Journal of Materials in Civil Engineering

In this paper, three recycled coarse aggregates (RCAs) with different 24-h water absorptions (5.67, 3.12, and 1.98 wt%) were used to produce recycled coarse aggregate concretes (RCACs). Different water absorption rates were obtained by modifying the surface of RCAs with low and high concentration of alkaline organosilicone modifier that is stable in concrete. A normal aggregate concrete mixture was also prepared to serve as control mixture. The effect of RCA absorption on the microstructure (interfacial transition zone), mechanical properties (compressive strength, modulus of elasticity, and concrete-rebar bonding strength), and durability (shrinkage and water permeability) of the resulting RCAC was investigated. Test results showed that the surface modification of RCA was effective in reducing the water absorption. From micrographs, RCAC prepared with low concentration of surface modifier (No. 2 RCA) showed mechanical interlocking with the surrounding cement matrix. Among RCAC, No. 2 RCA (with low concentration of surface modifier) showed better mechanical and durability performance due to the mechanical interlocking which served as effective force transmission medium between aggregate/cement matrix. It can therefore be concluded that RCA prepared with low concentration of surface modifier improved the properties of RCAC. In addition, it may be used as a potential tool to reduce possible slump loss in fresh concrete thereby resulting in consistent mix and providing greater flexibility in mix design.

The multiscale nature and multiscale cracking behavior of cementitious composite determine its micro-, meso-, and macroperformance. A new kind of fiber hybridization containing steel fiber, polyvinyl alcohol (PVA) fiber, and cheap calcium carbonate (${\mathrm{CaCO}}_3$) whisker (approximately $230 per ton) was designed to increase the multiscale cracking resistance for cementitious composites. Mechanical properties, microstructures, reinforcing mechanisms, and economic efficiency of this designed hybrid fiber-reinforced composite were presented. The results indicated that both the flexural strength and flexural toughness are significantly improved. Scanning electron microscopy images and fracture tests confirmed that the interaction of different fibers and multiscale cracks contributes to enhancing the mechanical properties of cementitious composite, which is also reflected in its deflection hardening performance and multiple cracking behavior. Moreover, it seems possible that the steel fibers and PVA fibers can be partly replaced with ${\mathrm{CaCO}}_3$ whiskers, which is very beneficial in decreasing the production cost of fiber-reinforced cementitious composites for large-scale construction project applications.

Alternative sulfur management solutions are of great interest to scientists and engineers due to the increase in the world’s sulfur product. Although use of by-product sulfur as a binder in concrete has been addressed in previous reports, almost no work has been done to investigate the potential use of by-product sulfur as stabilizer agent for soil. This paper presents the geotechnical characteristics of sandy soil form the southern Caspian Sea Coastal Area of Mazandaran State, Iran, stabilized with modified sulfur. Specimens cured up to 180 days and unconfined compression and direct shear tests were performed. Unconfined compression strength and direct shear parameters increased, depending on modified sulfur content and curing period. Empirical relationships are proposed to estimate the unconfined compressive strength and direct shear parameters. Our results showed that a modified sulfur agent has considerable influence on the physical characteristics of soil. Sulfur may be employed as soil stabilizer in civil engineering construction fields.

In this study, the behavior of bituminous mixes made with sewage sludge ash (SSA) as mineral filler was investigated. The behavior of these mixes was evaluated with the Cantabro, indirect tensile strength, water sensitivity, permanent deformation, and resilient modulus tests. The results show that SSA waste may be used in bituminous mixes at approximately 2–3% weight percent, maintaining adequate levels of cohesion and adhesion in the mixtures, which is comparable to mixtures made with active fillers such as hydrated lime and cement. Moreover, its use does not increase permanent deformations. However, the resilient modulus test gave slightly lower results for mixes made with SSA than for mixtures made with other fillers. It may be concluded that SSA waste may be used as a filler for bituminous mixes with better results than for mixes made with limestone fillers and with similar results for mixes made with other fillers such as hydrated lime and cement.

