Journal of Materials in Civil Engineering

The present paper analyzes the combination effect of slag and limestone filler on the expansion caused by delayed ettringite formation (DEF). Tests were carried out on heat-cured ternary cement mortars with various replacement levels of cement by both limestone filler and slag (15%, 25%, and 45%). The expansion of heat-cured cement mortars was evaluated and verified by measuring their length change, dynamic elastic modulus, and compressive strength over more than 750 days. The addition of limestone filler and slag to portland cement was found to be beneficial to reducing the expansion caused by DEF. It was found that the use of 10% and 20% slag ternary cements with 5% limestone filler delayed the beginning of the expansion and caused a decrease in the long-term expansion. Meanwhile, the use of 40% slag with 5% limestone filler suppressed the expansion caused by DEF.

Permanent deformation and fatigue cracking are two main distresses on airfield pavement. To enhance material performances, the researchers introduced three additives in this study: namely, two high modulus agents (HM-1 and HM-2) and an antirutting agent (ARA). Two control binders [Styrene-Butadiene-Styrene (SBS)], a modified binder (PG 76-22), and an unmodified binder (PG 64-22) were blended with additives at 0.3% and 0.6% (by the weight of asphalt mixture). The rutting and fatigue resistances of a total of fourteen binders and five mixtures (AC-20) were evaluated by temperature and frequency sweeps, multiple stress creep recovery (MSCR) tests, and linear amplitude sweep (LAS) tests as well as by the Hamburger Wheel Tracking (HWT) and the four-point bending beam (FBB) fatigue tests for mixtures. From the laboratory investigation, it was found that the additions of additives increased the $|G^{*}|/\sin \delta$ and $R$ value and decreased the $J_{nr}$ value at high performance temperatures. Also, the $|G^{*}|$ master curve showed the stiffness of the binder increased when the additive content rose. The antirutting agent (ARA) had more effects on rutting resistance than HM-1 based on HWT results. The relationship between binder indicators ($J_{nr}$ and $|G^{*}|/\sin \delta$) and mixture creep slope was great. As for fatigue performance, HM-1 modified binders showed higher fatigue lives than ARA modified binders at a high strain level. Furthermore, the fatigue life of mixtures at 500 με had weak correlations with fatigue life and $A_{35}$ predicted by the LAS test at the strain level of 2.5%.

Mechanically stabilized earth (MSE) walls often include galvanized steel strips as mechanical reinforcement within layers of specified backfill material. Galvanized steel reinforcement provides considerable tensile strength; however, it is potentially vulnerable to corrosion. Corrosivity of MSE backfill material is typically characterized using electrical resistivity. Many variations of the current AASHTO T288 standard exist to determine this resistivity. However, there is concern that this method may not reflect field conditions, particularly for aggregate backfills, and thus may mischaracterize the corrosivity of these backfill materials. ASTM currently has a proposed standard for coarse aggregate resistivity that addresses this mischaracterization. Five aggregate backfill materials were collected during construction from MSE wall projects located in eastern Kansas. These materials were laboratory-tested using two methods: (1) the current AASHTO standard and (2) a proposed ASTM test method for coarse aggregate resistivity. Results from the laboratory testing were compared with field resistivity measurements of two of the MSE wall backfills post-construction. The proposed ASTM test method appeared to more accurately simulate field conditions behind MSE walls. Increasing the number of soak/drain cycles substantially increased measured resistivity. Recommendations are made based on data included in this paper that should lead to more representative resistivity testing results. These include a minimum electrode spacing of 8:1 and a minimum height of the test box that is three times the maximum particle size.

The influence of silica fume (SF) on the strength and water resistance of magnesium–ammonium phosphate cement (MAPC) was investigated, and the improvement mechanism was also studied by employing analysis techniques that included X-ray diffraction (XRD), scanning electron microscopy (SEM), and scanning electron microscopy–energy dispersive spectrometer (SEM-EDS) tests. The addition of SF is observed to incrementally decrease the flowability of MAPC pastes as well as their temperature during hydration processes. The mechanical properties of all MAPC paste mixtures containing SF were higher than those of a basic control group at all curing ages. Moreover, the water resistance of MAPC samples with SF was also enhanced. The pH of the soaking liquids indicates that the precipitate of MAPC is reduced after adding silica fume. XRD spectrums of MAPC pastes indicated the formation of secondary reaction products (MgSiO₃), except the main hydration product struvite and residual magnesia. The microscopic morphology and internal action of MgSiO₃ were further analyzed by SEM and SEM-EDS.

Clayey soils with medium to high plasticity are prevalent in several parts of the world, causing billions of dollars in damage annually to various civil infrastructures. Several ground-improvement techniques can be employed to counteract this issue. However, these methods are impractical in certain situations and unsustainable in others due to their economic and environmental impacts. Microbial-induced calcite precipitation (MICP) could provide a more sustainable alternative. Researchers have successfully used MICP to alter specific geotechnical properties of sands and silts. This research investigates the applicability of MICP via biostimulation to treat clayey soils with low to high plasticity. The goal is to determine the viability of this technique to alter the engineering behavior of clayey soils, especially given the low permeability of these soils. For this purpose, four soils were selected from four different locations in Idaho and Montana. The soils were selected such that their plasticity varied from low to high to study the effect of plasticity index on the effectiveness of MICP treatments. In addition to the four soils, three additional artificial mixes were studied to study the effect of clay content on MICP effectiveness. Both macroscale and microscale studies were conducted on untreated and biostimulated soils to observe strength gain, swelling reduction, and calcium carbonate precipitation. The results show that MICP via biostimulation would be a promising method to treat problematic clayey soils.

When considering the early-age behavior of massive concrete structures, it is important to accurately reproduce the evolutions of the mechanical properties and their evolutions as a function of the hydration state. In this paper, we propose a method based on data gathered in an extensive experimental campaign to estimate the mechanical properties of concrete depending on its degree of hydration. Once the constitutive equations of elastic, creep, and early age strain properties are clearly defined, these properties are successively calibrated as functions of the degree of hydration. They are next integrated into a mechanical structural calculation for validation. Numerical results are compared to experimental data obtained on a realistic massive structure built especially for this study. First simulations have provided a mechanical response close to experimental data, thereby validating the consistency of both an overall modeling procedure and input dataset.

