Journal of Materials in Civil Engineering

Lightweight concrete (LWC) has been developed and used in both structural and nonstructural applications. With an increasing demand for sustainable construction materials, geopolymer as an eco-friendly material has been intensively investigated. This study developed a newly synthesized lightweight ambient-cured geopolymer composite (LGC) by replacing natural fine aggregate with expanded polystyrene (EPS) beads at 10%, 20%, and 30% in volume for various structural or nonstructural purposes. The obtained composite was characterized with regard to its physical and mechanical properties. The interfacial area between the geopolymer matrix and EPS beads was observed. The properties of the developed LGC at fresh and hardened states, such as density, workability, compressive and splitting tensile strength, modulus of elasticity and Poisson’s ratio, were obtained and compared. The test results showed that the EPS inclusion had a significant effect on the properties of LGC. Empirical formulas for predicting the compressive strength, modulus of elasticity, and splitting tensile strength of the developed LGC are proposed.

Consolidating previous research on the development of novel microcapsules for self-healing in cementitious systems, this work forms a base for developing an implementation strategy and guidance for microcapsule-based self-healing technology. The study presents details of the first commercial deployment of this technology, as a ready-mix self-healing additive for commercial application. This involved the on-site construction of two slabs in a new development at the University of Cambridge. This paper describes the optimization of the mix, the structural concept and design, and processing and casting procedures. Prior to application, the compliance and compatibility of the healing additive with the concrete according to specifications and requirements of the design were investigated, validating the use of the developed system. These were complemented by large-scale laboratory testing of the healing efficiency under damage scenarios identified as critical for the on-site application. The performance of the site installation was monitored over 12 months through a combination of nondestructive testing methods. Results are presented with durability indicators confirming the in situ enhanced performance of the proposed self-healing system.

This paper presents the combined effect of the mechanical treatment of recycled aggregate (RA) and the use of silica fume (SF) in the concrete mixes. In the first step, the RA is treated by the optimized ball mill method (oBMM) to decrease mortar content. In the second step, the SF is used to enhance the negative effects of the attached old mortar (AOM) that has remained in the RA. In this method, natural aggregate (NA), RA, and treated RA (tRA) at various ratios (20%–40%–60%) with 0%–5%–10% SF are used in the mixes. After 28 days, tests are carried out on the specimens. The results show that the mechanical treatment followed by the SF combination significantly enhances the performance of recycled aggregate concretes (RACs). Satisfactory test results are generally obtained for treated recycled aggregate concrete (tRAC) produced with up to 60% tRA and 10% SF. This improvement can be explained as the consequence of the removal of AOM by oBMM and eliminating the adverse effects of the remaining part of AOM in tRA by SF addition in concrete.

The concept of utilizing industrial wastes for road construction can be materialized only by evaluating the field performance of roads constructed with these wastes. The present study encompasses the laboratory investigation of steel slag–fly ash–lime (SFL) mix substantiated by field evaluation of flexible pavement test sections constructed with SFL mix in the base layer. Based on grain size analysis and unconfined compressive strength (UCS) test, 75% steel $\mathrm{slag}+19\%$ fly $\mathrm{ash}+6\%$ lime mix was chosen as a potential replacement for wet mix macadam (WMM) in the base layer of flexible pavement. The UCS test results were supported by the shear strength parameters and resilient moduli of optimum SFL mix. The superior stiffness characteristics of the SFL mix obtained in laboratory investigation were validated with a detailed structural evaluation of flexible pavement test sections constructed with 150 and 250 mm thick SFL base. Stiffness-based quality control approach was adopted during the construction of test sections through light weight deflectometer (LWD). SFL base layers exhibited higher in situ stiffness when compared to that of WMM. From the structural evaluation of test sections with falling weight deflectometer (FWD), sections with SFL base layer exhibited lower peak deflections than that of conventional WMM. The back-calculated elastic modulus computed from FWD test for SFL base layers was more than five times that of WMM. Furthermore, test sections with SFL base layer showed a service life ratio up to 2.6 and a notable cost saving up to 15% compared to conventional WMM layer.

Fatigue damage is one of the main distresses responsible for the deterioration of asphalt roads. Self-healing, occurring during rest periods, has been shown to increase the total number of loading cycles. The increase is assumed to depend on the time at which healing is induced and the healing duration. In the first damage stage, in which damage is caused by thixotropy, self-heating and permanent deformation, the recovery is equal to the reversible phenomena thixotropy and self-heating. In the second and third damage stages, the closure of cracks starts to dominantly contribute to the gain of additional loading cycles. The healable crack volume depends on the healing method and healing duration, and includes aspects of the crack type. If the healable volume is insufficient to completely close cracks, the healing efficiency decreases due to exponential crack growth. Other occurring phenomena related to the healing process, like thermal degradation, could lead to a further increase in loading cycles at the expense of other asphalt performance aspects. The heterogeneity of asphalt introduces uncertainty into measurements. Hence, the optimal healing time to induce healing for a maximum extension of loading cycles can be determined only in a range.

Artificial neural network (ANN)-based dynamic modulus $|{\mathrm{E}}^{*}|$ models were evaluated on South Carolina’s asphalt mixtures, the majority of which contained recycled asphalt pavement (RAP). These ANNs contained similar input variables as the NCHRP 1-40D and Hirsch regression models and were implemented in the neural network toolbox of MATLAB version R2018b. Two previously published ANN-based $|{\mathrm{E}}^{*}|$ models were also evaluated on the same database. Most ANNs in the literature have been shown to predict $|{\mathrm{E}}^{*}|$ with good success; however, they have not been validated outside of their original studies. The results showed that (1) ANN-based $|{\mathrm{E}}^{*}|$ models performed significantly better than regression models; (2) ANNs with few input variables (either $V_a$, $V_{beff}$, and $G_b^{*}$ or VMA, VFA, and $G_b^{*}$) highly predicted $|{\mathrm{E}}^{*}|$ with ${\mathrm{R}}^2>0.99$ on testing; (3) ANNs can accurately predict $|{\mathrm{E}}^{*}|$ of recycled asphalt mixtures; (4) the validation performance of the two published ANNs on South Carolina’s asphalt mixtures was ranked fair; and (5) locally customized ANNs are more accurate in the estimation of $|{\mathrm{E}}^{*}|$ than globally calibrated ANNs or regression models.

