Journal of Materials in Civil Engineering

Short-term oven aging (STOA) is used in current practice to simulate typical aging of asphalt mixtures during plant production and field construction. This study compares the volumetrics and performance of laboratory-produced asphalt mixtures and corresponding plant-produced mixtures to examine whether STOA simulates plant short-term aging. Eight plant-produced mixtures with varying levels of binder performance grade, binder content, filler content, and traffic design levels were tested for rutting and cracking resistance using Hamburg wheel-tracking (HWT) and semicircular bending (SCB) tests, respectively. The eight mixtures were duplicated in the laboratory and subjected to 2 h of reheating and 2 h of oven aging before testing. The eight lab-produced mixtures had comparable volumetric properties to the plant-produced mixtures, and the performance results showed a relatively high level of equality between plant- and lab-produced mixtures even when the properties of their extracted and recovered binders at high and intermediate temperatures are found to be significantly different. Based on the findings of this study, the use of the outlined STOA procedure is considered sufficient to represent standard plant production aging.

The significant influence of silica nonplastic fines content on the small-strain Young’s modulus and Poisson’s ratio of silty sands has been evaluated through a comprehensive set of resonant column tests in the flexural mode of excitation. It is demonstrated that at low fines contents, sand properties have a significant impact on the dynamic behavior of the soil; however, the silt inclusion is the predominant feature controlling Young’s modulus beyond a specific proportion of fines content. Based on the flexural resonant column tests performed on the sand–silt mixture specimens with variable parent sand materials in terms of uniformity coefficient and particle shape, a new expression is established for the evaluation of the small-strain dynamic Young’s modulus of silty sands using the concept of equivalent granular void ratio. Having a typical micromechanical discussion, the influence of confining pressure, particle shape, and fines content on the small-strain stiffness of sand–silt mixtures are thoroughly described. Furthermore, invoking the theory of elasticity, the variation of Poisson’s ratio with fines content for sand–silt mixtures is discussed.

Seawater sea sand concrete (SSC) can be applied in islands far away from the mainland. It is essential to clarify the fracture behavior of SSC which is related to the durability under the ocean environment. Thus, the present study is primarily concerned with the determination of fracture parameters of SSC. Ordinary concrete (OC) mixed by freshwater and river sand is introduced for reference. Based on the improved boundary effect model, the size-independent tensile strength and fracture toughness are determined by using the experimental maximum fracture loads of three-point-bending concrete beams. The resulting tensile strength is adopted to replace the maximum tensile stress at the fictitious crack-tip in the maximum fracture load model and the former proves to be the latter. The maximum fracture load related to the local fracture energy at the crack-tip region is then predicted. The size-independent fracture energy is given by the comparison between the analytical and experimental maximum fracture loads. The local fracture energy distributions in the SSC and OC are similar to each other. But the tensile strengths of SSC are higher than those of OC. The fracture toughness and fracture energy increase with the increasing of maximum aggregate size for SSC.

Although the absence of portland cement (PC) in alkali-activated slag (AAS) lowers its carbon footprint, conventional alkaline activators like sodium silicate are expensive and have large environmental impacts. Soda solid waste (SSW) is an alkaline waste of the glass industry, and its disposal poses environmental problems. This study investigated the use of SSW to activate ground slag at 60°C–120°C. Strength development of mortars and heat evolution of pastes were evaluated. Hydration products were studied using X-ray diffraction and thermal analysis. Strength gain, rapid in the first 3–7 days, is attributed to formation of amorphous phases and partly crystalline calcium silicate hydrate (C-S-H). Increasing SSW content causes a weaker and broader rate of heat evolution peak in the first few hours and evolves greater total heat in the first day. SSW-activated slag pastes evolve significantly less heat up to 7 days than a typical room-temperature-cured PC paste but similar when heat is normalized by compressive strength. Mortars containing 40% slag and 60% SSW reach $\sim 20\mathrm{MPa}$ after 7 days of curing at 120°C.