This article is on the development of a mix design method for self-compacting recycled aggregate concrete (SCRAC) by considering the adhered mortar content (AMC) on the surface of the aggregate. In this method of mix design, the acceptable percentage of recycled concrete aggregate (RCA) depends on the AMC value. Five different batches of design mixes were prepared, including one batch that used conventional design from natural aggregate, two batches that used conventional design from RCA, and two batches that used the proposed design from RCA. In one batch from each of the conventional and proposed design mixes, the RCA was treated with a sodium silicate solution and silica fume in order to assess the effect of treatment. In addition, each of the batches consisted of three different sub-batches prepared with different mixing approaches. The microstructural analysis revealed the reason for best mechanical properties prepared with treated RCA along with proposed two-stage mixing approach (TSMA).

A cold-mixed porous friction course (PFC) with waterborne epoxy resin/polyurethane composite-modified emulsified asphalt was prepared to improve the skid resistance and durability of pavement in hot and rainy areas. The technical parameters of the different structural layers of the cold-mixed PFC were determined. The high-temperature performance, abrasion resistance, water stability, and permeability of the cold-mixed PFC wear layer were investigated systematically. The skid resistance of the cold-mixed PFC wear layer, microsurfacing, and chip seal under different rainfall conditions was compared, and the open traffic time of cold-mixed PFC construction was analyzed. The results showed that the wear layer of cold-mixed PFC exhibited excellent high-temperature performance, abrasion resistance, water stability, and permeability. The skid resistance of the cold-mixed PFC wear layer was less affected by rainfall. When the rainfall intensity was $35\mathrm{mL}/\mathrm{s}/{\mathrm{m}}^2$, the British pendulum number (BPN) values of the wear layer of cold-mixed PFC-5 and PFC-8 were 66 and 73 BPN, respectively. The early strength of the different structural layers of cold-mixed PFC forms quickly, which can ensure the rapid opening of traffic after construction.

Concerning environmental problems caused by ever-increasing waste polymers, this paper developed tire crumb rubber (TCR) combined with recycled polyethylene (RPE) extruded melt blend as a composite additive for asphalt modification, aiming to enhance the performance of binder and reutilize extensively waste polymers. The influences of ratio of constituent, extrusion, and devulcanized crumb rubber (CR) on performance of the modified binder were evaluated by rheological methods. Moreover, the phase characteristics and modification mechanism were investigated by optical microscopy and scanning electron microscope (SEM). The results indicated that extrusion for TCR combined with RPE composite additive leads to a decrease in complex modulus and viscosity of the resulting binder. RPE in the composite additive plays a key role in improving the resistance to permanent deformation and reducing viscoplastic behavior. Microscopy showed the coarse RPE phase enveloping CR particles is favorable for improving rutting resistance of binder, whereas smaller particles and an unobvious polymer phase account for the reduced resistance to permanent deformation of binder with devulcanized CR. Extrusion for composite additive improves storage stability of the resulting binder, and devulcanized CR further facilitates stability. The loosened and porous surface of devulcanized CR in SEM sheds a brilliant light on improved storage stability.

The lubrication layer of concrete plays a vital role in the pumping of concrete. In the present study, the influence of different types of binders ordinary portland cement (OPC), Portland pozzolana cement (PPC), portland slag cement (PSC), and solid volume fraction on the flow properties of the lubrication layer (cementitious pastes) corresponding to 3 grades (M30, M40, and M50) of concrete were investigated. From the results, it is evident that the solid volume fraction (SVF) and shape of binders influence the rheology of cementitious pastes predominantly. Specifically, nonlinear behavior is much pronounced with $\mathrm{SVF}>0.46$ because of shear thickening of cementitious pastes in addition to the shape of particles. Further, this study also emphasizes the need for assessment of the lubrication layer through fundamental parameters (yield stress and plastic viscosity) compared with empirical parameters (spread). The research findings of this paper will be helpful in understanding the pumping potential of concretes with similar cementitious paste composition.

In this study, the performance of self-consolidating high-strength mortars (SCHSMs) produced using portland pozzolana cement (PPC) was evaluated for use in precast concrete applications. The applications may include using SCHSMs (1) for making thin sections with adequate strength and toughness, (2) as a patch material with better adhesion properties with substrate concrete, (3) as a sandwich layer or repair material in newly or existing concrete beams in the tension zone for improved ultimate strengths, and (4) for specialized precast concrete applications demanding high strength. The tests conducted include compressive, flexure, impact, shear strength, and toughness using standard or developed test procedures. Results from the investigation suggested that SCHSMs from PPC can be used for developing complicated sections such as I-specimens; however, significant strength reduction was observed compared with that of equivalent cube specimens. SCHSMs with 0.6% fiber addition showed higher ultimate strength, with toughness and impact energy several times higher than the respective specimens without fibers. The shear bond strength of SCHSMs containing PPC showed higher strength than mixtures made with ordinary portland cement (OPC) or OPC+silica fume blend. In addition, conventional beams made with a part layer of SCHSMs containing PPC provided higher ultimate strength and strains compared with beams made with a part layer of OPC. The heat-cured SCHSMs provided 56%–110% higher early-age strengths than normal water-cured SCHSMs, but the use of high temperature at 140°C or 200°C for 2 days negatively affected the later-age strengths. The shortlisting of curing regimes for PPC mixtures considering both early-age strength and later-age strength for precast concrete was not possible within the heat-curing regimes investigated. The optimized heat-curing regime for OPC may not necessarily be the optimized one for PPC mixtures.

