Journal of Materials in Civil Engineering

Because of its lower mechanical properties and durability compared to normal concrete, pervious concrete demands better quality control and greater inspection efforts to remain functional. Nondestructive tests (NDTs), ultrasonic pulse velocity (UPV) in particular, were used to increase the effectiveness of the quality assurance of pervious pavements. Predictive models for hydraulic conductivity (main feature) and compressive strength (main concern) of pervious specimens were derived using only UPV combined with total void ratio. The results confirm that UPV offers a technique for rapid assessment of in-place properties of pervious concrete, either to supplement or replace core testing in some cases. Combined use of UPV and void ratio was found to outperform the models based on a single test result. Based on the obtained results, statistical models were put forward for predictions of pervious concrete’s hydraulic conductivity and compressive strength.

The semicircular bend (SCB) test has received much attention in recent years. The test is quick, indicative, and has reasonable variability compared with other fracture property tests for asphalt concrete (AC) mixtures. The crack propagation in the test is calculated indirectly using the crosshead movement (CHM) or crack mouth opening (CMO). Although these methods might correlate well to the crack propagation, little research has been done to ascertain this relationship. The main objective of this study is to compare the SCB test using a noncontact camera (NCC) and CHM. A comprehensive comparison of fracture properties of six AC mixtures captured by these two methods is conducted. The critical strain energy ($J_c$) and ($K_{\mathit{1}c}$) values for AC mixtures are determined. There is a strong correlation between $J_c$ from SCB NCC and $J_c$ from SCB CHM, and between $K_{\mathit{1}c}$ from SCB NCC and $K_{\mathit{1}c}$ from SCB CHM. The results of this study indicate that the SCB CHM test has great potential as a quality assurance/quality control (QA/QC) test of fracture properties of asphalt mixtures.

This paper aims to develop measures to minimize the early-age fatigue damage of prematurely opened cement-treated bases (CTBs) due to repetitive heavy traffic loading. The four-point bending test was used in this study to characterize the early-age fatigue performance as well as the flexural properties of two different locally sourced granular materials stabilized with 3% general purpose (GP) cement. All the flexural tests were executed under stress-controlled mode. The fatigue test results evinced the existence of an endurance limit in cemented granular materials (CGMs) even at 7 days curing age. A stress-based fatigue performance model was developed for predicting the early-age fatigue performance of CGMs in service. In addition, the 7-day fatigue test data from this study were validated using existing CGM fatigue models. The numerical results obtained from the CIRCLY program indicated that the level of interaction between the axles of an axle configuration decreases with decreasing CTB layer thickness, resulting in increased pavement fatigue damage. It was also found that the asphalt cover over CTB required to prevent the occurrence of initial fatigue damage to the CTB decreases with increasing CTB modulus, subgrade strength, and CTB layer thickness. The limitations and simplifications in current pavement design and testing methods are also critically discussed and addressed on the basis of the results of this study.

A new and innovative binder KMP is developed for solidification/stabilization (S/S) of soils contaminated with heavy metals such as lead (Pb), zinc (Zn), and cadmium (Cd). The KMP consists of acid-activated phosphate rock, monopotassium phosphate, and reactive magnesia. However, effectiveness and immobilization mechanisms of KMP in actual field contaminated soils have not been investigated. This study presents a systematic investigation of strength, leachability, and microstructural properties of KMP stabilized field clayey soil that has been contaminated with Pb, Zn, and Cd at a smelter site. Several series of laboratory tests are conducted that include unconfined compression tests (UCT), toxicity characteristics leaching procedure (TCLP), modified European Communities Bureau of Reference (BCR) sequential extraction procedure, mercury intrusion porosimetry (MIP), X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive spectroscopy (EDS) studies. The TCLP and UCT results show that the leached Pb, Zn, and Cd concentrations decrease while unconfined compressive strength and dry density of the stabilized soil increase with increasing binder content and curing time. The sequential extraction results indicate that large percentages of Pb, Zn, and Cd are transferred from the exchangeable fraction to residual fraction after the KMP stabilization. The pore-size distribution reveals that the mean diameters and volumes of interaggregate and intra-aggregate pores decrease with an increase in the KMP content. The XRD and SEM/EDS analyses demonstrate the formation of magnesium phosphate-based products and heavy metal phosphate-based products in the stabilized soil, and they are the primary mechanisms for strength increase and heavy metal immobilization, respectively.

This study presents the residual capacity and post-event damage assessment of unconfined and glass-fiber reinforced polymer (GFRP)-wrapped confined concrete cylinders subjected to low-cycle fatigue loading. First characterized were monotonic compressive behaviors, including post-peak, strain-softening, and strain-hardening responses. Fatigue tests were then carried out at three stress levels to determine the number of cycles to failure, material degradation regarding the development of total and plastic strain, the deterioration of elastic modulus, and also the change in the temperature of test specimens. To assess the residual capacity of damaged concrete, the specimens were subjected to 0.3, 0.5, 0.7, and 0.9 of the fatigue life, and then monotonically reloaded to failure. After comparing the stress–strain curves of damaged and intact concrete, the remaining compressive strength and strain capacities were determined. Subsequently, permeability tests were conducted on concrete disks taken from damaged specimens, allowing the degradation process to be indirectly quantified using damage occurring in the concrete microstructure.

A moment tensor analysis of acoustic emission was applied to quantitatively study the microcracking mechanism and damage evolution process in cylindrical specimens of granite and sandstone under diametral compression. It was found that the localized damage zone tended to originate and propagate from the vicinity of the loading ends. During the damage accumulation process, the tensile cracks played a dominant role in number, but the acoustic emission (AE) energy release of microcracks of different types presented an inconsistent trend for the two types of rock. Scanning electron microscope (SEM) observations on the fractured surfaces were conducted, which indicated that during the rock failure process there coexisted microcracks of three types—tensile, shear, and mixed-mode—due to the heterogeneity of the mechanical properties of the rock. The microscopic observations using a polarized light microscope technique revealed that the mineralogical composition and microstructure of rock had a significant effect on its microcracking mechanism.

