Journal of Materials in Civil Engineering

The phenomenon of fatigue can be considered one of the main causes of asphalt surface failure. The four-point bending apparatus is a device used widely to determine the fatigue resistance of asphalt mixtures. Worldwide, there are several standard procedures that rule this test. The main difference between them is the waveform, in which the load is applied to the beam, and the failure criteria. This paper reports how the waveform—haversine or sinusoidal—affects the fatigue resistance determination of an asphalt mixture. Additionally, the impact of the obtained models was evaluated through numerical simulation, based on the required thickness of the asphalt layer from a pavement’s structure. It was concluded that depending on the loading waveform employed, the fatigue resistance results present a significant difference. Tests carried out on the four-point bending machine with haversine loading presented values of fatigue resistance much higher than the ones carried out with sinusoidal loading.

Hydrated cementitious fines can be recycled by thermal treatment ($<500°\mathrm{C}$) as an alternative binder with low energy consumption and carbon dioxide (${\mathrm{CO}}_2$) emissions during production. This paper analyzed the transformations of the phases during the dehydration and rehydration of slag–portland cement pastes using laser diffraction, surface area, X-ray fluorescence, X-ray diffraction, thermogravimetry, isothermal calorimetry, and compressive strength tests. Dehydrated slag cement fines can be rehydrated, reforming phases similar to that formed during pure hydration of clinker cement (calcium silicate hydrates, portlandite, and so on), but also other complex compounds, such as hydrotalcite (carboaluminates containing Mg). Dehydrated slag cement fines have high surface area. The heat released by rehydrated paste in the first hours is 10 times higher than that released by the hydrated paste due to the water readsorption and rebinding in the dehydrated cement phases (most of them amorphous). For similar water/binder ratios, the compressive strength of rehydrated cement paste at 28 days was about 66% that of the hydrated paste, using only approximately one-third of the thermal energy of the clinker of the cement manufacturing process.

Specimens were made of ultrahigh-performance concrete (UHPC) with two ratios of sand to cementitious materials, 0.5 and 1.25. Specimens with 0%, 0.5%, 1%, 1.5%, and 2% fiber content were prepared from each mixture. Fiber distribution in these specimens was investigated using three techniques: conventional imaging, X-ray computed tomography scanning (CT scan), and electrical conductivity. All techniques were able to determine the fiber distribution in UHPC. However, the electrical conductivity measurements required minimum preparation and were less expensive and faster compared to the other techniques. It was found that increasing the ratio of sand to cementitious material in the mixture decreased flowability and the fibers tended to settle down in a mixture with higher flowability compared to the mixture with lower flowability.

Plastic waste (PW) has long been identified among the direct and indirect primary sources of environmental pollution. Currently, global PW generation is more than 300 million tons annually and is increasing at a rate of 4% per year. Recycling has been recognized as a key technique, among others, for addressing the environmental hazards associated with PW. Prior studies on the modification of asphalt concrete (AC) using PW have been mostly about asphalt binder modification or mineral aggregate substitution for better AC properties. Several studies have focused on stone mastic asphalt concrete (SMA) or isolating recycled polyethylene terephthalate (RPET) as an aggregate substitute. In this study, a combined form of recycled plastic waste (RPW) was used as a mineral aggregate supplement in a dense-graded hot mix asphalt (HMA) AC made with RPW-modified asphalt binder. The term hybrid RPW-AC is used to refer to the HMA AC in this study. The viscoelastic performance of ACs containing combined RPW aggregates were compared with those containing RPET-only aggregates. Dynamic modulus ($|{\mathit{E}}^{*}|$) tests, flow number (FN) tests, and rutting resistance tests using an asphalt pavement analyzer (APA) were utilized to evaluate the performance of the hybrid RPW asphalt concrete mixes and were compared to fresh, RPET, and crumb rubber AC. The results showed that combined RPW as an aggregate supplement has advantages over the use of RPET-only aggregates. The hybrid RPW-AC showed superior performance compared to the reference mixtures.

Geosynthetic products are routinely used to reinforce pavement overlays to control crack propagation under repeated vehicular and varying thermal loads. Many experimental methods are available to measure the potential of geosynthetic products in controlling reflective cracks. Among all methods, the four-point beam (4PB) fatigue test is commonly used as an effective method to evaluate the performance of asphalt concrete beam specimens with geosynthetics. Three types of geosynthetic products made of GlasGrids (SGT), coir (CGT), and jute (JGT) were used to reinforce the asphalt concrete beam specimens in the current research study. Conventional linear variable differential transformers (LVDTs) were used to measure the vertical deflections during the 4PB fatigue tests. The digital image correlation (DIC) technique, being a noncontact measurement method, has undoubted advantages over the conventional measurement methods in asphalt concrete (AC) testing. The analysis of sequential images captured during the test aids in measuring the strain or displacement field over a region of interest (ROI). This method is most suitable for the study of cracks and their propagation where random damages are expected. The flexibility in postprocessing the measured data eases the analysis of results. This research study explains the different phases of the DIC method adopted for measuring the crack growth pattern during the 4PB fatigue tests on geosynthetic reinforced beams. The analysis of results showed that all the reinforcement layers assist in mitigating the cracking potential, by diverting the crack path along the interface of the geosynthetics. The parameters that influence the accuracy of the DIC analysis are also discussed in this paper.

