features of hydration phase formation and hardening of modified binders were investigated taking into account the chemical, structural, and morphological features of sandy-clay rocks. Meanwhile, the microstructural, morphological, and thermal properties of the silicate materials at 2-day were also determined, and their work investigated their compressive strength and water absorption. The results show that the polymineral composition of the studied sandy-argillaceous rocks, which are nanodispersed mine waste, determines the possibility of interaction with quicklime with the formation of binders during hydrothermal treatment without pressure. Accordingly, it contributes to the production of low energy consumption silicate wall materials. Cementitious composites of unautoclaved silicate materials based on sandy clay rocks have hydraulic properties that are caused by the process of further formation and recrystallization of calcium hydrosilicates, which optimizes the ratio between gel and crystalline components and compacts the structure of the cementitious composites, which leads to an increase in performance. The use of sand-clay rocks instead of traditional quartz sand in the production of silicate materials improves the process of forming the raw mix, increases the strength of silicate products by 4–11 times, and optimizes the weather resistance of wall materials.

Laboratory performance testing of the phase angle of asphalt concrete (AC) mixtures is often expensive and requires enormous human effort and time. To circumvent this problem, several regression-based methods have been proposed in the literature to model the phase angle behavior of AC mixtures using various approaches. However, these methods impose strict assumptions on the underlying relationship between phase angle and its corresponding covariates as well as how well and accurately these covariates are measured, restricting us from fully analyzing the predictive capability of any modeling method. To this end, this study proposed an alternative approach for modeling the phase angle characteristics of AC mixtures based on a recurrent neural network (RNN) that inherently and implicitly captures the effects of covariates. This approach is suitable to model the sequential nature of data recorded in laboratory testing where phase angle testing was repeated for a set of six loading frequencies forming a recurrent pattern. The proposed RNN model (P-RNN) was applied separately to wearing and base course mixtures by considering the historical values of phase angle as input and to predict its value for the next loading frequency, keeping temperature as a constant. To demonstrate the superiority of the proposed approach, the P-RNN model is compared with other competing models from the literature, and the results reveal superior performance of the P-RNN model.

The present study investigates the use of bacteria (namely, Sporosarcina pasteurii) to enhance the durability of structural concrete members with lightweight weight aggregates (LWAs) or normal weight aggregates (NWAs). As an innovative development, bacterially-induced calcium carbonate crystals have been widely used for improving the properties of concrete materials. In this research, seawater is used as a source of calcium and chloride for calcium carbonate formation by bacteria, whereby seawater serves as a curing environment with beneficial effects on both concrete matrix and durability. For this study, concrete specimens are cured in the two seawater and tap water environments up to the test time. Experimental results indicate that the inclusion of bacteria in the concrete mix water leads to acceptable results in seawater medium and both types of concrete tested. This is evidenced by a decrease of 4% in water absorption and an increase of almost 26% in compressive strength observed in normal-weight aggregate concrete after 91 days of curing. Moreover, both types of concrete made with bacterially-impregnated mix water exhibit reductions in their chloride penetration. In this regard, compared with the control specimens cured in plain water, the bacterially-treated LWA concrete specimens exhibited a reduction of almost 1% in their water absorption and a rise of about 16% in their compressive strength. It is, therefore, expected that exposure to seawater as a threat to concrete structures can be turned into an opportunity for improving their properties if the concrete is properly treated with bacteria.

To examine the uniaxial behaviors of plain concrete and lightweight aggregate concrete under dynamic loadings, the plain concrete specimens and lightweight aggregate concrete specimens prepared by shale ceramsite were designed and tested under the loading strain rate range of ${10}^{-5}/{\mathrm{s}–10}^{-2}/\mathrm{s}$. The hydraulic servo machine and shear device were applied to conduct the uniaxial compression, splitting tensile, and shear tests of both types of concretes, and the failure modes and stress-strain curves of two concrete at varying loading conditions were obtained from the test results. By comparing and analyzing the test results, the following conclusions are obtained: the failure of cementing layer occurs in plain concrete at low strain rates, while some coarse aggregates are damaged at high strain rates, but the failure of lightweight aggregate concrete is caused by the fracture of shale ceramsite at all strain rates. As the loading strain rate increases, the uniaxial compressive strength, splitting tensile strength, and shear strength of plain concrete and lightweight aggregate concrete are significantly increased, with the improved percentages of 35.63%, 43.75%, and 41.29% for plain concrete and 44.87%, 55.97%, and 49.44% for light aggregate concrete, respectively. For both types of concrete, the increase of strain rate has a more significant effect on the increase of splitting strength than compressive strength. In addition, the strain rate effect on the strength of lightweight aggregate concrete is significantly higher than that of plain concrete. The dynamic increase factor of peak stress of both concretes under uniaxial loadings is linearly related to the dimensionless logarithmic values of the strain rate. Based on the test results and analysis, two different relationship expressions between compressive strength, splitting tensile strength, and shear strength of two types of concretes are proposed, and the dynamic effects of concrete are explored from the perspective of the damage mechanism. This study is meaningful to the engineering applications and development of plain concrete and lightweight aggregate concrete.

The objective of this paper is to to ascertain the reliable mechanical properties of cold-formed Q345 steel at elevated temperatures while considerting the effects of tensile strain rate and specimen width. This paper presents an experimental study on the mechanical properties of cold-formed Q345 steel at temperatures ranging from 20°C to 800°C tested with two specimen widths and three tensile–strain rates, namely $0.06/\min$, $0.6/\min$, and $1.2/\min$. Tensile specimens were fabricated from a steel plate with a nominal thickness of 2.5 mm and tensile tests were carried out to determine the stress–strain relationship, yield strength, tensile strength, and elastic modulus. The test results showed that the tensile–strain rate has a maximum influence of 9% on yield and tensile strength at 600°C and the specimen width has a maximum influence of 14% on yield and tensile strength at 400°C. The maximum influence of the tensile–strain rate and specimen width on the elastic modulus is 18% and 12% respectively at 500°C. The necking phenomenon is less noticeable at temperatures below 300°C but is clearly observed at temperatures above 300°C. The comparison of the test results with predictions obtained from design standards (EC3, AISC, and AS4100) indicates a good agreement on the yield and tensile strength, but the magnitudes of elastic modulus obtained from the test are considerably higher than those obtained from the design standards. Based on averaged values of the test results associated with different tensile–strain rates and specimen widths, predictive equations were proposed to determine the mechanical properties of cold-formed Q345 steel at elevated temperatures.

