Journal of Materials in Civil Engineering

The effects of fiber type and content on the properties of emulsified asphalt cold recycled mixture (ECRM) produced using vertical vibration compaction are examined. The reliability of the vertical vibration testing method (VVTM) is verified by comparing the physical properties of VVTM-prepared samples with those prepared via the Marshall compaction method (MCM) and with the mechanical properties of core samples from a construction site. Furthermore, the mechanical strength and pavement performance of ECRM with different fibers are tested. Finally, using the entropy-weight technique for order of preference by similarity to ideal solution (TOPSIS) model, the fiber type and content for the optimal comprehensive performance of ECRM are recommended. Results show that the correlation between the mechanical strength of the VVTM-prepared ECRM sample and construction site core sample is $>90\%$. An increase in fiber content first increases and then decreases the mechanical strength and road performance of the ECRM; its influence on water stability is not significant. With the same fiber content, the improvement effect of four fiber types on ECRM’s comprehensive performance is ordered as follows: lignin fiber > polyester fiber > mineral fiber > basalt fiber. Based on the entropy-weight TOPSIS model, 0.4% lignin fiber content is the optimal scheme for the comprehensive performance of ECRM. Overall, the results provide a reference for the fiber type and content selection for ECRM and have important engineering significance for improving ECRM’s comprehensive performance.

In this study, recycled concrete aggregate (RCA) from construction and demolition waste (CDW) was utilized in zero-slump concrete (ZSC) to produce M-40 grade paver blocks. Initially, coarse RCA (4.75 to 10 mm in diameter) replaced natural coarse aggregate (NCA) and fresh (slump, compaction factor, density) and hardened (compressive strength, water absorption, abrasion resistance) properties were investigated to optimize its replacement percentage. Then, the feasibility of incorporating RCA ($<4.75\mathrm{mm}$) was determined based on fresh and hardened properties, i.e., bulk density, compressive strength, flexural strength, split tensile strength, water absorption, void ratio, abrasion resistance, ultrasonic pulse velocity, and dynamic modulus of elasticity. Four samples of each formulation were tested, and the average was recorded with the standard deviation as the error bar. Microstructural analysis [thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM)] was conducted to validate the findings. The effects of RCA incorporation with respect to environmental impact [global warming potential (GWP) and primary energy (PE) consumption] of $1{\mathrm{m}}^3$ optimized ZSC mixes were assessed. As per observation, mechanical as well as durability properties degraded with increase in RCA content. Compressive strength decreased 17% at a combined replacement of 45% coarse and 100% fine RCA. Based on TGA analysis, portlandite content decreased with increasing RCA concentration, as confirmed by FTIR spectroscopy. SEM results also confirms the findings as pore counts, total area, average size, and percentage area increases with increase in RCA. Incorporation of 45% coarse and 100% fine RCA resulted in 4% and 8.8% decrease in GWP and PE, respectively. The optimized ZSC mixture (coarse 45% and 40% fine RCA) was based on an optimized compressive strength/GWP ratio. The production cost of $1{\mathrm{m}}^3$ concrete mix (45% coarse and 100% fine RCA) was 75% higher than the control mix because of the associated higher cost of RCA. Based on these findings, RCA can replace up to 45% NCA and 40% river sand without having a significant impact on its properties. Therefore, CDW can be viewed as a resource, not a waste, which can save natural resources and pave the way to sustainable development.

This work presents indirect tensile tests and uniaxial and triaxial monotonic and cyclic compression tests of Berea sandstone (BST) under different levels of confining pressure (CP) where the axial and lateral strains are measured in addition to the axial stress. Based on these experiments, the influence of the CP on the mechanical behavior and the damage mechanics of BST is investigated. Results reveal a strong influence of the applied CP on the strength of the material, where BST switches from brittle to ductile due to the presence of the CP. Damage-controlled tests are exploited to quantify the evolution of plasticity and damage as a function of the applied axial load, as well as the CP level. Experimental analysis imparts damage and plasticity rates with respect to the applied axial load to get lower as the CP increases. To the authors’ best knowledge, very little work has been conducted on carefully quantifying plasticity and damage of rocks, especially using cyclic loading at high confinements. The proposed experimental methodology in this work of damage and plasticity quantification delivers a baseline blueprint to refine triaxial experimental data for the sake of development and accurate calibration of advanced constitutive models.

This study aims to investigate the fatigue behavior and healing properties of aged asphalt binders. Both 70# and SBS-modified asphalt binders were aged using a rolling thin-film oven test (RTFOT), and their physical properties were analyzed. Their fatigue behavior and healing properties were investigated using a dynamic-shear-rheometer time-sweep test. The influence of healing on fatigue behavior was evaluated in terms of the fatigue life ratio (FLR), and a new index was defined (accumulated dissipation-energy ratio, ADER) to evaluate the healing properties of aged asphalt binders. Aging reduced the penetration and ductility of both the asphalt binders, and large aging degrees increased their softening points. Small aging degrees slightly decreased the softening point of the SBS-modified asphalt binder but increased that of 70# asphalt binder. The former had a better thermal-oxidative aging resistance than the latter. Aging increased the complex shear modulus of the binders, resulting in a longer fatigue life under controlled-stress conditions. The fatigue life of aging asphalt binders obeyed a good ($R^2>0.90$) double-logarithmic linear relationship with the stress level. Healing recovers the asphalt complex shear modulus and extends its fatigue life. Additionally, the FLR and ADER increased with a decrease in aging degree and an increase in the healing period.

A numerical framework to study the morphology change of microstructure and ionic diffusivity of leached cement pastes is proposed. According to a two-scale microstructure model, the leached cement paste in the course of portlandite dissolution and C─ S─ H decalcification is modeled. In contrast to recent leaching studies that used particle-based microstructure models to analyze micrometer-sized structures, the novel aspect of this study is the consideration of capillary pores with sizes ranging from tens of nanometers to several micrometers. The evolving microstructure was coupled with the random walk algorithm to calculate diffusion properties in capillary and gel pores of cement pastes during leaching and hydration. Results were in general accord with the reported data from leaching experiments and other simulations. The rarely discussed relationships the simulated 3D microstructure and the ionic diffusivity of leached cement pastes are investigated. In particular, the pore structure, which has different degradation characteristics in each leaching stage, affects the ionic diffusivity variously. The proposed framework has potential as a tool for multiscale simulation of leaching concrete.

