Colin Wandzura

Mechanistic Laboratory Evaluation and Field Construction of Recycled Concrete Materials for Use in Road Substructures

Given the renewal of urban infrastructure and the increased costs of landfilling concrete rubble materials, opportunities exist to optimize the reclamation and recycling of portland cement concrete (PCC) and hot-mix asphalt concrete (HMAC) rubble through their innovative use in road rehabilitation. The primary objective of this study was to demonstrate the ability to reclaim, process, and recycle stockpiled concrete materials to provide improved structural mechanistic–climatic material properties and to meet or exceed the mechanical properties of conventional granular road materials. This research was based on advancements made in 2009 as part of the Green Streets Infrastructure Program in the city of Saskatoon, Saskatchewan, Canada. A second objective of this research was to pilot the field application of reclaimed and recycled HMAC and PCC rubble in typical urban road reconstruction applications. Recycled HMAC and PCC materials were used in the pilot reconstruction of a road that was exhibiting substructure moisture problems and structural failure. This study showed that recycled HMAC and PCC rubble materials could be processed to achieve mechanistic laboratory properties that exceeded those of conventional granular-based materials. This study also demonstrated efficient constructability and high end-product structural asset value of a typical rehabilitated urban road structure test section in the city of Saskatoon by using recycled HMAC and PCC rubble. On the basis on these findings, the use of quality processed HMAC and PCC rubble materials for road reconstruction was found to be a technical and environmentally sustainable solution.

Triaxial frequency sweep characterization of Saskatchewan hot mix asphaltic concrete across asphalt cement binder type

The purpose of this research was to determine how asphalt cement binder types influence the mechanical behaviour of hot mix asphalt concrete mixes. This research employed triaxial frequency sweep characterization of a typical City of Saskatoon Hot Mix Type A2 and a typical Saskatchewan Ministry of Highways and Infrastructure Hot Mix Type 70 across a range of triaxial load frequencies and stress states representative of Saskatchewan field state conditions. The asphaltic mixes were evaluated across four asphalt cement binder types typically employed by Saskatchewan road agencies. Based on the findings of this study, the mechanical behaviour of both asphalt mixes evaluated were found to be highly sensitive to load rate, stress state, as well as asphaltic binder type. It was concluded that load rate, field stress state, and asphalt binder type should be incorporated into the structural design of hot mix asphalt concrete pavements to ensure adequate mix performance, particularly when placed in severe field con...

Cement Stabilization of Conventional Granular Base and Recycled Crushed Portland Cement Concrete

Challenges in finding high-quality sources of natural aggregate have led Saskatchewan, Canada, road agencies to explore alternative solutions to meet aggregate demands. The use of recycled materials, such as recycled portland cement concrete (PCC), though traditionally limited to low-quality applications such as subbase or backfill materials, shows promise as a technically viable solution that also offers economic and environmental advantages. In this study, mechanistic material testing was used to examine the effects of cement stabilization on traditional granular base and on two impact-crushed recycled PCC materials from different locations. The unstabilized PCC materials had substantially better mechanistic material properties than the unstabilized conventional granular base material; this result indicates that PCC materials could be suitable for use in high-quality applications, such as base course layers, rather than being limited to use in low-quality applications, such as utility and embankment fills. This study also showed that cement stabilization substantially improved the mechanistic properties of conventional granular base material, yet had a much less pronounced effect on the material properties of the PCC materials. This result may be attributable to poor absorption of the cement by the PCC or a lack of rehydration of the PCC. There was minimal variability in the mechanical behavior of the PCC specimens despite a difference in stockpile location. Both types of PCC material were processed and crushed with the same technique and equipment.

Integrated Mechanistic-Based Framework for Sustainable “Green Street” Rehabilitation of Urban Low-Volume Roads:

This research developed a mechanistic-based framework for recycling rubble materials into high-value-added engineered road structural materials for use in urban road rehabilitation. Scientific-based engineering methods were integrated with advanced materials processing, road construction, and nondestructive asset management techniques to explicitly quantify the benefits of recycled material systems using reclaimed asphalt pavement (RAP) and portland cement concrete (PCC) rubble generated within the city of Saskatoon, Saskatchewan, Canada. The ability to process RAP and PCC rubble to meet or exceed conventional granular aggregate specifications with minimal waste was demonstrated. It was found that RAP and PCC aggregates can exceed the mechanistic material constitutive properties of conventional city of Saskatoon granular base aggregates by at least 30%. The mechanistic material property value of unstabilized RAP and PCC was demonstrated in addition to the benefits of various cold stabilization systems using cement and emulsion. Recycled RAP was used as a black base layer and PCC was used as a subbase course or a drainage and stress-dissipation layer, or both, in rehabilitated road structures of nine “Green Street” test sections constructed in Saskatoon. These test sections met or exceeded target structural designs and were validated by using nondestructive heavy-weight deflectometer testing. The use of recycled RAP and PCC rubble materials for urban road rehabilitation had economic, social, environmental, and energy benefits for the city of Saskatoon. Recycled rubble materials were found to provide a technically viable and cost-effective solution for rehabilitating urban low-volume roads relative to conventional granular aggregates.

Mechanistic Design and Nondestructive Structural Validation of a "Green Street" Test Section Using Recycled Rubble Materials

The City of Saskatoon, Saskatchewan, Canada, commissioned the “Green Street” Infrastructure Program to investigate the potential of using recycled reclaimed asphalt pavement (RAP) and portland cement concrete (PCC) rubble as structural road layers. This study validated the mechanistic materials characterization and structural design of a field test section constructed using recycled RAP and PCC materials in addition to in situ reclaimed and recycled road materials. This paper presents a summary case study of the Green Street test section on 8th Street in Saskatoon. The rehabilitation of 8th Street consisted of two pavement rehabilitation systems: one incorporated a drainage layer and the other did not. The rehabilitation of the right-turn lane included a drainage system incorporating City of Saskatoon offsite impact-crushed PCC rubble material. The entire right-hand-turn lane and sections of the median lane and the driving lane were rehabilitated by rotomixing hot-mix asphalt concrete (HMAC) and granular base layers and adding offsite impact-crushed RAP to top up the remixed base layer. The top 200 mm of this remixed base layer was stabilized with cement–emulsion. The entire 8th Street test section was surfaced with typical City of Saskatoon HMAC. When subjected to mechanistic triaxial frequency sweep characterization, both the cement–emulsion-stabilized in situ remix material (utilized as a black base course) and the HMAC surfacing materials showed good mechanistic structural material constitutive behavior. The stabilized in situ remix material yielded end-product mechanistic material behavior that exceeded that of the HMAC surfacing.