Journal of Materials in Civil Engineering

This paper describes the development of a portable dynamic energy calibrator (PDEC) for mechanical Proctor compaction machines along with an analysis of system variance on a silty sand’s (A-2-4) dry unit weights. The PDEC measures a rammer’s kinetic energy delivered to the sample and the compressive energy retained in the sample. The monitoring system uses a photoelectric gate and impact force sensor attached to the machine. When the rammer mass is included, the system’s impedance can be calculated. Next, 30 Florida Department of Transportation (FDOT)-approved machines throughout the state were tested, and summary statistics (i.e., mean, standard deviation, and so on) of the kinetic and compressive energies of the machines were found. Scatter plots of hammer kinetic energy along with sample energies allowed for identification of poorly functioning machines (e.g., low-impact energies or variations in mold support). Finally, a series of blind modified compaction tests were performed on A-2-4 soil at six labs at dry and wet of optimum. A regression analysis of the mean and variance of dry unit weight as a function of moisture content, kinetic energy, and sample energy was undertaken. Approximately 50% of the measured dry unit weight variance was associated with variance of kinetic energy, sample energy, or sample moisture. The other 50% of the variance was attributed to operator influence (i.e., sample preparation, lift thicknesses, moisture determination, and so on), which was not measured in this study.

This investigation reports the influence of the type of binder and crumb rubber gradation and dosage rate on the creep and recovery properties of crumb rubber modified bitumen (CRMB). Two types of binders, air blown and blended, were used with two gradations of crumb rubber, fine and coarse, at three dosage rates, 8, 10, and 12%. The morphology of these 12 binders were characterized by using environmental scanning electron microscopy (ESEM). Furthermore, energy dispersive X-ray spectroscopy was carried out on the samples to identify the chemical composition of the network structure as seen from ESEM. All the samples were subjected to creep and recovery tests by using a dynamic shear rheometer at five different temperatures of 46, 52, 58, 64, and 70°C. A generalized Voigt-Kelvin model was used to model the creep and recovery response of the material for all the temperatures tested. It was found that the nature of the binder plays a critical role on the development of morphology of CRMB. This morphology influences the creep and recovery characteristics of the final blend. The fibril diameter and the number of network junctions as determined through the image processing of ESEM images and the Voigt-Kelvin model parameters were found to be related.

The results of research are reported in this work that evaluated the benefits of the stabilization of Type 1 subbase material to which had been added a high volume of limestone quarry waste dust. There is extensive interest in introducing large volumes of quarry waste dusts to the Type 1 subbase that is used in the construction of the vast majority of foundations for roads and other pavements in the United Kingdom. Previous experience has indicated that replacement of 10–30% of Type 1 subbase with limestone quarry waste dust made the mixture inadequate for pavement foundation purposes. When pulverized fuel ash (PFA) and lime were added to these materials, the new mixture improved to a level that made the materials suitable for use as subbase in pavements. However, lime was still a costly industrial product and a major ${\mathrm{CO}}_2$ emitter. The replacement of lime with another capable PFA activator of waste or recycled origin was sought. After examining several potential wastes, it was found that air pollution control (APC) residues could not only activate the PFA to stabilize the Type 1 subbase containing high volumes of limestone quarry waste dust, but created a final mixture of more desirable mechanical properties than generated by PFA–lime. Unconfined compressive strength, resilient modulus, and plastic deformation of both PFA–lime and PFA–APC residue stabilized materials have been studied to reveal the performance of the novel binder of PFA and APC residues in enhancing the mechanical properties of Type 1 subbase to which was introduced high volumes of limestone quarry waste dust. The final mixture has significantly contributed to accommodating three types of waste materials to be used in pavement foundations.

The Olympic Rowing-Canoeing Park is one of 11 new venues constructed for the 2008 Olympic Games in Beijing. The soil materials excavated during its construction were primarily silty sand and sandy silt. Laboratory tests were carried out on these two soil materials with and without cement stabilization. A test embankment was constructed, and a 6-m high geogrid-reinforced retaining wall was built with the sandy silt material as the backfill, in which soil pressure and strain in the geogrid were measured. Sandy silt material was found to be more desirable than the silty sand for use as the backfill material in building the rowing-canoeing course and ancillary buildings. Shear strength, especially cohesion, increased after cement stabilization, and resistance against water erosion also greatly increased. Construction of the test embankment indicated that higher uniformity of the cement-treated soil layer may be achieved by a mixer than by disc harrow. For the geogrid-reinforced retaining wall, the strain in the geogrid was between 0.1 and 0.9%, much smaller than the strain corresponding to the ultimate tensile strength. This research was of great help in the design and construction of the rowing-canoeing course and ancillary buildings.

