Journal of Materials in Civil Engineering

A foamed alkali-activated material (FAAM) based on tungsten mining waste (TMW) and municipal waste glass (WG) is fabricated by using aluminum powder and organic surfactant foaming agents. The compressive strength and density of the FAAM are investigated in terms of different parameters of production and formulation, including curing temperature as well as the dosage of ${\mathrm{Na}}_2\mathrm{O}$, foaming agent, foam catalyzing agent, and stabilizing agent. FAAM made with aluminum powder consists of smaller open macropores and exhibits higher compressive strength compared with FAAMs with larger closed macropores obtained by organic surfactant counterparts. The final aluminum powder–based FAAM reaches a 7-day compressive strength in excess of 3 MPa and a density below $0.7\mathrm{g}/{\mathrm{cm}}^3$. The implementation of an appropriate amount of foam stabilizer leads to a further 15% increase in compressive strength, 6% reduction in density, and a thermal conductivity below $0.1\mathrm{W}/\mathrm{mK}$. The FAAM explored in this study represents an ideal material for building envelope insulation.

Diffuse waves have been proved to be more sensitive to medium interior changes than direct waves due to much longer traveling path and propagation time in media. This makes diffuse waves a useful tool in nondestructive evaluating and testing (NDT) applications. The diffusion equation is an analytic model for describing diffuse wave propagations, which provides a basis for most diffuse wave–based NDT approaches. When applying the diffusion equation, the diffusion coefficient ($D$) is usually assumed to be independent of medium changes and measurement locations. However, the heterogeneity and inhomogeneity inherent in multiple-composite concrete materials cause the change of diffusion coefficient when subjected to load and interior structural changes, especially for large concrete structures. In this research, a four-bending test on a full-size reinforced concrete beam was conducted, and the $D$ values were evaluated under various load levels and multiple receiver locations. The results show that $D$ in general increases with the increase of load, and the change is affected by microcracks in concrete. This study of the relationship between the diffusion coefficient and stresses/structural changes provides a novel approach for evaluating medium stress and damages. In addition, the work also suggests a potential method to improve current diffuse wave–based NDT techniques by considering $D$ variations caused by stresses and defects.

This study evaluates the effect of zinc oxide nanoparticle (ZnONP) on permanent deformation of modified bitumen. The moisture susceptibility was also evaluated in hot-mix asphalt (HMA) prepared by nano-ZnO modified bitumen. Bitumen modification was conducted using a high shear mixer at contents of 1%, 3%, and 5% by weight. Permanent deformation was evaluated using the $G^{*}/\sin \delta$ parameter obtained from dynamic shear rheometer (DSR) test results for modified bitumen. Compaction was conducted by a Superpave gyratory compactor, and moisture susceptibility was using the modified Lottman procedure. The dispersion of nanomaterials was analyzed by scanning electron microscopy (SEM). The best performance was obtained by ZnONP 5% modification. The performance grade was determined as PG 64-22 after all modifications. Optimum bitumen content (OBCs) were decreased by modification except the 1% mix (which had the same results as the reference sample). Asphalt mixtures were found to be highly resistant against moisture for all nanomodifications. Lower performance was determined just for the 1% ZnONP modified HMA as compared to the reference sample. After SEM analysis, the dispersion of nanomaterials in the mixture was homogenous. Up to 4 μm agglomeration was displayed in the mix.

