Journal of Materials in Civil Engineering

Most studies involving cement-stabilized soil blocks (CSSB) concern material properties, such as the characteristics of erosion and strength and how the composition of the block affects these properties. Moreover, research has been conducted on the performance of various mortars, investigating their material properties and the tensile bond strength between CSSB units and mortar. In contrast, very little is currently known about CSSB masonry structural behavior. Because structural design codes of traditional masonry buildings were well developed over the past century, many of the same principles may be applicable to CSSB masonry buildings. This paper details the topic of flexural behavior of CSSB masonry walls and whether the Masonry Standards Joint Committee (MSJC) code can be applied to this material for improved safety of such buildings.

A comprehensive study was conducted to evaluate the impact of liquid and lime additives on the pavement performance of asphalt mixtures from five different sources around the United States. Three types of mixtures were evaluated from each source: untreated, liquid-treated, and lime-treated. The measured properties of the 15 mixtures included the dynamic modulus and their resistance to rutting and fatigue at the undamaged and moisture-damaged conditions. The measured performance properties of the mixtures were then used to conduct 20 years’ worth of structural designs for actual projects selected from the five sources of mixtures. For each project, a total of three structural designs were established using the Mechanistic-Empirical Pavement Design Guide by changing the type of mix used in the hot mix asphalt (HMA) layer. The percent cost savings or additional costs were estimated relative to the cost of the HMA pavement with the untreated HMA mixtures. Overall, the use of lime additives in HMA mixtures consistently resulted in significant savings that was sometimes as high as 45%. The use of liquid antistrip additives in HMA mixtures resulted in savings between 13 and 32%, or an additional cost, in some cases as high as 50%. The additional cost for the liquid-treated mixes was observed for mixtures that were not considered to be moisture sensitive, as measured by retained tensile strength ratio.

In Singapore, the applications of recycled concrete aggregate (RCA) are limited to nonstructural concrete, road construction, and backfilling. To realize the beneficial use of RCA, an in-depth study was conducted to evaluate its use in structural concrete. This paper reports the test results of a study that is part of extensive research intended to evaluate the properties of RCA concrete produced by a proposed rational approach in concrete mix design. The key parameters studied include compressive strength, elastic modulus, and drying shrinkage. The results showed that the RCA concrete can be designed to achieve comparable compressive strength and elastic modulus, relative to the corresponding properties of concrete containing natural coarse aggregate (NCA). RCA concrete tends to exhibit higher drying shrinkage strains relative to NCA concrete, but the values are within the recommended limits.

This paper describes an application of the fast multipole boundary element method (FMBEM) in simulating the viscoelastic behavior of asphalt concrete (AC). FMBEM has some merits including easy meshing of complicated geometries, accuracy in solving singular fields, high calculation efficiency, and low data storage requirements. These merits lead to many applications in multiple time-step and multi-inclusion problems, such as prediction of AC creep behavior. In this paper, a fast multipole formulation and an algorithm for two-dimensional linear viscoelastic problems are introduced first. To consider the bonding between the asphalt matrix and aggregates, a viscoelastic interface model is used to simulate the interfacial imperfection. A numerical model of asphalt concrete is then constructed based on image processing techniques, and the model is capable of taking into account the effects of the size and content of the air voids. The creep compliance of AC is predicted by the developed FMBEM arithmetic and subsequently compared with the experimental results. It has been shown that the developed method can describe and simulate the correct creep evolutionary trend of AC.

