Journal of Materials in Civil Engineering

Warm mix asphalt (WMA) has received considerable attention in the past few years to reduce energy consumption and pollutant emissions during hot mix asphalt (HMA) production and placement. However, many concerns and questions are still unanswered regarding the field performance and environmental benefits of WMA. In this study, WMA mixtures containing reclaimed asphalt pavement (RAP) were evaluated in a field project in Ohio. The project included using Aspha-min, Sasobit, and Evotherm in three test sections. Furthermore, a control section was also produced so that a side-by-side comparison could be made between WMA and HMA mixtures. Temperature and emissions were monitored during the production and placement of the considered WMA and HMA mixtures. In addition, core samples were obtained from the evaluated sections and tested in the laboratory. Roughness and rutting measurements were also conducted during the first 46 months of service. The results of this study showed that the emissions were significantly reduced during the production and placement of WMA mixtures as compared to the control HMA mixture. In addition, although WMA mixtures were compacted at much lower temperatures, they achieved higher in-place density than the control HMA mixture. The results of the laboratory tests conducted on core samples showed that the WMA mixtures had higher indirect tensile strength (ITS) than the HMA mixture after 3 months of service. However, the HMA ITS value increased more rapidly with time than that of the WMA. The moisture susceptibility test results demonstrated that the Sasobit and Evotherm mixtures exhibited acceptable resistance to moisture-induced damage. Finally, the collected performance data indicated that the WMA and HMA sections had similar International Roughness Index (IRI) values after 46 months of service. In addition, no measurable rutting was observed in any of the test sections.

This work focuses on the feasibility of reusing and valorizing rubber aggregates from shredded worn tires in cement paste. This kind of eco-material could be used, for example, in special buildings, roads or pavement, or recreational areas. Fractions of the volume of sand were substituted by the same volume of rubber aggregates. The volume contains the ratio of rubber aggregates ranging from 0 to 50%. Nevertheless, compressive and flexural strengths decrease when the volume ratio of rubber aggregates increases in mortar-rubber aggregate mixtures. A solution to the decrease in mechanical strengths consists of adding mineral particles, such as siliceous or limestone fillers. Experimental characterization of the mechanical behavior of mortar-rubber aggregates containing either siliceous or limestone fillers is developed in this paper. It is observed that the use of either siliceous filler or limestone filler enhances mechanical properties. Modeling is developed to predict compressive and flexural strengths of mortar-rubber aggregate mixtures using the fuzzy logic method. Experimental mechanical results are compared with modeling.

Porous asphalt mixtures have been used for more than 60 years, but it was not until 1974 that the first formalized procedure was created by the Federal Highway Administration to design mixtures for open-graded friction courses (OGFC). Since that time, there have been several other mix design procedures developed and adapted, mainly for OGFCs on high-volume roadways. In the past decade, porous asphalt pavements have been gaining popularity as a storm water best management practice and utilize similar mixtures as those used for OGFCs. However, for any porous mixtures to perform as intended, they must be designed and constructed properly. Across the United States, there are currently more than 20 different methods used to design these mixtures. The objective of this research was to compare the different mix design procedures currently used in the United States. The results indicated that some of the procedures result in a range of design binder contents instead of a single value. This does not provide much guidance to inexperienced designers, which could result in pavement performance issues that could deter the future use of porous asphalt mixtures.

This paper reports the seismic responses of geosynthetically reinforced walls with two types of backfills using shake table tests. The backfills are tire-derived aggregates (TDA) and poorly graded sand, respectively. Mechanically stabilized earth (MSE) walls with reinforced TDA backfill have not been fully tested under seismic conditions. In this study, two geosynthetically reinforced walls are tested on a one-dimensional shake table. A section of reduced-scale MSE wall (1.6 m high, 1.5 m deep, and 1.5 m long) is built in a box that is anchored on a shake table that can generate earthquake excitations obtained from actual field recordings. Layers of geogrid are used as reinforcement. The geosynthetic reinforcement is based on static external and internal stability design. In each test, the segmental MSE wall is instrumented with accelerometers, linear variable differential transformers, linear potentiometers, and dynamic soil stress gauges to record the accelerations, wall vertical deformations, horizontal deflections of the wall face, and transient effective stresses during the shaking, respectively. The experimental study reveals the advantageous seismic performances of a geosynthetically reforced wall with TDA backfill over an MSE wall using traditional granular backfill.

Bamboo is an excellent eco-friendly construction material because of its high renewable rate, embodied energy, reduction of pollution, high strength-to-weight ratio, and low cost. However, the use of round bamboo is limited because of its variations in dimensions, properties, and composition and the difficulty of making connections. Laminated bamboo has the potential to overcome these difficulties. Therefore, its mechanical properties and the behavior of the connections need to be established. In this research, the dowel-bearing strength of glued laminated Guadua angustifolia Kunth bamboo is experimentally determined under nail and threaded bar fasteners with different diameters and in different loading directions. A three-dimensional FEM computational model is developed with excellent agreement with experimental results. It was found that, similar to wood, the bearing strength depends on both the diameter and the specimen width-to-diameter ratio. The local behavior of the zone under the fastener is different from the bulk material. Expressions to determine these local properties as functions of the bulk properties are proposed as well as equations for the bearing strength in terms of the specimen width-to-fastener diameter ratio.