One efficient way of recycling polymeric wastes such as crumb rubber and polyethylene terephthalate (PET) is to use them in a concrete mix. A prerequisite in accomplishing this application is to determine the general stress–strain relationship of this concrete type when subjected to fire in order to examine specific fire-performance criteria and better understand the actual behavior of structures made of it during the fire. In this research, the compressive stress–strain behavior of concrete containing polymeric recycled materials consisting of crumb rubber and PET as well as their combinations as natural sand replacements was investigated after exposure to elevated temperatures (200°C, 400°C, 600°C, and 800°C). For that purpose, the physicomechanical properties of the concrete specimens, namely, compressive strength, elastic modulus, strain at peak stress, ultimate strain, toughness, stress–strain curve, weight loss, and visual observation, were evaluated after exposure to elevated temperatures. Then a series of empirical equations were developed to predict the mechanical properties. Furthermore, a comparison was conducted between the experimental results and those predicted by international codes of practice, together with a comparison between the equations proposed here and the experimental results reported by other researchers. Finally, using the empirical equations obtained for the mechanical properties of the concrete containing recycled polymeric materials under elevated temperatures, a stress–strain model was proposed to predict the compressive behavior of this concrete, which demonstrated a good consistency with the experimental results. The results showed that as the temperature increased, a significant degradation occurred in the physical and mechanical properties of the concrete specimens. Moreover, the mentioned codes properly estimate the experimental results of compressive strength at higher temperatures and the tangential elastic modulus at all the temperatures, while they give a considerable overestimation of the strain at peak stress results.

In the interest of utilizing high-plasticity excavation soil as a replacement for fine aggregate in cement mortar, a study on the thermal treatment of soils containing 25% and 40% clay fractions was carried out. A range of tests including thermogravimetric analysis (TGA) and X-ray diffraction (XRD) were conducted to examine the transformation of fines ($\mathrm{silt}+\mathrm{clay}$) in soil at temperatures ranging from 200°C to 1,000°C. Thermally treated soils were used as fine aggregate in cement mortar, and properties such as water demand, dry density, compressive strength, and drying shrinkage were studied. The experiments were designed with the parameters treatment temperature and duration using central composite design of response surface methodology. From the test results, it was concluded that thermal treatment helps in transforming clayey soil, even high-plasticity soil, to be used as a suitable fine aggregate material in cement mortar. However, the properties of thermally treated soil highly depend on the clay mineralogy present in it.

Creep properties of asphalt binder and mastic are critically important to asphalt concrete’s high-temperature antirutting resistance. The Burgers and three element models were applied to determine the creep parameters of four asphalt binders and 24 mastics with varying filler volume fractions. The influence of asphalt binders and filler volume fraction on the creep compliance, $J$, instantaneous elastic deformation compliance, $J_e$, delayed elastic deformation compliance, $J_{de}$, viscous flow deformation compliance, $J_v$, and the proportion of $J_e$, $J_{de}$, and $J_v$ to total creep compliance were analyzed according to the model results. A simple two-point reciprocal relative creep compliance was applied to determine the critical filler volume fraction of asphalt mastics with different asphalt binders. The physicochemical interaction between asphalt binder and filler was evaluated with the Einstein coefficient, $K_E$. Based on Fourier infrared spectroscopy, four kinds of functional group indexes were calculated, and then associations of $K_E$ and the functional group indexes were determined by grey relational analysis (GRA). The results showed that filler volume fraction had a similar degree of influence on $J_e$ of the two kinds of modified asphalt mastics, but an obviously different influence on $J_{de}$ and $J_v$ of mastics with various asphalt binders. Nonrecoverable viscous flow characterized the deformation of matrix asphalt mastics. However, in modified asphalt mastics, elastic deformation played an important role in the initial stage of creep, and then the delayed elastic deformation constituted the principal component. Adding fillers caused an increase in the proportion of instantaneous elastic deformation and delayed elastic deformation, while the viscous flow deformation decreased significantly. The critical filler volume fraction was 0.273–0.426 for the four asphalt binders. Grey relational analysis results showed that the influential priority of the four functional groups of asphalt on $K_E$ were as follows: $\mathrm{sulfoxide}>\mathrm{carbonyl}>\mathrm{aliphatic}>\mathrm{aromatic}$.

This study aimed to evaluate the potential use of polyurethane solid–solid phase change material (PUSSPCM) as polymer modifier in asphalt binder. PUSSPCMs were synthesized via the two-step condensation reaction of 4,4′–diphenylmethane diisocyanate, polyethylene glycol, and 4,4′-methylenebis(2-chloroaniline). The synthesized PUSSPCMs possessed suitable transition temperature in the range of 10.9°C to 46.8°C and high latent heat enthalpy in the range of 71.68 to $73.87\mathrm{J}/\mathrm{g}$. The synthesized PUSSPCMs possessed good thermal stability even at 320°C. Furthermore, varying amounts of PUSSPCM modifiers were added to a neat asphalt binder. The viscosity of all the modified bitumen samples was lower than 2,000 cP. The addition of the PUSSPCMs did not greatly affect the penetration, softening point, and storage stability of modified asphalt. However, excessive content of PUSSPCMs adversely affected the ductility of modified asphalt. The temperature change rate of the PUSSPCM modified asphalt decreased with increasing PUSSPCM content. When the content of PUSSPCMs reached 7% by weight, the maximum temperature difference of neat bitumen specimen and modified bitumen specimen reached about 9.0°C in the laboratory.

A novel fiber-reinforced calcium silicate board was prepared from fly ash. The effects of compression pressure, pulp fiber content, and cement content on the flexural strength and thermal conductivity of the fiber-reinforced calcium silicate boards were investigated. Under optimal conditions, the fiber-reinforced calcium silicate board had a high flexural strength of 10.55 MPa and low thermal conductivity of $0.2424\mathrm{W}/(\mathrm{m}·\mathrm{K})$. The high flexural strength of the fiber-reinforced calcium silicate board was attributed to the good adhesion and penetration between fibers and the matrix, and the solidification of cement in calcium silicate board, enhancing the ability of the board to withstand the shear failure and bending force. The low thermal conductivity of the fiber-reinforced calcium silicate board was ascribed to the high porosity of the fiber-reinforced calcium silicate board and the low thermal conductivity of the porous tobermorite solid phase. This fiber-reinforced calcium silicate board has a potential application as a new building material.

