Recycling of end of life concrete fines (0 - 4 mm) into silica and cement

The purpose of this work is to find a methodology in order to make possible the recycling of fines (0 - 4 mm) in the Construction and Demolition Waste (CDW) process. At the moment this fraction is a not desired by-product: it has high contaminant content, it has to be separated from the coarse fraction, because of its high water absorption which can affect the properties of the concrete. In fact, in some countries the use of fines recycled aggregates is highly restricted or even banned. This work is placed inside the European project C2CA (from Concrete to Cement and Clean Aggregates) and it has been held in the Faculty of Civil Engineering and Geosciences of the Technical University of Delft, in particular, in the laboratory of Resources And Recycling. This research proposes some procedures in order to close the loop of the entire recycling process. After the classification done by ADR (Advanced Dry Recovery) the two fractions "airknife" and "rotor" (that together constitute the fraction 0 - 4 mm) are inserted in a new machine that works at high temperatures. The temperatures analysed in this research are 600 °C and 750 °C, cause at that temperature it is supposed that the cement bounds become very weak. The final goal is "to clean" the coarse fraction (0,250 - 4 mm) from the cement still attached to the sand and try to concentrate the cement paste in the fraction 0 - 0,250 mm. This new set-up is able to dry the material in very few seconds, divide it into two fractions (the coarse one and the fine one) thanks to the air and increase the amount of fines (0 - 0,250 mm) promoting the attrition between the particles through a vibration device. The coarse fraction is then processed in a ball mill in order to improve the result and reach the final goal. Thanks to the high temperature it is possible to markedly reduce the milling time. The sand 0 - 2 mm, after being heated and milled is used to replace 100% of norm sand in mortar production. The results are very promising: the mortar made with recycled sand reaches an early strength, in fact the increment with respect to the mortar made with norm sand is 20% after three days and 7% after seven days. With this research it has been demonstrated that once the temperature is increased it is possible to obtain a clean coarse fraction (0,250 - 4 mm), free from cement paste that is concentrated in the fine fraction 0 - 0,250 mm. The milling time and the drying time can be largely reduced. The recycled sand shows better performance in terms of mechanical properties with respect to the natural one.

Magnetization exchange with water and T(1) relaxation of the downfield resonances in human brain spectra at 3.0 T

The use of water suppression for in vivo proton MR spectroscopy diminishes the signal intensities from resonances that undergo magnetization exchange with water, particularly those downfield of water. To investigate these exchangeable resonances, an inversion transfer experiment was performed using the metabolite cycling technique for non-water-suppressed MR spectroscopy from a large brain voxel in 11 healthy volunteers at 3.0 T. The exchange rates of the most prominent peaks downfield of water were found to range from 0.5 to 8.9 s(-1), while the T(1) relaxation times in absence of exchange were found to range from 175 to 525 ms. These findings may help toward the assignments of the downfield resonances and a better understanding of the sources of contrast in chemical exchange saturation transfer imaging.

Geochemical Modeling and Analysis of the Frac Water Used in the Hydraulic Fracturing of the Marcellus Formation, Pennsylvania

