Journal of Materials in Civil Engineering

The ability to accurately predict pavement temperature variation with time and depth is critical to calculating binder oxidation in pavements, understanding asphalt material behavior, and predicting pavement performance. In this work, an improved one-dimensional model, coupled with methods to obtain model-required climate data from available databases and optimization of site-specific pavement parameters was developed to calculate hourly pavement temperatures nationwide. Hourly solar radiation and daily average wind speed were obtained from existing databases. Hourly air temperatures were interpolated using a daily air temperature pattern developed from time-series analysis and commonly recorded daily maximum and minimum air temperatures. Parameter estimation identified three critical site-specific pavement parameters: the albedo, the difference between the emissivity and absorption coefficient, and the absorption coefficient. The values of these parameters, optimized at 29 pavement sites nationwide based on the average hourly absolute error objective function, appear to correlate with climatic patterns, suggesting that these parameters be interpolated based on climate. The temperature model, proposed data sources, and site-specific pavement parameters provided calculations that agreed well with experimental measurements.

The effectiveness of externally bonded fiber-reinforced polymer (FRP) laminates for strengthening existing reinforced concrete (RC) structures is strictly related to the bond of the FRP reinforcement to the concrete substrate. Although numerous experimental studies have investigated this bond, experimental data concerning cyclic tests on both FRP sheets and plates applied on concrete specimens are still lacking. Thus, a series of single shear tests (SSTs) under both monotonic and cyclic actions, without inversion of sign, were performed on concrete prismatic specimens reinforced with carbon FRP (CFRP) sheets or plates. To evaluate and compare the influence of cyclic external actions on the bonding behavior of sheets and plate reinforcements, the results provided by monotonic and cyclic tests are reported and discussed in this paper. In particular, force-displacement relationships, axial strains, and shear stresses recorded along the FRP reinforcement are reported; the influence of the load path on the FRP debonding behavior is also examined.

In this study, the effects of initial temperature, catalyst content, and activator content on the gelling time and maximum curing temperature of two polymeric grouts were investigated. Because the grouts are used in various environmental conditions, the grouts were investigated at three different initial temperatures (4.4, 15.7, and 26.7°C, or 40, 60, and 80°F). The catalyst and activator contents varied from 0.5% to 3% of the total weight of grout mix. Gelling times for the polymer grouts were measured, and the curing temperatures for the mixtures were monitored during and after the gelling process. The gelling time reduced with increased catalyst and activator contents and increased initial temperature for both the polymer grouts. One grout exhibited shorter gelling time and lower temperature rise during the gelling process than the other grout. Both artificial neural network (ANN) and nonlinear relationship (NLR) models were used to predict the observed grout behaviors. For each grout, a total of 48 tests were performed and data from 32 tests ($2/3$ of the total data) were used for training and calibrating the two models. The data from the 16 remaining tests were used to verify the model predictions. Various ANN architectures with numbers of hidden layers and neurons were studied to determine the optimum network architecture for the current study. The optimum network required two hidden layers with four nodes in each layer. The NLR model and the ANN model predicted the gelling time and maximum curing temperature rises very well, and the coefficient of determination ($R^2$) was in the range of 0.91 to 0.97.

The results of an experimental program to evaluate the properties of a novel building material—oil palm waste-cement composite (OPWCC) are presented in this paper. Cement paste samples containing 0, 20, 40, 60, and 80% pulverized palm kernel shell (PKS) as a replacement for cement, and 2, 4, 6, 8, and 10% volume fractions of palm nut fiber (PNF) were evaluated for flexural strength, impact strength, sound absorption coefficient, thermal diffusion coefficient, and percentage water absorption. The results show that the impact strength, acoustic absorption, and thermal diffusivity performances of the composite were improved with the addition of PKS and PNF. On the other hand, the flexural strength and the water absorption characteristics of the composite deteriorated with the addition of PKS and PNF. However, for some of the investigated composites, these later-mentioned characteristics were within values specified by ASTM for sheathing board.

