Journal of Materials in Civil Engineering

The increasing cost of virgin asphalt and aggregate has increased the interest in using higher percentages of recycled asphalt pavement (RAP) in hot mix asphalt (HMA) mixtures. The purpose of this research project was to gain a better understanding of how the addition of RAP affects interaction among the aged and virgin binders and the overall properties of HMA. The effects of the addition of RAP were evaluated on a macroscopic scale by comparing the volumetric properties, dynamic modulus, and strength parameters of a series of specimens containing different percentages of RAP from two different sources. Also, the viscoelastic properties of the blended or rejuvenated binder in the recycled mix were back-calculated from the macroscopic properties of the mix using the Hirsch model. Studies have shown that this back-calculation method offers advantages like elimination of the need for extraction of blended binder, the ability to use indirect tension test specimens, and the use of a mechanistic based approach. The back-calculated viscoelastic properties were subsequently used to determine the low-temperature performance grade of the binder in the recycled mix. This research project showed that the percentage of RAP affects the properties of the mixture with respect to mixture volumetrics, dynamic modulus, and strength.

A number of completed or ongoing studies on different aspects of warm-mix asphalt (WMA) have being conducted in the United States, indicating pavement professionals’ strong interest in exploring the application of this innovative technology. In the summer of 2008, a field trial project using Sasobit-modified WMA was established in the southeastern region of Alaska, which was Alaska’s first experience with a WMA technology. In line with this field experimental feature project, this paper presents a systematic laboratory study of both Sasobit-modified WMA binders and mixes. Engineering properties of Sasobit-modified WMA binders and mixes were experimentally evaluated, and the effects of Sasobit addition on the WMA’s performance in terms of low temperature behavior, rutting resistance, and moisture susceptibility were investigated. Research results identified a number of engineering benefits of Sasobit-modified WMAs over conventional HMA. Sasobit-modified WMAs reduced mixing and compaction temperatures, improved workability and rutting resistance, and had insignificant effect on moisture susceptibility. These effects indicated the suitability of this WMA technology for central and southeastern regions of the Alaska Department of Transportation and Public Facilities (AKDOT&PF). The indirect tension test results showed a decrease of WMAs tensile strength at low temperatures. Additional tests at lower temperatures, along with a more complete thermal cracking analysis need to be performed to obtain a more definitive answer regarding the low temperature performance of these mixes for the northern region of AKDOT&PF.

This paper presents the production, modification, and characterization of biobinder from swine manure. A hydrothermal process was used to convert swine manure to a bio-oil. The bio-oil was fractionated to extract water, solid residue, and some of the organic compounds. The sticky residue after fractionation was used as a replacement for asphalt binder. This paper presents production and chemical and rheological characterization of the biobinder as compared with petroleum-asphalt binder. Biobinder from swine manure was found to be a promising candidate for partial replacement for petroleum-asphalt binder. Considering the limitations imposed on growth of swine farms by manure management practices and environmental regulations and the increasing demand for asphalt binder for infrastructure rehabilitation, this sustainable development will result in major improvements in environmental and economical impacts in both the agricultural and construction sectors. Hence, this study offers a unique approach that simultaneously addresses the increased depletion of petroleum resources the growing swine manure pollution and released greenhouse gases and the development of sustainable alternative for petroleum-asphalt binder. The use of biobinder will improve petroleum-asphalt binder’s low temperature properties while reducing asphalt pavement construction costs; the cost of biobinder production is estimated to be $\$0.13/\mathrm{L}$ ($\$0.54/\mathrm{gal}.$) and that of asphalt binder is $\$0.53/\mathrm{L}$ ($\$2/\mathrm{gal}$).

