Airfield and Highway Pavements 2019: Testing and Characterization of Pavement Materials

A typical dense graded asphalt mixture was produced in a drum plant, a batch plant and in the laboratory, all targeting the same volumetric composition. Samples from each production method were tested for volumetric composition, Marshall properties, properties indicative of resistance to deformation, fracture, and moisture damage, as well as complex (flexural) modulus over a range of frequencies and temperatures. The results indicated that each different production method produced consistent asphalt, but significant differences were observed between the different production method volumetrics. These significant differences did not affect the Marshall properties. However, significant differences were observed in deformation resistance, moisture resistance, and complex modulus results. Because of the interaction between asphalt volumetrics and other asphalt properties, it was not clear whether the observed differences in performance properties were a result of the volumetric composition differences, or a fundamental difference in the asphalt production methods.

A laboratory setting is a more controlled environment compared to the field where the environment can be more challenging due to heat and weather control. Comparison of performance measures such as rutting and cracking resistance are viable tests to investigate the difference between laboratory and field mixes. The research was done to compare rutting and cracking resistance of laboratory and field mixes. Performance grade (PG) 58-28 and PG 64-28 were considered for testing. Both performance grades were taken from highways in North Dakota with separate mix designs. The nominal maximum aggregate size (NMAS) for all mixes was 12.5 mm. Specimens for both laboratory and field mixes (150 mm diameter and 75 mm high) were compacted to a target of 7% air voids using a gyratory compactor. Asphalt pavement analyzer (APA) was used to determine rutting resistance of the specimens. Disk-shaped compact tension (DCT) and semi-circular bending (SCB) were used to determine low-temperature and fatigue cracking resistance, respectively. The DCT was performed at 10°C above the low-temperature PG grade. Cracking resistance was measured in terms of fracture energy. The results showed that for PG 58-28 the laboratory mix was more rut resistant than field mix whereas for PG 64-28 the field mix was more rut resistant than laboratory mix. The lab mixes were more cracking resistant than the field mixes for both binder grades. Fracture energy for virgin mixes was higher than mixes with reclaimed asphalt pavement (RAP) as expected.

Several research and state highway agencies are using or considering to use the overlay tester (OT) test for assessing the cracking potential of asphalt concrete (AC) mixtures for flexible pavements. Although the OT test simulates effectively the cracking mechanism on AC specimens, the variability of the results from the same OT device, or the interchangeably of the results from different OT devices has been a challenge, especially for dense-graded mixtures. This paper reports on a comparative evaluation of the test results from three available OT devices. The repeatability and reproducibility of the testing mechanism of the three devices were first evaluated utilizing synthetic specimens with mechanical properties similar to typical AC mixtures. A typical dense-graded mixture with a 12.5 mm nominal maximum aggregate size was also used for this purpose. Eight specimens were tested on each device. Apart from the number of cycles to failure, the results were assessed with an alternative analysis methodology that specifies the critical fracture energy (CFE) and crack progression rate (CPR) as performance indices. The variability of the results from each individual OT device improved when the proposed parameters were used to analyze the test results. The reproducibility of the test results was acceptable among the three different devices. The paper concludes with practical recommendations to ensure that the OT test results from different devices are repeatable and reproducible.

The binder content is one of the most important properties of HMA that can affect the performance of the mixture. Its determination is very important, especially in the case of recycling solutions. Different methods are available but centrifuge extractor and ignition methods are very common. Both methods have advantages and disadvantages that should be considered in order to make the choice most adequate. Based on proficiency tests, the paper has the objective to present the comparison of both methods described in the European standards EN 12697-1 and EN 12697-39 related to centrifuge extractor and ignition tests respectively. The paper demonstrates that there is a tendency to obtain higher values of binder content by ignition method. It was also confirmed the importance of the separation of mineral matter in the case of centrifuge extractor method. The precision of the test methods related to repeatability and reproducibility conditions is also presented. Precision data was compared with values indicated in the corresponding standards.

In general, asphalt concrete (AC) pavements are constructed with different types of aggregates, gradations, binder types, anti-stripping agents, and technologies. Hot mix asphalts and warm mix asphalts (HMA/WMA) mixtures are compacted at high or low temperatures to reach the specified density. Due to environmental influence and repeated traffic loading, AC pavements decay once they are under traffic stresses. Permanent deformation (rutting) in AC pavements manifests itself as longitudinal depression in the wheel paths where traffic fluctuates. The unrecoverable cumulative deformation that occurs in the wheel path under high temperatures as a result of the traffic loading is named permanent deformation or rutting. This study analyses the effect of different parameters (type of mixture, gradation and aggregate, and binder grade) in asphalt concrete (AC) mixtures using the Hamburg wheel tracking device (HWTD) destructive test. Twenty Superpave III (SP III) mixtures with different types of mixtures, gradations, types of aggregates, and types of performance binder grade were collected in New Mexico and tested at three different temperatures (40°C, 50°C, and 60°C). Results showed a significant effect of test temperature in HWTD results. Warm mix asphalts (WMA) mixtures generally showed lower impression depths than hot mix asphalts (HMA) mixtures. Aggregates performed differently under this test with good and bad results. Dacite, sand and gravel, river deposits, limestone, quartzite, limestone, and shale were studied. Similarly, different binder grades showed different behaviors when tested at different temperatures.

Performance-related testing—including cracking and rutting—as a feature of the asphalt mixture design process has garnered significant attention in recent years. One salient question related to implementation of mix-design performance testing is the amount and protocol for “aging” the mixture in the laboratory, ostensibly to “mimic” aging which occurs on in-service pavements. Many laboratory aging protocols have been proposed; some protocols are not practical for mix design (and potentially for QC/QA) due to, among other considerations, the excessive time spent in the oven. For many laboratory “performance” tests, prediction of actual field performance is less desirable than the ability to (relatively) rank or evaluate the cracking resistance of various laboratory mixes. This paper describes the effects of different aging protocols on the discrimination potential of the Illinois semi-circular bending test (SCB-IL/I-FIT). Three highways in Arkansas, for which field performance has been monitored since construction, are included in the study. Three long-term oven aging (LTOA) protocols are applied: NCHRP Report 871, NCAT “top-down cracking” program, and AASHTO R 30 for mechanical testing; one short-term oven aging (STOA) protocol, AASHTO R 30 for volumetric analysis, is also included. The discrimination potential resulting from the combination of each aging protocol and the cracking test is evaluated, both statistically and with an element of judgment regarding items such as practicality. Preliminary results indicate that all long-term aging protocols lead to comparable laboratory cracking performance regardless of observed field performance; this potentially allows the selection of an aging protocol based on practicality and convenience for use in routine practice.

The corresponding study analyzes and predicts the rutting behavior of asphalt concrete (AC) mixtures, using the Hamburg wheel tracking device (HWTD) and the principles of Weibull distribution. Twenty AC mixtures differing on hot mix asphalt/warm mix asphalt (HMA/WMA), gradation, and different types of aggregates and binder performance grades (PGs) were studied at three different test temperatures (40, 50, and 60°C). The failure rate function given by the Weibull equation was used in order to model and predict rutting in HWTD test for the different combination of studied parameters in AC mixtures. Shape and scale parameters were defined for each mixture at different test temperatures. Linear regressions were used in order to define shape and scale parameters in function of test temperature for each of the studied mixtures parameter. A generalized Weibull failure rate equation was defined to determine rutting in function of the Weibull parameters and number of wheel passes for the different combinations of type of mixture, gradation, aggregate, and binder PG in AC mixtures. An overall good correlation was observed between the fitted model and the actual HWTD test results. Shape and scale parameters showed relationship with creeping and compaction phase.