Desulfurized rubber asphalt (DRA) is a good environmentally friendly road construction material, but its high-temperature performance is relatively insufficient compared to ordinary rubber asphalt (RA). Therefore, in order to make full use of its environmental protection features and overcome its shortcomings in high-temperature performance, polyphosphoric acid (PPA) was used to modify DRA to prepare composite modified asphalt (PPA-DRA). First, RA, DRA, and PPA-DRA were prepared in this study, and their high-temperature performance and fatigue properties were compared and analyzed by a temperature scanning test and multistress creep recovery test (MSCR). Then, their low-temperature performance was also compared and analyzed by using a bending beam rheological test (BBR). Finally, the modified mechanism of PPA-DRA was revealed by the FTIR test, thermogravimetric analysis (TGA), and microswelling model. Results show that compared to RA and DRA, PPA-DRA performed better both at high and low temperatures but worse at fatigue resistance, and it can be applied to a wider range of traffic grades. However, PPA-DRA and DRA are more susceptible to aging than RA, and the elastic component in PPA-DRA increases greatly due to aging. According to the strategic highway research program (SHRP) specification, PPA-DRA, DRA, and RA can be graded as PG82-34, PG76-28, and PG76-28, respectively. Also, the FTIR test in conjunction with TGA proves that PPA-DRA exhibits better high-temperature performance than DRA and RA from the microscopic perspective, and its modification process is of chemical modification; the swelling model shows that compared to RA and DRA, PPA-DRA shows the largest number of micelles and the best combination between modifier and asphalt molecules, which promotes the formation of a dense spatial network structure and makes the asphalt structure more stable.

The introduction of the Superpave gyratory compactor (SGC) to pavement laboratories was a large step for the design process of hot mix asphalt (HMA). Considering the similarities between HMA and roller compacted concrete (RCC), the use of SGC in the design work of RCC pavement can offer many advantages. This study covers a wide range of RCC mixtures that can help to set the limits of using SGC for RCC mixture design. Therefore, a detailed experimental matrix was developed by taking various mixture parameters and gyration levels into account. Moreover, four different RCC mixtures determined on the basis of optimum mix designs were also produced by vibratory hand roller in order to simulate the field compaction conditions in the laboratory. The SGC results showed that for the same gyration level, the compaction ratio changes when the mixture is changed. The results also concluded that the gyration level for the same mixtures was the least significant factor affecting the mechanical performance. Hence, SGC is more effective in predicting the behavior of the fresh RCC. On the other hand, the mixtures with similar compaction ratios compacted by SGC and hand roller resulted in a similar strength level. Therefore, for RCC specimens produced by the SGC method, targeting the sample density (i.e., compaction ratio) is recommended due to its ease of applicability under field conditions rather than making a design based on the number of gyrations as used in conventional SGC applications.

Marginal hard asphalt possesses high stiffness and modulus; however, due to poor ductility at low temperature, it was seldom applied into road structures. Increasing asphalt content seemed to be an effective way to minimize the thermal cracking problem of hard hot-mix asphalt (HMA). Therefore, three types of methods (Groups 2–4) aiming to improve hard asphalt content were designed and compared with the traditional method (Group 1). Specifically, Groups 2 and 3 were designed with coarser gradation and lower gyration levels ($N_{\mathrm{des}}$), respectively, and Group 4 was designed following the enrobé à module élevé 2 (EME2) method. The high- and low- temperature, fatigue, modulus, and cracking performance were then conducted for each group. It can be seen that with the increase of asphalt content, the low-temperature strain increased in all three groups, of which Groups 2 and 3 improved more significantly. In addition, with the coarser gradation or lower $N_{\mathrm{des}}$, the high-temperature and cracking resistance of hard HMAs was lost to some degree; however, they can still compete with traditional neat HMAs. The hard HMAs designed with EME2 method performed excellent dynamic modulus and rutting resistance. Moreover, the hard HMAs designed with EME2 method and lower $N_{\mathrm{des}}$ showed a surprising improvement in the fatigue life. These results may contribute to the better use of hard HMAs.

The service life of RC is dependent upon the superior nature of concrete and its overall quality and excellence as a suitable cover material. Concrete acting as cover material is the only means by which destructive agents or other elements can access or infiltrate a structure, resulting in corrosive damage to rebar and causing other types of damage. As a liner, the controlled permeable formwork (CPF) is an active technique that enhances concrete as a cover material. Moreover, this liner allows for air and water that is trapped inside to drain or spill out from the concrete’s surface while retaining small particles and cement. Accordingly, this not only minimizes the porosity of the surface area of concrete, but it also helps to improve or enrich the actual content. However, it also reduces the size and proportion of the water-to-cement ratio (w/c). This paper aims to demonstrate the effect of CPF liner with respect to the durability properties and service life of reinforced/strengthened concrete. To this end, concrete samples were cast in relation to the impermeable formwork (IMF) and CPF liner using three (3) w/c ratios—0.48, 0.41, and 0.31. Experimental tests were then conducted at different stages to determine rapid chloride penetration, chloride ingress, chloride diffusion, and accelerated rebar corrosion. The findings from the experimental investigations revealed that CPF concrete acquired excellent resistance against the ingress of chloride ions ranging between 47% and 80%. Furthermore, the results showed that the service life of concrete cast against CPF liner was extended by around 2.1 times compared to IMF concrete.

Shear strength and rutting characteristics play a vital role in the serviceability and performance of interlocking concrete block pavement (ICBP). The objective of the present research study is to evaluate the shear stress behavior of the interlocking paver block–bedding sand interface using the laboratory large-scale direct shear test. The research includes analyzing the influence of parameters such as interlocking paver block shape, laying angle, and gradation of bedding sand on the shear stress behavior of ICBP. Optimization of the influential parameter is analyzed by the response surface methodology using expert software. The relative movement between the blocks during the shear mechanism is assessed by the image processing technique using well-known mathematical software and is validated from the readings measured using a Vernier caliper. Numerical simulation is carried out using professional engineering software to validate the laboratory test results. Combined rutting of the interlocking paver block and bedding sand is estimated from the derived shear test results. The test results prove that the ICBP, when laid with zigzag shape over Zone II bedding sand, perpendicular to the traffic movement, exhibits better shear strength and lower rutting.