Shrinkage behavior and fracture properties of five semiflowable self-consolidating concrete (SFSCC) mixes are studied, and their results are compared with those of conventional pavement concrete. In the study, prism tests were employed to evaluate concrete free shrinkage behavior. Restrained ring tests were performed to assess concrete cracking potential. In addition, unrestrained ring tests were conducted and compared with the restrained ring tests. Compressive strength, splitting tensile strength, elastic modulus, and notched beam fracture properties of the concretes were tested at 1, 3, 7, 14, and 28 days. The results indicate that the rates of shrinkage of SFSCCs are generally higher than those of conventional pavement concrete. Compressive strength, splitting tensile strength, and critical stress intensity factor of SFSCCs are comparable to those of conventional pavement concrete, but elastic modulus of SFSCCs is lower than that of conventional pavement concrete. With a higher shrinkage stress-to-fracture strength ratio, SFSCC mixes have higher potential for shrinkage-induced cracking than conventional pavement concrete. The use of a clay additive, purified magnesium alumino silicate, further increases the rate of SFSCC shrinkage.

Recycled asphalt pavement (RAP) has been increasingly used as an energy efficient and environmentally friendly paving material and is currently the most reused and recycled material in the United States. RAP has been used in new hot mix asphalt (HMA) mixtures and in base courses for pavement construction. When RAP is used as a base course material, the presence of asphalt in RAP may cause excessive deformation under traffic loading. Geocell, three-dimensional (3D) polymeric geosynthetic cells, was proposed in this study to minimize the deformation by confining the RAP material. Full-scale accelerated pavement tests were conducted to evaluate the effect of geocell reinforcement on RAP base courses over weak subgrade. Two types of RAP were used and a total of seven geocell-reinforced and unreinforced RAP sections were tested under full-scale traffic loads. The road sections were excavated and examined after each moving wheel test. The benefits of geocell reinforcement were evaluated in rut depths for a specific number of passes of the wheel load and the angle of stress distribution from the surface to the base course-subgrade interface. The test results demonstrated that the novel polymeric alloy geocell reinforcement improved the performance of unpaved RAP sections by widening the stress distribution angle and reducing the rut depth if the base courses were equally compacted in unreinforced and reinforced sections.

This paper presents the results from a laboratory study in which hot-mix asphalt (HMA) mixtures with No. 4 sieve screened reclaimed asphalt pavement (RAP) were characterized for their cracking resistance through laboratory performance testing. A typical surface mixture commonly used in the state of Tennessee was evaluated at 0, 10, 20, and 30% RAP contents. Two types of aggregate (limestone and gravel) and three types of asphalt binders (PG 64-22, PG 70-22, and PG 76-22) were used in this study. Mixture cracking resistance was evaluated through Superpave indirect tension (IDT), beam fatigue, and semicircular bending (SCB) tests. The results from this study indicated that the inclusion of RAP generally increased stiffness and indirect tensile strength; however, it generally compromised cracking resistance for the mixtures studied. Mixture properties changed significantly at 30% RAP content as compared to those with 10 and 20% RAP. Field projects validated the findings from the laboratory study.

Conventional cold-weather concreting is expensive and very energy inefficient. Common practice requires artificial heating of the raw materials and the surrounding environment to create suitable curing conditions for normal concrete. Antifreeze concrete is a new approach to cold-weather concreting without the need for artificial heating. This saves time, money, and energy. The antifreeze concrete technology has been proven in numerous full-scale field demonstrations and is compatible with current concrete construction practices. A laboratory study established the practicality of using antifreeze concrete and developed the tools to mix and cure concrete in subfreezing temperatures. Eight candidate antifreeze formulations were developed in the laboratory and subjected to initial screening tests that showed they were capable of being workable, entraining air, and meeting the design freezing point. Performance testing showed that the strength gain when cured at $-4°\mathrm{C}$ is as good as conventional concrete cured at $+5°\mathrm{C}$ and that antifreeze mixtures can be made durable. High dosages of chemical admixture used in antifreeze concrete mixtures were not harmful to the concrete. It is recommended that agencies conduct testing on their own to become familiar with the antifreeze mixtures before widespread use.