In this work, the influence of a dolomite filler, in combination with pulverized fly ash, on the sulfuric acid (${\mathrm{H}}_2{\mathrm{SO}}_4$) resistance of alkali-activated slag (AAS) is studied. The evolution of compressive strength and mass loss, as well as mineralogical, compositional, and molecular structural alteration of hardened AAS binders containing 0%, 20%, and 40% dolomite filler, or a combination of 20% dolomite and 20% fly ash, exposed to 0% (deionized water), 1%, 2.5%, and 5% ${\mathrm{H}}_2{\mathrm{SO}}_4$ solutions, are investigated. The results show that the dolomite and fly ash incorporation in AAS pastes exacerbates the alkalis leaching and alkalinity loss and tends to enhance the strength loss in the ${\mathrm{H}}_2{\mathrm{SO}}_4$ solutions, likely due to a coarsened pore structure and, thus, enlarged permeability. Under the ${\mathrm{H}}_2{\mathrm{SO}}_4$ attack, AAS is decomposed into gypsum, glauberite, and amorphous calcium-magnesium aluminosilicate hydrates, with little thaumasite, ettringite, or magnesium-bearing mineral formations. While decalcification and the silica polymerization of gel products take place in AAS upon an acid attack, it has strong dealumination resistance. In low and intermediate acid concentrations, the dolomite incorporation reduces the amount of gypsum and glauberite formed in AAS due to the dilution effect, while in strong acid media, dolomite dissolution occurs and contributes to the deleterious sulfate minerals formation.

Research on the usage of industrial by-products to improve mechanical properties of low-quality materials in infrastructure applications is of global interest. Two industrial by-products, namely, fly ash (FA) and asphalt emulsion (AE), were used in this research to develop an FA-AE stabilized marginal crushed rock (CR) as a sustainable pavement base material. A liquid alkaline activator was used, comprised of a mixture of sodium hydroxide (NaOH) and sodium silicate hydrate (${\mathrm{Na}}_2{\mathrm{SiO}}_3$) at ${\mathrm{Na}}_2{\mathrm{SiO}}_3:\mathrm{NaOH}=50:50$ and NaOH concentration = 5 M. In this research study, the mechanical properties of FA-AE stabilized CR were investigated via unconfined compressive strength (UCS), indirect tensile strength (ITS), flexural strength (FS), indirect tensile resilient modulus (IT $M_r$), and indirect tensile fatigue life (ITFL) tests. The UCS of FA geopolymer stabilized CR (without AE) was found to be dependent on the FA content and curing time. For all the curing times studied, the higher FA replacement ratio resulted in higher UCS values. Although the asphalt film enhances particle confinement, it was found to retard the geopolymerization reaction. According to the local road authority, which requires a $\mathrm{UCS}>1.75\mathrm{MPa}$ for a stabilized base course, the addition of AE reduced the UCS of FA-AE geopolymer stabilized CR. To meet the minimum 7-day strength requirement for both low and high-traffic roads, a geopolymer mix was suggested with an FA replacement $\mathrm{ratio}\ge 20\%$ and an $\mathrm{AE}\mathrm{content}\ge 1\%$. Compared with the cement stabilized CR at a similar UCS value, the FA-AE geopolymer stabilized CR had higher FS, ITS, IT $M_r$, and ITFL but lower carbon footprints.

To investigate the compaction characteristics of a single-component polyurethane (PU) mixture with dense gradation, the effects of temperature, humidity, catalyst content, and standing time on the compaction energy index (CEI) of the mixture were analyzed in this study. The air void ratio and splitting tensile strength of the polyurethane mixture at 15°C under different compaction times were also tested. Based on the test results, the effects of compaction time on the volume and strength characteristics of the polyurethane mixture were analyzed. The results showed that temperature, humidity, catalyst content, and standing time have significant positive correlations with the CEI, where standing time has the strongest correlation, followed by catalyst content, temperature, and humidity, respectively. A multiple linear regression model relating the CEI and the aforementioned factors was established. Compaction time, as characterized by the CEI, significantly influenced the air void ratio and splitting strength of the polyurethane mixture after curing. If the compaction of the polyurethane mixture is premature or delayed, the void ratio of the mixture increases after curing and the splitting strength decreases. Therefore, an optimal compaction time exists for the single-component polyurethane mixture. At this compaction time, the CEI of the mixture is approximately 600–800. During the process of single-component polyurethane curing, the increase in the adhesive force of polyurethane and the damage to the structure of the mixture, caused by the released ${\mathrm{CO}}_2$, served as a pair of mutually restricting effects, resulting in different volume characteristics and splitting strengths of the polyurethane mixture under different compaction times.

Engineered cementitious composite (ECC) is a relatively recent construction material with characteristics of high ductility and energy dissipation capacity. Such ductility is fulfilled by adding polymeric fibers, such as polypropylene (PP), polyethylene (PE), and polyvinyl alcohol (PVA) fibers, which would inevitably experience fusion under fire. This paper focuses on the behavior deterioration of postexposure high-strength engineered cementitious composite (HSECC). Color change, surface cracking, and spalling phenomena of HSECC specimens were inspected after specimens exposed to 200°C, 400°C, 600°C, 800°C, and 1,200°C for 1 h. Weight loss, residual compressive/flexural strength, and failure modes of cubes were evaluated correspondingly. Experimental results indicated that the threshold temperature for HSECC to crack is lowered in comparison with ECC of normal strength, whereas explosive spalling behavior could still be prevented effectively with 2.0 vol% PVA fiber. The loss ratio of weight and strength in HSECC was lower than that in ECC, but the failure modes under compression were found to be more catastrophic. HSECC exhibits lower intensity in an X-ray diffraction (XRD) curve than that of ECC. Apparent needle-like channels were observed beyond 400°C, then were gradually filled with reaction products ascribed to the synergistic effect of thermal expansion, volume increase caused by chemical reactions and pore-structure coarsening, and manifested by the results of mercury intrusion porosimetry (MIP).