Anomalous localized corrosion of submerged steel H-piles was detected in a Florida bridge. Microbiological analysis at the site indicated a high population of sulfate-reducing bacteria (SRB). The steel piles coincidently also had heavy marine growth, which can affect the corrosion process. As part of research to identify the role of macrofoulers on the aggravation of microbiologically-influenced corrosion (MIC), the objective of the work was to identify the influence of crevices created by the macrofoulers to facilitate proliferation of SRB and development of MIC. Steel coupons were immersed at three Florida bridge sites. Localized corrosion developed under the marine fouling coinciding with high sessile SRB populations. Crevice conditions with different interactions with the bulk solution can develop. Crevice environments associated with well-adhered barnacles would have less interaction with the bulk solution than that of the poorly-adhered and interlayered barnacles or marine flora. Aeration levels would be similarly affected. Laboratory experiments were made in solutions inoculated with SRB and with idealized crevices. The lab testing provided verification that sequential injections of nutrients and viable SRB allowed for SRB populations to be sustained. MIC developed in the environments representative of the occluded regions under fouling organisms.

This study evaluates the effect of limestone mineral addition in cement on the efficacy of supplementary cementitious materials (SCMs) in mitigating alkali-silica reaction (ASR) using the accelerated mortar bar test (AMBT). Mortars with and without SCMs were prepared by substituting portions of 0% limestone general portland (GP) cement with increasing amounts of limestone. Mortars with SCMs (25% fly ash or 65% slag) exhibit negligible expansion regardless of the limestone content in the binder, whereas mortars without SCMs exhibit high and almost identical expansion for all limestone substitutions. The expansion results show that limestone does not aggravate ASR, has no detrimental effect on the efficacy of SCMs in ASR mitigation, and likewise has no observable ASR-mitigating properties under the test conditions. The calcium silicate hydrate ($\mathrm{C}\text{-}\mathrm{S}\text{-}\mathrm{H}$) composition is not affected by the amount of limestone, which suggests that limestone has no influence on the alkali uptake in the $\mathrm{C}\text{-}\mathrm{S}\text{-}\mathrm{H}$. This is supported by the pore solution analysis results where SCMs (both fly ash and slag) have drastically reduced the pore solution alkali concentration over time, whereas limestone substitution only resulted in an alkali reduction equivalent to the substitution (dilution). Moreover, the carboaluminate phases formed when limestone is present were observed to decompose under AMBT conditions; thus, their influence on ASR mitigation is not possible to discern from this study.

It is well known that cold mix cement emulsified asphalt (CMCEA) exhibits good mechanical performance even when paved at room temperature. In this study, the compactibility and mechanical properties of CMCEA specimens were studied using a Superpave gyratory compactor. To analyze CMCEA compaction dynamics, two indices based on indexes of compaction quality (ICQ) and parameters of the compaction process (PCP) were considered. ICQ included the compressive strength and air voids, while PCP included the compaction energy index and compaction rate. Tests were conducted on CMCEA specimens to estimate the effect of process variables, such as compaction temperature, time interval before compaction, and gyration parameters, on ICQ and PCP. It was determined that CMCEA could be molded satisfactorily at temperatures below 40°C. Experimental results showed that the compressive strength and densification of CMCEA specimens were positively correlated in the range of °C10–40°C and negatively correlated beyond 40°C. Process variables play an important role in controlling the compaction characteristics, such as the compressive strength and air voids. Furthermore, choosing a suitable time interval before compaction (TIBC) at a given compaction temperature helps in saving compaction energy and achieving an appropriate compaction rate. To achieve a CMCEA compressive strength $>2.4\mathrm{MPa}$ and densification $>92\%$ at 25°C, as mandated by practical design requirements, the TIBC, number of gyrations, and gyration angle were optimized at 12–35 min, 140–160, and 1.15°, respectively. The method used to determine these parameters and the obtained optimal values serve as a benchmark for actual pavement construction.

This paper investigated the red ceramic waste originated from damaged sintered bricks as a potential source of pozzolanic mineral addition for portland cement. Physical, chemical, and mineralogical characterization of the red ceramic waste and clay raw material was conducted. The pozzolanic activity was identified through electrical conductivity, modified Chapelle, and Frattini tests, and verified by the evolution of axial compressive strength and apparent porosity in cementitious mortars produced with 30% of waste replacing portland cement. Results showed a low content of kaolinite (22%) in the clay used to produce the bricks and the complete decomposition of kaolinite after sintering. The red ceramic waste can be classified as a mineral addition with variable pozzolanicity by its ability to absorb calcium ions and pozzolanic material with medium reactivity, based on the ability to fix lime. The partial replacement of cement with 30% waste assigns a pozzolanic character to portland cement. The assessment of compressive strength and porosity in mortars over time supported the potential of using comminuted red ceramic waste as pozzolanic mineral addition in portland cement.

Targets made by ultra-high-performance concrete (UHPC) and functionally graded cementitious composite (FGCC) were manufactured and their dynamic behaviors were researched under the coupling of penetration from $14.5\text{-}\mathrm{mm}$ bullets and TNT explosions. The FGCC targets including the antipenetration layer, crack resistance layer, and spalling resistance layer were made of coarse aggregate reinforced UHPC, hybrid fiber–reinforced UHPC, and steel fiber–reinforced UHPC, respectively. The dynamic fracture of UHPC and FGCC targets were investigated and the penetration and explosion process were researched using the smoothed particle hydrodynamics (SPH) method. The crater sizes, fracture patterns, and attack damage of UHPC and FGCC targets were measured respectively. Results show that the resistance of FGCC against penetration and explosion was increased by the reinforcement of alumina aggregates. The minimum penetration depth of the FGCC target decreased greatly compared with the UHPC target. The dynamic processes of UHPC and FGCC subjected to penetration and explosion were simulated by the SPH algorithm. The simulated crater sizes were close to the experimental data. Penetration models were proposed to calculate the crater depths of UHPC and FGCC based on the Forrestal model. The deviations between the penetration models and experiments were small.