Water pipe infrastructure, especially cast iron and asbestos cement, are close to or past their recommended service life. Rehabilitation of this existing water pipe infrastructure is critical to reduce replacement costs and water loss. Cured-in-place pipe (CIPP) liners are one method of pipe rehabilitation, and long-term properties are integral in the design of CIPP liners for water pipes. Limited studies have focused on testing and reporting of long-term properties, which are essential for the service life design of CIPP products. This paper aims to investigate the long-term properties of a CIPP liner under service conditions (static pressure and pressure transients). Three types of tests, namely, creep, creep rupture, and fatigue tests, were examined. Results indicated that the creep retention factor (0.18–0.27) at 50 years does not correspond to the long-term rupture tensile strength reduction factor (0.7) at 50 years. Long-term creep degradation curves show that, when subjecting the liner to constant stress, the short-term strength of the liner remains close to the initial tensile strength. The long-term strength reduction factor due to fatigue (0.73 at 100 million cycles) suggests this CIPP material is less influenced by pressure fatigue cycles. Therefore, the creep retention factor is not a true estimate of rupture strength or fatigue strength reduction.

Deep mixing method (DMM) has been widely used in geotechnical and highway engineering to stabilize soft soil foundations. The emerging material, one-part geopolymer (OPG), is environmentally friendly, which is promising to be used as an alternative binder to replace ordinary portland cement (OPC) partially or even completely for stabilizing the soft clay. In this paper, the dynamic shear modulus and damping ratio of the OPG-stabilized soft clay are investigated through the dynamic triaxial test. X-ray computed tomography (X-ray CT) is adopted to analyze the evolution of microstructure, especially the porosity distribution in OPG-stabilized soil samples. Factors affecting the dynamic behaviors of the OPG-stabilized soil, including the mass ratio of fly ash (FA) to ground granulated blast furnace slag (GGBFS), curing stress, curing time, confining pressure, cyclic-stress frequency, and cyclic-stress ratio (CSR) are studied. Results show that among all the mixing proportions, the sample with FA/GGBFS mass ratio of 0.1 could get the highest dynamic shear modulus and lowest damping ratio. With the curing stress increasing and curing time elapsing, dynamic shear modulus increases and the damping ratio decreases significantly. Furthermore, the higher the confining pressure is, the higher the dynamic shear modulus achieves. However, the higher confining pressure, such as 300 kPa, might disturb the original structure of the OPG-stabilized soil sample and then induce the breakage of bonding between hydration gels and soil particles, further causing the substantial loss of transmission energy. Finally, the higher cyclic-stress frequency would induce the larger shear strain of the sample under the given CSR, resulting in the lower dynamic shear modulus and higher damping ratio. The outcome of this study could provide guidance for the application of OPG binder in the ground improvement.

Modeling the postpeak behavior of brittle materials like concrete remains a challenge from the point of view of computational mechanics due to the strong nonlinearities arising in the material behavior during softening and the complexity of the yield criterion that may describe their deformation capacity under generic triaxial stress states. A numerical model for plain concrete in compression is formulated within the framework of the coupled elastoplastic damage theory. The aim is to simulate, via the finite-element (FE) method, the stress-strain behavior of concrete at the mesoscale, where local confinement effects generally characterize the cement paste under the action of the surrounding aggregates. The mechanical characterization of the components are accomplished through a specific experimental campaign. With the subsequent validation study, it is shown that a few calibration parameters give a good prediction of the material strength and deformation capacity encountered in real uniaxial compression tests.

Racking in asphalt pavements has always been the leading cause of pavement damage. This study aims at investigating the effects of mesostructure characteristics of asphalt mixture on the fracture behavior of semicircular bending (SCB) samples. To fulfill this objective, a two-dimensional (2D) finite-element model (FEM) of an asphalt mixture considering viscoelastic properties was established by using digital image processing (DIP) technology and a cohesive zone model (CZM). The FEM method was validated based on experimental results. On this basis, the whole process of crack initiation and propagation, the damage distribution of cohesive elements, and the effects of mesostructure characteristics (such as voids, interface strength between aggregate and asphalt mortar, and initial crack length) on damage and fracture behavior of SCB samples were analyzed. It was observed that with increasing porosity, the ultimate bearing capacity of the specimen decreased, and the cracks propagated towards the path with more air voids. The air voids far away from the crack propagation path had minimal effect on the ultimate bearing capacity of the specimen but could induce new damaged cohesive elements. With the decrease of the interface strength of aggregate-asphalt mortar, the maximum bearing capacity of the samples decreased, and the proportion of the cohesive elements with more significant damage at the interface increased accordingly. The resulting bearing capacity, fracture energy, and creep dissipation energy of the specimens reduced gradually with increasing initial crack length.

The high-temperature resistance of lightweight shale ceramsite concrete (LWSCC) is seriously underestimated because the effect of moisture is not considered. To investigate the mechanical properties and damage of LWSCC after a high-temperature treatment, strength tests, X-ray diffraction (XRD), and scanning electron microscopy (SEM) were carried out, and a nondestructive ultrasonic testing device was used to quantify the damage. The results show that the spalling characteristics of LWSCC at high temperatures were closely related to its water content. The axial compressive strength of LWSCC linearly decreased with increasing target temperature. LWSCC showed a greater resistance to high-temperature deterioration than NWC with the same mass loss ratio. LWSCC with a moisture content of 4.1% had a high probability of spalling at temperatures above 500°C. However, dry LWSCC had a low probability of spalling even when heated to 800°C. Water in shale ceramsite with a porous structure was identified as a critical factor in the high-temperature deterioration. After the temperature exceeded 200°C, the high-pressure steam in the ceramsite expanded the cracks. These findings provide a basis for designing LWSCC with high-temperature resistance and evaluating the safety of LWSCC buildings after fires.

Backscattered electron (BSE) images have been widely used to investigate the phases of cementitious materials. With the view of quantifying phases including pores, hydration products, and unreacted clinkers from the cementitious products, three quantification methods based on grey level thresholds have been proposed to segment phases from the BSE image. In this paper, these three phase-segmentation approaches, including frequency histogram method, overflow method, and Gaussian distribution method, are systematically studied and critically compared. Results show that the overflow method and the Gaussian distribution method outweigh the frequency histogram method in terms of human visual judgment, phases threshold, phases content, reconstructed image quality, and porosity. Furthermore, the overflow method seems to be more practical for phase quantification, producing comparable results to the Gaussian distribution method. The Gaussian distribution method possesses the potential for quantifying over three types of phases.

