Journal of Materials in Civil Engineering

In this paper, the mechanical properties and size effects, which are important factors to be considered in the determination of strength, were assessed for a transparent material made from fused silica. This material could be a suitable substitute for brittle rocks or concrete. Laboratory tests on the strength and deformation properties of the transparent material were performed through uniaxial compression tests and Brazilian tensile tests. To study the size effect, cylindrical specimens for uniaxial compressive tests were prepared with diameters of 40, 45, and 50 mm and a height-to-diameter ($H/D$) ratio of 2.0. The specimens for Brazilian tensile tests were made into cylindrical discs with diameters of 40, 50, and 100 mm and $H/D$ ratios of 0.3, 0.5, and 1.0, respectively. The stress-strain relationship of the transparent material was found to be similar to that of brittle rocks, for which the elastic modulus increased with the increasing diameter for uniaxial compression tests. The uniaxial compression strength (UCS) and Brazilian tensile strength (BTS) of the specimens ranged between 63.64 and 109.70 MPa and between 2.48 and 7.4 MPa, respectively. These results are approximately $44.80\%-74.20\%$ and $30.20\%-36.15\%$ of those of granite. The UCS of the specimens increases with an increasing diameter. However, the BTS decreases as the specimen diameter and $H/D$ ratio increase.

In order to avoid certain construction difficulties in a traditional steel reinforced concrete (SRC) structure, like the interference between reinforcing steel and rebars or poor concrete pouring quality, steel–steel fiber–reinforced concrete (SSFRC) was proposed by removing the steel rebars from SRC and incorporating steel fibers. According to a standard push-out test of 36 specimens, this paper studies the bearing and damage mechanism in the bond interface between steel and steel fiber–reinforced concrete (SFRC). The results show that splitting cracks usually elongate from the concrete surface to the interface while bonding cracks elongate from the tips of a steel flange toward the concrete surface in the 45° diagonal direction. The external loading is transferred to the bond interface through steel near the free end, forming the compression stress and bond shear stress, and then, those stresses at the interface are transferred to the bottom SFRC surface at the loading end through an inclined compression band inside the SFRC. The SFRC blocks separated by cracks achieved stress balance under the bearing stress from steel at the interface and the clamping stress from nearby SFRC blocks along the bonding cracks. The SFRC cover mainly takes the bending effect from the compression stress when the thickness of the concrete cover ranges from 19.5 to 40 mm in this paper, but it takes the shear effect when the thickness of the concrete cover is larger than 40 mm. It is worth noting that the flexural strength of the concrete with a steel fiber ratio (${\rho }_{\mathrm{sf}}$) of 3% is not significantly improved, but the ultimate bond strength is increased by 17.63% compared with that of ${\rho }_{\mathrm{sf}}=2\%$. In addition, the calculation formulas of the ultimate bond strength, including the chemical bond stress, mechanical interlocking stress, and frictional stress, are proposed.

A two-dimensional finite-element simulation consumes less computational resources and has higher efficiency than a three-dimensional simulation. However, the existence of great differences between different slice images makes it difficult to represent the meso-structure of the whole specimen by a single or small number of images, while aggregate content and particle distribution have a significant impact on the results of two-dimensional finite-element simulations. To obtain accurate calculation results, it is necessary to solve a large number of two-dimensional models to suppress the errors by calculating the average value of the results. In this paper, based on a large number of slice images obtained by X-ray computed tomography (CT) scanning technology, two-dimensional finite-element models for indirect tensile test simulations were established while considering the meso-structure of asphalt mixtures. The relationship between the simulation results and the aggregate content was analyzed via an image processing method, and an aggregate content indicator was proposed and applied in the image selection process. According to the results, the use of the aggregate content indicator for the image selection process can greatly reduce the number of finite-element models and improve the calculation efficiency on the premise of ensuring the accuracy of the simulation results.

The high rate of energy consumption in the building sector has led designers toward construction methods that consume less energy during construction through serviceability. One of these methods is rammed-earth (RE) structures due to the availability of its materials, ease of preparation, and considerable decrease in energy consumption and environmentally destructive consequences. Improving the thermal characteristics besides the mechanical parameters of RE structures develops the application of RE structures. In the current study, the dynamic thermal parameters of RE wall specimens were experimentally measured under simulated conditions and compared to those of masonry walls. Thereby, a hygrothermal chamber was designed and made, and Fourier’s law was used to determine the thermal conductivity of these materials. Moreover, the effect of the acrylic coating was investigated for increasing thermal mass and decreasing energy loss from the structural elements. The results illustrate the proper thermal performance of stabilized rammed-earth in comparison to the masonry materials besides the positive effects of acrylic coating, which leads to satisfactory thermal comfort limits based on the ASHRAE 55 standard.

This study investigates the performance of two cementitious systems exposed to sodium chloride solution and thermal cycling. The two systems consisting of an ordinary portland cement (OPC) and a calcium aluminate cement (CAC). Several experimental techniques were conducted to evaluate the performance of OPC and CAC pastes exposed to different concentrations of sodium chloride (NaCl) solution and thermal cycling. X-ray powder diffraction was used to study the hydration products. Low-temperature differential scanning calorimetry was used to detect phase changes and study potential chemical interactions between pastes and NaCl solutions. A longitudinal guarded comparative calorimeter equipped with acoustic emission was used to detect phase changes and damage development in pastes saturated with NaCl solutions during thermal cycling. Unlike OPC pastes that can chemically interact with NaCl solutions to form a destructive chemical phase change at temperatures range between $-5°\mathrm{C}$ and 8°C, CAC pastes showed no chemical interactions with NaCl solutions, mainly due to possessing different chemistry than the OPC. As a result, no damage associated with the chemical phase change was observed in CAC pastes, indicating that the CAC is more chemically resistant to NaCl damage than OPC.

Mechanical properties of pervious concrete (PC) are highly influenced by the applied compaction; however, the required level of compaction to achieve the desired density and strength in the field is currently unknown. In some cases, compaction is established empirically on costly test panels. In this study, the relationship between the applied compaction force and the hardened porosity ($Ø$) and compressive strength ($f_c$) was investigated. Three PC mix proportions with varying paste contents were compacted in the laboratory using a lightweight deflectometer (LWD) at four different compaction levels. Porosity and 7-day $f_c$ testing were carried out on cylinders cast with each compaction level. In general, the first 15 LWD drops influenced $Ø$ and $f_c$ significantly, while the effect of compaction beyond that level was less significant. The applied compaction force recorded by the LWD was used to obtain the required properties of a rotary roller-screed to apply an equivalent compaction force in the field. Then, regression-based models were developed to estimate the 7-day $Ø$ and $f_c$ of PC based on the applied compaction force and the paste content. The developed models provide a practical solution to compute the required compaction force in the field to achieve the desired PC mechanical properties.

