Journal of Materials in Civil Engineering

Moisture damage in asphalt pavements can produce rapid failures costing millions of dollars to repair. Surface energy interactions between the asphalt binder and aggregate are known as the fundamental approaches to predicting the mechanisms in the moisture damage process in asphalt mixes. The field of surface energy measurement and its application for moisture damage evaluation is very recent and in the developing stages. The current practice involves two testing equipment for surface energy measurements of asphalt binders and aggregates. The Wilhelmy plate (WP) device is usually employed for surface energy measurements of asphalt binders, and the universal sorption device (USD) is usually used for surface energy measurements of aggregates. This paper presents a sessile drop (SD) device that can be employed for measuring the surface energy components of both binders and aggregates. The SD device has been used for measuring contact angles directly on asphalt binder and aggregate surfaces. The surface energy components of aggregates and binders are calculated using the measured contact angles. The laboratory contact angle measurements on aggregate specimens indicate that while the results from the device are in agreement with the results in the literature, they are not in agreement with the results from the USD. The surface energy components of asphalt binder determined from the measurements of contact angles using the SD device and from the WP measurements are in close agreement.

A generalized theory for the viscoelastic behavior of idealized bituminous mixtures (asphalts) is presented. The mathematical model incorporates strain rate and temperature dependency as well as nonmonotonic loading and unloading with shape recovery. The stiffening effect of the aggregate is included. The model is of phenomenological nature. It can be calibrated using a relatively limited set of experimental parameters, obtainable by uniaxial tests. It is shown that the mathematical model can be represented as a special nonlinear form of the Burgers model. This facilitates the derivation of numerical algorithms for solving the constitutive equations. A numerical scheme is implemented in a user material subroutine (UMAT) in the finite-element analysis (FEA) code ABAQUS. Simulation results are compared with uniaxial and indentation tests on an idealized asphalt mix.

Concrete made with laterite aggregate, a marginal material, is used for fire protection applications. Using mineral admixtures in laterized concrete makes it more sustainable. This paper studies the physical and mechanical properties of laterized concrete with fly ash and ground granulated blast furnace slag (GGBFS) as mineral admixtures after the concrete was exposed to elevated temperatures. Specimens were heated to 200°C, 400°C, and 600°C using an electrical furnace. The rate of increase in the furnace temperature was kept in line with the standard temperature rise—time curve. Specimens were cooled to room temperature through air cooling and water cooling and were tested at ambient temperature. The available equations to predict the compressive and flexural strength of concrete were observed not to apply to laterized concrete, particularly at temperatures higher than 400°C. Hence, lower bound equations were proposed to predict the strength properties of laterized concrete exposed to elevated temperatures. Thus, laterized concrete with mineral admixtures (fly ash and GGBFS) is a promising economical and sustainable material that shows better physical and mechanical properties at elevated temperatures as against conventional concrete and has resistance against the development of thermal cracks up to an exposure temperature of 800°C.

Natural clay usually contains some silt, which is also a fine-grained soil. The proportion of silt in clay varies depending on the source, and the presence of silt in clay affects the reaction between the soil and cement. The purpose of this research was to study the relationship between the proportions of silt and clay in fine-grained soil and the engineering properties of the fine-grained soil after being stabilized with cement. Six types of fine-grained soils were used in this study: a natural clay and five synthetic clays with various proportions of bentonite and kaolinite. The six clays were mixed with silt in the following silt-to-clay proportions: $0:100$, $15:85$, $30:70$, and $45:55$. Cement was added to the synthetic clays in amounts corresponding to 7.5 and 15% of the dry weight of the soil, and the samples were cured for 28 days. Cement was added to the natural clay in amounts corresponding to 7.5, 15, and 20% of the dry weight of the soil, and samples were cured for 7 and 28 days. The results of strength tests of the specimens showed that for both synthetic clay and natural clay, the yield strength increased as the silt content increased. In contrast, the compression index and the recompression index both decreased as the silt content increased. The yield strength of the samples was found to be correlated to the type of fine-grained soil. For the same amount of silt and cement, kaolinite exhibited a higher yield strength and a lower compression index than bentonite. Empirical formulas are proposed in this paper for the relationships between the normalized void ratio and the yield strength, between the compression index and the void ratio at the liquid limit, and between the compression index and the recompression index of cement-treated soft Bangkok clay.

