Journal of Materials in Civil Engineering

Cement-stabilized rammed earth (CSRE) is a monolithic construction used in the construction of load-bearing walls. CSRE predominantly undergoes catastrophic shear failures under compression. Short randomly oriented fiber reinforcements have the potential to enhance the CSRE ductility and its postpeak response. The literature available on fiber-reinforced rammed earth was mainly focused on overall mechanical properties of the material, but very little is known about the fiber–matrix interfacial properties. The fiber–matrix interfacial bond characteristics play a significant role in the mechanical behavior of fiber-reinforced composite. Understanding the postpeak behavior of fiber-reinforced composites such as coir fiber–reinforced CSRE necessitates the information on interfacial bond strength of the fiber and the matrix. In the present study, the bond strength between the coir fiber and the CSRE matrix was explored using pullout tests. The study shows that pullout resistance of the fiber in the CSRE matrix depends on the fiber embedment length, dry density, cement content, and moisture content. The current investigations focused on these parameters. The critical fiber embedment length for the natural coir fiber in the CSRE matrix was found to 25 mm. The use of chopped fibers less than the critical embedment length can help in the design of ductile earthen construction materials with improved postpeak response.

In the present study, three-point bending tests are carried out using single-edge notched beam specimens of bitumen and mastic to quantify healing. Experiments are conducted at a controlled displacement rate of 1 mm per minute at $-15°\mathrm{C}$. After the crack propagation, samples are given a rest period of 2 h at 10°C to promote healing before retesting them. Two different analysis approaches appealing to linear elastic fracture mechanics and viscoelastic fracture mechanics are compared. In order to perform analysis based on viscoelastic fracture mechanics, the elastic-viscoelastic correspondence principle is used. The amount of healing after the rest period is quantified using various healing indices based on the recovery of stiffness, peak load, fracture toughness, fracture energy, and J-integral. From the analysis performed on bitumen and mastic samples, the study illustrates that the quantum of healing is different when comparing different healing indices. While the stiffness-based healing index demonstrated the healing ability of bitumen, other healing indices used in the study confirmed the higher healing potential of mastic. The healing based on critical value of J-integral shows a distinct difference in the healing of bitumen and mastic. The study emphasizes that the quantification of healing capacity when using different healing indices should be closely linked to its measured conditions.

In recent years, compared with the traditional portland cement, environmentally friendly geopolymers have gained more attention as construction materials. This paper considered volcanic ash (VA) and ground granulated blast furnace slag (GGBFS) in different percentages (0%, 3%, 7%, and 10%) as a replacement for the conventionally used portland cement to stabilize sandy soils. NaOH and ${\mathrm{Na}}_2{\mathrm{SiO}}_3$ in different concentrations (4, 8, and $12\mathrm{M}$) and alkali to binder ratios (1, 1.5, 2, and 3) were used as alkali activator solutions to build new geopolymers. Samples were cured at both ambient and oven temperatures and for 1, 7, and 28 days. Unconfined compressive strength (UCS) of samples then was evaluated. Two predictive approaches, artificial neural network (ANN) modeling and the evolutionary polynomial regression technique (EPR), were applied to model UCS of geopolymerized sand samples. Regarding the high value of the coefficient of determination of the proposed ANN, 97%, and acceptable prediction errors, RMS error of 0.0439 and MAE of 0.0336, an 8-5-10-1 ANN was introduced as a more accurate tool for the prediction of UCS. Next, three-dimensional parametrical studies investigated the effects of simultaneous changes in alkali solution, binder, and curing condition parameters on UCS values of geopolymerized samples. Sensitivity analysis based on the cosine amplitude method introduced the Si/Al ratio as the parameter most affecting and VA content as the parameter least affecting the compressive strength of samples. Results were analyzed further using pH and electrical conductivity tests and interpreted based on microstructural investigations using scanning electron microscopy (SEM) images and X-ray diffraction analysis.

In this paper, the hydration reaction and properties of magnesium oxysulfate (MOS) cement modified with ammonium citrate tribasic are discussed and compared with MOS cement without chemical additives. The hydration reaction characteristics, hydration products, mechanical properties, and microstructures of MOS cement prepared with and without chemical additives were characterized by isothermal calorimetry, quantitative X-ray diffraction (QXRD), mercury intrusion porosimetry (MIP), thermogravimetry (TG), and scanning electron microscopy (SEM), and the mechanism of action of the chemical additives–was investigated. The results show that when the molar ratio of $\alpha \text{-}{\mathrm{MgO}:\mathrm{MgSO}}_4{·7\mathrm{H}}_2{\mathrm{O}:\mathrm{H}}_2\mathrm{O}$ is $8:1:11$, the basic salt hydrate $5\mathrm{Mg}(\mathrm{OH}{)}_2·{\mathrm{MgSO}}_4·7{\mathrm{H}}_2\mathrm{O}$ phase (5·1·7 phase) can be formed in MOS cement with and without chemical additives. However, ammonium citrate tribasic is an effective chemical additive that can (1) adjust the concentration of ${\mathrm{H}}^{+}$ and OH⁻ ions in the liquid phase through buffering to meet the requirements of the ${\mathrm{H}}^{+}$ or ${\mathrm{OH}}^{-}$ ion concentration (or pH value) required for the neutralization reaction of MgO particles, (2) strengthen the neutralization reaction of MgO particles, and (3) reduce the hydration reaction of MgO particles to form ${\mathrm{Mg}(\mathrm{OH})}_2$ through the complexation of the complex ions. Therefore, a large amount of the 5·1·7 phase and small amounts of ${\mathrm{Mg}(\mathrm{OH})}_2$ and the amorphous phase are formed in MOS cement with ammonium citrate tribasic, which optimizes the micropore structure and improves its mechanical strength and water resistance.