This research investigated the size effect of hydrated lime on the moisture susceptibility of warm-mix-asphalt (WMA) mixtures with selected additives. A superfine hydrated lime used in the study was produced from regular hydrated lime (RHL) by a Los Angeles abrasion machine. The superfine lime was measured to be 660 nm, approximately half of the RHL size of 1.3 µm, a sub-nano-sized hydrated lime (SNHL). Scanning electron microscope (SEM) pictures were taken to observe the difference of the crushed lime in size, shape, and texture. Experiments for antistripping properties, such as indirect tensile strength (ITS), tensile strength ratio (TSR), flow, and toughness were conducted on WMA mixtures containing SNHL and RHL as control samples. A total of 18 mixtures and 108 specimens were prepared from three types of aggregate, three WMA additives, and two types of lime. The results indicated that the microstructures of the SNHL and RHL are irregular: the lime particles have fractured and rough surfaces with sharp angles; some small spherical particles in the nano size were found in SNHL but not in RHL. Also, WMA mixtures using SNHL have greater ITS and TSR than those using RHL; an increases of 8% in ITS and 10% in TSR by using SNHL over RHL were observed for the WMA mixtures investigated. Finally, the antistripping properties of WMA mixtures containing SNHL were affected predominately by aggregate type and the WMA additive.

The objective of this study was to evaluate the use of crumb rubber (CR) from waste tires and engineered additives as a rejuvenator to high reclaimed asphalt pavement (RAP) content asphalt mixtures. Six asphalt mixtures were prepared by mixing aggregate blends with four asphalt binders, an unmodified asphalt binder classified as performance grade (PG) 64-22, two polymer-modified binders classified as PG 70-22M and PG 76-22M, and a PG 76-22 crumb-rubber-modified binder. The RAP content was varied from 0–40% and crumb-rubber additives were blended with the unmodified binder by using wet and dry processes. Hot-mix asphalt (HMA) mixture testing included an evaluation of rutting susceptibility, moisture resistance, and resistance to cracking using the flow number test, the loaded-wheel tracking test, the dynamic modulus test, the modified Lottman test, the dissipated creep strain energy test, and the semi-circular bending test. Results of the experimental program indicated that the addition of the CR additives rejuvenated the blended asphalt binder for the HMA mixture with high RAP content. The use of high RAP content with crumb rubber as a rejuvenator in the preparation of HMA is expected to provide adequate moisture resistance and superior rutting resistance as compared to conventional mixtures. However, because of the hardening properties of the mix prepared with high RAP content, the fracture and cracking resistance of the produced mixture was reduced compared with polymer-modified mixes.

This research project evaluates the low-temperature performance of energy-efficient and environmentally friendly hot-mix asphalt (HMA) paving materials. Innovative materials gaining interest in the asphalt pavement industry includes warm mix asphalt (WMA), recycled asphalt shingle (RAS), reclaimed asphalt pavement (RAP), and bioasphalt. The materials are used as modifiers in typical HMA to enhance low-temperature field performances. Sasobit compounds at 0.5, 1.0, and 1.5%, by weight of performance grade (PG) 52-34 asphalt binder, are used to design the WMA. Five and 10% of RAS were also added to a PG 52-34 asphalt binder. 50% of RAP combined with 50% of the base PG 58-28 binder, and 100% RAP extracted from the PG 58-28 HMA, were prepared and tested. Bioasphalt was produced from swine waste and used to modify PG 64-22 asphalt binder. By using the Superpave bending beam rheometer (BBR) and the new asphalt binder cracking device (ABCD) method, the thermal cracking performance of the samples were tested. The results showed that (1) the ABCD method can be used alongside or as a confirmation test for the BBR in evaluating the low-temperature cracking resistance behavior of asphalt binders; (2) adding WMA beyond a certain percentage could potentially reduce the low-temperature cracking performance of asphalt binders; and (3) swine waste bioasphalt can enhance low-temperature asphalt binder performance.

In this study, cement-stabilized granite mill tailings were used as a subbase material in highway construction. The properties of the cement-stabilized mill tailings were evaluated through laboratory testing and compared to those of cement-stabilized crushed stone. The results show that the cement-stabilized mill tailings exhibited relatively high strength and stiffness that could meet the requirements of pavement structure. However, the high drying and thermal shrinkage of cement-stabilized mill tailings required better curing during construction in order to avoid cracking. A field project validated the findings from the laboratory tests.