Instrumentation and Overall Evaluation of Perpetual and Conventional Flexible Pavement Designs

The perpetual structural pavement design is currently being explored for usage in Canada and worldwide. This thick structural design can provide many potential benefits but it also has associated costs. Cold Canadian winters and warm summers impact pavement performance and make pavement design challenging. This is further complicated by a heavy dependence on trucks to transport imports and exports. Consequently, most Canadian roads are subjected to rapid deterioration due to high fatigue stresses and rapid growth of the traffic loads. The concept of a perpetual pavement design was raised to overcome the limitation of structural capacity of the conventional pavement designs. The concept of perpetual pavement was explained and introduced in this thesis and the benefits behind the perpetual pavement construction were studied. The Ministry of Transportation of Ontario (MTO) and the Centre for Pavement and Transportation Technology (CPATT) joined their efforts in partnership with Natural Sciences and Engineering Research Council (NSERC), Ontario Hot Mix Producers Association (OHMPA), Stantec Consultant, McAsphalt and others to construct three test sections on the Highway 401. The goal was to monitor and evaluate the performance of three different pavement structural designs. Performance evaluation of test section was performed by evaluating the expected ability of pavement section to withstand the traffic loads and climate impact throughout the design life of that pavement section with minimum damage. The minimum damage is expressed as low vertical pressure on top of subgrade, low shear stresses in the surface course and low tensile strain at the bottom of asphalt layers. Perpetual pavement design with Rich Bottom Mix (RBM) layer, perpetual pavement design without RBM and a conventional pavement design were constructed and instrumented with various types of sensors. These are capable of monitoring the tensile strain in asphalt layers, vertical pressure on the subgrade surface, moisture in the subgrade material and the temperature profile in the pavement sections. The test section construction, sensor installation and preliminary modeling are all part of this thesis. Preliminary structural evaluation was performed by analyzing the three designs using a Mechanistic Empirical Pavement Design Guide (MEPDG) model representing the three pavement designs constructed on the Highway 401. In addition, the WESLEA for Windows software was used to validate the long life performance of the perpetual pavement design. Life Cycle Cost Analysis (LCCA) was also performed for the perpetual and conventional pavement designs to evaluate the cost benefits associated with pavement designs for 70 year analysis period. In addition, the perpetual Pavement design philosophy for moderate and low traffic volume roads was also examined in this research. This pavement design involved creating a complete comparison and validation of the benefits of using perpetual asphalt pavements versus the conventional pavements in all road types and traffic categories. Structural evaluation of the pavement sections in moderate and low traffic volume roads was performed. In addition, LCCA was implemented to validate the perpetual and conventional structural pavement designs in moderate and low traffic volume roads

A Structural and Economic Evaluation of Perpetual Pavements: A Canadian Perspective

Perpetual pavement design philosophy provides a long-life pavement design alternative. The ability of a pavement design to perform as long-life pavement is subjected to several technical constraints. Throughout the past 10 years, perpetual asphalt pavement designs have been under investigation in several parts of the world. The Canadian climate represents an additional challenge to the success of long-life pavement performance. This project investigated the construction and performance of three pavement test sections that were constructed on Highway 401 in Southern Ontario. The construction phase of this project was completed in 2010. The test sections were equipped with various sensors to monitor the structural performance. The test section included two perpetual pavement sections and one conventional pavement section. The two perpetual pavement designs were identical with the exception of the bottom asphalt layer, which was constructed as a Rich Bottom Mix (RBM) layer in one of the perpetual sections. The three pavement sections were evaluated from a structural point of view through the analysis of the in-situ tensile strain collected from asphalt strain gauges installed at the bottom of asphalt layers under the wheel path. In addition, asphalt material laboratory characterization was undertaken by testing asphalt samples collected during construction of the three test sections. The laboratory testing was performed at the Centre for Pavement and Transportation Technology (CPATT) at the University of Waterloo. The laboratory experimental matrix in this research included dynamic modulus testing, resilient modulus testing and Thermal Stress Restrained Specimen Testing (TSRST). The correlation between various laboratory test results and the collected in-situ tensile strain was evaluated. Several linear regression models were developed to correlate the laboratory test results and the field asphalt temperature with the in-situ tensile strain. Overall, it was found that the perpetual pavement with RBM section had the lowest tensile strain at the bottom of asphalt layers. Also, various models were developed that predict tensile strain at the bottom of asphalt layers by using laboratory test data. An economic analysis was implemented to evaluate the perpetual and conventional pavement designs including a Life Cycle Cost Analysis (LCCA). Furthermore, a sustainability assessment for both design philosophies was executed to evaluate the environmental benefits of perpetual pavement designs. The perpetual pavement designs were shown to provide many benefits over the conventional asphalt pavement designs for usage on Canadian Provincial and Interstate Highways in similar climatic zones with similar traffic loading. The advantages of perpetual pavement design philosophy are not limited to structural benefits, but also extended to economic and environmental benefits in the long term