Although many research works are available on evaluating the effect of carbon nanotube (CNT) on intermediate and high temperature performance of asphalt binder, limited studies have been reported for its effect on low temperature properties. Moreover, reported research work showed inconsistent conclusive remarks about its influence on the low temperature properties of asphalt binder. Therefore, along with the conventionally adopted technique, this study aimed at investigating the effect of CNT on low temperature properties of asphalt binder using the dissipated energy-based approach to make an appropriate conclusive remark. CNT content was varied as 0%, 0.75%, 1.5%, and 2.25% by the weight of asphalt binder. Initially, creep stiffness and creep rate corresponding to 60 s creep period were evaluated. Although CNT addition changed the creep stiffness and creep rate, the impact was not statistically significant at 0.75% CNT. However, a subsequently higher dose of 1.5% CNT significantly increased the creep stiffness and decreased the creep rate. A master curve for creep stiffness, relaxation modulus, creep stiffness rate, and creep relaxation rate was drawn to understand the effect of prolonged creep period on low temperature properties. The detrimental effect of CNT on low temperature properties of asphalt binder was found to be apparent, especially in a higher creep period zone. Subsequently, viscoelastic modeling of creep compliance data obtained from a bending beam rheometer (BBR) test was carried out using the Burgers model. Different energy components (stored and dissipative) were subsequently evaluated based on model parameters. Stored, as well as dissipated energy components, were found to be decreasing with an increase in CNT content to 1.5%. However, the degree of decrease in the dissipated energy component was found to be relatively higher compared to the corresponding decrease in the stored energy component. As a result, the dissipated energy ratio (DER), which is expected to be higher for better low temperature performance, was found to be decreasing with the incremental dosages of CNT. Although CNT addition decreased the DER value, the impact was not statistically significant at 0.75% CNT. However, a subsequently higher dose of 1.5% CNT showed a significant decrease in DER value. Such a response further reinforced that CNT addition may have a negative impact on low temperature properties of asphalt binder.

In recent years, asphalt pavements have been widely used due to their desirable properties: safety, smoothness, and durability. However, the aging of bitumen during its service period is inevitable, so the performance of asphalt pavement will decline. Thus, it is necessary to investigate the aging mechanism systematically to offer a new way of illustrating changes during the aging process, and the investigation of the short-term aging mechanism could be a first step. This study explored the variations of rheological properties and molecular weight distribution during the aging process, and the data obtained by gel permeation chromatography (GPC) were analyzed by principal component analysis. The experiments in this research include preparing aged bitumen samples under five aging temperatures and six aging durations, and then tests were performed using a dynamic shear rheometer (DSR), bending beam rheometer (BBR), and GPC. The results indicate that the aging increased complex modules ($G^{*}$), creep stiffness ($S$), and fatigue resistance index ($N_f$) but decreased phase angle ($\delta$) and $m$-values. In addition, the transformation from medium molecular size to large molecular size was found to be the most significant phenomenon during the aging process. Moreover, during the aging process of bitumen, the molecular weight distribution index polydispersity index was found to have the best correlation with rheological properties.

This study investigated the effect of ${\mathrm{CaCl}}_2$-blended acrylic polymer emulsion (CP) at 0%, 0.5%, 1.0%, and 1.5% by weight of cement on the degradation of alkali–silica reaction (ASR) susceptible fine aggregate particles. Mineralogical and textural characterizations of reactive aggregate particles were evaluated via X-ray diffraction (XRD) and scanning electron microscopy–energy dispersive spectroscopy (SEM–EDS) analyses. ASR expansion and the chemical composition of the reaction product were also assessed. Results indicate significant ASR expansion ranging from 0.35% to 0.42%, which is traced to the presence of reactive cristobalite/tridymite phases, porous, inequigranular, and alkali-releasing particles in the fine aggregate. The addition of CP to mortar had conflicting effects on the ASR expansion of mixtures. Relative to the plain reference mortar, a 0.5%–1.0% addition of CP slightly reduced ASR expansion. However, when CP content was increased beyond 1.0%, the trend reversed, and increasing expansion, albeit comparable to that of the reference mortar, was observed. On the other hand, increased degradation of single-grained silica-rich aggregate particles, higher $\mathrm{Na}+\mathrm{K}/\mathrm{Si}$ ratio and elevated ${\mathrm{Na}}_2{\mathrm{O}}_{\mathrm{eq}}$ of gels formed on vesicular particles were observed in the reference mortar. Overall, the reductions in expansion observed in mortar containing 0.5%–1.0% CP dosages are attributed to the influence of CP in reducing moisture transport, gel swelling, and the increased tensile strength of mortar. However, beyond the 1.0% CP content, it seemed that all the aforesaid benefits were offset by the formation of larger quantities of gels as a result of increased ${\mathrm{Ca}}^{+2}$ ions in the mortar containing 1.5% CP.

Bearing reinforcement is an inextensible reinforcement type that is manufactured by welding strongly between a longitudinal member and a set of transverse members. The pullout capacity of the bearing reinforcement comprises both friction and bearing components. In this research study, the test results of residual red clay and previously published test results were analyzed to develop rational pullout predictive equations. The pullout friction resistance can be calculated by utilizing the soil-reinforcement interaction factor, $\alpha$, which reduces linearly with fines content ($F$). The bearing pullout resistance is controlled in the failure plane of transverse member ($\beta$) and transverse members interference factor ($IF$). The water content to optimum water content ratio, $w/w_{owc}$ and $F$, were found to be dominant factors controlling both $\beta$ and $IF$. The $\beta$ reduced from $\pi /2$ to $\pi /3$ with the increase in $w/w_{owc}$ and $F$. The transverse members interference zone was larger for lower $w/w_{owc}$ and $F$. Equations for predicting $\beta$ and $IF$, in terms of the fines content and water content, are proposed in this paper.