A grading curve is an important measure for illustrating the grain size distribution of granular materials. In general, there exists a statistical fractal relationship between the cumulative number of particles and the grain size for granular materials in nature. The objective of this paper is to calculate fractal dimensions for different types of grading curves of granular materials. The common grading curves are classified into four categories: concave, convex, combinational, and gapped. The formulas of the concave and convex grading curves are derived from the same statistical fractal relation. The fractal dimensions can then be obtained from the known grading curves by a linear fitting approach. For combinational and gapped grading curves, two different fractal dimensions are used to describe the fine and coarse grain parts. In addition, a criterion to determine the optimal demarcation point of a combinational grading curve is suggested. All types of grading curves of common granular materials in civil engineering are considered in this study. Their statistical fractal dimension can be used to study the physical and mechanical properties of materials containing granular ingredients to facilitate the consideration of the complexity of grain distribution.

Alkali-activated binders (AABs) are a material obtained from the combination of a solid precursor and an alkaline activating solution. In this study, one solid precursor used was blast-furnace slag (BFS) and the other was an agro waste: sugar cane straw ash (SCSA). Sodium hydroxide was used for preparing activating solutions. In order to reach the potential reactivity of the SCSA, a study varying the BFS/SCSA mass ratio and ${\mathrm{H}}_2\mathrm{O}/{\mathrm{Na}}_2\mathrm{O}$ molar ratio was carried out. The BFS/SCSA ratio varied from $100/0$ to $70/30$, and ${\mathrm{H}}_2\mathrm{O}/{\mathrm{Na}}_2\mathrm{O}$ was studied in the range of 11.1–18.5. To fulfill this objective, specimens were assessed by their compressive strength of mortars and microstructural studies of pastes [X-ray diffraction (XRD); thermogravimetric analysis (TGA); Fourier transform infrared spectroscopy (FTIR); and field emission scanning electron microscopy (FESEM)] in the curing time range of 3–90 days at 25°C. Results from these tests showed that the best BFS/SCSA and ${\mathrm{H}}_2\mathrm{O}/{\mathrm{Na}}_2\mathrm{O}$ ratios were $70/30$ and 18.5, respectively. This study revealed an interesting valorization of the SCSA as a complementary precursor in BFS-based AABs because of the improvement of mechanical properties and the reduction in the consumption of BFS in AAB.

The semicircular bending (SCB) test has received significant attention as a fracture test for asphalt concrete (AC) mixtures. This study focuses on the variability of the SCB test, considering several factors, including mix gradation (Superpave and coarse matrix high binder), aggregate shape, air voids, aggregate type (granite, hard limestone, and soft limestone), and interface properties. The SCB test was modeled using a discrete element method approach to analyze the fracture behavior of the AC mixture. A total of 100 cases were produced for each mix combination, for which the interface property was set the same as that of the mastic. The effect of the interface was studied by generating 50 cases for each mix with some specific aggregate types. The generation of aggregates and air voids within the internal structure was done randomly. The simulation results suggested that the initiation of cracks and their propagation through the sample are related to the location of aggregate and air voids within the specimen. Furthermore, the aggregate-mastic contact bond increased the strength of the AC mixtures and reduced the coefficient of variation for several cases.

The objective of this research was to determine the mechanical properties, including among others compressive strength $(f_c^{\prime })$, tensile strength $(f_{sp})$, flexural strength $(f_r)$, modulus of elasticity $(E_c)$, and Poisson’s ratio $(\nu )$ of a brick aggregate concrete (BAC) containing rice husk ash (RHA) as a partial replacement of cement. Concrete cylinders with 100-mm diameter and 200-mm height were cast using 0–25% RHA as a partial replacement of cement with water-to-binder ratios of 0.45, 0.50, and 0.55, with a mix ratio of 1:1.5:3, and cured in water at room temperature. The experimental results indicated that $f_c^{\prime }$ and $f_{sp}$ increased gradually with the increasing RHA up to 15%. However, the maximum values of these were observed with 10% RHA. By contrast, $f_r$ of BAC containing up to 25% RHA was found lower than that of control concrete. $E_c$ and $\nu$ of BAC with RHA were higher than those of control concrete. It was observed that mechanical properties of BAC were influenced significantly due to the inclusion of 15% RHA as a partial replacement of cement with a water-to-binder ratio of 0.50.

Despite positive advantages of steel fibers/chips in concrete, there are some drawbacks, such as decreasing workability, which restricts fiber contents, and the impossibility of fibers orientation management in the optimum direction. This study addresses these issues using an alternating magnetic field (AMF). Compression experiments are conducted on cubic fine-aggregate steel chip–reinforced concrete (SCRC) specimens An AMF of 0.5 Tesla (T) and 50 Hz is applied to either fresh SCRC in different directions or to hardened SCRC. The test setup is capable of magnetizing and compressing specimens simultaneously. Applying an AMF to ready-mixed SCRC facilitates the compaction process of concrete and affects compressive strength, depending on exposure direction; exposure in the optimum direction increases compressive strength more than 17%. Moreover, subjecting hardened SCRC to an AMF decreases its compressive strength by approximately 11%. Finally, the advantages of this technique in the concrete industry and the feasibility of developing this method for real-time behavior controlling of smart structures are discussed.

