Journal of Materials in Civil Engineering

Cold in-place recycling technology for reclaimed material in pavement rehabilitation holds promise as a solution to resource scarcity. This paper reports results of a systematic experimental investigation of the material produced by this technique and in particular the role of cement and air void content. The internal structure is characterized using computed tomography and environmental scanning electron microscopy. A tension and tension-compression test is carried out to characterize the response of the material at 15 and 45°C. From microscopy, it is seen that the addition of cement did not result in formation of hydration compounds, but instead aids in densifying the material substantially. From the mechanical experiments, it is seen that the response of the material is clearly viscoelastic at the temperatures at which it is tested. The experimental data are used to find relevant linear viscoelastic parameters, and a methodology to compute these parameters directly is presented.

This study explores the engineering properties of a new self-compacting concrete (SCC), named as SFC-SCC, produced with a no-cement SFC binder and the bonding behaviors of embedded steel bar confined by this SFC-SCC using the pull-out test. The no-cement SFC binder was purely made from the mixture of slag (S), Class F fly ash (F), and circulating fluidized bed combustion (CFBC) fly ash (C). Experimental results showed that the 28-day compressive strengths of no-cement SFC-SCCs were in range of 32.3–42.6 MPa with the flowability of 620–650 mm at the fresh state. With equivalent 28-day compressive strength, the similar bonding strength of SFC-SCCs to that of the ordinary portland cement (OPC) concretes was observed with the required covering thickness of SFC-SCCs being lower than that of OPC concretes. The analysis on relationship between bonding and compressive strengths shows that the bonding quality of the SFC-SCCs is similar to that of the plain OPC concretes implying that the former also has a high potential of application as an alternative reinforced concrete for practical infrastructural construction.

Damping properties have important effects on the dynamic behavior of civil engineering structures. However, the influence of load on the material damping of concrete has not been studied systematically. This paper used an experimental strategy to investigate the effects of stress amplitude, loading frequency, and stress level on the material damping of concrete. The experimental results showed that equivalent damping increased with the increase of stress amplitude and was slightly influenced by the loading frequency and stress level. Subsequently, the classical Kelvin model was used to simulate the energy dissipation property of concrete under cyclic axial compression. The viscous coefficient of the Kelvin model was identified based on the experimental data, and a correction was conducted to describe the frequency-independent energy dissipation property of concrete. Comparison with experimental results shows that the modified model produces a high-accuracy solution for use in predicting the energy dissipation behavior of concrete material.

Technologies developed over the last two decades have introduced the use of glass fiber reinforced polymer (GFRP) composite bars as reinforcement in concrete structures when corrosion of the steel reinforcement is likely to occur. Fire resistance of GFRP-reinforced concrete (RC) members is a potential concern that needs to be understood and addressed because of the susceptibility of GFRP bars to degradation at elevated temperatures. In this study, the residual strength of fire-exposed GFRP-RC slabs and the GFRP mechanical properties after furnace exposure were studied. Slabs reinforced with two different types of GFRP bar were exposed to a furnace fire and sustained three-point bending, simulating the sustained service load (the moment due to dead load plus 20% of the moment due to live load at midspan), for 2 h. Upon completion of the fire test, the residual slab strength was assessed using a quasi-static flexural test up to failure. Next, GFRP bars were extracted from the selected locations of the slabs to evaluate the residual mechanical properties, including shear strength (transverse and horizontal) and glass transition temperature ($T_g$). The GFRP-RC slabs with both bar types did not experience apparent reduction in flexural capacity after a 2-h fire test that generated a maximum temperature of 115°C at the bar surface. The GFRP transverse shear strength decreased whereas the horizontal shear strength and $T_g$ slightly increased.

Oriented strand board (OSB) is an engineering material used in the building industry. In lieu of its cost-effectiveness and sustainability, OSB has been used widely as the skin layer of structural insulated panel (SIP), and is usually used in the building as wall panel and roof panel. During its service life, such panels might be subjected to various dynamic loads, such as windborne debris impact. Good understanding of dynamic failure behaviors of OSB material at different strain rates is needed for reliable prediction of the performance of OSB panel under dynamic loading. In this study, quasi-static and dynamic tests were carried out to investigate the static and dynamic failure behaviors of a specific OSB material. The testing results indicated the tensile strength of OSB was sensitive to strain rate. The damage mode under quasi-static loading condition was found to be different from that under dynamic loading condition, which affected the tensile strength of OSB material. An empirical formula was derived to predict the tensile strength enhancement of OSB material under different strain rates based on the testing results.

Shotcrete or sprayed concrete is widely used as ground support in the construction of tunnels. The early-age strength development of shotcrete is very important because it influences the determination of safe re-entry times beneath the tunnel heading. This study has examined the possible application of a handheld soil vane shear tester and a handheld auger penetrometer for testing the early-age strength of shotcrete. This is achieved by measuring the shear strength because previous research in this area indicates that the shear failure dominates the early-age resistance of shotcrete. The investigation involved testing of three techniques, which resulted in readings of both compressive and shear strengths. Shear testing involved a combination of the vane shear tester and the auger penetrometer, which obtains its readings through auger penetration and rotation. The compression testing involved the use of the Meyco needle penetrometer, which was tested on the same cast specimens as the shear tests and at the same time intervals. In this paper, the term shotcrete has been used for the special normal concrete, with a simple shotcrete mix design, used in this investigation. Strong correlations were found among the vane shear strength, auger penetrometer shear strength, Meyco penetrometer compressive strength, and time after pouring, for up to 4 h of testing. The shear strength results from the auger penetrometer and the vane shear tester are very similar, and there is almost a perfect linear correlation between the results from these two methods.

Mixing of soils with synthetic fibers has been a well-established approach in geotechnical engineering practice for ground improvement purposes. Of particular interest for most design problems in soil mechanics and earthquake engineering are the properties of geomaterials at medium strains, between approximately $5\times {10}^{-3}\%$ and $5\times {10}^{-1}\%$, where soil modulus and damping are highly sensitive to the strain magnitude (or strain amplitude involving cyclic-dynamic problems). The present paper reports on the small- ($<5\times {10}^{-3}\%$) to medium-strain behavior of two different sands mixed with polypropylene fibers. The study implemented high-amplitude resonant column tests to capture the behavior of a uniform natural sand and a well-graded crushed rock mixed with contents of reinforcing fiber between 0 and 2%. For this purpose, a fixed–partly fixed resonant column was used and the experiments were conducted on fully saturated specimens subjected to isotropic pressures from 50 to 800 kPa. The analysis of the results, in the range of medium strains, was conducted adopting a commonly used hyperbolic-type model and the model parameters were best fitted to the experimental data, allowing the investigation of the fiber content effect on the reference strain and curve shape parameter.