Soluble alkalis play a vital role during early age hydration and strength development in cement. This study investigates the influence of alkali addition on the hydration, phase assemblage, and strength development in ordinary portland cement (OPC) and limestone–calcined clay cement (${\mathrm{LC}}^3$) produced with 50% clinker replacement. The alkalinity (% ${\mathrm{Na}}_2{\mathrm{O}}_{\mathrm{eq}}$) of OPC and ${\mathrm{LC}}^3$ was increased using four different alkali salts: NaOH, ${\mathrm{Na}}_2{\mathrm{SO}}_4$, KOH, and ${\mathrm{K}}_2{\mathrm{SO}}_4$. An acceleration of the early age hydration and an increase in the early age compressive strength development was observed with increasing alkalinity in OPC and ${\mathrm{LC}}^3$ systems. The characteristic features of the calorimetry curves were seen to be significantly influenced by the presence of alkalis. The presence of additional sulfate ions was seen to modify the phase assemblage, with additional ettringite forming in these systems. However, increasing the alkalinity was also seen to reduce the later age clinker hydration and strength development.

This paper aims to determine the resistance of a wide range of building materials against projectile penetration using the depth-of-penetration (DOP) test and several well-established ballistic factors. Within the DOP test, the residual penetration into a backing aluminum alloy cylinder after passing through a sample with a defined thickness and bulk density was measured. The materials investigated here were plasters, mortars, autoclaved aerated concretes (AAC), normal-strength concretes (NSC), ultrahigh-performance concrete (UHPC), full fired-clay brick (FCB), granite, basalt, laminated glass, and ice. The findings show that the ballistic efficiency factors depend substantially on the material used, allowing one to identify materials with different levels of penetration resistance. Inferences drawn from this study can be used by engineers, architects, and contractors to assess the perforation resistance of various building materials to optimize their use against high-speed projectile impact. In addition, it is demonstrated that the uniaxial compressive strength of the building material might be misleading as the identifier of a material resistance against projectile impact because a significant difference in penetration resistance between materials with comparable compressive strength was found.

The adhered mortar attached on the surface of recycled aggregate is the primary difference between recycled aggregate and natural aggregate, and is the major reason for reducing its mechanical properties. To measure the percentage of adhered mortar, an image analysis method (IAM) was presented. First, three comparative specimens were conducted to demonstrate the precision and efficiency of IAM. Further, the actual adhered mortar content was also studied by the heating and cooling method. Then, the effect of recycled aggregate size on the percentage of adhered mortar, and the characteristic of recycled aggregate was explored by IAM. In addition, the type and optimal size of recycled aggregate were also investigated. The obtained data indicated that IAM is an accurate and efficient method to measure the proportion of adhered mortar or other phases; the highest content of adhered mortar was found in recycled aggregate with a size of 10.0–16.0 mm, up to 39.39%; the percentage of the recycled aggregates with a particle size between 16.0 and 20.0 mm should be increased in the mix proportion, which has less adhered mortar content and higher quality recycled aggregate content.

Due to greater durability and lower maintenance costs, concrete pavements are more competitive than asphalt pavements in areas where rigid pavements are required. To ensure the surface skid resistance of concrete pavement for driving safety, appropriate textures must be created on the concrete pavement surface. Common surface texturing treatments in Germany include exposed aggregate, grinding and grooving, and sealing methods. To investigate the influence of different surface texturing methods on the wearing resistance of concrete pavement, concrete pavement samples with six different surface textures were manufactured in this study. The advanced Aachen Polishing Machine (APM) was used to simulate the different polishing states on the extracted samples with 0, 16, 33, 100, 200, and 300 min of real-tire polishing effect. After each polishing stage, a series of surface characteristic tests was conducted to evaluate the wearing characteristics of pavement samples. The test results showed that different surface textures have different long-term polishing resistances. Of the texturing methods investigated, the exposed aggregate and sealing treatments provide the best long-term polishing resistance for plastic and hardened concrete, respectively. This research provided a comprehensive evaluation of and significant guidance on the selection of surface treatment methods for new construction of cement pavement and surface maintenance of hardened concrete pavement.

The influence of sand particles, aging, and water–cement (w/c) ratio on the viscoelastic relaxation modulus of cement paste and mortars was measured at early ages (1–28 days). Furthermore, the relaxation modulus obtained approximating the strain state as constant or obtained considering the real strain history observed during testing were compared; significant error was encountered when a constant strain was assumed. In contrast, little error was introduced when aging during the relaxation experiments was neglected, which is likely due to the relatively short duration of the experiments and the nonconstant strain history that led to rapid stress decay. In contrast to conventional wisdom, lower w/c samples loaded at very early ages exhibited similar relaxation to higher w/c samples; however, at later ages, lower w/c materials exhibit lower relaxation rate. For samples loaded at later ages, the similarity between the shape of the relaxation curves for samples containing differing sand content and w/c suggests a method to simply quantify the effects by shifting the spring constants in a Kelvin–Voigt or Maxwell-type model.

The present work is an attempt to explore use of recycled concrete aggregate (RCA) to replace natural aggregates (NA) in a sustainable way in stone matrix asphalt (SMA) mixes used as a rut resistant bituminous layer. Based on several initial trials, a modified pretreatment procedure has been developed, which involves mixing of RCA with 8% (by weight) nanosilica modified bitumen emulsion solution followed by 24-h curing. The treated RCA (TRCA) has been used as coarse aggregate completely replacing the coarse NA, with two different types of bitumen namely, VG 30 and VG 40 bitumens for preparation of SMA mixes. Marshall method was used to determine optimum bitumen content (OBC) of the respective mix type. The pertinent performance characteristics such as stone-on-stone contact, drain-down, Marshall parameters, indirect tensile strength, moisture susceptibility, resilient modulus and rutting potential have been addressed for various SMA mixes prepared at respective OBCs. It is concluded that TRCA as aggregate and VG 40 bitumen as binder in SMA mix contributed to the best results in terms of various performance parameters considered.

Production of alkali-activated binders is a developing research field that utilizes industrial/agricultural by-products and solid waste for the development of sustainable concrete. This paper comprehensively reviews the literature relating to rice husk ash (RHA)–based alkali-activated binders incorporating fly ash (low/high calcium) and blast furnace slag. The literature demonstrates that the properties of raw material significantly influence the formation of the alkali-activated gel matrix. Every precursor (low/high calcium fly ash and slag) that is used to develop alkali-activated binders with RHA have their own reaction mechanism dependant on their specific chemical composition. Hence the incorporation of RHA influences each binder in a unique way depending upon the alkali activation process and reaction mechanisms. The incorporation of RHA, in the range 5%–15%, with blended slag alkali activated binders, yields better compressive strength, when compared with RHA blended with fly ash (low/high calcium). The review presented in this paper is very useful to understand the behavior of alkali-activated binders incorporating RHA and in advancing the research into the successful application of RHA as a binder for alkali-activated materials.