This study investigates the bonding behavior of modified ceramsite concrete (MLC) and basalt fiber-reinforced polymer (BFRP) bars exposed to dry-wet (D-W) cycles of simulated seawater using pull-out tests. Two types of concrete strengths—MLC25 and MLC35—were examined under different environmental exposure periods (0, 10, 30, and 50 cycles) using a total of 54 specimens. Compared with the specimens that were only immersed in artificial seawater (ASW, without D-W cycles), the D-W cycles had no significant effect on the failure mode, which remained as pull-out and splitting failures. However, the ultimate bond strength and slippage varied significantly, and the ultimate bond strength decayed between 5% and 35%, while the slippage increased from approximately 4% to 60%. The bond strength of LC35 decreased by 33.65%, and the slippage increased significantly (by 55%) after 50 D-W cycles (using one-time concentrated ASW). Moreover, the mechanical properties under this unconditional environment showed that the splitting tensile strength decreased by 3.67% and the compressive strength decreased by 5.47%.

Ultrahigh-performance concrete (UHPC) has been considered for a variety of structural engineering applications, owing to its superior strength and durability. Among the main properties of UHPC, flexural performance characteristics largely depend on the type and dosage of fibers incorporated into the mixture. Noting this critical aspect and the fact that the availability and cost of fibers directly contribute to choosing UHPC over other cementitious composites, this study explored the possibility of a partial replacement of steel fibers conventionally used in UHPC mixtures with synthetic fibers. With a focus on workability and strength properties, a total of 15 mixture designs were developed, investigating five different synthetic fibers, including nylon, polypropylene, polyvinyl alcohol, alkali-resistant glass, and carbon fibers. Three mixtures were prepared for each fiber type by varying the dosages of synthetic and steel fibers. From the conducted tests, load-deflection curves were extracted, further to flexural strength and toughness characteristics. To properly understand the progress of crack formation and propagation, as well as the effectiveness of various fibers in the postcracking response of UHPC, the obtained results were paired with digital image correlation data. Through holistic comparisons, the outcome of the presented study provided original information on the extent of contribution of some of the most common synthetic fibers to the strain distribution, crack resistance, and flexural performance of UHPC.

The wide application of surfactants in cement-based materials requires the understanding of the influence of surfactants on the structure and properties of C–S–H gel. In this study, cation surfactants (CTAB) and anion surfactants (SDS) in ionized type are successfully intercalated into C–S–H gel, generating different molecular models through molecular dynamics simulation. Systematic analysis and quantitative description were performed on the molecular structures, bonding properties together with deformation and fracture mechanisms. It was found that the majority of ${\mathrm{Br}}^{–}$ ionized from CTAB could interact with Ca_interl, forming ${\mathrm{Br}}^{-}-\mathrm{Ca}\text{\_}\text{interl}$ bonds. Smaller ${\mathrm{Na}}^{+}$ ionized from SDS could bond with both O_bri and O_nbri atoms, while ${\mathrm{O}}^{–}$ and O atoms in SDS anions could interact with Ca_interl atoms as well. It is noteworthy that the intercalation of CTAB into C–S–H gel promotes the diffusion of water molecules, whereas the intercalation of SDS into C–S–H gel inhibits the diffusion of water molecules. Uniaxial tensile simulation results reveal that the breakage of both H_water–O_water hydrogen bonds and Ca_interl–O_water bonds dominates the failure process of CTAB/C–S–H gel, while the breakage of H_water–O_water hydrogen bonds governs the fracture of SDS/C–S–H gel.

As an inorganic–organic composite material, cement and emulsified asphalt (CA) mortar has been used widely in ballastless slab track structures, and its performance is influenced significantly by environmental conditions. In this study, we tested the long-term creep of CA mortar at different temperatures using a self-designed loading device, and explored the mechanisms by which high temperatures influence CA mortar creep based on several microscopic testing methods. The results indicated that high temperatures cause the creep degree and rate of CA mortar to increase significantly. Subsequent to creep at high temperatures, the mechanical properties and microstructure of CA mortar changed remarkably, and asphalt migration may be an important cause of changes in CA mortar at high temperatures. This will be useful for future studies of the evolution of CA mortar performance under long-term service conditions.

Estimation of multiscale elastic parameters is of significance for precise design of cementitious material performances, which depends on the materials’ mineral compositions and microstructures. Nanoindentation technology coupling with statistical analysis is an advanced method to probe the mechanical properties of mineral phases, which bridges the equivalent performance of block cementitious materials by upscaling and the microstructures of minerals by downscaling. In this study, grid nanoindentations and mercury intrusion porosimetry (MIP) were performed on cement paste samples with typical water/cement ratios to obtain the elastic modulus of microscopic phases and porosity. Then, upscaling calculation of equivalent elastic modulus was carried out by homogenization methods including dilute method, Mori-Tanaka (M-T) method, self-consistent method, and interaction direct derivation (IDD) method. Comparing calculations with macrotests of elastic modulus, the results are in good agreement with experiment results after considering the effects of capillary pores, especially by the self-consistent method and IDD method. Furtherly, regression analysis using the self-consistent method was employed to obtain the intrinsic elastic modulus of calcium silicate hydrate (CSH) monomers and packing density of CSH clusters, which is in agreement with reported simulation results by molecular dynamics. This work established the relationships quantitatively among gene minerals with special nanostructures, microstructures of cement pastes and macroelastic performances of block cement materials by a multiscale calculation framework across micro-meso-macroscales, offering a foundation for further multiscale design of high-performance construction materials in civil engineering.

This work assessed the effect of compressive fatigue on sulfate ion diffusion in standard-cured and steam-cured concrete containing slag. After compressive fatigue, the slag concretes were immersed in 5% sodium sulfate solution for 18 months. The sulfate ion content in concrete was measured and the sulfate ion effective diffusion coefficient was calculated. The results showed that compressive fatigue accelerated sulfate ion diffusion in concrete, and the acceleration was more prominent in steam-cured concrete than standard-cured concrete. During sulfate attack, the sulfate ion content in the same layer of standard-cured fatigued concrete grew with an increase in stress level. Massive ettringite with large size was generated in steam-cured fatigued concrete during sulfate attack. In addition, a sulfate ion diffusion model of fatigued concrete was established. Based on this model, the measured values agreed well with the simulated distribution curve of sulfate ions in fatigued concrete.