Asphalt pavement rutting is one of the most commonly observed pavement distresses, and crumb rubber can decrease this distress. This paper uses the two-dimensional (2D) and three-dimensional (3D) finite-element method (FEM) to simulate wheel track testing to predict rut depth in rubberized and conventional asphalt mixes and links these behaviors to an accelerated performance testing tool. Dynamic creep tests are performed on different specimens to obtain material parameters of the creep power law that is then used to model the viscoelastic behavior of asphalt mixtures. The Hamburg wheel rut tester (HWRT) is used for asphalt laboratory-accelerated rutting resistance testing and for calibration of material parameters developed in a dynamic creep test. Finite-element software is used to simulate HWRT and outputs of models are compared with the experimental observations. The results show that the difference between the predicted rut depth in 2D and 3D modeling and the measured rut depth in the laboratory is 13.5 and 11.5%, respectively. Furthermore, the rubberized asphalt mixture has 36% less rut depth than the conventional asphalt mixture.

Corrosion of steel reinforcement is the main focus of many studies on condition assessment of road infrastructure. The major uncertainty involves the behavior of steel rebar during dynamic loading imposed by traffic. Especially in countries that use deicing salts during winter, a combined loading situation emerges in which stress, frequency, and chlorides are present at the same time. Laboratory tests are conducted to evaluate the performance of single steel rebars simultaneously exposed to different model media (alkaline and chloride-containing solutions), different frequencies, and different initial stress levels. These so-called chloride-exposed fatigue tests show the impact of chloride-induced corrosion on the performance of dynamically loaded rebar. Despite the well-known low susceptibility of construction steel to enhanced stress-induced damage in a corrosive medium, the recorded behavior indicates altered electrochemical performance under dynamic load. The results allow for an alternative view of the assessment of service-life design of infrastructure.

For decades, synthetic fibers have been utilized to improve the performance of concrete structures by enhancing the flexural strength, modulus of elasticity, and other mechanical properties of concrete. However, there are uncertainties about how synthetic fibers affect the coefficient of thermal expansion (CTE), dynamic modulus of elasticity, and flexural strength of the concrete under freeze-thaw cycles. This study was an investigation of the effect of temperature change on the mechanical properties of fiber-reinforced concrete, including CTE, dynamic modulus of elasticity, and flexural strength. Two types of synthetic fiber, polypropylene (PP) and polyvinyl alcohol (PVA) fibers, with three dosages for each type, 6, 7, and $9\mathrm{kg}/{\mathrm{m}}^3$, were studied. The CTE was obtained using the severe temperature range specified by AASHTO specifications for measuring thermal effects in concrete bridge superstructures. Up to 300 freeze-thaw cycles were applied to specimens, while mass loss, dynamic modulus of elasticity, flexural strength, and CTE were measured in accordance with ASTM protocols. Adding fiber to concrete enhanced the flexural strength, increased the flexibility, decreased the dynamic modulus of elasticity, and increased the CTE. Specimens reinforced with PP fiber showed more flexural strength and flexibility than those reinforced with PVA fiber. Polyvinyl alcohol fiber–reinforced specimens exhibited greater CTE values compared with those reinforced with PP fiber. The added synthetic fiber enhanced the concrete’s resistance to freeze-thaw cycles. The optimum fiber dosage appears to be $7\mathrm{kg}/{\mathrm{m}}^3$, which generally had the best performance in terms of flexural strength, dynamic modulus of elasticity, and CTE while best preserving structural integrity under repeated freezing and thawing.

Foamed concrete is a versatile lightweight concrete that is finding increasing use in various application areas. A major concern with foamed concrete is its stability. Air voids can become unstable during production and placement or after placement of foamed concrete during the time when it is plastic and setting has not occurred. Because of the scarcity of information on foamed concrete stability, an experimental study was carried out to yield further information in this regard. Mixtures with foam contents from 20 to 90% were studied. The effects of using varying amounts of a plasticizing admixture in increasing the workability of the base mixture and its influence on stability were also studied. Although it was possible to produce and cast mixtures with up to 90% foam content, it was found that mixtures with foam contents of approximately 65% and higher became unstable some time after casting. Increasing the workability of the base mixture by using a plasticizer significantly improved the stability of foamed concrete mixtures and allowed achieving stability even at very high foam contents.

This study investigates the geopolymerization process of fly ash–based geopolymer paste specimens using acoustic emissions; the activating solution is a combination of silica fume and sodium hydroxide, made with two different water:solid weight ratios (w/s), 0.30 and 0.35. The specimens are cured in ambient conditions ($22\pm 3°\mathrm{C}$). The acoustic emission data are processed through pattern recognition (PR), and two clusters are identified and assigned to a specific mechanism depending on their characteristics. Results show that there is a predominant difference in the acquisition data between the two water:binder weight ratios. Pattern recognition shows that the greatest number of geopolymerization mechanisms, including dissolution of Si and Al atoms, forming bubbles, and microcrack initiation, occur at roughly the same time for the 0.3 w/s samples, whereas in 0.35 w/s samples the mechanisms occur sequentially. Final setting time of Vicat penetration tests, which assume a starting point of microcrack initiations, is 60 min after the test onset for 0.3 w/s ratio samples, whereas it occurs after approximately 600 min for 0.35 w/s samples. Microcrack initiation predicted by the pattern recognition technique coincides with the final setting times. Scanning electron microscope observations also coincide with the pattern recognition findings.

This work aims to prepare an eco-friendly binder from alkali-activated aluminosilicate solid industrial wastes. Eco-friendly binders provide a solution to the present ecological problem of producing non-portland-cement binders. Cement kiln dust (CKD) and ground granulated blast-furnace slag (GGBS) by-products were used to prepare the binder from alkali-activated GGBS-CKD mixed with $\mathrm{X}{\mathrm{Na}}_2\mathrm{O}:0.5{\mathrm{SiO}}_2\mathrm{mol}/\mathrm{kg}$. The characteristics of the prepared binder were studied using different techniques such as FTIR, DTA/TGA, XRD, and SEM. The compressive strength and bulk density of alkali-activated GGBS-CKD binders increased with increasing CKD contents up to 20% mass (Mix D2), then decreased with the increase of CKD contents from 30 to 50% mass. The chemically combined water and combined slag content of activated GGBS-CKD increased with increasing CKD content up to 50% mass (Mix D4). Mix D2 (20% mass of CKD) is the optimum mix composition. $\mathrm{Ca}(\mathrm{OH}{)}_2$ (CH) and ${\mathrm{CaCO}}_3$ containing CKD disintegrated the aluminosilicate matrix of GGBS. CH acts as a ${\mathrm{Ca}}^{2+}$ ion source to accelerate the pozzolanic activity to form rigid spheres of the compact massive matrix of (N, C)–A–S–H gel having low porosity. In addition, CKD has higher alkali and ${\mathrm{SO}}_4^{2-}$ content, which makes CKD an excellent activator to enhance the dissolution of GGBS to release silicate, aluminate, and/or aluminosilicate species and improve the alkali-activated network gel matrix formation.