An asphalt-binder is one of the key constituent elements that significantly influences and controls the fracture behavior and cracking performance of hot-mix asphalt (HMA). In particular, the low-temperature rheological properties of asphalt-binders are critical in terms of improving the HMA fracture properties in the laboratory and ultimately mitigating cracking in the field. The bending beam rheometer (BBR) is one of the most widely used laboratory test methods for evaluating and quantifying the asphalt-binder behavior at low temperatures, mostly using the stiffness (S) and m-value parameters. Using the Texas flexible pavements and overlays database, namely, the Texas data storage system (DSS), as the primary data source, this study was conducted to correlate the asphalt-binder low-temperature rheological properties (measured using the BBR) to the HMA fracture properties. The HMA fracture properties were measured in the laboratory using the monotonic-loading overlay tester (ML-OT). In general, the asphalt-binder low-temperature rheological properties [particularly the stiffness (S)] exhibited promising potential to predict the HMA fracture properties, namely, the tensile strain (${\epsilon }_t$) and fracture energy index ($FE$ Index), with a coefficient of determination ($R^2$) greater than 60%.

This study investigates the effects of raw sugarcane bagasse ash (SCBA) used as a partial or complete replacement for silica sand in engineered cementitious composites (ECCs). ECC mixtures with five different replacement levels of sand with SCBA were produced (i.e., 0%, 25%, 50%, 75%, and 100% by volume). The SCBA utilized in this study was comprehensively characterized. Furthermore, the fresh and hardened properties of the produced ECC materials were thoroughly evaluated. The characterization of SCBA revealed that raw SCBA consisted mainly of small (i.e., 256 μm average particle size), porous, and irregularly shaped particles with carbon and silica as the main constituents. Furthermore, the SCBA met the pozzolanic component requirement for Class C pozzolans; however, it did not meet the minimum strength activity index requirement to be classified as a pozzolan; however, it did not meet the minimum strength activity index requirement to be classified as a pozzolan. In terms of ECC fresh properties, the incorporation of SCBA produced an important loss in workability, which was mitigated with increasing dosages of high-range water reducer for increasing amounts of SCBA, which also resulted in a substantial increase in the air content. In the case of hardened material properties, the incorporation of SCBA as sand replacement produced a slight decrease (up to 11%) of the compressive strength of ECCs. However, the tensile strength and especially the tensile ductility of the composites were substantially enhanced (up to 22.3% and 311%, respectively). The tensile strength improvements were credited to the pozzolanic and/or filler effect of SCBA. On the other hand, enhancements in the tensile ductility were associated to the combined effect of the reduction of crack-tip matrix toughness (credited to the decrease in aggregate particle size), reduction in ECC cracking strength (due to increase in air content), and increase in the complementary energy (attributed to the potential decrease in the chemical bond of the fiber/matrix interface and an enhanced fiber dispersion). The surface resistivity of ECC materials was negatively affected by the addition of SCBA. Furthermore, the length change of all SCBA-ECC materials, at all ages of curing, was higher in comparison with that of the control mixture, except for the mixture with 25% replacement at 28 days of curing.

Many studies have been carried out on the influence of freeze–thaw cycles on the mechanical behavior of cement- or lime-stabilized soils. However, very limited studies have considered the effects of freeze–thaw cycles on cement-stabilized soil reinforced with fibers. The main objective of this study is to determine the effects of polypropylene fiber (PPF) and basalt fiber (BF) content (0%, 0.5%, 1%, 2%, and 5%), cement content (0%, 3%, and 9%), number of freeze–thaw cycles (0, 2, 4, 8, and 10), and initial moisture content on the unconfined compressive strength (UCS) of clay soil. The study reveals that adding cement, PPF, or BF to soil causes a remarkable increase in strength, where the strength of the PPF-reinforced specimens is significantly more than that of BF-reinforced ones. The UCS values of the specimens compacted at optimum moisture content (OMC) are almost more than those that were prepared at a molding moisture content of 0.8 OMC or 1.2 OMC. The strength of specimens increases with increases in cement content and curing time. However, the axial strain at failure for cement-stabilized specimens decreased with increasing cement content or curing time. Furthermore, it is concluded that the increase in the UCS of combined PPF or BF with cement inclusion is more than that caused by each fiber without cement. A regression model is developed to predict the UCS in terms of four effective agents for each case of stabilization by BF or PPF. Results indicate a satisfactory performance of the model where the Pearson correlation coefficient above 0.95 for UCS prediction is obtained.

Understanding the long-term creep behaviors of asphalt concrete core materials is crucial to the safety of embankment dams. This study systematically analyzes the creep behavior of asphalt concrete materials under a stepped loading path. Static triaxial tests are conducted to determine the stress–strain relation of asphalt concrete core materials. Both stepped loading and separate loading paths are applied on the asphalt concrete samples to analyze the difference between them in terms of the axial strain. To simulate the realistic temperature condition during the operation of dams, the temperature is set to 22.1°C. The test samples are subjected to four confining stresses (i.e., 0.1, 0.4, 0.7, and 1.0 MPa), and the stress levels are 0.2, 0.4, 0.5, and 0.8. For processing the test data obtained under the stepped loading path, the Boltzmann superposition method and Chen’s method are applied. Then, the Burgers model is applied to estimate the stress and strain behaviors of the asphalt concrete materials. The results indicate that asphalt concrete materials characterize in primary and secondary creep stages. The data processed by Chen’s method is much closer to the data of separate loading path than those processed by the Boltzmann method. The Burgers model describes well the creep behavior of the asphalt concrete materials. Thus, it can be applied in the estimation and analysis of the creep behaviors for embankment dams under long-term operation.

Photocatalytic pavements materials are being developed to purify toxic automobile exhaust gas, especially in tunnels where the pollution concentrations are high. This study investigated the photocatalytic efficiency and pavement performance of asphalt mixtures containing steel slag and different contents of ${\mathrm{CeO}}_2$ and ${\mathrm{TiO}}_2$ as photocatalyst materials. Photocatalytic testing equipment was developed to calculate the photodegradation efficiency for CO, ${\mathrm{CO}}_2$, NO, and HC. The pavement performance of the asphalt mixtures was evaluated using rutting tests and low-temperature bend tests. The texture depth was measured to evaluate the antislide performance. The excessive addition of the ${\mathrm{CeO}}_2$ and ${\mathrm{TiO}}_2$ nano photocatalysts had an adverse effect on the pavement performance of the steel slag asphalt mixture. The optimal contents of ${\mathrm{CeO}}_2$ and ${\mathrm{TiO}}_2$ were 7% and 0.6% by weight of the asphalt binder weight, respectively, as obtained by a gray target decision process based on principle component analysis. These findings are expected to contribute to the development of functional pavement materials that improve the surrounding air quality and have a lower environmental impact due to the use of waste slag.

