Landfill biocovers have been proven as a green and efficient technology to mitigate landfill methane emissions. Thermal, hydraulic, mechanical and bio-chemical (THMBC) factors regulate biocover behaviour. The aim of the current study is to evaluate the geotechnical and geo-environmental response or performance of compost based biocovers under freeze-thaw conditions. A comprehensive experimental program, including tests on samples as well as biocover column experiments, has been conducted. The results demonstrate that the thermal properties (thermal conductivity and thermal diffusivity) of the biocovers change due to the FTCs. Moreover, the outcomes of the column experiments demonstrate that biocover performance remains at an acceptable level even after experiencing two FTCs despite that most of the THMBC parameters in the biocover have changed due to the impacts of the FTCs and methane injection. The findings presented in this thesis will contribute to a better understanding and design of compost biocovers in cold regions.

Thesis (Ph.D.)--Boston University / One of the more powerful and consistent tools available to nature is the phenomenon of alternate freezing and thawing. Mechanically, extraordinary pressures may be involved because of the density differential existing between the liquid wnd the solid phases of water. Physiologically, there is the availability or nonavailability of water to sustain growth. Despite this, catastrophic changes are not to be expected. On the other hand, such a powerful tool must leave its imprint in one manner or another upon the natural landscape. In most arctic and highland areas the imprint is directly discernible. In more moderate climes the imprint is indirectly applied principally as a limiting parameter within an aggregate of generally favorable conditions. The phenomenon of freeze-thaw is a climatic parameter but not a climatic element. Unlike the elements, there is a definite threshold involved; that is, 32° Fahrenheit or 0° Centigrade. At this threshold water may exist in either the liquid or solid state but by the addition or subtraction of heat it can change from one state to the other without a gain or loss in temperature. In the natural environment the terms are not quite so precise. Time for the process to take place, impurities in the water, and the variation of temperature regimes among the many nooks and crannies of the landscape point to the necessity of relaxing the temperature threshold. In this study the zone of 34° F and 28° F is used. Conditions favorable for a thaw are thought to occur when: the temperature rises through the zone and conditions favorable for a freeze when the temperature drops through this zone [TRUNCATED].

Landfill biocovers have been proven as a green and efficient technology to mitigate landfill methane emissions. Thermal, hydraulic, mechanical and bio-chemical (THMBC) factors regulate biocover behaviour. The aim of the current study is to evaluate the geotechnical and geo-environmental response or performance of compost based biocovers under freeze-thaw conditions. A comprehensive experimental program, including tests on samples as well as biocover column experiments, has been conducted. The results demonstrate that the thermal properties (thermal conductivity and thermal diffusivity) of the biocovers change due to the FTCs. Moreover, the outcomes of the column experiments demonstrate that biocover performance remains at an acceptable level even after experiencing two FTCs despite that most of the THMBC parameters in the biocover have changed due to the impacts of the FTCs and methane injection. The findings presented in this thesis will contribute to a better understanding and design of compost biocovers in cold regions.

No description available.

Segmental retaining walls (SRW), typically constructed along highways, have grown in popularity over the past decade. Manufacturers of SRW blocks have estimated the service life of a properly constructed wall to be approximately 75 years. However, there have been reports of SRW systems failing after only five years in service. Suspected causes of the SRW failures are freeze-thaw damage while exposed to deicing salts sprayed by snow plows from highways. The current standard test method used for evaluating the freeze-thaw durability of SRW blocks has several drawbacks and does not accurately replicate environmental exposure field conditions. The objective of this research is to develop and assess a new standard test method for evaluating the freeze-thaw durability of SRW blocks that obtains reproducible results and offers sufficient information on the freeze-thaw performance for SRW block manufacturers and state highway agencies (SHAs). The research completed a preliminary proof of concept test for the new freezethaw test method developed using small, commercially available SRW blocks to mitigate potential problems and establish appropriate test parameters. The testing produced results of freeze-thaw degradation that followed the same modes of failure that has been discovered during field evaluations. After the proof of concept test was completed, a series of freeze-thaw tests were conducted using sets of SHA approved and non-SHA approved SRW blocks. Three different manufacturers’ SRW blocks were evaluated. There was no significant freezethaw degradation of any of the blocks after 200 freeze-thaw cycles, so for two blocks, experiments were extended to 400 cycles using a twelve-hour freeze-thaw cycle. The modification of the test did not result in more rapid deterioration of the SRW blocks. The researchers found that the freeze-thaw durability test method developed herein is beneficial for determining the freeze-thaw performance of the lower quality specified blocks. The test method gives realistic results, which match typical deterioration modes that are common in field settings, in a timely manner. However, the test method for testing SHA quality SRW blocks takes longer times and may not be a reasonable test for such products.