Air-cooled blast furnace slag (ACBFS) can be used to replace naturally mined aggregates to minimize the environmental and economic costs associated with construction. This paper compares pore solution chemistry of mortars prepared using ACBFS aggregate with pore solution chemistry of control mortars (i.e., mortars containing siliceous sand). The objective of the study was to evaluate the effects of the chemistry of ACBFS particles on the composition of the pore solution and how this chemistry may influence the process of hydration in cementitious systems incorporating ACBFS aggregate. The chemical composition of pore solutions was determined using the inductively coupled plasma optical emission spectroscopy (ICP-OES) technique. During the initial hydration period ($<5\mathrm{h}$), the concentration of sulfur in the pore solution of mortars was not affected by the presence of ACBFS aggregate. However, after 7 days of hydration, the concentration of sulfur in mortars containing ACBFS aggregate was 3.4–5.6 times higher than that observed in corresponding control mortars. Thermogravimetric analysis of mortars revealed that those containing the ACBFS aggregate underwent a lower degree of hydration compared to control mortars. For mortars with and without ACBFS aggregate, partial replacement of Type I ordinary portland cement (OPC) with fly ash reduced the concentration of sulfur in pore solutions after 7 days of hydration when compared with corresponding mortars prepared using only Type I OPC or a blend of Type I OPC and slag cement.

The utilization of Yellow River alluvial silt as the main filler for railway embankments can lead to a series of embankment problems. Therefore, the silt must be improved before it can be used. In this paper, a series of cyclic triaxial tests were performed to find an optimum percentage of composition of lignin–lime combined additive. According to the shakedown concept, permanent deformation of silt samples stabilized by different proportions of additives was classified and evaluated. The recommended proportions from unconfined compressive strength tests were verified, and the optimal proportion of additive was obtained. In addition, under different confining pressures and relative compactions, shakedown behavior of stabilized silt samples with optimal additive proportion was investigated. The experimental results revealed that the plastic shakedown limit and plastic creep limit of silt samples with 6% lignin and 3% lime were 4 and 8 times those of untreated silt samples, respectively. With the increase of confining pressure and relative compaction, the permanent deformation of the stabilized silt was reduced, and its shakedown limits were enhanced.

Current limited guidance on the selection of screws together with undefined design specifications restricts the effectiveness of self-tapping screws as reinforcement on timber members to control crack propagation. Using digital image correlation (DIC), this study visualized the surface strain distribution of screw-reinforced dowel-type connections to understand the influence of thread configuration and screw-to-dowel distance on controlling crack propagation. The experiment was based on single-dowel embedment tests using 16- and 20-mm-diameter steel dowels. Three thread lengths (0%, 33%, and 100% thread) and six screw-to-dowel distances ($0.5d$, $0.75d$, $1d$, $1.5d$, $2d$, and $4d$) were investigated. Results show that a screw with 33% thread on the point end can be as effective as screws with 100% thread to control crack propagation under the same geometrical parameters of the connections. Results also reveal that a screw placed further from the dowel (e.g., at $2d$ distance) can delay the crack-controlling effect. Self-tapping screws placed at $2d$ can still improve the embedment strength and ductility; however, further doubling this distance ($4d$) did not enhance the embedment strength, but a higher ductility was still achieved.

Methodologies for dosing fine/coarse-grained soils with cement using the porosity/cement ratio ($\eta /C_{iv}$) have mainly focused on the nonoptimal compaction conditions to calculate the split tensile and compressive strengths as well as the empirical relationships between both tests, neglecting the study on the optimal soil-cement mixes compaction conditions. Thus, this technical paper aims to determine the equations that control the empirical relationships between split tensile (STS or $q_t$) and unconfined compressive strengths (UCS or $q_u$) of a sedimentary soil improved with portland cement (PC) under optimal compaction conditions using the $\eta /C_{iv}$ ratio. The results showed a power increase of $q_t$ and $q_u$ with the curing time and the decrease of $\eta /C_{iv}$ ratio. In addition, it has been demonstrated that a relationship between tensile and compression might be defined using the $\eta /C_{iv}$ ratio adjusted to an exponent $\beta =0.45$, constant for all curing times. Therefore, the tensile/compression ratio obtained was 0.15, 0.16, and 0.17 for the 7th, 14th, and 28th days of cure, respectively. All $q_t$ and $q_u$ data were normalized (divided) into a single power increase function (93% acceptance with a 4.36% error) to find any mechanical resistance value with variables and molding conditions using the $\eta /C_{iv}^{0.45}$ ratio. Finally, the $\eta /C_{iv}$ ratio was a suitable parameter for dosing soil-cement mixes under optimal compaction conditions.

