Journal of Materials in Civil Engineering

Lightweight fills constructed by the use of expanded polystyrene block (EPS-block) geofoam (geofoam block) is known to be susceptible to horizontal loading since the vertical pressure which enhances the shear resistance along the interface of individual blocks is low. Therefore, research has focused on the methods to increase the interface shear resistance of geofoam blocks. This study investigated the use of interlocking mechanisms by conducting direct shear tests on four different interlock configurations. An interlock configuration utilized a number of ledges and notches to interrupt the continuous horizontal shearing plane in-between geofoam blocks. Two different densities of geofoam blocks (EPS19 with a minimum density of $18.4{\mathrm{kg}/\mathrm{m}}^3$ and EPS29 with a minimum density of $28.8{\mathrm{kg}/\mathrm{m}}^3$) were used in order to investigate the effect of material hardness on stress-strain behavior and interface friction properties. The results of this study showed that the interlocking mechanism improved the interface shearing resistance of geofoam blocks. The number of ledges and notches used in an interlocked configuration had an effect on the interface shear strength properties, and higher numbers raised the interface failure envelope to the level of internal shear strength of monoblock EPS. In conclusion, implementing an interlocked configuration changed the EPS/EPS interface friction mechanism from purely frictional to frictional-adhesional.

An investigation into the behavior of a contaminated clay soil and its treatment was carried out through a program of experimental tests. The contaminated soil samples were prepared with different percentages (3, 6, and 9%) of a glycerol solution with 40% concentration. The samples were prepared as mixtures of clean or glycerol-contaminated soil with different cement contents (3, 6, and 9%). Atterberg limits and unconfined compressive strength (UCS) tests were conducted on the samples. The results showed that Atterberg limits are reduced by adding glycerol or cement or adding glycerol to soil-cement. Both the strength and stiffness of the contaminated soil are reduced by increasing the degree of contamination. The results of treated soil showed that adding cement to contaminated soil increases the strength and the amount of increase in strength is dependent on the percent of cement, curing time and degree of contamination. Based on scanning electron microscopy analysis, it was found that the presence of glycerol prevents the interaction between soil and cement.

Numerical and empirical models addressing the drying shrinkage cracking behavior of joint-free steel-fiber-reinforced concrete (SFRC) slabs are presented. Effect of water–cement ratio, admixtures, and free shrinkage are considered. Mechanical restrictions including base friction, fiber dosage, and interfacial bond properties restrain the growth of microcracks into main cracks and also reduce crack opening. A model based on a finite-difference equilibrium solution of a one-dimensional (1D) slab on frictional ground simulates the formation and subsequent opening of cracks in the slab. Results are compared with an empirical predictive tool for crack opening. A sensitivity study shows that correlation of predicted crack opening reduced by increasing fiber volume, base friction, and interfacial bond strength. Case studies are conducted on three slabs in service at different occasions and both models are used to predict the crack opening. While these models are developed based on different methodologies, they are related to a great extent by addressing the same mechanical characteristics. A simple method to estimate the slab curl is proposed and a parametric study has been conducted.

Engineered cementitious composites (ECCs) are relatively new construction materials characterized by strain-hardening behavior under excessive tensile loading. Unlike conventional concrete materials, which generally show failure after first tensile cracking, ECCs strain-harden upon excessive loading by creating multiple closely-spaced microcracks. Given the fact that crack widths in ECCs are at micron levels, water movement into these cracks through capillary suction requires further attention, especially under frost action. This paper therefore explores the effectiveness of frost action on water movement into microcracked ECCs. The experimental study covered the sorptivity measurements of ECC mixtures produced with mineral admixtures with different chemical compositions after exposure to cyclic freezing and thawing ($\mathrm{F}/\mathrm{T}$), in accordance with ASTM C 666, Procedure A. Air-void characteristics of ECCs were also compared. Experimental findings showed that air-void parameters are not the sole influential parameters on the durability of microcracked ECCs under frost deterioration. Instead of being negatively influenced by the severe conditioning under frost action until the end of $150\mathrm{F}/\mathrm{T}$ cycles, sorptivity measurements of ECCs went down owing to self-healing in microcracks, depending on mixture composition. However, after $150\mathrm{F}/\mathrm{T}$ cycles, deterioration surpassed the self-healing effect and increased sorptivity measurements.