Impact of opioid-free analgesia on pain severity and patient satisfaction after discharge from surgery: multispecialty, prospective cohort study in 25 countries

Background: Balancing opioid stewardship and the need for adequate analgesia following discharge after surgery is challenging. This study aimed to compare the outcomes for patients discharged with opioid versus opioid-free analgesia after common surgical procedures.Methods: This international, multicentre, prospective cohort study collected data from patients undergoing common acute and elective general surgical, urological, gynaecological, and orthopaedic procedures. The primary outcomes were patient-reported time in severe pain measured on a numerical analogue scale from 0 to 100% and patient-reported satisfaction with pain relief during the first week following discharge. Data were collected by in-hospital chart review and patient telephone interview 1 week after discharge.Results: The study recruited 4273 patients from 144 centres in 25 countries; 1311 patients (30.7%) were prescribed opioid analgesia at discharge. Patients reported being in severe pain for 10 (i.q.r. 1-30)% of the first week after discharge and rated satisfaction with analgesia as 90 (i.q.r. 80-100) of 100. After adjustment for confounders, opioid analgesia on discharge was independently associated with increased pain severity (risk ratio 1.52, 95% c.i. 1.31 to 1.76; P < 0.001) and re-presentation to healthcare providers owing to side-effects of medication (OR 2.38, 95% c.i. 1.36 to 4.17; P = 0.004), but not with satisfaction with analgesia (beta coefficient 0.92, 95% c.i. -1.52 to 3.36; P = 0.468) compared with opioid-free analgesia. Although opioid prescribing varied greatly between high-income and low- and middle-income countries, patient-reported outcomes did not.Conclusion: Opioid analgesia prescription on surgical discharge is associated with a higher risk of re-presentation owing to side-effects of medication and increased patient-reported pain, but not with changes in patient-reported satisfaction. Opioid-free discharge analgesia should be adopted routinely

Incorporation of the Multi-Layer Plastic Packaging in the Asphalt Binders: Physical, Thermal, Rheological, and Storage Properties Evaluation