The effect of polyaluminum chloride (PAC) on the durability, microstructure, and corrosion sensitivity of slag–cement pastes was investigated in this research. Various experimental tests were performed to assess the mechanical properties (compressive strength test), durability (rapid chloride migration test, water permeability test, capillary water absorption test, chloride binding test, accelerated carbonation test), microstructure (scanning electron microscopy, X-ray diffraction, mercury intrusion porosimetry), and corrosion sensitivity (accelerated corrosion sensitivity, initial chloride concentration). Experimental results showed that adding 1.5% PAC increased compressive strength by 77.0%, 53.8%, and 19.4% at 3, 7, and 28 days. Resistance to chloride migration, water permeation, capillary water absorption, and carbonation was improved. These results were consistent with the microstructural analysis, which showed that adding PAC facilitated the formation of Friedel’s salt and development of pore structure, which was the key factor for the improved durability of the slag–cement paste. Adding 1.5% PAC had a limited influence on the corrosion sensitivity despite introducing the additional chloride ions into the system. These results promote the further practical application of PAC.

Thermal backfill is essential for projects such as underground crude oil pipelines and crude oil storage tanks to control the heat migration from the source. The properties of locally available soil may not be adequate as thermal backfill and hence need suitable amendment. Biochar is a low thermal conductive material and may contribute to an increase in soil strength. There are no such studies that deal with the thermal properties of biochar-based backfill. Further, the influence of biochar particle size fractions on soil thermal properties has not been reported until now. Therefore, the possibility of biochar as a soil amendment for modifying thermal backfill characteristics is explored in this study. Two types of soils (highly plastic silt and clayey sand) are amended with three biochar content amounts (5%, 10%, and 15%), and three different particle size fractions [coarse (4.7–2 mm), medium (2–0.425 mm), and fine (0.425–0.075 mm)], and their compaction characteristics as well as thermal and mechanical properties are investigated. It was observed that the amendment of biochar in soil reduced the thermal and mechanical properties of the soil. Further, the reduction in soil thermal conductivity and volumetric heat capacity with biochar amendment was more in coarser biochar fraction than finer and medium fractions. In comparison, reduction in unconfined compressive strength (UCS) was more in finer biochar fraction. Additionally, the thermal properties reduction was higher in clayey sand than highly plastic silt. An inverse linear correlation of thermal conductivity with pH and electrical conductivity were observed for both soil biochar mixes. The relationship between the thermal properties and UCS indicates that the medium fraction biochar provides the optimized value for reducing thermal properties and UCS of biochar amended soil (BAS). This proves the efficacy of BAS as thermal backfill.

Owing to the lack of research for evaluating the effect of the aggregate profile on the chloride diffusivity of concrete, this paper presents a numerical scheme for predicting the chloride diffusivity of concrete with practical aggregates. Using Fourier series, practical aggregate models consisting of pixels are established. A computer simulation of the mesostructure of concrete with established aggregates is performed. A random-walk simulation for digitized media is introduced to solve the diffusion equation of chloride ions, and the chloride diffusivity of concrete is determined. To ensure both the simulation accuracy and the operating efficiency of the computer, the first-passage radius and the numbers of random walkers are determined. The accuracy of the numerical scheme is verified via a comparison with experimental results. Finally, the impact factors, e.g., the interfacial transition zone (ITZ) thickness and the aggregate content, shape, angularity, and surface texture, are quantitatively evaluated. The simulation results indicate that the chloride diffusivity is significantly affected by the ITZ thickness, aggregate content, and aggregate shape but is hardly affected by the angularity and surface texture of the aggregate.

At present, the rationality and applicability of various high-temperature performance evaluation indexes for polymer-modified asphalts have not been comprehensively explored. This study aimed to fully explore their rationality and applicability. For this purpose, five asphalt binders including four representative polymer-modified asphalts and one neat asphalt (NA) were chosen, and many of their high-temperature performance indexes were first obtained by using a series of tests. Then the five corresponding asphalt mixtures were fabricated and their high-temperature performance indexes were also obtained by performing a wheel tracking test. On this basis, the high-temperature potential of asphalt binders was evaluated using the obtained indexes, and the correlation between the indexes of asphalt binders and their mixtures was analyzed via data processing software. Results show that the rankings of high-temperature performance of these five asphalt binders are not exactly consistent when all the high-temperature performance indexes—including penetration ($P$) at 25°C, penetration index (PI), equivalent softening point ($T_{800}$), softening point (SP), dynamic viscosity (DV) at 60°C, rutting factor ($G^{*}/\sin \delta$), improved rutting factor $[G^{*}/(\sin \delta {)}^9]$, Shenoy’s nonrecoverable compliance ($J_{\mathrm{Shenoy}}$), critical temperature of rutting factor ($T_{G^{*}/\sin \delta }$), nonrecoverable creep compliance ($J_{\mathrm{nr}}$), creep modulus ($G_V$), zero shear viscosity (ZSV), and generalized dynamic shear modulus (GDSM)—are utilized for evaluation. However, all the indexes can distinguish the polymer-modified asphalts from NA well. Among these indexes, the evaluation results of $J_{\mathrm{nr}}$ at different temperatures are consistent at the same stress level (0.1 or 3.2 kPa), and all the correlation coefficients between the $J_{\mathrm{nr}}$ and dynamic stability (DS) of asphalt mixtures exceed 0.9; thus, the $J_{\mathrm{nr}}$ is recommended as the dominant evaluation index. The $G^{*}/\sin \delta$, $T_{G^{*}/\sin \delta }$, and $G_V$ correlate weakly with the DS, and the ZSV performs poor repeatability in the test; thus, their rationality needs to be further verified using more asphalt samples.