This study assessed the impact resistance of self-consolidating engineered cementitious composite (SCECC) using the American Concrete Institute (ACI) Committee 544’s repeated drop-weight impact test and flexural impact loading test. The investigation also evaluated the compressive strength, splitting tensile strength, flexural strength, and modulus of elasticity of the tested mixtures. Fly ash (FA), which is typically used in common SCECCs, was partially replaced by slag (SL), silica fume (SF), and/or metakaolin (MK). Also, the microsilica sand (SS), which is the primary aggregate used in SCECCs, was replaced by crushed granite sand (CS) of different sizes to develop different SCECC mixtures. Standard SCECC mixture (made with only FA), vibrated engineered cementitious composite mixture, and traditional self-consolidating concrete (SCC) made with 10 mm coarse aggregate were tested for comparison. The results indicated that combining SL, SF, or MK with FA in SCECC mixtures can create composites with improved mechanical properties, adequate ductility, and enhanced impact resistance. The highest improvement in the impact resistance in both drop-weight and flexural impact loading tests was obtained when 15% to 20% MK was combined with FA. SCECC containing CS provided comparable performance with that of SCECC made with SS, indicating promising potentials for developing cost-effective composites. The impact resistance results in both drop-weight and flexural impact loading tests also indicated that SCECC mixtures exhibited significantly higher impact resistance compared with their SCC counterpart mixtures with comparable compressive strengths.

Chip seals constitute an alternative for maintaining and preserving asphalt pavement structures and constructing surface courses for low-traffic pavement structures. However, poor adhesion quality in the asphalt binder–aggregate interface of the chip seal can produce its accelerated deterioration and damage to vehicles due to the loss of aggregates. The main objective of this paper is to validate the feasibility of applying conventional tests (plate stripping and boiling water) to assess the adhesion quality of chip seals through the correlation of the results with those gathered from energy parameters (derived from surface free energy). Achieving this objective included the analysis of 135 combinations of aggregate–asphalt residue (recovered from asphalt emulsions). Corresponding results showed that there is no correlation between the plate-stripping test and the boiling-water test nor between their results and the energy parameters. However, the results suggest the possibility of optimizing the adhesion quality through the energy parameters, which can contribute to improving the chip seals design and field performance.

The objectives of this paper are twofold: (1) Investigate the low-temperature reversible aging discrepancy mechanism of the asphalt binders with similar regular low-temperature performance grade; and (2) evaluate the effects of commercial wax on the reversible aging properties of asphalt binder. First, the mechanisms of reversible aging in asphalt binder were reviewed. Then, regular performance grading tests and extended bending beam rheometer tests were used to comprehensively evaluate the effect of base asphalt binder type and commercial wax content on regular performance and reversible aging properties. Moreover, a modulated differential scanning calorimetry test was applied to analyze the phase transition, crystallization, and melting behavior of selected asphalt binder samples before and after long-term conditioning. The results showed that commercial wax-based warm mix additive increased the degree of reversible aging (physical hardening) in asphalt binder. There is a strong relationship between endotherm peak enthalpy and commercial wax content. For asphalt sample with a higher degree of reversible aging (physical hardening), glass transition temperature ($T_{\mathrm{g}}$) increased and two separate amorphous domains formed with the extension of conditioning time.

The design of greener materials is of great interest to develop eco-efficient construction systems, causing less environmental impact and following circular economy criteria. Accordingly, the current study aimed to analyze the viability to incorporate glass waste—from construction and demolition—in gypsum composites, promoting a circular economy in the building construction sector. Gypsum-based composites were formulated using different percentages and particle sizes of glass waste, and samples were prepared. These samples were tested in the laboratory, and the following characteristics were determined: dry density, surface hardness, mechanical strength, water absorption by capillarity, and thermal conductivity. Analysis comparing these composites to reference gypsum without additions showed that it is viable to prepare gypsum composites with the addition of glass waste to reduce water absorption by capillarity, improve mechanical strength, and increase surface hardness. All composites comply with the minimum requirements set by regulations. Therefore, these composites can be applied in the manufacturing of gypsum prefabricated elements or as interior coatings requiring special surface hardness, improved water behavior, and mechanical strength properties.