Cold recycling of asphalt pavement is an effective rehabilitation technique in terms of saving natural resources and cost of construction. The current study focuses on cold-recycled asphalt mixture designated as emulsified cold-recycled mixture (ECRM) that contains 100% reclaimed asphalt pavement material and slow-setting asphalt emulsion. Here, a repeated haversine compression test is conducted with and without confinement pressure at six temperatures (0°C, 10°C, 20°C, 30°C, 40°C, and 50°C) and 10 frequencies (25, 20, 10, 5, 2, 1, 0.5, 0.2, 0.1, and 0.01 Hz). The stress–strain–time response of ECRM is investigated, and it is observed that the influence of confinement pressure is negligible in the temperature range of 0°C–10°C, whereas it is significant at temperature 30°C and higher, irrespective of the frequency of loading. However, at 20°C, the influence of confinement pressure is negligible at higher frequencies (25–10 Hz), and it is significant at lower frequencies (less than 10 Hz). The viscoelastic response of ECRM is seen at all temperature, frequency, and confinement conditions of loading from the analyzed Lissajous plots. The dynamic modulus and phase angle are computed using the regression and the fast Fourier-transform (FFT) methods. The dynamic modulus and phase angle master curve is then generated using a free-shifting approach and a model-based approach. The model-based approach involves the numerical solution of the exact Kramers–Kronig relations combined with the generalized logistic sigmoidal model. The FFT-based dynamic modulus is used to construct a master curve with the generalized logistic sigmoidal model. Such a model-based master curve resulted in excellent predictive capabilities for dynamic modulus, and hence it is suggested for ECRM.

There are large volumes of lead-zinc tailings (LZT) produced in China and elsewhere in the world. LZT disposal to the landfill is problematic and causes many environmental issues. The objective of this work is to demonstrate how LZT can be effectively used to produce ceramisite. The experimental results show that the LZT alone is not suitable for making ceramisite. When mixed with clay, it can be turned into ceramisite with ideal properties for building applications. The optimization test results reported herein show that priority order of factors affecting the compressive strength of cylinder samples is, in turn, sintering temperature $(B)>$ sintering time ($C$) $>\mathrm{LZT}$ content ($A$). The order of factors influencing the density is $C>A>B$. The results show that the leaching content of Pb and Zn of all sintered ceramisite samples is far less than the limit values of hazardous components in the leachate specified in the relevant standard. The optimum combination of parameters to produce ceramisite is 50% LZT content, at sintering temperature of 1,150°C and sintering time of 9 min. Under the optimum conditions, the compressive strength and apparent density of ceramisite have reached 9.9 MPa and $1.12\mathrm{g}/{\mathrm{cm}}^3$ respectively. The results indicate that ceramisite can effectively be made using LTZ for civil engineering applications.

There is significant microstructural variability in alkali-activated coal fly ashes (CFA) depending on the activation conditions and the intrinsic properties of the utilized CFAs. This study systematically presents the impact of intrinsic CFA properties on these variations while keeping the activation conditions constant. Four high-Ca and four low-Ca CFAs were activated with 10 M NaOH under hydrothermal conditions (80°C, 1 day). The mineralogical and morphological changes investigated through X-ray diffraction (XRD), Fourier transform infrared (FTIR), and scanning electron microscopy (SEM) point out some poorly zeolitic formations with N─ A─ S─ (H) phase for low-Ca samples and with (N, C)─ A─ S─ H phase for high-Ca samples. Due to their self-cementitious properties, the mechanical performance—determined by compressive strength tests—of the high-Ca CFAs was higher than that of the low-Ca ones; albeit, too much free CaO had a detrimental effect. In all samples, the performance was enhanced with increased fineness. The mechanical performance of alkali-activated CFAs is mainly attributed to the amorphous or poorly crystalline phases. XRD and FTIR were able to confirm the amorphous gel formation. However, a direct correlation of their results with strength development could not be established. On the other hand, the SEM micrographs of the higher-strength samples showed a denser structure. Obtained results map out microstructural variations of alkali-activated CFAs, guiding the way for their effective reutilization.

The stainless-clad bimetallic steel plate (SCBSP) formed by cladding a layer of stainless steel on the surface of a mild steel plate is a solution to improve the corrosion resistance of steel in corrosive environments To study the hysteretic behavior of stainless-clad bimetallic steel plates under cyclic load, tests of 14 specimens taken from Q235+S34553 SCBSP with normal thickness of $3+8\mathrm{mm}$ were carried out, in which 14 different loading protocols were incorporated. Based on the test results, the hysteretic behavior of the SCBSP specimens was analyzed. The envelope curves of the SCBSP under cyclic loading were fitted based on the Ramberg-Osgood model (R-O model), and the energy-dissipation capacity of the SCBSP was evaluated by calculating their energy-dissipation index (EDI). Finally, the Chaboche combined hardening model was employed, its relevant parameters were identified, and the identification results were verified by finite-element simulation. The results show that SCBSP has good energy-dissipation capacity. The R-O model and Chaboche model can well express the mechanical behavior of SCBSPs under cyclic loading.

The passivation and chloride-induced corrosion behavior of aluminum alloys (AAs) 2014, 5083, and 6061, as a key component in aluminum alloy–concrete composite, were investigated in a pore solution of portland cement paste via electrochemical methods, scanning electron microscopy (SEM), and Raman spectroscopy. Results show that AA6061 presents the highest corrosion resistance due to the formation of uniform $\alpha \text{-}\mathrm{Al}(\mathrm{OH}{)}_3$ layer on both aluminum matrix and intermetallic phases. AA6061 shows the highest chloride threshold value while exhibiting the lowest corrosion resistance when chloride concentration is above the threshold. Different mechanisms of protection and chloride-induced corrosion for the three aluminum alloys in pore solution are proposed.