The bond between a deformed rebar and concrete is determined in pullout tests, using cylindrical concrete specimens with centrally embedded rebars, having a predetermined number of bonded ribs. In these experiments, the external measured parameters are the applied pullout load at the rebar end and the slip. This setup does not allow examination of the evolution of local damage in the concrete near the ribs, and the experimental research yields only the average bond stress versus slip relationship, which characterizes the bond property. The bond-slip curve is composed of an ascending branch along a short slip range and a following descending branch along the major slip range. Commonly, the different studies focus on the descending branch, although the maximum bond resistance is gradually developed along the ascending branch. The present study investigates in detail the ascending branch, which is commonly described by a smooth monotonic curve. There are no experimental data in the literature on the evolution of the resistance to pullout loading and the accompanying damage along the ascending branch. This study investigates the different stages of bond resistance development up to the maximum bond stress, and examines the local damage growth and its effect on the bond-slip curve smoothness. This investigation identifies that the ascending curve is not a smooth curve at all and it is composed of several segments with localized gradient changes. A complementary experimental study using an innovative experimental setup allows monitoring the local damage and strain fields in the concrete near the ribs during this part of the experiment. These tests provide new insight and complement the present study findings that the local gradient changes along the ascending curve result from the gradual formation and extension of interior damage with an accumulating effect during loading.

The California Department of Transportation has proposed to add a low amount of crumb-rubber modifier into dense-graded asphalt mixes, in addition to current policies of using gap- and open-graded mixes with a high content of rubber (around 20% by weight of binder) as the surface layers. The objectives are to reduce landfill disposal of scrap tires and to obtain equal or better performance compared to current dense-graded mixes containing unmodified binders. This paper investigated a new type of rubberized dense-graded mix containing 5% and 10% of the crumb-rubber modifier. The rubberized binder and the unmodified binder were compared at the same performance grade to meet the specific climate requirement. Their corresponding mixes met the Superpave volumetric design requirements. The laboratory experiment evaluated the rubberized mix and the conventional mix in terms of fatigue and fracture properties using a flexural bending fatigue test and semicircular bending test, respectively. A long-term oven-aging protocol and the uniaxial thermal stress and strain testing were used to evaluate the mix resistance to low-temperature cracking. Those laboratory test results indicated that the rubberized dense-graded mix had an extended fatigue life, higher fracture resistance, and better thermal cracking resistance than the standard dense-graded mix. Mechanistic-empirical (ME) design using the California ME design software simulated the performance of these mixes in various pavement structures and climate/traffic conditions to assess the interactions of stiffness and strain-controlled fatigue property for those mixes. The simulation results revealed that the new rubberized dense-graded mix mostly provided the same or better field performance as the conventional mix. The ME design analysis should be performed to optimize the application of those mixes in a case by case scenario.

In this laboratory study, the corrosion behavior of ASTM A1008 CS Type B carbon steel (C1008), ASTM A48 Class 35 gray cast iron (GCCL35), and ASTM A536 65-45-12 ductile cast iron [Ductile(65-45-12)] was examined in a simulated soil solution in the presence and absence of beetroot juice (beet juice), a bioderived additive. Two types of deicers, including 23% NaCl and 30% ${\mathrm{MgCl}}_2$ at different dilution ratios (1:30 and 1:90), were included as the test media to simulate the practical cases of buried pipes adjacent to roadways. The corrosion behavior of the metallic samples was examined by the measurements of open circuit potential and linear polarization resistance. In addition, electrochemical impedance spectroscopy was used to study the corrosion product layer. Surface analysis of the samples was carried out using energy dispersive X-ray spectroscopy and scanning electron microscopy methods. The results showed that beet juice had corrosion inhibitory properties in diluted 23% NaCl at both dilution ratios. However, in the case of diluted 30% ${\mathrm{MgCl}}_2$ solution, corrosion inhibition was limited to a dilution ratio of 1:30, which shows a more pronounced effect of dilution on the corrosion inhibition in 30% ${\mathrm{MgCl}}_2$ compared to 23% NaCl. The protection mechanism mainly involved blocking the anodic active sites by an organic passive layer. C1008 samples showed the lowest corrosion rate in the presence and absence of beet juice in NaCl and ${\mathrm{MgCl}}_2$ solutions. A more protective layer formed on the samples in NaCl solution compared to ${\mathrm{MgCl}}_2$, which may be due to the effect of ionic strength on the solubility.

All-coral aggregate seawater concrete and fiber-reinforced polymer (FRP) can overcome the shortcomings of conventional steel and concrete. This paper evaluates the bonding performance of different kinds of FRP bars and rebar with all-coral aggregate seawater concrete by using pullout tests. The results showed that specimens with plain round bars, deformed carbon fiber–reinforced polymer (CFRP) bars, and rebar mainly experienced pullout failure, while specimens with deformed basalt fiber–reinforced polymer (BFRP) bars and glass fiber–reinforced polymer (GFRP) bars experienced splitting failure. Different rib heights, rib spacings, and rib inclination angles caused different failure modes. The effects of fiber type, surface condition, failure mode, and concrete type on the bond behavior were analyzed. It was found that, owing to a difference in surface roughness, the ultimate load of plain round CFRP bars with coral concrete was weaker than those of plain round GFRP bars and BFRP bars. The ultimate load of plain round BFRP bars with coral concrete was more than five times that of ordinary concrete with the same designed cube compressive strength, mainly because coral reef sand had a large water absorption rate and the actual $\mathrm{water}/\mathrm{cement}$ ratio was relatively low, which led to an increased cement mortar strength. When the concrete strength was high, adhering sand to the surface of the FRP bars resulted in a small increase in the ultimate load. The ultimate load of ribbed steel bars with coral concrete was similar to that of deformed BFRP bars with coral concrete, but the bond failure mechanism was different. Compared with the influence of the type of FRP bar on the bonding performance, the influence of the rib parameters was greater.

It is crucial to accurately determine the coefficients of the modified Paris’ law to accurately characterize the fracture properties of an asphalt mixture. However, the current methods reported in the literature are associated with two major deficiencies: (1) application of incompatible energy balance equations, and (2) abandonment of the relationship between the dissipated pseudostrain energy (DPSE) and the damage density. This study, which addressed these deficiencies, developed an improved method to determine fracture parameters of asphalt mixtures, including the coefficients of the modified Paris’ law and the damage density. Two controlled-strain repeated direct tension (RDT) tests were performed in sequence on four types of asphalt mixtures to determine the properties of the asphalt mixture specimens in the linear viscoelastic stage and the destructive stage, respectively. The pseudostrain and the apparent DPSE were calculated for each specimen in every load cycle in the second RDT test. A fitting model was established for the apparent DPSE versus the number of load cycles for each specimen. This fitting model was incorporated into the modified Paris’ law to derive the formulation of the coefficients of the modified Paris’ law and the damage density. According to the DPSE balance equation, the model for the apparent stress amplitude was established based on the formulation of the apparent DPSE and the damage density. Mathematical techniques were applied to seek the most appropriate solutions for the model parameters, which proved to be perfectly reasonable and accurate enough to predict the values of the apparent stress amplitude, especially after 20 load cycles. With the determined model parameters, the coefficients of the modified Paris’ law were determined for every specimen, and the models of the damage density were finalized for all specimens.