This research study was performed to examine the shakedown behavior of geogrid-reinforced unbound granular materials and evaluate the factors that affect the shakedown stress limits. To achieve this objective, the study was performed through conducting repeated load triaxial (RLT) tests on both unreinforced and geogrid-reinforced unbound granular specimens. A multistage RLT test, in which only one sample is needed to determine the shakedown stress limits, was selected in preference to a single-stage RLT test, in which several tests on multiple samples are required. Five geogrids of different tensile modulus and different aperture geometries (three rectangular or biaxial and two triangular or triaxial) were used. The test results clearly demonstrated the potential benefits of placing the geogrid within the unbound granular base specimen in terms of permanent deformation reduction. The benefits of the geogrid are more prevalent at higher stress levels and for higher tensile modulus geogrids. The inclusion of the geogrid has more of an effect on delaying the occurrence of range B shakedown behavior (i.e., increasing the plastic shakedown limit) than that of range C shakedown behavior (i.e., increasing the plastic creep limit) for specimens prepared at the optimum and the dry side of optimum. For specimens prepared at the wet side of optimum, geogrids have a negligible effect on delaying the occurrence of range B shakedown behavior (i.e., increasing the plastic shakedown limit) but have a significant effect on delaying the occurrence of range C shakedown behavior (i.e., increasing the plastic creep limit). Of the five geogrids used, the triaxial geogrid TX2, with triangular geometry and the highest tensile modulus, performed consistently better than the other four geogrids.

The evolution of carbonation front progress, crack spatial distribution, and pore structure parameters of hardened cement paste have been monitored in situ by three-dimensional (3D) X-ray computed tomography (XCT) at different accelerated carbonation ages of 0, 3, 7, 14, and 28 days, respectively. The gray-value histograms of cement paste are a function of carbonation time, and the carbonation degrees at different times can be estimated by the volume fractions of uncarbonated and carbonated parts. Many cracks generate along the carbonation direction because of carbonation shrinkage. With the extension of the carbonation time, the volume and surface of cracks become larger. The porosity markedly decreases when pore volume is between 0.01 and $0.1{\mathrm{mm}}^3$ as the carbonation time increases.

The effect of basalt fiber on asphalt binder and mastic at low temperatures is investigated in this study. Basalt fibers are dispersed into the asphalt binder and mastic specimens to prepare the fiber-reinforced binding materials. The fiber-reinforced specimens are tested using the direct tension test and a newly developed fatigue test procedure, which is able to directly apply cyclic tensile loading to the asphalt binder and mastic specimens. The reinforcement effects of basalt fiber to the fatigue resistance of asphalt binding materials are evaluated. The direct tension test results show that with an appropriate content, the tensile strength of the asphalt binder is improved with the use of basalt fiber. The basalt fiber also restrains the axial strain and increases the stiffness of both the asphalt binder and mastic specimens. The fatigue test results indicate that the fatigue life of both asphalt binder and mastic specimens is significantly improved by the basalt fibers. The effect of basalt fibers is also analyzed using numerical simulations of direct tension and fatigue tests based on the finite-element method. The internal structure of the fiber-reinforced mastic is considered with the assistance of X-ray tomography technology. The fiber-reinforced mastic model is a heterogeneous composite in which the asphalt binder, fillers, and basalt fibers are treated as different materials. The axial stress and strain of the model are analyzed under unidirectional tensile loading and cyclic tensile loading. The results show that the fiber added between fillers releases the stress concentration of the critical area and diminishes the fatigue damage caused by cyclic loading.