Ultra-high-performance fiber reinforced concrete (UHPFRC) exhibits strain hardening and multiple cracking behaviors when subjected to tension load. There are limited studies on the effect of steel fiber aspect ratios on the tensile performance of UHPFRC. Also, tensile testing of cementitious materials and composites is challenging due to the lack of a standardized direct tensile testing method with wide variation. This study experimentally investigated the effect of hooked end and straight steel fiber aspect ratios on the tensile behavior of UHPFRC with a 2% fiber volume fraction. A direct tensile test setup was first developed to obtain good alignment and desirable experimental data in an attempt to overcome some of the difficulties with other tensile tests. UHPFRC failure modes, stress-strain relationships, initial cracking strength, and peak strength, as well as stress–crack width relationships, were characterized and analyzed. The developed tensile test results showed that, as the aspect ratio of the hooked end fiber increased, the ductility ratio and the characteristic stress increased. However, the effect of the straight fiber aspect ratio on tensile behavior was not more significant than that of the hooked end fiber aspect ratio. Over-large straight fiber aspect ratios led to a reduction in characteristic stress and ductility ratio and an acceleration of crack propagation in the early softening phase. In comparisons of the developed direct tensile test and other test methods in terms of peak strength, the small-scale briquette tensile test showed the potential to become an alternative to conservatively evaluate UHPFRC composition strength of.

As a promising environmentally friendly construction material that can be used to replace concrete, fly ash-based geopolymer (FABG) should meet the working strength requirement. However, the optimal mixture design of FABG could be difficult to obtain through experimental methods due to a variety of influential factors and their complex interrelationships. To address this problem and explore the influence patterns of those factors, this study developed an ensemble machine learning modeling method that integrated three algorithms: support vector regressor (SVR), random forest regressor (RFR) and extreme gradient boosting (XGBoost). A database containing 896 experimental instances was constructed by reviewing open resources. During the modeling, established estimators were tuned with a metaheuristic algorithm called differential evolution (DE). After analysis, the XGBoost model was determined as the strength prediction model of FABG, because it showed the best performance with the largest ${\mathrm{R}}^2$ scores (0.97 and 0.91) without overfitting by the minimum mean absolute error (MAE) gap between the training and testing subsets. Additionally, a further understanding of how the factors affect the predicted values of the model was given by the SHapley Additive exPlanations (SHAP) theory. The results show that curing conditions had the biggest impact on the model output, followed by alkali-activator solution variables and the mole of sodium hydroxide. Therefore, the proposed method can accurately predict the strength of produced FABG and assist in understanding the influence patterns of various factors.

Recycled coarse aggregates (RCAs) are widely used as a sustainable material in the construction sector. However, the variability of the material is the main factor that limits its use in practice. This paper investigates the effectiveness of RCA selection by an air jigging process in concrete. The performance was assessed with compressive strength and durability indicators from natural and accelerated carbonation tests. The RCA used was provided by two recycling plants. Air jigging technology reduced the mortar and ceramic content in RCA; hence, it increased the strength of the jigged material relative to concrete without air jigged RCA. However, jigging RCA resulted in natural and accelerated carbonation coefficients up to 2.5 times higher than concrete made with natural coarse aggregate. The treatment of RCA by air jigging technology enhanced the properties of concrete, achieving additional benefits compared with nontreated material. Furthermore, the existing models that provide a correlation between accelerated and natural results of carbonation depth and current international standards do not apply to RCA. Therefore, modifications of these models were carried out to enhance the service life prediction of RCA concrete.

When added to aged bitumen, oil-based rejuvenators are expected to restore its original properties to some degree. The extent of the rejuvenation depends on the composition of the oils. In this study, the effect of individual components of vegetable oils on blends with bitumen was investigated. First, 5% and 10% by weight of two free fatty acids, namely oleic acid and linoleic acid, and one triglyceride, triolein, were blended with bitumen, and thereafter, the blends underwent thermal aging at high temperatures under air in a ventilated oven. The fatty acids and triglyceride are referred to as rejuvenators in this context. Upon thermal aging, the free fatty acids did not produce any effect or were much less effective in decreasing the complex shear modulus (stiffness) of bitumen compared with the triglyceride. One reason for this result may be the favorable chemical changes of the triglyceride at high temperatures compared with the free fatty acids. Above all, this study provides basic knowledge to demonstrate the importance of the chemical composition of vegetable oils that are selected as bitumen rejuvenators, specifically when targeting long-term stability of the blends.

Portland cement composites modified with hydrothermal ${\mathrm{SiO}}_2$ nanoparticles (0.01–3.0 wt.%) and basalt microfiber (1.5 wt.%) with $\mathrm{W}/\mathrm{C}=0.4$ were developed. At different doses of ${\mathrm{SiO}}_2$ nanoparticles aged 1–28 days in combination with the microfiber, the compressive strength ${\mathrm{F}}_{\mathrm{com}}$ (up to 51.1 MPa, 1.5 times higher than the specimen without nanoparticles and microfiber) and flexural strength ${\mathrm{F}}_{\mathrm{flex}}$ (up to 13.2 MPa, 3.4 times) after 28 days of aging were determined. In addition, the impact viscosity, the number of blows before the first fracture ${\mathrm{N}}_{\mathrm{ff}}$ and before ultimate failure ${\mathrm{N}}_{\mathrm{cd}}$, impact coefficient ${\mathrm{N}}_{\mathrm{iv}}{=\mathrm{N}}_{\mathrm{cd}}/{\mathrm{N}}_{\mathrm{ff}}$ (up to 30; 2.72 times), and specific energy of impact destruction (up to $199.4\mathrm{kJ}/{\mathrm{m}}^2$, 22.2 times) were calculated. Synergetic effects of the combined action of different scale modifiers on ${\mathrm{F}}_{\mathrm{flex}}^{28}$ (1.29 times) and on ${\mathrm{N}}_{\mathrm{cd}}$ and ${\mathrm{E}}_{\mathrm{im}/}{\mathrm{S}}_{\mathrm{c}}$ (1.95 times) were revealed. Statistical correlations with high ${\mathrm{R}}^2$ values were obtained between the characteristics, $({\mathrm{N}}_{\mathrm{cd}}{,\mathrm{N}}_{\mathrm{ff}}{)–(\mathrm{F}}_{\mathrm{com}}^{28}{,\mathrm{F}}_{\mathrm{flex}}^{28})$ and (${\mathrm{F}}_{\mathrm{flex}}^{1,7,28}$, ${\mathrm{F}}_{\mathrm{com}}^{1,7,28}$), (${\mathrm{N}}_{\mathrm{ff}}$, ${\mathrm{N}}_{\mathrm{cd}}$, ${\mathrm{N}}_{\mathrm{iv}}$) and dose of ${\mathrm{SiO}}_2$ nanoparticles, which can used for the design of concrete structures and reduction of cement consumption. The mechanism of the strong synergetic effect of this combination can be explained by the increased volume fraction of the high density (HD) phase of the calcium silicate hydrates (CSH) gel with more packed nanogranules in a basic volume of cement matrix and interfacial transition zone (ITZ) and the increase in the shear stress of the CSH gel relative to the lateral microfiber surfaces inside the HD phase volume.

