Journal of Materials in Civil Engineering

The time-dependent deformation and long-term strength of rock mass are generally controlled by the mechanical properties of discontinuity, in particular, creep properties. By using the samples based on various JRC values, a series of shear tests and shear creep tests were carried out. The mechanical properties of discontinuity under shear stress were investigated. The creep properties under shearing condition were analyzed. Results showed that both the sliding and cutting behavior can be observed during the shear tests. The sliding effect and cutting effect can obviously change the shear strength parameters. The transient and steady creep appeared in shear creep tests, but accelerating creep was not observed. The long-term strength can be identified by using the variation of creep rate and the transition of different creep stages. The long-term strength is approximately 60–70% of the conventional shear strength.

Supplementary cementitious materials (SCMs) have been successfully employed in binary or ternary cement blends to mitigate alkali-silica reaction (ASR). The determination of composition of binary or ternary composite cement to avoid deleterious expansion of concrete is usually based on a wide range of experiments, and it is time-consuming and costly. This paper introduces a factorial design method, combined with a ternary contour diagram, to correlate the compositions of ternary composite cements with ASR expansions with only seven batches of experiments. Based on the ternary contours, a safe composition range and dangerous composition range can be obtained. Moreover, the ternary contour diagram can also be used to analyze synergetic effects between any two components in the ternary composite cements. Finally, the efficiency of the factorial design method was verified by comparing the experimental and predicted expansions, and the results correlated very well.

This work reports the laboratory performance of five film-forming sealers that protect concrete from deicer scaling (15 freeze-thaw and wet-dry cycles in diluted NaCl or ${\mathrm{MgCl}}_2$ solution). Regardless of the presence or type of sealer, no apparent scaling occurred on the concretes exposed to 2.54% by weight ${\mathrm{MgCl}}_2$ solution, but there was significant reduction in their splitting tensile strength (up to 55% for the nontreated concrete). The best-performing sealer in mitigating this risk of strength reduction was the methyl methacrylate (MMA) polymer. For the concrete exposed to 3% by weight NaCl solution, the scaling resistance and ability of strength preservation were significantly improved by the presence of a sealer. Regardless of the sealer type, the initial rate of water absorption of surface-treated concretes was greatly reduced by the sealer by at least 68%. The water absorption behavior of the sealer-treated concrete showed a strong correlation with mass loss caused by salt scaling. The concrete samples treated by the epoxy sealer featured the lowest initial gas permeability coefficient and the lowest water absorption rates, attributable to the formation of a highly impermeable and hydrophobic surface layer. The surface scanning electron microscope (SEM) micrographs of sealer-treated concrete reveal the importance of the integrity of hardened sealer film in upholding the concrete’s resistance to the transport of waterborne and gaseous phases and the attack by chloride deicers and freeze-thaw cycles.

Routine mechanical characterization of asphalt concrete is performed under small-strain levels with on-specimen linear variable displacement transducers (LVDTs) as deformation measuring devices. An optical LVDT was conceptually proposed and evaluated in this study to serve as a viable noncontact alternative to physical LVDTs. The envisioned device consists of a pair of low-end low-resolution grayscale cameras, each monitoring a virtual gauge point, i.e., a small untreated surface area of the tested specimen. The gauge length is the distance between the two virtual gauge points, and the sought-after information is their differential in-plane translation. Digital image correlation techniques were employed for the measurement, operated on the natural material texture without requiring speckle coating. As a first step toward evaluating the concept, the study explored both the precision and the accuracy that may be achieved with one low-resolution image sensor. A calibration scheme was also offered for introducing object-scale dimensions into the analysis. From this predevelopment study it is concluded that the envisioned optical LVDT is viable, rendering the idea worthy of consideration.