This paper presents the results of a research project whose goal was to measure the surface strength of concretes cured under different environments by using the newly developed twist-off test. A circular steel disk was glued to the surface of the concrete with an epoxy resin. The force required to twist this disk off the surface, together with an attached layer of concrete, was measured by using an ordinary torque wrench. The different curing regimes had specimens immersed in drinking water, covered with a wet hessian and polythene sheet, kept in a dry laboratory, left in open air, steam cured, and coated with a curing agent. Eight different concrete mixtures with a 28-day design compressive strength of 10–75 MPa were used. The effects of different water-cement and aggregate-cement ratios were studied for all mixes cured under the six different environments. The coefficients of variation associated with surface-strength measurement were also studied for different curing regimes.

Autogenous curing behavior of cold-bonded fly-ash-aggregate concrete for a range of cement and aggregate contents is studied by subjecting concrete to three different curing regimes, viz, mist curing, sealed condition and air curing. The moisture movement from the aggregate to concrete at various ages is estimated and correlated to the paste-aggregate proximity. The degree of hydration is evaluated through nonevaporable water content. Thermal gravimetric analysis (TGA) has been employed to identify hydration products with age of concrete. The results suggest that the degree of hydration and strength of cold-bonded aggregate concrete are almost insensitive to curing conditions. The autogenous curing of cold-bonded aggregate concrete could be effectively utilized with no variation in compressive strength or porosity as compared with mist curing, if it is properly covered to minimize the evaporation loss.

Taking the heterogeneity character of concrete into account, this paper presents an equivalent probabilistic model for failure study of concrete in which the heterogeneity of concrete is considered by assuming that the material properties conform to the Weibull distribution law and by using mesoscale mesh of finite elements. The study is divided into three parts. In the first part, a spatial correlation length factor is developed into the Weibull distribution formula so that the spatial correlation of local continuity of material properties can be considered. The second part presents a series of numerical analyses for investigating the size effect of self-compacting concrete (SCC) based on the equivalent probabilistic model, and a comparison is made between the simulation results and compression test measurements for illustrating the size effect on uniaxial compression strength and failure pattern of the SCC concerned. It is shown that the numerical model can provide reasonable predictions in the analysis of the size effect of SCC. In the final part, as an engineering application of the presented model, the damage and fracture behavior of the Koyna gravity dam during the 1967 earthquake are analyzed. Influences of concrete parameters on the crack pattern and failure modes of the dam prototype during the event are discussed.

When recycled aggregate is used for concrete manufacture, in many cases these aggregates are accompanied by a recycled sand content. This research focuses on concretes prepared with recycled sand content. First, the research examined the effects of recycled sand content on the characteristics of mortar—density and compressive and flexural strength—by using recycled sand contents of 0, 5, 10, 15, 20, and 50%. Subsequently, the effect on the characteristics of recycled concretes made with a water/cement ratio of 0.50, when part of the recycled aggregate was replaced with recycled sand, was studied. The results obtained on mortars indicate that the use of up to 20% recycled sand caused a drop in the compressive and flexural strength. In concretes, the use of up to 100% recycled aggregate has no appreciable effect on compressive strength but does lower the modulus of elasticity, E, as the recycled aggregate content increases. If the recycled aggregate used in the manufacture of concretes contains up to 10% recycled sand, this sand has no appreciable effect on the compressive strength of the concrete, nor on its modulus of elasticity E.