P-wave velocity ($V_{\mathrm{p}}$) is a significant parameter in characterizing the physical and mechanical properties of rock. The $V_{\mathrm{p}}$ of rock under different stress conditions will vary greatly. This study investigated the transformation of $V_{\mathrm{p}}$ under a single load and unload condition. Six concrete specimens were used. The unload level was 0 (uniaxial compression test), 0.1, 0.3, 0.5, 0.7, and 0.9 times the uniaxial compressive strength. Ultrasonic tests were carried out on the test processing. The loading and unloading process was analyzed as an integral part, and the process of secondary loading to destruction was divided into three sections—the compaction section, the elastic section, and the crack extension section—and the test results were analyzed using the least-squares regression method. Quadratic, linear, and logarithmic function relationships were found between axial stress and $V_{\mathrm{p}}$ at different sections throughout the test, and different polynomial relationships were found between the energy and $V_{\mathrm{p}}$ before and after the peak of $V_{\mathrm{p}}$. A polynomial relation was found between the energy and $V_{\mathrm{p}}$. In addition, the total input energy, elastic energy, and dissipated energy had a linear/quadratic function relationship.

The main purpose of this study is to investigate the effect of wastes, namely plastic wastes, iron wire, and cast-iron powder, as a potential substitute material on the behavior of environmental-friendly sintered clay bricks to reduce environmental pollution and production cost. Twenty groups of mixtures were tested to obtain precise results for the compressive strength, flexural strength, weight per unit area, apparent porosity, freeze-thaw resistance, ultrasonic pulse velocity (UPV), water absorption, and initial rate of absorption tests. The results indicated that no single trend could be identified to measure the effect of additional materials on the improvement or deterioration of mechanical and durability properties. The results revealed that an increment in the content of plastic particles up to 4% by weight resulted in a decline in water absorption, whereas an increase in the content of coarse plastic particles raised water absorption. It was found that specimens including regular iron wire and cast-iron powder demonstrated higher compressive strength rather than the specimens with plastic and irregular. The results of the freeze-thaw test revealed that most of the specimens satisfied the requirement of ASTM, and those incorporating cast-iron powder had the best results. Due to the low specific gravity of plastic wastes, the weight per unit area of specimens mixed with them was lower than that of specimens with iron wire and cast-iron powder, leading toward a reduction in the seismic weight of buildings. It concludes that the best improvement in the flexural strength of bricks was achieved by a 40% replacement of cast-iron powder, compared with the reference specimen.

Reclaimed asphalt pavement (RAP) has been widely implemented in asphalt pavement construction due to its cost benefits along with its reasonable engineering performance. With the trend of higher RAP applications, it is more critical to consider the complicated interactions between RAP and virgin binders. An unreasonable assumption of the full blending of RAP material could lead to many issues, such as insufficient virgin binder content and poor pavement durability. This paper focuses on the determination of virgin binder grades and content during the design of a high RAP content mixture by considering RAP blending effectiveness. By integrating the blending ratio parameter, a modified blending chart is proposed to determine the PG grade of the virgin binder, and a partial blending method is used to estimate the optimum virgin binder content. It is found that when an 83% blending ratio is considered in the 40%-content RAP mixture design, the differences of the determined virgin binder grade from the traditional blending chart and modified one is within 6° (one PG grade). If the blending ratio is 56% or less for a 40%-content RAP mixture, the required base binder needs to drop one PG grade (6°). Moreover, the partial blending method typically demands $0.5\%–1\%$ more virgin binder than the Superpave volumetric method, which could result in significantly improved cracking performance without jeopardizing its rutting resistance.

In this work, the influence of a naphthalene sulfonate–based superplasticizer on the initial corrosion of galvanized steel bars in the simulated concrete pore solution was studied. The initial corrosion process of the galvanized steel in solution with superplasticizer was first monitored. The inhibition effect of the protective layer formed by the superplasticizer and the protective property of the calcium hydroxyzincate (CHZ) passive layer were defined. Scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDS) was used to observe the surface morphology of the CHZ passive layer. The results showed that the addition of superplasticizer delayed the initiation of the corrosion process of galvanized steel bar and inhibited the hydrogen evolution. The protective property of the CHZ layer on galvanized steel varied with the concentration of superplasticizer. The inhibition effects of the superplasticizer on the initial corrosion will be beneficial to the quality of the steel–concrete interface.

Foamed cement paste has been used increasingly as a backfill material in geotechnical engineering applications, such as embankments, tunnels, and retaining walls. However, limited studies have focused on the influence of void structures of the foamed cement paste on its macromechanical behavior. This study used X-ray computed tomography (X-CT) to investigate the void structures of foamed cement paste and their influence on the macromechanical properties (strength and modulus). The test results showed that the void volumes had a unimodal distribution. The reduction in the density of the specimen indicated more large voids and a wider distribution of void sizes; however, surrounded-type voids were dominant in terms of percentage of total volume. The sphericity of the voids ranged from 0.1 to 0.6, indicating their highly irregular shapes. Sensitivity analysis showed that the volume of the surrounded-type voids played a primary role in the compressive behavior of the foamed cement paste, the void shape was the secondary influence factor, and the void size was the tertiary influence factor.

Laboratory experiments were used to determine the suitability of raw industrial by-products obtained within the United Kingdom that are being taken to landfill sites and develop a hydraulically bound cementitious material for applications in road (base), foundation, and subgrade in pavement construction. The by-products were predominantly sourced locally. Tests were carried out to determine the mechanical stability of the by-product binders and performance determined in strength development by time. High-pressure permeability tests were performed to determine the permeability of the materials, and frost susceptibility tests were conducted to determine the freeze–thaw resistance of the materials. Compressive strength tests were conducted at 7, 14, 28, 90, and 180 days of age. Strength development on the hydraulic paste was slow during the early stages of hydration for mixtures containing 40%–60% ground granulated blast furnace slag (GGBS). After 28 days and up to 90 days when the ultimate strength of the hydraulic paste was achieved, strength increased with the presence of GGBS of up to 60%. Ternary mixtures with proportions of 20% plasterboard waste gypsum (PWG); 20% reclaimed asphalt filler (RAF), 60% GGBS, and 10% vitamin B5 gypsum (V-B5G); 30% RAF; and 60% GGBS attained the highest compressive strengths of 41 and 40 MPa, respectively, at 90 days. One of the dominant factors that influenced the strength was the presence of calcium sulfate, ${\mathrm{CaSO}}_4$ (${\mathrm{CaO}+\mathrm{SO}}_3$), in the PWG and V-B5G materials; calcium silicate, ${\mathrm{CaSiO}}_3$ (${\mathrm{CaO}+\mathrm{SiO}}_2$), in the GGBS; and pozzolanic activity (${\mathrm{SiO}}_2{+\mathrm{Fe}}_2{\mathrm{O}}_3{+\mathrm{Al}}_2{\mathrm{O}}_3$) in the RAF. The results suggest most of the mixes in the groups are suitable for use as road (base) and foundation materials.