High-temperature rheological properties of asphalt binders are important in asphalt mixture production and compaction. In this study, the high-temperature rheological properties of asphalt binders with polymeric, warm-mix, and rubber particulate additives were examined at different temperatures, shear rates, and shear modes. Most of the tests were conducted using a concentric cylinder measuring system with a dynamic shear rheometer. The test results provide a full picture of the rheological behaviors of those binders at or approaching the mixing and compaction temperatures. Test results indicate that shear rate dependency of modified asphalt binders at high temperatures is generally not significant and is related to binder type. The shear thinning behavior is more noticeable for binders with particulate modifiers than for those with styrene-butadiene-styrene (SBS) polymers. The apparent shear thinning behavior shown at high shear rates at relatively low temperatures may be attributed to discontinuity developed during the test. The test results also suggest that there are interactive effects between warm-mix additive type, binder type, and test conditions (temperature and shear rate). Hence, the effects of warm-mix additives may need to be considered at different combinations of temperatures and shear rates. The complex and rotational shear viscosities were found to be comparable at lower test frequencies (or shear rates), but not at higher ones, and the responses of different binders to shear modes were found to be different. Although this study does not aim to develop new criteria for mixing and compaction temperatures for asphalt mixtures with modified binders, the insights gained are expected to contribute to the body of knowledge in this area.

This paper studies the effect of fly ash on rheological properties of magnesium oxychloride cement (MOC) paste. Six different dosages of fly ash (0%, 15%, 20%, 25%, 30%, and 35% by weight of MgO) samples are prepared to investigate the rheological properties of fly ash–magnesium oxychloride cement (FA-MOC) paste. The effects of fly ash on fluidity, setting times and mechanical properties of MOC paste are measured. Phases and microstructures of FA-MOC paste are analyzed by X-ray diffraction (XRD) and scanning electronic microscopy (SEM). An optical microscope is used to evaluate the flocculation of fresh FA-MOC paste. The results reveal that fly ash can improve fluidity and retard the setting time of MOC paste. The water-absorbing ability and the morphology effect of fly ash have combined effects on the rheological properties of FA-MOC paste. At the same time, the results show that fly ash used in MOC paste does not change the phases composition of hardened paste, but increases the amount of $5\mathrm{Mg}{(\mathrm{OH})}_2·{\mathrm{MgCl}}_2·8{\mathrm{H}}_2\mathrm{O}$ (Phase 5). However, fly ash weakens the structure of hydration products and results in poor mechanical properties of MOC paste.

This research investigates the effects of aggregate proportioning on the basis of theoretical particle packing models and verifies the predicted results with experimental data from compaction of concrete aggregates. The experimental, theoretical, and computational approaches are compared on the basis of the packing of the binary and ternary blends. The results illustrate that the Toufar packing model can predict the maximal packing degree of various binary and ternary blends of aggregates, and the sequential packing algorithm can closely predict the particle size distribution and the packing degree of aggregate assemblies. It was demonstrated that the suggested experimental procedure with Vebe apparatus can be used to determine and verify the aggregate packing degree, reaching the compaction degree values predicted by theoretical and computational models.

Concrete is one of the most widely used materials in building structures; hence, improving its durability is important. Corrosive agents affecting concrete durability find their way into concrete through surface cracks and pores. However, concrete can be made resistant to such destructive agents if calcite sediments are allowed to form in the concrete by certain types of bacteria. This study investigated the effects of certain bacterial agents on the electrical resistance, chloride penetrability, and steel corrosion of concrete specimens. The water absorption and compressive strength of the specimens were evaluated. For this purpose, concrete specimens were made using two different bacteria (S. pasteurii and B. subtilis) and two different mixture proportions. The specimens were cured for 28 or 91 consecutive days in two types of media (a solution of urea–calcium chloride and a solution of urea–calcium lactate). Results showed that the water absorption and chloride penetrability of the specimens decreased but their compressive strength and electrical resistance increased when bacteria, especially S. pasteurii, was used in the concrete. Moreover, the reinforcement provided enhanced resistance against corrosion in concrete specimens containing S. pasteurii and subsequently cured in the urea–calcium lactate medium.

This study investigated the changes in the performance and microstructure of carbonated MgO samples subjected to 40°C–550°C in water, oven, and furnace conditions. Although sample strength remained relatively stable until 80°C, an obvious reduction was observed in higher temperatures. This performance decline was attributed to the changes in the content and morphology of the strength providing carbonate phases (hydromagnesite). Phase quantification results revealed lower hydromagnesite content with smaller crystal sizes at $\ge 150°\mathrm{C}$. The decarbonation of hydromagnesite, followed by dehydration of brucite to MgO at higher temperatures of 550°C, revealed the relationship between the stability of major phases and sample performance.