Automobile exhaust emission has become one of the environmental problems that cannot be ignored. In order to improve the photocatalytic activity of titanium dioxide (${\mathrm{TiO}}_2$), graphitic carbon nitride $(\mathrm{g}\text{-}{\mathrm{C}}_3{\mathrm{N}}_4)/{\mathrm{TiO}}_2$ was prepared, and its bonding state and morphology were analyzed by microscopic characterizations. The nitric oxide (NO) removal efficiency of $\mathrm{g}\text{-}{\mathrm{C}}_3{\mathrm{N}}_4/{\mathrm{TiO}}_2$ was higher than that of $\mathrm{g}\text{-}{\mathrm{C}}_3{\mathrm{N}}_4$ and ${\mathrm{TiO}}_2$. This was attributed to the formation of a heterojunction between $\mathrm{g}\text{-}{\mathrm{C}}_3{\mathrm{N}}_4$ and ${\mathrm{TiO}}_2$ which accelerated the separation and transfer of photoinduced carriers. Because the results showed that the micropores produced by demulsification of emulsified asphalt were beneficial to the improvement of photocatalytic performance, emulsified asphalt was chosen as the carrier of $\mathrm{g}\text{-}{\mathrm{C}}_3{\mathrm{N}}_4/{\mathrm{TiO}}_2$ photocatalysts to study the influence of different application forms on photocatalytic performance of asphalt specimens. Furthermore, it was found that both the specimens with spraying photocatalyst aqueous solution and the specimens with spreading powder had a good NO removal effect. However, with the increase of photocatalyst content, the NO removal efficiency of sprayed specimen was higher than that of the spreading specimen due to the good dispersion of the photocatalyst in the spraying solution.

Fatigue cracking and permanent deformation (rutting) are major distresses that occur in flexible pavements. One of the most significant solutions to prolong the fatigue life as well as rutting resistance for an asphaltic mixture is to utilize flexible materials such as fibers. The impact of fiber addition to hot-mixed asphalt (HMA) was investigated utilizing a developed testing program in which the mechanistic and mechanical performance of fiber-reinforced mixtures as well as the economic attributes were evaluated. All beam fatigue tests were strain-controlled tests performed according to current guideline procedures. The testing results indicated that the fiber-reinforced mixtures had a better performance compared with conventional mixtures in terms of rutting and fatigue resistance. Additionally, a mechanistic analysis coupled with a cost-effectiveness analysis study based on the fatigue and rutting resistance performance on the two mixtures was performed. Overall, analysis showed that fiber-reinforced asphalt mixtures exhibited significantly lower cost of pavement per 1,000 cycles of fatigue and rutting life 1.6 km (1 mi) compared with conventional HMA mixture.

This paper presents a finite-element model developed to predict concrete drying behavior and internal relative humidity with very simple inputs that are known to engineers and practitioners (concrete mix design and cement Bogue composition). The model is based on an empirical derivation of the sorption isotherm, which is used to deduce the pore size distribution, as well as a derivation of total porosity and pore tortuosity through previously published formulations. Pore size distribution and total porosity are used to determine vapor and liquid water permeability, which is used to solve for moisture transport due to drying. The model is applicable for concrete that is not exposed to self-desiccation and/or wetting and drying cycles. The model is compared with a wide range of published experimental results and found to provide accurate predictions of internal relative humidity with these simple inputs, even in cases where the Bogue composition is not known. Limitations and uncertainties associated with the model are discussed and room for future improvement is suggested.

The recycling of asphalt shingles (RAS) in hot mix asphalt (HMA) has been the topic of much research. The asphalt binder of RAS is highly aged, oxidized, and stiffened, and the incorporation of it into HMA may alter the performance characteristics of the asphalt mixture. The first goal of this study was to determine the degree to which RAS binder blends with HMA virgin binder; the second goal was to determine the potential effects of this blending of binders on the long-term performance of RAS-containing HMA. A series of laboratory experiments were conducted, and the performance of RAS-containing HMA, which was fabricated replicating practical field conditions, was compared in two extreme scenarios—zero binder blending and total blending. The results showed that the performance of RAS-containing HMA tended to be closer to the total blending scenario. This suggests that RAS binder blends with HMA virgin binder nearly to the full extent. In addition, increasing RAS content makes HMA brittle and, therefore, more vulnerable to early-age cracking.

The effect of tricalcium aluminate (${\mathrm{C}}_3\mathrm{A}$) on the erosion degree and products of silica minerals under the thaumasite form of sulfate attack condition was studied using X-ray diffraction (XRD), a scanning electron microscope (SEM), and an energy dispersive spectrometer (EDS). The results show that ${\mathrm{C}}_3\mathrm{A}$ accelerated the formation rate of thaumasite, and the improvement degree depended upon ${\mathrm{C}}_3\mathrm{A}$ dosage. Crystal structures presented that the erosion products were thaumasite form solid solution after attack, and the value $a$ decreased with increasing of ${\mathrm{C}}_3\mathrm{A}$ content, but value $c$ had the opposite result. The morphology of the solid solution indicated that the crystal size became smaller as the ${\mathrm{C}}_3\mathrm{A}$ dosage increased.

Recycling of waste tire rubber is a significant environmental problem due to the huge number of waste tires needing disposal. A promising alternative to methodologies usually used for this aim is the use of tire rubber in the construction industry as artificial aggregate in concrete. This paper investigated the effects on the concrete compressive strength of the partial replacement of natural aggregates with waste tire rubber. Different types and amounts of natural aggregate substitutions were considered, with percentages of rubber ranging from 0% to 100% and including only fine aggregates (F), only coarse aggregates (C), and fine and coarse aggregates simultaneously (C&F). A literature review and new experimental data were considered, presenting about 1,500 tests from dozens of different authors in more than 20 independent studies, included the present one. Based on this large data set, new analytical relationships were developed and proposed to analyze the concrete strength reduction factor (SRF) expected as a consequence of natural aggregate substitution with rubber, and the relationship with the equivalent degree of compaction (EDC) of the mixture was considered.