Like every other organic compound, asphalt binder experiences aging over time, which significantly affects its chemical and physical properties. This study was the extension of a series of previous research studies in an attempt to evaluate the amorphous carbon-modified binders as a byproduct of paraffin factory when added in asphalt binder. A novel approach was taken in this research study to evaluate the aging properties of amorphous powder. Historically, it is believed that carbon powder can improve the aging of asphalt binder; however, the methods for such a claim are not designed well for long-term evaluation. This study used a time-temperature-aging superposing principle that added an aging component to the well-known time-temperature superposition principle to evaluate the aging properties of amorphous-modified binders comprehensively. This methodology was verified with a chemical test, Fourier-transform infrared (FTIR) spectroscopy. The master curve results, along with chemical properties, showed as binder aged, the rate of aging decreased. The chemical results indicated the benefits of amorphous powder against aging to some extent; however, due to added stiffness of this powder that acted as filler in binder, the master curve of aging showed higher stiffness values for samples modified with 10% amorphous carbon compared to 5% and 0% binders.

Yujia Memorial Archway in Jixian County, Hunan Province, can be considered a typical weathered stone artifact. Different ratios of 3-glycidyl ether propyl trimethoxy silane (GPTMS), 3-amino propyl triethoxy silane (ATS), and hydroxy silicone oil (PDMS-OH) were used to achieve in situ reinforcement of representative weathered stone samples, considering the permeability of the reinforcing material, its compressive strength, and weatherability. In a preliminary assessment, a reaction mechanism of interpenetrating hybrid organic–inorganic networks that can be bonded to the interface between the reinforcement material and the stone artifact is proposed. The amino group attacks the epoxy group by nucleophilic reaction to open the ring; a dehydration condensation occurs to form an epoxy organic network structure, while the silane hydrolyzes and condenses to form a Si-O-Si inorganic network structure. More importantly, the addition of PDMS-OH increases the flexibility and hydrophobicity of the material, further improving overall performance. A multiangle and multilevel comprehensive analysis of the composition, structure, hydrophobicity, macroscopic morphology, and microscopic morphology of the composites was carried out using Fourier transform infrared spectroscopy, Raman, scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction, and other techniques. The restoration materials were applied to the weathered stone samples, and the restoration effect was evaluated for the permeability, compressive strength, water absorption, acid resistance, salt resistance, and freeze-thaw resistance of the strengthened samples. The results show that a GPTMS:ATS:PDMS-OH ratio of $14:7:9$ is the best and can be applied to the in situ reinforcement of dolomite rocks.

A series of pullout tests were conducted to investigate the bond characteristics of deformed high-strength steel bars embedded in ultrahigh-performance concrete (UHPC). This study considered different fiber volume contents, bar diameters, bar embedment lengths, concrete covers, and bar grades. Pullout force, slip at the free end of the bar, and crack patterns were measured, and bond failure modes were investigated. New results are reported regarding bond strength increase with fiber volume content (up to 3%), bar diameter, and bar grade. The thickness of the concrete cover significantly affected the bond failure mode. UHPC had considerable energy absorption capacity due to debonding and pullout of steel fibers from the matrix. A theoretical formula and a simplified formula to evaluate the splitting bond strength are proposed, which are consistent with the experimental results.