Pavements are an important of highway transportation infrastructure that constitutes an enormous investment of public fund. A tremendous of time and money is spent now and then each year on construction of both new and existing asphalt pavement. The objective of this study is to evaluate the permanent deformation characteristics of buton rock asphalt (BRA) modified asphalt paving mixtures using dynamic creep test analysis. Dynamic creep test was conducted on unmodified and BRA modified asphalt mixture using UTM25 machine. Asphalt cement of C170 was used as the base asphalt binder for unmodified asphalt mixture and BRA modified asphalt mixtures were made by substituting the base asphalt with 10, 20, and 30% (by weight of total asphalt binder) natural binder continuing granular BRA modified binder. The granular (pellets) BRA modified binder with a diameter of 7–10 mm was produced and extracted according the Australia Standard. Results of this analysis are then compared to simplify the results of unmodified and BRA modified asphalt mixtures and the conclusions are drawn.

Improving the cracking susceptibility of the asphalt concrete (AC) layers in flexible pavement structures has become a major challenge, especially with the more frequent use of recycled materials, warm mix asphalt technologies, additives, and modified binders. Establishing a performance-based analysis methodology that incorporates cracking and rutting tests is paramount for balancing the mechanical performance of AC mixtures, especially their durability and stability, during the mix design process. This paper presents an experimental evaluation of AC mixtures with the overlay tester (OT), Hamburg wheel tracking (HWT), and indirect tension (IDT) tests. A dense-graded mix with a 12.5 mm nominal maximum aggregate size was designed and produce with five asphalt binders with different performance grade including a PG 58-28, 64-22, 70-22, 70-28, and 76-22. The PG 58-28 and 64-22 asphalt binders were also modified with 3% latex. The mechanical performance of the AC mixtures was assessed with a performance diagram formulated with the crack progression rate from the OT test, rutting resistance index from the HWT test, and tensile strength from the IDT test. Modifying AC mixtures with latex may help to improve their engineering behavior. However, test methods such as the OT, HWT, and IDT tests must be incorporated into a performance-based analysis methodology to ensure satisfactory mechanical properties of modified AC mixtures.

Cold central plant recycling (CCPR) is a pavement recycling technique where milled reclaimed asphalt pavement (RAP) from an asphalt pavement or an existing stockpile are recycled into a new pavement layer. The process has many environmental and economic benefits but often the recycling contractors producing the CCPR material and the owners of RAP are not the same companies. The use of CCPR as a pavement material could be greatly expanded if asphalt mixture contractors were able to produce a 100% (or nearly 100%) recycled material using their existing asphalt mixture plants. This study investigated the mechanical properties of a CCPR mixture produced using a bio-based rejuvenator containing an anti-strip agent in a conventional double-barrel drum asphalt plant. This mixture was produced without active fillers using a foamed asphalt recycling agent. The mechanical properties assessed included stiffness and crack susceptibility. The stiffness of the rejuvenated CCPR were found to be higher than traditional cold recycling techniques but less than that of the tested hot mix asphalt base mix at lower temperatures, but similar at higher temperatures. The rejuvenated CCPR mixture should have similar cracking performance when compared to a CCPR mixture using foam and/or emulsion plus cement as an active filler and mixed with a laboratory-scale pug mill that simulates the process from a field-scale CCPR plant.

Low-temperature cracking is one of the major distresses that asphalt pavements experience along with fatigue cracking and rutting. The low-temperature cracking arises during cold months when the temperature drops below the freezing point. As the temperature drops, thermal stress develops in the asphalt concrete (AC) layers due to the shrinkage of the materials. When the thermal stress exceeds the tensile strength of the AC, the low-temperature cracking occurs in the pavement. Since binder is the main bonding agent of the AC, at a lower temperature it needs to be flexible enough to resist the low-temperature cracking. Recently, the binder is being modified with styrene-butadiene-styrene (SBS) polymer to enhance the rutting and the fatigue performance. Though it is proven that the SBS polymer improves the rutting and the fatigue performance, the effect of SBS polymer on low-temperature performance is still unknown. To this end, this study investigates the low-temperature performance of polymer modified binders (PMBs) with different concentrations of SBS polymer. To retain consistency with the source, the SBS polymer is blended with a base (neat) binder (PG 64-22) using a high shear mixer at three different percentages: 1%, 3%, and 5%. After that, the lab produced binders are used to prepare the modified mixtures by maintaining same aggregate gradation and asphalt content. Finally, the low-temperature performances of the modified mixture samples are evaluated through thermal stress restrained specimen test (TSRST). It is found that both 3% SBS and 5% SBS PMBs show better low-temperature performance than the base binder.

Use of reclaimed asphalt pavement (RAP) in the full-depth recycling process is a cost-effective and environmentally responsible method. In this study, a non-edible oil available locally known as Polanga oil has been explored as a rejuvenator. Performance of the rejuvenated asphalt mixtures containing higher RAP content (30% to 70%) were studied. Rheological characterization of the rejuvenated binder was done with various tests such as rutting and fatigue test. Thermogravimetric analysis (TGA) was conducted used to study the thermal behaviour of the rejuvenated binder. Performance of the asphalt mixtures were assessed in terms of indirect tensile strength, moisture sensitivity, rutting, fatigue, and semi-circular bending test for low temperature cracking. The 5% dosage successfully rejuvenated the aged binder and also found to be thermostatically stable when exposed to temperature up to 230°C. Overally, the asphalt mixtures containing RAP up to 60% can be adopted without significantly affecting the performance.

The aim of the study is to evaluate the performance of hot mix asphalt (HMA) against moisture with nano-materials according to Superpave mix design procedure. In this study, bitumen is modified by silica nano-powder (SiO₂NP) and aluminum oxide (Al₂O₃) nano-particle. Nano-materials are mixed with base bitumen at contents of 0.3% and 3% by nano-silica and aluminum oxide and 0.5 and 5% nano-silica and aluminum oxide by weight of bitumen, respectively. HMA is prepared with nano-modified bitumen at optimum binder contents (OBC). Moisture susceptibility of modified HMA is evaluated according to modified Lottman test procedure. OBCs are increased by modification. HMA samples modified by 0.3% SiO₂ and 3% Al₂O₃ is determined as high resistive to moisture compared to other mixtures.