The shear behavior of coal-fouled unstabilized ballast and that stabilized with Elastan was assessed in direct shear mode at various normal stresses (${\sigma }_n$) and shearing rates ($S_r$). The materials used in the test were fresh granite ballast and coal fines of mean particle sizes ($D_{50}$) of 42 mm and 545 μm, triangular aperture geogrid, and Elastan polyurethane polymer with a density of $\mathrm{1,100}\mathrm{kg}/{\mathrm{m}}^3$. Test results indicated that the shear strength of both unstabilized and stabilized coal-fouled ballast is highly affected by the applied normal stress and shearing rate. The results further established the performance of ballast stabilized with Elastan to be significantly more enhanced than unstabilized ballast and that stabilized with geogrid. Furthermore, the results also confirmed that the shear strength of Elastan-stabilized ballast is highly influenced by the presence of coal fines. The friction angle ($\phi$) of coal-fouled Elastan-stabilized ballast reduces from 75° to 65° and dilation angle ($\psi$) from 19° to 8° as the void contamination index (VCI) increases from 0% to 45%. The performance index of Elastan-stabilized ballast, expressed as the ratio of shear strength of fouled ballast to the shear strength of fresh and unstabilized ballast, lies in the range of 1.60–1.29. The breakage of fouled ballast ($B_g$) was found to decrease owing to the addition of coal fines. Further, analysis of tested samples revealed that while geogrid reduced the particle breakage considerably, the Elastan treatment completely eliminated the breakage of particles.

The standard method of using a caliper to determine aggregate particle dimensions is not sufficient to describe the shape, texture, angularity, and volume of particles, and there is not a reference method to determine aggregate surface area. A three-dimensional (3D) structured-light scanner seems to be a viable and economical alternative with enough speed to obtain 3D data from hundreds of particles. This work used a 3D scanner to evaluate morphological properties of coarse aggregates and compared results with those from conventional techniques. Two types of aggregates (around 60 particles of each type) were scanned and manually measured by a single operator with a digital caliper using two different methodologies: (1) the minimum bounding box (MBB), and (2) a conventional standard test method (STD). The 3D structured-light scanner proved to be accurate for assessing the morphology, surface area, and volume of coarse aggregates, and with a processing rate of $10\min /\mathrm{particle}$, it was faster than other techniques such as X-ray computed microtomography (micro-CT) or laser scanning. Compared with the manual method (caliper) or the most commonly used two-dimensional (2D) image analysis techniques, it also was more accurate. The MBB using a caliper overestimated volume by about 17% and underestimated surface area by 11%, which was estimated by assuming an ellipsoid with the dimensions obtained. The 2D circularity had a poor correlation with the 3D sphericity, especially for flat or elongated particles.

Sugarcane agriculture contributes to the greenhouse effect by the polluting action of residue disposal, given that most sugarcane bagasse (SB) is burned. Because it is a low-cost fiber and ecofriendly material, SB can be an alternative to the construction of permeable friction course (PFC) pavement layers. Due to SB-specific properties, its effects on PFC mixtures are unknown. This study aims to evaluate for the first time the feasibility of incorporating SB fibers in a PFC mixture. For this purpose, a PFC mixture that included SB fibers (PFC-SB) was compared to a control PFC mixture fabricated using synthetic cellulose fibers (PFC-CEL), which are currently the most used fibers for fabricating these mixtures. The results suggest that the SB fibers can be successfully added to PFC mixtures to control binder draindown without compromising their volumetric properties. Additionally, the PFC-SB mixture presented an increase in stiffness and resistance to both cracking and raveling compared to the PFC-CEL. However, the mix design should be optimized to ensure proper mixture permeability. These findings suggest that the incorporation of SB fibers in PFC mixtures can be further explored, which encourages additional research.

Self-healing asphalt with encapsulated rejuvenators is a promising technology to improve the service life of asphalt pavements. Broken capsules reduce the viscosity of aged bitumen due to rejuvenator diffusion, sealing open microcracks at an early stage. Several waste oils have been used as low-cost rejuvenating agents in capsule production to reduce costs and enable the environmental benefits of this technology. This study aims to evaluate the effects of capsules containing waste vegetable oil (WVO) and waste mineral oil (WMO) on the mechanical properties of hot mix asphalt (HMA). Four capsule content amounts (0.25%, 0.50%, 0.70%, and 1.00% by weight) were included in HMA samples, which were evaluated through experimental standard tests such as stiffness modulus, indirect tensile strength, fatigue life, and moisture-induced damage. The results revealed that an increase in capsule content led to less rigidity and strength against permanent deformation and fatigue. It was also determined that the strength against permanent deformation of mixtures with WMO capsules increased more than that of mixtures with WVO capsules. Another finding is that the optimum capsule content ratio in asphalt mixtures is 0.50% by weight for both capsule types.

Two common test methods measure the surface energy of asphalt binders: the Wilhelmy plate method and the sessile drop method. In contrast to the sessile drop method, the Wilhelmy plate method introduces the influence of infiltration velocity. As a result, significant differences exist between the Wilhelmy plate method and the sessile drop method in determining the surface energy of the same asphalt binder, despite the fact that the surface energy of the asphalt is constant. To solve the problem caused by infiltration velocity, mathematical models were developed for test samples when the contact angle was obtuse, right, and acute, respectively, to determine the actual dynamic contact angles when considering the influence of infiltration velocity in the Wilhelmy plate method. Based on the relationship between the actual dynamic contact angle and infiltration velocity, a modified Wilhelmy plate calculation method is proposed. The measurements and analyses reflect that the modified Wilhelmy plate calculation method is capable of reducing deviation of asphalt surface energy measured by the Wilhelmy plate method and sessile drop method to less than 10%.

The objective of this experimental investigation is to use the ASTM C1138 (underwater) test method to investigate the influence of the quantity and type of coarse aggregates on the hydrodynamic abrasion resistance of concrete. Thereafter, relationships between the abrasion resistance of concrete with its principal mechanical properties are comparatively examined. It is found that the use of natural coarse aggregates to replace fine aggregates by up to 25% does not significantly affect concrete abrasion performance, but the use of recycled tire rubber aggregates with aspect ratios of $\sim 4$ to replace 25% of natural coarse aggregates increases the abrasion resistance by up to 64% depending on the test duration. Further, concretes produced with natural rounded coarse aggregates of 10 mm significantly outperformed those with angular 20 mm maximum particle size at all test durations by up to 57%. Finally, for the concrete mixtures tested, results indicate that tensile splitting strength is a superior parameter to compressive strength for predicting the concrete abrasion resistance in the ASTM C1138 test and the relations developed for the concretes tested predicted percentage abrasion loss within the margin of $\pm 0.5\%$.