This study investigates the effect of the volume fraction of steel fibers on the axial load response of 200 MPa ultrahigh-strength concrete (UHSC) columns. Behavioral aspects investigated include strength, ductility, and delay and control of brittle concrete cover spalling. In addition, the influence of the amount of transverse reinforcement and the combined effect of transverse reinforcement and steel fibers on the postpeak behavior of the 200 MPa UHSC columns were investigated. Two series of columns, having different amounts of transverse reinforcement, ${\rho }_{sh}=3.6$ and 6.1%, were constructed and tested under pure axial compressive loading. Each series consisted of three columns with three different steel fiber volume fractions ($v_f=0$, 1, and 1.5%). Test results demonstrated that an increase of transverse reinforcement amounts in 200 MPa UHSC columns improves the maximum confined concrete strength and significantly improves the postpeak ductility. The addition of steel fibers resulted in increased peak loads for both the poorly and well confined 200 MPa UHSC columns by delaying and controlling initial cover spalling. The addition of steel fibers improves the confined concrete strength and significantly improves postpeak ductility only for the well confined UHSC columns.

For both environmental and financial reasons, the use of reclaimed asphalt pavements (RAP) needs to be maximized. In this study, rejuvenators and soft asphalt cements were used as recycling agents. Aged binders recovered from field projects were mixed with various percentages of recycling agents to produce asphalt blends. The engineering and chemical properties of the blends were evaluated in the laboratory using binder tests including viscosity, dynamic shear rheometer, gel permeation chromatograph, and Fourier transform infrared spectroscopy. With high RAP contents, the test results indicated that hardened binders may be restored to proper performance characteristics using rejuvenators. The recycling process produces a final blend that is similar to a reference binder in terms of viscoelastic properties. The blends mixed with rejuvenators behaved better under fatigue than those with softening agents. The large molecular size was shown to be a characteristic of an asphalt blend, and may be used as a valuable indicator to design pavement recycling projects. The formation of the carbonyl area in aged asphalt was reduced by adding recycling agents, which changed the physical properties of the blended binder in a predictable manner. A model was developed to detect the content of recycling agents.

The purpose of this study was to determine the ability of high CaO and/or high-alkali (${\mathrm{Na}}_2{\mathrm{O}}_{\mathrm{eq}}$) fly ashes to control alkali-silica reaction (ASR) in mortar bars. The research focused on using an industry standard test method to validate if the chemical index characterization technique common in the literature could be used to accurately predict the replacement levels of investigated fly ashes to mitigate ASR. Results confirmed that low and moderate CaO content fly ashes (with both low and high ${\mathrm{Na}}_2{\mathrm{O}}_{\mathrm{eq}}$ contents) were more effective in mitigating ASR compared to higher CaO and higher ${\mathrm{Na}}_2{\mathrm{O}}_{\mathrm{eq}}$ ashes. A chemical index characterization technique was applied to calculate the required fly ash replacement based on the raw fly ash chemistries and 14-day industry standard results without fly ash (e.g., control). The index was shown to work well for low-CaO and low-alkali ashes; however, adjustments are necessary to use this methodology to predict replacement levels of moderate and high-alkali fly ashes. The industry standard test was shown to be the best method to date to determine the efficacy of high-CaO and/or high-alkali fly ashes. The data presented will also aid in the understanding of how alkali contribution from fly ashes should be considered in the development of new rapid test methods.

The effect of colloidal nanosilica on the fresh and rheological parameters, plastic shrinkage, heat of hydration, and compressive strength of cement-based grouts is investigated in this paper. The fresh and rheological properties were evaluated by the minislump flow, Marsh cone flow time, Lombardi plate cohesion meter, yield value, and plastic viscosity. The key parameters investigated were the dosages of nanosilica and superplasticizer and temperature of mixing water. Statistical models and isoresponse curves were developed to capture the significant trends. The dosage of nanosilica had a significant effect on the results. The increase in the dosage of nanosilica led to increasing the values of flow time, plate cohesion meter, yield stress, plastic viscosity, heat of hydration at 1 day and 3 days, and compressive strength at 1 day, while reducing the minislump, plastic shrinkage up 24 h, and compressive strength at 3, 7, and 28 days. Conversely, the increase in the dosage of superplasticizer led to decreasing the values of flow time, plate cohesion meter, yield stress, plastic viscosity, heat of hydration at 1 day and 3 days, and compressive strength at 1 day, while increasing the minislump, plastic shrinkage, and compressive strength at 3 and 7 days. Increasing the temperature of mixing water led to a notable increase in the results of minislump, flow time, plastic viscosity, heat of hydration at 3 days, and compressive strength at 1 day, while it reduced the plate cohesion, compressive strength at 3, 7, and 28 days. The statistical models developed in this study can facilitate optimizing the mixture proportions of grouts for target performance by reducing the number of trial batches needed.