Steel slag, an industrial waste generated in the production of steel, has cementitious properties due to high contents of free CaO. In the present investigation, different bacteria were isolated from steel slag and tested for their ability to produce the enzyme urease, which is involved in ${\mathrm{CaCO}}_3$ precipitation. One of the bacterial isolates, Staphylococcus pasteurii SS9, was selected further, based on its high urease activity to treat the steel slag for stabilization. Bacterial treated steel slag at 30% and 50% was used as a replacement to aggregate in cement mortar and cured in bacterial solution. The mortar specimens without bacterial treatment as well as without steel slag served as controls. After 7-day and 28-day curing, the compressive strength and permeability properties of the mortar specimens were evaluated. The 30% slag–modified mortar specimens treated with bacteria improved the strength by 15.9% and 12.8% at 7 and 28 days compared to the specimen without bacterial treatment. The compressive strength of 50% slag–modified mortar specimens with bacterial treatment showed only 6.3% and 1.8% improvement compared to the specimen without bacteria at 7 and 28 days, respectively. About eight times less water was absorbed in 30% and 50% slag–modified mortar specimens treated with bacteria than the control specimens. Scanning electron microscopy–energy dispersive X-ray spectroscopy and X-ray diffraction analysis confirmed the mineralization of ${\mathrm{CaCO}}_3$ on the surface of bacterial treated mortar specimens. Bacterial treated steel slag can effectively be used as a partial replacement of fine aggregates in cement mortar in the construction industry, and the current study provides an efficient way to utilize this waste material in cement mortar.

Foamed concrete has attracted increasing attention in civil engineering due to its unique properties. Permeability is one of the significant material properties that governs its long-term durability. This work presents a method to explore the permeability characteristics of foamed concrete based on X-ray microcomputed tomography (micro-CT) image reconstruction technique and Simpleware version M-2017.06 software. The pressure and water flow distributions in foamed concrete were obtained, and the permeability of the foamed concrete with different densities was calculated. The numerical simulation results showed that the proposed method can be used to predict the permeability of foamed concrete. The main factors that affect the permeability of foamed concrete are discussed. A power law model is established to reveal the relationship between the porosity and permeability of the foamed concrete, and the connectivity of pores was labeled to explain why the permeability of three different location calculation models are not the same under the same density conditions. Furthermore, the influence of boundary conditions on the calculation results of the permeability was analyzed, and a comparison of the 2D and 3D results were carried out to determine whether it is necessary to reconstruct the 2D CT images into 3D pore-scale physical models.

Based on the limited information on the tensile stress–strain relationship of ultra-high-performance concrete (UHPC) with treated fibers, the objective of the present research is to experimentally investigate the flexural behavior of UHPC with the treated fibers using a four-point flexural test. The steel fibers inside the UHPC matrix were aligned using an improved device and chemically treated using Zinc phosphate (ZnPh) simultaneously. Also, image analysis was used to obtain the fiber orientation factor with and without the fiber treatments. Two existing inverse analysis methods (namely point-by-point inverse analysis and a five-point inverse analysis) were used to derive tensile stress–strain relationships from the flexural test data. Then, comparisons between the predicted and experimental tensile response were conducted. The results showed that the flexural cracking strength, ultimate strength, and corresponding deflections were enhanced by 39.3%, 95.3%, and 124.5%, respectively, in UHPC with chemically treated and aligned fibers as compared to the reference specimen. The five-point inverse analysis cannot predict the tensile stress-stain relationship of UHPC with or without aligned fibers, while the predicted results from the point-by-point inverse analysis agree well with the experimental results for UHPC without fiber alignment. However, the testing tensile response of UHPC with aligned fibers can be predicted by the point-by-point inverse analysis after a ratio of fiber orientation factor of UHPC with fiber alignment to that without fiber alignment is incorporated to scale the tensile response.

Efflorescence has been an ongoing issue facing the development of geopolymers; excess efflorescence may disturb the stability of the binder microstructure. This paper investigates the controlling of efflorescence in a calcined kaolin-based geopolymer binder cured at ambient temperature. Silica fume (SF) and ordinary Portland cement (OPC) were used at different replacement levels (0, 5, 10, and 15 wt.%) to control the efflorescence via microstructural refinement. A digital camera was used to observe the extent of efflorescence on the surface of geopolymer mortars. Several techniques were performed to understand the effects of SF and OPC on the microstructural changes of the geopolymer binders. The bicarbonate and carbonate ion concentrations, as well as the alkalinity of leaching solutions, were measured. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and x-ray diffraction (XRD) tests were used to better understand the microstructural changes. The results revealed that using SF at 5wt.% or OPC at 10% reduces the efflorescence extent with improved compressive strength.