The use of recycled concrete aggregate (RCA) materials in highway constructions is economically viable and reduces virgin natural resource demands on the environment. To evaluate their potential use in highway construction, two different RCA materials and four virgin granular aggregate base (GAB) materials and their select mixtures were tested in the laboratory for strength, resilient modulus, permanent deformation, and durability. Laboratory water leach tests and pH-dependent leaching tests were conducted to determine the environmental suitability of the RCA materials. The leaching behavior of Ca, Cr, Cu, Fe, and Zn and the effects of pH, curing time, liquid-to-solid ($\mathrm{L}:\mathrm{S}$) ratio, and particle size on metal leaching from the RCAs were investigated. Summary resilient moduli (${\mathrm{SM}}_R$) of the RCAs were up to 2.6 times higher than that of the GAB materials. Their stiffness also increased when subjected to freezing and thawing cycles. Consistent trends could not be observed with percent RCA addition and strength or ${\mathrm{SM}}_R$; however, the RCAs generally yielded higher permanent deformations compared with the GABs. Prolonged curing caused rehydration of cement particles and, in general, yielded a decrease in pH and leached metal concentrations. Increasing the $\mathrm{L}:\mathrm{S}$ ratio decreased leaching of elements significantly because of the dilution of leached elements in the aqueous solutions. pH excursions yielded cationic leaching patterns for Ca and amphoteric leaching patterns for Cr, Cu, Zn, and Fe.

The use of recycled steel fibers from waste tires as reinforcement in concrete matrix appears to be a promising solution, thanks to the performance of the material in terms of toughness and postcracking behavior. The main objective of this paper is to analyze the bond behavior of recycled steel fiber–reinforced concrete (RSFRC) and steel bars, and compare the results with those of industrial steel fiber–reinforced concrete (ISFRC). The paper focuses on the characterization of the mechanical properties of concrete reinforced with short steel fibers from waste tires and on the results of pull-out tests executed both on RSFRC and ISFRC. The experimental results, in terms of failure mode, maximum bond stress, and bond stress versus slip behavior are analyzed and discussed. Finally, a theoretical analysis of the bond-slip behavior was performed. The experimental results show that most of the known performance of the ISFRC can be extended to RSFRC. Referring to the bond performance, an improved behavior of RSFRC with respect to ISFRC in terms of bond-slip law was observed.

Strain-hardening cement-based composites (SHCC) with polyvinyl alcohol (PVA) fibers have excellent tensile and bending behaviors; however, their water and aggressive ion penetrations should be considered carefully under applied load conditions because they can significantly influence the durability of SHCC. The goal of this study is to evaluate the effect of applied loads on water and chloride penetrations of SHCC. The capillary absorption test was respectively carried out under loading and after unloading, and then the water and chloride penetrations were evaluated. The results show that applied loads have a significant effect on penetrations, and the penetrations prove to rise with the increase of applied loads. Particularly, when a higher load is applied, water and chloride rapidly penetrate into SHCC. However, SHCC-W whose surface is processed with waterproofing agent, exhibits good penetration resistance. Due to the shrinkage stress induced by fibers in SHCC, the crack widths of SHCC after unloading are lower than those under loading, and the penetrations are thus supposed to decrease. The relationship between the applied load and water penetration of SHCC is established, which can be used for evaluating the durability of SHCC when considering the applied loading conditions.

Drying of concrete is a major reason for concrete shrinkage, which significantly influences cracking and durability of concrete structures. Therefore a pilot test was executed in which progressive drying of concrete was measured at different depths under the concrete surface exposed to environmental conditions. Pore relative humidity distribution throughout a cross section (in depths from 3 to 10 cm) of concrete specimens was measured experimentally over the time range of 10 months. Then a moisture diffusion process is formulated mathematically and solved using recent models for moisture diffusivity and moisture capacity, and taking its nonlinearity into account. Numerical modeling is carried out using finite elements implemented into advanced numerical algorithm. Simplified analysis is also provided. Measured and calculated values are compared and moisture diffusivity is calibrated to the experimental results. Comparisons between measured and calculated values have pointed to the complexity of the drying process as well as the incapability of the used models to predict drying of concrete with the desired precision. This experiment is a pilot test of an experimental program and verifies the feasibility of humidity measurements.