In order to develop an environment-friendly asphalt rejuvenator, waste vegetable oil (WVO) was selected as the base oil. The composition of the rejuvenator was first designed based on the response surface methodology (RSM), and 16 groups of rejuvenator samples were obtained. Then, these samples were used to regenerate aged asphalt and 16 groups of rejuvenated asphalt samples were prepared. Afterward, the viscous, conventional, rheological, and fatigue resistance properties of these rejuvenated asphalts were measured and evaluated, and the optimal composition of rejuvenator was determined. Results show that the addition of WVO-based rejuvenator can reduce the viscosity and softening point of aged asphalt, increase its penetration and ductility, and restore the physical properties and viscosity of aged asphalt to that of original asphalt. With the addition of WVO-based rejuvenator, the high-temperature performance of aged asphalt gradually declined, but the rejuvenator with optimal composition can restore its high-temperature performance to the similar level as original asphalt. The addition of WVO-based rejuvenator can evidently improve the fatigue damage resistance and low-temperature cracking resistance of aged asphalt, achieving a good regeneration effect. The fitting equation based on RSM can achieve an accurate and reliable prediction on the viscous, conventional, rheological, and fatigue damage properties of rejuvenated asphalt. According to the results of model optimization, the optimal composition of WVO-based rejuvenator is recommended as WVO:Dibutyl phthalate (DBP):antiaging agent (AA) = 90:9:1.

In this study, the acid resistance characteristics of commercial aggregates that are commonly employed in concrete construction, were investigated. The aggregates studied were of three categories, namely: (1) the siliceous group consisting of reef–quartzite, metaquartzite, and granite, (2) the siliceous–calcareous group consisting of dolerite and amphibolite, and (3) dolomite of the calcareous group. Samples of the aggregates were oven-dried, immersed in 20% by weight concentration of hydrochloric or sulphuric acid maintained at 60°C for 24 h, and then their mass loss values were measured. Mineralogical compositions and phase reaction changes in the aggregates were examined using X-ray fluorescence, Rietveld quantitative X-ray diffraction analysis, petrography, and scanning electron microscopy coupled with energy dispersive spectroscopy. A strong, nonlinear inverse correlation was found between quartz content and mass loss, for which aggregates that had ${\mathrm{SiO}}_2\ge 70\%$ exhibited very low or negligible mass loss. Metaquartzite and granite aggregates of the siliceous group showed the most superior resistance responses to acid attack, owing to their high levels of quartz content. Reef–quartzite, dolerite, and amphibolite all showed a partial or moderate level of acid resistance. Dolomite exhibited high susceptibility to acid attack, forming gypsum as a reaction product upon exposure to sulphuric acid.

To solve the inherent brittleness of magnesium phosphate cement (MPC)-based composites, we incorporated polyvinyl alcohol (PVA) fibers to develop tensile strain hardening fiber reinforced magnesium phosphate cement composites (SHFRMC). The effects of fly ash (FA) content, PVA fiber volume fractions ($V_f$), the sand to binder mass ratio (S/B), and the water to solid mass ratio (W/S) on the workability, compressive strength, and tensile properties of the SHFRMC were studied. Lastly, the micromorphology of PVA fibers and their bonding with the matrix was examined by the optical microscope test. Generally, when the FA content is 30%, the SHFRMC can achieve relatively high strength and strain capacity while maintaining good workability; the SHFRMC can achieve relatively high workability, strength, and strain capacity when the $V_f$ is 1.8%; when the S/B is 0, the workability, strength, and strain capacity of the SHFRM are the highest; and when the W/S is 0.13 or 0.16, the SHFRMC can achieve relatively high strength and strain capacity while maintaining good workability. The results revealed that a trade-off was needed among the workability, compressive strength, direct tensile stress, and tensile strain. The optical microscopy test showed that PVA fiber connects well with the matrix and plays an important bridging role in the tensile process to bear stress and restrain crack development, resulting in multicracking.

Using new techniques based on atomic force microscopy (AFM) and scanning electron microscopy (SEM), the stiffness, thickness, and microstructures of the shell of air bubbles extracted from air-entrained cement paste were examined, and coalescence resistances of pairs of bubbles were measured. The surface tension of air-entraining admixture (AEA) solutions in water and lime water also was determined. The results showed that air bubbles associated with synthetic AEAs had thinner and more-flexible shells than those with neutralized vinsol resin (NVR). The stiffness and thickness of the bubble shells were shown to be correlated with the differences in the stability of air bubbles in concrete among the same AEAs reported in a previous study. A mechanism leading to the differences in bubble shell properties between the AEAs is proposed based on the results of the surface tension testing and the particle-stabilized bubble theory, but further work remains to verify and refine this potential mechanism.

The interfacial transition zone (ITZ) in concrete is a layer of highly porous cement paste along the aggregate boundary and has a significant influence on the properties of concrete. Existing studies consider uniform thickness of the ITZ around the aggregate, which is not an actual representation of ITZ microstructure. Assuming uniform ITZ thickness around the aggregate leads to overestimating the volume fraction of the ITZ and, subsequently, its influence on the mechanical behavior of concrete. The local ITZ thickness depends on several factors such as water–cement ($w/c$) ratio, interaggregate distance, size, spatial distribution, and hydration of cement particles. The present work aimed to develop an analytical approach to incorporate differential ITZ thickness around the aggregate. The porosity profiles of cement paste between the two neighboring aggregates was investigated to predict ITZ thickness as a function of $w/c$ ratio, interaggregate distance, spatial distribution, and hydration of cement particles. Voronoi tessellation was used to assign differential ITZ thickness around the aggregates. Furthermore, a formulation for predicting ITZ volume fraction that incorporated differential ITZ thickness was proposed. The variation in ITZ volume fraction with different parameters such as maximum and minimum size of aggregate, volume fraction of aggregate and $w/c$ ratio was investigated. The elastic modulus of the concrete was calculated using a four-phase generalized self-consistent scheme to validate the proposed approach with the experimental results. The study found the ITZ thickness to be 7–21 μm and have a weak correlation with the spatial distribution of cement particles between the aggregates. The effect of the ITZ on the modulus of elasticity of concrete was negligible in concrete with low aggregate volume fractions.