This paper examines effects of a new biobased modifier, “biobinder,” on low-temperature properties of asphalt binder and compares the results with those of conventional modifiers: crumb rubber, Gilsonite, styrene-butadiene-styrene (SBS), and polyphosphoric acid (PPA). Low-temperature characteristics of modified and nonmodified asphalts were studied using experimental and modeling approaches. A three-point bending beam rheometer was used to measure the stress-strain response of each specimen. A theoretical approach was used to determine stiffness and stress release rate; in addition, the Burgers model was implemented to predict the stored and dissipated energy ratio and quantity of derivation of creep compliance in each of modified and nonmodified asphalt specimens. Effects of various modifications were compared based on both the calculated stored and dissipated energy ratio and quantity of derivation of creep compliance. The proposed biobinder is produced from the thermochemical conversion of biomass (including animal waste, switch grass, and woody biomass). Biobinder is then blended with virgin binder to produce biomodified binder (BMB). This paper argues that the improved low-temperature rheological properties in biomodified binder is reflected in the enhancement in energy dissipation ratio and quantity of derivation of creep compliance.

Most current modeling techniques assume that pavement layers are homogeneous. This assumption can be considered one of the main sources of uncertainty in the performance of pavement structures. The main objective of this paper is to present a methodology that includes the uncertainty of material properties as part of the mechanical response of pavement structures. This methodology efficiently combines a stochastic technique with finite-element modeling. The capabilities of the proposed method are illustrated by studying the role of the internal air void distribution of asphalt mixtures on the mechanical performance of flexible pavements. The results from this model corroborate its usefulness to incorporate variability in the mechanical analysis of pavements. Particularly, the methodology was effective in reproducing internal void distributions observed in compacted asphalt layers in the field and its ability to include such distributions in the macromechanical modeling of flexible pavements.

The use of glass fiber–reinforced polymer (GFRP) bars in high-strength concrete (HSC) can solve durability problems associated with conventional steel reinforced concrete (such as premature deterioration due to corrosion) and increase the service life of structures. Experimental investigations were conducted to evaluate the bond characteristics of GFRP bars in HSC. Ninety six pullout specimens that had variable parameters, namely, bar diameter (15.9 mm and 19.1 mm), bar surface condition (sand coated), GFRP bar types (standard low modulus and high modulus), and embedded length (3, 5, 7, and 10 times bar diameter) were tested. The influence of each of these parameters is analyzed to understand interface bond between GFRP bar and HSC. Load-slip characteristics and failure modes of the pullout specimens are described. The performance of various codes in predicting bond stress of both low-modulus and high-modulus GFRP bars embedded in HSC is described based on experimental results.

The technology of asphalt materials and mixtures has evolved in the last four decades in Europe and North America. For the surface layer, there has been an increase in the use of more resistant and durable asphalt mixtures, such as mixtures with discontinuous graduation, e.g., stone matrix asphalt (SMA),which is a gap graded mixture containing 70–80% coarse aggregate of total aggregate mass, 6–7% of binder, 8–12% of filler, and about 0.3–0.5% of fiber. The fibers hold the binder in the mixture at high temperature and prevent drainage during production, transportation, and construction. This research presents a study of the behavior of natural fibers (coconut and cellulose fibers) on SMA mixtures using two different design methods (Marshall and Superpave). The specimens were tested using several common laboratory test procedures: draindown test, indirect tensile strength, resilient modulus, fatigue life, and moisture susceptibility. The draindown test results clearly revealed that coconut fiber can be used in SMA mixtures as a replacement for cellulose fiber to prevent asphalt draindown during production. This study intends to contribute to the development of new technologies suited for the needs of the local paving industry.

This paper presented the investigation on shear behaviors of reinforced ultrahigh toughness cementitious composite (RUHTCC) slender beams with stirrups under center-point loading, where UHTCC possessed the tensile strain-hardening and multiple-cracking characteristics. Eight RUHTCC beams with four different web reinforcement ratios, as well as two reinforced concrete (RC) counterparts, were tested. The experimental results revealed that the use of slight web reinforcement can transform the brittle shear behavior to ductile flexure-shear behavior for RUHTCC beams with about 3.25% longitudinal reinforcement ratio, whereas the flexural failure was obtained when the stirrup ratio was increased up to 0.55% even for the beam with balance reinforcement ratio. Compared to the RUHTCC beam without a stirrup, the ultimate shear strength of RUHTCC beam with a stirrup was slightly enhanced. The shear contribution of UHTCC itself reduced with the increase in the web reinforcement ratio due to the restriction of stirrups. The multiple diagonal cracking and stable crack propagation behavior were presented in RUHTCC beams with and without stirrups, but the number and total opening of diagonal cracks decreased with the increase in stirrup ratio. An empirical equation for predicting the shear resistance of RUHTCC beams with stirrups was proposed based on the shear contribution from both UHTCC and stirrups.