The amount of residual Multi-layer Plastic Packaging (MPP) in Canada has greatly increased in the last two decades, which has economic and environmental consequences. MPP is primarily made up of two or more layers of Polyethylene (PE), Polyester (PET), Nylon (NY), and Metalized Polyester (METPET). While MPP has not been used as an asphalt modifier, some of the materials commonly found in MPP, such as PE and PET, have also been successfully used as asphalt modifiers. Nevertheless, a few recent studies have demonstrated the potential for reusing MPP as an asphalt modifier to improve asphalt pavement performance. Recycling post-industrial MPP instead of using raw polymers could lead to economic and environmental benefits. However, a comprehensive study to evaluate MPP as a viable asphalt additive is lacking. The main objective of this study is to evaluate the feasibility of using MPP as an asphalt modifier via the wet method, considering the physical, thermal, rheological, and storage properties of the MPP-modified binder at different MPP concentrations (2%, 4%, and 8%) in asphalt cement (PG 58–28). MPP-modified binders were evaluated using the following instruments: Differential Scanning Calorimeter (DSC), Thermogravimetric Analysis (TGA), Superpave Dynamic Shear Rheometer (DSR), Rotational Viscosity (RV), and Environmental Scanning Electron Microscopy (ESEM). Test results indicated that the incorporation of MPP has a strong potential to improve permanent deformation resistance at high temperatures. In addition, MPP shows a moderate impact on fatigue cracking performance at intermediate temperatures. Overall, in low-temperature climates, using less than 4% of MPP additives would offer higher fatigue damage resistance along with adequate permanent deformation. In high-temperature climates, higher concentrations of additives may be preferable to resist permanent deformation. Finally, MPP is a challenge for existing recycling systems, and its incorporation into asphalt applications may develop more sustainable materials that would contribute to circular economy principles

Predicting the Recovery and Nonrecoverable Compliance Behaviour of Asphalt Binders Using Artificial Neural Networks

Additives are widely used to enhance the rheological and performance properties of asphalt binder to satisfy the demands of extreme loading and climatic conditions. Meanwhile, adding to the complexity of asphalt binder behaviour that requires more time, effort, and material resources during laboratory work. The purpose of this research was to use Artificial Neural Networks (ANNs) to predict the recovery (R) and nonrecoverable compliance (Jnr) behaviour of asphalt binder based on mechanical test parameters and rheological properties of asphalt binder. A comprehensive experimental database consisting of the results of the frequency sweep and Multiple Stress Creep Recovery (MSCR) test using a dynamic shear rheometer (DSR) at five test temperatures (46 ∘C, 52 ∘C, 58 ∘C, 64 ∘C, and 70 ∘C). Prediction models for R and Jnr of asphalt binder modified with different contents of fly ash, fly ash-based geopolymer, glass powder/fly ash-based geopolymer, and styrene–butadiene styrene (SBS) were developed. The ANNs model was developed using five input parameters (temperature, frequency, storage modulus, loss modulus, and viscosity) and one hidden layer with five neurons. The results pointed out that the hybrid and 4%SBS binders achieved the highest ability to resist extremely heavy traffic and to recover the deformation with 60.1% and 85.5% at 46 ∘C, respectively, compared with the other modified asphalt binders. Excellent R-values for the total data set of 0.937, 0.997, 0.985, and 0.987 for Jnr3.2 of unaged binder, Jnr3.2 of aged binder, R3.2 of unaged binder, and R3.2 of aged binder, respectively. Therefore, the ANNs model is appropriate tool to predict the R3.2 and Jnr3.2 using unaged or aged binders at different temperatures

Rutting Behaviour of Geopolymer and Styrene Butadiene Styrene-Modified Asphalt Binder

Modifying asphalt binders is an effective method of improving the performance of asphalt pavement, such as its resistance to rutting. However, because modification changes the behaviour of binders, substantial laboratory testing is required before field application to determine the best mixtures. This research aimed to evaluate the impacts of temperature, stresses, polymer type, and modification rate on the rutting behaviour of the asphalt binder modified with fly-ash-based geopolymer (GF), styrene butadiene styrene (SBS), and a combination of SBS and GF. The rheological properties of asphalt binders were investigated using the frequency sweep test at various temperatures. Additionally, the multiple stress creep recovery test was conducted at various temperatures and stresses to calculate the non-recoverable creep compliance (Jnr) and the percent strain recovery (R). The rutting resistance of asphalt mixture was assessed using the Hamburg wheel rut test. The results revealed that the asphalt binder with 8% geopolymer (8%GF) exhibited the best response in terms of complex shear modulus (G*), rutting factor (G*/sinδ), R, and Jnr compared to the 4%GF and 12%GF at different temperatures. Another interesting finding is that GF’s use in the hybrid binder (2%SBS + 8%GF) led to a significant increase in the shear complex modulus and a decrease in the phase angle compared to the binder modified with 2%SBS. The geopolymer decreased the binder’s sensitivity to temperature for both unaged and RTFO asphalt binders. The hybrid binder would also improve strain recovery under high stress and temperatures and the ability to withstand severe traffic loads. Furthermore, there is a crucial relationship between temperature and Jnr, which could help asphalt pavement designers select suitable modifiers considering the local climate and traffic volume