Road agencies of Bangladesh rely mostly on imported bitumen and stone aggregates for construction, maintenance, and rehabilitation of flexible pavements. Expenses for importing materials are one of the reasons for the higher construction cost in Bangladesh. The study attempts to investigate the recycling prospects of RAP in base and subbase layers in accordance with existing construction practices. RAP is collected from the roadside stockpile of Tongi-Ashulia-Zerabo-EPZ Road a national highway in Bangladesh (N302). Series of laboratory tests are performed on RAP to determine the bitumen content and physical properties of milled RAP aggregates. The study reports the laboratory test results of soaked CBR tests for the specimens prepared with 100%, 70%, 60%, and 50% RAP and remaining virgin aggregates. Since gradation affects the strength properties of aggregate, it is kept fixed for all the cases. The study finds that with 100% of RAP aggregates CBR value is 15 and observed a slight increase in CBR values when RAP is replaced with virgin aggregates. However, when RAP, and virgin aggregate combinations are treated with a binder, it shows a significant improvement in CBR values. Maximum CBR value 47 is found for 50% replacement of RAP and treated with 5% cement. However, CBR value rises to 52 if only RAP is treated with 1% bitumen.

In Europe, ceramic manufacturing produces an estimated 3 million tons per year of waste, and construction, and demolition waste (RCD) have become a problem; control agencies have issues with granting environmental licenses for the disposal of this waste, since it is not recycled or reused. In Bogotá, Colombia, 2 tons of waste are generated and at least 22 million tons are generated in the country, much more than those observed in other countries in northern Europe. Due to this, the use of ceramic recycling in asphalt mixtures was mechanically evaluated, in Spain and Colombia, using sizes similar to those used in natural aggregates, and favorable results were evidenced. Subsequently, dynamic tests were applied, such as resilient modules, confirming that the new mixtures can be a solution for the use of waste and the reduction of the costs of the bituminous mixtures, especially in certain routes, with low traffic or secondary utilities.

Carbon char is a by-product of the pyrolysis of waste tires. The use of carbon char would promote sustainability and economy. Carbon char is similar to carbon black, a potential additive for hot-mix asphalt (HMA). Previously carbon black in HMA showed the potential to reduce rutting potential, temperature susceptibility, and low-temperature cracking. The primary objective of this study was to evaluate carbon char, resulting from the pyrolysis of waste tires, in Superpave HMA. Carbon char was blended with the PG asphalt binder at various percentages (5%, 10%, 15%, and 20%). A rotational viscosity test was performed on the blend to see what percentages of carbon char by mass of asphalt binder would be workable. Five percent and 10 percent were found to be viable. Those carbon char percentages were used with a PG 58-28 binder in a Superpave HMA mix design. Modified Lottman and Hamburg wheel tracking tests were then conducted on this Superpave mixture. This paper presents those results.

Sulfur is an abundant co-product of the oil and gas production. By 2020, new regulations limiting the sulfur content in maritime fuels will increase its supply. There is a need to revisit cracking characteristics of sulfur modified asphalt concrete (AC) mixtures. The objective of this study is to evaluate the cracking resistance of sulfur extended asphalt (SEA) mixtures as compared to AC prepared with standard binders. One conventional AC and two SEA mixtures were prepared in the laboratory containing 0%, 15%, and 30% sulfur replacement by weight of the binder, respectively. The sulfur was added during the mix production in the form of pellets to mimic the procedures that can be used during plant production. The Illinois flexibility index test was used to assess the cracking susceptibility of SEA mixtures. Results obtained indicate decreasing cracking resistance with increase in sulfur addition.

Bituminous binder modification is an exercise carried out so as to improve properties of virgin bitumen. In this paper properties of asphalt binder modified by waste polythene shopping bags have been assessed. The binder was modified with varying percentages of waste polyethylene materials (1, 2, 3…..10%) by weight of the binder with 0% serving as control. Modification process was carried out by digesting waste polythene shopping bags in hot asphalt binder to obtain ten samples. Some properties of the modified binder (such as penetration, penetration index, softening point, and ductility) were evaluated for each of the modified samples as well as for the control sample. Observation showed that while penetration and ductility of the modified binder reduced, softening point increased as percentage of polymer material increased. The results showed that modification of bitumen with plastomer like polyethylene caused the binder to become more rigid and less ductile. In the case of penetration index, all the values fell within the limits of -2 and +2 stipulated for paving bituminous binder. The implication of this result is that modification of asphalt binder with plastomer will improve pavement performance especially in tropical regions with high day time temperatures.

Compaction of hot-mix asphalt (HMA) is an essential process in the construction of asphalt pavement as it is critical to the performance of the road infrastructure. The compaction process enables the asphalt mixtures to achieve stability, provide resistance to deformation (rutting) against traffic loading, reduce permeability of the layer, and improve its durability. One of the factors affecting compactability (or workability) of the HMA is its internal structure. The research work presented in this paper is aimed at investigating the influence of the internal structure of HMA based on aggregate gradation and packing characteristics on the compactability. Three coarse-graded HMA mixes were used to evaluate parameters that describe aggregate packing characteristics, including the gravel to sand ratio, gradation shape factor, as well as the traditional and revised rational Bailey ratios. HMA specimens were compacted using a Superpave gyratory compactor (SGC), and the data were analyzed to determine five parameters of HMA compactability. The HMA compactability parameters were then correlated to the aggregate packing parameters. Overall, the parameters of HMA compactability exhibited a strong correlation with the aggregate packing parameters. The outcomes of the study not only provide a better understanding of the influence of aggregate gradation and packing characteristics on HMA compactability, but also identify essential input parameters to be considered when developing models to simulate HMA compaction.

Flat and elongated particle ratio is a shape characteristic for coarse aggregates used in pavements. The ASTM D 4791 is the standard test method to determine flat and elongated coarse aggregate particles in asphalt mixes. However, this method is subjective, making it less reliable to accurate measurements. The objective of this study was to investigate three flat and elongated particles ratios (FERs): 2:1, 3:1, and 5:1 using a modern 3-D laser scanning technique and compare results with ASTM D 4791. Based on the ASTM D4791, the Superpave specification allows for a maximum of 10% coarse aggregates to have FER of 5:1 in asphalt mixes. Eight aggregate materials used for road construction in South Africa were investigated. The results indicate that three crushed stones would be rejected by the Superpave specification whereas all eight crushed stones could meet the specification based on the results from the 3-D laser scanning method.

Viscoelastic analysis of asphalt concrete pavements requires information to be collected on dynamic modulus, |E*|, and phase angle, $\varphi$. Since these are collected at only a few temperatures and frequencies, the data are typically used to construct master curves for each property, which allows the interpolation of |E*| and $\varphi$ for any temperature and frequency of interest. Several efforts have been directed at developing predictive models that allow their computation based on mix characteristics. However, to date, predictive models for |E*| have received much more attention because of their use in linear elastic based mechanistic-empirical design procedures and the greater difficulty in modeling the shape of the $\varphi$ master curve. Phase angle has typically been modeled as a function of |E*|, using a generalized form of the beta distribution, or using the 3 parameters Lorentzian equation. However, no predictive model has yet been developed with these equations. This paper presents the rationale of a 5-parameter flexible functional form for modeling the phase angle, how changes in each parameter affects its shape, and some preliminary results from two comprehensive predictive models developed using the Lorentzian and the proposed 5-parameter equations.