Cracks are commonly observed in glulam joints even though the members have yet to experience the design load level. The cracks are commonly formed by tensile stress perpendicular to grain and are induced by shrinkage of the wood under varying climatic conditions and exacerbated by the confinements from steel plates and bolts. The aim of this research was to investigate the effect of cracks on the behavior of bolted joints under tension load. A theoretical method based on a quasi-nonlinear fracture mechanics model was proposed to estimate the failure load of tension joints. Both bolt ductile yielding and brittle failure, such as splitting and plug shear of wood, were considered in the analytical calculation. To obtain the load distributions of total load on individual bolts, a three-dimensional (3D) linear elastic numerical model was developed. Furthermore, full-scale tension tests were conducted on glulam joints with different configurations and crack patterns to validate the proposed theoretical method. It was found that the analytical method can reasonably predict the capacity and failure modes of bolted glulam joints. Moreover, the experimental results indicate that cracks have a dramatic effect on the stiffness and ductility ratio of the bolted joints.

Large compressive deformation associated with ideal plasticity-like stress plateaus is an extremely important performance characteristic of foamed concrete. However, there have been few investigations concerning the stress-strain characteristics of foamed concrete subjected to axial strain larger than 10% under uniaxial and triaxial compressive loading. In the current study, foamed concrete samples at three densities (250, 450, and $650\mathrm{kg}/{\mathrm{m}}^3$) were prepared and a series of tests were carried out. Axial stress-strain (${\sigma }_1\text{-}ϵ$) curves were obtained, and peak stress (compressive strength), elastic modulus, peak strain, and the postpeak stress-strain relationship were analyzed. The experimental results showed that the stress-strain characteristics for foamed concrete at all three densities are similar and each can be ideally simplified into four stages. The compressive strength of foamed concrete increases with density and confining pressure, whereas elastic modulus has a positive correlation only with densities regardless of confining pressure. Additionally, no significant correlation was detected between peak strain and density, but peak strain increases with confining pressure. A linear relationship between residual compressive strength and strain was found for almost all test cases. Based on the experimental results, theoretical models for the prediction of peak stress, elastic modulus, and the postpeak stress-strain relationship were derived incorporating the effects of density and confining pressure.

This study experimentally investigated the degradation of tensile properties of basalt fiber reinforced polymer (BFRP) profiles under acidic conditions. The effects of the temperature, pH value, and BFRP thickness were analyzed by means of accelerated aging. The surface conditions were also observed by a scanning electron microscope. The long-term acid resistance of BFRP was studied based on the Arrhenius model. The results showed that BFRP profiles have superior durability in acidic solutions. Under the condition of $\mathrm{pH}=2/55°\mathrm{C}/9\mathrm{weeks}$, BFRP showed a strength retention rate of 81.6% and almost no changes in tensile modulus. The degradation was attributed to the fracture of the interface between resin and fiber, caused by physical and chemical interactions in the acidic solution. Subsequently, a prediction model of the long-term degradation was built, and the relationship of the service years and strength reduction, considering different pH values and working temperatures, was established for durability design.

A research program directed at the study of welding historic wrought iron using modern welding methods has been conducted over the last several years at the University of Colorado Denver. Shielded metal arc welding methods have been developed for welding structural wrought iron material obtained from historic bridges. Wrought iron is distinguished from modern structural steel for which many welding procedures exist. Parametric studies of multiple end preparation geometries and preheat temperatures have been conducted to ascertain an optimum procedure for a full-penetration groove weld. Tensile tests have been conducted on welded material at room temperature and Charpy V-notch tests have been conducted on welded material at low temperatures.

The optional multiple repeated load (OMRL) test, which involves multiple load levels, is a more promising test method to simulate actual traffic load conditions on pavements. The presented study developed the load-temperature master curve for asphalt mixtures based on the OMRL test under four loading levels with varying temperatures (50 and 60°C) and confining stresses (0, 69, and 138 kPa). The effects of temperature and confining stress on the permanent strain of pavement mixtures were evaluated. Results show that higher temperatures increased the permanent strain and load sensitivity significantly. Higher confining stress dramatically improved the multiple flow numbers of the four asphalt mixtures with a consistent ranking. Likewise, the load sensitivity of asphalt mixtures was increased under lower confining stress. A load-temperature master curve for the slope of strain growth could be established by shift factors, which means the OMRL test conducted under one temperature and confining stress level can be used to accurately predict permanent deformations under all other temperatures or confinements.