Lime is often used to increase strength, reduce compressibility, and reduce moisture sensitivity in soils with moderate to high plasticity. In the case of road construction, state agencies typically have specifications that prevent lime stabilization of subgrade soils during low temperatures (e.g., $<4°\mathrm{C}$). Part of the rationale for these specifications is that lower curing temperatures reduce the kinetics of pozzolanic reactions, which in turn may prevent the design strength from being reached. The objective of this research was to investigate the effect of temperature and time on reactivity and strength for lime-soil mixtures. The pH, electrical conductivity, and unconfined compressive strength of soils mixed with varying lime contents were respectively measured at various curing temperatures at multiple curing periods. Results indicate that increased curing duration leads to decreases in pore fluid pH and conductivity. However, this reduction in pH is less at temperatures below 10°C, which indicates lower levels of reactivity. Increased lime is recommended for situations in which stabilization will proceed at cooler temperatures. Unconfined compressive strength does not significantly increase with curing duration until after 7 days, after which the effect of pozzolanic reactions is evident. The trend of increasing unconfined compressive strength with increasing temperature was observed for both short- and long-term curing durations. The 7-day cured sample strengths at 2°C increased by 10% when allowed to cure for 56 days, while the samples cured at 21°C increased by 100% with the same curing duration. Exposure to either freeze-thaw cycles or low curing temperatures (2°C) resulted in significant reductions in strength gain for a given curing duration. However, once the freeze-thaw cycles or temperature reduction was removed, strength gain resumed at approximately the same rate. Overall, these results suggest that current specifications may be modified to allow lime stabilization to proceed in lower temperatures, if a corresponding increase in curing time and/or thermal protection is provided.

The aim of this work was an evaluation of the influence of titanium dioxide on the chemical and physical properties as well as the aging behavior of bitumen. Accordingly, two samples of paving grade bitumen $50/70$ and one polymer modified bitumen sample 25/55-55 A were modified with two different titanium dioxide products. These bitumen samples were investigated in different modification and aging states, to evaluate the photocatalytic and filler effects of the titanium dioxide. The investigation procedure included different analytical methods, like Fourier Transform infrared spectroscopy, asphaltene separation, thin layer chromatography, as well as different physical methods like the determination of the softening point ring and ball and needle penetration along with investigations with a dynamic shear rheometer. The results did not show any negative effects of the titanium dioxide on the properties of bitumen. In contrast, a positive influence on bitumen aging could be recognized in regard to different chemical and physical parameters. However, the extent of the property changes depended on the types of bitumen and titanium oxide used.

The addition of polycarboxylate superplasticizers (PCE) can alter the microstructure of dispersion system, and hence improve the fluidity of cement paste. In this paper, adsorption isotherms of PCE as well as the rheological and the hydration properties of cement paste have been systematically investigated. Cement hydration property was analyzed by isothermal calorimetry, differential thermal analysis (DTA), and thermogravimetric analysis (TG). The pore structures were investigated by mercury intrusion porosimetry (MIP) and dynamic water vapor sorption (DWVS). The microstructure and composition characteristics of hydration products were investigated by scanning electron microscopy (SEM) equipped with secondary electron imaging (SEI), backscattered electron imaging (BSE), and energy dispersive X-ray spectrometer (EDS). The results indicate that a higher PCE dosage leads to an increase of fluidity and a decrease of apparent viscosity as well as yield stress of fresh cement paste, owing to the disassembled flocculation and the released water from flocculation. The adsorption of PCE shows a double-layer adsorption behavior. The first adsorbed layer of PCE attributes to the zeta potential and the fluidity of cement paste, while the second adsorbed layer makes no contribution to these properties. The hydration degree of the cement paste is hindered by the addition of PCE at 1 day, but promoted at 3 days, while the promotion of hydration process almost vanishes at 28 days. The addition of PCE decreases the size of hydration products in hardened cement paste and changes the composition of hydrated calcium silicate (C-S-H) gel. The decreased porosity as well as average pore size due to good dispersion capability of PCE significantly improves the concrete performance.

The semicircular bending (SCB) test is used to characterize crack propagation of asphalt mixtures at intermediate temperatures using the critical strain energy release rate or the flexibility index, known as the Louisiana method and the Illinois method, respectively. Both methods neglect the effect of dissipated energy during testing, which may cause variability in materials characterization. This study used the probability density function of Weibull distribution to develop a relationship between the load-line displacement and the corresponding load for the SCB test at various temperatures. Two mathematical models are presented to compute two parameters, the initial bending stiffness and the normalized Shannon entropy, which is a new approach to parameterize the specimen’s mechanical response during loading. These two parameters are used to characterize crack propagation resistance of asphalt mixtures; at the same initial bending stiffness value, higher normalized Shannon entropy values may indicate better resistance to crack propagation. On the other hand, at the same Shannon entropy value, higher initial bending stiffness values may indicate the ability to carry heavier loads.

The flexural behavior of basalt textile-reinforced concrete (BTRC) with and without pretension and with one of two types of short fibers was investigated using an instrumental four-point bending test under quasi-static loading. BTRC samples consisted of five layers of basalt textile, with and without pretension, and the cement matrix contained short carbon or steel fibers in various volume fractions (0%, 0.5%, 1.0%, and 1.5%). Critical flexural performance, including first-crack stress, flexural strength, energy absorbed, flexural strain at peak stress, number of cracks, and crack spacing, were analyzed. Test results revealed that the addition of short fibers in the BTRC samples enhanced their flexural capacity. The addition of short fibers (1.0 vol%) without pretensioning resulted in good crack patterns and flexural mechanical properties. The reinforcing effect of BTRC with pretensioning was more apparent than that of BTRC without pretensioning. The maximum flexural strength of all samples reached approximately 23.6 MPa, which was approximately triple that of the first-crack stress of the pretension samples. The addition of short steel fibers (1.0 vol%) in flexural samples without pretension showed the highest flexural strength. The maximum flexural strain and crack patterns obtained by experiments and digital image correlation revealed satisfactory agreement. Weibull analysis was conducted to quantify the variability in BTRC flexural strength with different short fiber types and volume fractions. Textile pretensioning, type and type and volume fraction of short fibers were shown to significantly affect the flexural behavior of BTRC.