The hydraulic fracturing of the Marcellus Formation creates a byproduct known as frac water. Five frac water samples were collected in Bradford County, PA. Inorganic chemical analysis, field parameters analysis, alkalinity titrations, total dissolved solids(TDS), total suspended solids (TSS), biological oxygen demand (BOD), and chemical oxygen demand (COD) were conducted on each sample to characterize frac water. A database of frac water chemistry results from across the state of Pennsylvania from multiple sources was compiled in order to provide the public and research communitywith an accurate characterization of frac water. Four geochemical models were created to model the reactions between frac water and the Marcellus Formation, Purcell Limestone, and the oil field brines presumed present in the formations. The average concentrations of chloride and TDS in the five frac water samples were 1.1 �± 0.5 x 105 mg/L (5.5X average seawater) and 140,000 mg/L (4X average seawater). BOD values for frac water immediately upon flow back were over 10X greater than the BOD of typical wastewater, but decreased into the range of typical wastewater after a short period of time. The COD of frac water decreases dramatically with an increase in elapsed time from flow back, but remain considerably higher than typicalwastewater. Different alkalinity calculation methods produced a range of alkalinity values for frac water: this result is most likely due to high concentrations of aliphatic acid anions present in the samples. Laboratory analyses indicate that the frac watercomposition is quite variable depending on the companies from which the water was collected, the geology of the local area, and number of fracturing jobs in which the frac water was used, but will require more treatment than typical wastewater regardless of theprecise composition of each sample. The geochemical models created suggest that the presence of organic complexes in an oil field brine and Marcellus Formation aid in the dissolution of ions such as bariumand strontium into the solution. Although equilibration reactions between the Marcellus Formation and the slickwater account for some of the final frac water composition, the predominant control of frac water composition appears to be the ratio of the mixture between the oil field brine and slickwater. The high concentration of barium in the frac water is likely due to the abundance of barite nodules in the Purcell Limestone, and the lack of sulfate in the frac water samples is due to the reducing, anoxic conditions in the earth's subsurface that allow for the degassing of H2S(g).

Transport of Hydraulic Fracturing Water and Wastes in the Susquehanna River Basin, Pennsylvania

The development of the Marcellus Shale gas play in Pennsylvania and the northeastern United States has resulted in significant amounts of water and wastes transported by truck over roadways. This study used geographic information systems (GIS) to quantify truck travel distances via both the preferred routes (minimum distance while also favoring higher-order roads) as well as, where available, the likely actual distances for freshwater and waste transport between pertinent locations (e. g., gas wells, treatment facilities, freshwater sources). Results show that truck travel distances in the Susquehanna River Basin are greater than those used in prior life-cycle assessments of tight shale gas. When compared to likely actual transport distances, if policies were instituted to constrain truck travel to the closest destination and higher-order roads, transport mileage reductions of 40-80% could be realized. Using reasonable assumptions of current practices, greenhouse gas (GHG) emissions associated with water and waste hauling were calculated to be 70-157 MT CO2 eq per gas well. Furthermore, empty so-called backhaul trips, such as to freshwater withdrawal sites or returning from deep well injection sites, were found to increase emissions by an additional 30%, underscoring the importance of including return trips in the analysis. The results should inform future life-cycle assessments of tight shale gases in managed watersheds and help local and regional governments plan for impacts of transportation on local infrastructure. (C) 2013 American Society of Civil Engineers.

Ground Water Impact Assessment in Rural Areas of North-Eastern Part of Ukrain

Protecting ground water from pollution in the rural areas of Ukraine is a priority, particularly because the largely unconfined aquifers are used by local people for potable water supply. The most important aim of this project was to characterise the scale and impact of pollution sources on groundwater quality according to the nature of groundwater vulnerability and of the particular sources of pollution. Analysis of 50 different maps of Ukraine according to geochemical, natural and landscape features, together with field studies made it possible to identify areas with different pollution risk factors. The most harmful sources of groundwater contamination providing nitrates, petrol, heavy metals and other pollutants were identified and an integral method of groundwater quality assessment was worked out. The main sources of groundwater contamination in rural areas of Ukraine were identified and listed in order of importance. Magmedov also puts forward recommendations for improving monitoring of groundwater quality as an essential part of sustainable development in rural areas of Ukraine.

Sensitivity of Nd isotopic composition in seawater to changes in Nd sources and paleoceanographic implications

It has been argued that past changes in the sources of Nd could hamper the use of the Nd isotopic composition (ϵNd) as a proxy for past changes in the overturning of deep water masses. Here we reconsider uncertainties associated with ϵNd in seawater due to potential regional to global scale changes in the sources of Nd by applying a modeling approach. For illustrative purposes we describe rather extreme changes in the magnitude of source fluxes, their isotopic composition or both. We find that the largest effects on ϵNd result from changes in the boundary source. Considerable changes also result from variations in the magnitude or ϵNd of dust and rivers but are largely constrained to depths shallower than 1 km, except if they occur in or upstream of regions where deep water masses are formed. From these results we conclude that changes in Nd sources have the potential to affect ϵNd. However, substantial changes are required to generate large-scale changes inϵNd in deep water that are similar in magnitude to those that have been reconstructed from sediment cores or result from changes in meridional overturning circulation in model experiments. Hence, it appears that a shift in ϵNdcomparable to glacial-interglacial variations is difficult to obtain by changes in Nd sources alone, but that more subtle variations can be caused by such changes and must be interpreted with caution.

