Saskatchewan Highways and Transportation (SDHT) rely on dense-graded hot mix asphalt concrete mixes for construction and rehabilitation of asphalt pavement surfaced highways. As a result of increased commercial truck traffic on the provincial road network, over the last two decades, some of Saskatchewans recently placed dense graded hot mix asphalt concrete (HMAC) pavements have been observed to show a susceptibility to premature permanent deformation in the asphalt mix. One of the aggregate properties thought to have significant influence on mix performance under traffic loading is the shape of the aggregate. Specifically, the physical properties of the fine aggregate (smaller than 5 mm in diameter) are of particular importance in dense graded mixes. Although empirical evidence suggests that there are performance benefits associated with using angular fine aggregate, the relationship of this parameter on mechanistic mix performance and resistance to permanent deformation has not yet been clearly defined.<p>The primary objective of this research was to conduct laboratory analysis to determine the physical, empirical, and mechanistic behaviour sensitivity to the proportion of manufactured and natural fine aggregate in SDHT Type 72 hot mix asphalt concrete. The second objective of this research was to compare the mechanistic behaviour of the Type 72 mixes considered in this research to conventional SDHT Type 70 structural hot mix asphalt concrete.<p>Physical and mechanistic properties of a SDHT Type 72 mix at levels of 20, 40, and 60 percent manufactured fines as a portion of total fines (smaller than 5 mm), and for a SDHT Type 70 mix (which contained 38 percent manufactured fines) were evaluated. Ten repeat samples were compacted for each mix using 75-blow Marshall compaction, and ten samples for each mix were compacted using the Superpave gyratory compaction protocols. Marshall stability and flow testing was conducted on the Marshall-compacted samples. Triaxial frequency sweep testing was conducted on the gyratory-compacted samples using the Rapid Triaxial Tester (RaTT) at 20°C. The testing was conducted at axial loading frequencies of 10 and 0.5 Hz, and at deviatoric stress states of 370, 425, and 500 kPa, respectively. The resulting dynamic modulus, axial and radial microstrains, Poissons ratio, and phase angle were evaluated.<p>The research hypothesis stated that the increased amount of manufactured fines improves mechanistic properties of the Type 72 mix under typical field state conditions, and Type 72 mix with increased manufactured fines can exhibit mechanistic properties equivalent to or exceeding those of a typical type 70 mix. <p>Based on the improved densification properties, increased Marshall stability, increased dynamic modulus, and reduced radial and axial strains, it was demonstrated that increasing manufactured fines content in the SDHT Type 72 mix does improve the mechanistic properties of this dense-graded asphalt mix. It should be noted that there appears to be a minimum level of manufactured fines content that is required to affect mix response to loading, and that this threshold lies somewhere between 40 and 60 percent manufactured fines content for the Type 72 mix tested as part of this research.<p>Further, the Type 72 mix exhibited comparable or improved mechanistic properties relative to the Type 70 mix, which SDHT consider a structural mix. This is illustrated by the Type 72 mix with 60 percent manufactured fines resulting in higher Marshall stability and dynamic modulus, and lower axial microstrains than the Type 70 mix evaluated in this study.<p>It is recommended that other Type 72 and Type 70 mixes are evaluated using similar testing protocols. In addition, field test sections should be used to further verify the research hypothesis investigated here. <p>Economic analysis indicates that substantial savings in life cycle costs of SHDT asphalt concrete surfaced roadways can be realized by engineering well-performing, rut-resistant mixes. The life cycle costs can be reduced annually by approximately $7.4 million, which translates into $102.5 million savings over 18 years, during which the entire pavement network would be resurfaced with well-performing asphalt concrete mixes.<p>Further, enhanced crushing of smaller aggregate top size decreases the amount of rejected material, and increases manufactured fines to coarse aggregate ratio, resulting not only in better engineering properties, but also in the optimized use of the provinces diminishing gravel resources. Pressures on aggregate sources are also reduced by improving life cycle performance of Saskatchewan asphalt concrete pavements. The total potential aggregate savings that can be realized by implementing well-performing Type 72 HMAC mixes amount to 4.3 million metric tonnes of aggregate in the next 42 years. These aggregate savings can help decrease the predicted shortage of aggregate between 2007 and 2049 by approximately 6 percent. The total potential cost savings after 18 years of paving 500 km per year with rut-resistant, well-performing HMAC mixes amount to $112.4 million in present value dollars. The 42 year savings amount to $193.7 million in present day dollars. It is recommended that a more detailed economic analysis be carried out.

