The use of soil cement as a growth medium was examined in this study. During the monitoring, green soil cement revealed diverse ecological values. The survival rates of plants in each soil conditions were higher than 80%,which was very promising. Furthermore, the survival rates dropped when the soil density reached95%, which means soil density might influence the survival rate of plant. Plant growth rates in sandy soil were higher than that in soil cement. In particular, low soil density facilitated plant growth in sandy soil, whereas density effect was not clear to plant growth performance in soil cement. Experiments were undertaken to study the soil-water characteristics of sandy soil and soil cement in field and laboratory condition. The influence of vegetation and material density on the development of negative pore water pressure (PWP) and degree of saturation (Sr) in the studied materials was investigated. The field planting experiments proved a promising survival rate of Schefflera heptaphylla in both types of materials while sandy soil promoted better growth of the seedlings than the soil cement. From the field study, PWP and Sr of sandy soil responded noticeably and promptly to natural drying and wetting cycles. However, the responses in soil cement were relatively mild. When subjected to the same drying-wetting cycles, PWP responded more slowly and to a smaller magnitude compared with that of soil cement. In addition, Sr changed little in soil cement. An increase in the density of the sandy soil promoted rapid development of negative PWP, while an opposite trend was observed for soil cement. Attempts have been made to explain the observations from the perspectives of material permeability and change in water content during a drying period in both soil types. Furthermore, in sandy soil, the development of PWP (with a measurement limit of -90 kPa) was minimally affected by the presence of vegetation, while vegetation noticeably helped the development of negative PWP in the soil cement. Bounds of the soil-water characteristic curve of the studied materials were presented based on estimates from the drying and wetting scanning curves derived from the field monitoring. A complementary laboratory study was carried out in an environmental chamber with controllable temperature and humidity. Monitoring results from the laboratory agreed well with that obtained from the field. / published_or_final_version / Civil Engineering / Master / Master of Philosophy

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My research has focused on the precipitation of iron minerals, mostly oxides and hydroxides, in aqueous systems across steep pH and Eh gradients. Unlike most work in this area, which involves loose precipitates filtered out of solutions, I have focused on precipitated aggregates and, more specifically, on those that are self-organized into dis-crete structures or patterns. This topic is actually quite narrow because such types of natu-ral material organization are rare within the geochemical realm compared with the mor-phological richness of crystals, not to mention the phantasmagoria of life.My investigation of iron-based examples has included three types of physical sys-tems: 1) growth of tubular structures around bubbles coming off a charged cathode in a free solution where convection dominates; 2) development of Liesegang patterns within gelled solutions due to reactions dominated by diffusion; and 3) formation of a cement-ing matrix within the aqueous interface between particles of silica. The third case in-volves physical characteristics of the first two in that it is primarily a tightly packed, dif-fusion-limited process, but at least initially the generation of gases can create mechani-cally driven flows through the interstitial spaces.All three systems and studies are inextricably related for both tubular ('vermi-form') structures and Liesegang patterns are commonly found in natural iron-cemented sediments such as massive laterite, ironstone deposits, and banded iron formations. They are also found on a much smaller scale within discrete 'concretions' and represent the two poles of the gradient between convection-based and diffusion-based systems. As Seilacher (2001) states concerning concretions, "the distribution and precipitation of dis-solved constituents, such iron and manganese, proceeds in two radically different mor-phospaces, which are typified by dendrites [and I would include tubes and other linear growth] on the one hand and Liesegang rings on the other." Both have been observed in my lab creations with surprising frequency and tenacity even in systems thought to be in-hibitory.

Cutter Soil Mixing (CSM) is a recently developed deep mixing technique that has grown to include the treatment of sandy and silty soils. This study seeks to investigate the influence of (i) sand-silt ratio, (ii) cement content, (iii) water content and (iv) time on the unconfined compressive strength of saturated cement-treated soil specimens. A new test device and method of specimen reconstitution were conceived in order to obtain a saturated mix of soil and cement. A comparison of results show strength increases non-linearly to decreasing total water-cement ratio, and that this trend is largely independent of sand-silt ratio. Furthermore, strength increases non-linearly with time and is independent of sand-silt ratio. Lastly, it is recommended that the strength be correlated with total water-cement ratio rather than cement content, in order to improve data reporting and provide design guidance to engineering practice.