Chemical stabilization is commonly used to improve engineering properties of problematic soils. This study investigates the possibility of using calcium carbide residue (CCR), a by-product of the acetylene production process, to improve engineering properties of clays. For this purpose, an array of unconfined compressive strength (UCS) and consolidation tests is performed on green bentonite (with predominantly montmorillonite mineralogy) and white kaolin (with predominantly kaolinite mineralogy) to assess strength and compressibility of the stabilized clays with different CCR dosages and at various curing times. Furthermore, a suite of microlevel tests characterizes the microstructural properties of the stabilized clay matrices to provide further insight into the mechanism of strength development. Microlevel assessments are performed using field emission scanning electron microscopy (FESEM), X-ray fluorescence (XRF), particle size analysis (PSA), and nitrogen-based Brunauer-Emmett-Teller (${\mathrm{N}}_2$-BET) surface-area analysis tests. The experimental results suggest that CCR can significantly improve the strength and compressibility characteristics of the tested clays. The highest strength improvements are attained with 9 and 12% of CCR for the tested bentonite and kaolin, respectively. Furthermore, the UCS values from the current study are compared with those reported in the literature for the same clays stabilized with several traditional and nontraditional additives. Microlevel observations delineate the formation of new cementing materials that result from chemical reactions between CCR and clay minerals. Less-porous and denser soil fabrics are seen on the surface of clay particles. Findings of this study confirm the potential of CCR as a sustainable alternative to traditional stabilizers for soil improvement purposes in civil engineering applications.

Reduction in pore water pressure is a useful strategy to improve the stability of slopes. Deep draining trenches can be used for this purpose. For the realization of deep trenches, the usual conventional construction techniques are not adequate and the use of adjacent vertical panels, built by means of the methods well-established for diaphragm walls, is necessary. However, unbonded materials (i.e., gravels) cannot be used, because the excavation of a panel adjacent to one already built will cause instability. For this scope a bonded material such as pervious concrete can be used. It must have high permeability; filtering capacity, in order to prevent internal erosion of the soil in which the trench drain is installed; and sufficient shear strength after a short curing time to avoid the instability of adjacent previously built panels. This paper reports the hydraulic characterization of two mixtures of pervious concrete carried out in the laboratory. Hydraulic conductivity was measured in saturated conditions. Then, the water retention functions of the mixtures were experimentally deduced by investigating different calculation options and their impact on the simulation of seepage processes through an unsaturated soil mass, in which an ideal trench is located.

Macrosynthetic fiber–reinforced concrete (MSFRC) has reached maturity as an engineering material and is widely being used in some civil engineering applications. However, design approaches for MSFRC are not as well developed as for steel fibers, and there is a need for further research on this new material in order to further help the development of guidelines and increase the practical applications. The main objective of this study is to critically review the present state of knowledge and applications of MSFRC and to study the effect of these fibers on fresh- and hardened-state performance of different concrete mixtures. Seven groups of concrete mixtures were produced with different volume fractions of steel fibers, fly ash, macrosynthetic fibers, and chemical admixture. Mini slump, compression, and flexural tests were conducted on the specimens for evaluating their mechanical performance, and water absorption and sorptivity tests were also conducted for measuring the permeability of these different concrete mix groups. Therefore, with this comprehensive study, a detailed understanding is gained about the present state of applications of macrosynthetic fibers and their potential for being used as a fiber-reinforcement mechanism in concrete elements.

The largest boron reserves in the world are located in Turkey. The production of boron compounds and use of generated boron derivative waste during this production are extremely important for both economically and environmentally. This study evaluates boron derivative waste and investigates doping effects of heat-treated boron derivative wastes on mineralogical, microstructural, and mechanical properties of cement mortar. The waste, portland cement, and wastes heat-treated at temperatures of 400–900°C are characterized. The cement is partially replaced with heat-treated wastes at 800 and 900°C in weight ratios of 15, 25, and 35%. Compression tests are conducted for all mortars and proximate strength value to reference mortar is obtained with the incorporation of waste heat-treated at 800°C by the 25% ratio. From a strength point of view, thermally processed waste is practical for use in the production of cement mortar at 25% by weight.

This study aimed to evaluate cement-bonded panels produced with sugarcane bagasse cured by accelerated carbonation at early ages. The cement-bonded bagasse panels produced were subjected to two separate curing processes: (1) curing for 2 days (48 h) in a climatic chamber, followed by 25 days in an air-saturated environment; and (2) curing for 2 days (48 h) in a climatic chamber, and after in environment with carbon dioxide (24 h), followed by 24 days in an air-saturated environment. After 28 days of curing, physical and mechanical characterizations were conducted following the recommendations of European regulations. The physical results of the cement-bonded bagasse panels were lower than that the required by international standards. Moreover, accelerated carbonation decreased the water absorption value by 37.29% and the thickness swelling value by 64.84%, i.e., there was an improvement on dimensional stability of the carbonated cement-bonded bagasse panels. In addition, accelerated carbonation increased the mechanical strength values in the bending of the modulus of rupture by 78.69% and the modulus of elasticity by 125.13% of the cement-bonded bagasse panels.

An experimental investigation was conducted to evaluate both residual capacity and the damage of the concrete material in previously damaged RC columns. Three circular columns, each caged to provide low, medium, and high level of confinement, were axially loaded to failure. All damaged columns were then cut into three pieces, and two cored cylinders were taken from each piece. The first core was prepared and instrumented for compression, whereas the second was sliced into a number of 25-mm disks for permeability testing. For each column, a comparison was made between the stress–strain relationships of concrete cores, intact concrete cylinders, and confined concrete associated with columns. Results showed an average loss of 68, 42, 33, and 30% in the lateral strain, axial strain, strength, and stiffness of the damaged concrete, respectively. A permeability-based damage profile was established that showed the intensity and extent of damage in the concrete. The study showed a 33% loss in axial strain capacity and a 17% reduction in compressive strength, resulting in a 46% increase in the permeability of the concrete.

Hot-mix asphalt (HMA) mixtures with high content of reclaimed asphalt pavement (RAP) have been investigated and applied in the laboratory and in plants. An asphalt mixture can be considered as a four-scale assemblage of components with different characteristic length scale, binder, mastic, mortar, and finally mixture. This paper investigates the mechanical properties of HMA mixtures with high RAP contents through the multiscale of binder, mortar, and mixture, and analyzes the property correlations between them. RAP contents of 30, 50, and 85% were adopted for tests; meanwhile fresh asphalt (0%RAP) and 100%RAP were also prepared for comprehensive comparison. Frequency sweep test, repeated creep test, and bending beam test were used to measure the properties of mortars, meanwhile, dynamic modulus test, flow number test, and semicircular bending (SCB) test were used to measure the properties of mixtures. It is found that with the increase of the RAP content, binder, mortar, and mixture show similar changes of mechanical properties, behaving as complex modulus increases with viscoelasticity reduce, and rutting resistance improves, whereas thermal cracking resistance declines. The mechanical properties of binder, mortar, and mixture at high and low temperature are well related. Fine aggregates have significant influence on the high-temperature properties of mortars, and the mixture modulus is highly affected by coarse aggregates.