The ability of titanium dioxide (${\mathrm{TiO}}_2$) photocatalytic nanoparticles to trap and decompose organic and inorganic air pollutants render them a promising technology as a pavement coating to mitigate the harmful effects of vehicle emissions. This technology may revolutionize construction and production practices of hot-mix asphalt by introducing a new class of mixtures with superior environmental performance. The objective of this study was to assess the benefits of incorporating ${\mathrm{TiO}}_2$ into asphalt pavements. To achieve this objective, the photocatalytic effectiveness and durability of a water-based spray coating of ${\mathrm{TiO}}_2$ was evaluated in the laboratory. This study also presents the field performance of the country’s first air-purifying photocatalytic asphalt pavement, located on the campus of Louisiana State University. Laboratory evaluation showed that ${\mathrm{TiO}}_2$ was effective in removing ${\mathrm{NO}}_x$ and ${\mathrm{SO}}_2$ pollutants from the air stream, with an efficiency ranging from 31–55% for ${\mathrm{NO}}_x$ pollutants and 4–20% for ${\mathrm{SO}}_2$ pollutants. The maximum ${\mathrm{NO}}_x$ and ${\mathrm{SO}}_2$ removal efficiencies were achieved at an application rate of $0.05\mathrm{L}/{\mathrm{m}}^2$. The efficiency of ${\mathrm{NO}}_x$ reduction is affected by the flow rate of the pollutant, relative humidity, and ultraviolet (UV) light intensity. In the field, ${\mathrm{NO}}_x$ concentrations were monitored for both the coated and uncoated sections to directly measure photocatalytic degradation. Furthermore, nitrates were collected from the coated and uncoated areas for evidence of photocatalytic ${\mathrm{NO}}_x$ reduction. Results from both approaches show evidence of photocatalytic ${\mathrm{NO}}_x$ reduction. Further field evaluation is needed to determine the durability of the surface coating.

Pyrites and pyrrhotites are the most abundant minerals of the iron sulfide group in nature and may be found in the aggregates used to produce concrete. In the presence of water and oxygen, such compounds generate expansive reactions that may have severe structural damages. This is especially critical in concrete dams, given the large volume of material used and the restrictions in movement imposed by the surroundings. In these cases, the definition of adequate rehabilitation programs depends on the prediction of the expansive reaction evolution and the future behavior of the structure. Although models that describe solid particle–gas reactions may be used with this purpose, none were specifically developed to simulate this phenomenon in dams. This paper introduces a new kinetic model based on the unreacted-core model for pyrrhotite oxidation. The comparison of the results obtained with this new model and with the direct application of the unreacted-core model show significant differences. Following an extensive parametric study, a simplified constitutive equation is proposed to estimate the pyrrhotite oxidation kinetics in concrete dams. The estimations performed with this constitutive equation agree with the experimental data obtained in the tests of different particle sizes.

The objective of this study was to evaluate the moisture susceptibility, rutting, and fatigue resistance of laboratory-made half warm mix asphalt (HWMA) mixtures containing moist aggregates and recycled materials such as manufactured roofing shingles and reclaimed asphalt pavement (RAP). The test properties evaluated in this study included weight loss (%), indirect tensile strength (ITS), tensile strength ratio (TSR), wet flow, wet toughness, percent toughness loss, rut depth of dry and wet conditioned specimens, rut index, and beam fatigue life. The experimental design in this study included the use of foaming technology and three hydrated lime contents (0, 1, and 2% by weight of aggregate), three aggregate sources (designated as A, B, and C), three fractioned RAP sources from the same aggregate sources, and one PG 64-22 binder. A total of 27 mixtures was designed, and a total of 120 ITS samples, 162 asphalt pavement analyzer (APA) samples, and 36 fatigue beams were tested in this study. Results indicated that the addition of recycled materials such as RAP or roofing shingles can be effectively employed in HWMA mixtures, which did not reduce wet ITS and TSR values, although the compaction temperature was only 85°C. The influence of the moist aggregate used in HWMA on rut depth can be neglected and even results in a better rut resistance when incorporating recycled materials. Stiffness values of mixtures with recycled materials were generally dependent on the aggregate type. Based on the statistical analysis for the selected aggregates, no significant difference in fatigue life was observed for mixtures with recycled materials and control mixtures.