In this paper, atomic force microscopy (AFM) is used to evaluate micromechanical properties of the interfacial blending zone between reclaimed asphalt pavement (RAP) and virgin asphalt binders. Three virgin asphalt binders with different performance grades (PG 58-28, PG 64-28, and PG 64-22) and two sources of RAP binder are used to evaluate the effects of the different RAP and virgin asphalt binder properties on the stiffness and adhesive properties of the blending zone between these binders. A new procedure is developed to simulate the interaction between RAP and virgin asphalt binders that occurs in the drum in an asphalt plant. The AFM tests indicate that blending occurred between RAP and virgin binder for all six tested RAP-virgin asphalt binder combinations. The reduced modulus for the blending zone depended generally on the virgin binder grade and RAP source. The highest stiffness was achieved from the combination of RAP and PG 64-22, whereas the lowest stiffness was obtained from the combination of RAP and PG 58-28. The bonding energy results indicate that adhesive properties of the blending zone were adversely affected by the presence of RAP within the zone. However, the adhesive properties of the blending zone were significantly better than those for the RAP binders. The variation in the blending zone between both RAP binders and PG 58-28/PG 64-28 indicate that the blending zone might not be homogenous. Further analysis of the concentration of RAP binder within the blending zone revealed dependence on RAP stiffness characteristics. However, the adhesive properties of the blending zone were primarily controlled by the virgin binder properties.

In this paper, waste-tire crumb rubber with a size of 2–4 mm was used to prepare rubber concrete, and the axial compressive properties were tested at temperatures of $-30$ and 20°C. According to the feature points in the prepeak stress-strain curves, the strength, peak strain, deformability, and elastic modulus of rubber concrete at $-30°\mathrm{C}$ are compared with those at 20°C. The influence of different water/binder ratios and rubber contents on the relative axial compressive strength and relative elastic modulus of rubber concrete are also discussed. The results show that the ascending branches of axial compressive stress-strain curves of rubber concrete have a little difference with those of ordinary concrete. At $-30°\mathrm{C}$, the stress and strain of rubber concrete are much larger and the responding deformation ability is obviously better than that of ordinary concrete as the rubber content increases.

Chloride-induced reinforcement corrosion is one of the major causes of durability failure of concrete structures in a salty environment. Because concrete is a kind of heterogeneous material, the effect of coarse aggregate on chloride diffusion cannot be ignored. This paper presents the results of an indoor experimental investigation on chloride diffusion in concrete specimens with continuously graded coarse aggregate. Concrete specimens with different coarse aggregate volume fraction (CAVF) and various maximum sizes of aggregate (MSA) were exposed in a self-designed tidal cycle device, where the chloride environment of a tidal zone was simulated, to determine the chloride concentration profile along depth for 30, 60, 90, 130, and 170 days. A time-and-depth-dependent chloride diffusion coefficient was determined using the Boltzmann–Matano method in terms of the chloride measurements. CAVF and MSA impact factors were obtained on the basis of statistical analysis. The results show that the chloride diffusion coefficient increases initially and becomes stable afterward along the penetrating direction, but decreases as CAVF or MSA increases. Based on the aforementioned results, the authors propose a time-and-depth-dependent model of a chloride diffusion coefficient considering the effect of coarse aggregate, which is called the T-D model.

This paper studies the linear viscoelastic behavior under small strain amplitudes and the nonlinear behavior using large amplitude oscillatory shear (LAOS) tests performed at strains beyond the linear viscoelastic regime of bituminous mastics. Four types of mineral fillers—blast-furnace slag (BFS), silica fume (SF), fly ash (FA), and hydrated lime (HL)—with particle sizes less than 75 μm are used to prepare the asphalt mastics with proportions of 0.7 and 1.15 based on the mass of base binder. For the linear rheological measurements, small strain oscillatory shear testing is carried out within the linear regime of the materials. The nonlinear viscoelastic properties are investigated using the LAOS test performed at 40°C and 1 Hz to examine Lissajous-Bowditch plots and by analyzing the elastic and viscous nonlinearities of the mastics at strains of 0.5, 10, 20, 30, and 40%. The linear viscoelastic region (LVER) of the mastic and base binder depends not only on the strain amplitude but on the testing frequency and temperature as well. The filler type and concentration have an obvious influence on the linear viscoelastic properties of their mastics. The HL and SF fillers outperform the linear viscoelastic properties of the BFS and FA in terms of the complex shear modulus. The Lissajous-Bowditch plots become progressively distorted with the increase of strain amplitude and show an increase in the exerted stress with the addition of mineral fillers. The local nonlinear measures of an oscillatory LAOS cycle are able to quantitatively differentiate between the properties of studied mastics at different strain amplitudes. The mastic that shows the best performance in the linear regime is not guaranteed to perform superiorly in the nonlinear regime. The results can be used to differentiate or rank the properties of mastics and/or asphalt binders at different strain amplitudes in a quantitative manner.

Aluminum has been increasingly used in space, building, and other structures owing to its light weight and high durability. The cyclic plasticity of aluminum is of great importance for the design of aluminum structures in regions with high seismic risk, where extremely large plastic strain loading is involved. For seismic loading, strain amplitudes can vary in a wide range, which makes it necessary to calibrate the plasticity model at the full strain range. This paper aims to present a straightforward approach to accurately evaluating hysteretic properties of aluminum material and structures under variable-amplitude cyclic loading within the full strain range until fracture. In this paper, a new method is proposed to calibrate the generalized Armstrong-Frederick model at the full strain range using only representative mechanical variables of structural aluminum such as yield strength and tensile strength. The newly proposed method is validated at both the material and member levels, respectively, through quasistatic cyclic experiments on double-edge notched specimens and aluminum buckling restrained braces. The validation results show that the proposed method can well describe the cyclic plasticity of aluminum members at the full strain range.

Controlled low strength materials (CLSM) are gaining increasing importance with the growing emphasis on sustainability in the construction industry. Controlled low strength material can be a valuable application for the safe and efficient use of nonstandard materials such as industrial by-products, which are normally rejected for conventional concrete because of the negative impact on hardened properties. In the present study, a laboratory experiment was carried out to explore the effect of cementing paste volume on flowability and strength development of CLSM mixtures. The experimental results showed that the cementing paste volume had a more significant effect on the slump flow compared to the water to cementitious materials ratio ($\mathrm{w}:\mathrm{cm}$); however, it had little effect on compressive strength of CLSM mixtures. It is proposed that the cementing paste volume can be used as an independent parameter to target a desired flow in proportioning of CLSM without compromising the compressive strength of the mixtures.