Multigrade bitumen asphalt is a quality asphalt product that is not used in many places globally. Multigrade bitumen is believed to be less sensitive to temperature, which gives it an advantage over conventional binders. Previous testing has shown that asphalt temperature changes greatly with depth, but currently the industry standard is to nominate a single temperature for design. For detailed design of asphalt roads, perhaps asphalt layers should be divided into nominal layer depths and different modulus and fatigue equations/values should be used to reflect the temperatures of each respective layer. Previous laboratory testing conducted on multigrade bitumen asphalt beams under a range of temperatures and loading conditions was analyzed. The samples tested included 0% or 15% recycled asphalt pavement (RAP) to determine the impact of the recycled material on the fatigue life and stiffness of the pavement. This study investigated the temperature susceptibility of multigrade bitumen asphalt pavements compared with that of conventional binders by combining previous testing that included conducting a range of fatigue tests, developing complex modulus master curves for each mix, and a study of how pavement temperature changes through pavement depth. The materials properties were analyzed using the pavement design software. This investigation found that the final design of the pavement is greatly affected by the nominated pavement temperature and respective material properties. This paper outlines a potential revision to the current design approach for asphalt pavements and proposes that further investigation is needed into pavement temperature and its incorporation into design.

Cross-laminated timber (CLT) is a massive panel product made from orthogonal layers of solid-sawn lumber. Because of its composite nature and engineered layup, CLT provides the possibility of a substantial market for underutilized and lower-quality tree species. This paper presents a study that evaluates the structural performance of three-layer CLT panels fabricated from two such tree species grown in the northeastern US: eastern hemlock and eastern white pine. A total of 17 panels measuring $99\times 305\times 3.048\mathrm{m}$ were fabricated and tested to evaluate major and minor axis bending properties (apparent and effective bending stiffness and bending moment capacity) and major axis shear property (effective shear stiffness). When compared with reference design values of the American National Standards Institute/American Plywood Association (ANSI/APA) PRG 320 established CLT grades, the results show that both eastern hemlock and eastern white pine panels satisfy baseline structural performance requirements of the ANSI/APA PRG 320 standard.

The use of reclaimed asphalt pavement (RAP) has significantly increased in construction and rehabilitation of flexible pavements to ensure proper use of limited natural resources. Bio-oils could act as a rejuvenator and reduce the stiffness of binders and mixes with high RAP content. Two oils, namely waste cooking oil (WCO) and soy oil, are potential sources of bio-oils that are abundant and can potentially be used. This study was conducted to explore the effects of the bio-oils on binder and mixture properties that contain a high percentage of RAP binder. Two different types of aggregates and virgin binders were used in the study, along with a RAP binder that was extracted and modified by the bio-oils in the laboratory. Rheology of the modified binder was evaluated, and hot mix asphalt (HMA) specimens prepared using the modified binder were tested to determine the rutting, fatigue cracking, and low-temperature cracking resistance. The test results indicated the improved and typical performance of HMA with the modified binder.

Quantifying the degree of hydration of mineral additives in a blended system has been a challenge in the concrete research community. This study attempted to calculate the degree of hydration of both clinker and ground granulated blast furnace slag in a slag-blended cement system based on nondestructive detection by X-ray micro–computed tomography (CT). Ordinary portland cement (OPC) pastes and slag-blended cement pastes were used with water-to-binder ratios of 0.3 and 0.5. The degree of hydration was calculated by comparing the volume fraction of the unhydrated phase with its original value. The key to quantification is to segment different phases (clinker, hydration products, and pores) in CT images, and then the volume fraction of the unhydrated phase can be obtained. Grayscale gradient–based edge detection was introduced for the first time to segment CT images of the cementitious materials. The degree of hydration quantified from the CT images was compared with that obtained from classical Thermogravimetric analysis (TGA). The use of X-ray CT to quantify the degree of hydration of OPC and slag-blended pastes was shown to be feasible. A suitable segmentation method for CT image of cementitious materials was recommended.

Nowadays, polycarboxylate-based (PCA) superplasticizer (SP) has become the basic ingredient to prepare high-performance concrete (HPC). PCA SP with carboxylic sulfonic groups and long poly (ethylene oxide) side chain was prepared. The behaviors and economies of PCA SP-blended concrete were investigated. Inclusion of PCA SP improves the initial fluidity and fluidity preservation of concrete. Utilizing PCA SP increased the air content and bleeding water rate and prolonged the setting times of concrete, which have a negative effect on the early-age properties of concrete. At the early curing age (7 days), concrete mixtures with 0.20% and 0.24% PCA SP have the slightly lower mechanical properties and higher water porosity than control concrete. Beyond a certain amount of PCA SP (0.24%), a large reduction in the mechanical properties and a rapid increase in the water porosity can be found in concrete. The introduction of PCA SP to concrete lowers the resistance of concrete against chloride ion penetration and increases the total material costs. The prolonged curing period is an effective method to improve the long-term properties of PCA SP series concrete. Based on the consideration from the early-age properties and the economies of concrete, at the given fluidity, an optimum amount of PCA SP must be chosen in the production of concrete.

The aim of this study was to investigate the influence of polymer 2 hydroxyethyl methacrylate (PHEMA) with different amounts (3%, 5%, and 7% by weight) on physical and high-temperature rheological properties of bitumen. The modified bitumen properties were evaluated by using optical and scanning electron microscopes, rolling thin film oven, pressure aging vessel, penetration degree, softening point, ductility, viscosity, and temperature sweep tests. The results showed that PHEMA was well dispersed in bitumen, and the samples were homogeneous mixtures. The difference in softening points of the top and the bottom of PHEMA-modified bitumen samples indicated that storage stability was acceptable. Also, the results showed that PHEMA increased the high-temperature performance grade and the permanent deformation resistance of pure bitumen.