The main interest of this research investigation is to explore the effects of the ${\mathrm{Al}}_2{\mathrm{O}}_3$ proportion present in metakaolin (MK) on the mechanical properties of magnesium phosphate cement (MPC). Different contents of MK and ${\mathrm{Al}}_2{\mathrm{O}}_3$ were used to replace magnesium to prepare magnesium phosphate cement and some properties, such as setting time, compressive strength, flexural strength, and bonding strength, were tested in this paper. Experimental results showed that the presence of MK and alumina could decrease the exothermic reaction intensity of MPC, and resulted in extending setting time. The addition of MK can improve the compressive strength and flexural strength of MPC; meanwhile, the rate of flexural strength increasing with MK addition was lower than that of the compressive strength. It was also found that the bonding strength of MPC-containing MK and alumina was superior to the control mortar mixture. In addition, the improvement mechanism was discussed based on the microanalysis of X-ray diffraction (XRD), scanning electron microscope (SEM), along with energy dispersive spectrometer (EDS). The microstructure results showed that a homogeneous and amorphous substance (${\mathrm{AlPO}}_4$) as a secondary hydration product was distributed widely, which modified the mechanical properties of MK-MPCs.

This work attempts to analyze the impact of plastic strips on the compressive strength of concrete. Three sets of concrete mixes, one of conventional concrete (CC) and the other two modified concrete with plastic [polyethylene terephthalate (PET)] strips, viz., horizontally oriented plastic strips (MC-H) and randomly oriented plastic strips (MC-R) were tested. Load and deflection controlled analyses show the PET strips as contributing toward 5%–15% enhancement in compressive strength and a substantial reduction in the standard deviation (60%–65%). Further, modified concrete in comparison with conventional concrete exhibits higher stiffness and the early arrival of peak load with relatively steeper response in the postpeak regime. An analytical model attempting to quantify the role of PET strips in offering confinement is proposed in the study. The model describes the contribution of PET in terms of confinement stress and is used to justify early arrival of peak load. It also closely predicts the inclination of failure plane. This study reveals the positive role of PET strips in controlling heterogeneity in concrete behavior, increasing stiffness, and attaining early peak load.

An experimental research program was carried out to evaluate the environmental impacts of embankments constructed with steel slag on groundwater. A series of sequential water leach tests and sequential column leach tests were performed to study the leaching of aluminum, copper, and zinc into groundwater due to the flow of percolating rainwater through treated steel slag. The results indicated that treating steel slag prior to use by mixing with an alum-based water treatment residual resulted in lower effluent pH and metal concentrations. Metal leaching was greatly affected by the effluent pH and total metal content, as well as the natural pH and buffering capacity of the subgrade. The results of the employed numerical model showed that the field metal concentrations were expected to be considerably lower than those measured in laboratory column leach tests due to dispersion within the vadose zone.

The effects of in-place volumetric properties on the rutting and cracking of asphalt pavement are of great interest to the pavement industry. As such, the major objectives of this paper are to determine the volumetric properties that correlate with field rutting and cracking and to quantify the field performance difference between low and high magnitudes of the determined volumetric properties. This study included 71 pavement sections from 24 field test roads that were part of the National Cooperative Highway Research Program (NCHRP) 09-49A project and covered different mix designs, volumetric property ranges, pavement ages, and four climate zones across the United States. The volumetric properties investigated are in-place air voids, voids in mineral aggregate (VMA), voids filled with asphalt (VFA), asphalt film thickness, and effective binder content ($V_{be}$). Rutting and cracking (transverse and longitudinal) performance data for all the test sections were collected in accordance with the Long-Term Pavement Performance program’s Distress Survey Manual. The authors identified the volumetric properties that correlated well with field performance and determined threshold values using the fuzzy clustering method to divide the identified volumetric properties into two groups: one with relatively small values, and the other with relatively large values. The rutting and cracking between the two groups were then compared. The results indicate that in wet climate areas, higher in-place air void percentages and lower VFA values correlate with more top-down longitudinal cracking. The sensitivity of the in-place air voids was sufficient to distinguish differences in cracking, whereas VFA sensitivity was not able to do so. Also, thicker asphalt film correlated with less field transverse cracking. The variables that clearly affected rutting were the VMA and $V_{be}$, whereby lower $V_{be}$ values indicated better rutting resistance. However, $V_{be}$ was unable to distinguish rut depths of various magnitudes. The effect of VMA on rut depth is complicated and there might be a sensitive range of VMA within which the rutting resistance of asphalt pavement can be more sensitive.

Research and experience have both shown that epoxy-coated reinforcement, the use of which is mandated by most state departments of transportation for bridge decks, increases cracking. Although the epoxy coating protects the steel from corrosion, bond strength is compromised and the increased cracking exacerbates durability issues in concrete. As a means to improve bonds and reduce the formation of cracks, the Illinois Department of Transportation (IDOT) proposed texturizing the surface of epoxy-coated bars. IDOT developed a prototype textured epoxy coating, and this paper details a preliminary study on the bond strength of reinforcing bars with the new coating. Direct pull-out and beam specimens are tested to compare the bond characteristics of uncoated, standard epoxy-coated, and textured epoxy-coated (TEC) No. 5 (15.9-mm diameter) and No. 8 (25.4-mm diameter) reinforcing bars. Bars with the textured epoxy coating showed good force-slip behavior comparable with black steel initially, but a rapid degradation in slip resistance was observed. In flexure, the TEC reinforcement demonstrated significantly higher slip resistance and resistance to crack widening compared with the conventional epoxy-coated bar. Overall, the added frictional resistance of the textured epoxy-coating showed promise. However, further research is needed to optimize the coating and characterize its behavior.