This study focused on the evaluation of the mechanical and durability aspects of stabilized poorly graded sandy soil by activated blast furnace slag cements (ASCs) with three different activators with combinations of ${\mathrm{Na}}_2{\mathrm{SiO}}_3$ and NaOH (PN), ${\mathrm{Na}}_2{\mathrm{CO}}_3$ and $\mathrm{Ca}(\mathrm{OH}{)}_2$ (PC), and ${\mathrm{Na}}_2{\mathrm{SO}}_4$ and $\mathrm{Ca}(\mathrm{OH}{)}_2$ (PS). Type of activators, binder percentage, and curing time were investigated as parameters. The results of unconfined compression strength (UCS) of samples in a constant amount of binder/soil (5-wt%) showed an increase from 0.75-MPa for ordinary portland cement (OPC)-based samples to 2.28, 2.63, and 4.5-MPa for PC-, PN-, and PS-based samples, respectively. Due to its high UCS sample value, the activator considered most effective is PS based. The formed gel between the soil’s particles results from the dense microstructure and fewer voids in the sample suggests a higher interaction level between soil and binder. PS- and PC-based binders showed more ductility than OPC-based stabilized soil. Moreover, ASC samples showed better soundness than OPC samples, due to less volume changes, stronger bonds between soil particles, binder matrix, and absence of destructive expansion.

Tricalcium aluminate (${\mathrm{C}}_3\mathrm{A}$) is the most reactive phase in portland cement clinker. In the study of the ${\mathrm{C}}_3\mathrm{A}$ hydration process, the use of synthetic samples is often preferred over clinker-sourced samples due to the absence of traces of other elements in synthetic ${\mathrm{C}}_3\mathrm{A}$. However, the reproduction of results from synthetic samples using clinker-sourced ${\mathrm{C}}_3\mathrm{A}$ samples is challenging due to the difficulty of complete extraction of aluminate phases from clinkers without damaging their structure. Salicylic and maleic acid/methanol solutions were used in the past to isolate ${\mathrm{C}}_3\mathrm{A}$, but complete extraction has not been observed. Thus, it was necessary to modify the selective dissolution (SD) method. Possible processes were tested with white and ordinary portland clinkers. A modified process with maleic acid/methanol solution was developed and the samples were analyzed by X-ray diffraction (XRD), thermogravimetric analysis (TGA), and Raman spectroscopy, compared with synthetic ${\mathrm{C}}_3\mathrm{A}$ samples. The modified selective dissolution process with maleic acid/methanol solution proposed in this work was effective in achieving complete isolation of aluminate-based phases, and can be used for further studies of the hydration process of clinker-sourced ${\mathrm{C}}_3\mathrm{A}$ samples to improve the understanding and quality of portland cement clinkers.

This study investigated the hydration mechanism of gypsum–slag cement gel. Experimental results indicated that products of hydration of gypsum slag cement gel materials were predominantly zeolite minerals and amorphous gel materials that had a chemical structure similar to that of zeolites mineral. Under standard curing conditions, rodlike and cubic shapes of zeolite minerals formed with a relatively small crystal sizes. Citrate retarders were able to control the generation mechanism of various minerals in slurry; change the hydration products in the semihydrated gypsum with respect to concretion, numbers, and percentage before hardening; and affect the structure of the hardened products.

This work addresses the effect of time, temperature, airflow rate, and weight of asphalt binder on the laboratory short-term aging of asphalt binders and proposes an alternative protocol that can reduce the aging time and resolve some of the current short-term aging protocol shortcomings. In the first part of this study, two asphalt binders from different sources were examined in a rolling thin-film oven at different combinations of the aforementioned test parameters. The high-end continuous performance grading temperature and carbonyl index were considered as the two responses for quantification and qualification of laboratory aging. The statistical analysis showed that the first-order terms of time, temperature, and weight as well as their interactive terms were statistically significant. However, the effect of airflow rate within the studied range was insignificant. Based on the findings of the first part of study, an alternative protocol was proposed for the study of short-term aging in a rolling thin-film oven. One unmodified and three highly modified binders were aged in a rolling thin-film oven under the current and proposed aging conditions for comparative purposes. According to the obtained rheological properties (high- and low-end continuous performance grading temperature and viscosity) as well as the chemical characteristics (carbonyl index, saturate-aromatic-resin-asphaltene fractions, and oxygen content), it was shown that the proposed laboratory short-term aging protocol not only can reduce the aging time of the conventional protocol, but also that it is applicable to both unmodified and polymer-modified asphalt binders.