Evaluating Fly Ash-Based Geopolymers as a Modifier for Asphalt Binders

Severe Canadian winter conditions and growing traffic volumes are vital factors resulting in a reduction of the service life of flexible pavements. Researchers and engineers strived to develop several additives to develop balanced asphalt mixers capable of resisting distresses that caused deterioration of flexible pavements in Canada. In this study, a critical literature review regarding the use of geopolymers and their application in construction materials is provided. Moreover, an experimental matrix of laboratory testing was conducted to study the rheological and microstructural properties of the PG 58-28 asphalt binder, with different percentages (0%, 3%, 6%, and 9%) of geopolymer. The effect of geopolymer-curing time on rheological properties was investigated. Rotational viscometer, dynamic shear rheometer (DSR), and environmental scanning electron microscopy (ESEM) imaging devices were used to compare the performance of control binder with a binder with different percentages of geopolymers. Results indicated that the increase in the geopolymer content and the curing time affect the rheological behavior of the asphalt binder by increasing its viscosity, complex shear modulus, and failure temperature. Samples with higher geopolymer percentage exhibited better performance in terms of rutting resistance. Moreover, an increase in the failure temperature of modified asphalt binder with 9% geopolymer is recorded as 8.58%, 14.2%, and 15.2% for curing times of 2, 7, and 14 days, respectively, compared with virgin asphalt. Furthermore, the nanoparticles appear to be well dispersed in the binder, and increasing the percentage of the geopolymer does not seem to affect the microstructure of the binder. Overall research conclusion is that geopolymer application resulted in a potential enhancement of some of the properties of the asphalt binder

Traffic and Climate Impacts on Rutting and Thermal Cracking in Flexible and Composite Pavements

The study presented in this paper analyzed four long-term pavement performance (LTPP) test sections located in the states of New York (NY) and California (CA). Two of them are flexible pavement sections, whereas the other two are composite pavement sections. Two levels of analysis—in-state analysis and cross-state analysis—were performed for these pavement sections to determine the impacts of traffic and climate conditions. The performance of the pavement sections was evaluated in respect of thermal cracking and rutting resistance. The in-state analysis focused on comparing the pavement sections located in the same state. The two pavement sections located in CA exhibited insignificant variation in thermal cracking, although one of them had an additional 1.5” (38 mm) dense-graded asphaltic concrete (AC) layer. On the other hand, the additional 1.5” (38 mm) AC layer resulted in a significant reduction in the rutting depth in one pavement section. The in-state analysis of the two pavement sections located in NY revealed that the 0.8” (20.4 mm) chip seal layer had significantly low resistance to thermal cracking and rutting. The cross-state analysis examined pavement sections of comparable structural capacities—two with low structural capacity, and two with high structural capacity. The performance comparison of the two pavement sections with low structural capacity revealed that the chip seal layer exhibited a significantly high rutting depth, i.e., low rutting resistance under high traffic loads in a freezing climate. On the contrary, the two pavement sections with high structural capacity showed relatively high rutting resistance in both warmer and freezing climates. Furthermore, this paper presents the pavement deterioration models for rutting and thermal cracking in the LTPP test sections. These models were developed using multiple linear regression considering the pavement service life (age), traffic load (average annual daily truck traffic, AADTT), and climate impact (freezing index, FI). The deterioration models had coefficients of determination (r2) in the range of 0.82–0.99 and standard errors varying from 0.01 to 9.92, which indicate that the models are reliable