Creep and shrinkage behavior of ultra high-performance concrete under compressive loading with varying curing regimes

This Ultra High Performance Concrete research involves observing early-age creep and shrinkage under a compressive load throughout multiple thermal curing regimes. The goal was to mimic the conditions that would be expected of a precast/prestressing plant in the United States, where UHPC beams would be produced quickly to maximize a manufacturing plant’s output. The practice of steam curing green concrete to accelerate compressive strengths for early release of the prestressing tendons was utilized (140°F [60°C], 95% RH, 14 hrs), in addition to the full thermal treatment (195°F [90°C], 95% RH, 48 hrs) while the specimens were under compressive loading. Past experimental studies on creep and shrinkage characteristics of UHPC have only looked at applying a creep load after the thermal treatment had been administered to the specimens, or on ambient cured specimens. However, this research looked at mimicking current U.S. precast/prestressed plant procedures, and thus characterized the creep and shrinkage characteristics of UHPC as it is thermally treated under a compressive load. Michigan Tech has three moveable creep frames to accommodate two loading criteria per frame of 0.2f’ci and 0.6f’ci. Specimens were loaded in the creep frames and moved into a custom built curing chamber at different times, mimicking a precast plant producing several beams throughout the week and applying a thermal cure to all of the beams over the weekend. This thesis presents the effects of creep strain due to the varying curing regimes. An ambient cure regime was used as a baseline for the comparison against the varying thermal curing regimes. In all cases of thermally cured specimens, the compressive creep and shrinkage strains are accelerated to a maximum strain value, and remain consistent after the administration of the thermal cure. An average creep coefficient for specimens subjected to a thermal cure was found to be 1.12 and 0.78 for the high and low load levels, respectively. Precast/pressed plants can expect that simultaneously thermally curing UHPC elements that are produced throughout the week does not impact the post-cure creep coefficient.

Assessing drinking water quality at source and point-of-use : a case study of Koila Bamana, Mali, West Africa

Ensuring water is safe at source and point-of-use is important in areas of the world where drinking water is collected from communal supplies. This report describes a study in rural Mali to determine the appropriateness of assumptions common among development organizations that drinking water will remain safe at point-of-use if collected from a safe (improved) source. Water was collected from ten sources (borehole wells with hand pumps, and hand-dug wells) and forty-five households using water from each source type. Water quality was evaluated seasonally (quarterly) for levels of total coliform, E.coli, and turbidity. Microbial testing was done using the 3M Petrifilm™ method. Turbidity testing was done using a turbidity tube. Microbial testing results were analyzed using statistical tests including Kruskal-Wallis, Mann Whitney, and analysis of variance. Results show that water from hand pumps did not contain total coliform or E.coli and had turbidity under 5 NTUs, whereas water from dug wells had high levels of bacteria and turbidity. However water at point-of-use (household) from hand pumps showed microbial contamination - at times being indistinguishable from households using dug wells - indicating a decline in water quality from source to point-of-use. Chemical treatment at point-of-use is suggested as an appropriate solution to eliminating any post-source contamination. Additionally, it is recommended that future work be done to modify existing water development strategies to consider water quality at point-of-use.