This work studied the weathering aging behaviors of styrene-butadiene-styrene copolymer (SBS) modified asphalt. The aging behaviors mainly included physical and rheological properties, chemical structure, and morphology, which were evaluated by viscosity, dynamic shear rheometer (DSR), bending beam rheometer (BBR), Fourier transform infrared spectroscopy (FTIR), and fluorescence microscope tests. The results showed that the SBS modified asphalt had the best ability to resist weathering aging compared with the single SBS modifier or base asphalt. Early weathering aging could improve the compatibility between the base asphalt and the SBS modifier and enhance the modification effect of the SBS modifier to the base asphalt. The gray relation entropy analysis indicated that during the weathering aging of SBS modified asphalt, the complex modulus aging index (CMAI) at 30°C showed the closest relationship with the degradation of the SBS modifier compared with other aging indicators.

This study presents a new laboratory technique for binder aging by using a steam cooker. This new technique is used to study the effect of steam and heat on asphalt during storage and asphalt pavement during its service life. Five steam-aging durations (0, 15, 30, 45, 60, and 75 min) with four steam-aging stages at diffrent pressures and temperatures for each stage are selected to investigate the physical and rheological properties of steam-aged asphalt binders. The steam-aged asphalt binders are subjected to a short-term aging process by means of a rolling thin-film oven test (RTFOT) in order to investigate the influence of aging on steam-aged asphalt binder properties after aging. Bituminous binder properties are investigated by both physical and rheological methods. Tensile strength tests were used to select the suitable stage for the research. In general, the physical test results demonstrate prominent increments in softening point and viscosity, and decrements in penetration for steam-aged binders compared with nonaged binders. This study adopts a time-sweep (TS) test method to study the fatigue phenomenon under a control strain mode using a dynamic shear rheometer (DSR). Fatigue life of asphalt binders is defined using the traditional approach based on number of cycles required to cause to cause failure and reduction in stiffness. Temperature-sweep tests using a dynamic shear rheometer (DSR) are used to predict the asphalt grade after aging. Indirect tensile tests are done to study the effect of aging/moisture on the performance of asphalt mixtures. The main objectives of the study are to study the effect of pressure and temperature on asphalt binders by using new technique and to determine the sensitivity of steam-aging (LPSA) on asphalt binders and mixtures.

This study investigates the influence of composition and the resultant reaction of blended binders proportioned with a high volume of supplementary cementitious materials (SCMs) on shrinkage and restrained shrinkage cracking of flowable and ecologically friendly concrete (Eco-concrete). Concrete mixtures were designed using optimized particle packing of aggregate skeleton to secure relatively low binder content of $315\mathrm{kg}/{\mathrm{m}}^3$, containing 50% SCM replacement. Hydration kinetics using isothermal calorimetry, thermogravimetric analysis, autogenous and drying shrinkage, capillary water absorption, and development of mechanical properties were evaluated to characterize the effect of binder composition on shrinkage-induced cracking and tensile creep behavior of Eco-concrete. Test results indicate that mixtures provisioned with SCMs exhibited up to 60% longer time to cracking and developed 2.4–4.4 times larger tensile creep coefficient at the time of crack initiation compared to the control mixture without any SCM. Such spread can be attributed to (1) resultant reaction and pozzolanic activity, and (2) improved capillary porosity induced by SCMs, which can control the rate of elastic properties evolution and shrinkage at early and later age. Good correlations were established between hydration kinetics of the binders and shrinkage cracking tendency of Eco-concrete that can be applied for designing more sustainable binder systems with high shrinkage cracking resistance.

${\mathrm{Na}}_2{\mathrm{CO}}_3$ is considered to be a salt that causes destructive weathering distress on cementitious materials. In this paper, calcium sulfoaluminate (CSA) cement paste was partially immersed in a 10% ${\mathrm{Na}}_2{\mathrm{CO}}_3$ solution under constant conditions [$20\pm 2°\mathrm{C}$, and $60\pm 5\%$ relative humidity (RH)] and then under alternate sets of conditions ($30\pm 2°\mathrm{C}$ and $80\pm 5\%$ RH for 24 h, then $20\pm 2°\mathrm{C}$, and $60\pm 5\%$ RH for 24 h). The results showed that the paste remained relatively sound after 72 days of exposure under the constant conditions, but the paste was severely damaged after only four cycles under the alternate conditions. The microanalysis results of X-ray diffraction (XRD), environment scanning electron microscope (ESEM), energy dispersive spectrum (EDS), and ion chromatography (IC) indicated that ${\mathrm{Na}}_2{\mathrm{CO}}_3$ could not be identified in the damaged paste, and the mechanism was that ${\mathrm{Na}}_2{\mathrm{SO}}_4$ caused crystallization distress. ${\mathrm{Na}}_2{\mathrm{SO}}_4$ is the product of the chemical reaction between ettringite and a ${\mathrm{Na}}_2{\mathrm{CO}}_3$ solution.

This paper reviews the methods adopted to produce high-performance concrete (HPC) and ultrahigh-performance concrete (UHPC). The chronological development of these concretes in terms of their constituents, mixture proportions, mixing protocols, and particle packing models from selected literature are presented. The paper highlights the earliest techniques that were used to obtain cementitious materials with high strength and durability, including pressure mixing and heat curing. The paper also covers the work done on HPC and UHPC since the late 1990s and summarizes the current state of the art. Numerous mixture proportions to attain target compressive strengths between 100 and 200 MPa are presented. Higher compressive strengths are achieved with denser mixtures (with practically achievable maximum particle packing densities, i.e., interparticle pores are minimized). In other words, particle packing density is a major attribute in the achievement of low porosity, flowability, durability, and reduced defects in concrete. Therefore, models, theories, and trial methods to achieve a higher packing density in concrete are presented.

Reinforcement corrosion is a general problem about the reliability and durability of concrete structures. A lot of research about the issue of reinforcement corrosion has been done; however, it has focused primarily on reinforcement under zero strain. To discuss how tension strain affects reinforcement corrosion, a salt spray test was conducted on reinforcement specimens. The degree of corrosion in reinforcement and the mechanical properties of the tested reinforcement were obtained. The strength of reinforcement decreased with the degree of corrosion, and the decrease of elongation was more significant. Strain level had a nonnegligible influence on the degree of corrosion. The reinforcement corroded more when it was kept under a higher tension strain. During the same corrosion period, the corrosion degree in a specimen under a tension strain of $1.0\times {10}^{-3}$ was 1.22 times that of an unstrained specimen. The coefficient representing the effect of strain on corrosion was defined. It was also found that the influence of tension strain on mechanical properties of tested reinforcement is irregular.