Unbound granular materials (UGM) are extensively used as basecourse materials around the world as they are capable of bearing relatively high traffic loads and are an economical option in comparison to bound materials. The unbound materials performance as basecourse determines the life-cycle costs of a pavement. The extent to which the repeated load triaxial test can predict the performance of unbound granular materials in the laboratory is an important parameter for road designers. Moreover, the performance of the unbound basecourse materials depends upon the moisture conditions when they are being loaded, gradation curve of the material, in situ density, permeability, and the nature of the aggregate fines (clays). There is a need to find the factors that cause the variation in the performance of the materials both in the laboratory and in-field pavement conditions to enable appropriate selection and use. This research utilizes accelerated pavement tests (APT) alongside repeated load triaxial (RLT) tests to test differently graded unbound granular materials at higher moisture contents. The objective of the research is to find the similarities and contrasts in basecourse material in both tests and to find the root causes of variation in the aggregate performance. If results of the RLT test can truly represent the results from full-scale APTs for basecourse materials, then the pavement materials industry can use the much lower costing RLT tests with confidence knowing it is representative of performance tests from APTs. The accelerated tests are performed on test pavements at the Canterbury Accelerated Pavement Testing Indoor Facility (CAPTIF) with the introduction of surface water, which replicates typical rainfall events. An increase in moisture in the basecourse layers is observed during the APTs due to entry of surface water through the surface seal, which allowed the performance of the basecourse material at higher moisture contents to be assessed. The RLT tests were conducted in parallel with the same basecourse materials at higher moisture conditions. The relative performance ranking of APTs and RLT tests is found to be the same for some materials; however, it differs in some cases. The similarities and differences in the rankings from both procedures are highlighted, and the causes of these similarities and differences are inferred and discussed.

A value of tensile strength of cement-based materials is required for the design of pavements, for the analysis of concrete dams to prevent thermal cracking and sometimes for the design of prestressed beams. Cementitious materials exhibit a significant variability in their tensile strength, depending on the test method used. The three common test methods are direct tension, three-point bending, and four-point bending, and it is commonly found that bending tests yield higher strengths than direct tension tests. During this investigation, tests were carried out on cement mortar and concrete for each type of test. A two-parameter Weibull model was found to fit each individual set of data well. For both cement mortar and concrete, the Weibull moduli calculated for the test methods were approximately the same. The Weibull modulus is used to relate the values of strength obtained with different test methods, using the Weibull effective volume concept, the predicted results are in remarkably good agreement with the experimental results.

The newly developed Mechanistic-Empirical Pavement Design Guide (MEPDG) uses the dynamic modulus master curve to account for the temperature and frequency dependent behavior of asphalt concrete. However, the master curve used in the MEPDG is constructed using dynamic moduli measured in uniaxial testing and the effect of confinement on the mechanical properties of asphalt concrete is disregarded. This study implemented a model of triaxial dynamic modulus master curve in finite-element (FE) modeling of asphalt pavements. The dynamic modulus distribution in asphalt layers due to the contribution of confinement was evaluated for various scenarios. The results show that when the effect of confinement is considered the dynamic modulus can be more than two times the uniaxial value at the same temperature and frequency. The effect of confinement on dynamic modulus is more evident at high temperatures and low frequencies. Various pavement responses were computed using the developed FE model and compared to those obtained using the corresponding uniaxial dynamic modulus. For the pavements analyzed in this study, the confinement has the most pronounced effect on the permanent deformation of asphalt layers. The compressive strain in asphalt layers can be reduced to about half of the value obtained using the uniaxial dynamic modulus.

In order to predict compressive strength of geopolymers prepared from alumina-silica natural products, based on the effect of ${\mathrm{Al}}_2{\mathrm{O}}_3/{\mathrm{SiO}}_2$, ${\mathrm{Na}}_2\mathrm{O}/{\mathrm{Al}}_2{\mathrm{O}}_3$, ${\mathrm{Na}}_2\mathrm{O}/{\mathrm{H}}_2\mathrm{O}$, and $\mathrm{Na}/[\mathrm{Na}+\mathrm{K}]$, more than 50 pieces of data were gathered from the literature. The data was utilized to train and test a multilayer artificial neural network (ANN). Therefore a multilayer feedforward network was designed with chemical compositions of alumina silicate and alkali activators as inputs and compressive strength as output. In this study, a feedforward network with various numbers of hidden layers and neurons were tested to select the optimum network architecture. The developed three-layer neural network simulator model used the feedforward back propagation architecture, demonstrated its ability in training the given input/output patterns. The cross-validation data was used to show the validity and high prediction accuracy of the network. This leads to the optimum chemical composition and the best paste can be made from activated alumina-silica natural products using alkaline hydroxide, and alkaline silicate. The research results are in agreement with mechanism of geopolymerization.