The aim of this paper is to study the impact of certain soil treatments on the internal erosion characteristics of treated compacted silt. The experiments measured the internal erosion using the hole erosion test (HET). This study aims to describe the effects of clay, lime and cement soil treatments on the internal erosion, specifically with regard to the amount of treatment used and the curing time. A new enhanced HET was developed to apply a high inlet pressure up to 650 kPa and thus generate a hydraulic shear stress up to 10,000 Pa. The internal erosion resistance was quantified by the coefficient of soil erosion and the critical shear stress. The results demonstrated that clay treatment could reduce the coefficient of soil erosion depending on the nature and percentage of clay added to the soil. The results also showed that lime and cement treatment primarily increased the critical shear stress of the tested silt. This increase was higher with cement treatment and was dependent on the amount of the added product. The impact of the curing time (up to 30 days) on the evolution of the erosion characteristics was not relevant for the lime-treated silt, whereas that of the cement-treated silt was dependent on the amount of cement added to the soil.

Graphene oxide (GO) is a newly invented material with extraordinary properties. This paper presents the effect of graphene oxide addition on freeze–thaw resistance in hardened cement. GO is incorporated in the cementitious matrix in ratios of 0.01, 0.03, and 0.06% by weight of cement. Freeze–thaw cycle tests show a weight loss of approximately 0.8% after 540 cycles in the control mix compared to approximately 0.25% in 0.06% GO mix. Several tests were conducted to investigate the reasons behind this result. The tests included nitrogen and water adsorption, air content, and compressive strength. The results showed that GO mixes have finer pore structure than the control mix. Moreover, the results indicated that GO addition increases air content in the mix and shows high compressive strength compared to the control mix. The enhancement of freeze–thaw resistance due to GO addition can be because of the modification of pore structure where water hardly freezes in small pores. Also, the resistance of nanocracks propagations can limit the development of frost damages, in addition to the entraining air in the mix by GO addition that creates room to release osmotic pressure.

Strain-hardening material properties of cementitious composites have been achieved by the hybridization of fibers in the matrix. The modulus of elasticity of thin ferrocement composites depends on the elastic modulus of the cement mortar and some factors pertaining to the difference in the elastic modulus of the mesh and mortar. This study presents an experimental and analytical investigation aimed at determining the modulus of elasticity of hybrid polyvinyl alcohol (PVA) ferrocement (HFF). The study had two stages: the first was to determine the elastic modulus of hybrid fiber cementitious (HFC) composites, and the second was to determine the elastic modulus of HFF panels based on flexural tests. An analytical calculation was conducted using the data obtained from a standard compression test, nanoindentation test, and finite element (FE) analysis. The nanoindentation of a representative volume element (RVE) and the transversely isotropic material behavior using FE modeling of an RVE were compared and evaluated. The calculated composite elastic modulus is in good agreement with the elastic modulus obtained from the flexural tests and the FE-model.

Green building practices have created an opportunity for the forest products industry to become a leader in the creation of innovative building products derived from renewable materials. In other industries, sandwich composites have proven to be efficient structures by meeting structural demands of traditional panel products while consuming less material. A prototype molded-core sandwich panel made of span-rated oriented strand board (OSB) facings and a bidirectional molded wood-strand core was produced. Critical mechanical properties were evaluated to determine the feasibility of this product for use in building applications. The goals of this study were to generate details on structural performance of the product, validate the design, and provide suggestions for future product development. Results indicate that this molded-core panel performs particularly well in flexure while connection properties had the largest scope for improvement. Sufficient performance was observed to validate the design, warranting production and testing of panels sized for end-use. Future product development should explore different connection systems, perform detailed engineering analyses of the mechanical properties necessary for complete structural design, and characterize physical properties of the panel.

This study investigates the engineering and durability properties of self-consolidating concrete (SCC) specimens that were produced using various types of foamed lightweight aggregate (FLWA). Further, the effects of FLWA on the engineering and durability properties of SCC are assessed on the basis of related international standards. All of the fresh SCC mixtures exhibited exceptional flowability with uniform composition. The use of surface-treated FLWA improved significantly the compressive strength and the dynamic elastic modulus of SCC and reduced the drying shrinkage at later ages. The lowest thermal conductivity of $0.79\mathrm{W}/\mathrm{mK}$ was achieved for SCC incorporating 80% fly ash (FA) and 20% ground blast furnace slag (GBFS) aggregate that produced with a foaming agent concentration of 7%. Furthermore, the electrical resistivity and the ultrasonic pulse velocity values for all of the 28-day specimens exceeded 20 kΩ-cm and $\mathrm{3,660}\mathrm{m}/\mathrm{s}$, respectively, satisfying the minimum requirements of the referenced concrete durability indices. Finally, the 91-day passing charges for all specimens ranged between 1,500 and 566 C, indicating either low or very low chloride permeability.