This paper reports a laboratory investigation aimed at evaluating the potential of polymer binders to stabilize pavement subgrades in Qatar. The conclusions regarding the impact of the polymer stabilizers are based on comparisons with selected physical, chemical, mechanical, and microstructural properties of natural Qatari subgrade soil and soils stabilized with the traditional standard, portland cement (PC). The results demonstrate that the polymer binders modify the Qatari subgrade soils resulting in more favorable engineering properties: for example, the compressive strengths of the polymer-stabilized soils are superior to those of the unstabilized soils and those stabilized using PC. The mechanical properties of the stabilized and unstabilized soils were incorporated in the analysis of asphalt pavement sections using the state-of-the-art protocol for pavement design and analysis. Results of the analysis further demonstrated the benefits of using stabilized subgrade soils in improving pavement performance. Of particular practical importance is that polymer subgrade stabilization significantly reduces subgrade rutting. Consequently, polymer subgrade stabilization is a key consideration for perpetual pavements, especially considering the extremely high truck traffic in Qatar. Although the work reported in this paper was carried out with Qatari soil, the results are expected to be relevant to other types of soil and weather conditions experienced throughout the Middle East and in similar climates throughout the world.

Waste foundry sands (WFSs) represent the highest amount of solid wastes generated by foundries. The high cost of landfilling and the potential uses of waste foundry sand in construction purposes have prompted research into their beneficial reuse. Microbial modified mortar/concrete has become an important area of research for high-performance construction materials. This study investigates the effects of fungal (Eupenicillium crustaceum) treated waste foundry sand on concrete properties as partial replacements of sand. It shows an increase in compressive strength up to 24% and decreases in water absorption (44%) and porosity (50%) in concrete made with fungal treated 20% WFS after 28 days of curing, compared to untreated concrete made with 20% WFS. The strength improvement is attributable to microbially induced mineral formed by fungi, often referred to as calcified filaments, confirmed by scanning electron microscopy and energy dispersive spectra. The formation of calcium oxalate (weddellite) in urease broth by fungi was confirmed by X-ray diffraction. This ability of fungal culture to form the biomineral results in improvements to concrete properties.

The goal of this paper is to study the feasibility of using geopolymers based on Class C fly ash (CFA) to self-solidify/stabilize (S/S) heavy metal wastes (HMWs). The S/S effectiveness and mechanism of Pb(II), Cr(VI), and Hg(II) by CFA-based geopolymers were studied by compressive strength test, Toxicity characteristic leaching procedure (TCLP), X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), and scanning electron microscope–energy dispersive X-ray analysis (SEM-EDXA). The results show that with HMWs the compressive strength has a slight decrease, and the lowest 28 days strength of the CFA-based geopolymers was 51.1 MPa. All leaching concentrations of heavy metals from geopolymers are far lower than the maximum concentration limits, and S/S ratios of these heavy metal ions are very high. The XRD patterns show no significant changes in the mineral compositions when heavy metals are present. Compared to the FT-IR spectrum of the blank specimen without heavy metals, the peaks of $\mathrm{Si}\text{-}\mathrm{O}\text{-}\mathrm{Si}/\mathrm{Si}\text{-}\mathrm{O}\text{-}\mathrm{Al}$, Si-O, and $\mathrm{OH}/\mathrm{H}\text{-}\mathrm{O}\text{-}\mathrm{H}$ are shifted in geopolymers with HMWs. The SEM-EDXA data reveal other shapes of products coexist within the amorphous geopolymeric gels. It indicates that heavy-metal ions are physically encapsulated and chemically bonded in the three-dimensional geopolymeric network. This work is beneficial to the understanding and future application of CFA-based geopolymers as S/S materials to make HMWs less available as environmental pollutants.

Viscosity-modifying admixtures (VMAs) are often used to increase the robustness of self-compacting concretes (SCCs); however, concretes produced in this way require a higher cement or additions content than those made with additional limestone filler and thus are less attractive from the point of view of economics and sustainability. In light of this, the objective of this paper was to study the robustness of a SCC made with VMAs and low filler content and to determine whether it was comparable to a commercial SCC, with high limestone filler content and less cement. Three types of SCCs with water/cement (w/c) = 0.6 were produced with water contents varying between $-7.5\%$ and $+7.5\%$. A linear regression model was constructed from the experimental data for each of the properties analyzed so as to provide an easy method of calculating the acceptable percentage of water-content variation in concrete that satisfies certain robustness requirements. This model provides a comparison of the different types of SCCs and thus assists the concrete producer to select the appropriate mixes. The results show that variations in flowability and compressive strength due to changes in water content were very similar in the three concrete types considered in this study. However, when filler was replaced by VMA, the material’s cohesive properties (viscosity and segregation resistance) showed improvement. In the SCC made with additional limestone fines, slump flow spread time $T_{50}$ and V-funnel time were the properties that contributed the most to reducing the material robustness. It was also observed that segregation resistance and compressive strength do not play a significant role in the robustness of SCCs under consideration.