This study aimed to evaluate the effects of additional antistrip additives on the durability and moisture susceptibility of granite-based open-graded friction course, referred to as FC-5 asphalt mixture. The laboratory testing involved two granite-based FC-5 mixtures containing 1% hydrated lime (by weight of aggregate), 1% hydrated lime plus 0.5% liquid antistrip (LAS) additive (by weight of asphalt binder), 1.5% hydrated lime, and 1.5% hydrated lime plus 0.5% LAS additive. Two sources of granite aggregates were obtained, one from Junction City, Georgia, and the other from a regional supplier with an original source from Nova Scotia, Canada. Four types of LAS additives were collected for this study. A binder bond strength test was used to select the LAS agents that provided the best improvement in moisture resistance. The FC-5 mixtures were fabricated in the laboratory using two FC-5 mix designs provided by the Florida DOT. The specimens were conditioned by the asphalt pavement weathering system to simulate long-term aging and moisture conditioning in the field. Mixture performance tests, including the Cantabro test, tensile strength ratio test, and Hamburg wheel tracking test, were used to evaluate the durability and moisture susceptibility of FC-5 mixtures. Finally, a cost-benefit analysis was performed to determine the cost-effectiveness of the FC-5 mixtures with antistrip additives. This study found that the addition of LAS additive, an extra 0.5% hydrated lime, or both produced longer lasting FC-5 mixtures, and the additional antistrip additives would improve the cost-effectiveness of FC-5 mixtures.

The reuse of high content of reclaimed asphalt pavement and reclaimed asphalt shingles in hot mixtures by adding recycling oils has attracted wide attention and interest in the paving industry. However, the aging property and the durability of oil recycled asphalt binders with reclaimed asphalt materials are not well understood. This study prepared 12 oil recycled asphalt binders with base binder, extracted binders from reclaimed asphalt pavement and reclaimed asphalt shingles, and three types of oils, including two bio-oils and one re-refined engine oil bottom oil. Multiple stress creep recovery and oscillation tests were performed to evaluate the rheological change with aging, and Fourier-transform infrared spectroscopy was used to track the chemical evolution. Aging performance of these blends was evaluated using the aging indexes. Results showed that the recovery and nonrecoverable creep compliance were highly related. The aging indexes of nonrecoverable creep compliance at 3.2 kPa and complex modulus indicated that adding oils may impair the durability of asphalt binders with reclaimed asphalt materials. However, the aging index of carbonyl suggested that the oils do not have much effect on the chemical reaction (oxidation). The correlating analysis indicated that rheological and chemical change had a good correlation relationship, but also showed material dependency.

The possible utilities of geopolymers likely are due to their potentially high mechanical, physical, and durability properties that make geopolymers similar to ceramic materials. The similarity largely is because of a mineralogical and chemical composition silimar to that of ceramic materials. However, to produce effective similar properties, a measured dissolution of source materials in an adequate alkaline solution is required for geopolymerization. This paper examines the effects of sodium hydroxide (NaOH) and sodium silicate (${\mathrm{Na}}_2{\mathrm{SiO}}_3$) solutions on the properties of loess geopolymer and its effective use in ceramic tiles repairing. The experiments involved 8M concentration of sodium hydroxide and a combination of NaOH and sodium silicate with the same molarity at a ratio of ${\mathrm{SiO}}_2:{\mathrm{Na}}_2\mathrm{O}=2.5$. Compressive and split tensile strengths of the loess geopolymer mortars (GPMs) were assessed at 7 and 28 days. X-ray diffraction (XRD), energy dispersive X-ray (EDX), scanning electron micrographs (SEM), and mercury intrusion porosimetry (MIP) analysis were carried out to determine the GPM behavior under alkali solutions as well as the correlation between its strength and structure. The resulting geopolymer loess was used to fill ceramic tile gaps. The experiment showed that the reaction and strength performance of loess geopolymer depended on the precursors and alkali liquids used. It was also established that the mixture of NaOH and ${\mathrm{Na}}_2{\mathrm{SiO}}_3$ not only reduced the pores in the loess based–geopolymer matrix but also had adequate mechanical behavior, effective adhesion, and durability for filling ceramic tile gaps.

Modification of asphalt binders has been one of the common techniques to overcome the climatic and traffic-related distresses that develop in bituminous materials. Over the past decade, many new methods of incorporating recycled tire rubber as a modifier have been developed and evaluated by states and county road departments. This study focuses on the use of the so-called devulcanized recycled tire rubber modifier and its effects on the performance grade, fatigue cracking resistance, and rutting resistance of asphalt binder. Devulcanized rubber was incorporated into hot liquid asphalt at various percentages using high and low shear blending, consecutively. First, the effect of modifications on continuous performance grades (PG) at low, intermediate, and high temperatures was investigated. Second, equistiffness temperatures of the binder-rubber mixes were established, and the fatigue cracking resistances of the rubber-binder blends were measured by using the linear amplitude sweep (LAS) test at different strain levels. Last, the multiple stress creep and recovery test (MSCR) was conducted on the modified asphalt samples to characterize the high-temperature performance. Although there was a significant improvement on high PG as the modifier amount increased, the improvement for intermediate and low PGs was minimal. The same trend observed for high PG of the modified asphalt binders was also obtained for fatigue cracking resistance and rutting resistance. The results showed that the use of devulcanized rubber modification could successfully extend the life of bituminous materials.

Sulfate-rich dispersive soils are worldwide responsible for damaging earthworks, such as roadway roadbeds and embankments. One of the causes for such behavior is the high amount of exchangeable sodium ions adsorbed on their clay particles vastly increasing erosion susceptibility, being responsible for problems as piping, ravines, and water turbidity. In order to reduce the erodibility, it is usual to treat such soils with calcium-based stabilizers. However, in the presence of sulfates, when combined with calcium-based stabilizers in the soil, reactions take place between stabilizers and sulfates to form expansive minerals. Namely, these minerals are known as ettringite and thaumasite and are responsible for excessive volumetric swell. In this context, the present research aims to develop alternative soil stabilizers (industrial byproducts plus artificial pozzolans) and reinforcements (fiberglass) to solve problems associated with sulfate-rich dispersive soils. Thus, a binder composed of carbide lime and ground glass was used. In addition, fiberglass was applied to look for enhanced mechanical properties of the materials. To assess the efficiency of the proposed stabilization and reinforcement, unconfined compressive and splitting tensile strength, ultrasonic pulse velocity, wet and dry durability, and fatigue life tests were carried out. Soil–ground glass–carbide lime-fiberglass blends were molded at different porosities, carbide lime, ground glass, and fiberglass contents. Results show that unconfined compressive and split tensile strength and initial shear modulus are highly dependent on changes in porosity and lime content. Durability, expressed as the accumulated loss of mass, could be assessed through the adjusted porosity/lime index ($\eta /L_{iv}$). Fiberglass inclusion resulted in higher tensile strength. The fatigue life was correlated to the $\eta /L_{iv}$ index through a negative exponent. The greater the carbide lime level, the smaller was the fatigue life for all treated specimens. An increase in porosity results in fewer contacts between particles, whereas an increase in carbide lime content enhanced the specimen’s rigidity.