Road surface profile is an important factor that affects the dynamic responses of the vehicle, which in turn affects pavement responses. In this study, a complete two-dimensional (2D) axle-tire-pavement interaction finite-element model was developed to investigate the effects of a rutted surface on near-surface pavement responses. The results indicate there is a significant difference in tire-pavement contact stress distributions between a rutted surface and a flat surface. The presence of a rutted surface increases both the propensity for top-down cracking and the severity of instability rutting. The observed trend indicates that the greater the existing rut severity is, the more likely it is for top-down cracking and increased rutting to occur.

Compacted landfill liner is an integral part of a waste management system, which minimizes the migration of harmful contaminants to geoenvironment and groundwater. Low hydraulic conductivity is the most important requirement for geomaterial used as compacted landfill liners. Because of this, high plastic geomaterials are preferred for such applications. Therefore, plasticity characteristics can be used as an initial guideline for assessing the suitability of materials used as a landfill liner. Such guidelines are important because of the fact that hydraulic conductivity determination is extremely time consuming for plastic geomaterials, and a quick assessment of material properies is always expected in the planning stage of the project. The existing methodology on the basis of plasticity criterion is not suitable for high-plastic soil, which otherwise is a very useful material for landfill liners. Considering this, the present study deals with the re-evaluation of plasticity-based criterion for assessing the suitability of medium and high-plastic geomaterials used as a compacted landfill liner. The development of the criterion is on the basis of the test results of bentonite–fly ash mix, which is used to represent a wide range of plasticity. The proposed criterion is further verified on the basis of the data reported in the literature. The present study also demonstrates the potential application of fly ash in combination with bentonite for landfill liner construction.

The objective of this study is to introduce a new approach to recycling asphalt shingles in asphalt paving construction in which recycled asphalt shingles (RAS) are ground to ultrafine particle sizes and blended with asphalt binder through a wet process. In the proposed wet process, the ground recycled material is blended with the binder at a high temperature prior to mixing with the aggregates. Two unmodified binders that are classified as PG 64-22 and PG 52-28 were blended with two contrasting sources of RAS at a modification content ranging from 10–40% by weight of the binder. The use of RAS modification through the proposed wet process was successful in the laboratory. Based on the results of the experimental program, the use of RAS modification through the proposed wet process would generally improve or not influence the high temperature grade of the binder, but it may reduce the low temperature grade of the binder. As demonstrated in this study, an optimum shingle content may be identified that will improve the high temperature grade without influencing the low temperature grade of the binder. Using confocal laser-scanning microscopy (CLSM), wax crystals ranging from 4–8 μm in size were successfully detected. However, wax crystals were not detected in the RAS-modified binder, which may indicate that the wax molecules are absorbed by the RAS material. Results of high-pressure gel permeation chromatography (HP-GPC) showed that the proposed wet method of modification produced a slight increase in the high molecular weight (HMW) ($>3,000\text{daltons}$) content in the prepared blends at higher RAS contents, suggesting that a fraction of the RAS binder contributes to the blend properties.

The mechanistic-empirical pavement design guide (MEPDG) is the research version of the newly released DARWin-ME software by AASHTO. MEPDG includes two models for Levels 2 and 3 hot-mix asphalt (HMA) dynamic modulus ($E^{*}$) predictions. The two models are NCHRP 1-37A and NCHRP 1-40D. The primary difference between the two is the binder stiffness parameter; viscosity or shear modulus. Moreover, MEPDG includes three levels for binder stiffness characterization: viscosity for Level 1 conventional binders, shear modulus for Level 1 superpave binders, and default values for Level 3. The influence of the binder characterization input level on the performance of the MEPDG $E^{*}$ predictive models is evaluated in this paper. To calibrate the models for Idaho, 27 HMA mixtures commonly used in Idaho were investigated. Results showed that the performance of the investigated models varied based on the temperature and the binder characterization method. The NCHRP1-37A $E^{*}$ model with MEPDG Level 3 binder inputs yielded the most accurate and least biased $E^{*}$ estimates. The accuracy of this model was further enhanced by introducing a local calibration factor.

The effects of curing time and reheating on the short-term performance of stone-matrix asphalt (SMA) mixtures with various warm-mix additives (i.e., Evotherm, Sasobit, and foamed asphalt) was evaluated in laboratory performance tests. The laboratory tests included complex modulus, loaded wheel track, indirect tensile (IDT) strength, and semicircular beam (SCB) fracture. In the tests, plant-produced mixes that were sampled from a field overlay project were compacted in the laboratory with and without reheating, and performance tests were conducted at various curing times after compaction. The effect of curing time on mixture characteristics was dependent on the mixture type and performance test considered. The mixtures containing warm-mix additives showed similar variations in mixture properties due to curing time compared to the control mixture. The reheating process caused asphalt mixtures to have greater modulus, tensile strength, and rutting resistance but smaller fracture resistance. Among the mixtures containing various warm-mix additives, the mixture containing Sasobit showed the relatively smallest changes in mixture properties attributable to reheating. Finally, it was discovered that the warm SMA mixtures showed variations in different performance characteristics, depending on the type of warm-mix additives and recycled materials, than the control mixture.