Doctor of Philosophy / Civil Engineering / Kyle Riding / Pre-stressed concrete is used for manufacturing railroad ties. Air entrainment is used in concrete railroad ties to provide durability in freeze-thaw conditions commonly present in track. Vibration practices in pre-stressed concrete railroad tie plants could contribute to excessive air loss during manufacture and thus poor freeze-thaw resistance. Rheological properties of fresh concrete significantly influence the determination of how much air is lost during vibration. This research attempted to increase understanding of the effect of vibration on air bubble distribution and freeze-thaw resistance of concrete given certain compositions and rheological properties of concrete. The objective was achieved by examining the effect of different admixtures combinations, vibration parameters, and rheological properties on the air void system and freeze-thaw resistance of concrete. This research also proposed a method to measure rheological properties of concrete when vibrated and for concrete mixtures too stiff to measure using conventional rheology measurements. Results showed that delaying the initiation of vibration can cause significant air loss but does not necessarily decrease freeze-thaw performance of concrete. Results also showed that a majority of air loss occurs in the first 30 seconds of vibration. The types of admixtures used in the concrete mixture can significantly affect the air system and freeze-thaw durability of concrete; this effect was shown to be more pronounced in mixtures with low yield stress and plastic viscosity. While the peak vibration acceleration had a mild effect, the frequency and peak velocity of vibration did not seem to have a noticeable effect on the air system and freeze-thaw performance of concrete. Results also showed that rheological properties of stiff mixtures can be estimated by running the rheology test during vibration.

Master of Science / Civil Engineering / Kyle Riding / The Kansas Department of Transportation (KDOT) currently practices a six-month procedure for determining freeze-thaw durability of coarse aggregate intended for use in concrete pavement. In addition to the excessive amount of time required to conduct this procedure, the testing conditions fail to replicate the accelerated rate of concrete deterioration commonly caused by deicer salt exposure in freeze-thaw environments. An experimental study was conducted in an attempt to reduce the duration of this aggregate qualification procedure. Limestone course aggregates from different quarries were used to batch concrete specimens. These specimens were subjected to curing regimes of different durations before being exposed to repeated cycles of freezing and thawing. The effects of the curing methods on freeze-thaw durability were then investigated. Another segment of this study entailed the immersion of coarse aggregate in salt brine solution prior to concrete batching. Salt-treated and non-salt-treated specimens were subjected to two different methods of freeze-thaw cycling to determine if the presence of salt could differentiate between aggregates with high and low performance. This study found that shorter curing methods, along with adjusted performance requirements, could be used to develop a shorter aggregate qualification procedure. It also found that shorter periods of time in more severe freeze-thaw conditions produced comparable concrete durability results to those of the current test method. Salt treatment of aggregates could indicate a difference in performance of aggregates when exposed to salts in freeze-thaw conditions. It could also be useful in determining frost resistance of hardened cement paste.