In the present study, the effect of phosphogypsum, a byproduct from the phosphoric acid production industry, on the clinkerization process was researched in order to improve the burnability of clinkers at lower burning temperatures. Raw meal samples containing phosphogypsum at 0%, 1%, 3%, and 5% by weight were burned at 1,350°C, 1,400°C, 1,450°C, and 1,500°C. The introduction of phosphogypsum reduced the presence of unbounded (free) CaO relatively up to 43%. Thus, the mineralization effect of phosphogypsum promotes lower burning temperatures. The free CaO content of the 5% phosphogypsum containing clinker decreased to 0.94% at 1,400°C after $120\min$ of burning time. The free CaO content was found to be almost identical (0.75%) to that of industrial clinker burned in a rotary kiln at 1,500°C. Due to the low free CaO content ($<1\%$) and the burnability index (73), the recycling of phosphogypsum wastes was found to be suitable for the production of eco-efficient clinkers. The reduced energy consumption and energy-related ${\mathrm{CO}}_2$ emissions in such modified clinkers can contribute to the economic and ecological goals of the cement industry.

This paper presents a series of experimental investigations on the time-dependent characteristics of ethylene–propylene–diene monomer (EPDM) under various temperatures and strain conditions. The time-dependent mechanical properties including relaxation modulus and creep compliance of EPDM are investigated through short-term experiments. Based on the time-temperature superposition principle (TTSP), a transformation method named as the time-temperature-strain/stress superposition principle (TTSSP) is proposed to obtain the long-term time-dependent characteristics. The master curves of TTSP are obtained via horizontal shifting of the curves of the relaxation modulus or creep compliance with time and the shift factors are fitted by the Williams-Landel-Ferry equation. The results show that TTSSP is suitable to predict the stress relaxation and creep behavior of EPDM. The results show that, after serving for 100 years at 15°C, the relaxation modulus could reduce to 44.7% under 10% strain, whereas the creep compliance would increase to 191.3% under 1 MPa stress.

Steel fiber–reinforced sprayed concrete (SFRSC) is widely used for ground support in underground works. The panel test, as in EN 14488-5, is one of the most common procedures for the quality control of the energy absorption capacity of SFRSC. The test entails the use of large equipment to manipulate and characterize heavy specimens that cannot be easily extracted from a structure in case a direct assessment of the material in place is needed. Alternative procedures, such as the Barcelona test (BCN), have been used to assess the energy absorption of cast fiber–reinforced concrete in smaller-scale cylindrical specimens that can be extracted from a structure and are considerably less demanding in terms of equipment and payload. The objective of this study is to evaluate the use of the BCN as a substitution of the traditional square panel test to assess the energy absorption of SFRSC. Both tests were conducted in parallel in combination with the quantification of the incorporated fiber content through an inductive test. Hence, the analysis reflects the actual control conditions of the SFRSC under the influence of spraying. Results indicate a possible reliable correlation between the BCN and panel test if the cracked area is considered. Different sizes of cores were tested to understand the influence of this parameter in energy absorption by the BCN test. The reduction of specimen size demands an increase in the number of determinations per batch to ensure representative results. The study suggests that the BCN can be considered a viable method of evaluating the energy absorption of SFRSC in cores extracted from test panels or actual tunnel linings.

In the AASHTO T-378 protocol for computing dynamic modulus and phase angle, the bituminous mixture sample is subjected to a continuous loading from high frequency to low frequency. The postprocessing method involves fitting a regression equation to the stress and the strain data. The influence of confinement pressure and rest period between the frequencies on the overall mechanical response of the material within the context of the current test method needs detailed investigation, and this paper discusses some of the interesting aspects. Two dense graded bituminous mixtures (unmodified and polymer-modified) are subjected to repeated haversine compression loading at six different temperatures (5°C–55°C) and ten test frequencies ($25–0.01\mathrm{Hz}$). The tests are conducted with and without confinement pressure and rest period. The analysis of the data revealed that confinement pressure strongly influenced the dynamic modulus and phase angle in the temperature range of 35°C–55°C and frequencies in the range of $0.01–2\mathrm{Hz}$. The influence of the rest period on dynamic modulus and phase angle is observed to be negligible. For all the loading conditions, the dynamic modulus master curve is constructed using the sigmoidal model, and the phase angle master curve is constructed following a free shifting procedure. The results show that for the dynamic modulus master curve, the root mean square error is considerable for the tests conducted with confinement conditions. Finally, the collected data that fulfilled the Kramers–Kronig relationship is used for generating a master curve for dynamic modulus and phase angle in the temperature range of 5°C–35°C.

This paper examines the feasibility of roll-threading superelastic Cu-Al-Mn shape memory allow (SMA) rods. The key idea behind this study was to perform roll-threading between quenching and aging, where cold workability of the material is relatively high. To obtain excellent superelasticity, single-crystal superelastic Cu-Al-Mn SMA rods were prepared with 16-mm diameter and 300-mm length. Threadability was studied by dimensional inspection and surface observations. Mechanical properties of the threaded rods were examined by cyclic tension tests. Comparisons between rolled and cut threads were made by cutting each single-crystal rod into halves to obtain two rod specimens having the same crystal orientation, thus ensuring fair comparison by excluding the influence of variations in orientations of the single-crystal rod. From the study, it was demonstrated that roll-threading of Cu-Al-Mn SMA rods was possible if roll-threading is performed between quenching and aging. Since additional heat treatment from the ordinary manufacturing process is unnecessary, roll-threading of Cu-Al-Mn SMA rods is as easy as that of steel rods. It was also demonstrated that the roll threads had significantly superior fatigue resistance compared with the cut threads of the same size. These results suggest that superelastic Cu-Al-Mn SMA rods with rolled threads are suitable for mass production to be used in structural and earthquake engineering applications.