A new type of three-layer waterproof structure was developed to reduce the scour problem of concrete slabs by paving an asphalt-based composite seal layer between the cement-stabilized base and the cement concrete pavement. The asphalt-based composite seal layer consists of an upper layer (microsurfacing), a transition layer (microsurfacing), and a bottom layer (synchronous chip seal). A new construction method was proposed to guide the construction of the asphalt-based composite seal layer. The waterproof and antiscouring properties of the asphalt-based composite seal layer were evaluated by a permeability test, a high-resolution industrial computed tomography (CT) scanner, a scouring test, and a direct shear test. The permeability test showed that the three-layer structure possessed good waterproofing properties. The CT scans results showed that the asphalt-based composite seal layer was very dense due to effective compaction during the construction process. The scouring test indicated that the scouring resistance of the asphalt-based composite seal layer was much better than that of the cement-stabilized base. The results showed that the asphalt-based composite seal possessed decent resistance to scour and could effectively protect the base from the threat of scour. The cost analysis results showed that the proposed asphalt-based composite seal layer has a more competitive unit price compared with an asphalt concrete layer.

This paper aimed to investigate the corrosion mechanisms of stirrups in concrete, considering the macrocell current between stirrup and longitudinal rebar. The impacts of relative humidity (RH) and area ratio of stirrup to longitudinal rebar were studied. To avoid mechanical damage like bending on the corrosion activity of stirrups, straight stirrups were used in concrete specimens. Corrosion experiments of concrete were carried out under a simulated marine atmospheric environment. Measurements of polarization curves and macrocell currents were performed to calculate the increase of the total anodic current of stirrups due to the macrocell current by means of curve-fitting analysis. The results showed that the microcell corrosion is the major mechanism in the corrosion of stirrups under different RH conditions. Results also indicated that as RH increased, microcell and macrocell corrosion current densities increased, whereas the galvanic coupling effect that was used to quantify the increase of the total current density of stirrups decreased.

To understand the performance of desulfurized rubber asphalt (DRA) and its application feasibility comprehensively, the road performance, viscosity–temperature characteristics, rheological properties, storage stability, aging resistance, and environmental performance of DRA were investigated and compared with ordinary rubber (hereinafter called rubberized rubber) asphalt. The test results showed that rubberized rubber asphalt (RRA) performs better than DRA in elastic recovery, aging resistance, and rutting resistance, but DRA performs better than RRA in storage stability and low-temperature performance. DRA has similar fatigue resistance as RRA. Compared with RRA, the construction temperature of DRA can be reduced by about 30°C, which means that DRA has better workability. The performance grade (PG) of DRA was classified as PG 76-34, which indicates that DRA has a wider temperature range and can be applied to lower-temperature environments. In addition, the harmful gas emission of DRA is lower than that of RRA, so DRA is more environmentally friendly. Therefore, it is necessary to modify DRA with compound methodologies to enlarge its application.

The use of seawater and recycled coarse aggregate (RCA) in concrete mixtures leads to the production of a very sustainable concrete. The potential risk of steel reinforcement corrosion (due to chloride in the seawater) in such mixtures may be eliminated when considering plain concrete or noncorrosive reinforcement (e.g., fiber-reinforced polymer). This study investigated the fresh and hardened properties of a proposed green concrete mixed using seawater and recycled coarse aggregates. Two different concrete mixtures were studied, namely conventional concrete (Mix 1) and seawater-mixed concrete with RCA (Mix 2). Blast furnace slag was used as supplementary cementitious material at a 65% replacement level in both concrete mixtures. Fresh and hardened properties of the two concretes, including workability, strength gain, drying shrinkage, permeability, and microstructure, were characterized and compared. The results suggest that the use of seawater and RCA together has negative effects on concrete performance. Compared with the reference (Mix 1), Mix 2 concrete had approximately 5% lower density, 25% lower slump flow, 50% lower setting time, 33% lower strength gain, 10% higher drying shrinkage, 60% higher water absorption, and 100% higher charge passed (in rapid chloride permeability tests). Consequently, strategies to improve the performance of such concretes, such as a reduction in the water:cementitious materials ratio and the use of chemical admixtures, are suggested. These strategies, however, may somewhat reduce the green aspect of the proposed seawater-mixed concrete with RCA.