Low-temperature cracking is a severe distress for asphalt pavement built in cold regions. When a steep drop in temperature is experienced, thermal stress develops in the different pavement layers and, as a critical temperature value is reached, cracking occurs. Hence, thermal stress represents a relevant parameter for predicting the low-temperature performance of asphalt pavements. Conventionally, thermal stress is calculated by converting the experimental results of creep compliance to a relaxation modulus and then by numerically solving the convolution integral. Hopkins and Hamming’s algorithm is commonly used for this purpose in many research efforts. In this paper, the use of Laplace transformation is evaluated as an alternative approach since, by using this method, thermal stress and critical temperature can be directly and easily derived without relying on a traditional two-step computation process. The results obtained from Hopkins and Hamming’s solution and from the Laplace transformation are then graphically and statistically compared. It is found that the approach based on Laplace transformation provides reliable and reasonably close results to those obtained from the more complex Hopkins and Hamming’s method.

Aiming to solve the problems caused by the construction and demolition waste and the depletion of natural aggregates, in the present study, both the coarse recycled aggregates and the fine recycled aggregates are used to produce new green concrete with a fly ash–based geopolymer. The mechanical study shows that the reduction rates of the compressive strength, Young’s modulus, and the Poisson’s ratio of the geopolymeric recycled aggregate concrete (GRAC) specimens increase with the increase of the water/cement (w/c) ratio. The Young’s modulus is much more vulnerable to the increase of the w/c ratio than the compressive strength. These significant changes to the GRAC samples could be attributable to the deteriorated properties rendered to the geopolymer by the increase of the w/c ratio. When the minimum ratio of w/c is applied, the fly ash–based geopolymer renders better mechanical properties to the concrete specimens than the ordinary portland cement. With the aid of scanning electron microscopy and nanoindentation, there is no interfacial transition zone well developed between the old cement paste and the new geopolymer/cement paste.

Low-temperature cracking in pavement is a common distress in cold regions especially in North America; such distresses are shown to be highly related to binder low-temperature properties. To reduce the low-temperature cracking, several state departments of transportation are requiring the use of polymer-modified asphalt. However, polymer modification tends to be costly and in some cases led to phase separation in asphalt. Therefore, the current paper implements a fractional viscoelastic approach to study the effectiveness of several bio-based modifiers on improving asphalt binder’s low-temperature characteristics. As such, implementing the bending beam rheometer (BBR) test, low-temperature rheological characteristics of asphalt binders, which are modified by four different bio-oils including biobinder from swine manure, corn stover, wood pellet, and miscanthus pellet are investigated. For this purpose, the BBR test was performed on asphalt binder samples containing 10% modifier at three temperatures of $-12$, $-18$, and $-24°\mathrm{C}$. In order to analyze results of the BBR test, a fractional viscoelastic model is used to describe the relation of creep compliance and time. Utilizing the simple fractional model, relaxation modulus, storage modulus, and loss modulus are derived. In addition to the Superpave performance grading (PG) protocol, parameters of the simple fractional viscoelastic model are used to evaluate the performance of asphalt binders at low service temperatures through damping ratio and dissipated energy ratio. While biobinder from swine manure has the best performance by Superpave PG protocol analysis, corn stover shows the highest values for damping ratio and dissipated energy ratio among all modified asphalt samples.

A preventive maintenance strategy of spraying rejuvenators on asphalt pavement surfaces is being considered as a cost-effective and environmentally sustainable option to extend the service life of existing asphalt concrete pavements. Rejuvenators might penetrate into the asphalt concrete and soften (rejuvenate) the bituminous binder. In this paper, the rejuvenation effectiveness of two rejuvenators on an artificially aged mortar is assessed. Cylindrical mortar specimens were prepared from the artificially aged mortar and then treated by the rejuvenators. The rheological and shear fatigue properties of the reference and treated mortar specimens were measured using dynamic shear tests. Meantime, a three-dimensional column model was created to investigate the dynamic shear test’s capability of detecting the rheological properties of a composite column with a soft material in its outer part and a stiff material in its inner part. From finite-element modeling, it is found that the shear modulus of the composite column is higher than that of the soft material and lower than that of the stiff material. However, the results of the dynamic shear tests show that the two rejuvenators did not decrease the complex shear modulus of the artificially aged mortar. In addition, the two rejuvenators did not change the shear fatigue life of the artificially aged mortar.