In this study, a nano-silica (5% to 50%) water-based solution and silane/nano-clay (5% to 50%) composite were used as superficial treatments for concrete. The coatings were applied on concretes with different water-to-binder ratios (0.35 to 0.6). The transport properties of treated concrete were evaluated by the rapid chloride penetrability test and absorption and desorption percentages. Moreover, the treated concrete was subjected to severe durability exposures: physical salt attack and salt-frost scaling. Deterioration of the concrete surface was visually assessed and quantified by mass loss; in addition, mineralogical, thermal, and microscopy analyses were performed on concrete specimens to elucidate the mechanisms of enhancement imparted by surface treatments. The results showed that increasing the concentration of nano-silica in the colloid led to improved performance of concrete, with 50% dosage leading to the least penetration depth, absorption and desorption percentages, and mass loss, whereas for the silane/nano-clay composite, a low percentage (5%) of nano-clay was adequate to mitigate the damage of concrete under aggravated conditions.

The effect of steel reinforcement on the distribution of alkali-silica reaction (ASR) damage in concrete blocks is studied by leveraging acoustic emission sensing with a data-driven approach. The innovation lies in deriving damage contours caused by ASR based on a minimal sensor array. Through this approach, damage progression can be traced in time and event distribution can be visualized. A gap in the current literature, namely evaluating ASR progress in concrete structures with different internal restraint using acoustic emission (AE), is addressed. Unsupervised pattern recognition is utilized to study the effect of the temporal damage condition. In the confined specimen, the distribution of AE events in the midwidth region of the specimen is concentrated and close to the normal distribution. The surface cracks are mostly oriented along the specimen length and in the midwidth region. However, in the unconfined specimen, the distribution of AE events is more uniform, and cracks are randomly distributed.

The point-load test method (PLTM) commonly used in the geotechnical area is shown in this paper to estimate the compressive strength of in situ masonry mortar. A specially developed portable PLTM instrument was used for mortar sheet testing. The mortar sheets were removed from horizontal masonry joints by drilling cores out, with little preparatory work required. The test mortar sheets were subjected to pressure from two opposing cone heads, and the peak load at the failure of the mortar sheet was recorded. The effect of specimen size and mortar thickness on the point-load strength was examined. A suitable size of mortar sheet was selected for the experiment. The thickness correction method was used to improve the accuracy of the empirical formula. Scattering characteristics were investigated to check the reliability and repeatability of the PLTM results. A strong relationship was noted between the point-load strength of the mortar sheet and cube compressive strength, ranging from M2.5 to M15.0. Contrast tests with other available test methods verified that the PLTM offers an alternative to the masonry mortar compressive test and has high accuracy, requires little preparation, and involves reproducible and quick operation following specimen extraction from joints.

The objective of this study is to propose reliable models to assess the unrestrained and restrained shrinkage strains of lightweight concrete prepared using bottom ash aggregates and air foam (LWC-BF), on the basis of the nonlinear regression analysis using test data measured in the present specimens. Ten mixtures for LWC-BF were prepared with air foam volume fraction varying between 0% and 40% and water-to-binder ratios ($W/B$) at 25% and 30%. To grant sustainability with LWC-BF, the binder was composed of 30% ordinary portland cement, 50% ground-granulated blast-furnace slag, and 30% fly ash. All the specimens under the plastic shrinkage condition exhibited no crack development. The equivalent porosity ($P_{eq}$) and $W/B$ could be regarded as a critical factor to assess the unrestrained (${\epsilon }_{fsh}$) and restrained (${\epsilon }_{rsh}$) shrinkage strains of LWC-BF. The net time to cracking and average stress rate at cracking recorded in the ring specimens under restrained condition ranged between 1.33 and 1.75 days and 1.12 and $1.31\mathrm{MPa}/\mathrm{day}$, respectively. Thus, the cracking potential of LWC-BF attributable to shrinkage was classified as high level. Based on these analyses and the concept of time function, ${\epsilon }_{fsh}$ and ${\epsilon }_{rsh}$ can be simply formulated as functions of $P_{eq}$ and $W/B$. The statistic comparisons revealed that the proposed models predict accurately the shrinkage behavior of LWC-BF. The mean and standard deviation of normalized root-mean-square error values determined from the measured and predicted shrinkage curves are 0.083 and 0.014, respectively, for unrestrained specimens, and 0.083 and 0.005, respectively, for restrained specimens. Meanwhile, code models result in unreasonable predictions for unrestrained shrinkage curves.

One of the most important factors affecting the occurrence of thermal cracking is asphalt binder aging. Many studies have been conducted to identify and prevent this distress. However, the majority of these studies used the results of mechanical tests to evaluate the thermal cracking potential of an asphalt mixture, and little attention has been paid to the main properties of the materials which contribute to the occurrence of thermal cracking. This study investigated the effect of aging on thermal cracking of asphalt mixtures by mechanical and surface free energy (SFE) methods based on the main properties of the material. Eight combinations of asphalt mixtures were prepared using granite and limestone aggregates and two types of asphalt binder, PG 64-16 and PG 58-22. The thermal cracking of asphalt mixtures was evaluated by conducting a mechanical test, i.e., the semicircular bending (SCB) test, at three temperatures; and thermodynamic tests, i.e., sessile drop (SD) and universal sorption device (USD) tests, based on SFE methods. The results of the SCB test indicated that the values of SCB parameters of maximum load, fracture energy, and fracture toughness were higher in the aged asphalt mixtures than in the control mixtures. In addition, the results revealed that aging increased the free energy of cohesion and decreased the free energy of adhesion. This means that, as a result of aging, the probability of thermal cracking decreases in the mastic, whereas the probability of thermal cracking increases due to the weak adhesion between asphalt binder and aggregate. The results of the statistical analysis demonstrated a strong correlation between the free energy of cohesion and adhesion and the parameters of maximum load, fracture energy, and fracture toughness at all three tested temperatures. The coefficients of the regression models presented in this study confirmed the close relationship between the mechanical results and the SFE, suggesting that the thermodynamic methods are effective for investigating low-temperature cracking in asphalt mixtures.