During the last two decades, Superpave pavements were built using mostly coarse graded mixes as opposed to fine graded mixes due to the fact that coarse mix requires less asphalt binder than a fine mix while both mixes fulfill the Superpave criteria. Recently, it was observed nationally that the Superpave mixes have poor cracking performances in general. In an effort to examine this issue, this study has investigated the fatigue performance of coarse and fine graded asphalt concrete (AC) mixes. Both fine and coarse mixes were collected from a pavement site NM14, where they were applied side-by-side to construct a 2-lane 2-mile section in each direction. They have identical performance grade binder, RAP content, and aggregate source. Mixes were compacted in the laboratory and samples were tested for dynamic modulus, and four-point bending beam fatigue (BF). The fatigue test data were analyzed by employing the viscoelastic continuum damage model (VECD). The dynamic modulus test result shows that the coarse mix has higher dynamic modulus than that of the fine mix. The beam fatigue test results reveal that coarse mix has better fatigue performance than the fine mix.

The objective of this study was to address the rheological properties of crumb rubber modified asphalt binder. Reacted and activated rubber (RAR) with different dosages were used to modify the asphalt binder. In addition, a terminal blend rubber modified binder was used as a comparison. The rotational viscosity test was performed to study the effect of crumb rubber contents on the binder’s viscosity. The multiple stress creep recovery (MSCR) test was used to evaluate the rutting resistance of the short-term aged binders. The bending beam rheometer (BBR) test was applied to evaluate the low-temperature performance of the long-term aged asphalt binders. The viscosity of RAR modified asphalt binder increased, with the addition of RAR. The MSCR tests exhibited that the addition of RAR led to an improvement of elastic properties and a decrease in viscous features of the binders. The fatigue resistance of the long-term aged binders was improved with the RAR addition. The RAR modified binder decreased the chance of thermal cracking. In general, the findings from this study showed that the rutting resistance, fatigue cracking performance, and low temperature performance of RAR modified asphalt binder were enhanced.

Polyphosphoric acid (PPA) is known to improve the rutting resistance of asphalt binders by bumping their high-temperature performance grade (PG). However, the stress sensitivity of PPA-modified binders, as an important parameter contributing to rutting, is not thoroughly studied. In the current study, multiple stress creep and recovery (MSCR) test was conducted on three types of neat asphalt binders (PG 58-28, PG 64-22, and PG 70-28), and those modified by 1.0% PPA. Binder blends were subjected to 0.1 kPa and 3.2 kPa stress levels, as well as a higher stress level of 10 kPa, to evaluate their stress sensitivity. The non-recoverable creep compliance and percent recovery values were determined at different test temperatures and the stress levels. The results indicate an increase in the percent recovery and a decrease in the non-recoverable creep compliance due to PPA modification for both non-polymer-modified and polymer-modified binders. However, the increase in the percent recovery is found to be more significant for polymer-modified binder than that for non-polymer-modified binders. It is also found that using PPA reduced the stress sensitivity of polymer-modified binders. Based on the findings of this study, it is anticipated that an increase in traffic level will increase the rutting potential of mixes containing PPA than a polymer-modified asphalt binder of the same high-temperature PG grade. The outcomes of this study are expected to help pavement engineers gain a better understanding of the effect of PPA on the mechanical properties of asphalt binders.

Since conventional binders are more temperature susceptible, they fail to provide satisfactory performance in hot climate regions. Thus, binders are now being modified with different types of polymers to improve the high temperature performance and durability of the pavement. Styrene-butadiene-styrene (SBS) is one of the most popular elastomeric polymers being used in recent years for its excellent elastic property. For better understanding and further use in different analyses, it is very important to know the effect of SBS content on the elastic response and performance of a polymer modified binder (PMB). Therefore, this study investigated the laboratory performance of the PMBs with different percentages of SBS polymer. To retain consistency with the source, the SBS polymer was blended with a base (neat) binder (PG 64-22) using a high shear mixer at three different percentages: 1%, 3%, and 5%. The performance of the neat and the PMBs are investigated through the multiple stress creep recovery (MSCR) test. Results showed that the performance of a PMB increases with SBS content. Later, the Burger model was used to evaluate the effect of SBS content on viscoelastic material parameters of the PMBs. It is found that both instantaneous modulus and viscosity increase with the SBS content.

Different modifiers [styrene-butadiene-styrene (SBS), latex, polyphosphoric acid (PPA), polyethylene (PE), crumb rubber (CR)] are used in this study to modify a neat asphalt binder (PG 64-22). A novel dynamic shear rheometer (DSR) based extensional deformation test is performed using a sentmanat extensional rheometer (SER) fixture to evaluate the modifier type, effectiveness, and ductility of the modified binders. In SER test results, first peak elongation force (F₁), is the binder’s stiffness property and second peak elongation force (F₂), indicates the type of modifier and its stiffness. In the case of all modified binders, F₁ increases which indicates that modification improves the stiffness of the original binder. Although, SBS (2%, 4%, and 6%), latex (2%, 4%, and 6%), and CR (5%, 10%, and 15%) modified binders show F₂ value, PPA (1%, 1.5%, and 2%), and PE (3.5%, 4%, 6%, and 8%) modified PG 64-22 do not show any F₂ value. This indicates that the presence of elastomers in SBS, latex and CR modified binders, and plastomers and chemical modifier in HDPE and PPA modified asphalt binder respectively. For effectiveness of the elastomeric modifiers, modified binders at similar stiffness (F₁) are evaluated by comparing the F₂ values. It is concrete that SBS is more effective modifier than other types of elastomers used in this study. Considering percent elongation of the modified binder, it can be concluded that an increase in SBS percent increases the ductility and an increase in HDPE percent decreases the ductility within the studied rates.

The mechanism that allows the mixing and placement of warm-mix asphalt (WMA) at reduced temperature are not completely answered to date. While several past studies have related reduced rotational viscosity to the reduced mixing and compaction temperatures, several others reported that the reduced viscosity does not necessarily reveal the mechanism of lowering mixing and compaction temperatures. Mixing and compaction process causes a relative motion within aggregates, where binder acts as a lubricant film between aggregates. These thoughts led the authors to propose that the frictional behavior of asphalt binder as a lubricant in binder-aggregate interaction as a possible further mechanism of improved workability of WMA. This study aims to evaluate frictional behavior for a better understanding of improved workability of WMA binder with chemical additives through tribological characterization. Different Evotherm dosages were utilized for the modification of a regular performance grade (PG) binder. The tribological test was conducted through a ball-on-three-plates apparatus assembled in a dynamic shear rheometer (DSR) at different temperatures. All the binders were primarily characterized by rotational viscosity through rotational viscometer. Test results and analysis shows that the chemical additives alter the lubricating behavior by slightly reducing the coefficient of friction, though significant differences were not observed.