Long-term corrosion tests were performed on prestressed T-girders measuring 4.98 m (16 ft, 4 in.). The test program was composed of four specimens, including one control. The specimens were subjected to wet/dry cycles using 3% NaCl solution to accelerate corrosion. Two of the specimens were precracked prior to conditioning to examine the effect of crack presence and/or width. The specimens were continuously monitored using acoustic emission (AE). Half-cell potential (HCP) measurements and linear polarization resistance (LPR) were performed daily to serve as a benchmark for corrosion detection. Acoustic emission can detect the onset of corrosion comparable in time to conventional electrochemical methods. Furthermore, AE intensity analysis has the ability to distinguish between different levels of corrosion. The specimens were load-tested to measure the residual capacity, which can give an indication of AE’s ability to detect corrosion damage before it affects the strength of prestressed structures.

Extensive amounts of natural quarry aggregates are currently being used in road and pavement applications. The use of construction and demolition (C&D) materials such as recycled concrete aggregate (RCA), crushed brick (CB), and reclaimed asphalt pavement (RAP) as an alternative to quarry aggregates has generated interest in recent years, particularly as a pavement base or subbase material. However, the resilient moduli responses and performance of these C&D materials reinforced with geogrids under repeated loads have yet to be established. This research investigates the resilient moduli ($M_R$) and permanent deformation characteristics of C&D materials reinforced with biaxial and triaxial geogrids with the use of repeated load triaxial (RLT) equipment. The effects of varying deviatoric stress on the resilient modulus of unreinforced and geogrid-reinforced C&D materials were also investigated. Regression analyses of resilient modulus test results were performed using the two- and three-parameter models. The $M_R$ properties of the geogrid-reinforced RCA and CB were found to be higher than that of the respective unreinforced material. The $M_R$ value of RCA+biaxial increased by 24% and of RCA+triaxial increased by 34% when compared with unreinforced RCA. The permanent deformation value obtained from RCA+biaxial decreased by 29% and of RCA+triaxial decreased by 36% when compared with unreinforced RCA. The $M_R$ value of CB+biaxial increased by 16% and of CB+triaxial increased by 55% when compared with unreinforced CB. The permanent deformation value decreased by 29 and 37% for CB+biaxial and CB+triaxial, respectively, when compared with unreinforced CB material. The incorporation of geogrids had significant effects on the resilient modulus and permanent deformation characteristics of C&D materials. The three-parameter resilient moduli model was found to provide a good fit for the geogrid-reinforced C&D materials.

This paper presents the experimental results of a study on the durability properties of clinoptilolite blended cement mortars. In the study, clinoptilolite was used at 0, 5, 10, 15, 20, and 30% replacement by weight of cement while sand and water quantities were kept constant. Fire resistance, abrasion resistance, and shrinkage of the mortars were examined. The results showed that the replacement of cement with clinoptilolite in mortar improved the fire resistance of mortar and that water cooling resulted in higher strength losses than air cooling. Also, the abrasion resistance of mortars increased with an increase in the content of clinoptilolite. After the abrasion tests with a full 352 cycles, although the abrasion loss of control mortar was 2.83%, the abrasion losses of the mortars containing clinoptilolite ranged from 2.12 to 2.81% and the lowest abrasion loss was obtained from the mortars including 30% clinoptilolite. However, the incorporation of clinoptilolite in the mixture caused some increase in the shrinkage values of mortar; at the end of 90 days, the shrinkage value of the mortar specimen with 30% clinoptilolite was approximately 0.14%, whereas that of control mortar was 0.10%.

The discrete-element method (DEM) provides more realistic results compared with those of continuum analysis for unbound construction materials such as railroad ballast. This paper introduces a digital-image aided particle-shape generation method for DEM to consider the shape effects of aggregate particles on assembly behavior. The BLOKS3D DEM program is used in this research with the capability of representing angular aggregates as discrete elements with user-defined particle morphological properties from imaging-based shape indices. A three-dimensional (3D) image analysis approach is available to construct discrete elements with shapes close to the morphological properties of actual aggregate shapes. A large-sized shear box is then used in direct-shear tests to validate this image-aided particle-shape generation DEM. The purpose of validation is to match the laboratory test results with the DEM simulation results by using one single set of model parameters. To that end, the sensitivity of DEM model parameters are investigated by conducting DEM shear-box simulations using different combinations of model parameters realistically chosen on the basis of previous research studies. The validation process is finally accomplished by statistically demonstrating that the DEM shear-box simulation results using one set of parameters can predict the laboratory shear-box test results reasonably well under various normal stress levels.