The addition of polymer emulsion in cement paste improves concrete impermeability. However, a high polymer emulsion content (usually 10%–20% of the mass of cement) is typically required to significantly improve the performance of concrete, which might increase material costs and decrease the compressive strength of concrete. This study seeks to develop a better method for improving concrete impermeability without significantly decreasing the concrete strength at a relatively low polymer emulsion content. In this study, the aggregates were pretreated with asphalt emulsion to concentrate hydrophobic asphalt film in the interfacial transition zone (ITZ). The effects of asphalt emulsion-coated aggregate (ACA) on the transport and mechanical properties of concrete were investigated. The aggregates were pretreated with asphalt emulsion at dosages of 0.1%, 0.4%, 0.7%, and 1.0% mass of the coarse aggregates, and the replacement percentages of normal coarse aggregates (NCA) by ACA were 10%, 30%, 50%, 70%, and 90%. Water absorption (WA) by capillarity, compressive strength, and stress-strain curves were obtained. The porosity and microhardness of ITZ around ACA were also investigated. The results indicated that the porosity of ITZ within $20\mathrm{\mu m}$ of the aggregate surfaces increased over two times, and its microhardness decreased by approximately 30% when the coated asphalt emulsion content increased to 0.7% and 1.0%, thus decreasing the concrete strength by approximately 20%. The WA rate was influenced by the mutual effects of the hydrophobicity of asphalt film and increased porosity in ITZ. The proper replacement percentage of NCA by ACA (30%) improve concrete impermeability and reduce concrete brittleness without significantly decreasing the concrete strength at a relatively low asphalt emulsion content (0.4% mass of coarse aggregates).

This study investigated the hydric and durability performances of compressed earth blocks (CEBs) stabilized with calcium carbide residue (CCR) and rice husk ash (RHA). Dry mixtures were prepared using kaolinite-rich earthen material and 0%–25% CCR or $20:0\%$ to $12:8\%$ CCR:RHA of the weight of the earth. Moistened mixtures were manually compressed to produce CEBs ($295\times 140\times 95\mathrm{mm}$). Stabilized CEBs were cured at $30°\mathrm{C}\pm 5°\mathrm{C}$ and wrapped in plastic bags for 45 days. The cured CEBs were dried and tested for water absorption and other indicators of durability. Unstabilized CEBs immediately degraded in water. The stabilized CEBs were stable in water, with a very low coefficient of capillary absorption ($<20\mathrm{g}/{\mathrm{cm}}^2·{\min }^{1/2}$) and excellent durability indicators. They resisted erosion at a standard water pressure (50 kPa) and at a pressure of 500 kPa. The coefficient of surface abrasion improved far higher than the $7{\mathrm{cm}}^2/\mathrm{g}$ recommended for the construction of facing masonry. It also increased after wetting-drying cycles and correlated with the evolution of compressive strength. This correlation can be used as the nondestructive test of stabilized CEBs.

In this paper, the influence of different temperatures and ground-granulated blast-furnace slag (GGBFS) content on the compressive strength and shrinkage bahavior of roller-compacted concrete (RCC) was explored. For this purpose, four RCC mixes incorporating 0%, 20%, 40%, and 60% of GGBFS were prepared. The mixes were subjected to three temperatures, 25°C, 50°C, and 70°C. The results show that RCC gained strength more rapidly at higher curing temperatures. Shrinkage results showed that temperature had a direct impact on shrinkage strain development, with lower final shrinkage strain values at higher exposure temperatures. This was due to a loss of interlayer water at a faster rate in the early stages itself. Also, incorporation of GGBFS led to marginally higher shrinkage strain, which was compensated at higher exposure temperatures. Strength and shrinkage results were further confirmed at the microscopic level by scanning electron microscopy and thermogravimetry analyses. Based on the experimental results, a multivariable model incorporating the effect of temperature, time, and GGBFS percentage was developed for the prediction of shrinkage strain of RCC. The regression coefficient of the model was higher than 0.95 for all mixes, indicating that the proposed model can estimate shrinkage strain within 95% of the prediction band.

Agro-waste ashes can be used as supplementary cementitious materials in concrete. Although many studies have been reported on the use of rice husk ash as a pozzolan, only limited studies are attempted on the use of rice-straw ash in concrete. The composition of rice straw and the influence of thermochemical processing on the amorphous nature and microstructure of rice-straw ash are reported in this study. Moreover, compressive strength, water penetration test, and rapid chloride permeability tests were conducted for rice-straw ash blended concrete. Results from the study indicate that rice-straw ash obtained from pyrolysis temperatures up to 700°C were amorphous and contained reactive silica. From considerations of strength, workability, and durability, 10% rice-straw ash is observed to be the optimum level of replacement. Rice-straw ash blended concrete with 20% replacement level exhibited better performance against water penetration and chloride ingress than control concrete.

This paper investigated hollow glass microspheres (HGMs) on the density, mechanical properties, and durability of ultralightweight cement composites (ULCCs). The influences of HGMs on the microstructure developments of ULCCs were also studied. The results indicated that the ULCCs had a 1-day density ranging from 778 to ${948\mathrm{kg}/\mathrm{m}}^3$ and 28 days compressive strength ranging from 22.9 to 33.1 MPa. The density of ULCCs was decreased with the increasing amount of HGMs, while the mechanical properties were reduced accordingly. The newly developed ULCCs with an HGM-to-binder volume ratio of $5:1$ and water-to-binder of 0.58 has a 1-day density of ${778\mathrm{kg}/\mathrm{m}}^3$ and 28 days compressive strength of 22.9 MPa, whose specific strength was ${0.029\mathrm{MPa}/\mathrm{Kg}/\mathrm{m}}^3$. Furthermore, the obtained ULCCs showed a good resistance to chloride ion penetration. The microstructure demonstrated that the pozzolanic reaction of HGMs resulted in denser hydration products, which exhibited beneficial impacts on the durability of ULCCs.

The purpose of this research is to study the accumulative effect of repetitively adding groundwater on the engineering properties of coarse grain salinized embankment fill material. Large-scale compression and engineering characteristics tests were carried out on different salt content samples. Based on the laboratory test results, the influence factors on the engineering properties were analyzed by repetitively adding groundwater with ${\mathrm{SO}}_4^{2–}$ or ${\mathrm{CL}}^{–}$. With the increase of added water containing ${\mathrm{SO}}_4^{2–}$ or ${\mathrm{CL}}^{–}$, the compressive deformation of tested samples showed a trend of dramatically increasing at the beginning followed by gradually decreasing, while the collapse deformation of the samples increased continuously. The coefficient of compressibility showed a typical three-stage variation law, regardless of the salt type of added water. With the decrease in temperature (simulating the cooling period during construction), the excess content of ${\mathrm{SO}}_4^{2–}$ in the water resulted in an increase of salt expansion in the samples, while shrinkage behavior was observed with the excess of ${\mathrm{CL}}^{–}$ in the water. Thus, an obvious accumulative effect in the salt expansion of the sample was observed. With the increasing addition of water containing ${\mathrm{SO}}_4^{2–}$ or ${\mathrm{CL}}^{–}$, the collapse deformation of the samples increased continuously. Moreover, the effects of added water with ${\mathrm{SO}}_4^{2–}$ or ${\mathrm{CL}}^{–}$ on the engineering characteristics of the samples were discussed from the following perspectives: salt accumulation, distribution of salt in the soil, interaction of salt ions, and dissolution of soluble salt. It is further shown that even a small amount of soluble salt in groundwater will have a significant impact on the engineering properties of the coarse grain saline soil with an accumulative effect by repetitively adding groundwater.