Asphalt modifiers/additives are increasingly used in pavement industry. Additives are commonly used as softeners to decrease the binder performance grade (PG), while polymer modifiers are usually used for heavy traffic applications to reduce permanent deformations. Recently, rejuvenators have been used in recycled pavement applications to reduce cracking susceptibility and as retarders to moisture damage. These modifiers can be derived from crude petroleum and sometimes from a bio-based feedstock. The origin of crude binder and modifier source affects the resulting binder-modifier chemical interaction. The inherent chemical variability affects the rheological performance of modified binders. It also impacts the aging potential of these binders and thereby affecting its long-term field performance. In this study, binders modified with softeners/rejuvenators at various dosages were evaluated for their performance under long-term aging. Rheological characterization of modified binders was determined using frequency sweep, linear amplitude sweep, and low temperature performance with parameters such as Glover-Rowe, R-value, crossover frequency, ΔT_c, while the chemical characteristics were determined using Fourier transform infrared spectroscopy (FTIR), and thin layer chromatography and flame ionization detection (TLC-FID). An optimum dosage of the rejuvenator studied was recommended to maximize performance of the modified binder.

Rheological properties of asphalt binder are among the most important factors that contribute to cracking in asphalt pavements. Several laboratory tests are promoted to capture fracture tolerance of asphalt concrete. Among these, the semi-circular bend (SCB) test has been gaining popularity due to its ease of use. A laboratory experimental study was undertaken to find how the binder rheological properties correlate with the mix fracture properties when tested under SCB. A number of asphalt mixes were exposed to SCB test. In parallel, dynamic shear rheometer (DSR) tests were conducted on the corresponding binders. Asphalt mixes used in the study included virgin mixes with different binder grades, as well as mixes that included different types and contents of recycled materials and recycling agents. SCB test results were analyzed to deliver a modified version of Illinois flexibility index (I-fit) and peak load; while binders were characterized through shear modulus at intermediate temperature, high temperature performance grade, and Glover-Rowe (G-R) parameter. Results show that binder shear modulus correlate reasonably well with the mix strength and flexibility index, and there are discrepancies between G-R parameter and flexibility index.

This study aims to characterize the mechanical and microstructural properties of asphalt binders prepared with 25 and 35% of RAP contents. A base binder of pen 60/70 (PG 64-22) was used in this study. The binders were characterized by conducting performance grading, multiple stress creep recovery, and frequency sweep tests. The performance of RAP blended binders were compared with the control binder. In addition, microstructural investigation was carried out using an atomic force microscope (AFM) to evaluate the mixing and adhesion between the conventional and recycled binder. From the rheological studies, the dynamic modulus of binder increased with an increase in RAP proportion. The binder testing results showed higher rut resistance characteristics for 35% RAP binder compared to 25% RAP and control binders. In microscopic studies, as the proportion of RAP increased from 0 to 35%, the surface roughness increased and the phase contrast decreased. The results of this study would be of value to the highway authorities and contractors as they move towards adopting more RAP material in the construction of asphalt pavements.

The concept of surface free energy was utilized to assess the effect of binder aging, mineral fillers, and aggregate type on the moisture damage resistance of asphalt concrete. A known methodology was used to quantify the dry and wet adhesive bond energies between four types of asphalt mastics and two types of aggregates. Furthermore, the effect of binder aging was evaluated by testing asphalt mastics with different aging conditions: non-aged, RTFO-aged (short-term aging), and PAV-aged (long-term aging). The compatibility ratio (CR) was then quantified for each mastic-aggregate combination and used as an indicator of moisture resistance of asphalt mixtures. Results confirmed that granite aggregates are more prone to moisture damage than limestone aggregates. Furthermore, cement and lime mastics enhanced the resistance of the system to moisture damage compared to limestone filler, which resulted in higher moisture susceptibility. Finally, results also revealed that aged mastics lead to lower CR, which suggests that moisture susceptibility of asphalt mixtures increases as the pavement ages.

Application of tack coat is known to enhance the performance and durability of the pavement structure by improving the bond between pavement layers. Although the most common mechanisms for tack coat failure in pavement interlayers are shear and tensile modes, the tensile failure mode has not been thoroughly investigated. In this study, a modified version of the bitumen bond strength (BBS) test was introduced for measuring the tensile bond strength between tack coat and an asphalt surface. Also, the effects of curing, moisture, and aging on the tensile bond strength of the tack coat were studied. A cationic tack coat containing polymer was applied at its optimum application rate to the surfaces of the cylindrical asphalt samples. One set of the samples was prepared with different curing times at 25°C in dry condition as well as after moisture-conditioning. The samples of the second set were long-term aged in an oven at 85°C, simulating an in-service aging equivalent to 5 to 7 years. Samples of both sets were tested using the modified BBS test at 25°C. The findings of this study clearly exhibited the effect of curing time, moisture, and aging on the tensile bond strength of the tack coat applied to the surface of an asphalt pavement. The application of the BBS test was found to be a time- and cost-effective method for determining the tensile bond strength of the tack coats.

Two-lift concrete paving (2LCP) involves placing two layers of concrete (wet-on-wet) instead of a single homogeneous layer. The practice not only allows the use of local aggregates that might not be suitable for conventional concrete pavement but also provides opportunities for incorporating recycled materials and higher levels of supplemental cementitious materials to produce an economical and sustainable pavement. More importantly, the practice can also produce more durable concrete pavements for either airfield or highway applications through the optimization of top lift mixture design, as well as with desirable surface characteristics including improved skid resistance and reduced noise. The presentation discussed the potential technical benefits of 2LCP. While 2LCP is likely to result in increased construction costs associated with additional equipment, labor, and scheduling effort, potential savings from the use of lower-quality, less expensive concrete and aggregate in the bottom lift could be sufficient to offset the additional costs. According to cost information collected from recently constructed 2LCP projects in the United States, a case-based cost analysis was also performed to evaluate the cost-effectiveness of the 2LCP practice. Through information collected from an extensive literature review, surveys, and interviews, a summary of the benefits of 2LCP from technical and cost-effectiveness perspectives was provided to justify the implementation of the 2LCP concept.

This study reports the results of deflection testing aimed to establish appropriate performance threshold values and evaluate the effect of asphalt concrete overlays (ACOs) on measured deflections and void detection. Rehabilitation planning can be improved through timely joint repairs and detecting voids more accurately. Collected deflections were correlated with load transfer efficiencies at varying confidence intervals to select performance threshold values. Moreover, testing was performed on joints prior to and after ACO milling to evaluate its effect on measured deflections and void detection. Deflection correction factors for each load level are recommended to calibrate deflections to account for the presence of ACOs and to improve void detection analysis. Presented recommendations can improve rehabilitation planning by applying trigger values appropriate to local pavement structures and climate and by accounting for the contribution of ACOs on slab deflections and void detection analysis, without the need to mill ACOs prior to FWD testing.

Currently, per American Concrete Institute Committee 306 guidance, when placing concrete in temperatures below 40°F, the concrete must be protected. Cold weather admixture systems (CWAS) technology enables concrete to be finished and cured at 23°F. CWAS concrete incorporates a suite of admixtures that depress the freezing point and allow concrete to be poured at sub-freezing temperatures and cured without external heat sources. This document will showcase the history of CWAS concrete and illustrate its long term durability when placed in cold regions. The goal of the project was to investigate long term durability of two field sites in service. This investigation consisted of a visual inspection as well as collecting nondestructive testing data on site and collecting core samples. This technology was a breakthrough for cold regions to continue construction during cold seasons and remain as durable as control concrete poured using conventional methods.