Resistance to permanent deformation is the primary performance indicator of unbound aggregate pavement layers. In relation to the applied wheel-load deviator stress, the shear strength property of a confined base/subbase controls the rate of permanent strain accumulation in that aggregate layer. The objective of this study was to quantify the impact of aggregate properties on the shear strength and permanent deformation characteristics of unbound aggregates. Sixteen different aggregates were studied in the laboratory for two different gradations: original quarry source and engineered midrange gradations. Aggregate specimens were prepared at these gradations to determine moisture-density relationships, and conduct monotonic and repeated load triaxial tests at the target maximum dry densities and optimal moisture contents. In addition, imaging-based aggregate particle shapes or morphological indices were obtained. The laboratory findings indicated that the particle size corresponded to 60% passing, and imaging-based angularity index contributed significantly to the increases in the shear strength properties of aggregates, which were also affected by density and moisture content. Permanent strain accumulations were primarily influenced by applied shear stress in relation to the shear strength of aggregates, and rutting model parameters obtained through regression analyses were influenced by applied stress, strength, and material properties. Further, an aggregate with plastic fines showed the highest permanent strain accumulation, hence clearly indicating the significant influence of plasticity of fines on the permanent strain accumulation.

The bond between concrete and steel bars defines the structural behavior of reinforced concrete—each is the complement of the other. The bond allows for the compatibility of strains, transmission of stresses, and good mechanical behavior, with less possibility of the concrete cracking; this can result in the protection of the reinforcement and a higher structural durability. This study investigates (1) the bond behavior between concrete and steel bars, and (2) the development length of steel bars in steel fiber-reinforced concrete (SFRC). For the tests, the bars had diameters of 8 and 12.5 mm with full development lengths ($l_b$), and with reductions of 50% ($0.5·l_b$) and 25% ($0.75·l_b$). The volume fraction of steel fibers ($V_f$) had values of 0.0%, 0.5%, and 1.5%. In the results, the flexural ultimate loading for SFRC was higher than for nonfiber-reinforced concrete. For samples with a $V_f$ of 1.5%, the bond strength was higher than that found in other concretes, confirming that the use of steel fibers improved the bond between concrete and reinforcement and the effectiveness of the proposed test system.

This research developed an ultra-high-performance engineered cementitious composite (UHP-ECC), which combines the properties of strain-hardening, multiple cracking, and high mechanical strength. The compressive strength of the UHP-ECC reached 150 MPa at 28 days under standard curing conditions, whereas the tensile strength and strain capacity of the UHP-ECC were 18 MPa and 8%, respectively. Different fiber volumetric ratios and geometries (fiber length and diameter) were used to investigate the influences of fiber-reinforcement parameters on the mechanical and crack-pattern properties of UHP-ECC, including the tensile strength, strain capacity, strain energy, crack number, and crack spacing. It was found that the fiber reinforcement parameters significantly influence both the mechanical properties and crack-patterns of UHP-ECC. Based on the test results, a bilinear tensile stress–strain model was proposed for UHP-ECC and its accuracy was demonstrated through comparisons with the test results.