Terminal blend rubberized asphalt (TBRA) is widely used as binder of asphalt mixtures due to its technical characteristics of storage stability. However, its road performance deteriorates due to the aging process of TBRA. The purpose of this study is to evaluate the aging characteristics of TBRA binders containing 0%, 5%, 10%, 15%, and 20% content of crumb rubber (CR) by weight of the neat binder. All the binders were treated with rolling thin-film oven test (RTFOT) and pressure aging vessel (PAV), respectively. The chemical compositional changes were monitored by attenuated total reflection (ATR)-Fourier transform infrared spectroscopy (FTIR), and physical and rheological properties were tested on neat asphalt and TBRA binders. FTIR test results show that TBRA binders offer greater long-term aging resistance than the neat asphalt binder, and E10TB (10% by weight CR) exhibits the highest long-term aging resistance. With the increase of CR, the temperature sensitivity property of the TBRA binders increases, whereas their high-temperature stability decreases. After PAV aging, blending CRs into neat asphalt causes a higher phase angle aging index and $J_{nr}$ aging index, and lower critical temperature aging index, complex modulus aging index, softening point increment, and rutting factor aging index, indicating their superior long-term aging resistance. Moreover, based on the correlation analysis, the critical temperature aging index (CTAI) has a good linear relationship with the physical aging index (SPI) and chemical aging index ($\mathrm{\Delta }{I}_{\mathrm{CA}}$).

This paper proposes a unified sorption–desorption isotherm for the full range relative humidity (0%–100%) based on categorizing the behavior of different pore size groups for engineered wood products. The sorption and desorption isotherms are established by accumulating the wetting and drying behavior of different pore groups, which qualitatively represent the physical structure of wood material. The porosity of wood is categorized into three distinctive pore size classes, shown to be adequate for capturing the moisture capacity of different wood species with reasonable accuracy, and the saturation behavior is studied separately for each pore type. Based on physical concepts, desorption isotherms are probabilistically derived from sorption behavior. The proposed sorption-desorption isotherm is calibrated with experimental data conducted on seven engineered wood products, including Pacific Teak, Tasmanian Oak, Blackbutt, Radiata Pine, Slash Pine, laminated veneer lumber (LVL) of Radiata pine, and cross-laminated timber (CLT) of Spruce. The relative humidity range for the active participation of each pore type in the moisture content is discussed, and further conditions for the simplification of the proposed isotherm are demonstrated.

To study the antifatigue performance of Q690 high-strength steel in the ocean splash zone, indoor accelerated corrosion tests and high-cycle fatigue tests were carried out, and the $S\text{-}N$ curves of different corrosion specimens were fitted. The law of fatigue crack growth was determined using a scanning electron microscope. The results showed that as the degree of corrosion damage increased, the surface of steel lost its metallic luster, and reddish-brown layered corrosives gradually formed. After 100 days of corrosion, the rust rate and corrosion depth rate of specimens were 7.21% and $1.342\mathrm{mm}/\mathrm{year}$, respectively. Under cyclic loading, the fatigue limit value of corrosion specimens was reduced by 38.89% due to the influence of external corrosion damage, which accelerates the fatigue performance degradation rates of specimens. The damage index can reflect the crack distribution law of failure fracture. When the stress level increases, the number of fatigue bands decreases, and the damage accumulation increases. The research results are of great significance for the fatigue failure prediction and reliability analysis of Q690 high-strength steel.

Accelerated weathering tests are commonly carried out to evaluate the resistance of porous materials to the damage induced by salt crystallization. A wide range of testing procedures have been prescribed by various standards and recommendations to suit the spectrum of materials adopted in general construction. On account of the differences in the procedure and the reagents prescribed, the results of different tests are prone to be different even on the same material. In the current study, a remarkable difference in the severity and pattern of deterioration was observed when the same set of bricks were subjected to accelerated weathering tests prescribed by different standards’ recommendations. Although the deterioration was less severe and always occurred during the drying phases of the first standard, much more severe damage (with about fivefold greater mass changes) was observed during the rewetting phases of the second standard. Simple calculation showed that the concentration of ions furnished in the second standard’s test were about 62% greater than in the first standard’s test. Based on this and the occurrence of more severe damage in spite of drying at lower temperatures in the second standard’s test, different damage mechanisms are envisaged in the two tests. Although the damage in the first standard’s test may be predominantly attributed to evaporation-induced supersaturation, the occurrence of massive damage during successive immersions at room temperature suggests that it could be predominantly caused by dissolution-mediated phase transformation of thenardite to mirabilite in the second standard’s test. These hypotheses about the damage mechanisms presented in the study are mainly based on the qualitative differences between the damage manifestations upon exposure to sodium sulfate solution as per the studied standards’ tests.

Much attention has recently been paid to investigating the internal mechanisms between the void structures of foamed concrete and its mechanical behavior. This study adopted the X-ray computed tomography (X-CT) technique to build three-dimensional (3D) internal void structures of foamed concrete before conducting the unconfined compression test. A sensitivity analysis was conducted to evaluate the influence of the void structure on the mechanical properties. The results showed that the contacts between voids had a primary influence on the residual strength, and the void size was the major influence factor on the modulus. A micromechanical model was developed to simulate the mechanical behavior of the foamed concrete under compression, and good agreements were found with the test results. A simple equation was proposed to predict the mechanical properties of the foamed concretes considering the effects and variations of the void structures on the mechanical properties. Combining the equation with the micromechanical damage model, the variations of the mechanical behavior due to the difference in void structures can be well predicted.