Due to increasing traffic numbers, especially heavy goods vehicles and higher global temperatures, the road infrastructure requires more and longer maintenance measures, leading to longer non-availabilities for the road users. In the research project “HESTER” (hybrid retrofitting system for maintaining roads including the usage of novel materials), a precast concrete pavement was developed which aims for an economical and durable construction in the shortest time possible. Particularly in heavy load areas like bus stops, this approach is an extremely innovative and promising option for solving the before-mentioned problem. As part of the cooperative research project, the chair of pavement engineering at the TU Dresden and its partners investigated different ways to modify conventional concrete recipes for pavements in a first step with the aim of creating a high performance concrete that withstands higher traffic and climatic loading. For this purpose, hollow polymer microspheres and short fibre reinforcements were used. In a second step, precast concrete slabs consisting out of the most suitable and classified material were produced and investigated under realistic conditions in a large-scale test stand. Four precast slabs, bedded on a silica-resin material and having four different jointing systems respectively, enabled the examination of eight systems under high cyclic loading.

The production use of precast concrete pavements (PCPs) has come a long way over since 2001 when the first production use of PCP was made to rehabilitate the Tappan Zee tollway plazas by the New York State Thruway. Since then, the PCP technology has been gaining wider acceptance in the U.S. for rapid repair and rehabilitation of concrete pavements as well as for heavily trafficked asphalt concrete pavements and intersections. The use of PCPs can significantly reduce traffic impacts of roadway repair and reconstruction projects, particularly on heavily traveled routes. Several U.S. highway agencies have implemented the PCP technology, and other agencies have constructed demonstration projects. In the U.S., the PCP technology is being used for intermittent repairs and for continuous applications with long-life service expectations. Over the last 17 years, significant advances have been made to reliably design and construct PCP systems. This paper provides an overview of the current best practices related to PCP use in the U.S.

The production use of precast concrete pavement (PCP) has come a long way over since 2001. The technology is gaining wider acceptance in the U.S. for rapid repair and rehabilitation of concrete pavements as well as for heavily trafficked asphalt concrete pavements and intersections. Several U.S. highway agencies have implemented the PCP technology, and other agencies have constructed demonstration projects. The Strategic Highway Research Program 2 (SHRP2) Project R05 was conducted from 2008 to 2012 to develop technical information and guidelines that would encourage the rapid and successful adoption of PCP technology. In 2013, the SHRP2 Implementation Assistance Program (IAP) was implemented by the Federal Highway Administration (FHWA) to help highway agencies to deploy SHRP2-developed products. As part of the IAP, FHWA in partnership with the American Association of State Highway and Transportation Officials (AASHTO), selected several transportation agencies to receive implementation assistance awards to help offset the cost of constructing a PCP project. This paper provides details of three PCP demonstration projects constructed between 2015 and 2017 by first time users of jointed PCP.

The constituent materials of a concrete pavement have to be optimized with reference to cost effectiveness and sustainability. This paper presents a study on flexural fatigue behavior of high volume fly ash concrete (HFC) under different types of fatigue loading. The different types of fatigue loading used in the study are: constant amplitude, compound, and variable amplitude loading. Mix proportion of HFC, satisfying the strength requirement of pavement concrete, is developed having a cement replacement level of 60% with low calcium fly ash. A total number of 95 beam specimens are tested under constant amplitude fatigue loading and a total number of 24 beam specimens are tested under compound fatigue loading. The three amplitude loading is used as variable amplitude loading. A total number of 10 beam specimens are tested under variable amplitude loading. The relations between the stress level (S) and the fatigue life (N) are established from the results of constant amplitude and compound loading. The results of compound and variable amplitude loading are also used for validating the Miner’s hypothesis for cumulative fatigue damage. Probabilty analysis carried out on the pooled data of Miner’s sum values showed the normal distribution. The Miner’s hypothesis can be accepted conservatively for the thickness design of rigid pavements.

Sealant is widely used in the construction of buildings and traffic infrastructure. Expansion joint failure is a significant contributing factor to concrete pavement damage. To effectively seal expansion joints to concrete pavement, a novel shape memory polyurethane (SMPU) sealant was developed in this study. A systematic test program was implemented, including glass transition temperature determination by differential scanning calorimetry analysis, the shape memory properties after uniaxial tension programing, and shape recovery with SEM. During the shape memory cycle process, the thermal and mechanical properties were investigated for shape recovery. The results indicate that the tailored T_t of prepared SMPU can be used as the shape memory switching temperature to match its working temperature, the prepared SMPU has a satisfactory shape memory effect and the programming can improve the mechanical, the recovered SMPU shows a little molecular damage because of the programming of the SMPU. It is concluded that the synthesized SMPU with the specially tailored Tt is suitable to use as a sealant of concrete pavement joints.

The safety to our ecosystem can be assured by making use of many industrial wastes in a sustainable manner. Recycling and reutilisation of industrial waste and by-products is of high importance in cement and concrete industry. In view of rapid infrastructure growth, there is an emerging need for development of cementitious materials or fillers either to replace cement or fine aggregate for stable growth. One of such industrial wastes is secondary aluminium dross. In this paper, an attempt has been made to study the mechanical properties of concrete incorporated with secondary aluminium dross. Portland pozzolana cement has been partially replaced by secondary aluminium dross in various proportions like 5, 10, 15, and 20% to study the mechanical properties such as compressive strength, split tensile strength, flexural strength, water absorption. It is observed that up to 15% replacement of cement by secondary aluminium dross is giving better results comparable with the conventional concrete. Also, the increase in initial setting time is observed with increase in percentage replacement of aluminium dross in the concrete which can make it preferable in case of hot weather conditions wherein the concreting for the roads has to be done in an open environment. From the overall study, it can be concluded that the concrete incorporated with secondary aluminium dross can be used for making pavement quality concrete that can sustain low traffic volume or it can be considered for rural roads.

Many state highway agencies in the United States are transitioning from the 1993 AASHTO pavement design guide to the AASHTOWare Pavement ME Design (PMED) for designing new and rehabilitated pavements. PMED software allows designers to input material properties to characterize pavement layers at three levels of hierarchy from project-specific inputs from extensive laboratory test results to the default values included in the software. The software then predicts smoothness and selected pavement distresses. The primary objective of this study was to investigate the effect hierarchical levels of input concrete strength properties on jointed plain concrete pavement (JPCP) performance using the PMED software. Mixture and strength information for ten existing JPCP projects were collected. The information includes aggregate type, cement content, water to cement ratio, and 28-day Portland cement concrete (PCC) compressive strength. Standard empirical equations were used to determine PCC strength properties. Pavement sections were analyzed with these mixture and strength properties and the long-term JPCP performances were evaluated. Results show that there are no differences in faulting prediction due to change in input levels of PCC strength parameters. The international roughness index (IRI) model also did not show any sensitivity to hierarchical input levels of PCC strength parameters.