An innovative quality assurance method is used to assess the stiffness of the bedding material to a water pipeline located in Texas. The method used is a combination of spectral analysis of surface waves technique (SASW) and geostatistics. SASW tests were conducted to measure the stiffness of pipeline bedding material at 15 sections along the pipeline after different curing periods of 1, 3, 7, 14, and 28 days. The stiffness measurements from SASW tests are used in geostatistical analysis to determine stiffness properties at untested locations and map the variation of stiffness values along the pipeline. The SASW measurements indicated a significant increase in mean stiffness value of bedding material from 267.5 MPa on day 1 to 442 MPa after a 28-day curing period. The geostatistical analysis predicted and mapped the stiffness of bedding material over the entire pipeline by incorporating the variability present in the known stiffness measurements. This research highlights the adaptability of geostatistics and in situ measurements in assessing the quality of the pipeline bedding material.

This paper investigates the potential use of phase change materials (PCM) in concrete pavements to store heat, which can be used to reduce ice formation and snow accumulation on the surface of the concrete pavement. The thermal properties of the PCMs are evaluated using a low-temperature differential scanning calorimeter (LT-DSC) while a longitudinal guarded comparative calorimeter (LGCC) is used to evaluate the thermal response of cementitious mortar containing the PCM. Paraffin oil (petroleum based) and methyl laurate (vegetable based) were selected as PCMs since they have high enthalpies of fusion ($\sim 130–170\mathrm{J}/\mathrm{g}$) and have desirable freezing temperatures ($\sim 2–3°\mathrm{C}$) during the liquid to solid phase transformation. Two approaches were used to place the PCM in the mortar specimens: (1) placing the PCM in lightweight aggregate (LWA) in mortar and (2) placing the PCM in an embedded tube that is placed in mortar. The durability and stability of the PCMs in the cementitious system were studied by monitoring the change in enthalpy of fusion, mass loss, pulse velocity, and compressive strength. When the PCM was placed in the mortar specimen using LWA, the paraffin oil can release a considerable amount of heat during phase transformation, which can be used to melt ice and snow. However, it was observed that the methyl laurate reacts with the cementitious matrix, causing damage to the mortar. Both paraffin oil and methyl laurate showed promising performance to melt ice and snow when the PCM was placed in an embedded tube in the mortar specimen.

The study investigated the fatigue performance of rubberized stone matrix asphalt (SMA) in the dry process and compared its fatigue characterization with SMAs with other typical binders. Five SMA mixtures were used with the following asphalt binders: (1) virgin asphalt of PG 67-22, (2) crumb rubber modifier (CRM) modified in wet process, (3) CRM modified in dry process, (4) terminal-blend binder, and (5) styrene-butadiene-styrene (SBS) modified binder. Dynamic modulus and direct-tension fatigue tests were performed using the asphalt mixture performance tester (AMPT) system. In addition, improved linear amplitude sweep (LAS) tests were performed on the binders by a dynamic shear rheometer (DSR). The fatigue test data were analyzed by the simplified viscoelastic continuum damage (S-VECD) theory. The results showed that (1) dynamic modulus of the rubberized SMA in the dry process was similar to that of the wet process and higher than that of SMA with virgin asphalt, although a little lower than those of SMAs with terminal-blend binder or SBS binder at high temperatures; (2) the damage resistance and fatigue life of the rubberized SMA in the dry process are higher than those of SMA with virgin asphalt and similar or slightly higher than with the wet process, but lower than SMAs with terminal-blend binder or SBS binder; and (3) the virgin binder had lower damage resistance and fatigue life, followed by the CRM binder in the wet process, the terminal-blend binder and SBS binder had higher damage resistance and fatigue life. This is consistent with the mixture results for the direct-tension fatigue tests.