Due to the increase in the number of vehicles on the road, the amount of used vehicle tires has also increased exponentially. Making tires into rubber powder and adding them into asphalt, which forms asphalt rubber as a kind of asphalt binder of asphalt pavement surface, is an effective way of using waste tires. Styrenic block copolymers (SBS) can improve high-temperature performance of asphalt as a kind of polymer additive. Comprehensive recycling rubber powder and SBS in asphalt mixture can not only make use of waste tires, but also expand the application of waste materials and compose environmentally friendly mixture for the asphalt pavement surface, which improves service life and service function of asphalt pavements. In order to evaluate the high-temperature performance improvement of composite-modified asphalt material, three different asphalt binders and two different asphalt mixture types were selected and the related tests were conducted. The results show that for the mixture of SMA-13 and SMA-16, composite-modified asphalt mixture had better high-temperature performance than asphalt rubber mixture, but worse than SBS asphalt. In addition, the crumb rubber (CR)/SBS composite-modified asphalt had a large internal friction angle, which could give better cohesive force for aggregate gradation. Finally, CR/SBS composite-modified asphalt had the smallest reduction rate from 50°C to 70°C. This study identifies that compound action of rubber powder and SBS is an optimal choice for asphalt pavement surface in high-temperature season. It provides a wider range of applications for asphalt rubber in the road construction field, which also realizes waste cyclic utilization and environmental protection.

This paper systematically performed fatigue crack propagation (FCP) tests to investigate the corrosion fatigue crack propagation (CFCP) behavior of HRB400 steel bar. The fatigue loading scheme involved the constant amplitude loading and stepwise decreasing amplitude loading. The load ratio, the ratio of the minimum load to the maximum load, was designed as 0.1, 0.2, 0.3, 0.5, and 0.7. The test environments included air, pure water, 3.5% NaCl solution, and an electrolytic erosive environment. The FCP rate and threshold stress intensity under the test conditions were obtained and compared. An empirical model for predicting the CFCP rate was proposed, where the influences of load ratio and environment type were incorporated. The proposed model was validated using the test results. The results showed that the CFCP behavior of the rebar showed the feature of true corrosion fatigue. Increasing the environmental erosion level and load ratio increased the FCP rate and decreased the threshold stress intensity, indicating that the steel bar’s resistance to fatigue crack growth decreased. The predictions of the proposed model agreed well with the test data. This paper provided experimental and theoretical references for the corrosion fatigue life prediction of concrete structures.

Waste management is a crucial issue facing modern society. The generation of sewage sludge is increasing annually due to the urbanization and improvement of sanitation systems of cities. The construction sector has emerged as a solution for the elimination of waste due to the enormous volume of materials that this sector can absorb. This paper evaluates the pozzolanic activity of sewage sludge ash (USSA) obtained following an uncontrolled-combustion process, a simple and economic procedure. Compressive strength of Portland cement/USSA mortars with 5%–25% by weight USSA were evaluated. Calcium hydroxide/USSA and Portland cement/USSA pastes were chemically and physically characterized through thermogravimetric/differential-thermogravimetric (TG/DTG), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses. The increase in the replacement of Portland cement by USSA is associated with an increase in the compressive strength of mortars. These values for USSA containing mortars cured for 90 days were in the range of $49.6–55.4\mathrm{MPa}$, higher than the one reached by the reference mortar. According to the microstructural analysis, the increment on the compressive strength can be attributed to the formation of hydrated products (C─ S─ H, C─ A─ S─ H, and C─ A─ H) by the pozzolanic reaction of USSA.

The aim of this study is to investigate the cause of the self-cementing properties of recycled aggregates used for pavement base. Clay bricks were added to the recycled aggregates to study the pozzolanic reactions. The evolution of the mechanical performances of the materials was investigated in the laboratory (California Bearing Ratio) and in the field (plate test). Both tests showed that initially, the mechanical performances of recycled aggregates are equivalent or even lower than those of natural aggregates. However, recycled aggregates become much better than natural aggregates with time. Therefore, setting tests, microcalorimetric analysis, and two pozzolanicity tests (pH evolution and consumption of ${\mathrm{Ca}}^{2+}$ ions) were carried out in a laboratory in order to explain the observations made on the test beds. The microcalorimetric analysis showed that there is only a slight hydraulicity due to residual anhydrous cement content in recycled aggregates. However, the other tests highlight that the presence of clay bricks particles in recycled aggregates results in pozzolanic reactions that can explain the time-evolution of mechanical performances. This study suggests that recycled aggregates have a high added value when they are used as pavement base.

To facilitate rapid hardening of concrete and to increase production rate, particularly at the precast manufacturing site, the use of electrolyzed water containing molecular hydrogen (${\mathrm{H}}_2$) and hydroxyl ions (${\mathrm{OH}}^{-}$) would be an effective alternative to the existing chemical set accelerators. In this study, electrolysis of water was performed by applying direct current (DC) voltage for 30 min using Pt and Ti electrodes separated by a polymeric membrane. Two types of concrete specimens were prepared using normal distilled water (CC) and 30-min electrolyzed water (30MEC) to compare the impact of electrolyzed water on the performances of concrete. The results revealed that the use of electrolyzed water for the fabrication of concrete (30MEC) not only improves the physical properties (e.g., bulk densities, apparent porosity, and water absorption) but also enhances the compressive strength by approximately 14.4%, 9.3%, and 4.9% and flexural strength by (approximately 16.7%, 12.8%, and 5.3%) than that of the concrete fabricated using normal water (CC) cured for 3, 7, and 28 days, respectively. The accelerated chemical reaction of cement particle due to the presence of ${\mathrm{OH}}^{-}$ ions in the electrolyzed water may lead to improve the physical and mechanical properties of concrete. Finally, the plausible mechanism behind the early setting and strength gaining capability of electrolyzed water-based concrete has been explained based on the Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Mercury intrusion porosity (MIP) analysis.