Engineered cementitious composites (ECCs) have attracted increasing attention in recent years owing to its unique properties of tensile strain hardening behavior and tight multiple cracks. A new kind of multiscale ECC (MS-ECC) that contains polyvinyl alcohol (PVA) fibers and calcium carbonate (${\mathrm{CaCO}}_3$) whiskers was designed based on the design models of ECC. Nine series of MS-ECC proportions were prepared, and the mechanical properties, including compressive strength, uniaxial tensile behavior, flexural behavior, and microstructures of the mixtures, were studied. The experimental results indicate that the strength of MS-ECCs was enhanced with the proper addition of ${\mathrm{CaCO}}_3$ whiskers. Moreover, the addition of ${\mathrm{CaCO}}_3$ whiskers increased the robustness of the ECC material. The microstructure experiment demonstrated that the ${\mathrm{CaCO}}_3$ whiskers and PVA fibers could effectively interact with different scales.

The polyethylene terephthalate/carbon black (PET/CB) composite was fabricated by twin-screw extrusion and injection molding method. The morphology, electrical conductive percolation threshold, tensile piezoresistivity, and stress-strain behavior of the composite were investigated. A scanning electron microscope showed that the carbon black was dispersed in the PET matrix homogeneously, but some little visible carbon black agglomerates can also be detected in the composite. The electrical conductive percolation threshold of composite was 15% by weight of carbon black. When the carbon black content changed from 15 to 20% by weight, the PET/CB composite had the tensile piezoresistivity. At the axial tensile strain from 0 to 0.001, the composite with 20% by weight carbon black had the highest value of fractional change in resistivity, which had a linear relationship to tensile strain. After five times cyclic tensile loading and 100,000 cycles fatigue tensile loading, the composite showed good repeatability in tensile piezoresistivity. The yield strength and tensile strength of composite were 18 and 23.8 MPa, respectively. The results showed the potential way of using PET/CB composite as strain sensors for civil engineering.

Pervious concrete (PC) is a class of porous materials that has found application in building materials, specifically in pavements, for its stormwater mitigation abilities. X-ray microcomputed tomography was used to understand and quantify the three-dimensional (3D) pore morphology, shape factors, and size descriptors in PC mixtures prepared with varying porosity. The Zingg pore shape classification indicated higher percent of rod-shaped pores and the frequency of spheroid-form pores was higher in single-sized mixtures, whereas dense mixtures had higher occurrence of blade-form pores. The average pore sphericity was in the range of 0.40–0.60, indicating semispherical pores. Few large-sized pores in PC had a significant influence on the relation between 3D pore-structural-permeability properties. The visualization of 3D pore structure indicated the importance of isolated pores in PC for periodic maintenance. The new findings on the pore structure will assist in mix design optimization, selection of mixtures, and modeling of PC.

In light of the current increasing interest toward nanomaterials for concrete technology, it appears that nanocellulose (with its incredible properties) can shape a promising sustainable candidate. This study investigates the influence of a new type of nanocellulose materials, namely, cellulose filaments (CF), on the properties of cement pastes and self-consolidating concrete (SCC). CFs were found to alter mixture rheology and improve its stability because of the filaments’ hydrophilicity. While the compressive strength of CF pastes was adversely affected (because of air entrainment and filament agglomeration), the flexural capacity was increased by up to 25%. In SCC, all measured mechanical properties were enhanced. Strength improvements of up to 16% (in compression), 34% (in splitting tension), 22% (in flexure), and 96% (in energy absorption) were obtained. These improvements were attributed to two effects imparted by CF: nanoreinforcing and internal curing. The former was evidenced by microstructural analysis, while the latter was confirmed by the assessment of autogenous shrinkage, in which CF reduced the shrinkage strains at 7 days by up to 31%. In SCC, CFs also imparted a viscosity-modifying effect, in which the hardened properties were enhanced via improving mixture stability.

Fracture properties of cement paste at an early age are difficult to determine using conventional methods because of its low strength. By using an indentation technique, this paper reported a fracture test method for early-age cement paste in microscale. Power equations were employed to capture the load-displacement curves, where the power indexes were acquired to be associated with energy constants. The elastic energy constant may be a featured parameter to characterize solid phases. An explicit expression for estimating plastic energy with the effect of holding load at peak force was established based on an energy method. The fracture energy, energy release rate, and fracture toughness of a cement paste cured for 3 days were calculated directly from indentation curves via this model. The microstructure of the cement paste was studied using scanning electron microscopy and backscattering analysis. The results show that the fracture data of the cement paste at an early age from the indentation tests are stable and comparable with those by conventional macrofracture tests. The indentation-based fracture testing method may provide an efficient method to assess the fracture properties of cement-based materials.

The long-span steel bridge has experienced a rapid growth in China during the last two decades. Steel deck surfacing plays an important role in the durability of long-span steel bridges. So far, three types of surfacing materials have been used in China’s experience: epoxy asphalt (EA), Gussasphalt (GA), and stone matrix asphalt (SMA). Four main double-layered surfacing structures have been used via the combination of the three materials, GA-EA (EA on the top), GA-SMA, EA-SMA, and EA-EA. The objective of this study is to identify the best surfacing strategy from the four existing double-layered structures. A comprehensive performance evaluation was conducted to achieve this goal. The rutting resistance, low temperature performance, fatigue performance, and moisture damage resistance were evaluated for the individual surfacing materials, double-layered surfacing structures, and the composite structures consisting of steel deck and surfacing structures. The results showed that EA-EA had the best high-temperature performance, GA-EA had the best low-temperature performance, GA concrete had the lowest moisture susceptibility, and GA-EA possessed the best fatigue performance. In addition, the layer position had an influence on the rutting performance of the double-layered structure. Then, a simple ranking method taking account into the comprehensive performance was used to identify the best surfacing strategy. The GA-EA structure was found to be the best surfacing strategy for long-span steel bridges in China after the comparison.