Saskatchewan Highways and Transportation (SDHT) rely on dense-graded hot mix asphalt concrete mixes for construction and rehabilitation of asphalt pavement surfaced highways. As a result of increased commercial truck traffic on the provincial road network, over the last two decades, some of Saskatchewans recently placed dense graded hot mix asphalt concrete (HMAC) pavements have been observed to show a susceptibility to premature permanent deformation in the asphalt mix. One of the aggregate properties thought to have significant influence on mix performance under traffic loading is the shape of the aggregate. Specifically, the physical properties of the fine aggregate (smaller than 5 mm in diameter) are of particular importance in dense graded mixes. Although empirical evidence suggests that there are performance benefits associated with using angular fine aggregate, the relationship of this parameter on mechanistic mix performance and resistance to permanent deformation has not yet been clearly defined.<p>The primary objective of this research was to conduct laboratory analysis to determine the physical, empirical, and mechanistic behaviour sensitivity to the proportion of manufactured and natural fine aggregate in SDHT Type 72 hot mix asphalt concrete. The second objective of this research was to compare the mechanistic behaviour of the Type 72 mixes considered in this research to conventional SDHT Type 70 structural hot mix asphalt concrete.<p>Physical and mechanistic properties of a SDHT Type 72 mix at levels of 20, 40, and 60 percent manufactured fines as a portion of total fines (smaller than 5 mm), and for a SDHT Type 70 mix (which contained 38 percent manufactured fines) were evaluated. Ten repeat samples were compacted for each mix using 75-blow Marshall compaction, and ten samples for each mix were compacted using the Superpave gyratory compaction protocols. Marshall stability and flow testing was conducted on the Marshall-compacted samples. Triaxial frequency sweep testing was conducted on the gyratory-compacted samples using the Rapid Triaxial Tester (RaTT) at 20°C. The testing was conducted at axial loading frequencies of 10 and 0.5 Hz, and at deviatoric stress states of 370, 425, and 500 kPa, respectively. The resulting dynamic modulus, axial and radial microstrains, Poissons ratio, and phase angle were evaluated.<p>The research hypothesis stated that the increased amount of manufactured fines improves mechanistic properties of the Type 72 mix under typical field state conditions, and Type 72 mix with increased manufactured fines can exhibit mechanistic properties equivalent to or exceeding those of a typical type 70 mix. <p>Based on the improved densification properties, increased Marshall stability, increased dynamic modulus, and reduced radial and axial strains, it was demonstrated that increasing manufactured fines content in the SDHT Type 72 mix does improve the mechanistic properties of this dense-graded asphalt mix. It should be noted that there appears to be a minimum level of manufactured fines content that is required to affect mix response to loading, and that this threshold lies somewhere between 40 and 60 percent manufactured fines content for the Type 72 mix tested as part of this research.<p>Further, the Type 72 mix exhibited comparable or improved mechanistic properties relative to the Type 70 mix, which SDHT consider a structural mix. This is illustrated by the Type 72 mix with 60 percent manufactured fines resulting in higher Marshall stability and dynamic modulus, and lower axial microstrains than the Type 70 mix evaluated in this study.<p>It is recommended that other Type 72 and Type 70 mixes are evaluated using similar testing protocols. In addition, field test sections should be used to further verify the research hypothesis investigated here. <p>Economic analysis indicates that substantial savings in life cycle costs of SHDT asphalt concrete surfaced roadways can be realized by engineering well-performing, rut-resistant mixes. The life cycle costs can be reduced annually by approximately $7.4 million, which translates into $102.5 million savings over 18 years, during which the entire pavement network would be resurfaced with well-performing asphalt concrete mixes.<p>Further, enhanced crushing of smaller aggregate top size decreases the amount of rejected material, and increases manufactured fines to coarse aggregate ratio, resulting not only in better engineering properties, but also in the optimized use of the provinces diminishing gravel resources. Pressures on aggregate sources are also reduced by improving life cycle performance of Saskatchewan asphalt concrete pavements. The total potential aggregate savings that can be realized by implementing well-performing Type 72 HMAC mixes amount to 4.3 million metric tonnes of aggregate in the next 42 years. These aggregate savings can help decrease the predicted shortage of aggregate between 2007 and 2049 by approximately 6 percent. The total potential cost savings after 18 years of paving 500 km per year with rut-resistant, well-performing HMAC mixes amount to $112.4 million in present value dollars. The 42 year savings amount to $193.7 million in present day dollars. It is recommended that a more detailed economic analysis be carried out.