This paper investigates the influence of limestone powder (LS) fineness on the early-age properties of portland cement paste. Blended pastes with LS were prepared based on volumetric ratio and their fresh properties, chemical shrinkage, and hydration were measured. Fresh properties were evaluated by water demand for normal consistency, yield stress, plastic viscosity, and bleeding ratio. Chemical shrinkage was measured using the helium pycnometry method. Hydration products and the hydration process were analyzed by X-ray diffraction (XRD), thermogravimetry and differential scanning calorimetry (TG-DSC), and calorimetry tests. Results show that LS significantly affects the properties of portland cement and this effect greatly depends on its fineness. Specifically, LS coarser than cement decreases water demand, plastic viscosity, and yield stress, while finer ones have the opposite effects. Plastic viscosity is related to the particle density (particle number per $100{\mathrm{\mu m}}^3$ solids) and specific surface area of total powders. Bleeding resistance is improved for blended paste with finer LS. Chemical shrinkage results demonstrate that LS indeed increases chemical shrinkage per gram of cement because of promotion on cement hydration. But this influence on the volume change of total paste is mitigated because of the dilution effect. XRD patterns show that LS does not react with cement hydrates at 24 h and preliminarily indicates the promotion of LS on cement hydration. Calorimetry results further confirm that LS accelerates and amplifies cement hydration despite its fineness and this promotion is more significant when LS is finer. This promotion is also confirmed by hydration degrees calculated from both heat of hydration and nonevaporable water content.

Low-temperature cracking is the main distress in asphalt pavement in cold regions (such as the arctic and subarctic regions) as the climate in these areas is severe in winter. While soft asphalt binders (such as PG 52-34 and PG 52-28) are used in the cold regions, asphalt pavements can still exhibit premature cracking failures. One of the approaches to solve this issue is to modify binders using additives. However, it is not clear which additives can significantly improve the thermal cracking resistance of binders. Therefore, there is a need to find potential additives resulting in improved resistance to thermal cracking because of extreme low temperatures experienced in cold regions. In this study, five additives [nano ${\mathrm{TiO}}_2$, nano ${\mathrm{SiO}}_2$, styrene-butadiene-styrene (SBS), ground tire rubber (GTR), and corn oil-based softening agent (SA)] were applied at various dosages with two soft base binders (PG 52-28 and PG 64E-40). Performance properties of modified binders were evaluated using the dynamic shear rheometer (DSR), standard bending beam rheometer (BBR), and modified BBR. The testing results indicated that the combination of a 7% softening agent and 7.5% SBS exhibited the highest improvement in the resistance to thermal cracking. Meanwhile, this combination also resulted in two performance grade bumps at high temperatures. Based on the laboratory testing results, the combination of a softening agent and high SBS could be potential additives to create high-performance binders for cold regions.

Aeolian sand is a type of special soil with a loose structure, fine and uniform particles, and poor self-stabilization ability. These characteristics easily lead to sand dune movement and wind erosion in dry desert conditions. Therefore, reinforcement technology for aeolian sand is an important research topic. Microbially induced calcite precipitation (MICP) is a novel microbial soil-strengthening technique considered in this study with a focus on the effect of the reactant injection rate on the microbial solidification of aeolian sand. The aeolian sand was solidified using MICP with different injection rates of the cementing solution. The physical and mechanical properties as well as the microstructure of the solidified aeolian sand samples were analyzed. The experimental results show that using Sporosarcina pasteurii and the cementing solution (a mixture of urea and calcium chloride) can effectively solidify aeolian sand using the MICP technology. The engineering performance of the sand was effectively improved with an unconfined compressive strength that approached 14.01 MPa. The permeability coefficient of the solidified aeolian sand was significantly reduced, and the injection rate of the cementing solution significantly affected its uniformity. When the injection rate of the cementing solution was too low, most of the calcium carbonate was generated and accumulated at the top of the sand sample. Therefore, the upper part of the sample was relatively dense and strong, while the lower part had the opposite properties. When the injection rate of the cementing solution was too high, the roles of the upper and lower parts of the sample were reversed. When the injection rate of the cementing solution was $0.278{\mathrm{mol}\mathrm{L}}^{-1}{\mathrm{h}}^{-1}$, the solidified aeolian sand sample was relatively uniform and had a moderate unconfined compressive strength of $4.58–5.03\mathrm{MPa}$. The uniform and high strength of the solidified aeolian sand was obtained by controlling the reactant injection rate. The optical microscope and SEM analyses indicated that the calcium carbonate crystals were rhombic hexahedral with sizes of approximately $5–10\mathrm{\mu m}$. The calcium carbonate crystals were generated from the MICP in the solidified aeolian sand, which cemented the sand particles together, filled the pores between particles, increased the density and strength of the sand, and reduced its permeability coefficient.

Plastic concrete is used widely in the construction of cut-off walls. These structures might be exposed to coupled effects of dynamic load along with confining pressure. Therefore, careful study of the impacts of these combined stress conditions is one of the primary issues to be considered in analysis and design. Although there is a large number of experiments on the mechanical properties of plastic concrete in static loading and triaxial condition, none have studied the behavior of this material in dynamic state loading. Therefore, a series of unconfined and triaxial compression tests has been carried out under different confining pressures and strain rates to experimentally investigate the behavior of this material under combined stress conditions. The test results indicate that increasing the loading rate in the triaxial tests causes enhancement of the strength and friction angle of plastic concrete. This phenomenon is more evident in higher confining pressures.

The degradation of ancient buildings has attracted much attention, and plane lime mortar cannot meet the requirements of utilization in special environmental loads or buildings. In order to improve the hydraulic properties and freeze-thaw resistance of lime mortars, both carboxymethyl cellulose (CMC) and metakaolin were added to plane lime mortars in this study. The performance of lime mortars with different additives was evaluated. The experimental results showed that the combined effect of CMC and metakaolin on compressive strength of lime mortars could be divided into three stages according to the curing age. The early compressive strength of blended mortars is improved. With increasing curing ages, the compressive strength varied in accordance with the phase transition of hydration and carbonation products. Furthermore, blended mortar with a long curing age exhibits better freeze-thaw resistance. These results suggest that the combined action of metakaolin and CMC played a significant role in the properties of lime mortars, which is generally beneficial for restoration applications, especially for ancient buildings in cold regions.

Corrosion of reinforcement in concrete is a billion dollar problem spread across the globe. Early detection of corrosion-induced damage preempts weakening of the structure and timely rehabilitation extends its life. Therefore, there is a need in the industry for a reliable nondestructive diagnostic tool for detection of corrosion-induced damage in concrete structures. This paper presents two ultrasonic wave–based imaging techniques for monitoring changes in the concrete subsurface during various stages of rebar corrosion. An accelerated corrosion setup was developed to induce corrosion in a rebar embedded in a concrete slab specimen. A pitch catch mode of ultrasonic scanning was performed on a set of grid points on the test specimen using compressional and Rayleigh wave transducer arrangements. In the first approach, the traditional synthetic aperture focusing technique (SAFT) was used to produce images in the horizontal and vertical planes using the compressional wave velocity information and incorporating corrections related to limited directivity of the transducers. In the second approach, the planar SAFT algorithm was used for detection of vertical corrosion cracks, using the scattered Rayleigh wave field. The study shows that with progress of corrosion, the rebar image disappears from the compressional wave–based SAFT images while the corrosion-induced surface breaking cracks appear in the planar SAFT images. The combination of these two approaches has potential to be a powerful qualitative nondestructive technique for identification and localization of damage leading to requisite repair and maintenance activities.