Nanotechnology has the potential to create many new materials and devices with wide-ranging purposes. Nano-sized particles have been used in numerous applications to improve the properties of various materials. The utilization of nanotechnology in civil engineering is expected to increase and may become an attractive alternative for asphalt binder modification. The objective of this study was to investigate and evaluate the rheological properties of binders containing various percentages of carbon nanoparticles after a short-term aging process. The experimental design for this study included five binder sources (three grades including PG 64-22, PG 64-16, and PG 52-28), three nano percentages (0.5, 1.0, and 1.5% by weight of the virgin binder), and control binders. The rheological characteristics of the rolling thin film oven (RTFO) binders, including failure temperature, performance grade, creep and creep recovery, viscous flow, and frequency and amplitude sweep, were tested. The results of the experiments indicated that the addition of nanoparticles was helpful in increasing the failure temperature, complex modulus, and elastic modulus values and in improving rutting resistance of the RTFO binder. The phase angle of the binders generally decreased with an increase in nano content and RTFO aging procedure. In addition, statistical analysis indicated that the asphalt binder source plays a key role in determining the rheological properties because of significant evaluations.

The practice of treating soil with fly ash and lime is an attractive technique when the project requires improvement of the local soil for the construction of stabilized bases under pavements, as a support layer for shallow foundations, to strengthen slopes in slope stability problems, and to prevent sand liquefaction. Currently, efforts are being made to develop dosage methodologies for improved soils based on a rational criterion as it exists in concrete technology, in which the water-cement ratio plays a fundamental role in the assessment of the target strength. This study evaluates the strength controlling parameters of a sandy soil treated with fly ash and lime and shows that the voids-lime ($\eta /L_v$) ratio (corresponding to porosity divided by the volumetric lime content) plays a fundamental role in the assessment of the target strength. The controlling parameters evaluated were the amount of fly ash, quantity of lime, porosity, and voids-lime ratio. A number of unconfined compression tests and suction measurements were carried out in the present work. The results show that the unconfined compressive strength (UCS) increased linearly with the amount of lime for soil–fly ash–lime mixtures. A power function adapts better to the relation UCS-porosity ($\eta$) for soil–fly ash–lime mixtures. The ratio $\eta /L_v$, in which $L_v$ is adjusted by an exponent (in this case 0.12 for all soil–fly ash–lime mixtures studied), is shown to be a good parameter in the evaluation of the UCS of the soil studied (UCS varies nonlinearly with $\eta /L_v$ in the case of fly ash–lime addition). Finally, it was found that a unique correlation controls the strength of the compacted soil–fly ash–lime mixtures studied; consequently, using this relationship an engineer (considering the specifics of each case such as price, availability, and cost of transportation of each material, among others) can choose the amount of lime, the quantity of fly ash, and the compaction effort appropriate to provide a mixture that meets the strength required by a project at the optimum cost.

Time domain reflectometry (TDR) has been evaluated as a tool for the measurement of the moisture content of masonry materials. To this aim, the relationship between relative dielectric permittivity, measured by TDR, and volumetric water content, measured gravimetrically, has been experimentally determined over samples of three cement mortars and a clay brick. The obtained experimental points do not fit the calibration curves available in literature for other porous materials, such as soils and rocks. Instead, specific calibration relationships have been determined. The obtained results show that in all cases dielectric permittivity is highly sensitive to moisture variations, indicating TDR as a promising tool for moisture measurement of building materials. Owing to the feasibility of the proposed experimental procedure for moisture measurements of real masonry walls, the technique appears to be suitable for field monitoring applications.

The water diffusion attributable to concentration gradients is among the main mechanisms of water transport into the asphalt mixture. The transport of small molecules through polymeric materials is a very complex process, and no single model provides a complete explanation because of the small molecule’s complex internal structure. The objective of this study was to experimentally determine the diffusion of water in different fine aggregate mixtures (FAM) using simple gravimetric sorption measurements. For the purposes of measuring the diffusivity of water, FAMs were regarded as a representative homogenous volume of the hot-mix asphalt (HMA). Fick’s second law is generally used to model diffusion driven by concentration gradients in different materials. The concept of the dual mode diffusion was investigated for FAM cylindrical samples. Although FAM samples have three components (asphalt binder, aggregates, and air voids), the dual mode was an attempt to represent the diffusion process by only two stages that occur simultaneously: (1) the water molecules are completely mobile, and (2) the water molecules are partially mobile. The combination of three asphalt binders and two aggregates selected from the Strategic Highway Research Program’s (SHRP) Materials Reference Library (MRL) were evaluated at room temperature [23.9°C (75°F)] and at 37.8°C (100°F). The results show that moisture uptake and diffusivity of water through FAM is dependent on the type of aggregate and asphalt binder. At room temperature, the rank order of diffusivity and moisture uptake for the three binders was the same regardless of the type of aggregate. However, this rank order changed at higher temperatures, suggesting that at elevated temperatures different binders may be undergoing a different level of change in the free volume.