This paper investigated the stabilization efficacy of alkali-activated ground-granulated blast furnace slag (GGBS) for a marine soft clay, compared with that of portland cement (PC). The influence of activators, including NaOH, ${\mathrm{Na}}_2{\mathrm{CO}}_3$, carbide slag (CS), NaOH-CS, ${\mathrm{Na}}_2{\mathrm{CO}}_3\text{-}\mathrm{CS}$, and ${\mathrm{Na}}_2{\mathrm{SO}}_4\text{-}\mathrm{CS}$, on the stabilization efficacy was investigated. A range of tests were conducted to investigate the properties of stabilized clays, including unconfined compressive strength (UCS), X-ray diffraction (XRD), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP). The results indicated that ${\mathrm{Na}}_2{\mathrm{CO}}_3\text{-}\mathrm{GGBS}$ had no stabilization efficacy for this marine soft clay. NaOH-GGBS-stabilized clay yielded the highest UCS at 7, 28, and 90 days; however, the UCS decreased from 90 to 180 days because of the microcracking. CS-GGBS-stabilized clay had higher 90-day and 180-day UCS than that of PC-stabilized clay, but significantly lower 7-day and 28-day UCS. NaOH, ${\mathrm{Na}}_2{\mathrm{CO}}_3$, and ${\mathrm{Na}}_2{\mathrm{SO}}_4$ could enhance the strength development rate of CS-GGBS-stabilized clay. However, the UCS of NaOH-CS-GGBS and ${\mathrm{Na}}_2{\mathrm{CO}}_3\text{-}\mathrm{CS}\text{-}\mathrm{GGBS}$-stabilized clays decreased from 90 to 180 days as well. ${\mathrm{Na}}_2{\mathrm{SO}}_4\text{-}\mathrm{CS}\text{-}\mathrm{GGBS}$ was found to be the optimum binder for this marine soft clay, yielding at least twice higher UCS than that of PC stabilized clay at any age studied. Considerable ettringite was produced in the ${\mathrm{Na}}_2{\mathrm{SO}}_4\text{-}\mathrm{CS}\text{-}\mathrm{GGBS}$ stabilized clay, which contributed to the enhanced strength.

Curing of asphalt emulsions ensures the proper strength development of the material with the evaporation of water. This paper focuses on determining the minimum curing time needed for Malaysian asphalt emulsions. Three factors, including curing conditions (indoor, outdoor, and curing at night), asphalt emulsion types (RS-1k, RS-2k, RS-2kL, RS-3k, Ralumac, and SRSB) and application rates (high, medium, and low), were investigated. The curing time was determined by weighing a specimen repeatedly at a certain time interval until a constant weight was achieved. Statistical analysis of analysis of variance (ANOVA) was also performed to study if there are differences between groups of variables. From the results, it was found that curing conditions incorporating weather characteristics (i.e., wind speed, temperature, relative humidity, and solar radiation) are the most significant factor affecting the curing time of a particular asphalt emulsion. Curing of asphalt emulsions for construction at night proved to be unworkable due to the absence of solar radiation with relatively low temperature and high relative humidity. On the other hand, a low application rate of asphalt emulsions generally cured faster regardless of the curing conditions and asphalt emulsion types.

The estimation of strength and stiffness of reinforced aggregates is very important for the design and construction of reinforced unpaved/paved road sections. This paper presents the experimental results from static and cyclic triaxial tests carried out on granular subbase samples reinforced with multiple layers of geogrid reinforcement. Aggregates of different size ranges were mixed in calculated proportions by weight to obtain the gradation specified for rural roads. Triaxial samples of 300 mm diameter and 600 mm height were prepared using this sampled aggregate. The strength and stiffness characteristics of this aggregate reinforced with geogrids at different elevations were determined from static and cyclic triaxial tests. Triaxial tests were also carried out on geocell encased aggregates, and the results are compared. From the experimental results it is observed that reinforced systems carried more stresses than unreinforced systems at the same strain level. The beneficial effect increased with increase in the quantity of reinforcement, whereas for geocell reinforcement, the advantage was evident only at higher strains.