Mechanical foaming of bitumen is a popular technique employed to reduce the viscosity of binder for ensuring coating of aggregates at lower temperature. The potential of this technique is being utilized widely for producing sustainable reclaimed-asphalt pavement (RAP) inclusive mixtures, but usage of recycled concrete-aggregates (RCA) in foamed technology is very scanty. The present study is the first of its kind attempting to investigate the optimum proportion of hydrophobic RAP aggregates and hydrophilic RCA (separately as well as combined) for the preparations of foam-mix asphalt (FMA). It was observed that incorporation of RCA in FMA affects the quality of mixes but RCA inclusive FMA was found to qualify the stipulated specifications for pavement applications. From the present study, it is found that up to 20% RCA and 40% RAP proportions individually could be utilized for the preparation of foam mixes. Also, it is interesting to note that delayed hydration of residual cement grains could enhance the performance of FMA. Furthermore, 30% RCA coupling with 10% RAP was found to exhibit acceptable performance. The present study suggests that 0.1% fiber reinforcement could enhance the performance of the foam mixes considerably.

Recent advancements in material sciences have led to the development of new fiber-reinforced polymer (FRP) systems that, unlike traditional FRPs, are specifically tailored to have large fracture strains that are advantageous for external strengthening applications. One such system is polyethylene terephthalate (PET) FRP, which can attain a nominal fracture strain of 7%. In this work, the mechanical properties of PET laminates were investigated when exposed to temperatures ranging from 25°C to 125°C. Test results indicate that PET-FRP exhibits a nonlinear stress-strain response that could be divided into three phases with three moduli ($E_1$, $E_2$, and $E_3$) and corresponding three tensile strengths (${\sigma }_1$, ${\sigma }_2$, and ${\sigma }_3$). The results also demonstrate how the aforementioned mechanical properties degrade around the glass transition temperature of the epoxy from so ft ening in the matrix. Interestingly, test results indicate that PETs exhibit an increase in rupture strain (from 9% to 14%) when the test temperature increases from 25°C to 125°C. To properly document these observations into design tools, temperature-dependent material models for moduli and tensile strengths are derived.

Concrete structures are economical and typically durable when exposed to a variety of environmental conditions. However, carbonation results in a reduction of the durability of reinforced concrete members because it damages the passive film surrounding the reinforcement, which accelerates corrosion processes and may ultimately lead to premature failure of the members. Predicting service life is complex because it depends strongly on changes in materials and environmental conditions. Existing carbonation models predict the service life based on deterministic theories. In this study, deterministic and probabilistic methods are applied to study concrete carbonation in the presence of repair materials using the maintenance periods and repair cost according to the coefficient of variation (COV) of the carbonation depth of each repair material. Water-based paint, organic alkaline inhibitor, inhibiting surface coating, and corrosion-inhibiting mortar (IM) were used as repair materials. An accelerated carbonation experiment using 20% ${\mathrm{CO}}_2$ was performed for 5 days, and then the repair materials were applied on the concrete surface. Then the samples were put back in the carbonation chamber and carbonation depth was measured after 7, 14, and 28 days. Based on the COV value, the carbonation depth and maintenance periods were predicted. These were used as parameters for the probabilistic life-cycle cost (LCC) model. Results showed that carbonation inhibition was best when the repair was done using IM. Cost results obtained from deterministic and probabilistic models were compared. When the probabilistic model is applied, the repair cost is evaluated as a curve, unlike with the deterministic model. The probabilistic model reduces the maximum cost by 50% compared to the deterministic model. As the COV decreased (indicating better quality concrete), the probabilistic model results approached those of the deterministic model evaluation.

A number of parameters can influence the fluidity of an ultrahigh-performance concrete (UHPC) mix and, hence, its viability for use in construction. These parameters include the carbon content of silica fume, high-range water reducer (HRWR) dosage, water-cement ($\mathrm{w}/\mathrm{c}$) ratio, and proportion of fine sands used in the mix. However, the relationship between those variables and their effect on the fresh and hardened properties of UHPC is not yet well understood. Using spread as a measure of fluidity, the effects of these variables on the compression strength, direct tensile strength, air voids, chloride ion penetration resistance, and freeze-thaw (F-T) resistance are experimentally investigated. The test results indicate that changing the ratio of the silica sands used can lead to an enhancement in the packing density and a corresponding substantial increase in compressive strength. Increasing the HRWR dose results in a mild reduction in the compressive strength of the mixture but does not adversely affect durability. However, increasing the dosage beyond a limit can lead to fiber segregation, which can adversely affect the mechanical properties. A response surface that ties the water-cement ratio and HRWR dosage to the compressive strength and spread is proposed. The response surface can be used as a design aid to properly design or optimize a UHPC mix.

In the system formed by bituminous crack sealant and the crack wall, the contact area of aggregate and sealant is maximum, and types and properties of aggregate have an obvious influence on the adhesion of the sealant. To quantitatively evaluate the adhesion of sealant to aggregate, based on the surface energy theory, the surface energy and its components of sealant and aggregate were determined and calculated using the sessile drop method. Then, the adhesion work of different types of sealants and aggregates was calculated. The correlation of adhesion work was verified by the improved boiling method test and scanning electron microscope (SEM) test. Results show that surface energy of the aggregate is obviously higher than that of the sealant. The relationship of surface energy of raw materials is $\mathrm{granite}>\mathrm{diabase}>\mathrm{basalt}>\mathrm{Sealant}$ A (type JG-10; Beijing Jiageweiye Company) > Sealant C (type II; American Crafco Company) > Sealant B (type JSD; JSD Corporation of Japan). The relationship of adhesion work of different sealants with the same aggregate is Sealant A > Sealant C > Sealant B, indicating that the adhesion of Sealant A to aggregate is better than that of Sealant B and Sealant C. Results of the improved boiling method test show that the coefficient of linear correlation between the mass loss rate of sealant and the adhesion work is as high as 0.9308, indicating that there is a good linear relationship between them. The SEM results show that the adhesion work is consistent with the actual adhesion state of the interface, which shows that the adhesion work index can be used to characterize the adhesion of sealant to aggregate.