Recently, a shape memory polymer-based self-healing syntactic foam was proposed and tested as a sealant for expansion joints. The key for success is to train the foam by using a two-dimensional (2D) stress condition (compression in the horizontal or traffic direction and tension in the vertical direction) at a temperature above the glass transition temperature ($T_g$). However, for practical applications, programming a full-size slab of sealant with a 2D stress condition and under temperature control is not a trivial task. This study demonstrated that the programming with a one-stage 2D stress condition can be replaced by a sequential two-stage one-dimensional (1D) stress condition. To further simplify the programming process, 1D tension programming was conducted at a temperature above the $T_g$, followed by 1D compression programming at a temperature below the $T_g$ (cold compression). The test results show that the hybrid programming leads to similar shape memory behavior as long as the prestrain level in the two programing is similar or the prestrain absolutely predominates in one direction. Otherwise, the sealant exhibits a two-stage recovery: it recovers first in the direction with larger prestrain, followed by the direction with smaller presrtain, regardless of the programming sequence.

The objective of this study was to evaluate the feasibility of using warm mix asphalt (WMA) technologies to produce quality open graded friction course (OGFC) mixtures. This evaluation was based on the comparison of Evotherm WMA and foamed WMA mixes with traditional hot mix asphalt (HMA) OGFC using three primary criteria: draindown, permeability, and abrasion resistance. The results of the study indicated that fibers could be removed from OGFC mixtures when using the WMA technologies included in this study. This conclusion was based on the performance evaluation of the mixtures, which showed that when the fibers were removed, the permeability of the mix almost doubled. Additionally, the WMA mixtures without fibers met typical aged abrasion loss requirements and the foamed WMA mixtures without fibers performed similarly with regard to aged abrasion resistance to the HMA mixture with fibers, whereas the HMA mix without fibers showed lower resistance to abrasion than the WMA mixtures. The enhanced performance of the mixtures can be attributed to the increased binder film thickness of the WMA mixtures compared to the HMA mixtures without fibers.

Fly ash changes the microstructure of paste and can increase concrete durability. Calcium hydrated lime was added to concrete with 50% of the cement, by weight, substituted with fly ash, with the intent of replacing some of the calcium hydroxide consumed by the pozzolanic activity. Three proportions of mixes were studied: concrete with high early strength cement (HESC), concrete with 50% HESC and 50% fly ash, and concrete with 50% HESC, 50% fly ash and an additional 20% of hydrated lime. They were then tested according to ASTM C1202, but with the application of a voltage of 30 V during 35 h. Results revealed that concretes containing fly ash and hydrated lime presented a lower accumulated charge density and coefficient of chloride diffusion than the HESC concrete used as a reference.

Stone-matrix asphalt (SMA) is a type of hot-mix asphalt that can reduce the cost of maintenance and rehabilitation of pavements through decreasing the amount of permanent deformation during its service life. In addition, warm-mix asphalt (WMA) has been recently used to reduce the mixing and compaction temperatures of asphalt concrete and potentially decrease the initial cost of asphalt mixtures, especially in countries for which energy costs are high. The primary purpose of this research is to combine these technologies to produce more efficient asphalt mixtures. To this end, two different additives [cellulose fiber and styrene-butadiene-styrene (SBS)] were used to construct typical SMA mixtures, and a type of WMA additive (wax) was used to prepare warm SMA specimens. Modified binders were subjected to binder properties tests. Mixture performance tests, including the Marshall, indirect tensile strength, moisture susceptibility, dynamic creep, and resilient modulus tests were also performed to evaluate the performance properties of different types of SMA mixtures. A mechanistic-empirical design procedure was conducted to investigate the benefit of modification. The results indicate that Fischer-Tropsch (FT) wax is capable of enhancing the base binder properties. Although different percents of wax could reduce the amount of binder drain down, this reduction was not adequate. Consequently, the use of an additional additive may be necessary. The effect of wax on the performance properties of SMA mixtures was also insignificant, although there were some improvements. Moreover, by comparing the test results, good correlations were obtained between various performance properties of SMA mixtures, all of which were significant. The use of cellulose fiber, SBS, and FT wax would respectively increase the service life of the pavement 1.08, 1.243, and 1.154 times more than the corresponding unmodified mixtures.