Bonded concrete overlay is a favorable maintenance method since the material properties are similar to existing concrete pavements. In Korea, the transverse tining method with excellent skid resistance has been applied to bonded concrete overlay for road safety purpose. However, transverse tining produces higher noise level about 4 to 5 dB(A) than the asphalt pavements. To achieve low noise, exposed aggregate concrete pavement (EACP) can become a surface texture in bonded concrete overlay. EACP texture consists of coarse aggregate exposed to the surface around 2 to 3 mm after the removal of cement mortar. EACPs are able to maintain the low noise. In order to apply the surface of bonded concrete overlay with exposed aggregate texture, it is necessary to provide an optimum mixture proportion that satisfies the functional performance as well as the structural performance. Therefore, this study aimed to investigate the optimum mixture design for exposed aggregate concrete overlay based on the structural performance and low noise characteristics that can be affected by cement content, coarse aggregate size, and fine aggregate percentage. The compressive and flexural strength were measured to evaluate the structural performance of exposed aggregate concrete overlay. Also, exposing number of coarse aggregate, and mean texture depth were measured for evaluation of low noise characteristics.

Pervious concrete is widely used as pavement surfaces as means to increase water infiltration for water storage or conservation purposes or to reduce surface runoff (and increase skid resistance) for roadway safety. A proper evaluation of pervious concrete pore network properties is important to ascertain the ability of the material to serve the intended purposes and X-ray computed tomography (CT) scan is one method that allows for the non-destructive evaluation of the pervious concrete specimens. Pore network structures can be derived from X-ray CT scan images through the use of segmentation algorithms. Current image processing-based segmentation algorithms, however, can yield significant errors when deriving pervious concrete pore network properties. This paper describes the use of the watershed segmentation algorithm on X-ray CT scans of pervious concrete pavement mix and evaluate essential pore network properties such as pore volume, flatness, elongation, and shape factor distributions. First, the fundamentals of the watershed segmentation algorithms are described. The paper next presents on the experimental program in testing pervious concrete mix and the use of X-ray CT scans in deriving images of the samples. The watershed algorithm of different elevation functions are then applied to derive the pore network properties and the results are presented. Finally, the advantages of this algorithm over existing image processing techniques are discussed.

Moisture ingress significantly influences the serviceability and longevity of the transportation infrastructure. Moisture intrusion can give rise to the early development of distresses by creating pumping effect in granular layers and reducing the orthogonal load bearing capacity of pavement foundations. Traditionally, the tube suction test (TST) has been used to characterize the affinity of the unbound and stabilized aggregate systems to hold and transport moisture. There are several systematic errors associated with the characterization of the moisture susceptibility of granular layers using the TST test. This was the motivation to explore alternative approaches to mitigate such anomalies and refine the laboratory mixture design process of cement treated granular soils. Therefore, several alternative moisture susceptibility tests such as submergence and back pressure saturation tests in conjunction with routine mechanical tests were incorporated in this study to identify the affinity of granular layers to hold and transport moisture. To better characterize the influence of aggregate type and mineralogy upon moisture intrusion, several virgin and reclaimed aggregate systems and subgrade materials were incorporated in this study. Based on the laboratory achieved data, the back pressure saturation tests at different durations were able to detect early onset of damage in the cement stabilized materials in an efficient and timely manner. Therefore, the back pressure saturation test can be a viable option in lieu of traditional TST to efficiently characterize the damages imparted by prolong inundation situations such as storm-related flooding during natural disasters.

Many scholars worked on utilizing byproducts materials in rigid pavements because of the increasing demand for incorporating sustainable pavement materials in construction. Ceramic is one of the materials integrated to the concrete mix as a cement alternative. Recently, it has been witnessing a debate on whether it is considered pozzolanic. In line with this trend, this study aims at first in assessing the pozzolanic activity of ceramic powder and the hybrid powder composed of ceramic and slag cement as well as assessing the flexural capacity of concrete. The adopted research program made on pastes is achieved through Frattini test (direct method) and strength activity index (indirect method) along with SEM and X-ray diffraction tests to characterize the studied pastes. Four types of pastes are considered in the experimental plan: cement paste, slag cement paste, ceramic cement paste, and a hybrid paste which consists of ceramic, slag, and cement. Lastly, the flexural capacity is made through the four combinations. The accomplished laboratory-testing program is presented, and the results will be further analyzed and discussed.

An otherwise compliant and typical Australian airport crushed rock base course material was separated into fractions and recombined to produce samples of non-fines contents. Samples were compacted at optimum moisture content and then allowed to dry back to 60% of optimum, prior to repeated load triaxial testing in both drained and undrained condition. The repeated load triaxial modulus and cumulative deformation were compared for samples prepared with fines contents ranging from 6–14%. Over this range, increasing fines content had no detrimental effect on either the modulus or deformation of the crushed rock material. Although the results are limited in terms of materials and test conditions, it was concluded that the repeated load triaxial test has potential for a more performance-based specification of airport crushed rock sources. Further research is recommended to extend these findings to other materials and to harsher test conditions.

Unbound granular materials are used as base and subbase for flexible pavements, particularly for low traffic and heavy loads. The performance of these materials are measured by accumulation of permanent deformation, which leads to pavement rutting. Prediction of rutting is very important in pavement design and for preventive maintenance programs, hence there is a strong need to develop and introduce in practice more appropriate and sound models to predict permanent deformation. This paper presents a numerical approach to predict permanent deformation of unbound granular material using an elasto-plastic approach, based on the constitutive model SANISAND, which was developed by Dafalias and Manzari. The constitutive model is compatible with the concept of critical state soil mechanics and is based on the theory of bounding surface plasticity. Simulations using the model are verified against experimental data conducted on recycled concrete aggregates for application as pavement materials. The results of the preliminary verification are promising.

The natural freezing and thawing of soils can dramatically affect the soils thermal and mechanical properties, which can have destructive effects on structures built upon those soils. Previous testing in this field has attempted to predict the frost penetration depth, based on the soil, thermal, and hydrodynamic properties. To assist with future model developments, multiple frost-susceptible soil types were tested with a variety of moisture conditions. Thermal conductivity and temperature were measured as a function of depth throughout multiple multi-day frost and thaw cycles. The radial strain and frost heave were also measured in order to identify thermal expansion. All of these were selected to provide additional information to future models, requiring multiple sources of data to improve accuracy. It was identified that moisture migration was likely the most significant factor in frost heave and frost penetration, as free water sources in porous low plasticity silt (ML) material produced the largest deformations, while there was minimal heave in other frost susceptible but minimally porous materials. The thermal conductivity was found to not increase in the same manner across all samples, but would increase in some locations in each sample, which are theorized to correspond to where the moisture was most concentrated, such as where ice formation was at its highest. All of these conclusions, along with further investigation into moisture properties, will enable better frost depth prediction and frost heave potential.

Design and analysis of drainage systems in flexible pavements require proper understanding of the pavement’s response to the ingress of water. For the sake of simplicity, investigation of adequacy of drainage systems in flexible pavements is usually carried out assuming saturated state for the foundation layers. However, several studies have confirmed that the water regime within pavement layers is controlled by unsaturated flow principles. This paper demonstrates the significance of unsaturated analysis of pavement drainage through a comparison of results from DRIP and VS2DI a finite difference software package, which consider saturated and unsaturated analyses, respectively. A typical pavement structure with edge-drain was modeled using DRIP and VS2DI. The results of sensitivity analyses indicated that DRIP may be unconservative since it generally underestimates the time-to-drain compared to the unsaturated analysis. The findings of this research suggest that using a more refined analysis tool for the design of drainage systems in pavements may be desirable.