The behavior of asphalt mixtures is typically described using linear viscoelastic models at low-strain applications. The time and temperature dependency of asphalt mixture properties is described by forming a master curve that includes three components: time-temperature shift factors, and storage and loss moduli (or compliances). Mathematical models are needed to describe the master curve, which are used in calculating asphalt pavement responses to load and also to compare the overall properties of various mixtures at a wide range of temperatures. This paper proposes a rigorous approach to mathematically describe the master curves using stochastic identification techniques. These techniques have the advantage over current deterministic methods in their ability to account for the uncertainty associated with the constructed models, which could be contributed to variation in the material properties of the asphalt mixture phases as well as their spatial distribution, measurement errors, modeling errors, and inadequate available information. Consequently, uncertainty can be accounted for in the analysis and design of asphalt pavements. The stochastic approach is used successfully in this paper to identify the linear viscoelastic master curve for asphalt mixtures that have been aged to different time durations.

Sintered wollastonite-plagioclase glass ceramics were prepared through crystallization of a parent glass generated by vitrification of pyrolysis residual glass fibers that had been pyrolytically recovered from waste composite materials. A vitrifiable mixture consisting of 95% by weight glass fiber and 5% by weight ${\mathrm{Na}}_2\mathrm{O}$ was melted at 1,450°C to obtain a glass frit. The glass-ceramic materials were produced by a sinter-crystallization process from the powdered glass frit. The effect of firing temperature on the properties of sintered-glass ceramics was investigated. The sintering behavior of glass-ceramic tiles was evaluated by means of water absorption, apparent porosity, and bulk density. In addition, the mineralogical and microstructural characterization of these tiles was carried out using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results from experiments such as water absorption, bending strength, chemical resistance, and stain resistance have shown that the developed glass-ceramic materials possess technological properties very suitable for architectural applications.

A study was conducted to evaluate the effect of coefficient of thermal expansion (CTE) test procedures and length-change measuring devices on the measured CTE values. Twenty different coarse aggregate sources were tested using the Texas Department of Transportation (TxDOT) and the American Association of State Highway and Transportation Officials (AASHTO) suggested CTE methods. Two different types of length-change measuring devices, linear variable differential transformers (LVDTs) and differential variable reluctance transducers (DVRTs), were used. No significant effects of length-change measuring devices were observed on the CTE values measured by the TxDOT method. However, the test methods have shown effects on the measured values. The TxDOT method yields higher CTE values than the AASHTO method. Data obtained in this study confirmed that the internal water pressure development during the heating and cooling cycles is one of the potential reasons. Internal water pressure can significantly affect the CTE of concrete. Further investigation is needed to determine the effect of internal water pressure on the CTE, which affects the design and service life of concrete pavements.

A systematic framework is proposed to quantify hybrid uncertainties (i.e., aleatory and epistemic uncertainty) for the probabilistic prediction of corrosion damage in aging reinforced concrete (RC) bridges when the initial statistical parameters of variable are not available, sparse or cannot be accurately obtained. The key idea is to use a likelihood-based approach to calculate the probability distribution function (PDF) of the variable described by sparse data and an entropy-based transformation method to obtain the PDF of variable described by expert-based information. Following this, a hybrid description of uncertainties is proposed using the marginal integration. The uncertainty quantification of important factors on corrosion initiation and propagation are discussed, and a time-variant corrosion cracking model is developed. The proposed methodology is illustrated and demonstrated by a numerical example of corrosion damage prediction of an existing RC bridge. The prediction results of corrosion damage agree well with the experimental observations.

A reliable method for determining the dynamic material characteristics of hot-mix asphalt using a Bayesian method based on Latin hypercube sampling, impact resonance testing (IRT), and the shift factor of linear viscoelastic (LVE) asphalt concrete specimens is reported. Discrete resonance moduli data were obtained from the IRT at temperatures of 5, 25, 40, and 50°C. The shift factor of the LVE was used to translate the discrete points of resonance moduli to higher or lower frequencies, depending on the temperature of the specimen. Based on the temperature–frequency combinations, Bayesian statistical predictions were used to create a dynamic modulus master-curve representation, using the resonance moduli data and Latin hypercube sampling. The results for three different hot-mix asphalt mixtures were in good agreement with dynamic moduli data obtained using other testing methods.