Aggregate occupies at least three-quarters of the volume of asphalt mixture and can significantly affect the performance of pavement. The geometrical morphology influences the slippage and interlock among aggregates for resisting and distributing applied loads. In recent years, the discrete-element method (DEM) has been employed for simulation of asphalt mixture structure. This paper introduces an approach for simulation of aggregate and asphalt mixtures using parameterized shape and size gradation. Both the plane geometry factor (PGF) and the section aspect ratio (SAR) were employed to describe the three-dimensional (3D) geometric characteristics of aggregates. A numerical technique of aggregate models was implemented with probabilistic parameters depending on statistical results of PGFs and SARs. The 3D numerical model of asphalt mixtures was assembled with three different components, and was validated by uniaxial compression tests via comparison with the laboratory result. It was found that the PGF and SAR are appropriate to describe the three-dimensional features of aggregate shapes, because a simplified space object can be described by a two-dimensional (2D) graphical projection and a vector scalar corresponding to the space vector. Probability distribution curves of PGFs and SARs between coarse aggregates were in concordance with the Gauss-type function, because their correlation coefficients were all greater than 95%. It was verified that the developed clumping algorithm of aggregates was reasonable in terms of the shape and size gradation. Based on the parallel-bond model and Burger’s model, the results of virtual tests were in good agreement with those of laboratory uniaxial tests. The angularity (PGF) of aggregates has a beneficial effect on the strength and stability of asphalt mixtures, whereas the flat-elongated feature (SAR) has a negative effect on the strength and stability of asphalt mixtures.

Mass stabilization, a ground improvement solution used for construction in peatlands, involves mixing suitable dry binders into the peat, increasing strength and stiffness and reducing permeability. A previous pilot study of the carbonation process in stabilized peat showed that it could be a net sink of ${\mathrm{CO}}_2$, because the binder takes in ${\mathrm{CO}}_2$ from the atmosphere and any ${\mathrm{CO}}_2$ released by oxidized peat due to carbonation. In this study, a closed-chamber method was applied to stabilised peat specimens over a 6 month period to assess the factors affecting ${\mathrm{CO}}_2$ intake rate. The studies revealed that an increase in cement content and a larger surcharge contributed to a larger ${\mathrm{CO}}_2$ intake rate. These rates decreased logarithmically with time, and surcharge was found to be less influential over time. The ${\mathrm{CO}}_2$ intake rate reduced when the atmospheric ${\mathrm{CO}}_2$ concentration reduced, and the replacement of cement with ground granulated blast-furnace slag had a negative effect on the ${\mathrm{CO}}_2$ intake rate due to its lower carbonation potential. Furthermore, a high water table resulted in a decrease in the ${\mathrm{CO}}_2$ intake rate. These laboratory results have highlighted that dry soil mixing has a minimal on-site impact in environmental terms, allowing geotechnical engineers to make more informed decisions on the suitability of this technique for construction projects.

The electrical resistivity of hardened cement-based materials was measured in this work by a modified noncontact electrical resistivity measurement (MN-CM). The resistivity was further processed to compute the chloride diffusion coefficient ($D_{\rho }$) using the Nernst-Einstein equation. Also, the rapid chloride migration test (RCM) was carried out to obtain the chloride migration coefficient ($D_{\mathrm{RCM}}$), and the relationship between $D_{\rho }$ and $D_{\mathrm{RCM}}$ has been established. The obtained $D_{\rho }$ was further correlated to the pore structure parameters characterized by low-field nuclear magnetic resonance (NMR) spectroscopy. The results show that the $D_{\mathrm{RCM}}$ is more sensitive to the change of pore connectivity, while $D_{\rho }$ is more sensitive to the change of porosity. The $D_{\rho }$ is smaller than $D_{\mathrm{RCM}}$ since it strictly follows the Nernst-Einstein equation while RCM neglects the other driving forces such as capillary sorption and concentration gradient. It is concluded that the proposed MN-CM can obtain the chloride diffusion coefficient of saturated cement-based materials in a quick, stable, and reliable manner.