This paper presents an experimental study on fresh and hardened properties of nonautoclaved aerated concrete (NAAC) mixtures. It also attempts to address a new method to determine the packing density and air percentage of NAAC mixtures. Different types of NAAC mixtures with various aluminum powder percentages and water-to-cement ratios were made. Results revealed that the new method (called the wet packing theory) is able to determine the percentage of air pores in the aerated concrete with high accuracy. Results also showed that there is an optimum aluminum percentage of approximately 0.0934 from the perspective of minislump diameter and compressive strength. With an increase in the aluminum percentage compared to the optimum percentage, minislump (workability and flow-ability) and compressive strength reduced. Scanning electron microscope (SEM) images of NAAC indicated that the air voids were shaped as an artificial porosity. The results showed that with an increase in the amount of aluminum powder, packing density reduced. It was observed that the maximum air percentage increased with an increase in the amount of aluminum percentage from 0.0934 to 0.1869.

This paper investigates high-cycle fatigue (HCF) failure in thermomechanically treated (TMT) rebars using fractographic analysis. Most fatigue failures are found to initiate at the root of the transverse ribs, irrespective of rebar diameter. Three-dimensional finite-element (FE) analysis is used to study the effect of modifications to the rib geometry on stress concentrations at these critical locations. Modification of the ratio of the radius ($r$) of the root of the transverse rib to its height ($h$) is found to reduce stress concentrations at the rib root. A procedure combining FE analysis with ideas adapted from notch fatigue is developed to predict the fatigue life of rebars with optimum $r/h$ ratio. The predicted fatigue life of a 16-mm-diameter rebar with optimum $r/h$ ratio is found to be significantly higher than that of the original rebar. Pullout tests reveal that the proposed modification to the rib design does not result in any deterioration in bond strength between rebar and concrete.

This paper investigates the effects of stress ratio and microstructure on the fatigue crack growth (FCG) behavior of HRB400 steel bars widely used in concrete bridges. A constant stress–controlled FCG test with different stress ratios is performed on compact tension specimens. Test specimens are machined from rebar in two directions, i.e., cracks propagate in the radial and axial directions of the steel bar. The FCG rate versus stress intensity factor range under different stress ratios and different crack orientations are obtained. The morphology of the fracture surface and the FCG path are examined by scanning electron microscope and optical microscopy. Following this, the FCG curves, fracture characteristics, and FCG paths are compared. The experimental results show that the radial and axial crack predominantly present the transgranular and intergranular fracture mode, respectively. The material presents a higher resistance to FCG in radial orientation than that in axial direction.

The bond characteristics between steel fiber and a cementitious matrix play a crucial role in controlling the performance of steel fiber–reinforced concrete (SFRC). The bonding mechanisms of SFRC have attracted considerable attention over the last four decades and are still active research. This overview provides a state-of-the-art understanding of the major mechanisms governing the pullout behavior of steel fibers. Characteristics of different types of bond and their functions have been explained in detail. Primarily important are bond strength in each of its likely failure modes. Different factors affecting the bond strength include geometry, orientation and embedded length of fiber as well as matrix strength. A review of existing analytical papers investigates the bond mechanisms between steel fiber and cementitious matrix. The review shows that the most successful method to improve bond slip is to reinforce concrete with pre-deformed fibers. This review also provides useful information on how fiber geometry influences pullout behavior from the matrix for a known relative strength between the two constituents. The theory of bonding and its related parameters is surveyed. Finally, recommendations for future research and optimum applications of SFRC are considered.

The presented work focuses on the influence of a water-soluble derivative of cellulose, hydroxyethyl methyl cellulose (HEMC), on gypsum thermal properties. The polymer is used as an additive in the weight fraction, up to 1% of pure gypsum. The water-to-gypsum ratio was taken at a level of 0.74. The study of hemihydrate calcium sulphate hydration of $\beta$ crystalline form was observed using own-made apparatus measuring the temperature of the system during hydration. The presence of the polymer leads to a retardation of the hydration and setting process of gypsum paste. For the purpose of conductivity measurements, an improved method with a “hot wire” setup was used. A decrease of thermal conductivity and density with added HEMC was observed because of structure modifications of the gypsum product. It was concluded that adding HEMC influences not only the water retention coefficient and the rate of setting of gypsum, it also changes the morphological structure of gypsum-polymer composite, which is reflected in the density and thermal conductivity of the final product.

In shielded mechanized tunneling, the annular gap caused by the tunnel boring machine (TBM) driving must be backfilled instantaneously using a suitable grout. A two-component grout composed of a chemically retarded cement slurry and an accelerator is pumped into the annular gap behind the TBM shield, where it gels and attains sufficient mechanical stiffness in a very short time. This property of the grout helps restrict immediate ground movements adjacent to the TBM tail shield and reduce volume loss. In this study, the hardened two-component mix is tested using a confined oedometric condition, and a complete time-dependent hardening stiffness evolution is developed. Moreover, the freshly prepared grout is tested in terms of its performance suitability (storage and transportation) and serviceability owing to permeability and dewatering. The obtained parameters from the oedometer tests are incorporated into a numerical simulation of an earth pressure balance (EPB) excavation focusing on modeling of the backfilling procedure using finite-difference method (FDM) software. The study also focuses on distinguishing between two commonly used backfilling techniques implemented in numerical analyses. The numerical model consists of testing a regular tunnel section using a newly introduced hardening soil (HS) constitutive model with the soil parameters obtained from the Torino, Italy, metro case. Another set of synthetic softer soil parameters are chosen to highlight the soil properties in the model response. The two-component grout satisfies all the prerequisites for a good backfilling material in its fresh and hardened state. The grout attains sufficient mechanical strength in a very short time, remains impermeable, and achieves a stiffness of 43 MPa in 28 days. The results obtained from the oedometer tests enable development of a complete time-dependent stiffness evolution of the grout. The implementation of hardening behavior of the two-component grout is evident in terms of ground settlements when compared with the conventional backfilling simulation technique.

The present study evaluates the effects of reclaimed asphalt pavement (RAP) binders collected from two different sources (RAP-A and RAP-S) on Superpave performance grade (PG), rutting, and fatigue performance of a polymer-modified binder (PMB). Preliminary rheological investigations on both extracted RAP binders revealed that RAP-A had stiffer binder than RAP-S binder. The PMB was blended with 0, 15, 25, and 40% of RAP-A and RAP-S binders. Superpave PG was determined based on dynamic shear rheometer and bending beam rheometer tests. The rutting and fatigue performance of PMB with varying percentages of RAP binders were evaluated using multiple stress creep recovery and linear amplitude sweep (LAS) tests, respectively. The results showed that the high-temperature PG of PMB bumped by one grade interval; however, low-temperature PG remained unaltered. Although the addition of both RAP binders resulted in a similar PG, their rutting and fatigue performance were found to be significantly different. This showed that same PG of binder may not necessarily have similar performance. Although the addition of RAP binder to PMB increased the stress sensitivity of the PMB-RAP binder blend, the stress sensitivity remained well within the critical limit. The result from the LAS test showed that the addition of RAP binder may adversely affect fatigue resistivity of PMB. Overall, change in performance of PMB was found to be dependent on nature, source, and quantity of RAP binder.