Ferronickel slag (FNS) which is also known as electric arc furnace slag is a byproduct of the production of ferronickel alloy. The production of FNS at Société Le Nickel (SLN) in New Caledonia is about 2 Mt per year with an existing stockpile of 25 Mt, which presents an excellent potential for concrete applications in the Pacific region. The possibility of using FNS from SLN as fine aggregate replacement in concrete is investigated. The low-carbon-concrete mix design includes 50% natural sand replacement by FNS sand and 25% ordinary portland cement substitution by fly ash. Microstructural analysis by scanning electron microscopy—energy dispersive X-ray spectrometer (SEM-EDS) of the interface transition zone (ITZ) of FNS sand shows that the excess in Portlandite weakening the ITZ of natural aggregate is absent in FNS sand ITZ. As a result, the resistance against chemically aggressive ions diffusion, water absorption, sorptivity, bulk and surface resistivity, and volume of permeable voids are significantly improved compared with the reference concretes due to the pozzolanic effect of FNS strengthening the ITZ. The substitution of 50% natural sand by FNS sand allows offsetting the detrimental effect of using fly ash on the concrete resistance against carbonation. All results show that using FNS sand in concrete can improve the concrete performance.

Freeze-thaw cycles can damage the microstructure of concrete and reduce the service life of structures, which is particularly detrimental for concrete at very early ages. What size range of pores can be affected by the early-age freeze-thaw cycles and whether the later-age curing can recover the damage to pores are critical questions for understanding the mechanism and avoiding frost damage. Typical low and high water-to-cement (w/c) ratio pastes were investigated experimentally in this study in terms of the pore-size distribution. The pastes were subject to freeze-thaw cycles at the ages of 1 and 7 days and then sealed cured to the age of 40 days for pore-size distribution measurement by the techniques of mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM) with backscattered electron (BSE), and X-ray computer tomography (X-ray CT). The detectable pore-size range by MIP, BSE, and X-ray CT in hardened paste was identified. The pore characteristics within each size range were quantified. It was found that the pores in high w/c $\mathrm{ratio}=0.5$ paste have been coarsened significantly compared to the low w/c $\mathrm{ratio}=0.3$ paste, and the later sealed curing cannot recover the damage. Combination of different techniques can achieve a full-scale quantification of pore size. The total porosity of the samples cannot be directly determined by adding different porosity obtained by different techniques. The results of this study will offer suggestions for material design and curing strategies for concrete structures that are prone to experiencing freeze-thaw cycles at very early ages.

Unreinforced concrete or concrete reinforced with noncorrosive reinforcement could potentially be mixed with seawater in locations where potable water is scarce. A fundamental understanding of the properties of concrete mixed with seawater is therefore essential. This paper analyzes the hydration kinetics, hydrate phases, pore solution, and porosity of cementitious pastes made with seawater and compares these results with the corresponding ones from pastes made with deionized water. Pastes were prepared with cement and with a 20% mass replacement of the cement with fly ash. Isothermal calorimetry (to study hydration kinetics), thermogravimetric analysis (to study the hydrated phase assemblage), X-ray fluorescence (to determine pore solution composition and electrical resistivity), and dynamic vapor sorption (to determine the pore size distribution) were performed on the paste samples. Seawater accelerates hydration kinetics at an early age; however, this effect is negligible at later ages. Friedel’s salt formation in systems with seawater at later ages is negligible [0.4% (by mass of paste) at 91 days]. The primary difference between the hydrated phases of pastes made with seawater and those made with deionized water appears to be the absorption of chloride in the calcium silicate hydrate. The pore solution in pastes made with seawater has higher sodium, chloride, and hydroxide ion concentrations. The concentrations of sodium, potassium, and hydroxide ions in pore solutions are lower in pastes with fly ash compared to pastes without fly ash. Pastes with seawater show a lower electrical resistivity than pastes with deionized water due to the higher ionic concentrations. Paste with seawater has a slightly finer pore structure compared to paste with deionized water.

The long-term friction performance of safety-focused friction surfacing, especially high-friction surface treatment (HFST), relies primarily on the properties of aggregate. Nevertheless, inconsistencies exist in the properties and attributes and requirements for aggregates across the country. A study was conducted to evaluate the properties of the calcined bauxite and steel slag aggregates selected for HFST. Differences were identified between the British Standard (BS) and AASHTO test methods for aggregate abrasion and polishing. Laboratory tests were conducted to determine the mechanical, physical, chemical, and geometric properties of the selected aggregates. It was found that the Micro-Deval abrasion (MDA) test is a repeatable test. A size effect existed in both the abrasion and polishing tests. It was concluded that steel slag may be used as an alternative aggregate for friction surfacing. The requirements for aggregates for HFST were established in terms of the critical property attributes, particularly the Los Angeles abrasion (LAA), MDA, and polish value PV-10, which can be readily implemented by state Departments of Transportation.

The use of waste materials in construction is gaining increasing interest due to the development of new technologies. This paper presents an experimental study on geopolymer binder produced with copper mine tailings (MT) and low-calcium slag (SG) for potential applications in road construction. The study systematically investigated the effects of water-to-solid ratio (w/s), SG content (0%, 25%, and 50%), sodium hydroxide (NaOH) concentration (5, 10 and 15 M), and the ratio of sodium silicate (SS) to sodium hydroxide (0.0, 0.5, 1.0, and 1.5) on the unconfined compressive strength (UCS) of synthesized geopolymer binder specimens. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analyses were also performed to characterize the microstructure and phase composition of the geopolymer specimens. The results show that the inclusion of SG improves UCS and reduces the initial water content required for achieving a certain workability of the geopolymer paste. The geopolymer binder specimens prepared at 50% SG, 10-M NaOH, $\mathrm{SS}/\mathrm{NaOH}=1.0$, and cured at 60°C for seven days reached the highest UCS of 23.5 MPa. The geopolymer paste prepared at 50% SG, 15-M NaOH concentration, and $\mathrm{SS}/\mathrm{NaOH}$ ratios of 0.5 and 1.0 showed flash setting, which led to poorer quality specimens and lower UCS. The SEM, EDS, and XRD analyses clearly showed the participation of iron dissolved from SG in the formation of geopolymer gels. This research helps promote the reuse of MT and SG through geopolymerization and contributes to the knowledge of geopolymer materials.