High-strength low-alloy (HSLA) weathering steels are the conventional material used for nonredundant fracture-critical members in bridge construction. Guidelines from state departments of transportation (DOTs) prevent material suppliers from scribing marks which remain on the surface of fracture-critical members when in service due to the possibility of degrading mechanical properties. Currently, any automated scribe marking, namely mechanical milling, is either cut from the end of the part, or welded over, thereby effectively removing it before service. All other markings are either manually die-stamped, or spray-painted on, which can be accidentally removed during sand blasting or shipping. Safe automated methods of scribing fracture-critical members are needed such that markings will remain throughout the production process but will not compromise the integrity over the lifetime of the part. In this study, a microstructural evaluation of 50W (or 345W) weathering steel was conducted to characterize the effect of plasma markings on microstructure and mechanical properties. S-N curves generated through fatigue testing showed no measurable difference in fatigue life between marked and unmarked material.

High-strength fabrics are ideal materials for use in structural and aerospace systems where high-performance and lightweight structures are demanded. Mechanical characterization of this class of materials under dynamic loading is of great importance considering extreme conditions such as explosion, impact, and ballistic loading. The strain-rate effect on the tensile behaviors of unidirectional glass, basalt, carbon, and plain-woven aramid fabrics were evaluated under various strain rates (25, 50, and $100{\mathrm{s}}^{-1}$) using a servohydraulic high-rate testing system. The stress-strain responses and failure modes of these fabrics at the investigated strain rates were studied. Quasi-static tests were also performed as a comparison. The results showed that as the strain rate increased from 25 to $100{\mathrm{s}}^{-1}$, the average tensile strength of basalt, carbon, glass, and aramid fabrics increased from 1,095 to 1,743, 1,516 to 1,974, 1,072 to 1,462, and 1,530 to 1,897 MPa, respectively. Toughness and maximum strain were also found to be increased. The significance of strain-rate effect on the material properties of different fabrics was statistically tested using ANOVA. The $P$-values of tensile strength, toughness, maximum strain, and Young’s modulus of all materials were less than 0.05, except for the maximum strain of basalt ($P$-value of 0.3134) and the toughness ($P$-value of 0.1832) and Young’s modulus ($P$-value of 0.0662) of aramid.

Plastic shrinkage cracking in restrained cement pastes reinforced with wollastonite particles of micro and submicron sizes was studied using a quantitative two-dimensional (2D) cracking experiment. A series of blended paste mixes with portland cement and different grades of wollastonite fibers were developed and tested under low vacuum conditions. Testing parameters included four grades of wollastonite with aspect ratio in the range of $3:1–20:1$ and average particle size ranging from 33 to 2,000 μm at 15% cement replacement. Wollastonite beneficially altered the shrinkage cracking morphology by arresting crack growth, wherein crack lengths and widths were reduced by a factor of two, and the area by a factor of three when compared with the control specimens. However, the initial evaporation rate, early age diffusivity, and cumulative moisture loss increased. Influence of the microfibers in controlling early age drying were related to the porosity of the microstructure using mercury intrusion porosimetry (MIP).