This paper describes the experimental analysis of joints made with threaded steel rods epoxy-glued into high-density hardwood. Seventy specimens of 10 different types were tested until failure with a pull-pull device. The objective of the study was to evaluate the influence of the geometric and mechanical parameters of the joint on axial strength. Experimental results question the application of the existing joint design formulas to the case of high-density hardwood. Hence, experimental study on glued joints should be extended to include a greater variety of timbers of different densities.

In this paper, the characteristic behaviors of hot-mix asphalt (HMA) in compression are studied by using concepts from the viscoelastic continuum damage (VECD) modeling approach. Temperature and frequency sweep tests with and without confining pressure were performed to determine the linear viscoelastic properties of HMA. The analysis of these tests showed that HMA exhibits significant and reversible stress-hardening behavior. This behavior was subsequently modeled by using a model developed from similar efforts for granular materials. To prove the importance of considering this characteristic behavior, constant crosshead rate tests were performed and analyzed with and without stress hardening. The VECD analysis framework was utilized for this purpose. When stress-hardening behavior was taken into account, it was found that microdamage-induced softening occurred over a range of temperatures from 5°C to 55°C. This finding suggests that microdamage may be significant for conditions in which HMA rutting is a primary concern. It also suggests that the mechanisms of microcrack-induced damage and stress-induced hardening must be investigated to accurately model the global behavior of HMA in compression.

The coefficient of thermal expansion (CTE) was determined for a typical concrete-paving mixture made with six different types of coarse aggregates belonging to the basic class of glacial gravel, quartzite, granite, diabase, basalt, and dolomite. The CTE, compressive strength, and splitting tensile strength of fifteen different concrete mixtures were determined at the age of 28 days. Two parameters, CTE and splitting tensile strength, are the basic input in AASHTO’s new mechanistic-empirical pavement design method. The study revealed a noticeable variation in the values of the CTE of concrete with different types of aggregates. Concrete with quartzite aggregate had the highest value of the CTE followed by dolomite, glacial gravel, granite, and diabase or basalt. The estimated value of the splitting tensile strength of concrete, considering its compressive strength and using AASHTO’s Mechanistic-Empirical Pavement Design Guide for Level 2 design of concrete pavements was discovered to be significantly lower (17–31%) than its actual experimentally determined value.

Constitutive equations for asphalt binders and mixtures are important for predicting pavement performance, characterizing their flow behaviors, and establishing databases. To choose a proper constitutive equation, material characteristics such as single-phase, multiphase, viscous, or viscoelastic fluid must be identified because each phenomena shows its unique equation. Past literature treated rheological behaviors of asphalt binders as a homogeneous single-phase fluid, and asphalt binders were classified differently from those of asphalt concrete mixtures. These generalizations are not always true. This paper presents a classification of material phases and definition of yield stress that are introduced for the first time on a scientific basis. In this classification, constitutive equations for certain modified asphalt binders holding yield stress can be identical to those of asphalt concrete mixtures, when both belong to multiphase fluids. Also, a unique constitutive equation for the linear viscoelastic fluids is proposed to illustrate differentiation from the one of viscous fluids. All constitutive equations suggested here are used in regression analysis of the measured data and their efficacy is proven in excellent curve fittings. Finally, temperature and aggregate concentration effects are added to propose the most versatile multiphase linear viscoelastic constitutive equation.