The purpose of this study is to clearly understand the self-organized critical phenomenon of concrete in the process of uniaxial compression. During the compression tests, acoustic emission (AE) waveform and its characteristic parameters were collected synchronously. The AE characteristic parameters information entropy was defined by combining information entropy theory with AE characteristic parameters in the time domain and frequency domain. Moreover, the evolution law of the AE characteristic parameters weighted information entropy composed of typical characteristic parameters in the time domain and the AE peak frequency information entropy in the frequency domain are obtained during the loading process. The results reveal that, as the stress grows, the AE characteristic parameters weighted information entropy of concrete shows an evolution characteristic of “descending, stabilizing and rising,” while the AE peak frequency information entropy shows the evolution characteristic of “ascending and declining.” Meanwhile, as the AE characteristic parameters weighted information entropy reaches the minimum value ($\mathrm{e}\approx 0.9$ peak stress), the critical state of concrete ends. After that, the information entropy value increases rapidly, and the penetrating cracks initiate. When the specimen is destroyed, the information entropy value reaches the maximum. The evolution process of cracks in concrete, switching between a chaotic state that develops in random and an organized state that develops in order, follows certain laws (disordered–ordered–disordered), which corresponds well to the AE characteristic parameters weighted information entropy. The research results provide a new method for concrete damage monitoring based on AE.

Electromagnetic waves (EMWs) absorption cement composites were widely demanded in urban construction in the near future with increasingly serious electromagnetic pollution in rapid development and application of electronic communication technology. To fully utilize the influence of graphene nanoplates (GNPs) and ${\mathrm{Ni}}_{0.4}{\mathrm{Zn}}_{0.6}{\mathrm{Fe}}_2{\mathrm{O}}_4$ on EMWs absorption properties of cement composites, various dosages of dispersed GNPs, ${\mathrm{Ni}}_{0.4}{\mathrm{Zn}}_{0.6}{\mathrm{Fe}}_2{\mathrm{O}}_4$, and hybrid mixtures were incorporated in cement, and the electromagnetic reflectivity loss, electromagnetic parameter were tested and discussed in the frequency range of $2–18\mathrm{GHz}$. Also, the effects of GNPs and ${\mathrm{Ni}}_{0.4}{\mathrm{Zn}}_{0.6}{\mathrm{Fe}}_2{\mathrm{O}}_4$ on complex permittivity, complex permeability of cement composites were analyzed for further mechanism analysis combined with XRD, MIP, and SEM micrographs. The results showed that 1.0% GNPs and 30% ${\mathrm{Ni}}_{0.4}{\mathrm{Zn}}_{0.6}{\mathrm{Fe}}_2{\mathrm{O}}_4$ were the optimal dosages in cement composites, which could absorb more than 80% incident EMWs energy in 8–18 GHz. Furthermore, the ${\mathrm{GNPs}/\mathrm{Ni}}_{0.4}{\mathrm{Zn}}_{0.6}{\mathrm{Fe}}_2{\mathrm{O}}_4$ (1%, 30%) cement composites exhibit lower EMWs reflectivity loss compared to GNPs or ${\mathrm{Ni}}_{0.4}{\mathrm{Zn}}_{0.6}{\mathrm{Fe}}_2{\mathrm{O}}_4$ added individually, and the effective absorption frequency width (lower than $-10\mathrm{dB}$) was 5.4 GHz, of which more than 90% EMWs energy was translated to thermal energy and absorbed by the matrix, reaching similar EMWs absorption effect of absorption coating materials. Essentially, the imaginary part of complex permittivity and the real part and imaginary part of complex permeability of cement composites could be improved conspicuously when ${\mathrm{GNPs}/\mathrm{Ni}}_{0.4}{\mathrm{Zn}}_{0.6}{\mathrm{Fe}}_2{\mathrm{O}}_4$ was incorporated, indicating higher dielectric loss angle tangent and magnetic loss angle tangent of cement composites achieved. Thus, the impedance matching, dielectric loss, and the magnetic loss of cement composites under incident EMWs increased.

The tensile mechanical properties of hydraulic asphalt concrete (HAC) play a significantly important role in the safety of the impervious core in embankment dams. This paper aims to develop a direct tensile test setup with temperature control, to devise the direct tensile test method for HAC, and to investigate the direct tensile properties of HAC in a temperature range of 0°C–20°C and a strain rate range of ${10}^{-5}{-10}^{-2}{\mathrm{s}}^{-1}$. Through a large number of direct tensile tests, the shape and size of the specimen and the connection mode between the clamp and the specimen were designed. The test results show that the temperature and the strain rate significantly affect the tensile stress–strain characteristics of the HAC. As the temperature decreased from 20°C– 0°C or the strain rate increased from ${10}^{-5}{-10}^{-2}{\mathrm{s}}^{-1}$, the tensile strength, the tensile modulus, and the aggregate cracking ratio increased, whereas the peak strain declined. Moreover, the empirical formulas for the tensile strength, tensile modulus, and peak strain were successfully derived by applying the time–temperature superposition principle. The coefficient of determination was more than 0.95, indicating that the modeling data well agreed with the test results. Finally, according to the Mohr–Coulomb criterion, the effect of the temperature on the cohesion and the internal friction angle was analyzed at the various strain rates. The obtained test results can provide a reference for the design of asphalt concrete cores in embankment dams.

In this work, a porous road base material was studied for a load-bearing water-storing road. According to the performance analysis, asphalt and ordinary portland cement did not work well on the load-bearing water-storing road as base binder materials. Therefore, a metakaolin-based (MK) geopolymer was used to produce a concrete composed of geopolymer and open-graded aggregate (CGOA) as a new road base material to replace traditional cement-treated aggregate. The geopolymer gel adhesive ability, geopolymer surface cracks and internal pores, CGOA water stability, CGOA water storage rate, and CGOA unconfined compressive strength (UCS) were indicators to get the optimal formulation and production process. Mixing open-graded aggregates with a geopolymer gel [Si/Al mole ratio (MR) of 2, Al/Na MR of 0.85–1.00, and ${\mathrm{H}}_2{\mathrm{O}/\mathrm{Na}}_2\mathrm{O}$ MR of 14–16], and then membrane curing for more than 60 h at 20°C could produce the desired CGOA. It was designed to make it possible for the road to act as a superior reservoir while bearing traffic loads to reduce waterlogging in urban areas.