The long-term permanent deformation behavior of subgrade soil repeatedly subjected to traffic loading has a significant effect on the settlement of pavement during operation. Many studies conducted on this topic have focused on granular materials, marine soft soils, frozen soils, or fouled ballast. However, the deformation behavior and cyclic strength of compacted loess subjected to traffic loading have undergone limited investigation. In this study, the development of permanent strain in compacted loess was addressed using a number of cyclic triaxial tests. The effects of cycle number, cyclic amplitude, and confining pressure were examined in detail. Permanent strain was separated into two broad categories: the initial strain generated by the first cycle and the accumulated strain generated by subsequent cycles. Furthermore, a predictive formula was proposed in order to describe the mechanism by which permanent strain varied according to cycle number, cyclic amplitude, and confining pressure. Linear fitting was employed in order to establish the relationship between the initial strain and the amplitude of cyclic stress, and a log function was used to establish a correlation between accumulated strain and cycle number. In addition, the cyclic strength of compacted loess was also addressed. The results indicate that initial strain exhibits an ostensibly significant effect on the distribution of cyclic strength versus cycle number and contributes to a large proportion of overall permanent strain, especially at a low cyclic-stress level.

In this paper, Mode I and Mode II fracture energies of self-consolidating concrete (SCC) are examined. Two shapes of Mode II specimens are used, and the specimens are made from mixtures with three different water-to-cement (w/c) ratios. To determine the fracture energy, the size effect methodology is also considered. Results indicated a mixed-mode fracture for beam-type double-notched specimens under four-point loading. There is an evident size effect for the Mode II fracture that is pronounced for larger specimens. With the decrease in w/c ratio from 0.65 to 0.45, and thus increase in compressive strength from 26.44 to 53.5 MPa, the Mode II fracture energy increased by 47%. The brittleness number increased for specimens with higher compressive strength or larger size. The failure cracks propagate through the aggregates rather than the paste for lower w/c ratios. The Mode II fracture energy was on average 26 times the Mode I fracture energy, and this ratio grows by reducing the w/c ratio. Approximate empirical relations are proposed for Mode II fracture energy as well as the ratio of Mode II to Mode I fracture energy ($G_{II}/G_I$) in terms of the compressive strength. Mode II fracture energy takes a lower value for SCC compared with conventional concrete.

The aim of this research is to determine the durability and strength of concrete continuous footing based on the chosen mechanical, physical, and chemical properties of the concrete. The presented investigations constitute some opinions from experts on the bearing capacity of concrete continuous footing and the possibilities of carrying additional loads and extended working life. The cylindrical specimens were taken from continuous footing by a concrete core bore hole diamond drill machine. The properties of old concrete are compared with present and old standard requirements and guidelines. Large dispersions of the cylindrical compressive strength (6.9–29.3 MPa), density ($\mathrm{1,750}–\mathrm{2,100}\mathrm{kg}/{\mathrm{m}}^3$), and water absorption (5%–14%) were observed. A short literature survey concerning old concrete properties is also given.

Nitrate and nitrite-based corrosion inhibitors have been studied for decades for mitigating corrosion of steel embedded in ordinary portland cement (OPC) concrete; however, few studies are available regarding the effect of nitrate or nitrite on the performance of alkali-activated binders. This work, for the first time, investigates the influence of three nitrate-containing activators (i.e., sodium nitrate, magnesium nitrate, and aluminum nitrate, each mixed with sodium hydroxide solution) on the strength development, pore structure, phase assemblage, and phase stability of alkali-activated slag (AAS) binders upon exposure to chloride and natural carbonation. The results show that the addition of nitrate, regardless of its form, does not substantially alter the type of main reacted phases, i.e., calcium-aluminosilicate-hydrate (C-A-S-H) and Mg-Al layered double hydroxides (LDHs), in AAS; however, the addition of aluminum nitrate improves its compressive strength, boosts the formation of Ca-Al LDHs (AFm-type phase), and likely inserts nitrate anions in the interlayer of formed Ca-Al or Mg-Al LDHs. The findings suggest that the nitrate-intercalated Ca-Al LDHs and/or Mg-Al LDHs, if formed to some extent, can potentially release nitrate ions during chloride binding and carbonation, working as a smart corrosion inhibitor.

Recycled asphalt pavement (RAP) is increasingly being used due to the economic savings and environmental benefits. RAP contains removed or reprocessed asphalt binder and aggregates instead of virgin material. In order to minimize the damage due to water migration in RAP, pavement design requires accurate quantification of its hydraulic properties. This paper first presents theoretical formulations that enable finding the most accurate and applicable models for RAP. Hydraulic conductivity of RAP is predicted using models containing asphalt content and associated parameters. Results of several widely used empirical and semiempirical models were also compared to identify the one that is most reliable for RAP. A systematic evaluation is presented based on root-mean-square error (RMSE) analyses of predicted and experimentally measured hydraulic conductivity values. The influence of bitumen content and grain-size distribution factors on hydraulic conductivity of RAP were evaluated by the addition of new variable combinations to account for these effects on the best widely used model. Logarithmic linear regression was used to develop new relationships between hydraulic conductivity and different variable combinations to determine the influential variables. It was determined that factors related to grain-size distribution play a prominent role in hydraulic conductivity of RAP. It was observed that the RMSE values of models that contain asphalt content were comparable to those of the Kozeny-Carman model, but lower than those of the Hazen, Slichter, Terzaghi, Beyer, Kruger and Fair-Hatch models. The latter do not contain asphalt content, showing that models that contain it gave better predictions.