This paper presents an investigation on a new material composed of magnesium phosphate cement (MPC), fly ash, and rape stalk. The main goal is to evaluate the viability of using this new material as an insulation material for buildings. Several composites with different weight concentrations and three different rape stalk sizes were prepared. The density, compressive strength, and thermal conductivity of the material were measured. Experimental results show that the proposed MPC rape stalk concrete possesses required material properties for production of lightweight concrete in structural and non-structural applications. The physical properties of the rape stalk indicate that it is a promising alternative to hemp hurd for producing plant concrete. Results also indicate that MPC might be a better cementitious material for producing plant aggregate concrete compared with portland cement or lime.

This study investigates the effect of chemical degradation on the residual mechanical properties of ultrahigh performance fiber-reinforced concrete (UHPFRC) after temperature exposure ranging from 100 to 900°C. Emphasis has been placed on the isolation of chemical degradation. A long drying period and a slow heating rate were used to minimize the buildup of excessive pore pressure caused by water evaporation and transport constraints. To identify critical areas of chemical degradation, differential scanning calorimetry and thermo gravimetric analysis were performed. The results were used in correlation with existing research to aid in deriving a simplified model for predicting the temperature-dependent stress versus strain behavior of UHPFRC.

Fatigue cracking is considered to be one of the main pathologies in asphalt pavements, contributing to the reduction of its service life and generating high costs as a consequence of more maintenance works. Because of the importance of road quality in society’s economic development, techniques to avoid and reduce the adverse effects derived from cracking phenomena are necessary. For this purpose, this research focuses on the development of a sustainable and economic solution that uses reinforced polyethylene pond wastes as an antireflective cracking system placed between asphalt pavements layers. Three different pavement sections were studied in the laboratory: A reference one with no anticracking system; a pavement section with geotextile as the common anticracking system; and a similar one with reinforced polyethylene pond waste. The results obtained from the mechanical performance testing showed that this technique could provide an optimal solution to reduce the effect of this pathology, and to offer a new way to valorize these wastes. In addition, in comparison with the other solutions, reinforced polyethylene pond liners are more effective in reducing the propagation of cracks through the asphalt pavement.

Microbial-induced calcite precipitation (MICP) is one of the environmentally friendly ways to improve engineering properties of sandy soil. A laboratory study was conducted to investigate the effect of randomly distributed discrete fiber on the mechanical properties of MICP-treated soil and to discover the corresponding mechanisms. Specimens were prepared at four different fiber ratios (0.1, 0.2, 0.3, and 0.4% by weight of sand). MICP were catalyzed by Sporosarcina pasteurii at the concentration of $4.3\times {10}^7\mathrm{cells}/\mathrm{mL}$. MICP-treated sand samples were prepared using full-contact flexible molds. The results showed that remarkable improvements in shear strength, ductility, and failure strain were achieved with fiber addition in the MICP-treated sand. The unconfined compression strength (UCS) and shear strength increased gradually with an increase in fiber content up to a fiber content of 0.3%. The optimum fiber content in the MICP-treated sand was found to be 0.2–0.3%. The UCS of MICP-treated sand at the optimum fiber content is more than two times higher than that without addition of fiber. The failure strain of MICP-treated sand at the optimum fiber content is nearly three times higher than that without addition of fiber. Residual strengths of MICP-treated sand at the optimum fiber content are near 100 kPa, while the residual strength is 0 kPa for that of MICP-treated sand without fiber. The cohesion and angle of internal friction of fiber-reinforced sand prepared at different ratios of fiber increased by 29–45 kPa and 7.6–11°, respectively. The inclusion of fibers increases the residual strength occurring after peak stress and decreases the brittle behavior of the MICP-treated sand.