This paper uses information collected from a full-scale untrafficked test section originally constructed for an emergency paving demonstration to determine the short- and longer-term effects of short-term aging on mixture behaviors. Increased haul times (up to 10.5 h) were a primary consideration in the paving demonstration, and this paper discusses the effects of increasing haul time to levels well beyond typical cases. A series of mixture and extracted binder test results were used to characterize the effects of short-term aging on mixtures for up to 5 years after construction in a hot climate. Whereas other studies have reported data to support concern when mixtures are held at elevated temperatures for longer times during construction, haul time effects detected in this work were secondary to parameters which are already used for project acceptance in the southeast United States. Further, the authors suggest that increased short-term aging from hauling or silo storage may have limited effect on mixture performance in certain conditions, as was the case in most analysis phases of this experiment.

In cold regions, freeze-thaw cycles cause airport pavements to exhibit numerous failure modes on the surface, thus affecting the normal operations of the airports. To repair surface damage to airport pavements quickly, efficiently, and cheaply, surface-strengthening materials may be added to the concrete to improve its frost resistance. In the current study, several such materials, namely, concrete protectant, polyurea, epoxy resin, and silane (main ingredients), were tested for their performance in pavement concrete samples. A one-sided freeze-thaw cycle experiment was designed and the mass loss, relative dynamic elastic modulus, saturation, and diffusion coefficient were used to evaluate the frost resistance of the reinforced concrete. In order to calculate the diffusion coefficient, the existing diffusion model was extended to take into account moisture diffusion in concrete during freeze-thaw cycles. The mechanisms of frost resistance were further investigated with the help of scanning electron microscopy (SEM). The results showed that after surface treatments, mass loss and saturation of the concrete decreased, while its relative dynamic elastic modulus increased. The diffusion coefficient exhibited a minimum value with the increase in the number of freeze-thaw cycles, with a cutoff around the 42nd cycle. The results demonstrated that for the selected concrete and four strengthening materials, the condensation reaction products of the silane in particular increased the water and frost resistance of the concrete significantly compared with other surface-strengthening materials. The mass loss of concrete was reduced by 66% and the relative elastic modulus was increased by 64.8% for the silane reinforced sample compared with the unreinforced concrete. The saturation and diffusion coefficient of the concrete were also reduced, demonstrating that, among all materials tested in this research, the silane is the most suitable material for surface strengthening of the airport concrete pavement selected for the research, and its optimum dosage is $4{\mathrm{m}}^2/\mathrm{kg}$.

This study investigates the durability of precast fly ash–based geopolymer concrete (GPC) exposed to an outdoor atmospheric environment for 8 years. Core specimens from GPC culverts are tested to determine the effect of carbonation, permeation properties, and pore-size distribution, and the durability is compared with that of ordinary portland cement (OPC) concrete from the same exposure environment. It is found that the GPC has lower carbonation resistance than OPC concrete. According to mercury intrusion porosimetry (MIP) test results, the porosity of the GPC surface increased with carbonation under field-exposed conditions, whereas no significant changes occurred between laboratory-prepared carbonated and uncarbonated GPC specimens. The GPC produced sodium-based carbonation products that are soluble in water. The surface porosity of the GPC therefore increased, and this process accelerates the carbonation in field conditions. In addition, sorptivity test results correlate well with the MIP analysis and carbonation resistance. Therefore this study reveals that the fly ash–based geopolymer concrete is more susceptible to carbonation in an atmospheric environment.

The use of self-compacting concrete (SCC) has been established; however, novel methods for optimizing and providing suitable workability are still developing. The effect of magnetized water on SCC, by keeping the dosage of superplasticizer constant and reducing the ratio of water-to-cement, was investigated. Results showed a 10% decrease in the amount of water required and a 12% increase in compressive strength. Moreover, the effect of magnetized water on the dosage of superplasticizer in SCC, for making a specific spread diameter ($600\pm 10\mathrm{mm}$) was studied. Results indicated that use of magnetized water in self-compacting concrete can reduce superplasticizer dosage by up 30%.

Bitumen undergoes ageing, which leads to changes in its chemical and rheological properties, causing it to become harder and more brittle with time. This study aims to compare the effects of different laboratory ageing methods on the chemistry and rheology of three bitumen types: a Pen $40/60$, a Pen $70/100$, and a polymer-modified bitumen (PmB). Four ageing protocols were applied: ageing at room temperature, oven ageing, pressure ageing vessel (PAV), and rolling thin-film oven test (RTFOT) combined with PAV ageing. The effects of temperature, pressure, and ageing time were studied using dynamic shear tests and infrared spectroscopy. The results highlight the relationship between chemistry and rheology of bitumen. Bitumen hardening, which was revealed by an increase in complex modulus and a decrease in phase angle, was reflected in the growth of specific chemical functional groups. Among all materials, soft bitumen showed the greater tendency to oxidize. Different behavior was observed for PmB, which presented the highest resistance against oxidation among the studied bitumens, even though the reaction with oxygen caused the deterioration of the added polymer modifiers.

It is difficult to entrain air into roller compacted concrete (RCC) using conventional air entraining agent (AEA) because of its low cement content. This paper examines whether modified absorbent polymer (MAP) can be used as an air entraining admixture to improve both freeze-thaw resistance and strength gain of roller compacted concrete with 40% fly ash content. Modified absorbent polymer is different from superabsorbent polymer because MAP particles are spherical, have low water-absorption capacity, do not entrain additional air by surfactant content, and can release the absorbed water during subsequent hydration. The influence of MAP and AEA on strength and freeze-thaw resistance of RCC is compared. The air void structure and pore structure are evaluated by microscopic imaging, mercury intrusion porosimetry, and nanoindentation. Compared with traditional AEA, the addition of MAP facilitates the formation of a more effective air void network, the improvement of capillary structure, and the enhancement of the strength of the matrix surrounding MAP voids, resulting in significant improvement of freeze-thaw resistance with great increase in strength.