Hot-mix epoxy asphalt has superior performance as bridge deck pavement material. However, its high cost hinders the application of epoxy asphalt in road pavement. This study investigated the effects of epoxy resin contents on epoxy asphalt performance, aiming to seek out a cost-effective proportion. Specifically, the macromechanical properties, chemical compositions, and microstructure transformation of epoxy asphalt were evaluated by a tensile and viscosity test, Fourier transform infrared spectroscopy (FTIR) test, and fluorescence microscopy test, respectively. Finally, a brief cost analysis was conducted. Results indicate that when the epoxy resin content exceeds or equals 40%, both tensile strength and elongation of epoxy asphalt meet the performance requirements regulated in the specification. In addition, the enhanced epoxy resin content may also boost the viscosity-increasing rate of epoxy asphalt, especially at high temperatures. Furthermore, the areas of 1,085, 1,108, and $\mathrm{1,118}{\mathrm{cm}}^{-1}$ wavenumbers of epoxy asphalt infrared spectrum demonstrate good positive correlations with the epoxy resin contents. Besides, according to the fluorescence microscopy test result, after the curing process, the initial spherical epoxy resin particles tend to agglomerate, and a cross-linked spatial structure may form when the epoxy resin content exceeds or equals 40 wt%. Finally, combining the performance and cost analysis, the 40 wt% epoxy resin content can achieve a good balance between the material cost and pavement performance.

To inhibit the multiphase combustion characteristics of polymer-modified bitumen (PMB) at high temperatures, a new composite flame retardant with synergistic effects was developed based on the gradient distribution of combustion temperature ranges of four bituminous fractions: saturates, aromatics, resins, and asphaltenes (SARA). Expanded graphite (EG), ferrous hypophosphite (FHP), ammonium polyphosphate (APP), and zinc borate (ZB) were chosen to match the combustion temperature range of every bituminous fraction in turn, so that each bituminous fraction combustion behavior was inhibited by the corresponding flame retardant constituent. The optimized compounding scheme of the composite flame retardant was confirmed, and its inhibitory effects on bituminous combustion were examined using cone calorimeter tests. Test results showed that when the mixed proportion of EG, FHP, APP, and ZB was 1:3:3:4 by weight, the prepared composite flame retardant showed multiphase synergistic inhibitory effects during the entire bituminous combustion, obviously increasing bituminous flame retardancy. Simultaneously, the composite flame retardant presented greater smoke-suppressing effects during bituminous combustion. A thick pyknotic continuous carbon layer was formed on PMB after adding the composite flame retardant, and it played a flame-retarding role in the gas and condensed phases and also suppressed smoke release during bituminous combustion.

Roads constructed over poor ground conditions that carry high traffic volumes and axle loads may, over time, experience persisting occurrences of pavement distress. Road construction, be it a new or a rehabilitation project, is both costly and time-consuming. An appealing option that improves pavement durability, reduces construction cost and time, accelerates strength development over a short curing period, and decreases pavement thickness is to chemically stabilize local road materials. In contrast to other aggregate materials, there has been a gap in evaluating and quantifying the feasibility of chemical stabilization of sandstone aggregate that possesses marginal quality as a road construction material. Therefore, the aim of this paper is to provide an experimental investigation of relative strength development of sandstone aggregate subbase of marginal quality stabilized with combinations of Portland composite cement (PCC), ordinary Portland cement (OPC), and styrene–butadiene latex copolymer (or polymer). The samples were prepared with different gravel-to-sand (G:S) ratios of 2.1, 1.2, and 0.4 and subsequently stabilized with a polymer-cement (P/C) blend. Samples were compacted and cured under dry and wet conditions before measuring their unconfined compressive strength (UCS), indirect tensile strength (ITS), and California bearing ratio (CBR). At the same curing condition and P/C contents, it was found that the UCS and CBR of P/C-stabilized samples increased with increasing G:S ratios. At the same polymer and cement contents, the P/C-stabilized samples with the highest G:S ratio of 2.1 also demonstrated a significantly higher rate of UCS strength development compared with the samples with lower G:S ratio and unstabilized samples. Soil stabilization with a combination of 0.75% polymer and 5% cement contents yielded the highest UCS that was approximately seven times the UCS of unstabilized samples and an ITS of 0.73 MPa. Stabilization with a combination of 0.75% polymer and 3% cement contents yielded the highest CBR value that significantly exceeded 30% after only 4 days of soaking and was seven times that of unstabilized samples. This paper has thus demonstrated the potential improvement to the strength development of sandstone aggregate subbase stabilized with P/C blend under the optimal curing condition and the importance of identifying and using the optimal proportion of polymer and cement to achieve the target strength development and improvement.

To explore the potential application of high-performance viscosity-modifying admixtures (VMAs) is of great importance. In this work, the effects of the adsorption group and molecular weight of VMAs on the properties of fresh cement paste were studied. A series of copolymers having similar molecular weights but different adsorption groups (carboxyl, sulfonic, and quaternary ammonium groups) were compared for the first time. A series of copolymers having the same chemical structure but different molecular weights were also compared. The adsorption, fluidity, bleeding, and rheological properties of the fresh cement paste mixed with different copolymers were tested. The results show that the copolymer, having stronger adsorption group (carboxyl group) and higher molecular weight, could decrease the bleeding and fluidity while enhancing the stability of the fresh cement paste more effectively. The study may help explore ideal materials for the design and preparation of synthetic polymer VMAs.

Material resistance and performance are determined by the failure criterion for an asphalt mixture, affecting the scientific design of pavement. Conventional tensile, compression, bending, and split tests for asphalt mixture cannot fully reflect the complex stress and strain state of the pavement structure. In this paper, double confining pressure triaxial tests were performed on asphalt mixtures to generate three-dimensional complex stress states. In octahedral stress space, a failure criterion was established featuring the tensile and compressive meridians as well as the failure envelope curve. According to the generalized Hooke’s law (GHL), a transformed three-dimensional strain failure criterion model (FCM) was established and its accuracy was validated by the axial strain. The correlation function between stress and strain FCMs was proposed. According to the elastic layered system theory and the principle that the load response is less than the structural resistance, a three-dimensional load check was performed on a typical asphalt pavement structure. The results show that top-down cracks tend to appear in the inner edge of the load at the top of the upper surface layer. This research provides theoretical support for the study of the characteristics of asphalt mixture strength and pavement design under complex stress conditions.