Effectiveness of E. coli DH5α biofilm growth on mortar surfaces to inhibit microbiologically-influenced deterioration is investigated. Unlike traditional chemical deterioration processes through direct acid addition, biodegradation is realistically simulated through biogenic acidification using two species of sulfur-oxidizing bacteria (SOB). Calcium leach-out analysis, scanning electron microscopy (SEM), and X-ray diffraction (XRD) suggest that E. coli DH5α biofilm prevents or controls microbiologically-induced mortar deterioration. The pH of the solution in the reactor containing E. coli biofilm-covered mortar did not decrease as the SOB was not able to grow. However, the growth of SOB in the control reactor with mortar increased the sulfate concentration to $6,350\mathrm{mg}/\mathrm{L}$ and the calcium leach-out to 69 ppm. SEM and XRD analyses showed the presence of gypsum on control mortar without E. coli biofilm; however, there was no sign of gypsum on the biofilm-covered mortar surface. Fluorescence in situ hybridization analysis shows that SOB did not attach to the surface of biofilm-covered mortar and the E. coli biofilm was still present after biogenic acidification.

This paper presents piezoelectric-based passive/active methods to reliably detect and quantify defects in mass concrete or grout structures. A dual-mode sensing methodology that makes use of both passive acoustic emission detection and active ultrasonic wave evaluation methods utilizing piezoelectric sensors is investigated. Two types of piezoelectric sensors (PES) transducers are used for acquiring the passive and active signals, respectively. A novel imaging method is developed to map and locate the acoustic emission source caused by the damage growth in the subject structure. Active sensing is further used to evaluate the growth of the damage. A proof-of-concept test using simulated damage, a pencil lead break for acoustic emission, and a drill hole of various diameters for crack growth has been conducted to show the effectiveness of the present passive/active methods. The methods have also been applied to detect and evaluate crack growth caused by stepwise loading. The work presented in this paper lays the foundation for further development of a dual-mode sensing mechanism for in situ crack growth detection and evaluation in massive grout or similar material structures.

Strain-controlled cyclic simple-shear tests were performed on silica sand with radial strain measurements. The specimens were tested under a constant $K_0$ condition and subjected to cyclic loading and postcyclic monotonic loading. Threshold cyclic shear strain, volumetric strain, secant shear modulus, and damping ratio are investigated. Generally, the volumetric strain behavior in this study agreed well with literature findings that were investigated using the conventional cyclic direct simple shear test (without radial constraints). Radial strain during monotonic simple shear (postcyclic loading) was found to be a good parameter in monitoring the onset of flow slide in cohesionless soil. The concept of threshold cyclic shear strain, ${\gamma }_t$, was adequately applied in assessing the specimen volume change. Dynamic engineering properties, including equivalent shear modulus and damping ratio, were also studied. The damping ratio was found to decrease when the cyclic shear strain amplitude was greater than 2%. Possible reasons for the decrease in damping were explored.

A magnesia-phosphate cement (MPC) paste based on magnesia and potassium dihydrogen phosphate (${\mathrm{KH}}_2{\mathrm{PO}}_4$ or PDP) was prepared with the additions of dipotassium hydrogen phosphate (${\mathrm{K}}_2{\mathrm{HPO}}_4$ or DHP) and borax as set-retarders. The resulting materials were characterized in terms of their setting characteristics, strength properties, hydration products, and microstructures. The replacement of PDP by DHP was found to increase the setting time and reduce the intensity of the exothermic reactions during the initial setting and hardening stages. When the replacement percentage did not reach 50%, substitution of dipotassium hydrogen phosphate for potassium dihydrogen phosphate in the MPC paste could strike a good balance between the speedy strength gains and delayed setting time. The setting time of the MPC system increased from 5 min (without DHP addition) to 180 min with PDP replaced by DHP completely. The addition of borax also led to an extension of the initial hardening period, as indicated by reductions in the early values of compressive and flexural strengths. The phase of hydration product analysis indicated that no new phase appeared with the addition of DHP, only that more unreacted magnesia appeared with increasing DHP contents. The microstructural characteristics of the materials produced were strongly dependent on the level of DHP and borax employed.