Two feldspars were used as fine aggregates and cement replacement to explore the effect of feldspar dissolution on alkali–silica reaction (ASR) expansion at elevated temperatures (38°C and 60°C). At elevated temperatures, feldspar dissolution increased alkali concentration in pore solution significantly but did not increase ASR expansion of fused silica aggregate. On the contrary, feldspar dissolution even reduced ASR expansion, and the reduction in ASR expansion is more significant at 60°C than at 38°C. The mitigating effect can be attributed to the increase of Al concentration in pore solution resulting from feldspar dissolution because aqueous Al limits the dissolution of reactive silica contained in aggregate. The impact of feldspar dissolution on pore solution may lead to incorrect identification of field-deleterious feldspar-bearing aggregates as nonreactive ones.

Based on the field tests of fly ash concrete with a maximum exposure time of 840 days, the effects of fly ash content and exposure time on gas permeability of concrete were studied. A time-dependent gas permeability coefficient model considering the influence of fly ash content was established. The pore structure parameters of fly ash concrete with different exposure times were measured by the nuclear magnetic resonance (NMR) method. In addition, the time-dependent relationship between microstructural parameters and gas permeability coefficient was discussed. Results show that adding 20%–40% fly ash into concrete can effectively reduce the gas permeability and improve its microstructural features after exposure of 360 days; concrete with 30% fly ash has the minimum critical pore size and average pore size, which have the most significant effect on reducing the gas permeability. With prolonged exposure times, fly ash concrete can increase (decrease effectively) the proportion of pore diameter of 10–50 nm (100–500 nm). Total porosity and critical pore diameter can better characterize the time-dependent gas permeability.

Compacted Gaomiaozi (GMZ) bentonite has been considered as the first choice of buffer materials in the deep geological disposal of high-level radioactive wastes (HLW) in China. During the long-term lifespan of the repository, the bentonite barriers will simultaneously undergo a coupled thermohydromechanical (T-H-M) process, which induces complex volume changes. In this study, the constitutive model of GMZ bentonite with consideration of THM coupling was established, using the framework of the BExM model along with a thermal volume change model for unsaturated soils. New formulations for the interaction between micro and macrostructures ($f_I$ and $f_D$) and the thermal loading yield surface (TY curve) were adopted. Emphasis was placed on the identification and validation of the material parameters based on a series of experimental results. A comparison between the simulated and measured values show that the improved model with parameters calibrated successfully represents the main features of volume changes observed in the laboratory and during wetting-drying cycles, elastic thermal expansion, and plastic thermal contraction under various suctions and stresses, as well as compressibility under various suctions and temperatures.

Asphalt aging is a major cause of distresses in asphalt pavement, seriously decreasing the in-service performance and shortening the lifetime of pavement. Traditional asphalt rejuvenating methods usually consume a great deal of worker and energy resources. This study encapsulated rejuvenator to automatically realize in-situ rejuvenation of aged asphalt in pavement. Soybean oil was selected as the asphalt rejuvenator, and its effectiveness in rejuvenating the aged asphalt was identified. Then it was encapsulated into three kinds of calcium alginate capsules by the orifice coagulation bath method. Next, the micromorphology, internal structure, density, mechanical strength, and thermal stability of the capsules were characterized using digital microscopy, stereomicroscope, graduated cylinder test, uniaxial compressive test, and thermogravimetric analysis, respectively. The effects of the capsules on the pavement performance of asphalt mixture were analyzed. Test results showed that the soybean oil effectively recovered the properties of the short-term aged asphalt binder at an optimum content of 2% by binder mass, and it was encapsulated successfully in capsules with diameters of about 2 mm. There were many slight bumps and indentations on the capsule surface, and many pores filled with soybean oil inside the capsule. The density of the capsules was close to that of the asphalt binder, providing a favorable condition for their uniform distribution in the asphalt mixture. It was proved that the capsules can resist the mechanical and thermal conditions during road construction. The pavement performance of asphalt mixture containing capsules still met the requirement of the specification in China. The findings of this paper are helpful to prolong the service life of asphalt pavement and reduce the maintenance costs in the long run, ultimately contributing to the development of smart and sustainable pavement.

In this study, asphalt mixtures were subjected to the boiling water test, and the stripping potential was quantified in terms of loss index using the photodetection technique. Initially, the change in loss index due to variability in testing protocols like boiling time, drying time, and drying method was evaluated. Subsequently, loss index (LI), and tensile strength ratio (TSR) were determined for three different aggregate types, five liquid anti-stripping additive contents, and four dosages of hydrated lime. Results indicated that LI increased with the increase in boiling time, whereas LI decreased due to moisture. In terms of the drying method, the recommended hot-air-gun drying method was suitable for quantifying stripping. Furthermore, the results of both LI and TSR had a good correlation. The threshold limits for LI with respect to specified TSR requirement was evaluated and was found to be sensitive to variation in aggregate type and additive content. Therefore, LI values estimated using a quick tool could facilitate quality control during the asphalt mixture’s production stage.

Urban waste glass powder (GP) has been identified as the Si-rich ($>70\%$) but Ca- and Al-deficient precursor material for use in alkali-activated materials (AAMs). To facilitate the recycling and utilization of GP, this study explored the possibility of using calcium sulfoaluminate cement (CSA) as both reactive alumina source and shrinkage-reducing agent to improve the strength and durability properties of alkali-activated waste GP. The experimental and thermodynamic simulation showed that 0%–50% of CSA substitution could contribute to the formation of calcium (sodium) aluminosilicate hydrate [C─ (N─ )A─ S─ H] and N─ A─ S─ H gels due to the release of Ca and Al from CSA. Nonetheless, more than 50% of CSA resulted in the change of reaction paths and the precipitation of AFt and AFm as the major phases, which reduced the porosity significantly. A higher CSA replacement ratio generally increased the early strength development rate, while the delayed strength gain could be observed due to the slower but progressive dissolution of GP. More importantly, CSA effectively reduced the overall shrinkage of hardened AAM pastes, and the mixtures with up to 50% of CSA had lower shrinkage than the reference ordinary portland cement sample. However, the GP-rich mixtures showed viscoelastic/viscoplastic response to the capillary pressure–induced stress upon drying, possibly due to the structural rearrangement of C─ (N─ )A─ S─ H and N─ A─ S─ H. It was also found that the moderate amount of CSA in mixtures could considerably reduce the leaching of free alkali and therefore lower the potential environmental impacts. This study can improve the limited understanding on the hydrate assemblages and properties of AAMs based on GP and CSA, and expand the toolkit of cementitious materials based on recycled urban waste glass.