As an organic solvent, naphthenic oil is used widely in the polymer industry, so it has the potential to be used with polymer to improve the performance of asphalt binder in pavement engineering. The effects of naphthenic oil as an additive for styrene-butadiene-styrene (SBS)–modified asphalt were investigated in this paper. Penetration, softening point, ductility, rheology property before and after aging, morphology observation, and storage stability were tested on naphthenic oil/SBS-modified asphalt. The following findings were achieved: Naphthenic oil increases the consistency and temperature sensitivity of SBS-modified asphalt. It is remarkably beneficial to the low-temperature property of SBS-modified asphalt. It is not advantageous to the resistance to deformation. Naphthenic oil is beneficial to the antiaging property of SBS-modified asphalt and helps the polymer to get swollen, proving that naphthenic oil has some properties of aromatics. Another discovery is that naphthenic oil makes the SBS distribute more evenly, which is consistent with the discovery in the rubber industry. Future investigation of its use with other additives and the anti-ultraviolet light (UV) aging properties are suggested.

Dynamic shear modulus of an asphalt mastic has a remarkable effect on the mechanical performance of an asphalt pavement, and particulate composite micromechanical models are proven to be suitable for the prediction of modulus of asphalt mastics. However, the prediction accuracy of the current micromechanical models decreases sharply at a high filler concentration and high temperature (or low frequency). This study aims to develop a modified micromechanical model that can be applied to predict modulus of asphalt mastics at a wide range of frequencies and filler concentrations. Dynamic shear rheometer (DSR) tests are performed using asphalt mastics with four filler concentrations, and three-dimensional discrete-element method (DEM) is implemented to validate the DSR tests and obtain additional master curves of asphalt mastics with different filler concentrations. The reinforcement mechanisms are introduced into the micromechanical models to predict the laboratory test results with an increase of the prediction accuracy. The numerical results show that the test data is repeated by the DEM simulation, which is believed to be a promising tool to present the rheological behavior of asphalt matrix and asphalt mastics. The modified micromechanical viscoelastic model can predict the dynamic shear modulus of asphalt mastics successfully at high filler concentration and low frequency.

The application of palm oil fuel ash (POFA) and fly ash (FA) as an alumino-siliceous precursor to create a viable geopolymer binder for the manufacture of unfired lightweight masonry units, using soft soil (SS) as aggregate, was studied in this research. The POFA was a byproduct from a palm oil factory, while FA was a byproduct from a coal-fired electricity generation plant. Unconfined compressive strength (UCS) and the microstructure of POFA–FA–SS geopolymers were investigated. The optimal liquid alkaline activator (L) providing the maximum total unit weight was found to decrease with increases in the POFA replacement ratio for all ${\mathrm{Na}}_2{\mathrm{SiO}}_3:\mathrm{NaOH}$ ratios. The optimum ${\mathrm{Na}}_2{\mathrm{SiO}}_3:\mathrm{NaOH}$ ratio providing the highest strength for all heat conditions decreased with increasing POFA replacement because additional NaOH was required for leaching ${\mathrm{SiO}}_2$ from POFA for a geopolymerization reaction. The optimum ${\mathrm{Na}}_2{\mathrm{SiO}}_3:\mathrm{NaOH}$ ratios providing the highest UCS were found to be 90:10, 80:20, 70:30, and 60:40 for FA:POFA ratios of 100:0, 90:10, 80:20, and 70:30, respectively. The optimum heat condition was found to be 80°C for 48 h. The higher temperature of 90°C was not recommended because UCS gain was relatively small due to a substantial loss of moisture during heat curing. More time was required for the lower temperature of 70°C to accelerate the geopolymerization reaction. Microstructural analysis showed that the highest cementitious product, sodium aluminum silicate hydrate (N–A–S–H), was formed for the POFA–FA–SS geopolymers at the optimum ${\mathrm{Na}}_2{\mathrm{SiO}}_3:\mathrm{NaOH}$ ratios and heat conditions. The cementitious product decreased along with the FA:POFA ratio, which is associated with UCS reduction. Based on industrial standards in Thailand, the POFA–FA–SS geopolymer was found to be viable as an environmentally friendly nonbearing masonry unit at an optimum FA:POFA ratio of more than 80:20.

Damage due to atmospheric corrosion on metal structures is a significant aspect for both the design of new construction and the maintenance of existing buildings. This problem is particularly felt for nineteenth-century wrought iron constructions, because of both lack of proper maintenance and architectonic value. The main objective of the current paper, framed within a more comprehensive research project, is to provide a time-dependent model able to predict the corrosion wastage thickness on historical metal structures as a function of the protection coating life variability and its renovation cycles. Average damage curves, calculated on a sample of 20 buildings experimentally monitored for 20 years, were taken as literature references to calibrate the model, based on the hypothesis that the durability, due to phosphorus content, of historical wrought irons are between that of recent mild carbon steels and that of weathering steels. The reference damage curves for two environmental conditions (marine and urban–industrial) and two different materials (mild carbon steel and weathering steel) were interpolated, fitted, and extended to 125 years. A comparison was made between experimental damage curves and some significant models from literature, and the percentage error with respect to the tolerance and confidence intervals of the reference damage curves is discussed. Results definitely confirm a substantial difference between experimental values and those predicted by literature models. As an application example, the model was applied to estimate the remaining life of the metal structural elements of the Umberto I Gallery in Naples, one of the most significant monuments of the largest city in Southern Italy.