The reduction of hot asphalt mixtures for the usage and development of sustainable supplementary cold asphalt mixtures (CAMs) for the construction of road and highway surface layers is a major issue for researchers around the world. This reduction will benefit environmental impact, cost effectiveness, and energy savings. Furthermore, because CAMs comprise a remarkable portion of industrial waste (the disposal of which consumes virgin lands), they are attractive to road and highway authorities. The primary aim of this investigation is to develop new cold rolled asphalt (CRA) with the same gradation as hot rolled asphalt (HRA), which is usually used as a surface course in the U.K., and to improve its mechanical properties and durability by using waste and by-product materials as mineral fillers and additives. Waste fly ash (WFA) was used as a replacement for conventional mineral filler and a by-product silica fume (SF) was used as an additive to enhance the mechanical properties and durability of CRA containing WFA. The experimental results have shown that WFA significantly improves the mechanical properties and durability of CRA. On the other hand, the addition of SF enhances the initial strength, long-term strength, and durability. The new CRA mixture has mechanical properties and durability comparable to those of conventional HRA, which demonstrates the feasibility of the use of CRA in heavy road construction.

Present research aims to carry out field and laboratory tests in a top cement improved residual soil layer. Regarding laboratory tests, the isolated influence of parameters such as cement percentage, porosity and water content will be studied after unconfined compression testing. Test results showed that the unconfined compressive strength ($q_u$) increased along with the cement percentage and with the reduction of the porosity of the compacted mixture. It was still possible to verify that the water content had reduced influence on the unconfined compressive strength, which was basically dependent of porosity and amount of cement. The research also studied the behavior of plate load tests with different diameters (D) bearing on a treated layered system with different thickness (H) considering 5% of portland cement (determined after analysis of unconfined compression test results). Triaxial tests were also carried out in specimens retrieved from the cement treated layer, cone penetration tests (CPT) were done in the cement improved layer and the outcome shows a substantial increase in tip cone resistance comparatively with the natural soil. A finite-element analysis of the plate load tests was carried out using the elastic-perfectly plastic model with Drucker-Prager failure criterion that proved suitable for the simulation. After processing results of plate load tests bearing on the cemented layered system, it was verified that the applied pressure versus settlement to diameter ratio correlation is controlled by the H/D relation, in which this factor increase takes to a stiffer and stronger response.

The viscoelastic behavior of model sandy soils in the form of silica particle compacts under dynamic compression (0.2–10.0 Hz) is reported. The solid content ranges from 24 to 28% by volume, as controlled by compaction. Both viscous and elastic characters are largely governed by the solid part of the compact. The elastic character stems from the stiffness of the silica, while the viscous character stems from the interparticle movement. The elastic character of the solid part (the storage modulus and solid content) is essentially independent of the degree of compaction, indicating validity of the rule of mixtures. The viscous character of the solid part (the loss tangent and solid content) decreases with increasing degree of compaction, indicating decreasing ease of interparticle movement as the degree of compaction increases. The loss modulus and solid content is essentially independent of the degree of compaction. All quantities decrease with increasing frequency. A low degree of compaction is recommended for fast decay of the vibration amplitude; no particular degree of compaction is recommended for mechanical energy dissipation.

This paper reports the evaluation of fatigue response of asphalt mixtures produced with different additives, namely cellulose and synthetic fibers, amorphous polyolefin, and ethyl vinyl acetate (EVA), in comparison with conventional asphalt mixtures. The additive content was also analyzed by producing asphalt mixtures with 3, 6, and 9% of additive. Fatigue testing was performed with an indirect tensile test apparatus under controlled stress mode of loading. A comparative analysis of the fatigue resistance was carried out using the different methods. Fatigue life was defined using the classical approach in which the number of cycles reaches the double of initial deformation. It was also defined in terms of different methods based on dissipated energy: total dissipated energy, ratio of dissipated energy change, and plateau value. This paper offers an analysis of different methods of evaluating the indirect tensile fatigue test. The testing clearly shows that polymer modification may extend the fatigue life, and that energetic methods can be effectively applied to data from indirect tensile fatigue tests.