Trillions of cigarette butts (CBs) are dumped into landfills globally. CBs leach toxic components into the soil, including heavy metals, tar, and many other chemical compounds. Approximately 7.2 billion CBs are discarded every year in Australia, and 16.8 billion CBs accumulate in the waste management system annually. In previous work, the encapsulation method for CB with bitumen and paraffin wax was developed and encapsulated CB in dense graded asphalt (DGA) was evaluated using bitumen classes C320, C170, and C600. In recent studies, the encapsulation method was improved, and the possible use of bitumen-encapsulated CB (BECB) in stone mastic asphalt (SMA) was demonstrated. To build on this foundational research, the current work aimed to investigate the use of improved BECB in heavy-duty DGA prepared with polymer-modified bitumen (PMB) class A10E. Samples were prepared following VicRoads and Austroads guidelines. In this research, the Marshall stability and flow, resilient modulus, dynamic creep, tensile strength ratio, and indirect tension fatigue test were performed to evaluate the performance of BECB-modified DGA. The results were compared with the control DGA prepared with industry-standard conventional materials. Test results suggested that using 0.5% and 1% BECB in DGA met the industry requirements and endorsed the recycling method of CB in asphalt concrete.

Jarosite (JS) is an industrial solid waste obtained from zinc industries that plays an important role as a pollutant engendering soil and ground water contamination. The present research article has highlighted the use of JS as a filler material in pavement construction, thereby limiting its pernicious threat to the environment and promoting sustainable construction practices. This study compared the performance of asphalt mastics and mixes made with JS with their counterparts made with conventional materials (stone dust) and a widely used waste (fly ash) filler. A physical and chemical characterization of fillers was completed, and then the asphalt concrete mixes were designed at varied filler proportions (2%, 4%, 6%, and 8%). Subsequently, the asphalt mastics corresponding to various mixes were designed, and their rheological and morphological properties were assessed. Finally, the performance of asphalt mixes against various types of distress was analyzed along with their environmental suitability. The results highlighted that asphalt mixes containing JS exhibited paramount resistance against cracking, moisture sensitivity, and rutting. This result was mostly attributed to the high porosity, finer nature, high specific surface area, and high asphalt–filler interaction of JS. In addition to the superior engineering properties, the asphalt mixes containing JS were also found to exhibit satisfactory environmental suitability.

Gas breakthrough behavior is an important parameter for evaluating the performance of cement-based materials in gas storage projects or radioactive waste disposal facilities. This study conducted gas breakthrough experiments using the step-by-step method on mortar samples to investigate the gas breakthrough properties of mortar. Mortar samples with three different mixing proportions of silica fume contents (0%, 5%, and 10% by weight) were selected for the experiments. The results showed that the incorporation of silica fume in the mortar samples significantly reduced both the intrinsic gas permeability and the water permeability, and increased the gas breakthrough pressure. The gas breakthrough pressures of the mortar samples with silica fume contents of 0%, 5%, and 10% were approximately 1.5, 3.7, and 5.4 MPa, respectively. Theoretical derivation and experiment data fitting indicated that on a double logarithmic scale the gas breakthrough pressure was linearly correlated with the intrinsic gas permeability and the water permeability, respectively.

Asphalt aging is the main cause of fatigue failure of asphalt pavement. The performance of rodlike nano-ZnO is better than that of nano-ZnO in all aspects, and rodlike nanomaterials can reduce the agglomeration phenomenon of powder like nanomaterials in asphalt. Therefore, in this paper, rodlike nano-ZnO particles were added to asphalt to improve its aging resistance. Asphalt was modified by adding different amounts of rodlike nano-ZnO particles. The penetration (25°C), softening point, and ductility (5°C) of rodlike nano-ZnO–modified asphalt were tested. The aging of rodlike nano-ZnO–modified asphalt was simulated by thin film oven test (TFOT) and ultraviolet (UV) aging. The dynamic shear rheological (DSR) properties of modified asphalt before and after aging were studied, and the mechanism was explained using UV-visible-infrared absorption test, Fourier transform infrared (FITR) spectroscopy, and scanning electron microscopy. Rodlike nano-ZnO particles can increase the softening point of asphalt and reduce the penetration (25°C), which has a positive effect on the ductility (5°C), but when the content is 3%, the ductility of asphalt will be affected. The complex shear modulus (${\mathrm{G}}^{*}$) and phase angle ($\delta$) of the composites can be improved using rodlike nano-ZnO. With the increase of the amount of rodlike nano-ZnO, the performance change rate of modified asphalt before and after aging decreases gradually. When the content of rodlike nano-ZnO is 3%, the modified asphalt has the best UV absorption capacity, does not affect other physical properties, and can significantly improve the drying and hardening of the microsurface after aging. Therefore, rodlike nano-ZnO can significantly improve the UV resistance of asphalt.