Saskatchewan Ministry of Highways and Infrastructure (MHI) is responsible for maintaining approximately 26,100 km of two lane equivalent highways network. Most highways in Saskatchewan are constructed primarily of granular materials. Granular materials serve various purposes in a pavement structure. In particular, granular materials distribute stress within the road structure and reduce the stress applied to the subgrade. Granular materials also mitigate pumping of subgrade fines into surfacing materials, as well as provide drainage for the pavement structure.<p>As a result of the rapid deterioration of roadways and the increasing highway traffic, a significant portion of the Saskatchewan highway system is in need of rehabilitation in the next couple of decades. However, increasing costs associated with road construction as well as budget constraints render many conventional rehabilitation solutions untenable in many applications. In addition, the depletion of quality aggregate also exists in many areas of Saskatchewan. Given that much of Saskatchewan granular pavement system will be in need of strengthening in the next few decades, there is a need to apply new cost-effective and aggregate-preserving pavement rehabilitation technologies such as cold in-place recycling and base strengthening.<p>The goal of this research is to improve the engineering design and performance of recycled and stabilized granular base systems under Saskatchewan field state conditions. The specific objectives of this research are to characterize the conventional laboratory behaviour, moisture sensitivity, and mechanistic behaviour of various granular base strengthening systems in the laboratory, to characterize the structural responses of various granular base strengthening systems in the field, and to evaluate the pavement thickness design and responses of various granular base pavement structures.<p>This research is based on a cold in-place recycling and base stabilization project undertaken by Saskatchewan MHI in fall 2006. Control Section (C.S.) 15-11 between km 5.0 and km 8.0 was selected as a typical thin granular pavement under primary weight loadings that required strengthening. Unstabilized granular base, cement stabilized granular base, and cement with asphalt emulsion stabilized granular base were constructed and evaluated in this research. Materials employed on C.S. 15-11 were sampled and prepared for the various laboratory tests performed in this research. Conventional tests performed included sieve analysis, Atterberg limits, sand equivalent, standard proctor compaction, and California bearing ratio strength and swell test. Advanced mechanistic and moisture sensitivity testing included indirect tensile strength, moisture capillary rise and surface conductivity, unconfined compressive strength, and rapid triaxial frequency sweep testing.<p>The cement and cement with emulsion asphalt stabilization of the granular base were found to improve the conventional, mechanical and moisture susceptibility properties of in situ C.S. 15-11 granular base materials. The cement stabilization applied on C.S. 15-11 provided a high degree of improvement relative to the cement with emulsion stabilization. The cement stabilization was found to be relatively easy to apply in construction, whereas the cement with emulsion stabilization was more difficult, particularly due to the problems associated with cold temperatures during late season construction.<p>The rapid triaxial tester (RaTT) was found to be a practical and useful apparatus to characterize the mechanistic constitutive behaviours of granular materials. The C.S. 15- 11 in situ unstabilized base was found to have the poorest mechanistic behaviour among all three granular bases on C.S. 15-11, as expected. Cement stabilization improved the mechanistic behaviour of the in situ material significantly by providing the highest mean dynamic modulus, lowest mean Poissons ratio, lowest mean radial microstrain, and the lowest mean phase angle. The cement with emulsion asphalt stabilization also provided a considerable improvement on mechanistic behaviour of C.S. 15-11 granular base materials. However, the degree of improvement was less than the cement stabilization system.<p>Non-destructive falling weight deflection measurements taken across the field test sections showed that the stabilization systems yielded a significant improvement of primary structural response profiles across the C.S. 15-11 test sections after stabilization. The cement stabilization system was found to yield the most significant structural improvements among all the test sections constructed on the C.S. 15-11. The deflection measurements taken in 2007 after hot mix asphalt paving further identified that the unstabilized system is more sensitive to the freeze-thaw effects relative to cement stabilization and cement with emulsion stabilization systems.