The use of natural fibers such as oil palm broom fibers (OPBF) for reinforcing cementitious composites, although reported to be beneficial from economic and environmental standpoints, has generated durability concerns that have caused investigations into possible fiber treatments. In this study, three types of treatments were carried out on OPBF. These include alkalization, silanization, and hot-water treatments. For alkalization, OPBF was treated with solutions of 2%, 4%, 6%, and 10% sodium hydroxide each for 30, 60, 120, 240, 480, 1,440, and 2,880 min. For silanization, OPBF were treated with solutions of 1% and 3% triethoxyvinylsilane each for 60, 120, 240, 480, 1,440, and 2,880 min. For hot-water treatment, OPBF were treated with water at 100°C for 15, 30, 60, and 120 min. The effects of treatments on the fibers were analyzed through tensile strength, X-ray diffraction, electron microscopy, and water absorption tests. The results indicate improvements in tensile strength and modulus of elasticity of 60% and 65%, respectively. Although the average reduction in water absorption of 4% was recorded for silanization, increases of 40% and 9% were recorded for alkalization and hot-water treatment, respectively. The changes in the physical and mechanical properties of treated OPBF are attributed to the elimination of impurities, lignin, and wax, a reduction in the microfibrillar angle, alteration of fiber surface, and improvement in fiber crystallinity. The reported pretreatments could enhance the durability of composites incorporating OPBF as a reinforcement.

Hot-mix asphalt (HMA) is a multicomponent mixture composed of asphalt, coarse and fine aggregates, fillers, and other necessary additives. The bitumen–aggregate adhesion and performance of HMA are mainly dependent on such factors as mixing temperature and time, raw material characteristics, and mixing sequence of raw materials. The latter factor is the least reported in the literature. In recent years, surface energy theory has significantly been employed as the method for the prediction of bitumen–aggregate adhesion and mixture performance. This paper provides the optimization of the HMA mixing process based on the surface energy theory. A quantitative index called the total adhesion work is proposed from the perspective of energy change, which can be used to determine the two-step adding proportion of fine aggregate. Assuming that asphalt is in the hot-melt state rather than solid-state during the actual mixing process, a method for testing the surface energy components of hot-melt asphalt is proposed. Based on the total adhesion work, several different mixing processes are used to produce HMA, and the optimal one was identified experimentally. It is shown that the asphalt mixture performance can be improved by optimizing the adding sequence and proportion of the fine aggregate. The enhancement of HMA high-temperature performance and water stability is the most pronounced when the total adhesion work ratio of the two-step addition procedure approaches unity.

Although the multiple stress creep recovery (MSCR) test has shown its superiority in predicting rutting resistance of asphalt binders, concerns have been raised regarding the testing protocol and procedures. To evaluate the rutting resistance and investigate the suitability of the standard MSCR test method for Alaskan binders, nine typical Alaskan asphalt binders from three different suppliers were collected from paving projects and tested using MSCR tests with four different testing protocols and procedures. The results indicated that the modified binders had better rutting resistance than the neat binder regardless of performance grade (PG). The nonlinear stress limits of most modified binders were all found to be less than 3.2 kPa, which indicated that the stress level of 3.2 kPa included in current specifications could identify their nonlinear behavior. A higher stress level was recommended for identifying the nonlinearity of Binder 3 (PG 64-40 from Supplier A). The recovery time and the number of load cycles had significant effects on the nonrecoverable creep compliance (Jnr) and percent recovery ($R$) values of polymer-modified binders. Based on the testing results, it was recommended that at least 30 load cycles be included at each stress level and that the strain data from the last five cycles be used to calculate the Jnr and $R$ values. The Jnr-diff included in current one current standard was found unwarranted to evaluate the stress sensitivity of the Alaskan polymer-modified binders used in this study.

Reducing volume expansion of steel slag is a key problem for steel slag to be applied in asphalt concrete pavement. It not only avoids environmental damage caused by natural stone mining but also provides a cheap and excellent alternative to traditional aggregates. In this study, a surface hydrophobic waterproof structure (SHWS) was proposed for immersion pretreatment of the surface of steel slag particles. The main properties of the modified steel slag were analyzed and compared with those of unmodified steel slag; the properties analyzed included hydrophobicity, water absorption, adhesion strength to asphalt, and volume expansion. The water stability of the modified asphalt mixtures was also studied by considering volume stability, immersion Marshall test, and freeze–thaw split test. The results showed that the surface water absorption of the modified steel slag was at least 23.6% lower than that of unmodified steel slag due to the hydrophobicity of the SHWS. The volume expansion inhibition effect of the SHWS increased with decreasing particle size of the modified steel slag. For steel slag with particle sizes between 4.75 and 9.5 mm, the final volume expansion rate of the modified steel slag was 46% lower than that of unmodified steel slag. Water stability of the modified steel slag asphalt mixtures was also improved due to the alkaline rough hydrophobic steel slag surface and high adhesion strength to asphalt. The proposed immersion pretreatment is expected to provide an efficient alternative solution for improving the application of steel slag in asphalt pavement.

Most tabia sites exhibit accelerated decay rates caused by weathering. Weathering damage generally proceeds from the surface to the interior; thus, protecting the surface of tabia sites is an effective method to resist weathering. In this study, the microbially induced carbonate precipitation (MICP) technique is used to form an anti-erosion layer on the surface of tabia. Next, the applicability of MICP for tabia surface erosion control is examined in the laboratory via the static contact angle test, capillary water absorption test, Karsten tube test, durability test, acid resistance test, water vapor permeability ($WVP$) test, and color change test. Moreover, the effect of the concentration of bacteria and cementation reagent on the surface erosion control is analyzed. The test results show that MICP can significantly improve the water resistance of a soil sample by changing the microstructure of the surface. Higher concentrations of bacteria and cementation reagent allow the sediment layer to provide better protection; however, this effect is not linear. The concentration threshold reduces the positive effect of the bacterial concentration on the water resistance of the soil surface. The MICP protection layer offers favorable durability with little negative impact on the air permeability and color of the sample. The use of an MICP protection layer can effectively relieve the surface erosion of earthen sites.

In this study, six different blends including a base binder, polymer modified binder [5% acrylonitrile styrene acrylate (ASA) by the weight of binder], ASA–nano calcium, and ASA–nano copper at concentrations of 3% and 5% by weight were characterized using a dynamic shear rheometer (DSR). The range of temperatures was $46°\mathrm{C}–82°\mathrm{C}$, while the frequencies were from 1 to $100\mathrm{rad}$/s. The prediction of complex modulus ($G^{*}$) from physical and rheological properties of binders and the mechanical test conditions were performed using an artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS). The coefficient of determination ($R^2$) and root-mean-squared error (RMSE) were used as the performance indicator metrics in the evaluation of the performance of analytical models. The results of this study show improvement in the rheological behavior of the modified asphalt binder. Further, ANN and ANFIS models for predicting the outcomes of the DSR test results have been shown to provide reliable models both with training and testing data sets. The $R^2$ values of 0.996 and 0.920 and RMSE values of 0.008295 and 0.006755 were obtained with the testing data sets for the ANN and ANFIS prediction models, respectively. Model results showed that both ANN and ANFIS models were able to predict $G^{*}$ with high accuracy, with ANN being the more efficient analytical model in terms of performance.