The macroscopic property of cement-based materials depends on their pore structure. Due to the complex and disordered pore structure of cement-based materials, traditional parameters like porosity and mean distribution radius are not accurate enough for strength predictions. Fractal geometry was employed to characterize the complexity of pore structure more accurately than existing parameters, especially the scale-dependent fractal properties, which are more dependent on the pore ranges. In this study, the pore size range of cement-based materials containing dolomite powder was regularly segmented to characterize the scale-dependent fractal nature of the pore structure. The relationship between the segmented fractal dimension and the compressive strength was discussed. Results based on the mercury intrusion porosimetry (MIP) and mechanical property tests showed that the difference existed in the relationship between segmented fractal dimension and dolomite powder content under various pore ranges. The relationships between compressive strength and fractal dimension of gel pores and fractal dimension of large pores presented positive and negative linear function, respectively. The strength equations expressed in terms of the segmented fractal dimension were proposed. Regression analysis proved that the equations in this study had high prediction accuracy.

Freeze–thaw (FT) damage is one of the main factors affecting the durability of concrete structures. This paper focused on the effects of the coarse aggregate volume fraction (CAVF) on FT damage to concrete in different salt solution concentrations (SSCs). The dynamic elastic modulus (DEM) and cumulative scaling quantity (CSQ) were obtained by rapid FT tests to investigate the CAVF’s influence at different SSCs. Both the dynamic elastic modulus and cumulative scaling quantity became worse with the increasing FT cycles. The dynamic elastic modulus increased with an increasing coarse aggregate volume fraction, but the cumulative scaling quantity decreased significantly. Meanwhile, the salt solution concentration had little effects on the DEM and CSQ. Furthermore, an empirical prediction model for evaluating the relative dynamic elastic modulus (RDEM) considering the CAVF was established via regression analysis and validated by experiments. A prediction model for assessing the relative cumulative scaling quantity taking into account the effects of the loss rates of the RDEM and CAVF was developed, and it correlated well with the experimental results.

The current investigation presents a laboratory assessment of the physical and rheological properties of control and nanosilica-modified asphalt binders incorporated with warm mix additives (WMAs). Nanosilica can be produced from rice husk and silica fumes and therefore is a cost-effective and environment-friendly asphalt modifier. Fisher-Tropsch wax (FT wax) and organosilane additive were the two WMAs utilized in the current study. The study utilized three concentrations for each additive. Rutting evaluation of the asphalt binders was done through Superpave rutting and the multiple stress creep and recovery (MSCR) test. The fatigue performance was evaluated utilizing the Superpave fatigue test and the linear amplitude sweep (LAS) test. The results of this study revealed that adding WMAs decreased the viscosity of the control and nanosilica-modified asphalt binders. The asphalt binder showed an improved elevated temperature performance after the incorporation of WMA additives. The incorporation of WMA additives enhanced the resistance against fatigue cracking as revealed by the LAS test. The resistance to aging was enhanced after the addition of warm mix additives.

Environmental, economic, and social benefits are encouraging the incorporation of reclaimed asphalt pavement (RAP) in stone matrix asphalt (SMA) mixtures. However, RAP-incorporating mixtures have higher stiffness, which leads to fracture failure. This research used semicircular bending (SCB) tests to evaluate the fracture characteristics, i.e., maximum tensile strength (TS), fracture energy (FE), and flexibility index (FI), of RAP-incorporating SMA mixtures with different rejuvenators. Four RAP contents (10%, 20%, 30%, and 40% by weight of the aggregate) and four different rejuvenators [waste vegetable oil (WVO), waste engine oil (WEO), waste grease (WG), and palm oil sludge (POS)] with four rejuvenator dosages (0%, 3%, 6%, and 9% by weight of binder) were used to prepare SMA mixtures. Fracture characteristics were analyzed using 100-mm-diameter Marshall specimens. Rejuvenated mixtures had about a 10% increase in the TS compared with nonrejuvenated mixtures. The WVO and WEO substantially increased the TS, FE, and FI values other two rejuvenators, whereas WG and POS provided no improvement. The incorporation of rejuvenator improved the fracture resistance and allowed up to 40% RAP content. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analyses were performed to examine the rejuvenators’ effectiveness at the microlevel. SEM images measured the level of activation of aged binder and the lubrication effect of different rejuvenators. In terms of fracture characterization, 30% RAP content along with 6% WVO was the best performing SMA mixture.

Deicing chemicals have been widely used in cold regions to control snow and ice on the surfaces of concrete products. At present, the most widely used deicers are chlorides or acetates. Although the effects of the chloride- or acetate-based deicers on the durability of concrete products have been investigated, the impacts of the calcium-based deicers on the performance of concrete materials were barely discussed. In this study, the effects of calcium-based deicers on the durability of concrete materials with exposure to freeze/thaw (F/T) and wet/dry (W/D) cycles have been investigated in the laboratory. Three types of deicers, including calcium chloride (${\mathrm{CaCl}}_2$), calcium acetate (${\mathrm{CaAc}}_2$), and calcium formate (${\mathrm{CaFm}}_2$), were used to compare their effects on the durability of concrete materials. The testing results show that the mechanical properties of concrete materials significantly declined after exposure to deicers along with F/T and W/D cycles. The microstructure analysis demonstrates that the reduction of the mechanical properties primarily resulted from the microstructure change after exposure to the F/T and W/D cycles in deicing chemical solutions. This study not only provides experimental results of the mechanical properties reduction regularity but also elucidates a potential degradation mechanism of the reinforced concrete products and structures from a perspective of the microstructure change.

Geopolymers, known as the next generation binder, are gaining the interest of contemporary researchers due to their superior strength and durability properties compared with ordinary portland cement (OPC). The current investigation aims to develop a greener geopolymer concrete (GC) containing waste materials as a replacement to fine and coarse aggregates. Waste foundry sand (WFS), an industrial waste, has been used as partial replacement to normal sand, whereas natural coarse aggregates were partially to fully replaced by recycled concrete aggregates (RCA). In addition, indigenously synthesized graphene oxide (GO), in the laboratory, was added to GC by a small proportion of 0.05% by weight of binder to compensate for the performance loss in GC due to addition of waste materials. The strength and durability properties were studied up to 90 days of curing age. The microstructure was also studied by conducting scanning electron microscope (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR) to support the strength and durability results. The test results are promising and indicate enhanced performance of GC produced using waste materials with GO addition.