The aim of the present paper was to study the effect of incorporating rubber aggregates and acrylic or EVA polymers on the properties of cement mortar exposed to acid (HCl, ${\mathrm{H}}_2{\mathrm{SO}}_4$, ${\mathrm{HNO}}_3$) and elevated temperature conditions. Compressive and bending strength tests, water absorption test, mass measurements, and visual inspection were performed. Impact-echo and impedance spectroscopy methods were used to investigate the effect of heat exposure. The use of rubber aggregates led to reduction of strength values and water absorption. The use of polymeric admixtures further decreased water absorption and inhibited compressive strength loss and delayed mass loss when the specimens were stored in acid solutions. The acoustic and electric measurements showed that the use of rubber aggregates or both rubber aggregates and polymers led to reduction of absorption frequency or relative permittivity, respectively. The drop of frequencies was attributed to the formation of microcracks, as well as to decomposition and brittleness of rubber aggregates and polymers. The elevated temperatures resulted in permittivity reduction. The final stage observed after heating at 400°C was the carbonization of the used polymers.

The sensitivity of the fatigue resistance of surface hot-mix asphalt (HMA) mixes is evaluated for three primary design variables. Aggregate type, binder type, and binder content as well as their interaction have been quantified with respect to their effects on HMA fatigue life, rutting resistance, and stiffness. The objective was to optimize the design by extending fatigue performance while reducing the confounded negative effect on rutting resistance. Two aggregate types were used in the evaluation. Two binders of the performance grading (PG) 64-28 were also employed: a modified binder that meets national specifications and an unmodified binder at two binder levels (optimum and optimum plus 0.5%). Aggregate texture was compared visually using high-resolution scanning electron microscopy (SEM) images. The results showed that the value of modifying the binder to produce softer mixes can be compromised when a high-friction aggregate is used due to the irregular shape of the texture, which produces stiffer mixes. A slight adjustment to the amount of binder ($+0.5\%$) can decrease this effect. Superior HMA fatigue performance was exhibited by the regular 12.5 aggregate and the modified binder at the optimum binder content plus the additional 0.5%. This conclusion was reached through the integration of the positive effects of the investigated variables, which revealed only an insignificant reversible impact on rutting resistance. The findings of this study can therefore be considered a guide for designing HMA with superior fatigue performance for use in pavement design.

Use of high performance concrete (HPC) with locally available supplementary cementitious materials (SCMs) has been increasing the world over. The difficulties associated with different indigenous cementitious materials lies in variation in its physical/chemical/mineralogical properties which may greatly influence the time-dependent properties like shrinkage and creep in HPC. A reasonably accurate estimation of actual shrinkage and creep is an important design parameter to ensure that structures built in such concrete perform satisfactorily especially in long-term, and it does not exhibit unduly large deformation or any distress like cracking during its anticipated service life. Further, very old and limited percentage of NU-ITI/RILEM data are for concrete with SCMs, and, hence, all the existing prediction models based on regression analysis of entire/partial data may not ensure satisfactory prediction of shrinkage and creep of modern HPC, in general, and especially for local geographic conditions. Towards this, four different HPC mixes of M50 grade using different SCMs, namely fly ash (FA), silica fume (SF), and ground granulated blast-furnace slag (GGBS) along with ordinary portland cement (OPC) have been prepared to investigate the microstructural and micromechanical concrete properties.

The adhered cement mortar in coarse aggregates and fines from demolished concrete has the potential to induce a residual cementing property upon recycling. A procedure for quantifying the contribution of recycled fines to the strength gain within the new mortar matrix is proposed. The strength gain is found to be more significant in recycled aggregates and fines from brick aggregate concrete than in those from stone aggregate concrete. Isothermal calorimetry measurements indicate the existence of large heat flows immediately after wetting and a prolonged initial reaction period during the hydration of recycled fines because of the presence of unreacted cement compound fractions and depleted amounts of gypsum. This phenomenon has been further confirmed, particularly in recycled fines from brick aggregate concrete, through electron microscopy observations of the formation of new gel structures caused by rehydration. The chemical compositions determined using two independent methods indicated possible interactions between CH (the hydration product) and pozzolan (from brick) to induce strength gain in new mortars and new concrete obtained by recycling brick aggregate concrete. This explanation is consistent with the strength test results and the evolution of the heat events observed calorimetrically.