A new type of microwave absorption cement-based material was prepared by using a magnetic hollow fly ash microspheres $(\mathrm{HFAM})/{\mathrm{Fe}}_3{\mathrm{O}}_4$ composite as the absorbent. Through the chemical precipitation method, a nano-${\mathrm{Fe}}_3{\mathrm{O}}_4$ layer was coated on the surface of HFAM to obtain the $\mathrm{HFAM}/{\mathrm{Fe}}_3{\mathrm{O}}_4$ composite. Then the composite was added into mortar to prepare microwave absorption cement-based material. The mineral components, micromorphology, and electromagnetic parameters of the $\mathrm{HFAM}/{\mathrm{Fe}}_3{\mathrm{O}}_4$ composite and the reflection loss of the cement-based material were investigated. It was found that the $\mathrm{HFAM}/{\mathrm{Fe}}_3{\mathrm{O}}_4$ composite had superparamagnetism, and its saturation magnetization and the residual magnetization were $32.67\mathrm{emu}/\mathrm{g}$ and almost zero, respectively. The best microwave absorption of the cement-based material was obtained at 3% $\mathrm{HFAM}/{\mathrm{Fe}}_3{\mathrm{O}}_4$ composite to cement, of which the bandwidth of the reflection loss lower than $-10\mathrm{dB}$ (responding to 90% microwave absorption) was nearing 8 GHz, showing excellent microwave absorption performance.

This paper presents a methodology for designing mix proportions for a targeted compressive strength of alkali-activated slag concrete (AASC) using particle packing theory. Very little information is available on a complete methodology in designing the AASC mix. Ground granulated blast-furnace slag is activated with sodium silicate–based and sodium hydroxide–based alkaline activator solution. Sodium hydroxide concentration, binder content, and the alkaline solution:binder ratio are taken as variables. The aggregates are proportioned using particle packing theory, resulting in fewer voids and a dense concrete mix which hinders the ability of external aggressive chemicals to migrate into the concrete. Results show that the sodium hydroxide concentration and alkaline solution:binder ratio are the most influential parameters on compressive strength and workability of AASC. This paper presents a mix design procedure for AASC with a detailed example.

Predicted values for the shrinkage and swelling potentials of expansive soils are principal parameters used in the design of ground-supported structures because unsteady soil movement affects long-term structural reliability. To characterize the shrink and swell indexes of a soil, ${\gamma }_h$, the change in volume of the soil must be measured after exposure to varied controlled conditions. Several volume measurement methods have been commonly employed in geotechnical engineering; however, all of these methods have practical limitations so engineers have long sought an alternative test method. A method developed by geologists for rock samples was adapted to determine the volumes of engineering soil samples, and it was implemented during an investigation of highly expansive soil samples from a construction site located on Interstate 35 in San Antonio. Twenty samples from two geotechnical borings were analyzed following a pressure plate apparatus test protocol, which subjected the soils to varied levels of pressure and suction (moisture) and then determined how their volumes changed. Volumes were determined at various stages of testing to an uncertainty of $\pm 0.3\%$ or better in a manner that proved repeatable and nondestructive. Shrinkage index values derived from these analyses ranged from 0.0068 to 0.0317 (mean of 0.0161) and the swelling index values ranged from 0.0077 to 0.0304 (mean of 0.0161), which are consistent with values found by other studies of expansive soils. Thus, the effective measurement of soil sample volumes enabled the determination of the shrinkage and swelling indexes of expansive soils, which made it possible for geotechnical engineers to design a more cost-effective highway retaining wall.

Owing to the considerable ${\mathrm{CO}}_2$ emission resulting from portland cement (PC) production, a great deal of research has been devoted to finding alternative binders, among which alkali-activated binders have shown promising potential. Fly ash and natural Pozzolan are two choices of the starting ingredients for alkali-activated mateials, with the latter having rarely been studied. The current study compares the flow, strength, and transport properties of natural Pozzolan– and fly ash–based alkali-activated mortars. To this end, various mortar mixtures were prepared using fly ash or natural Pozzolan as aluminosilicate source (precursor) and 2.5, 5, 7.5, 10, and 12.5 M sodium hydroxide solution as alkaline activator. Several experiments were conducted on produced mortars to evaluate their fresh and hardened properties including including flow, compressive and flexural strengths, elastic modulus, absorption and total void volume, and rapid chloride migration. These tests were also conducted on PC mortars to compare the performance of alkali-activated mortars to that of PC mortars. The results of this study revealed that natural Pozzolan can be activated and perform to the same level of fly ash. However, the activation rate was slower and the minimum level of alkaline concentration for a proper activation was higher for natural Pozzolan than fly ash. While alkali-activated mortars displayed noticeably lower compressive strength than PC mortars, the studied mortars activated with sodium hydroxide molarities of 7.5–12.5 M produced strength adequate for structural applications. The transport properties of alkali-activated mortars having high NaOH molarity were similar to those of PC mortars.