Highway subsoils in cold countries are subject to increased thermal conductivity, disruption of natural moisture circulation as well as dynamic loading and application of de-icing chemicals in the winter months. In this work, the moisture mass transfer in a state of vapour flow and the de-icing chemical migration were considered during unidirectional freezing. The moisture mass transfer in a gaseous state was previously widely neglected in the exploration of frost heave. To conduct freeze-thaw cycles with increased lengths of soil samples and a modified slow freezing technique, an environmental chamber of nine samples capacity was designed. Supplying the non-saline samples with either 11 or 22 g/L sodium chloride solution signified chemical mass transport over the sample length and a significant change in temperature-moisture distribution when compared to deionised water supplied test results. The presented conceptual model with vapour mass transfer was based on the thermodynamic equilibrium of vapour density with temperature change and the phase transition to ice during thermal energy withdrawal. Compared to the widely used coupled heat-mass models, the vapour flow based model clearly explained the driving forces and presented a much easier algorithm for calculation. The de-icing chemical displacement was explained as the migration of the dissolved ions together with hygroscopic water transport, which in turn, was driven by cryosuction forces. The reduction of hydraulic conductivity during the secondary salinisation with sodium chloride was caused by chemical osmosis, which tended to equalise the solute concentration in pore water over the sample length. The research outcomes indicate a significant contribution to the future perspectives on frost heave modelling and prognosis. Further research could extend this work by inclusion of the vapour mass transfer in quantitative analysis for soil freezing. The effect of secondary salinisation should be also foreseen in the long term prognosis for highway subsoils exploitation.

Fibre reinforced polymer (FRP) materials have emerged as an innovative tool within the civil engineering community for the strengthening and rehabilitation of existing reinforced concrete structures. Research has taken place over the past decade that has demonstrated the benefits of FRPs, and it is evident that there is a need for their usage given the status of the deteriorated North American civil infrastructure. However, in order to increase confidence in the application of these materials in Canada, further information is required to fully understand their behaviour in cold climates. This thesis expands on the previous research that has taken place at Queen’s University, investigating the freeze-thaw behaviour of FRP strengthened reinforced concrete. The research program herein studies the combined effects of freeze-thaw cycling and sustained loading on the flexural performance of 45 small-scale beams strengthened with glass FRP sheets, carbon FRP sheets, or carbon FRP plates. In an attempt to attain failure of the beams due to FRP rupture, the anchorage of the beams was increased and a theoretical model was produced to select the beam design for this failure mode. The model also predicted the performance of the strengthened beams in order to determine appropriate sustained loading levels. After being subjected to 300 freeze-thaw cycles and almost 3 months of sustained loads, the beams were tested to failure. It was found that the beams subjected to combined loads encountered virtually no losses in average ultimate strength. However, the greater inconsistency of the results for these beams relative to the control beams implies that lower guaranteed strengths should be used for design in situations where these conditions are present. / Thesis (Master, Civil Engineering) -- Queen's University, 2008-02-29 14:19:29.954

In recent years, a modified method to strengthen reinforced concrete (RC) structures has emerged involving application of fibre reinforced polymers (FRPs) in the ‘near surface’ of a member. The near surface mounted (NSM) method entails placing a pre-cured FRP bar, rod, strip, or plate, along with an adhesive into a pre-cut groove or slot in the cover of a member. Advantages of the NSM technique over externally bonded (EB) systems include minimal surface preparation and installation time, the ability to anchor the FRP into an adjacent member, superior protection from mechanical and environmental damage, and superior bond properties. Although a number of laboratory studies, field applications, and experimental field projects have employed the NSM FRP strengthening technique, none of these have been performed in a climate where cold environments and freeze-thaw cycling could cause adverse effects. This thesis presents the results of an experimental program to investigate the flexural and bond performance and freeze-thaw durability of a specific NSM carbon/vinylester FRP tape strengthening system through a series of tests on strengthened slab strips and a series of pull-out bond tests. The effects of adhesive type (cementitious or epoxy) and exposure condition (room temperature, freeze-thaw, sustained load, or freeze-thaw under sustained load) are examined. The results indicate no discernable negative impacts on the performance of the grout strengthened members after exposure to freeze-thaw cycles and/or sustained load. The slab strips strengthened with epoxy adhesive displayed minor changes in ultimate load (less than three percent) after exposure to freeze-thaw cycles or a period of sustained load, while the combined effect of freeze-thaw cycles and sustained load produced an average reduction in ultimate load of eight percent. The epoxy adhesive strengthened pull-out bond tests experienced a 27% average drop in ultimate load after 150 freeze-thaw cycles. These results suggest that additional research on the combined effects of sustained load and freeze-thaw cycling are warranted, particularly for NSM strengthening applications using epoxy adhesives. / Thesis (Master, Civil Engineering) -- Queen's University, 2010-04-30 18:11:56.424