To investigate the stress distribution in recycled aggregate concrete (RAC) under uniaxial compression, modeled recycled aggregate concrete (MRAC) was studied by numerical simulation. The mechanical properties of interfacial transition zones (ITZs) of RAC were measured by the nanoindentation technique. A two-dimensional numerical study of the stress distribution characteristics of MRAC under the uniaxial compression is presented. The simulation was verified by experimental results. A parametric analysis is then conducted to study the sensitivity of each phase’s mechanical properties and the amounts of old cement mortar in the MRAC. Simulation results demonstrate that a concentration of tensile stress and shear stress appears around new and old ITZ regions. It is found that when the elastic modulus of natural aggregates increases, the magnitude of tensile stress concentration becomes higher, whereas as the elastic modulus of ITZs increases, the magnitude of stress concentration decreases. It is also shown that the higher relative elastic modulus of new cement mortar compared with that of the old cement mortar significantly reduces the stress concentrations at the regions between recycled coarse aggregate particles. The amount of old cement mortar affects the stress distribution in the new ITZ much more obviously than that in the old ITZ.

Changing lifestyles over the past few decades have brought about an increase in the types and volume of waste. Nowadays, waste is considered one of the world’s main problems. The incorporation of waste in structural and nonstructural elements has therefore been studied, primarily in renders. However, data are scarce on the influence of using rubber aggregates from shredded tires in mortars. This work presents a performance-based analysis to test the viability of using these modified mortars for wall coatings. It presents unprecedented analyses of some durability-related properties and the influence of the crushing process in the overall performance of mortars incorporating rubber. Even though the results show, as expected, that the incorporation of rubber particles is detrimental to both compressive and flexural strength, those changes do not impair its use as renders under normal conditions. Furthermore, the incorporation of rubber leads to a significant reduction of the modulus of elasticity of the mortar. The added rubber also improves its impact-resistance characteristics and some other durability characteristics of these modified mortars compared with those of conventional mortars, which shows that this could be a future viable alternative for wall coatings.

The use of nanoindentation to study asphalt is aimed at understanding the relationship between properties of asphalt binder at various length scales. A combination of atomic force microscopy (AFM) imaging and nanoindentation is used to determine the relaxation moduli of bimodal and trimodal distributions of asphalt microphases to assess differences between macroscale and composite nanoscale viscoelastic behavior. The relaxation modulus values extracted from age-altered phases of the same asphalts provide important relationships between microstructural changes depicted in AFM images and changes in composite viscoelastic properties obtained from the measurements. This paper provides key information regarding asphalt microrheology, which will yield improved input values for asphalt prediction models and enhanced pavement performance. Based on comparison of the composite viscoelastic properties obtained from this study to values obtained at larger length scales, it is apparent that relaxation modulus values decrease as the length scale increases. This finding serves as the basis for ongoing studies by the authors and other researchers in the areas of asphalt nanomodification, chemical mapping, and modeling of nanodamage using AFM.

Over the years, the Indiana Department of Transportation (INDOT) has changed its emphasis from construction to preservation of public highways. As such, there is great interest in assessing cost efficacy of a pavement preservation strategy. This paper aims to present the functional and structural benefits of microsurfacing applications at highway sections in Indiana. To achieve this goal, comprehensive monitoring and data analysis was performed using the pavement condition rating (PCR), structure number (SN), and surface roughness [international roughness index (IRI)] for in situ performance evaluation. According to the deflection and roughness analysis, an improvement was observed in SN and IRI during the early life of the pavement. Furthermore, no significant difference was obtained over the following 2 years. Application of the microsurfacing resulted in a significant rise in PCR and SN and decline in IRI. A similar result was found at the resurfacing site. Pavement with microsurface sections had stable roughness with only a 2-point increase every year. The two control sections (SR-68 and SR-145) have had 4-point increases on average. The IRI for SR-58 resurfacing was $762\mathrm{mm}/\mathrm{km}$ ($48\mathrm{in}\mathrm{.}/\mathrm{mi}$) in 2009 (after construction), which is almost half of the 2008 (before construction) IRI value. The rates of decline of the SN and IRI were no different statistically for untreated control sections, and the rate of decline of the PCR was slightly higher than in the pavement preservation project, including resurfacing and microsurfacing. The cost study indicated that microsurfacing would be deemed cost effective if it could provide more than 1.6 years of service life, and resurfacing would be cost effective if it could provide more than 3 years of service life. Considering cost as well as performance, pavement preservation should be an effective strategy to eliminate or retard damage. If applied properly, microsurfacing is an economical alternative to conventional resurfacing. The case study results demonstrate that microsurfacing is a cost-effectiveness treatment in addressing pavement distresses and in extending pavement life in general.

Photocatalytic technologies offer a unique benefit to road materials due to their potential to support depollution reactions of nitrogen oxide (${\mathrm{NO}}_{\mathrm{x}}$) and their versatility. The aims of this research were to investigate the wear resistance of photocatalytic asphalt slabs under repeated loads and to quantify the effect of contaminants such as dirt (fine particles), salt (sodium chloride) and deicing solution (salt plus water) on photocatalytic effectiveness. Accelerated loading tests (wheel tracking test) and skid resistance (British pendulum test) allowed the characterization of slab behavior over different steps of cycles. A specific laboratory setup was adopted to measure the reduction in concentration of pollutants as nitrogen oxide in accordance with European standards. Results showed a decrease over progressive load cycles in depolluting effectiveness and skid resistance of photocatalytic slabs, and deicing solution had the largest negative effect. The negative impact was largely dependent on the number of cycle and the contaminant type.