This paper investigates the influence of the presence of a joint (vertically or horizontally oriented) on the hydromechanical behavior of sandstone under undrained triaxial conditions. A series of undrained triaxial experiments was performed on intact and horizontally and vertically jointed sandstone samples under different confining pressures and initial pore-water pressures. Joints in jointed samples were artificially created with rough and irregular surface profiles. An increase in pore-water pressure with increasing deviatoric stress was observed for all tests. Maximum induced pore-water pressure values were higher and occurred later in the jointed rock samples when compared to the intact samples at all confining pressures. This may be related to the efficiency of the response of the joint pore volume to loading when compared to that of the matrix pore volume. Moreover, the significance of new pore volume creation (by microcracking during failure) on sample pore-water pressure is dependent on the initial pore volume, which itself varies with the presence and size of joints regardless of orientation. Effective peak deviatoric stresses observed from the tests were consistently higher for the intact rock samples when compared to the jointed rock. This result suggests that the compressive strengths of intact and horizontally and vertically jointed rocks are not comparable when the joint is rough and the deformation is undrained. The origin of the influence of horizontal or vertical joints on rock strength may relate to the presence of edges on the rough joints, which act as stress intensification points and allow material failure under lower applied stress for the jointed samples than for the intact (homogeneous) samples.

In order to investigate the fracture performance of lightweight epoxy asphalt concrete (LEAC) used in steel bridge deck pavement, experiments and numerical simulations were used to analyze the effect of lightweight aggregate (LWA) on fracture behavior of LEAC. The gradations of LEAC with different LWA contents were determined by the Marshall method, indirect tensile test with and without freeze-thaw processing were used to measure the indirect tensile strength and moisture stability of LEAC, and fracture properties were evaluated by three-point bending beam test at 15°C and $-10°\mathrm{C}$. Also, internal structures of LEAC were scanned by X-ray CT device to develop three-dimensional finite element models (3D-FEM), and mechanical states of basalt aggregate, LWA, and epoxy asphalt mastic (EAM) were also studied. The results show that the LWA has an obvious influence on fracture properties of LEAC; LWA content 5% can significantly improve the fracture performance. EAM is the main bearing structure of LEAC; minimizing the impact on EAM can enhance the structural strength of LEAC. The mechanical state of internal structure can be calculated by 3D-FEM effectively, and the simulation results illustrate that the effect of LWA on stress distribution of EAM is obvious.

The presence of a superplasticizer can significantly impact the apparent viscosity of cementitious material. However, its working mechanism remains controversial. In this paper, the effect of different polycarboxylate-based superplasticizers (SPs) on the viscosity of low water-binder ratio cementitious materials was characterized by V-funnel efflux time and rheological parameters. The results show that superplasticizer based on the copolymerization of acrylic acid and polyethylene glycol monoallyl ether shows a better performance compared to the two other types of SPs according to the V-funnel efflux time and apparent viscosity of cementitious materials. Furthermore, it is found that, for a same slump flow value, the apparent viscosity of mortars with different SPs is related to the water film thickness of cement particles, and more closely to the viscosity of aqueous solutions containing unabsorbed SPs.

The fatigue characteristics of a lightly stabilized granular material under traffic loading are important considerations for the design of a pavement containing such material. This paper examines the use of flexural testing with on-sample midspan deflection measurement for determining fatigue characteristics of lightly stabilized granular base materials. The experimental program included cyclic load flexural testing to determine the stiffness modulus, fatigue life, and damage characteristics of a granular material stabilized lightly with 1–3% cement–fly ash and to establish relationships for predicting the fatigue life. Fatigue life was estimated using the energy ratio approach and compared with the number of load cycles required to break the specimen. Empirical relationships are proposed to relate the fatigue life with tensile strain and stress ratio similar to those proposed in the literature. Progressive damage due to fatigue and permanent deformation accumulation with increases in the load cycles is also presented in this study.

Interfacial adhesive bonding of concrete-like materials is strengthened by short Kevlar fibers. The tough and flexible Kevlar fibers, bridging across grain structures, can effectively suppress premature surface and subsurface local fracture at the interface during the formation of fictitious crack. The adhesive joint, formed through either repairing of a gap using epoxy or structural reinforcement using carbon-fibers/epoxy composite, is changed into a composite adhesive joint because of use of Kevlar fibers at the interface. In this study, grey granite samples were tested under three-point-bending with two different interfacial repair conditions: (1) epoxy only, and (2) epoxy with short Kevlar fibers of 6 mm in length. Peak loads and RILEM fracture energy $G_f$ were measured from as-received granite samples, and the two different types of repaired samples. Improvements were observed in both the peak load and fracture energy. Formation of fictitious crack and its influence on the peak load were discussed.