Two types of concrete mixtures (Concrete A and Concrete B) were prepared with sands having different fineness modulus. Sand was replaced with coal bottom ash (CBA) at 20, 30, 40, 50, 75, and 100% levels in both concrete mixtures. Laboratory tests were performed to study the effect of CBA on compressive strength, sorptivity, chloride permeability, drying shrinkage, and sulfate and acid resistance of concrete. At 7 days, for both grades of concretes, concrete mixtures incorporating CBA showed lower compressive strength. At 28 days, for Concrete A, no significant effect of CBA on compressive strength was observed. However, in case of Concrete B, concrete mixtures containing more than 50% CBA displayed lower 28-day compressive strength than that of control concrete. With age, compressive strength of bottom ash concrete mixtures increased at faster rate. Bottom ash concrete mixtures displayed higher sorptivity, lower chloride permeability, and drying shrinkage. For both grades of concretes, resistance to sulfate and acid exposure of control and bottom ash concrete mixtures were almost identical. Compressive strength of concrete mixtures increased up to 180 days of immersion in sulfate solution. Under acid attack, control and bottom ash concrete mixtures experienced almost equal weight loss.

Shape memory alloys (SMAs) have attracted a great deal of attention as a smart material that can be used in various civil engineering applications. In contrast to the use of SMAs in the biomedical, mechanical, and aerospace applications, which requires mostly a small diameter of material, the larger size bars are usually needed in a structural application. It is well known that properties of large-section SMA bars are generally poorer than those of wires because of difficulties in material processing, which also increases the cost. SMA cables have been recently developed as an alternative and new structural element. This study explores the performance of large-diameter nickel-titanium (NiTi) SMA cables and their potential use in civil engineering. The SMA cable, which has a diameter of 8 mm, is composed of 7 strands and each strand has 7 wires with a diameter of 0.885 mm. The uniaxial tensile tests are conducted at various loading rates and strain amplitudes to characterize the superelastic properties of the SMA cable. An optical digital image correlation (DIC) measurement system and an infrared thermal imaging camera are employed to obtain the full-field strain and temperature fields. The cyclic tests are performed to evaluate the low-cycle fatigue characteristics of the SMA cables. Results show that large-diameter SMA cables exhibit very good superelastic properties and can be used in various real-world structural applications.

In the present study, the effects of direct current (DC) stray current on concrete structures were studied with the focus on the effect of concrete rather than corrosion of steel bars. Concrete samples were prepared with different water/cement (w/c) ratio and silica fume (SF) content were submerged in distilled water for 30 days while subjected to a voltage of 50 V direct current (VDC). The effects DC stray current on the properties of concrete were determined by electrochemical impedance spectroscopy (EIS) and rapid chloride penetration (RCP) tests. The obtained results showed that DC stray current will increase permeability of the concrete. The critical role of w/c ratio and SF additive on the degradation effects created by DC stray current was investigated. Moreover, a mechanism based on the migration of calcium and hydroxyl ions out of the pore solution and the dissolution of ${\mathrm{Ca}(\mathrm{OH})}_2$ precipitates from the hydrated phase was proposed for the explanation of DC potential on the degradation of concrete.

A number of recent studies have identified and begun to quantify increased susceptibility of the infrastructure to climate change–induced carbonation of reinforced concrete. In this paper, the results of a study are presented which uses an updated empirical model to predict the diffusion coefficient of carbon dioxide (${\mathrm{CO}}_2$) in concrete and thereafter, predict carbonation depths for a number of urban environments in the United States. Data from newer climate forecasts from the 5th Intergovernmental Panel on Climate Change assessment report are used to generate predictions for carbonation depths in four U.S. cities of varying geographic and climatic conditions (Los Angeles, Houston, Chicago, New York City). Results confirm that carbonation depths will increase in the future because of climate change. The magnitude of the increase is dependent on the climate-change scenario considered and the geographic location of the city. Whether or not the increases will require building code changes to increase concrete cover or improve concrete quality will be dependent on actual construction practices for the city in question.