Sandy lean clay (SLC) has a high content of fine sand and silt with poor compressibility and water stability. It threatens the structural stability of highways in regions where this soil type is common. Improvement of SLC for enhancing highway structural stability has attracted wide research interest. Therefore, based on a study of the basic physical-mechanical characteristics of sandy lean clay along the Puyong Expressway, the water stability of the compacted soils was investigated based on a series of indices, including cohesion, angle of internal friction, and degree of compaction. The characteristics of cement- or lime-treated soil were also studied. The results show that the water status has a great effect on the cohesion of SLC. The soaked California bearing ratio (CBR) for untreated SLC was only about 3% to 37% that of unsoaked CBR, depending on the moisture content, indicating that untreated SLC has very weak water stability. It is suggested that the water content of SLC should be controlled at a level slightly higher than the optimal moisture content (${\omega }_{\mathrm{opt}}+2\%$) during compaction. The degree of compaction should not be used as the compaction quality control index when the subgrade is filled with SLC. CBR and other strength indicators should be used as the compaction quality control indices of SLC subgrade. Based on the results of numerical simulations using the finite-element method, improvement measures of each layer and the corresponding waterproof measures of the SLC subgrade are recommended when the embankment is 25 m thick.

To improve the durability of color antiskid pavement and the abrasion resistance of its antiskid particles, an organic treatment agent (OTA) is selected to treat the antiskid particles. The before-and-after study of the OTA treatment on the properties of the antiskid particles is conducted. The abrasion resistance of color antiskid pavement is discussed by using four evaluation indexes: abrasion mass loss rate, British pendulum number attenuation rate, texture depth attenuation rate, and bond strength. In addition, the color durability of color antiskid pavement under single and complex conditions is studied by using the color brightness coefficient as the evaluation index. Compared with untreated antiskid particles, the OTA demonstrates a 54%, 29%, 44%, and 34% reduction in water absorption, weared stone value, crushed stone value, and mass abrasion shedding rate, respectively, on the treated particles. Furthermore, the OTA produces a 5%, 16.7%, and 9.7% decrease in abrasion mass loss rate, British pendulum number attenuation rate, and texture depth attenuation rate, respectively, whereas it produces a 33.3% increase in bond strength, compared with untreated specimens. Moreover, under four conditions: liquid corrosion, ultraviolet radiation, combined high-temperature and liquid corrosion, and combined high-temperature and ultraviolet radiation, the maximum reduction of the color brightness coefficient of color antiskid pavement with OTA treatment is 85.8%.

Concretes at different saturation degrees are needed to be prepared in the laboratory when studying the effects of humidity on its mechanical properties. Different humidity control methods would produce different results. The present work investigates the changes in compressive behavior and microstructure of the ordinary concrete caused by two different humidity-controlling modes: (1) the isothermal drying humidity-controlling mode and (2) the rewetting humidity-controlling mode. The compressive behaviors of concrete in different humidity states are compared, and the microstructure is studied in detail using scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP). The results indicate that drying results in an increase of compressive strength, whereas rewetting results in a significant decrease. Both drying and rewetting humidity-controlling modes cause some changes in the microstructure of concrete. Drying results in calcium silicate hydrate (C-S-H) globule densification and makes cement matrix denser, increases porosity, and coarsens the pore size distribution. Rewetting makes porosity decrease and the pore size distribution slightly refined, as well as causes serious microcracking. The differences in compressive behavior of concrete is related to the shrinkage or swelling, the change of pore size distribution, and the microcracking caused by two different humidity-controlling modes. The isothermal drying humidity-controlling mode is suggested as the more reasonable mode for concrete because it is more effective in controlling saturation degree, takes less experiment time, and causes less effect on microstructure and the compressive strength of concrete.

Early-age cracking of concrete may influence the long-term durability of a structure. Cracking occurs when the tensile stress in concrete exceeds its tensile strength. Early-age stress development in concrete is influenced by temperature changes, modulus of elasticity, creep or stress relaxation, shrinkage and coefficient of thermal expansion, and the degree of restraint. Three-dimensional finite-element analysis was used to model the early-age stress development of concrete, and a rate-type creep analysis was used herein. Four creep compliance models, including the B3 Model, Modified B3 Model, B3 Model with $R_T$, and B4 Model were incorporated in the finite-element model. Experimental results from restraint of volume change tests with a rigid cracking frame were used to assess the accuracy of the finite-element analysis. The experimental tests included 63 concrete mixtures, which contained varying cementitious materials, mixture proportions, temperature histories, aggregate types, water:cementitious materials ratios, and chemical admixtures. The results showed that the finite-element model provides accurate predictions of measured early-age concrete stresses. The Modified B3 Model provided the most accurate prediction of the measured early-age concrete stresses.