One of the main aspects of sustainable engineering constructions is the recycling of byproduct materials or wastes, including those from different agricultural crops. The influence of ternary-blended binders—ordinary portland cement (OPC), ultrafine palm oil fuel ash (UPOFA), and silica fume (SF)—on the engineering and transport properties of ultrahigh-strength green concrete (UHSGC) has been investigated. Up to 50% of the UPOFA was combined with varying proportions of silica fume at 5%, 10%, 15%, and 20% from the volume of the portland cement in order to quantify their influence on the engineering and transport properties of the UHSGC. The results showed that the UPOFA inclusion reduced the early age strength of the UHSGC at 3 and 7 days, then slightly improved the strength at the ages of 28 and 90 days. Whereas, the SF inclusion, as a ternary-blended binder in combination with the UPOFA, significantly enhanced the early and long-term strength for all UHSGC mixes, in comparison with the OPC control mix. The highest compressive strength was realized at 20% SF content, which exceeds 152 and 157 MPa at the ages of 28 and 90 days, respectively. The transport properties of the UHSGC, specifically, porosity, water permeability, and rapid chloride permeability, were significantly improved with the utilization of the ternary-blended binder. Consequently, the overall results demonstrated the feasibility of utilizing up to 70% of byproduct based pozzolanic materials (UPOFA and SF) as a blended binder to partially substitute the portland cement to improve the properties and durability performance of the UHSGC. Furthermore, new relationships between compressive strength and transport properties of the different mixes were presented, and a good correlation between these properties and compressive strength for this type of concrete was obtained.

Micromechanical fracture models, void growth model (VGM) and stress-modified critical strain (SMCS) model, can predict the ductile fracture of structural steels by investigating the growth of microvoids existing inside materials. Based on test results on smooth notched tensile specimens, in this paper, material parameters in the VGM and the SMCS model were calibrated for G20Mn5QT cast steel. A monotonic tension test on a double-hole plate specimen was carried out to verify the calibrated material parameters. Predictions for the ductile fracture initiation of the double-hole plate specimen by the two micromechanical fracture models agreed well with test results. The fracture propagation of the double-hole plate specimen during the whole loading process was then simulated by deleting fractured elements identified by the VGM. The load-deformation curve and fracture propagation process obtained by numerical simulation were consistent with the test results, which further verified the calibrated material parameters and the approach to simulating fracture propagation based on the VGM.

The use of construction waste as a subgrade backfill material is a very promising approach to solve the problems of the rapidly increasing amount of construction waste and the shortage of construction materials. This paper considers the correlation between the brick content and the crushing behavior of construction waste. First, the composition and physical parameters of construction waste from Xi’an City in northwest China were investigated. Secondly, crushing tests on the coarse particles were conducted to determine the crushing ratios of samples with different brick contents. Crushing over the entire range of particle sizes was tested, and the mass changes for the different size categories were measured. The deviation indices of the samples were then calculated. The crushing ratio and the deviation index fluctuated with the brick content. Finally, the particles in the samples were observed by using a stereomicroscope for visual inspection. The appropriate brick content is suggested, and the California bearing ratio (CBR) test values of the corresponding samples meet the required specifications. The research can be used as a reference for the reuse of construction waste.

Application of green cement to replace ordinary portland cement (OPC) for concrete structures has become an active research interest. Using pull-out tests, this study explored the bond behavior of embedded rebar confined by concretes made with two kinds of no-cement binders: (1) a hydraulic binder consisting of a ternary mixture of ground granulated blast furnace slag, low calcium fly ash, and circulating fluidized bed combustion (CFBC) fly ash, which is known as slag-fly ash-CFBC (or SFC) binder; and (2) an alkali-activated slag (AAS) binder. The experimental results showed that, at equivalent grades of 28-day compressive strength, the bond strength of the embedded rebar confined by concrete made with the SFC binder ranked the best, followed by OPC binder in the second place, and the AAS binder in the third place. Analysis of bond quality showed the satisfactory compatibility between the reinforcing bars and the confined green concretes, highlighting their high potential for successful application to the practical construction of infrastructure.

In recent years the plastic industry has developed a new type of synthetic macrofiber based on polyolefins that complies with the requirements of existing standards in considering contributions of fibers in the structural design of reinforced concrete (RC) elements. In meeting such requirements, the possibility of improving the results with lower fiber dosages by means of an admixture could provide new advantages. A previous study incorporated a bond improver admixture that increased the postcracking strength that appears after the first decrement of the load by 44%. At that time, the theoretical mechanisms of the admixture remained under discussion. The present research assessed the changes introduced by the bond improver admixture that enhance such residual flexural strengths. Pull-out tests and microstructural analysis of polyolefin fibers embedded in a concrete matrix of a previous study were taken as a reference. Therefore, specimens were manufactured with the same concrete mix and sizes. The bond improver admixture was added in some of them. Pull-out tests showed that the maximum load for extraction was lower with the admixture, although the overall energy of extraction was higher. Additional specimens were analyzed to assess the role of the bond improver admixture in the hydration process.

The mechanical behavior of the concrete–epoxy bonded interface is of high importance in concrete strengthening and repair systems. This paper presents the effects of cure time, sustained load, and different temperatures on the time-dependent deformation of a concrete–epoxy interface (CEI) and on the fracture behavior of the CEI at room temperature. Notched three-point bending specimens were used for this experimental study. Elevated temperatures during sustained loading increased the crack mouth opening displacement (CMOD) of the CEI, as did less curing time prior to sustained loading. Both of these results can be attributed to viscoelastic deformation of the epoxy. In fracture tests conducted after the sustained loading period, it was observed that the ultimate load and total fracture energy of the CEI specimens asymptotically decreased in comparison to control specimens that did not undergo sustained loading. Image analysis of the fracture surfaces showed an increase in the incidence of the interfacial failure mode with sustained loading, corresponding to reduced bond performance.

As a type of thermosetting material, any improper or faulty operation of the epoxy asphalt cannot be rectified if the irreversible reaction has taken place. This has brought difficulties to the construction organization of epoxy asphalt pavement. The objective of this study is to evaluate the paving performance of epoxy asphalt mixtures (EAMs) and to predict the allowable time for paving and traffic opening. The viscosity curves of epoxy asphalt binder (EAB) were first measured under different reserved temperatures, and a viscosity growth model considering the time-temperature characteristic was proposed. The Marshall tests were also carried out on EAM under the preset reserved temperature and time to measure the Marshall stability (MS) and the air voids. The permissible reserved time at various reserved temperatures can be obtained through either the viscosity test on EAB or the Marshall test on EAM. The applicability of the two methods was compared, and the temperature influence was discussed. Additionally, the Marshall test results indicate that the relationship between the MS growth rate and the curing temperature follows the Arrhenius law: the traffic opening time of the EAM pavement can be forecast once the temperature-dependent rule is established. The results of this study can provide practical guidance to the mixing, paving, and curing processes of the EAM pavement.