This paper investigates the influence of basalt (B) and hydrated lime (HL) fillers on the rheological and fracture performance behavior of asphalt mastics. A polymer modified asphalt (PMA) binder (PMB-40), basalt (inert filler), and hydrated lime (active filler, are considered for preparation of PMA mastic. Five different combinations of B and HL fillers are selected for the preparation of different PMA mastics with filler:binder ratio of $0.8:1$ (22.5% by volume). The rheological response of PMA mastic is investigated based on Superpave rutting factor, fatigue factor, and linear amplitude sweep (LAS) test results using a dynamic shear rheometer (DSR). Fracture characterization of PMA mastics is evaluated using a double-edge notched tension (DENT) test. Hydrated lime significantly improves rut resistance of PMA mastics at high temperatures. Superpave fatigue factor and LAS test results show that PMA mastic containing high dosages of HL (10–20%) has low resistance to fatigue cracking and is more susceptible to strain amplitude at intermediate temperatures. Mastic without HL predominantly shows better fracture resistance behavior with good critical tip opening displacement (CTOD) value than does PMA mastic containing high dosages of HL (10–20%). High dosages of HL (10–20%) increase high-temperature aging susceptibility by influencing the rheological performance. The PMA mastics are ranked based on various performance parameters. This study shows that the combination of B with high dosages of HL filler may not enhance the fatigue and fracture resistance of PMA mastic.

Cured carbon fiber composite material (CCFCM) is available from manufacturing lines; however, excess CCFCM has no reuse applications at present. Postindustrial CCFCM was mechanically refined and used as reinforcement to improve the mechanical properties of pervious concrete (PC). Four PC mixtures were included in the study, which contained 0 (control), 3, 4, and 5% CCFCM by volume. Infiltration rates of all CCFCM mixtures were above the acceptable level of $\mathrm{1,200}\mathrm{cm}/\mathrm{h}$. Paired t-tests showed that all CCFCM mixtures significantly outperformed the control mixture in terms of split tensile strength by 57–84% and flexural strength by 36–65% in 28-day testing. Load-displacement curves of CCFCM mixtures indicated increases of 41–54% in toughness indices. Mass loss due to Los Angeles machine abrasion (Cantabro) ranged from 16 to 31% for CCFCM mixtures, while the control lost 50% of its original mass. Overall, within the tested range, up to 4% CCFCM addition to PC presented the optimal result across the entire experimental scope. Higher CCFCM contents may be possible if used as a replacement of aggregate rather than an additive to the mixture.

Very few studies have been carried out to investigate the durability and swelling behavior of dredged marine materials. To tackle this issue, this study mainly considers the influence of water immersion and thawing-freezing on the stress-strain characteristics and swelling property of 16 designed soil mixes with cement, lime, and Class-F fly ash. The unconfined compressive strength, failure strain, deformation modulus, and their quantitative corelationships are discussed in detail to evaluate the mechanical performance of stabilized materials damaged by water immersion and thawing-freezing. The result reveals that binder type and binder content have an important influence on the position and shape of stress-strain curves, compressive strength, deformation modulus, failure strain, and failure mode. The derived relationships between unconfined compressive strength and deformation modulus/failure strain are quantified, taking into account ageing effects. To quantitatively estimate the strength degradation, a coefficient of strength loss is defined for evaluating the effect of thawing-freezing and water immersion on compressive strength. Moreover, three-stage modes are proposed for depicting satisfactorily the stress-strain curves and swelling-time curves. A combination of relative swelling percent and absolute swelling amount, which can be reduced by chemical stabilization, is used to reasonably describe the swelling potential of stabilized soils.

To reuse concrete waste in an effective and simple way, compound concrete made of fresh concrete (FC) and coarsely crushed demolished concrete lumps (DCLs) distinctly larger than conventional recycled aggregates has been studied and adopted in actual structural members in recent years. The existing research results focus mainly on the compressive behaviors of compound concrete. In contrast to the previous studies, this paper investigates the tensile-splitting behaviors of the compound concrete. Two series of tests were conducted. In the first series, 24 300-mm cubic specimens with different replacement ratios of DCLs (0, 20, and 30%) were fabricated using normal-strength DCLs and two kinds of FC (normal-strength FC, and high-strength FC), and the tensile-splitting behaviors of the cubes were experimentally studied. In the second series of tests, 64 cubic specimens containing normal-strength DCLs and two kinds of FC with different cube dimensions (150, 200, 300, 400, and 500 mm) and various characteristic sizes of DCLs (50, 67, 100, 133, and 167 mm) were fabricated, and the size effect on the tensile-splitting behaviors of the cubes was experimentally examined. On the basis of the test data, a formula was presented to predict the combined tensile-splitting strength of the compound concrete. It was found that (1) the adverse effect of the DCLs on the combined tensile-splitting strength of the compound concrete did not increase significantly with the increase in the difference between the compressive strength of the fresh concrete and that of the demolished concrete; (2) for the compound concrete containing normal-strength FC, the ratio of the combined tensile-splitting strength to the combined compressive strength was generally close to that for conventional normal-strength concrete, but for compound concrete containing high-strength FC the ratio was approximately 1.1 times that for conventional high-strength concrete; (3) the influence of the characteristic size of the DCLs on the combined tensile-splitting strength of the compound concrete could generally be ignored; and (4) the combined tensile-splitting strength of the compound concrete decreased gradually with the increase in the cube dimension, and the size effect on the combined tensile-splitting strength was similar to that on the tensile-splitting strength of conventional normal-strength concrete.

Wicking occurs in concrete in practice when fluid absorption takes place at one surface of the element and drying at another surface. This paper examines chloride diffusion and wicking in concrete with varying water-to-cement ratios (w/c) and varying cement replacement levels by fly ash and slag. The influence of salt type (NaCl and ${\mathrm{MgCl}}_2$) on chloride transport is examined. The chloride binding capacity is similar for the cement paste with different w/c. The replacement of cement with fly ash and slag increases the bound chloride content. When compared to NaCl solutions, a greater bound chloride content is observed for cement paste exposed to ${\mathrm{MgCl}}_2$ solutions due to the formation of the additional phases, such as calcium oxychloride. Samples exposed to wicking had a greater chloride penetration depth than diffusion alone due to the contribution of advection to the chloride transport. The salt type significantly influences the chloride transport. The penetration depth was observed to be lower in concrete exposed to ${\mathrm{MgCl}}_2$ solution because the additional reaction products form in and block pores for chloride transport. When concrete with a higher w/c is exposed to ${\mathrm{MgCl}}_2$ solution during wicking, there is a larger reduction in the penetration depth compared to that in NaCl solution because the greater amount of $\mathrm{Ca}(\mathrm{OH}{)}_2$ results in the formation of reaction products that block more pores. The reduction in the penetration depth due to blocking by reaction products is less in concrete with fly ash and slag due to the lower content of $\mathrm{Ca}(\mathrm{OH}{)}_2$.