Equilibrium moisture beneath highway pavements is a critical parameter that affects the strength and stiffness of pavement systems and controls the pavement design. The soil moisture content can be expressed in form of soil suction by means of the soil water characteristic curve (SWCC). Previous research studies have shown a correlation between soil suction and Thornthwaite’s moisture index (TMI); however, these suction correlations exhibit large variability. The paper assessed the TMI from the historical climatic data obtained from Oklahoma Mesonet weather stations data from 1994 to 2017. Two commonly used models used to calculate the TMI values from the historical climatic data and contour maps are constructed. On the basis of the field data and numerical modeling, the paper builds a relationship between equilibrium suction of subgrade soils, TMI, relative humidity, and clay content.

Using waste products as highway material is an efficient solution to the problems associated with their disposal. Approximately 52,000 tons of fly ash produced annually at Boropukuria coal-based power plant in Bangladesh require a huge disposal area and create environmental issues. In the future, it will be challenging to manage disposal sites for fly ash for a densely populated country like Bangladesh. Stabilization of problematic soils with fly ash not only improves engineering properties of soil but also provides a solution to issues of fly ash disposal. This paper reports the results of laboratory investigation carried out on expansive soil collected from Rajendrapur area stabilized with fly ash. Series of laboratory tests are carried out to find chemical composition, Atterberg’s limit, maximum dry density, optimum moisture content, soaked CBR, swelling index, unconfined compression strength. Here, 4% cement is used as an activator, and an optimum amount of fly ash is determined from laboratory tests. The effect of cement with different fly ash contents are correlated with the unconfined compressive strength and Atterberg limits of stabilized soil. The study finds that soaked CBR value of the soil improves from 1.73 to 26 after adding 6% of fly ash for 14 days of curing. Moreover, swelling index of the collected soil for 4-days soaking is found to be decreased by 47% when 6% fly ash is added. The outcome of this study will guide road engineers of Bangladesh to use fly ash for stabilizing the subgrade having swelling potential.

Lignosulfonate has been utilized mainly for the purpose of granular road dust control. The use of lignosulfonate has been limited in current soil stabilization practices, although it can be considered as an alternative soil stabilizer for improving selected soil engineering properties. In this study, homogeneously diluted lignosulfonate was mixed with two types of silty soils with the goal of improving their strength and durability. Five laboratory tests were performed on unstabilized and lignosulfonate stabilized soils, including: (1) Proctor compaction test, (2) unconfined compressive strength test, (3) freeze-thaw durability test, (4) wet-dry durability test, and (5) scanning electron microscope (SEM) analysis. The unconfined compressive strength test results demonstrated that a low dosage of lignosulfonate and water was required to improve the strength of sandy silt with gravel. Based on the outcomes from the durability tests, lignosulfonate improved wet-dry resistance for both silty soil types while also producing significant improvement in freeze-thaw durability for sandy silt with clay. The scanning electron microscope (SEM) analysis indicated that lignosulfonate was capable to create a bonding among soil particles.

In this work a soil was characterized in the laboratory and the soil stabilization with waste tire fibers analyzed. Three waste tire fiber contents were used, 1, 2, and 3% (w/w). Proctor and California bearing ratio (CBR) tests were performed. Proctor test results show that maximum bulk dry density decreased with increasing content of tire fiber waste. Stabilization with the fibers decreased the soil resistance, determined in the CBR test. Simple shear test results show an increase in the peak friction angle with increasing waste tire fiber contents. Residual friction angle did not show a clear trend, whereas cohesion tends to decrease with waste tire fiber content. It was observed the mixture of the soil with fibers is not easy and good homogeneity is hard to achieve.

High traffic volume roads present a challenge for maintenance and rehabilitation as lane interdictions are required, but also undesirable. Closing lanes for pavement rehabilitation impacts not only highway capacity, but also the road network operation, along with the user safety. To minimize these effects, applications involving foamed bitumen stabilized layers have been growing in use for the last decade in Brazil, especially because of the possibility of providing adequate rehabilitation to deteriorated pavements within a reduced time frame. This paper presents the results of the monitoring of three different sections for two high traffic volume roads in Brazil, where foam stabilization was used as the rehabilitation solution. For each of these sections, the stabilized layers were composed of different types of aggregate, ranging from reclaimed asphalt pavement, to well graded crushed stone, and crushed cement treated base. The results obtained during up to five years of pavement monitoring include series of FWD testing, backcalculation results, material characterization (mix composition, binder and active filler contents, triaxial resilient modulus tests), and pavement functional and structural performance analysis. The results obtained show that foam stabilized layers can be used as efficient solution for high level roads, minimizing lane interdiction periods while maintaining a proper structural and functional performance.

In order to use the locally available lateritic soil as a base course for pavement construction, the engineering properties of the soil need to be enhanced. Hence, the experimental investigation of the lateritic soil stabilized with the ground granulated blast furnace slag (GGBS) and combination of alkali solutions such as sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃) has been conducted. The various parameters which affect the properties of the soil like binder (GGBS) content, sodium oxide (Na₂O) dosage, silica modulus (M_s), and water to binder ratio (w/b) are considered. In the present investigation, the GGBS content of 25%, Na₂O of 6%, Ms of 0.5, and w/b of 0.25 are chosen. The Atterberg’s limits, standard and modified proctor compaction tests, unconfined compressive strength (UCS), and durability tests were conducted on the stabilized soil. The UCS of 28 days cured and stabilized samples at standard and modified proctor densities is showing 775% and 580% increase with respect to natural soil and 98% and 142% increase with respect to 0 days cured samples respectively. The chosen combination of soil mixture passes all 12 cycles of wetting and drying (WD) and freeze and thaw (FT) with weight loss of 5.2% and 1% at standard proctor density and 8% and 2.5% at modified proctor density respectively after 7 days of curing.

In this paper, the impacts of loss of support beneath a concrete pavement due to permanent deformations within the supporting foundation layer are studied using 2D finite-element (FE) modeling of a rigid slab resting on a ‘solid’ foundation system. Field testing using cyclic plate load tests were conducted on two side-by-side sections with similar subgrade involving a control section (no geogrid) aggregate base course (ABC) layer (thickness = 203.2 mm) and a geogrid stabilized ABC section (thickness = 101.6 mm). Automated cyclic plate load tests were used to determine permanent deformation (δ_p) and composite in situ resilient moduli (M_r) values of the foundation system. Field testing showed statistically significant differences between the two sections with lower δ_p in the geogrid stabilized section compared to the control section. The δ_p values measured for the two sections were used to model a void beneath the slab over a defined area (i.e. loss of support, LOS). FE analysis was performed on a jointed square pavement slab with loading applied near the joint corner for different LOS conditions beneath the slab corner. The principal stresses in the pavement layer were calculated for standard 80 kN single axle highway loading and SWL50 aircraft loading cases for different pavement thicknesses. Using the principal stresses and the stress ratio (SR), the number of load repetitions for fatigue failure were calculated. FE analysis results showed that the magnitude and the void size have significant impacts on the SR and the resulting fatigue life of the pavement layer.