In this study, the effect of nano-${\mathrm{SiO}}_2$ on the mechanical properties, microstructure, and hydration process of cementitious materials incorporating hydrophobic admixture (CM-HA) was studied through mechanical strength and hydration heat tests, x-ray diffraction (XRD), a scanning electron microscope (SEM), and mercury intrusion porosimetry (MIP). The results showed that the addition of hydrophobic admixture reduced the compressive strength of cement paste by about 18% in 28 days, and the addition of nano-${\mathrm{SiO}}_2$ increased the strength of cement paste incorporating hydrophobic admixture by about 20% after 7 days, which indicated that the mechanical properties and strength development of CM-HA could be significantly improved by nano-${\mathrm{SiO}}_2$ due to the nucleus effect, hydration activity, and nano-filling function, although hydrophobic admixture was not beneficial for the strength development due to the delay for hydration process. Results also indicated that nano-${\mathrm{SiO}}_2$ could significantly accelerate the hydration rate and reduce the porosity of cement, especially the porosity of macropores. This study provided a new research method for alleviating the adverse effects of hydrophobic admixture on the mechanical properties and durability of concrete and implemented the application of nano-materials in hydrophobic materials.

To solve the rutting damage of asphaltic pavement and the adverse effects of urban heat islands, diatomite-adsorbing polyethylene glycol (PEG), that is, diatomite-supported PEG (PEG/diatomite), was synthesized as a form-stable composite phase change material (CPCM), which was used as a modifier to prepare the temperature-adjusting asphalt, which can lower the temperature of the road surface on a hot summer afternoon. The microstructure and chemical structure of CPCM were investigated using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectra. Also, effects of CPCM on the thermal properties, morphology, and rheology of modified asphalt were studied via differential scanning calorimetry (DSC), atomic force microscopy (AFM), and dynamic shear rheometer (DSR) testing. It was found that the phase change enthalpy of CPCM is approximately $9.0332\mathrm{J}/\mathrm{g}$, which is up to 60% of the theoretical enthalpy. In the laboratory test, the highest temperature variation of the temperature-adjusting asphalt specimens was $\sim 9.0°\mathrm{C}$, which plays an effective role in regulating pavement temperature. Small bee structures were observed on the surface of PEG/diatomite-modified asphalt and showed no obvious changes from before to after aging.

Double-layer paving technology is a new construction technique for asphalt pavements. Few laboratory studies have been conducted on the influences of pavement layer thickness and mixture types on the high-temperature stability of double-layer pavement surfaces. This paper aims to evaluate the effectiveness of different paving technologies, mixture type combinations, and structural layer thickness combinations on the high-temperature stability of pavement surfaces. The results indicate a 15% improvement in the dynamic stability of double-layer paving and a 7% reduction in rutting deformation relative to that of conventional paving. Compared to the AC-13/AC-25 combination, the AC-16/AC-20, AC-16/AC-25, and AC-13/AC-20 mixture type combinations enhance dynamic stability by at least 69%, 58%, and 26%, respectively, and decrease rutting deformation by at least 18%, 5%, and 3%, respectively. Thickness combinations of 4/6 cm and 3/7 cm improve dynamic stability by at least 35% and 67%, respectively, and decrease rutting deformation by at least 14% and 26%, respectively, compared to the 5/5 cm thickness combination. To effectively improve the high-temperature stability of pavements, a double-layer pavement structure with a 3 cm AC-16 surface layer and a 7 cm AC-20 bottom layer is recommended. The pavement compaction and roughness of double-layer paving meet the standard requirements, as verified, through field testing.

This paper presents an experimental study on glued-in rebar glubam (glued laminated bamboo) joints. The main experimental parameters were anchorage length, glue-line thickness, and the angle between bar and bamboo fibers. The influences of the parameters on pull-out strength, initial stiffness, and the bond behavior of glued-in rebar glubam joints were investigated through pull-out tests. Four typical failure modes are discussed, including pull-out failure of rebar, pull-out of rebar along with splitting of glubam, splitting of glubam block, and yielding of rebar. The critical anchorage length of the specimens with rebar perpendicular to the grain was suggested to be 12 times the diameter of rebar while other specimens should be 16 times, and 4 mm was the most suitable value for the glue-line thickness. The load-slip curve and the average initial stiffness were analyzed based on the bond length, glue-line thickness, and angle between bar and bamboo fibers. The initial elastic portion of the bond stress-slip curve of the glued-in rebar glubam joints can be approximately analyzed by a simple analysis model with assuming linear spring bond links. Finally, a design equation of pull-out strength was proposed based on the testing data.

In order to study the thermal properties of reactive powder concrete (RPC) at high temperatures, the thermal conductivity, thermal diffusivity, specific heat capacity, and linear expansion coefficient of hybrid fiber-reinforced RPC at 20°C–900°C are measured. The formulas of thermal parameters with the volume fraction of polypropylene fiber and the elevated temperatures are fitted and compared with the ordinary concrete (OC) and high-strength concrete (HSC). The results indicate that as the temperature increases, the thermal conductivity and thermal diffusivity first descend and then rise, while the linear expansion coefficient and specific heat capacity first increase and then decrease. The thermal conductivity and specific heat capacity of RPC are lower than that of OC and HSC, and the thermal diffusivity coefficient of RPC is lower than that of HSC and higher than that of OC. Through inputting the measured thermal parameters to the finite-element software, the simulated temperature–time curves of hybrid fiber-reinforced RPC are obtained and compared with the measured curves. It is found that the two curves are basically consistent, and thus the measured thermal parameters are accurate and reliable, and can be used in the numerical simulation analysis of RPC structures under fire.