To determine the mechanical behavior of rigid polyurethane composite aggregate (RPC) in compression, uniaxial compressive tests of RPC specimens, which were molded by reaction injection, were conducted under different specimen densities. The failure behavior of the specimens was observed by macroscopic compression tests and microscopic scanning electron microscope (SEM) tests. Based on the classical mechanical constitutive model of ordinary concrete and RPC uniaxial compression tests results, a three-stage model considering specimen’s density was proposed to describe the RPC’s mechanical behavior. Although this model is more suitable for single-sized RPC, a mechanical theoretical model that is suitable for different grades of RPC was proposed based on damage mechanics theory. The three-stage model has fewer parameters and higher accuracy for single-sized RPC’s stress-strain curves than does the mechanical theoretical model. The latter model is suitable not only for single-sized RPC but also for different grades of RPC.

In recent years, energy harvesting technologies have been applied in pavement engineering. Piezoelectric energy harvesting in pavement aims to take advantage of the vehicle load on a road. Most of the existing theoretical and experimental research focused on the materials, structures, and shape of the energy harvesters to improve the efficiency of the output energy. However, few investigations have analyzed the compatibility of piezoelectric energy harvesters (PEHs) and pavement. This study investigated the influence of PEHs on the structural response of asphalt pavement. Three-dimensional (3D) tire–pavement interaction finite-element models with and without a PEH were constructed according to a previous demonstration project. Several critical points within the pavement structures were selected and their mechanical responses induced by the passing tire were compared and discussed. A parametric study analyzed the pavement responses to different traffic speeds, tire loads, and bonding conditions between the PEHs and asphalt layers. Two potential optimization solutions for the PEH were explored. The results showed that the influence of the PEH on the asphalt pavement performance is significant in terms of the horizontal and vertical strains and von Mises stresses. A PEH causes potential permanent damage initiation in its adjacent area within the pavement structure. The maximum values of the horizontal tensile strains appeared at the bottom of the asphalt surface course in all pavement models with a PEH. These conclusions offer basic information for improving the practical design of PEHs in asphalt pavement.

Owing to their high chemical resistance, alkali-activated materials (AAMs) may represent a promising option for repairing concrete structures affected by acidic media. However, AAMs have some technical limitations with respect to cast-in-situ applications because they require heat curing to mitigate delay in setting time, strength gain, and microstructural development at early ages. Therefore, this study investigated the performance of concrete with AAMs incorporating blends of fly ash, slag, and nanosilica cured at normal temperatures and exposed to very aggressive (10%) sulfuric acid environments. In addition to full immersion exposure for 18 weeks, a combined exposure was implemented to simulate field conditions involving alternating wetting–drying and freezing–thawing cycles combined with sulfuric acid attack. The evaluation criteria were based on visual assessment, neutralization depth, mass loss, and bond strength to substrate concrete in repair prototypes. In addition, the alterations of the microstructure of specimens were analyzed by mineralogical, thermal, and microscopy studies. The results showed that concretes prepared with fly ash–based AAMs with a small amount (6%) of nanosilica or (10%) slag without heat curing showed improved durability in sulfuric acid environments in terms of reduced penetrability of acidic media, low mass loss, and increased bond strength to substrate concrete with time. Thus, such AAMs could be a viable option for cast-in-situ repair applications of concrete elements in acidic environments.

The drying process of concrete is a complex unsteady heat and mass transfer process that is greatly affected by the drying temperature. The influence of the drying process on the drying characteristics and strength of concrete must be investigated. Concrete specimens were dried under various temperatures, namely, 60°C, 85°C, 105°C, 120°C, and 150°C, to obtain the criterion for the dry state of the concrete specimens and optimum drying control condition. An anomalous diffusion model was developed to characterize the drying phenomena of the concrete specimens. Three main results were acquired. First, the proposed model can clearly interpret experimental drying data and predict the dry state of concrete specimens. Second, drying temperature greatly affects the drying rate and dry state of the concrete specimens. Third, conducting the drying test on concrete specimens at 105°C is recommended.