A series of direct shear tests were conducted on fine, medium, and coarse sand–fiber mixtures subjected to normal pressures of 100, 200, and 300 kPa. Soils were mixed with 0.1%, 0.2%, and 0.3% fibers 6, 12, and 18 mm in length to assess their effects on shear strength characteristics of samples with 70% relative density. Genetic expression programming (GEP) was also evolved to envisage strengths and strains of sand–fiber mixtures. Test results showed that in general, fiber inclusion improves composite characteristics with fine sand–fiber mixtures showing the greatest enhancements in shear strengths. Inclusion of 6 and 12 mm fibers in coarse sand failed to improve strength characteristics due to the inadequate anchorage length and ineffective interactions with grains. Amid the factors investigated, fiber length and concentration, normal stress, and gradation proved to be the most influential. GEP results revealed high accuracy with coefficients of determination of 0.945 and 0.951 for training and testing phases, respectively, and sensitivity analysis illustrated that interaction is most sensitive to fiber length and the coefficient of curvature.

This study examined the changes in the microstructure and phase composition of Hadfield steel depending on the content of the main elements Mn and C and the alloying elements Cr and V. Phase composition and fine structure of manganese steels were studied using X-ray diffraction analysis and electron diffraction using transmission electron microscopy. Samples of steel were undoped and were alloyed with Cr and V at a content of $\sim 0.4\%$ and $\sim 1\%$ by weight C and 6%–18% by weight Mn. The main phase of the steels, regardless of the Mn content, remained completely austenitic, and the introduction of Cr and V led to the expansion of the $\gamma$ region. The average scalar density depended on the concentration of Mn, whereas Cr and V shifted the region of the $\epsilon$ phase toward a lower concentration of Mn and increased the content of the $\alpha$ phase.

This work studies the hydration kinetics of portland cement pastes blended with multiwalled carbon nanotubes (MWCNTs) aqueous dispersions. Anionic, cationic, and nonionic surfactants—i.e., surfactants that have different charged functional groups in their structure—were used as dispersing agents. MWCNTs in powder form were dispersed in deionized water with sodium dodecyl sulfate, cetylpyridinium chloride, and triton TX-100. Three concentrations of each surfactant (1, 10, and 100 mM) were tested, and all samples were sonicated until an adequate dispersion degree was obtained. Cement pastes blended with carbon nanotubes were prepared, and their hydration kinetics were studied using the Vicat needle and isothermal calorimetry tests. It was concluded that the effect of MWCNTs on the hydration kinetics of portland cement can be masked by the effect of surfactants used as dispersing agents for the nanotubes in the mixing water.

It is important to further improve the microwave absorption capacity of bitumen to promote the application of microwave heating in pavement maintenance. $\mathrm{SiC}\text{-}{\mathrm{Fe}}_3{\mathrm{O}}_4$ composites were prepared as microwave-enhanced materials based on the impedance matching theory and the limitation of traditional single-phase microwave absorber. A network analyzer was used to measure the electromagnetic parameters. The rheological properties were evaluated and the morphological characteristics of $\mathrm{SiC}\text{-}{\mathrm{Fe}}_3{\mathrm{O}}_4$ composites were studied. The process of microwave-heating of bituminous concrete was simulated and the heating rate and heat distribution were analyzed intensively. The results showed that the reflection loss of bitumen containing $\mathrm{SiC}\text{-}{\mathrm{Fe}}_3{\mathrm{O}}_4$ composites reached $-21.82\mathrm{dB}$ (the microwave reflectivity was only 1%), which is 13.4 dB lower than that of the bitumen containing SiC. The average heating rate of the bituminous concrete containing optimum $\mathrm{SiC}\text{-}{\mathrm{Fe}}_3{\mathrm{O}}_4$ composites was $0.322°\mathrm{C}/\mathrm{s}$, which is 1.88 times of that of pure bituminous concrete, and higher than that of bituminous concrete containing either SiC or ${\mathrm{Fe}}_3{\mathrm{O}}_4$. $\mathrm{SiC}\text{-}{\mathrm{Fe}}_3{\mathrm{O}}_4$ composites improved the thermal conductivity of bituminous concrete, as well. The rheological properties of bitumen did not decline. The microstructure of $\mathrm{SiC}\text{-}{\mathrm{Fe}}_3{\mathrm{O}}_4$ composites contributed to microwave absorption. It can be concluded that the bitumen containing $\mathrm{SiC}\text{-}{\mathrm{Fe}}_3{\mathrm{O}}_4$ composites has stronger microwave-absorption ability compared with the bitumen containing a single-phase absorber. The bituminous concrete with composites had a greater microwave heating effect, and the optimum mass ratio of SiC to ${\mathrm{Fe}}_3{\mathrm{O}}_4$ was $1:2$.

Geopolymers exhibit high mechanical performance and low ${\mathrm{CO}}_2$ emissions, and have garnered interest in the construction sector. The brittleness of geopolymer matrices has led to a demand for materials to reinforce them and make them suitable for applications involving tensile or dynamic loading, such as reinforcements produced with 3D printing. However, the durability of polymers currently used in 3D printing in geopolymer matrices is unknown. The properties of polylactic acid (PLA) and poly(ethylene terephthalate)-glycol (PETG), when immersed in an alkaline solution that simulates the pore water of geopolymer matrices, were assessed with weight monitoring, Fourier transform infrared spectroscopy, thermal analysis, and direct tensile tests. The results showed that new carbonyl compounds are formed in the extension of the polymeric chains, which could be associated with the oxidation of the chains. PLA presented a weight loss of 35.83% and a decrease in tensile strength of 45.62%. PETG showed no significant changes in properties, indicating its good durability in geopolymer matrices.