The City of Saskatoon is responsible for maintaining approximately 1,100 km of roads including locals, collectors, arterials, and freeways. With the aged state of the road infrastructure, increasing budget constraints limit the City’s ability to maintain existing road infrastructure to an acceptable level of service and to construct new road infrastructure. The infrastructure demands related to urban growth within the City of Saskatoon have caused a shrinking aggregate supply and increasing aggregate demand. In turn, growing demand and dwindling resources for aggregate are resulting in rapid increases to road construction costs. Aggregate sources are a non-renewable resource in Saskatchewan. Therefore, road designers do not have an endless supply of quality aggregates. With limitations of the road building industry and the foreseeable economic growth projected for the City of Saskatoon, it is reasonable to expect that the unit costs of providing conventional pavement structures will continue to increase in Saskatoon. Presently, the primary conventional road building materials include well graded granular base material, subbase, crushed rock and a wearing surface of either conventional hot mix asphalt concrete (HMAC) or Portland cement concrete (PCC). To ensure long term pavement performance, quality aggregate sources are needed in all road design structural layers. Recent years have seen an increased need for substructure drainage systems, therefore increasing the need for high quality crushed rock. City of Saskatoon, like other urban centers, generates significant stock piles of concrete rubble annually. The primary objective of this research was to compare PCC material properties to those of conventional granular materials under realistic field state conditions. The second objective of this research was to validate the economic feasibility of using recycled PCC material within City of Saskatoon road structure through test section design and field test sections’ structural performance. Conventional and mechanistic material characterization was completed for recycled PCC well graded base course and recycled PCC drainage rock derived from PCC rubble, as well as conventional City granular base and drainage rock aggregates from typical City of Saskatoon stockpiles. Conventional testing completed on the samples included physical properties as required by COS aggregate specifications. Micro-Deval testing was also completed to compare the mechanical breakdown of the aggregates tested. Based on the results of the conventional tests performed, the recycled PCC well graded base and the recycled PCC drainage rock were found to meet COS base and drainage rock specifications, respectively. The recycled PCC well graded base material, recycled PCC drainage rock, COS granular base, and recycled PCC well graded base stabilized with different percentages of cement and slow setting type one (SS-1) asphalt emulsion were the research materials mechanistically tested. These materials were mechanistically tested using triaxial frequency sweep characterization to derive the mechanistic material constitutive relations across all the materials. Five repeat samples were gyratory compacted and tested at room temperature using the rapid triaxial testing. To characterize climatic durability, all the samples were moist cured for 28 days, characterized using the rapid triaxial test; then vacuum saturated and then characterized again using the rapid triaxial test. The mechanistic properties measured for the PCC material showed better climatic durability compared to those measured for the virgin aggregates, particularly after climatic durability testing. Prior to vacuum saturation, the conventional COS granular base had a peak dynamic modulus of 457 MPa. Under the same testing conditions, recycled PCC well graded base unstabilized had a stiffness of 1081 MPa; the stabilized PCC samples with two percent cement had a dynamic modulus of 1542 MPa. The radial micro strain and Poisson’s ratio were reduced for well graded PCC materials both unstabilized and stabilized compared to the conventional COS granular base. The conventional granular base had a peak radial micro strain of 194 compared to the untreated recycled PCC well graded base peak radial micro strain of 54 at the same testing parameters of low stress state at a testing frequency of 10 Hz prior to vacuum saturation. The conventional COS granular base samples failed under high deviatoric stress state at a 0.5 Hz testing frequency prior to vacuum saturation, whereas the PCC materials survived all testing frequencies and stress states. However, after vacuum saturation, the unstabilized recycled PCC well graded base samples failed under high stress state under a 10 Hz testing frequency. To validate field structural performance, two road structures within the City of Saskatoon were used as test sections in which recycled PCC drainage rock was used as a structural drainage layer. The first test section was constructed in the east bound lane of Marquis Drive, and the second was completed at the University of Saskatchewan. Prior to construction of both the Marquis Drive and North Road test sections, both sections were tested for peak surface deflections using the heavy weight deflectometer. Segment 1 of Marquis Drive had an average pre construction surface deflection of 1.85 mm under a primary weight limit. Section 1 of North Road had an average pre construction surface deflection of 1.17 mm under primary weight limit. After construction was complete on both test sections using recycled materials including a PCC drainage layer, HWD testing showed post construction peak deflections were significantly lower than the deflections measured pre construction. Recycled PCC well graded base material performed well in mechanistic laboratory analysis. However, the material was not field tested in this research. Mechanistic laboratory and field analysis indicated that recycled PCC drainage rock aggregates met structural performance requirements. The capital cost analysis showed that using recycled PCC drainage rock can reduce the overall cost of road rehabilitation projects when compared to using conventional virgin aggregates, particularly crushed drainage rock. The Marquis Drive section had a cost savings of $89,000, and the University of Saskatchewan section had a cost savings of $75,800 when recycled materials were used in lieu of virgin aggregates to rehabilitate the pavement structure. In addition, no PCC was disposed of in the landfill, saving the City of Saskatoon tipping fees and extending the life of the landfill. This research showed that the crushed PCC rubble is both technically and economically feasible to use as high quality aggregates in City of Saskatoon streets. Based on the findings of this research, the City of Saskatoon should pursue the use of recycled PCC rubble aggregates in urban road construction.

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