A dynamic message sign (DMS) is made up of a display, cabinet sheet aluminum skin, and internal structure along with electrical components. The aluminum skin is connected to the internal structure usually with a welded connection; however, adhesive or chemical bonding can be used instead for the connection between these two components. The goal of this paper is to examine the tensile and shear strengths along with other mechanical properties of adhesives used in the DMS under varying environmental and geometrical conditions. Adhesive tensile and shear specimens with different widths were tested according to accepted standards after conditioning them in different temperature and humidity conditions. Numerous data resulting from the tests were analyzed through graphical comparisons and statistical analysis so as to explore the effect of the considered parameters on tensile and shear strengths. As part of the statistical analysis, response surface metamodels (RSMs) were utilized not only to determine statistically significant parameters affecting the strengths, but also to develop separate regression models for the tensile and shear strengths. The highest decrement in the tensile stress was found to be 7.1%, 19.9%, and 7.9% with the increase in conditioning temperature, conditioning humidity, and specimen’s width, respectively. Owing to the effect of increases in conditioning temperature, conditioning humidity, and specimen width, the shear stress was increased most by 10%, 7%, and 19.3%, correspondingly. Key findings revealed that an increase in conditioning humidity decreases the tensile strength. The RSM model–based analysis also found conditioning humidity to be the most significant parameter negatively affecting the tensile stress because a probability value of 2.529% was observed from the RSM model. Finally, this work found adhesive or chemical bonding to be a possible substitute to welding for assembly of the DMS.

An autoregressive (AR) model for the simulation of modulus of elasticity (MOE) fluctuations along hardwood boards without pronounced knot periodicity is presented. The model is calibrated based on contiguous, localized (100 mm gauge length) empirical MOEs from European white oak boards. The calibration involves the computation of the sample autocorrelation function (SACF). For this computation, the stationary data resulting from a two-step transformation method are used: (1) first, board-internal MOE normalization suppresses the interboard bias; and (2) the rather left-skewed normalized data are described by a log-gamma distribution, which is then mapped to $\mathcal{N}(0,1)$ to obtain the needed stationary data. A first-order AR process suffices to accurately describe the data and is thus used as a basis to simulate MOE profiles, followed by the sketched transformation procedure in reverse order. The quality of the simulated MOE profiles and of the methodological approach is shown by comparison with the experimental MOE profiles. It was found that the simulation model correctly reproduces the statistical information of the MOE variations while also producing very plausible profiles, with similar characteristics as the empirical MOE profiles. This model can be used to better study the size effect of glued-laminated timber by means of numerical simulations.

In this paper, the stress-strain response of two extrusive volcanic igneous rocks, e.g., compact basalt (CB) and volcanic breccia (VB), under a high rate of loading is studied experimentally and numerically. The dynamic characterization of rocks is done for five different specimen sizes using a split Hopkinson pressure bar (SHPB) device with a $76\text{-}\mathrm{mm}$ diameter. Based on the test results, the response of the two rocks is compared, and suitable specimen dimensions to be used in SHPB testing are decided for both the rocks. Furthermore, simulations of SHPB tests with a strain rate dependent Johnson-Holmquist (JH-2) model are performed, and numerical simulation results are compared with experimental data to determine the parameters of the JH-2 model for the two rocks. Thus, the parameters obtained are used in the analysis of a tunnel subjected to a 20 kg trinitrotoluene (TNT) explosion in CB and VB, and the simulation results are compared. The suitable specimen sizes for characterizing CB specimens are proposed to be 54 mm in diameter, with a 0.5 slenderness ratio, and 76 mm in diameter, with a 0.3 slenderness ratio. For VB rock, the suitable specimen sizes are 54 mm in diameter, with a 0.2 slenderness ratio, and 76 mm in diameter, with a 0.2 slenderness ratio. The dynamic increase factor varies from 1.69 to 6.77 for CB and from 1.09 to 4.83 for VB. In the blast analysis for tunnels in the two rocks, nearly 4 times higher stress and 4.4 times lower displacement are observed at the tunnel crown in CB as compared to that in VB.

Granular soils are sensitive to internal erosion due to the presence of lesser fines and need to be stabilized to improve their geoengineering properties. An investigation is made to explore the efficacy of fly ash-slag (FA-GGBS) geopolymer in stabilizing granular soil through a set of experimental studies. The experimental program focused on compaction characteristics, unconfined compressive strength, bearing resistance, and durability of geopolymer stabilized granular soil to assess its suitability as a construction material. Microstructural analysis has been carried out and correlated with strength development. Based on the test results, a maximum unconfined compressive strength of about 7 MPa and California bearing ratio (CBR) ranging from 52% to 416% is obtained. The geopolymer stabilized soil showed excellent stability against wetting–drying and freezing–thawing cycles, slaking water, and aggressive chemical environments. The microstructural developments are greatly influenced by the geopolymer content and curing period, indicating the formation of hydration and geopolymeric reaction products.

The microbial-induced carbonate precipitation (MICP) technique has been increasingly employed for erosion mitigation and stabilization of sandy slopes. Biocementation can improve the strength and stiffness of unsaturated sand. In this study, the performance of a new biogrouting method (i.e., surface percolation) for sandy slopes under unsaturated conditions was investigated. Model-scale laboratory tests were conducted on MICP-treated coastal slopes to assess the erosion resistance to wave actions. The spatial distribution of ${\mathrm{CaCO}}_3$ in the biocemented sandy slope was measured, which can reveal the mechanism and characteristics of biocementaion of sandy slopes. Results show that the slope surface experienced no obvious erosion after the implementation of MICP treatment for four cycles. The lowest degree of saturation was observed at the slope crest, and it increased to the highest value at the slope toe. Similarly, the erosion resistance was also doubled from the slope crest to the slope toe due to flow of water/solution in the slope in the downward direction.