Asphalt mortar plays an important role in the performance of asphalt mixtures. Up to now, there have been many studies on the properties of asphalt mortar. However, asphalt mortar requires a balanced design that considers the overall performance including self-healing capability. Therefore, this study aims to analyze the effect of different types of filler with varied ratios (0.11, 0.22, 0.33, 0.44, and 0.55) by volume on the performance of the asphalt mortar and mixture. The examined fillers were limestone, fly ash, diatomite, and four types of red mud, which were mixed with bitumen to prepare asphalt mortar. Then, the rheological properties of the asphalt mortar were investigated through viscosity tests and multiple stress creep recovery (MSCR) testing. In addition, this research explores the impact of filler type and its ratio on the cohesion and self-healing performance in dry and water conditions. Furthermore, the Hamburg wheel tracking test (HWTT) was performed to evaluate the moisture-damage and rutting resistance of asphalt mixtures, which consisted of the same selected mortar. The results indicate that pull-off tensile strength after the first failure-healing (F-H) cycle in the water condition has a good linear relationship with the dynamic stability of the asphalt mixture in the HWTT. Moreover, red mud and diatomite can be applied as promising substitute fillers compared with the other examined fillers in this study, but the chemical components need to be carefully selected.

This paper presents the effect of ground granulated blast-furnace slag (GGBFS) content on the alkali–silica reaction (ASR) in geopolymer mortar using the accelerated mortar bar test and scanning electron microscope (SEM) analysis. Three geopolymer mixtures with different fly ash/GGBFS weight ratios (9, 4, and 1) along with one ordinary portland cement (OPC) mixture were considered in this study. Other parameters of the geopolymer mixtures were kept constant. Mortar bar prisms were prepared in accordance with accelerated mortar bar test standards for expansion measurements, and SEM analysis was performed after 21 and 150 days of immersion in 1 M NaOH solution at 80°C. In addition, compressive strengths of mortar cubes were measured up to 29 days. Silica dissolution of the reactive aggregate used in mortar was determined by immersing it in NaOH solutions with different pH values. This study’s results suggest that the ASR in geopolymer is lower than that of OPC and that expansions due to ASR in geopolymer mortar increase with the increase in the GGBFS content in the mix design. Finally, this paper also emphasizes that the standard accelerated mortar bar test needs to be modified before endorsing it for geopolymer mortar.

This paper presents the results of a pilot study to evaluate a solid-state welding technology, called surface activated solid-state (SASS) welding, for joining structural steel members. SASS welding does not require bulk melting of base metals and can be readily automated to produce high quality joints free from volumetric flaws and without extensive operator training. In addition, this welding process is performed instantly over a plane, in contrast to sequentially along lines as in arc welding; consequently, the former achieves much higher production rates than the latter. Butt-welded joints constructed from A992 steel were SASS welded and subjected to a series of mechanical tests and metallurgical evaluations. Coupon test results indicate that the SASS-welded joints can overmatch the tensile strength and match the ductility of the base metal. However, in the as-welded condition, SASS-welded joints did not display sufficient notch toughness for use in demand critical applications. A metallurgical study of these joints suggests that coarse prior austenite grains, brittle secondary phases, and the texture of grain boundary ferrite at or near the joint interface were possible causes. Notch toughness of SASS welds was significantly improved by post-weld heat-treatment, particularly at temperatures higher than $A{c}_3$, which were observed to homogenize the microstructure across the weld joint, refine ferrite grains, and produce purely reconstructive phase transformation products (i.e., polygonal ferrite + pearlite). The improvement in notch toughness is believed to be a result of these microstructural changes.

In the present investigation, geotechnical properties of fly ash lime (FAL) mixes and fly ash cement (FAC) mixes were studied for their use as a subbase material for flexible road pavements. The effects of lime content, cement content and curing age on unconfined compressive strength (UCS), resilient modulus, and permanent strain of these mixes were studied. Fly ash with minimum 6% lime content and fly ash with minimum 6% cement content satisfy the minimum strength criteria recommended by the Indian Road Congress (IRC) for their use as subbase materials. These mixes exhibited higher resilient modulus than the conventional granular subbase (GSB). The influence of wetting-drying (W-D) cycles on resilient modulus was also reported in this study. The fitting of different existing models for the measured data of resilient modulus and permanent strain was compared, and the model parameters of FAL and FAC mixes for the best fitting model were determined.

More than $60\mathrm{billion}\mathrm{kg}$ ($60\mathrm{million}\mathrm{t}$) of industrial by-products such as fly ash, garbage melting furnace slag, and steel slag are generated every year in Japan. Almost all of them seem to have been effectively used in mixtures with cement according to their chemical and mechanical characteristics in the field of civil work. Fly ash and slags can be used to create geopolymers in a process that emits less carbon dioxide than does the cement-making process. This reduction in ${\mathrm{CO}}_2$ emission is important because ${\mathrm{CO}}_2$ is one of the substances known to contribute to global warming. In the future, further uses of these fly ash and slags must be explored. The chemical mechanism for hardening composite materials by mixing aluminosilicate binders such as fly ash and slags with alkaline activators such as liquid NaOH and sodium silicate is known as a geopolymeric reaction, and the hardened composite material is called geopolymer. Geopolymers are produced by mixing two components of solid binders, such as fly ash, slags, and so on, with liquid activators such as NaOH, KOH, sodium silicate, and so on. Geopolymers have recently been developed to be used as a replacement for portland cement concrete. Research has been done to improve the compressive strength characteristics of both geopolymers and the combination of soft soil and fly ash–based geopolymer. The development of high compressive strength geopolymer using fly ash and slags will strongly contribute to the fields of construction, geotechnical engineering, and architecture. This paper describes the method for production and strength diagnosis of geopolymers considering the chemical composition of fly ash or slags.