The fatigue-cracking life of an asphalt mixture measured in the laboratory is generally a small fraction of the fatigue-cracking life observed in the field. One of the reasons for this large difference is the self-healing property of asphalt binders. Self-healing is a process that reverses the growth of fatigue cracks during rest periods between load applications. A thorough understanding of the healing mechanism is required to accurately model and predict the influence of healing on the fatigue-cracking life of asphalt mixtures. Previous studies have used experimental evidence to demonstrate a correlation between chemistry of asphalt functional groups, such as chain length and branching, and healing measured in asphalt binders. One of the mechanisms of healing is the self-diffusion of molecules across the crack interface. This paper demonstrates the use of molecular simulation techniques to investigate the correlation of chain length and chain branching to self-diffusivity of binder molecules. The findings reported in this paper are consistent with observations reported in previous studies and expand on the understanding of the relationship between molecular architecture, self-diffusivity, and self-healing properties of asphalt binders.

This paper presents the workability, mechanical, durability, and microstructural properties of lightweight concrete (LWC) incorporating pumice aggregate, normal-weight gravel aggregate, ASTM type I portland cement, and volcanic ash (VA)–based ASTM Type I blended cement (PVAC). Workability and mechanical properties of LWC mixtures such as slump, air content, compressive strength, tensile strength, density, and modulus of elasticity are described. The durability and microstructural characteristics are investigated by drying shrinkage (DS), water permeability, mercury intrusion porosimetry (MIP), differential scanning calorimetry (DSC), and microhardness tests. The variables in the study include percent replacement (0, 50, 75, and 100% by volume) of coarse gravel aggregate (GA) by coarse volcanic pumice aggregate (VPA), water-to-binder ratio (W/B) by mass, aggregate-to-binder ratio (A/B) by mass, total binder content, and cement types (ASTM type I cement and PVAC). The investigation suggests the production of blended PVAC-based LWCs for structural applications having satisfactory strength and durability characteristics. The use of PVAC induces the beneficial effect of reducing drying shrinkage and water permeability as well as refinement of pore structures and better interfacial transition zone (ITZ).

This paper presents the use of palm oil fuel ash as a pozzolanic material in producing high-strength and high-workability concrete. Portland cement Type I (CT) was partially replaced with ground palm oil fuel ash (PA). PA with 2–5% by weight retained on a sieve No. 325 was used. The concrete mixtures were made with portland cement Type I containing 10, 20, and 30% of PA. Compressive strength, coefficient of water absorption, rapid chloride penetration and corrosion resistance of concretes were determined. Test results indicated that the high-strength high-workability concrete can be achieved by using PA to replace portland cement Type I up to 20%. The resistance to chloride-induced corrosion of concrete containing PA as measured by accelerated corrosion test with impressed voltage is significantly improved in comparison to that of CT concrete.

This study investigates the benefits of modifying asphalt and stone-matrix-asphalt (SMA) mixtures in flexible pavement. $70/100$-penetration-grade asphalt cement and 5% styrene-butadiene-styrene (SBS) triblock copolymer were selected. Unmodified and modified asphalt binders were subjected to physical and compatibility tests. Performance tests, including Marshall stability, static indirect tensile strength and static compressive strength at 25 and 60°C, tensile strength ratio, index of retained strength, rutting resistance, low-temperature cracking, and resilient modulus, were conducted on unmodified and SBS-modified SMA mixtures. The regression relationships between the performance tests were obtained. A mechanistic-empirical design approach was used to estimate the improvement in service life of the pavement or the reduction in thickness of the SMA and base layer for the same service life caused by modifying the SMA mixtures. The test results show that SBS-modified asphalt mixtures perform better than control mixtures. Temperature susceptibility can be reduced by including SBS in the asphalt mixture. The results of multilayer elastic analysis indicate that using SBS-modified SMA as surface layer in pavements reduces the number of construction materials used. Actual savings would depend on the designer’s decision in reducing the thickness of an individual layer.