Modifying oil behavior with the help of additives is a superficial and deep soil improvement method. The considerable geological distribution of different types of pozzolanic materials, especially of zeolite in Iran, on the one hand, and the unique characteristics of these materials on the other, have caused this type of additive to be of interest to geotechnical engineers. In this study, in order to investigate the effect of zeolite on sandy clay soil and clayey sand soil, a set of tests including Atterberg limits, modified compaction, uniaxial compressive strength, and direct shear tests have been conducted. Further, scanning electron microscopy (SEM) and X-ray diffraction (XRD) have been performed to investigate the microstructure of stabilized and nonstabilized soil. The results indicated changes in Atterberg limits, internal friction angle, and maximum dry unit weight in response to alteration of the additive percentage. Further, changes in the zeolite percentage and curing time led to altered uniaxial strength of soil. With the increase in the percentage of zeolite and lengthening the curing time, the uniaxial compressive strength of samples increased, with the uniaxial compressive strength in clayey sand and sandy clay soil growing by 4 and 2.5 times the initial strength of soil, respectively. Thus, the effect of these additives is more considerable on clayey sand soil. In addition, the strength parameters of soil (including cohesion and internal friction angle) improved in response to adding zeolite. The maximum increase in the internal friction angle and cohesion was related to zeolite 25%. The results of XRD and SEM analyses indicated that stabilization with zeolite caused occurrence of chemical reactions and production of cement products including calcium silicate hydrate (CSH) and calcium aluminate hydrate (CAH), which is one of the main reasons behind the increased soil strength.

The alkali-activation of high-volume fly ash (HVFA) produces a low-carbon sustainable cementitious binder with remarkable strength and chemical durability at room temperature. In this work, the influence of activator type (i.e., deionized water, NaOH, ${\mathrm{Na}}_2{\mathrm{SO}}_4$, ${\mathrm{Na}}_2{\mathrm{CO}}_3$ solutions), silica fume incorporation, and curing duration on the phase assemblage and strength and shrinkage developments of HVFA is studied. The results show that ${\mathrm{Na}}_2{\mathrm{SO}}_4$-activated HVFA shows the highest strength achievement, followed by ${\mathrm{Na}}_2{\mathrm{CO}}_3$, NaOH, and water. Alkali incorporation in HVFA considerably increases the shrinkage magnitude and is mainly attributed to the detrimental effect of alkalis on the viscoelasticity and stiffness of cementitious solids. The HVFA activated by the NaOH solution shows the largest shrinkage, followed by ${\mathrm{Na}}_2{\mathrm{CO}}_3$ and ${\mathrm{Na}}_2{\mathrm{SO}}_4$ solutions, despite comparable moisture loss. The curing duration does not significantly affect the shrinkage development of alkali-activated HVFA without silica fume. However, with silica fume incorporation, extending curing duration considerably reduces the shrinkage of alkali-activated HVFA. The phase and molecular analysis suggest that silica fume noticeably retards the reaction of HVFA systems but tends to increase the level of silica polymerization in gel products, regardless of activator type.

Although there are numerous experimental studies of the size effect on nominal splitting tensile strength of concrete materials being performed, research on effect of specific material parameters involving maximum aggregate size (MAS) and concrete strength grade (CSG) on the splitting tensile strength of concrete materials is relatively rare. This paper investigated the influence of MAS and CSG on macro splitting tensile behavior of concrete materials and the corresponding size effect from both experimental and numerical perspectives. Four groups of maximum aggregate sizes (10, 20, 30, and 40 mm) and three groups of concrete strength grades (C20, C40, and C60) were considered, and a total of 84 concrete cubic specimens with different side lengths (150–350 mm) were tested. A three-dimensional mesoscale numerical method was established and a total of 114 concrete cubic models (with side length up to 600 mm) with different MAS and CSGs were simulated. The results indicate that splitting tensile strength decreases with increasing side length and the downtrend of strength decreases as side length increases. The downtrend of strength in concrete specimens with smaller MAS was more obvious, and the increase in MAS can reduce the sensitivity to the size effect on the splitting tensile strength. Concrete specimens with higher strength grades had more obvious downtrends of strength than did specimens with lower strength grades. The influential mechanism of MAS and CSG on the macroscopic failure behavior and the corresponding size effect of concrete materials were analyzed preliminarily.

The dynamic compressive test of rubber cement mortar (RCM) under two different curing humidity levels (the relative humidity was 95% and 50%, respectively) was carried out by using a split Hopkinson pressure bar (SHPB) device, and the dynamic mechanics and damage evolution characteristics of RCM were studied. The results show that the impact resistance of cement mortar is obviously improved by adding rubber particles and is decreased by reducing the curing humidity. The stress-strain curve of the RCM has a transverse fluctuation in the top region, which reflects the excellent ductility and toughness of the RCM. Both dynamic peak stress and dynamic increase factor (DIF) have a linear positive correlation with strain rates, and the DIF is reduced due to the decrease in curing humidity. A damage analysis was carried out, and the reduction of curing humidity and the incorporation of rubber particles increased the damage variable $D$ and significantly changed the dynamic damage evolution process of the cement mortar. Finally, the blasting disturbance and the surrounding rock stability were analyzed along with the material properties and underground engineering issues. Therefore, this engineering application analysis demonstrated that the rubber cement-based materials have a prospective application.

The four-point beam (4PB) test is extensively used to characterize the fatigue behavior of asphalt concrete mixtures. But the inhomogeneity of the deformation in the beam is not given due consideration in traditional analyses of these tests. During bending, the strain in the beam varies both along the length and depth of the beam. Consequently, different parts of the beam would experience different levels of damage when subjected to repeated loading. The modulus obtained from traditional calculation procedures do not take into account this variation, and therefore, the calculated modulus is essentially an overall weighted modulus. In this study, a new methodology is proposed with which the evolution of local modulus and local phase angle with loading cycles can be determined. The methodology does not assume any specific constitutive relationship among the stress, strain, and extent of damage. It was developed by considering the modulus of the material to depend on only the amplitude of the applied strain and the number of cycles of load repetition. With this methodology, the evolution of local modulus at any particular strain level can be obtained, provided the 4PB tests are conducted at a sufficient number of strain levels. Based on the evolution of local modulus, a new fatigue failure criterion is proposed. The number of repetitions at which the local modulus reduces to zero is taken to be the point of failure. This fatigue life criterion is more meaningful than the old 50% reduction in stiffness criterion. The fatigue life obtained using this criterion is also comparable to that obtained using the new stiffness ratio criterion.