Timber frame connections commonly use mortise and tenon connections secured by wooden pegs. The calculation of peg connection strength depends upon the joint dimensions, material properties of the mortise and tenon, and the bending yield strength of the peg. The purpose of this technical note was to measure the bending yield strength of a variety of pegs encompassing the range of wood species and diameters found in timber frame construction. A regression analysis of the bending yield strength data used a series of two-factor and single-factor power and linear equations using specific gravity and diameter as independent variables. A linear equation to estimate the bending yield strength was chosen based upon similarity of results and simplicity of calculation.

The literature review on existing technologies shows uncertainties in the performance of a single system for concrete curing monitoring. The project presented in this paper developed an integrated system by analyzing combined measurements of radio frequency identification (RFID) and optical fibers. Laboratory development/testing of this integrated system examined its performance. RFID tags and single-mode optical fiber cabling were embedded into seven concrete sample cylinders. Results verified that stability of RFID tag readability range and single-mode optical fiber cabling output power maintained well over a span of 28 days. Performance of this proposed system was successfully tested because both systems reached stability in the same period. For RFID signal measurements, the readability range of the tags was 1.15–2.37 m. The optical fiber system had an output power variation of 0.01 in two samples. This preliminary test demonstrated the potential of the system.

This study examined soda residue (SR) and ground granulated blast furnace slag (GGBS) to stabilize soft soil in comparison with using portland cement (PC). The shear strength of samples was measured to study the additive dosage and curing time effect on the additive performance. Microstructural investigations were conducted using pH, thermogravimetric analyses, X-ray diffraction, and scanning electron microscopy to correlate with shear strength of the treated soil. The results indicated that the presence of SR can increase the shear strength of soft soil and the optimum content is approximately 30% to yield the highest cohesion. Soil stabilization using a mixture of SR and GGBS increased shear strength as GGBS content and curing time increased. Shear strength of SR-GGBS-stabilized soil was close to that of the corresponding SR-PC-stabilized soil after curing for 28 days. The main hydration products detected for SR-GGBS-stabilized soil included calcium silicate hydrates, calcium aluminate hydrates, ettringite, and calcium chloroaluminate hydrates. The results will contribute to the use of SR and GGBS as effective stabilizers for soft soil.

This study aims to characterize both experimentally and numerically the flexural behavior of two different locally sourced granular materials stabilized with 3% general purpose (GP) cement. The four-point bending test was conducted on the compacted cement-stabilized beam specimens at various curing ages ranging from 7 to 90 days. The obtained experimental results elucidated both an exponential relation between curing period and flexural strength and a logarithmic relation between ultrasonic pulse velocity (UPV) and flexural strength for the cemented granular materials (CGMs) tested in this study. It was found that the rate of gain in flexural strength during the first 28 days is distinctly higher than that of during the subsequent 62 days. Taking into consideration the practical aspects of road operation, it is proposed that the flexural properties of CGMs, such as flexural strength, should be determined at 28 days curing age for use in pavement structural designs. In conjunction with the experimental study, a three-dimensional finite-element model of a four-point bending specimen was developed to simulate the flexural behavior of CGMs under static monotonic loading. The microplane model M7 was then implemented using commercially available software, and its parameters were calibrated (only two parameters of the model M7 were adjusted from their reference value) using the experimental flexural stress-strain response of CGMs at a 7-day curing age. The calibrated model M7 was then used to predict the flexural behavior of both CGMs at 28 and 90 day curing ages. Numerical simulations using the calibrated model M7 were shown to agree well with the flexural behavior of CGMs in experiments. This shows the capability of the calibrated microplane model M7 in simulating the flexural behavior of CGMs at various curing ages using minimum constitutive parameters.