In order to investigate the effects of high pore-water pressure on the mechanical damage and failure behavior of mine shaft–lining concrete, specimens were immersed in a high-water-pressure container (up to 10 MPa) to form a high hydraulic gradient similar to that present in shaft-lining concrete in deep aquifers. The acoustic-wave velocity, strength, elastic modulus, and microcrack propagation were correlated through a mixed orthogonal experimental scheme in which the water pressure, exposure time, and concrete strength, were varied over 16 tests. The experimental results indicate that high pore-water pressure accelerates the damage process of shaft-lining concrete, resulting in increased modulus of elasticity, decreased peak strength with increasing water pressure and exposure time, and greater microcrack propagation in lower-strength-grade concrete (e.g., C60). In addition, most of the specimens failed by shear cracking. A damage evolution equation and constitutive model of shaft-lining concrete under uniaxial compression considering the effects of high pore pressure is established. The model shows good agreement with the experimental results.

It is important to investigate the aging mechanism of asphalt binders. To simulate the aging of the binders in asphalt pavements, three mixture gradations of Stone Mastic Asphalt (SMA)-13, Asphalt Concrete (AC)-13, and Superpave-13 were first aged in an accelerated weathering machine (AWM) for four durations of 0 (as control), 1,000, 2,000, and 3,000 h. Then, aged asphalt binders were recovered from the weathered asphalt mixtures by the Abson method. The nanosized properties of morphology, adhesion, and elastic modulus of the recovered asphalt binders were measured by atomic force microscopy (AFM). Nonlinear models were used to fit the relationships between aging durations and each of the three properties: morphology, adhesion, and modulus of elasticity. The results indicated that (1) as the weathering duration increased, the roughness of morphology decreased while those of both adhesion and elastic modulus increased; (2) nonlinear models fitted well the nanosized properties of morphology, adhesion, and elastic modulus; and (3) SMA-13 performed the best, and Superpave-13 barely outperformed AC-13 with regard to aging resistance.

Asphalt binder draindown is a potential issue related to stone matrix asphalt (SMA) mixtures. One convenient approach for reducing binder drainage is the use of fibers as stabilizing additives. This study assesses the feasibility of incorporating fibers from banana plants into an SMA mixture as a proposed use for residues from banana cultivation. We found the fiber content capable of preventing draindown and subsequently evaluated the influence of fiber length on the mechanical properties of an SMA mixture. Samples were prepared in a Superpave gyratory compactor with four different fiber lengths (5, 10, 15, and 20 mm) at a fixed content (0.3% by weight) and then compared to samples without fibers. Indirect tensile strength, resilient and dynamic modulus, flow number, and fatigue life tests were conducted. Overall, fibers improved the mechanical properties analyzed. These enhancements were more pronounced for the samples with 15- and 20-mm fibers. Thus, a smaller number of longer fibers was more beneficial to the fiber reinforcement of mixtures than a larger number of shorter fibers.

Incorporating waste and recycled materials in concrete has not just a sustainable benefit, but also gives a higher resistance to special circumstances that face concrete structures, such as fire, which causes serious damages to concrete. The present study experimentally investigated the impact of incorporating recycled coarse aggregate (RCA) and two unprocessed waste powder materials on the residual mechanical properties of self-compacting high-performance concrete (SCHPC) after exposure to elevated temperature. Fifteen mixtures of SCHPC (540 specimens) have been produced by replacing the cement mass by up to 30% of each waste fly ash (WFA) and waste perlite powder (WPP) in addition to replacing the coarse natural aggregate (NA) by up to 50% of RCA. Using RCA up to 50% enhanced the residual mechanical properties of SCHPC after exposure to the elevated temperature due to the strong aggregate–mortar contact zone and the similarity of thermal expansion between them. The fire resistance of SCHPC has been enhanced by replacing the cement up to 15% of WPP; meanwhile, WFA did not affect the fire resistance of SCHPC significantly.