<p> This research also showed that the Saskatchewan MHI structural design system is not applicable to the design of stabilized granular base systems. Evaluation of the thickness design for C.S. 15-11 showed the unstabilized and the cement with asphalt emulsion stabilized test section met the criterion of fatigue cracking, but failed to meet the criterion of structural rutting in MHI design system. However, the cement stabilized section met both fatigue cracking and rutting criteria. The structural evaluation revealed that mechanistic pavement response analysis and validation are necessary in the thickness design of stabilized granular systems such as C.S. 15-11, where traditional MHI design system is not applicable. This research employed finite element modeling and linear elastic pavement modeling software to determine the maximum shear stresses within granular base under typical Saskatchewan stress state conditions. The maximum shear stress values were found to locate on top of granular base courses under the applied circular loading edges ranging from 177 kPa to 254 kPa. These maximum shear stresses within the C.S. 15-11 test section granular base courses under field stress states were compared to maximum shear stresses occurring within samples measured by rapid triaxial testing performed in this research. The comparison showed that the ranges of shear stresses applied in the laboratory RaTT testing were close to shear stresses of granular bases in the field computed from modeling. Therefore, this research showed a good correlation of lab RaTT testing and field results for granular pavements.<p>In summary, this research met the objectives of mechanistically evaluating various granular base stabilization systems in Saskatchewan by means of various laboratory testing, non-destructive field testing, as well as mechanistic modeling and analysis. This research provided valuable data and showed considerable potential for improving design, construction, and QA/QC of conventional and stabilized granular base systems in Saskatchewan.

Saskatchewan Ministry of Highways and Infrastructure (MHI) is responsible for maintaining approximately 26,100 km of two lane equivalent highways network. Most highways in Saskatchewan are constructed primarily of granular materials. Granular materials serve various purposes in a pavement structure. In particular, granular materials distribute stress within the road structure and reduce the stress applied to the subgrade. Granular materials also mitigate pumping of subgrade fines into surfacing materials, as well as provide drainage for the pavement structure.<p>As a result of the rapid deterioration of roadways and the increasing highway traffic, a significant portion of the Saskatchewan highway system is in need of rehabilitation in the next couple of decades. However, increasing costs associated with road construction as well as budget constraints render many conventional rehabilitation solutions untenable in many applications. In addition, the depletion of quality aggregate also exists in many areas of Saskatchewan. Given that much of Saskatchewan granular pavement system will be in need of strengthening in the next few decades, there is a need to apply new cost-effective and aggregate-preserving pavement rehabilitation technologies such as cold in-place recycling and base strengthening.<p>The goal of this research is to improve the engineering design and performance of recycled and stabilized granular base systems under Saskatchewan field state conditions. The specific objectives of this research are to characterize the conventional laboratory behaviour, moisture sensitivity, and mechanistic behaviour of various granular base strengthening systems in the laboratory, to characterize the structural responses of various granular base strengthening systems in the field, and to evaluate the pavement thickness design and responses of various granular base pavement structures.