Asphalt binder resistance to permanent deformation at intermediate temperature significantly affects overall pavement resistance to rutting. To enhance asphalt resistance to permanent deformation, researchers have used various modifiers and additives such as styrene butadiene styrene (SBS) block copolymer, ethylene vinyl acetate (EVA), polyvinyl acetate (PVA), styrene butadiene rubber (SBR), and natural rubber latex. In this paper, the effectiveness of modification of asphalt binder by styrene-ethylene/propylene-styrene (SEPS) in order to enhance asphalt binder’s resistance to permanent deformation has been investigated using two different evaluation methods: the Superpave specification parameter, $G^{*}/\sin \delta$, and the cross model for calculating zero shear viscosity (ZSV). The experiments were conducted using dynamic shear rheometer (DSR) frequency sweep test performed on both the neat sample and modified ones at 40, 50, and 60°C. Utilizing these two approaches, rutting resistance of modified asphalt binders are determined and then normalized using the rutting resistance of the neat asphalt binder as the control data in order to calculate the rutting resistance improvement ratio. The research results showed that regardless of the evaluation method, SEPS can significantly improve anti-rutting performance of asphalt binder. However, it was found that ranking of modified asphalt binders according to the two approaches is different.

The present study examines the mechanical behavior and corrosion resistance in dual phase B500c reinforced steel used in concrete structures, before and after applying a layer of aluminum coating in intense corrosion environment. The aluminum layer was applied on the steel bars via thermal process with a flame spray gun and an average layer of 100 μm was created. The 90-day exposure corrosion tests performed in laboratory salt spray environment resulted in 0.29% mass loss of the specimen with aluminum coating while the noncoated specimen (bare) presented a mass loss of 13.5%. Similarly, the mechanical properties in tensile testing remained stable in all cases during different exposure times in contrast to bare specimens in which the strength properties followed mass loss ratio reduction while a dramatic reduction in ductility properties was also noticed. Roughness measurements were also performed in the reinforced steel, either with aluminum coating or without aluminum coating. The effects on friction coefficient and the wear rate were estimated using the weighting method, and the relevant results are presented.

Phase-change composites for energy storage were prepared by the expanded graphite (EG) absorption method and their microstructures were analyzed. The organic phase-change materials (PCMs) were evaluated for their thermal and latent heat storage properties. The expanded graphite was prepared under the microwave irradiation. The scanning electron microscope (SEM) and mercury intrusion porosimetry analyses showed that expanded graphite had micron-size pores. The EG was able to easily absorb organic PCMs because of its nonpolarity and porosity. Composite PCMs for energy storage were fabricated with paraffin and the expanded graphite. The resulting material showed superior heat storage (releasing) effects and reduced large-range fluctuation in environmental temperature, thus achieving energy transfer simultaneously across different times and space.

The objective of this study is to characterize the rheological properties and aging mechanism of asphalt binders blended with high percentages of biobinders using Fourier transform infrared spectroscopy (FTIR). The petroleum asphalt was partially replaced by the biobinders at fractions of 30 and 70% by weight. Rotational viscometer (RV) and dynamic shear rheometer (DSR) tests were conducted for the rheological properties, and the rolling thin film oven (RTFO) test was conducted for the aging simulation. Loss of volatiles was obtained from the RTFO test, whereas the oxidation characterization was investigated through the FTIR test. The rheology results showed that the bioblended asphalt binder exhibit different rheological properties as compared with the control asphalt binder before and after the RTFO-aging. The mass loss test showed that the loss of volatiles of biobinders were much higher than the control asphalt binder. FTIR spectra analysis showed that additional $\mathrm{C}═\mathrm{C}$, $\mathrm{C}─\mathrm{O}$, $\mathrm{C}═\mathrm{O}$ and OH bonds were generated during the aging. Further chemical analysis revealed that the aging of biobinder originates from three aspects: the loss of volatiles, the dehydrogenation which formulates higher molecular weight compounds such as asphaltene, and the oxidation which resulted in chemicals such as acids, alcohol, and ester.