The current test method cannot predict the properties of a joint sealant accurately, and therefore this paper proposes a new test method to evaluate its adhesive property. Field investigation was conducted to examine the main forms of joint sealant failure and its actual working conditions. Our findings enabled us to develop a new test method for evaluating the adhesive properties of sealants. A testing procedure, a standard substrate, and optimal testing parameters were determined in the light of analyses of test results. We conducted differential scanning calorimetry (DSC) and X-ray photoelectron spectroscopy (XPS) tests to research the adhesive mechanism of the sealant. Results showed that adhesive failure is the main failure form, and it is caused mainly by horizontal joint expansion. Using peak load as the standard evaluation index, we noted that quartz substrate has the weakest bonding interface with joint sealants. The adhesive strength of sealants has a positive correlation with the isocyanate index and elongation rate, and a negative correlation with temperature. The optimal elongation rate was determined to be $100\mathrm{mm}/\mathrm{h}$, at which there is good repeatability and stability. Sealants with high isocyanate index can present two glass transition points and react more easily with ${\mathrm{SiO}}_2$, but may also result in a rougher surface that could reduce the chemical interaction between polyurethane and ${\mathrm{SiO}}_2$.

The durability of flexible pavements is affected by the presence of moisture, which leads to failure of bitumen-aggregate bonds. The failure of the bond has been explained by various mechanisms. The use of hydrated lime (HL) has been found to improve this bond and reduce moisture damage. However, a unique mechanism leading to the improvement in the bond requires further research and has motivated the introduction of nanotechnology in its determination. The present study is based on the use of synthesized NHL in varying percentages to modify bituminous binder. Atomic force microscopy (AFM) was carried out on the base and modified binders to evaluate bond strength and bond length of the modified bituminous binder, and unique observations were made. The peak force corresponding to bond strength is found to increase up to 10% with the addition of NHL, after which saturation is observed. The distance corresponding to this peak force, however, keeps on increasing with incremental usage of NHL. This observation was attributed to an increase in charge density due to addition of inorganic NHL.

This study demonstrates the use of novel zinc phosphate (ZnPh)-treated steel fibers in ultra-high-performance concrete (UHPC), replacing the commonly used steel fibers. The effects of ZnPh-treated steel fibers on tensile and flexural strengths of UHPC were investigated through flexural and direct tension tests. The results showed that first cracking strengths were reduced by 9.7% and 0.5% in the flexural and direct tension test specimens, respectively. The ultimate strengths were increased by 16.8% and 18% in the flexural and direct tension test specimens, respectively. Also, in the direct tension test, the ultimate strain at the ultimate strength was increased by 113.1%. scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) analyses revealed that a weaker interface exists between the ZnPh covering and the fiber. This interface resulted in reduction of first cracking strengths, whereas the ZnPh covering improved ultimate strengths due to an increase in friction between the fiber and matrix after the ZnPh peeled off.

This study presents an investigation of the cyclic freeze–thaw (F/T) effects on the dynamic and static splitting-tensile properties of plain cemented clay (clay mixed with 15% cement) and basalt fiber–reinforced (BFR) cemented clay (clay mixed with 1.5% basalt fiber and 15% cement). The effects were evaluated by focusing on the dynamic tensile strength, static tensile strength, absorbed energy, and strain rate effects of two different cemented clays at 0, 1, 3, 6, 9, and 12 F/T cycles using a static splitting-tensile test and splitting Hopkinson pressure bar (SHPB) test. The experimental results showed that the basalt fiber addition led to a marked increase in the static and dynamic tensile strength of the cemented clay specimen under F/T cycles. In the static splitting-tensile test, the strength decreased with the increase of the number of F/T cycles for the two specimens except 12 F/T cycles. All of the plain cemented clay’s dynamic tensile strength had a sharp decline at one F/T cycle in the SHPB test, while the decrease in the strength at three F/T cycles was larger (more than 50%) for that BFR cemented clay. The law related to absorbed energy was similar to dynamic tensile strength, and the relationship between the two was obtained. Continuous freeze–thaw cycles do not necessarily decrease the tensile strength of cemented clay, and its detailed mechanism was discussed.

This laboratory study investigated the performance of open-gradation cold patch asphalt mixtures using two new solvents, mineral spirit and isoamyl acetate, for patching potholes in porous pavements. Mineral spirit and isoamyl acetate were used as the solvents to produce the cutback asphalt. The test results showed that the mineral spirit and isoamyl acetate cold mixes had greater initial and cured strengths, cohesiveness values, anticracking performances, and rutting resistance than did diesel cold mix; in addition, the mineral spirit and isoamyl acetate cold mixes had lower moisture susceptibility than did the diesel cold mix. The improved coating, mixing, and curing of the new cutback cold mixes were due primarily to the better solubility of the two new solvents with asphalt and their high evaporation rates. For a $100\text{-}\mathrm{kg}$ mixture, using the mineral spirit and isoamyl acetate cutback mixes costs $\$2$ and $\$3$ more, respectively, than using the diesel cutback mix. Considering the cost and toxicity level, the mineral spirit cutback cold mix had better overall performance and ecoefficiency.

This paper addresses effects of hybrid fibers on the flexural and tensile properties of ultrahigh performance fiber-reinforced cementitious composites (UHPFRCC). The workability, compressive strength, flexural strength, and uniaxial tensile properties of designed UHPFRCCs were investigated. The results indicate that UHPFRCC containing 1.5% long steel fiber and 0.5% short steel fiber exhibits the best flexural property. Flexural strength was decreased with the increased amount of plastic fibers, resulting from inhomogeneous distribution of steel fibers. UHPFRCCs with larger amounts of short steel fibers show higher ultimate tensile strength. In addition, first-cracking tensile strength and ultimate tensile strength of UHPFRCC with plastic fibers were reduced but the strain-hardening process was enhanced. An analytical model was utilized to predict the ultimate tensile strength of hybrid fiber-reinforced UHPFRCC; theoretical calculations and the experimental results were in good agreement, which was used to explain the effect of hybrid fibers on the ultimate tensile strength of UHPFRCC. Various hybridization designs of fibers and the high volume of mineral admixtures can significantly reduce the environmental impact and develop a novel cleaner construction product with excellent materials properties.

Sasobit and zeolite warm additives have been used by many to reduce the mixing and compaction temperature of asphalt mixes. Risk of water damage and less resistance to permanent deformation as a result of less binder oxidation is a primary concern associated with roadways paved by warm-mix asphalt. This study evaluates Marshall stability, Marshall quotient, compressive strength, index of retained strength, resilient modulus (MR), stiffness modulus (SM), flexural modulus (FM), and rutting resistance (RR) testing of styrene-butadiene-styrene/asphalt mixtures (SBSAMs) containing sasobit and zeolite additives. In addition, a comparison table was prepared to select the type of SBSAMs for any field application. The test results of SBSAMs made with zeolite show slightly better performance than SBSAMs and sasobit-SBSAMs in terms of rutting, moisture, and temperature susceptibility.