Studded tires are used during winter seasons to reduce snow- and ice-related accidents in several cold climate regions. However, during driving the studs in these tires progressively punch into the asphalt pavement and displace small aggregates, which eventually results in pavement rutting. This article reports the results of a comprehensive testing program conducted to identify potential materials and mix design variables for the development of a wear-resistant asphalt mix to reduce the studded-tire wear associated with traffic accidents and repair/rehabilitation costs without compromising field performance. These included asphalt binder content and asphalt performance grade (PG), nominal maximum aggregate size (NMAS), aggregate type, gradation type, and addition of crumb rubber. The results show that an open-graded mix is not an appropriate alternative for studded-tire wear-resistance purposes. Slightly increasing the asphalt binder content can effectively improve the studded-tire wear resistance of asphalt mixtures with NMAS of 12.5 mm. However, this effectiveness is reduced with NMAS of 4.75 mm. Any increase in asphalt binder content to improve studded-tire wear resistance must be carefully done because it may affect permanent deformation resistance. On the contrary, crumb-rubber modification of asphalt binder is not a good option for the improvement of studded-tire wear resistance, but it can clearly improve the permanent deformation resistance as indicated by the flow number (FN) test results. Slightly increasing the fine aggregate content and changing the PG of asphalt binder can slightly improve studded-tire wear resistance, but the improvement is not statistically significant.

Pothole repair for porous pavements requires the patching mixture to have sufficient connected air voids, high strength, low moisture susceptibility, and high abrasion resistance. In this study, a cold patch asphalt mixture for porous pavements was designed. Turpentine was used as the solvent for the cutback asphalt, replacing diesel. The bentonite-cement was used as a mineral filler to improve adhesiveness between the aggregates and asphalt. Laboratory tests were conducted to investigate the initial strength, fully cured strength, moisture susceptibility under soaking and freeze-thaw cycling, and abrasion resistance of the designed cutback asphalt mixture. Test results showed that turpentine had a similar solubility parameter with asphalt but a higher evaporation rate than that of diesel. The cold mixtures had sufficiently high air voids of 20%. The cold mixtures produced with turpentine showed higher initial and cured strength, lower moisture susceptibility, and higher abrasion resistance, as indicated by a lower Cantabro loss value. Due to the relatively good solvability with asphalt and the higher evaporation rate of turpentine, the cold mixtures were thoroughly mixed, the aggregates were more evenly coated, and the performance of the designed mixtures was greatly improved.

Highway agencies are using reclaimed asphalt pavement (RAP), particularly cold recycled asphalt mixtures (CRAMs) more than ever before. CRAMs have been also used by a Korean contractor, but it was observed that pavements constructed with this material in the base layer experienced cracks and other distresses on the surface. Thus, an investigation was carried out to find causes and potential improvements. A case study conducted on a substance called “Contractor Mix,” including asphalt emulsion, acrylate polymer (AP), and portland cement with a significantly high cement to emulsion ratio resulted in undesired brittleness rendering it similar to cement treated RAP mixture. In the present study, Contractor Mix was further evaluated along with a control hot mix asphalt (HMA) and portland cement concrete (PCC). Also, three more CRAMs with different proportions were evaluated with the same ingredients as Contractor Mix. Experimental study was performed by conducting asphalt mixture tests including dynamic modulus, indirect tensile strength, and compressive strength. Finally, performance of pavements constructed with different CRAMs in base layer were predicted using AASHTOWare Pavement ME Design. The simulated results predicted that while pavements of Contractor Mix would experience transverse cracking, those with HMA, PCC, and all other CRAMs would perform satisfactorily under the conditions investigated in the present study.

This study investigates the effect of soaking conditions on the durability of soft soil treated with soda residue and ground granulated blast furnace slag. Specimens were cured for up to 60 days and soaked in solutions for up to 28 days. Tap water (T), NaCl (N), ${\mathrm{MgSO}}_4$ (M), and $\mathrm{NaCl}+{\mathrm{MgSO}}_4$ (N-M) were selected as soaking solutions. The results indicate that the stabilized soil was durable in tap water even cured for two days. When soaked in T or N environment, the strength of the specimens increased with soaking period due to dense structure and hydrated gel filling between matrix. The strength of the specimens soaked in solutions was slightly higher than that in tap water. However it decreased slightly after soaking for 28 days in M or N-M environment due to looseness at the ends of the specimens and formation of ettringite cluster. The effects of reinforcing and filling-in of hydration products, including calcium silicate hydrates, ettringite, calcium chloroaluminate hydrates and calcium chloride hydroxide hydrate, contributed to an improvement in strength and durability.

The wet–dry cycles test examines the durability of stabilized soils. The deterioration process in this test can be attributed to multiple factors, so this attempt aims to explore the most important one. Uniaxial compression strength, shrinkage, and wet–dry cycles test results were applied in coupled and transient thermo-hydro-mechanical analyses to simulate one cycle of the test. It is found that moisture diffusion generates high stresses in the surface which indicates shrinkage as the dominant degrading factor.

Salt scaling is a commonly observed durability issue in concrete exposed to a combined salt and frost attack. This damage is restricted to a very thin surface region causing the removal of mortar flakes. This study demonstrates the surface-swelling characteristics of different concrete mixes. Significant paste swelling of the embedded fine silica sand peripherally occurs around the coarse aggregate particles in concrete mixes having a high water/cement ratio or insufficient air entrainment. Localized scaling is observed in concrete mixes with a denser matrix. The severity of this phenomenon is related to the magnitude of cryogenic suction governed by the permeability of the paste. Surface scaling is proposed to be the generator of bulging stress due to confined expansion from ice growth.

Lateral loads such as wind and inertial forces from earthquakes are resisted by the bond strength of brick masonry structures. The consideration of uncertainty in both load and resistance capacity is vital for limit state design of masonry structures. This paper investigates the variability associated with shear, flexure tensile, and split tensile bond strength of fly-ash brick masonry. The bond strength data were obtained from laboratory-prepared specimens made of commercially available fly-ash bricks. Three goodness-of-fit tests, namely Kolmogorov-Smirnov, Kolmogorov-Smirnov-Lilliefors, and Anderson-Darling, were carried out on the selected distributions, and the most appropriate distributions for modeling the considered bond strength parameters are recommended.