In this study, an eco-olivine nanosilica is produced from natural olivine, and then used as an alternative silicate source in synthesizing the silicate-based alkali activator. The effects of silicate origin and dosage on activator characteristics, fresh behaviors, gel structure, strength, porosity, and shrinkage are investigated. The results indicate that the soluble silica content in the alternative activators is above 98%; compared with the traditional waterglass-based mixes, the nanosilica-derived ones exhibit similar behaviors in the early age reaction, gel structure, and mechanical properties. As some important engineering properties, nanosilica-based mixtures also exhibit increased workability, prolonged setting time, slightly increased porosity, and shrinkage. Thus, by using this alternative silica source in alkali-activated materials, a more sustainable product with less cost and carbon emission can be achieved, and with comparable key performances.

Insufficient bonding strength between a poroelastic road surface (PERS) and a sublayer usually induces premature delamination failure. The objective of this paper was to investigate the shear bonding strength of the PERS-sublayer interface with different bonding agents and develop polyurethane-bound grain (PUG) as an alternative bonding agent. The inclined shear test was utilized to measure shear bonding strengths of control (without bonding agents) and interface-treated samples. The effects of polyurethane content within PERS, sublayer type, temperature, and freeze-thaw conditions on PERS-sublayer shear bonding strengths were investigated for control samples. Shear bonding strengths between the PERS and sublayer with a PUG layer were compared to those with epoxy asphalt and polyurethane for interface-treated samples. It was found that shear bonding strengths between PERS and asphalt-bound sublayers substantially decreased, with the increase of temperature or after one freeze-thaw cycle. Shear bonding strengths between PERS and asphalt-bound sublayers were smaller than the ones between PERS and cement-bound sublayers, regardless of polyurethane content, temperature, or freeze-thaw condition. The PUG layer enhanced PERS-sublayer interface bonding and achieved comparative bonding strength to epoxy asphalt, which was greater than the bonding strength brought by pure polyurethane. A PUG layer with 7% polyurethane produced more than 1.5-MPa shear bonding strength at 60°C for the grain size considered in this study.

The compressive behavior of cement and asphalt mortar (CA mortar, including Types I and II CA mortar, namely CAI and CAII) under strain rates ranging from ${10}^{-5}/\mathrm{s}$ to ${10}^{-2}/\mathrm{s}$ was experimentally investigated using an electrohydraulic servo tester. The strain rate effects on the failure pattern, compressive strength, elastic modulus, and peak strain were studied. The results showed that the compressive strength and elastic modulus of CA mortar increased with increasing strain rate. The peak strain of CAI increased with the strain rate, whereas the peak strain of CAII showed a reverse tendency. At the same strain rate, the compressive strength, elastic modulus, and peak strain of CAI were smaller than those of CAII, but the strain rate sensitivity of the compressive behavior of CAI was stronger than that of CAII. A constitutive model involving the strain rate for CA mortar is proposed based on the theory of thermodynamics and damage mechanics.

The recently developed mechanistic-empirical design method of pavement uses the nationally calibrated dynamic modulus predictive model for the design and analysis of asphalt pavements. This study calibrates this model for the local Superpave asphalt concrete mixtures of New Mexico. Although the calibrated model shows good correlation, this study develops a new regression-based model which shows improved correlation with the tested data. A total of 54 asphalt-aggregate mixtures are compacted, cored, and sawed to cylindrical specimens and tested for dynamic modulus and phase angle. The time-temperature superposition principle is applied to develop master curves at a reference temperature of 70°F (21.1°C). The master curve parameters are correlated with the aggregate and binder properties. The local predictive models are validated for the dynamic modulus and phase angle of other AC mixtures which were not used to develop the models. Statistical evaluation shows that fairly accurate estimations of dynamic modulus and phase angle of the local mixes are possible by using these local predictive models.

This paper explores a new way to recycle wasted radiation-proof cloths and produced a cost-effective material for electromagnetic shielding. Chopped fiber (CF), produced from radiation-proof cloths made from copper-plated Dacron (CPD) and silver-plated Dacron (SPD), is used as the conductive material to manufacture electromagnetic interference (EMI)-shielding mortars. The electrical resistivity and strength of CF mortar is investigated. The effects of CF content, CF length, and sample thickness on the shielding effectiveness (SE) in the frequency range 0.3–3,000 MHz is studied. Test results show that the electrical resistivity decreases rapidly with the increase of CF content. The addition of CPD could improve both compressive and flexural strength of mortar. The compressive strength increases and the flexure strength decreases with the addition of SPD. The maximum compressive strength reaches 40.9 and 36.5 MPa for CPD and SPD mortars, respectively. The SE curves have small difference for these two types of mortars. The increase of CF content, CF length, and sample thickness could all enhance the SE, but to a different extent. For this type of mortar, the maximum peak value of 47.7 dB is obtained at a frequency of 2,470 MHz with a thickness of 30 mm.

The upgrading and evaluation of waste paper sludge fly ash (PsFA) as a cement substitute in wood-wool composite boards (WWCB) is investigated in the present study. This type of board is widely applied in the building environment because of its excellent thermal and acoustical properties; however, cement is still widely used as a binder although environmentally its use leads to a high ${\mathrm{CO}}_2$ footprint of the composite and is therefore less favorable for sustainable building designs. Paper sludge fly ash could be a feasible replacement of cement; however, its high water demand limits the substitution level to 10% by mass of binder. Therefore, different upgrading methods including water treatment and thermal treatment are performed, and their effects are evaluated using various analytical methods. Afterward, PsFA’s suitability as a binder replacer in WWCB is investigated with the hypothesis to refine the microstructure of the boards, resulting in extra lightweight properties. A substitution level of binder with the upgraded PsFA by 20–60% in WWCB can be achieved and is confirmed by the improved mechanical, thermal-insulating, and sound-absorbing properties.

Dealing with dredged clay with high water content has become a difficult issue in recent years. The admixture addition of polyacrylamide (PAM) to dredged clay to improve its poor engineering properties has become a trend. This study presents a laboratory investigation of the effects of the addition of polyacrylamide on the consolidation behavior of dredged clay. A series of oedometer tests was conducted on PAM specimens in both normally consolidated (NC) and overconsolidated (OC) states. The test results show that in the NC state, the weak engineering properties of dredged clay were improved by the PAM addition. The initial water content of the samples with PAM after filtration tests decreased by 45% compared to natural samples without PAM. The structural yield stress and coefficient of consolidation of samples with PAM were two times higher than those of untreated samples. A predictable model of the coefficient of secondary compression was obtained for Tianjin Binhai dredged clay. In the OC state, the coefficient of consolidation decreased with the increase in PAM content. An overconsolidation ratio (OCR) of 2.0 is the threshold value for evaluating the critical settlement between primary and secondary compression. The coefficient of secondary compression decreased linearly with increasing OCR and a linear model for predicting secondary compression is proposed. The addition of PAM can be beneficial ($50\mathrm{m}\mathrm{g}/\mathrm{L}$ for Tianjin Binhai dredged clay) to accelerate the consolidation process, reduce secondary compression, and reduce project costs.