This study investigates the use of the particle image velocimetry (PIV) technique and GeoPIV-RG software to track the localized axial and lateral strain development of composite geogrid specimens in a wide-width tensile test and to evaluate the load-strain response of the composite geogrid material. The effects of strain rate on the mechanical properties of composite geogrid specimens in both the machine direction (MD) and cross-machine direction (CMD) under tension were also investigated by performing tests under three different strain rates. The aperture at the center of the test specimen was suggested as the optimum location of the geogrid specimens to accurately measure strain development. The wide-width tensile test results revealed that the stiffness of the tested composite geogrid was independent of the strain rate and was comparatively higher than the manufacturer specified values. Therefore, these test results confirm that the crosshead method underestimates the tensile properties of geosynthetics in the wide-width tensile test. The findings suggest that cost-effective geotechnical structures can be designed adopting the tensile properties obtained from the GeoPIV-RG technique instead of the crosshead method.

A sandwiched foam concrete (FC) layer with good bond and thermal properties is crucial to the overall performance of a prefabricated insulation panel. In this study, the effects of grade and the dosage of fly ash (FA) on the dry density, specific strength, thermal conductivity, bonding strength, shrinkage, and moisture loss rate of high-belite sulphoaluminate cement (HBSC)–based foam concrete (HBFC) were investigated. The shrinkage differences between HBFC and portland cement-based foam concrete (PCFC) were also compared. The results show that the bonding strengths of HBFC doped with Grade-I and Grade-II FA are higher than that doped with Grade-III FA. When the Grade-III FA dosage is less than 5%, or the Grade-I and Grade-II FA dosage are less than 15%, the bonding strengths of HBFC meet the requirements of the prefabricated insulation wall panel. The shrinkages and moisture loss rates of HBFC in all groups increase fast within 24 h of curing. The 672 h shrinkages of the HBFC doped with all grades of FA increase with the FA dosage, which are still much lower than those of PCFC. The shrinkages of HBFC doped with Grade-I and Grade-II FA are lower than that with Grade-III FA, and the rule is the same as the moisture loss rates of the HBFC. HBSC doped with a 15% dosage of Grade-II FA is the most suitable binder for a preparing cost-effective HBFC panel with the dry density, specific strength, thermal conductivity, bonding strength, and 672 h shrinkage of being $302.9\mathrm{kg}/{\mathrm{m}}^3$, $\mathrm{1,276.6}\mathrm{N}·\mathrm{m}/\mathrm{kg}$, 0.0791 $\mathrm{W}/\mathrm{m}·\mathrm{k},0.128\mathrm{MPa}$, and $2.930\mathrm{mm}/\mathrm{m}$, respectively, and the corresponding cost for preparing $1{\mathrm{m}}^3$ of HBFC is about $41.30.

The process of obtaining chemically bonded phosphate ceramics generally involves the use of metallic oxides, the preparation of which consumes high quantities of energy. The present study proposes a method to recycle slags generated by a steel production process that is widely used across the world—the electric arc furnace. A chemically bonded phosphate ceramic is produced by exploiting the high content of metals present in the slag, realizing the conditions to mitigate the environmental impact of the industrial by-product. In situ infrared spectroscopy, isothermal conduction calorimetry, and X-ray diffraction revealed that the setting reaction involves the formation of amorphous products in the form of metallic phosphate hydrates and a fraction of calcium silicate hydrates similar to those found in portland cement. This phosphate matrix allows the effective immobilization of heavy metals in the slag, such as Cr and As. According to the results of mechanical tests, which showed compression resistance of $15–25\mathrm{MPa}$, and leaching tests, slag-based phosphate cement can be used without restrictions as a construction material for applications such as mortars or bricks.

Rutting is one of the most common types of asphalt pavement failures. This study has investigated the high temperature performance of asphalt binders incorporating graphene oxide (GO). To this end, frequency sweep, temperature sweep, and multiple stress creep recovery (MSCR) tests using a dynamic shear rheometer (DSR) were conducted on the control and GO-modified asphalt binders. Response surface methodology (RSM) based on a statistical model was used to investigate the interactive effects of three parameters, namely temperature, GO content, and loading frequency, on the rutting performance of the GO-modified asphalt and develop predictive mathematical models. Atomic force microscopy (AFM) was used to observe the microstructure of the binders. The results of the rheological tests showed that GO considerably enhanced the high temperature performance of the asphalt binder. The MSCR test results revealed that in comparison with the control asphalt, the GO modified binders presented lower nonrecoverable creep compliance ($J_{nr}$) and higher percent recovery ($R$) values, showing a significant contribution of the GO to rutting resistance. The statistical analysis showed that the selected input variables exhibited a notable impact on the complex modulus ($G^{*}$) and rutting behavior ($G^{*}/\sin \delta$) of the asphalt, and quadratic models were proposed for predicting the rutting potential. Finally, the AFM analysis demonstrated that GO was perfectly distributed in the asphalt matrix.

This study evaluates the alkali activation of a binary system composed of sugar cane bagasse ash and carbide lime as a green stabilization technique for bauxite tailings (BTs). To analyze the feasibility of this alternative binder as a stabilizer, mechanical tests were performed to measure the strength, stiffness, and durability of BT binder mixtures. As a control group, tailings were stabilized with high-initial-strength portland cement (Type III). The results show that the alternative binder is a suitable option to improve the mechanical behavior of bauxite tailings. The porosity/binder index ($\eta /B_{iv}$) was an appropriate parameter for evaluating BT stabilization. Reduced porosity and increased binder content (decreased $\eta /B_{iv}$) led to an improvement in the mechanical behavior of the studied mixtures.