<p>This research is based on a cold in-place recycling and base stabilization project undertaken by Saskatchewan MHI in fall 2006. Control Section (C.S.) 15-11 between km 5.0 and km 8.0 was selected as a typical thin granular pavement under primary weight loadings that required strengthening. Unstabilized granular base, cement stabilized granular base, and cement with asphalt emulsion stabilized granular base were constructed and evaluated in this research. Materials employed on C.S. 15-11 were sampled and prepared for the various laboratory tests performed in this research. Conventional tests performed included sieve analysis, Atterberg limits, sand equivalent, standard proctor compaction, and California bearing ratio strength and swell test. Advanced mechanistic and moisture sensitivity testing included indirect tensile strength, moisture capillary rise and surface conductivity, unconfined compressive strength, and rapid triaxial frequency sweep testing.<p>The cement and cement with emulsion asphalt stabilization of the granular base were found to improve the conventional, mechanical and moisture susceptibility properties of in situ C.S. 15-11 granular base materials. The cement stabilization applied on C.S. 15-11 provided a high degree of improvement relative to the cement with emulsion stabilization. The cement stabilization was found to be relatively easy to apply in construction, whereas the cement with emulsion stabilization was more difficult, particularly due to the problems associated with cold temperatures during late season construction.<p>The rapid triaxial tester (RaTT) was found to be a practical and useful apparatus to characterize the mechanistic constitutive behaviours of granular materials. The C.S. 15- 11 in situ unstabilized base was found to have the poorest mechanistic behaviour among all three granular bases on C.S. 15-11, as expected. Cement stabilization improved the mechanistic behaviour of the in situ material significantly by providing the highest mean dynamic modulus, lowest mean Poissons ratio, lowest mean radial microstrain, and the lowest mean phase angle. The cement with emulsion asphalt stabilization also provided a considerable improvement on mechanistic behaviour of C.S. 15-11 granular base materials. However, the degree of improvement was less than the cement stabilization system.<p>Non-destructive falling weight deflection measurements taken across the field test sections showed that the stabilization systems yielded a significant improvement of primary structural response profiles across the C.S. 15-11 test sections after stabilization. The cement stabilization system was found to yield the most significant structural improvements among all the test sections constructed on the C.S. 15-11. The deflection measurements taken in 2007 after hot mix asphalt paving further identified that the unstabilized system is more sensitive to the freeze-thaw effects relative to cement stabilization and cement with emulsion stabilization systems.<p> This research also showed that the Saskatchewan MHI structural design system is not applicable to the design of stabilized granular base systems. Evaluation of the thickness design for C.S. 15-11 showed the unstabilized and the cement with asphalt emulsion stabilized test section met the criterion of fatigue cracking, but failed to meet the criterion of structural rutting in MHI design system. However, the cement stabilized section met both fatigue cracking and rutting criteria. The structural evaluation revealed that mechanistic pavement response analysis and validation are necessary in the thickness design of stabilized granular systems such as C.S. 15-11, where traditional MHI design system is not applicable. This research employed finite element modeling and linear elastic pavement modeling software to determine the maximum shear stresses within granular base under typical Saskatchewan stress state conditions. The maximum shear stress values were found to locate on top of granular base courses under the applied circular loading edges ranging from 177 kPa to 254 kPa. These maximum shear stresses within the C.S. 15-11 test section granular base courses under field stress states were compared to maximum shear stresses occurring within samples measured by rapid triaxial testing performed in this research. The comparison showed that the ranges of shear stresses applied in the laboratory RaTT testing were close to shear stresses of granular bases in the field computed from modeling. Therefore, this research showed a good correlation of lab RaTT testing and field results for granular pavements.<p>In summary, this research met the objectives of mechanistically evaluating various granular base stabilization systems in Saskatchewan by means of various laboratory testing, non-destructive field testing, as well as mechanistic modeling and analysis. This research provided valuable data and showed considerable potential for improving design, construction, and QA/QC of conventional and stabilized granular base systems in Saskatchewan.