Spent fluid catalytic cracking (SFCC) is an industrial waste from oil refineries that is increasing nonstop in Vietnam and many places globally, and needs to be recycled. However, SFCC has various compositions depending on the fluid catalytic cracking (FCC) types and additives in the petroleum-refining industry. Thus, an experimental optimization procedure is needed to find the optimum addition of SFCC as a filler powder for asphalt–concrete mixtures. For this requirement, the study objective was an optimization procedure based on Taguchi parameter design employing an $MMDC$ parameter. $MMDC$, developed using a robust multivariate statistical method called principal component analysis (PCA), is a representative parameter of required performance quality proposed by the Marshall mixture design. The Marshall mixture design was used to verify the asphalt–concrete mixture in which SFCC filler partly replaced traditional limestone (LS) filler. The effect of LS filler rate on mixture characteristics was used to determine the required range of values of $MMDC$. Also, Marshall characteristics based on various SFCC filler rates verified the optimum methodology result. The confirmation experiment results showed that the approach could find an optimum case with advantages in reducing asphalt binder content in the mixture and the number of specimens in the laboratory. Furthermore, the experimental results indicated that SFCC filler could enhance the Marshall characteristics of an asphalt–concrete mixture.

The objective of this study was to develop a simplified process and tool to assess the potential performance of Hot Mix Asphalt (HMA) mixtures in terms of rutting, fatigue, and thermal cracking, using only asphalt mix design information and volumetric data. Recent HMA mixture design data was collected from 25 states within the US and then compared to equivalent historical data available in the Long-Term Pavement Performance (LTPP) database for highways. The data was separated according to the four climatic regions within the LTPP and performance was assessed using existing predictive models. Three predictive models were used in the evaluation and comparison process. Then, four ranking criteria were developed to support the evaluation of the mix designs quality: Low, Satisfactory, Good, or Excellent. The evaluation results were reasonable based on the predictive models’ findings and the performance found in the LTPP. Out of the 48 HMA mixture designs studied, the majority were ranked either Satisfactory or Good. The overall results showed that state agencies have changed their mix designs over the years for the better, especially when considering fatigue cracking and rutting resistance. The methodology and criteria developed in this study are intended to be used as support tools in determining the quality of asphalt mixtures accepted by state agencies or local governments. They provide a quick insight on the needed improvement/modification against the potential development of distress during the lifespan of the pavement structure.

Geopolymers have been long recognized as the next-generation building material due to environmental reasons. However, geopolymers are inherently brittle and usually require high-temperature curing. This paper was intended to develop a ductile engineered geopolymer composite (EGC) under ambient curing conditions. Two types of metakaolin powder with different particle sizes were applied as the solid precursor. The tensile, compressive, and flexural behaviors of EGC with different mix designs were investigated. It was concluded that the combinational application of coarse and fine metakaolin is conducive to the tensile and compressive behaviors of EGC materials. As the alkali concentrations increased from 6 to $14\mathrm{mol}/\mathrm{L}$, the tensile and compressive strength of EGC increased, whereas the tensile ductility of EGC decreased gradually. Also, the ${\mathrm{SiO}}_2/{\mathrm{Na}}_2\mathrm{O}$ molar ratio had negligible influence on the tensile behavior of EGC, whereas the compressive strength decreased with the increase of ${\mathrm{SiO}}_2/{\mathrm{Na}}_2\mathrm{O}$ molar ratios. A numerical model to predict the flexural behavior of EGC was also proposed, and the accuracy was verified with experimental results.

A total of 65 Z-shaped ultrahigh-performance concrete (UHPC) specimens with monolithic interfaces, flat-wet-joint interfaces (roughened with a high-pressure water jet), and keyed-wet-joint interfaces were tested under the classical push-off test setup. The influences of steel fiber properties, keyed-joint shapes, and confining stress on the shear strength of the UHPC specimens are discussed. A high-precision equation for predicting the shear capacity of the UHPC specimens with monolithic interfaces, flat-wet-joint interfaces, and keyed-wet-joint interfaces is proposed and verified by experimental results. The test results indicate that steel fibers had a significantly positive effect on improving the shear strength of the UHPC specimens. For the flat-wet-joint specimens, the shear strength increased approximately linearly as the fiber content increased. Using long and hooked-end fibers improved its shear strength. For the keyed-wet-joint specimens, the shear strength improved almost linearly with confining stress, whereas the keyed-joint shape had little influence. The strength reduction factor (the ratio of the ultimate shear strength of the flat-wet-joint interface to that of the monolithic interface) increased with the fiber volume fraction. A relationship between the strength reduction factor and the fiber characteristic parameter is proposed.

When compared to conventional bitumen, thiophene bitumen produced in northern Iraq is abundant and inexpensive (on the order of $125\mathrm{USD}/\mathrm{t}\mathrm{on}$). This type of bitumen contains higher sulfur content in terms of the heterocyclic compound (not elemental sulfur); furthermore, long-term aging (LTA) effects are not considered in research on this type of bitumen for use in paving mixtures. In this research, the influence of LTA at $85\pm 3°\mathrm{C}$ for $120\pm 0.5\mathrm{h}$ on thiophene mix asphalt (TMA) properties in terms of stability, indirect tensile strength at 25 and 60°C, rigidity, resilient modulus, and tensile strength ratio were determined and compared with hot-mix asphalt (HMA) containing conventional bitumen. Under a 40-kN dual load with a 105 mm wheel radius, pavement responses in terms of fatigue strain ($\epsilon {\mathrm{t}}^{\max }$), rutting strain ($\epsilon {\mathrm{c}}^{\max }$), and surface deflection ($\mathrm{\Delta }{\mathrm{z}}^{\max }$) were analyzed using multilayer elastic analysis software (BISAR). The test results of TMA showed slightly higher stability, indirect tensile strength, and resistance to moisture damage (higher durability) with a slightly lower resilient modulus than HMA. Generally, results showed that the performance of TMA at a mixing temperature of 130°C is considered similar to that of HMA under the effect of LTA. Furthermore, using thiophene bitumen can reduce the mixing temperature of paving mixes above about 20°C in a manner comparable to HMA. In addition, the results also indicated that LTA-TMA showed 10% higher fatigue life than LTA-HMA. In addition, it was found that the granular base layer in the LTA-TMA pavement system can be reduced by 55%.

Traditional chemical stabilizers have been widely used for decades in order to enhance the strength and compressibility of soil. However, such stabilizers have been observed to create severe problems related to soil characteristics, groundwater quality, and also make the soil excessively brittle in nature. In the present study, lignosulfonate (a by-product from the timber industry) has been used to stabilize high plasticity clay and its influence on stress-strain behavior and unconfined compressive strength was investigated at different dosages of lignosulfonate and curing periods. From the test results, a logarithmic model was developed to predict the time-dependent strength behavior of lignosulfonate-treated high plasticity clay. In addition, the rate of strength development models were also proposed as a function of the lignosulfonate–to–dry soil mass ratio and time in order to illustrate the accumulation of strength gain during the different curing stages. The regression coefficients were determined from the proposed models and their correlation with the different parameters has been explained.