This paper presents a new cyclic piecewise linear pull-out push-in shear-lag material model representing the local bond behavior of preconstruction-installed steel anchor bolts for concrete. Impact loading resulting from a Schmidt hammer is used to evaluate the bond quality between the steel bolt and the surrounding concrete. The impact loading results in microcracking at the interface of steel bolt. The bond between the steel bolt and the surrounding concrete is modeled as a nonlinear interface. Each loading cycle is modeled by dividing it into six portions, namely elastic loading, interfacial cracking, unloading, reloading in the push-in direction accompanied by interfacial cracking, unloading, and reloading in the pull-out direction. The model incorporates stiffness degeneration caused by interfacial cracking and stiffness recovery caused by the lateral pressure effect along with Poisson’s effect. Rules formulated by trial and error for plotting cyclic pull-out push-in deformational response of steel bolts are presented. The validity of the presented rules is judged by comparing their cyclic deformational response with a finite-element simulation, and experimental deformational response and good agreement is found. The developed cyclic rules can be used for simulating the deformational response of preconstruction-installed steel anchor bolts.

This study investigated the fatigue cracking mechanism of asphalt mixtures by synergizing crack initiation and propagation at varying temperatures and mix variants. An advanced approach to the dynamic semicircular bending (SCB) test was utilized to evaluate the fatigue mechanism of 18 asphalt mixtures totaling 648 SCB specimens. Based on crack growth and crack mouth opening displacement analyses, distinctive cracking mechanisms were recorded for three different asphalt mixture types. Further, predictive models were developed to estimate the different stages of fatigue based on fundamental materials properties. Overall, the adopted methodology conveniently distinguished cracking characteristics with respect to crack initiation and propagation at different temperatures.

This paper presents discrete element method (DEM) simulation results of the plastic deformation behavior of asphalt concrete(AC) subjected to the loading of the asphalt mixture performance test. This consists of a repetitive vertical axial stress of 690 kPa for 0.1 s followed by a rest period of 0.9 s. Nine ACs were considered; three mix designs and three aggregate types. A single PG 76-22 modified binder was used for all nine mixes. Their microstructure was captured by X-ray tomography and the images processed were input into a DEM software package. The viscoelastic properties of the asphalt mastics were obtained by fitting Burgers models on frequency sweep dynamic shear rheometer data. These models were used to define viscoelastic contact laws for the mastics. These mastic contacts were assumed broken (i.e., the elastic constants of the Burgers models were set to zero) where the limits in linear viscoelastic behavior were exceeded. Flow number (FN) values were obtained by fitting the Francken model to the computed plastic deformation estimates. The results compared favorably to laboratory rutting measurements obtained on the same cores with the Hamburg wheel testing device (HWTD). The plastic strain at FN and the plastic strain rate at FN exhibited higher correlation with the HWTD rutting measurements than the FN values.

The morphology of aggregates has a significant effect on the mechanical performance of aggregate-based materials such as asphalt concrete and cement concrete. This paper obtains shape indexes of aggregates, including aggregate sieve size, orientation, sphericity, and volume. The four indexes can be obtained through a virtual measurement method based on the minimum axis-aligned bounding box (AABB) of a three-dimensional (3D) solid model of aggregate. The methodology consists of three main steps: (1) the 3D solid model of each aggregate is developed from X-ray computed tomography (CT) images for aggregate cross sections, and the aggregate sphericity and volume are calculated; (2) the 3D aggregate model is rotated from the initial orientation to find a target orientation at which a minimum AABB occurs; based on that, the aggregate initial orientation is determined by the direction of the longest side of the minimum AABB and the angle rotated; and (3) the searching route for the cross section that determines the sieve size of the aggregate is computed, and the cross section with the longest length is identified to calculate the aggregate sieve size. The 3D solid models developed in this paper are very close to real aggregates, and contain intact geometric boundary information in their 3D internal structures. Laboratory measurement indicates that the virtual measurement method can significantly facilitate the accuracy, efficiency, and automation of aggregate shape characterization.

This study evaluated the feasibility of using waste engine oil (WEO) to partially replace virgin asphalt binder. Two base asphalt binders (PG 64-28 and PG 76-22) were blended with three different WEO percentages of 0, 5, and 10%, respectively. First, the effects of WEO on two base asphalt binders were evaluated by the mass loss during rolling thin film oven (RTFO) and by performance grading (PG) test. Second, based on the developed WEO-PG formula, two binders were designed to have equivalent low temperature PG. Subsequently, the rheological properties of these two low-PG-equivalent binders were evaluated by PG, multiple stress creep recovery (MSCR), frequency sweep, and monotonic fracture tests. Results of the study showed that use of higher WEO content resulted in a decreased PG for base asphalt binder, but the amount of decrease was dependent on the base asphalt type. With the presence of WEO, the binders having equivalent low-temperature PG did not necessarily exhibit similar stiffness or fracture property. WEO had a softening effect, and an improved elasticity and recovery property on the base asphalt.

The need for long-term performance of rail infrastructure has now become imperative because heavy-haul railways are expected to withstand higher speeds and heavier axle loads, especially for enhanced productivity in mining and agriculture sectors. However, the degradation of ballast particles and associated track deformation impose a significant impact on the cost of maintenance. Although various existing techniques can be used to reduce the extent and frequency of maintenance without removing the superstructure, this study elucidates a novel method of confining the upper subballast stratum (i.e., capping) with energy-absorbing rubber tire cells to provide increased stability and resiliency to the track substructure. The results of this study verify that a capping layer confined with recycled rubber tire cells can actively reduce ballast degradation and particle movement within the track substructure. A favorable reduction in track settlement and lateral spreading of particles is also attained when broadly-graded finer gravels are selected to form a compacted capping layer just beneath the ballast layer.

Powder X-ray diffraction is a time-consuming and challenging task, especially for preparation of sensitive phases like ettringite and calcium-silicate-hydrate (C-S-H) phases. Fine-grained ultrahigh-performance concrete (UHPC) with an average grain size $<100\mathrm{\mu m}$ could be investigated directly without time-consuming milling. As a proof of concept, small UHPC cylinders with plain surfaces were investigated with a newly designed sample holder. The comparison with conventionally prepared powder shows the feasibility of fast qualitative phase analysis using this approach. As a great benefit, a depth-dependent analysis, as well as a comparison of surface layers and core material, was carried out.