Polymers have been incorporated into asphalt as a way to mitigate permanent deformation at high performance temperatures for many years. There are several types of polymers used in asphalt binders to improve the rheological and engineering properties of asphalt mixtures, including styrene butadiene styrene (SBS), ground tire rubber, styrene butadiene rubber, ethylene vinyl acetate, and polyethylene. SBS is the most popular polymer used in high-traffic pavement compared with other polymer modifiers. However, recent studies have shown that mixtures containing some other modifiers are cost-effective and perform as well as or better than SBS-modified binders in some cases. The experimental design in this study included one base binder, PG 64-22; two aggregate sources; SBS and five other modifiers; and three antistripping additives (ASAs). Asphalt pavement analyzer (APA) and Hamburg wheel tracker (HWT) were used to investigate the rut resistances of these alternative modified-asphalt mixtures. It was found that the APA and HWT rut depths of all alternative modified mixtures met the requirements of rut resistance, and these values were typically located in the range of 1–3 mm regardless of polymer type, ASA type, and aggregate source. The ASAs used in this study were effective and did not display significant differences in rut-resistance values from various polymerized mixtures. Simple logarithmic formulas for HWT rut depth during the loading process and the normal distributions of rut depths were developed in this study.

In the last few years, use of recycled concrete aggregate (RCA) in road applications has increased. For this application, concerns exist regarding the frost resistance of RCAs and the deicer-salt scaling resistance of concrete containing recycled aggregate concrete (RAC), especially in cold climates. In this investigation, the frost resistance of four types of aggregates, including a natural aggregate (NA) and three types of RCAs, were examined according to a range of standard methods. Also, the deicer-salt scaling resistance of concrete mixes containing the aforementioned aggregates was assessed. Frost resistance tests showed that several of the standard test methods lead to unreliable results for frost resistance of RCAs. The deicer-salt scaling resistance of RACs had an acceptable correlation with only one particular method. In fact, testing concrete specimens containing RCAs is considered the best way to assess the frost resistance of RCAs.

The aim of this paper was to study the mechanical properties and damage evolution of concrete added with ${\mathrm{Al}}_2{\mathrm{O}}_3$ hollow sphere (AHSC) under impact loading. The impact compression experiments were carried out by a 100-mm-diameter split Hopkinson pressure bar apparatus. The mechanical performance, including strength, deformation and failure pattern, were analyzed. The damage factor ($DF$) was defined as the dissipation of concrete constitutive energy and the damage evolution was explored. The results show that the evolution of AHSC dynamic stress fell into four stages: elastic stage, plateau stage, densification stage, and failure stage. The plateau stage, which did not exist in the dynamic stress-strain curves of plain concrete (PC), could help AHSC better absorb energy under impact loading. Along with the increase of strain rate, the dynamic strength increase factors (DIF) of both AHSC and PC increased continuously. Furthermore, the DIF of AHSC was larger than that of PC at the same strain rate. Moreover, the critical strain shared the same law with DIF, indicating that the addition of ${\mathrm{Al}}_2{\mathrm{O}}_3$ hollow sphere could improve the deformation property of concrete. The analysis of failure patterns of specimens indicated that the damage degree got higher with the increasing strain rate, and AHSC was more seriously damaged than PC at the same strain rate. On the basis of the increasing rate of $DF$, the dynamic damage evolution could be divided into three periods. There was a jumping period in the damage evolution curve of AHSC, and this phenomenon became more obvious with the increase of strain rate.

Increased use of industrial residues for soil stabilization is a necessary practice for sustainable geotechnics. The present study investigates carbide lime, the residue resulting from the production of acetylene gas, for its potential use as a substitute for commercial lime in soil stabilization. Carbide lime obtained from a plant in southern Brazil was characterized for its physical properties and morphology based on grain size distribution, specific surface area, scanning electron microscopy and energy dispersive X-ray spectroscopy, mineralogy based on X-ray diffraction analysis and thermogravimetric analysis, and chemical composition by X-ray fluorescence spectrometry and wet chemical analysis. The total and leachable toxic heavy metals concentrations were also determined by the U.S. EPA acid digestion and ASTM water shaking standard procedures. The improvement in mechanical behavior with an increase in the carbide content and curing period was demonstrated by increased unconfined compressive strength. Carbide lime consists predominantly of portlandite [$\mathrm{Ca}{(\mathrm{OH})}_2$] mineral and possesses characteristics similar to commercial lime, and is also nonhazardous. Overall, results from this study show that carbide lime possesses excellent physical, mineralogical, and chemical characteristics and is environmentally benign for use as an alternate low-cost, effective amendment for soil stabilization.

The compressive behavior of membrane materials used in spiral case structures (SCSs) is of interest because, to a large extent, it determines the structural performance of SCSs. Unfortunately, it has not been dealt with in depth and was routinely assumed to be linear and elastic in SCS structural design. The aim of this work is to further current knowledge of the compression-resilience responses of the two most commonly used membrane materials: the polyurethane (PU) cork and polyethylene (PE) foam. A lever-type consolidometer was employed for the current cyclic compression-resilience test. The compressive behavior of both materials was stabilized after six loading/unloading cycles (with maximum pressure of 1.0 MPa). Strong evidence of the nonlinearity and inelasticity of both materials was found. The relevance of cyclic loading/unloading to the permanent set of both materials is clearly supported by the current findings. This study has gone some way toward enhancing the community’s understanding of the nonlinearity and inelasticity of the two membrane materials and has highlighted the need to consider them in the structural design of SCSs.

EPS is the international acronym for expanded polystyrene, which is a thermoplastic derived from petroleum. Each EPS bead is composed of 98% air and 2% raw material (in mass); therefore, its considered a waste problem because it occupies a lot of space in landfill sites. An alternative for reducing the disposal of this product is using it as a soil reinforcement material in earthworks. This paper presents the experimental study performed to assess the behavior of three types of soil (colluvial clayey soil, sandy soil, and bentonite) reinforced with the addition of EPS beads. The soil samples with and without the addition of EPS beads were submitted to compaction tests, isotropically consolidated drained triaxial compression tests, and direct shear tests. The results showed that the soil type, the content of EPS beads, and the level of confining stress influenced the final mechanical behavior of the composites in relation to the resistance parameters.