Soft subgrades are not strong enough to provide the required degree of compaction for a pavement embankment’s foundation. Therefore, it is required to treat the subgrade soil or construct a working platform on top of the soft subgrade to ensure proper compaction of the subsequent layers. The constriction sizes of the granular materials used for a working platform are comparatively higher to restrict the erosion of overlying embankment materials. This condition would lead to severe material loss in the embankment layer in cases where the embankment is constructed with dispersive soil, which becomes structurally unstable in wet conditions and appears to disperse in water. This paper investigates the contact erosion failure at the foundation of a pavement embankment constructed with dispersive soil as a result of groundwater fluctuation. Experimental studies were conducted on a laboratory model test apparatus designed to simulate the conditions in the pavement embankment’s foundation. The experimental studies revealed that the magnesium dominant clayey soils also susceptible to contact erosion failure due to soil dispersion. Also, the experimental results show that even a small percentage of dispersive clay particles present in the embankment soil would influence the contact erosion failure.

This paper presents the effects of single-stage (jaw crusher alone) and two-stage crushing (jaw crusher followed by an impact crusher) mechanism on the mechanical properties of aggregates. A two-phase study was designed to investigate the effectiveness of two-stage crushing mechanism in improving the properties of aggregate and performance of asphalt mixtures. Aggregate packing, mechanical properties, and their influence on asphalt mixture performance have been discussed. Performance tests comprising stiffness, resistance to rutting, adhesion, and fatigue cracking were conducted in the laboratory. The study revealed that aggregate particles manufactured in a two-stage crushing process were more cubical in shape and exhibited better laboratory test results than single-stage crushing. Packing of aggregates using single-stage crushing could not be possible within the Bailey’s defined ratios. A reasonable relationship exists between the octahedral shear stress and the resilient modulus for both types of materials under a triaxial testing methodology. However, asphalt mixtures with aggregates from two-stage crushing showed relatively better results. Also, the variability in the performance parameters in the case of two-stage crushed materials was relatively less compared with single stage crushed materials.

An analytical model of chloride diffusion in concrete structures is derived mathematically for a condition with a square-root increase of surface chloride concentration and a decrease of chloride diffusivity in the initial exposure period. This model is validated with four sets of chloride profiles measured by other researchers on concrete samples containing a few types of cementitious materials. The validation results indicate that the new model is accurate and suitable for the abovementioned diffusion condition with the average coefficient of determination ($R^2$) between the modeled results and the measured chloride profiles being very close to 1 (i.e., $>0.971$). The model can be used to predict the chloride concentration profile after undergoing diffusion for a certain period in the initial exposure period, which can then be integrated with the profile outcomes modeled for the subsequent exposure periods with different diffusion conditions to determine the corrosion initiation period as a main part of concrete structure’s service life.

Inorganic–organic hybrid (IOH) lunar cements are processed by using a lunar soil simulant and polyethylene (PE). As the inorganic simulant grains are strongly held together by the PE binder, the IOH may be utilized as an infrastructural material on the lunar surface. With a uniform simulant grain size, the flexural strength of the IOH decreases exponentially with the binder content, quite close to the strength of samples of random simulant grain-size distribution. If the simulant grains have a two-step size gradation, the IOH strength increases significantly. Above a threshold binder content, the strength decreases only slightly as more simulant grains are added; below the threshold, the IOH becomes much weaker as less binder is used.

Fiber-reinforced concrete (FRC) is a well-recognized construction material because of its vast application in civil engineering structures. The use of steel fibers in FRC is well established in terms of reliable modeling of its mechanical characteristics; however, new fiber reinforcements also need attention. This paper analyzes the compressive stress-strain behavior of three mix types of high-strength fiber-reinforced concrete (HSFRC) having compressive strengths of 70–85 MPa and containing 1–3% volume fractions of basalt fibers. In the first mix of HSFRC, 100% cement content was utilized whereas 10% cement content was replaced by silica fume and metakaolin as replacement materials in the remaining two mixes. Based on the experimental data, an analytical model to predict the complete stress-strain behavior of HSFRC is proposed that shows good agreement with experimental results.