Infrared Thermography Enhancements for Concrete Bridge Evaluation

Infrared thermography is a well-recognized non-destructive testing technique for evaluating concrete bridge elements such as bridge decks and piers. However, overcoming some obstacles and limitations are necessary to be able to add this invaluable technique to the bridge inspector's tool box. Infrared thermography is based on collecting radiant temperature and presenting the results as a thermal infrared image. Two methods considered in conducting an infrared thermography test include passive and active. The source of heat is the main difference between these two approaches of infrared thermography testing. Solar energy and ambient temperature change are the main heat sources in conducting a passive infrared thermography test, while active infrared thermography involves generating a temperature gradient using an external source of heat other than sun. Passive infrared thermography testing was conducted on three concrete bridge decks in Michigan. Ground truth information was gathered through coring several locations on each bridge deck to validate the results obtained from the passive infrared thermography test. Challenges associated with data collection and processing using passive infrared thermography are discussed and provide additional evidence to confirm that passive infrared thermography is a promising remote sensing tool for bridge inspections. To improve the capabilities of the infrared thermography technique for evaluation of the underside of bridge decks and bridge girders, an active infrared thermography technique using the surface heating method was developed in the laboratory on five concrete slabs with simulated delaminations. Results from this study demonstrated that active infrared thermography not only eliminates some limitations associated with passive infrared thermography, but also provides information regarding the depth of the delaminations. Active infrared thermography was conducted on a segment of an out-of-service prestressed box beam and cores were extracted from several locations on the beam to validate the results. This study confirms the feasibility of the application of active infrared thermography on concrete bridges and of estimating the size and depth of delaminations. From the results gathered in this dissertation, it was established that applying both passive and active thermography can provide transportation agencies with qualitative and quantitative measures for efficient maintenance and repair decision-making.

MATURE FINE TAILINGS (MFTs): A STUDY OF COMPRESSIVE STRENGTH AND RHEOLOGICAL PROPERTIES OF ATHABASCA OIL SANDS PETROLEUM MINING WASTE APPLIED IN CONCRETE MIXTURES

This study investigates the compressive properties of concrete incorporating Mature Fine Tailings (MFTs) waste stream from a tar sands mining operation. The objectives of this study are to investigate material properties of the MFT material itself, as well as establish general feasibility of the utilization of MFT material in concrete mixtures through empirical data and visual observations. Investigations undertaken in this study consist of moisture content, materials finer than No. 200 sieve, Atterburg Limits as well as visual observations performed on MFT material as obtained. Control concrete mixtures as well as MFT replacement mixture designs (% by wt. of water) were guided by properties of the MFT material that were experimentally established. The experimental design consists of compression testing of 4”-diameter concrete cylinders of a control mixture, 30% MFT, 50% MFT and 70% MFT replacement mixtures with air-entrainer additive, as well as a control mixture and 30% MFT replacement mixture with no air-entrainer. A total of 6 mixtures (2 control mixtures, 4 replacement mixtures) moist-cured in lime water after 24 hours initial curing were tested for ultimate compressive strength at 7 days and 28 days in accordance to ASTM C39. The test results of fresh concrete material show that the addition of air-entrainer to the control mixture increases slump from 4” to 5.5”. However, the use of MFT material in concrete mixtures significantly decreases slump as compared to controls. All MFT replacement mixtures (30%, 50%, and 70%) with air-entrainer present slumps of 1”. 30% MFT with no air-entrainer presents a slump of 1.5”. It was found that 7-day ultimate compressive stress was not a good predictor of 28-day ultimate compressive stress. 28-day results indicate that the use of MFT material in concrete with air-entrainer decreases ultimate compressive stress for 30%, 50% and 70% MFT replacement amounts by 14.2%, 17.3% and 25.1% respectively.

Ethanol Production from Hardboard Manufacturing Process Wastewater: Methods for Improving Product Yields from Hemicellulose Hydrolysates

Waste effluents from the forest products industry are sources of lignocellulosic biomass that can be converted to ethanol by yeast after pretreatment. However, the challenge of improving ethanol yields from a mixed pentose and hexose fermentation of a potentially inhibitory hydrolysate still remains. Hardboard manufacturing process wastewater (HPW) was evaluated at a potential feedstream for lignocellulosic ethanol production by native xylose-fermenting yeast. After screening of xylose-fermenting yeasts, Scheffersomyces stipitis CBS 6054 was selected as the ideal organism for conversion of the HPW hydrolysate material. The individual and synergistic effects of inhibitory compounds present in the hydrolysate were evaluated using response surface methodology. It was concluded that organic acids have an additive negative effect on fermentations. Fermentation conditions were also optimized in terms of aeration and pH. Methods for improving productivity and achieving higher ethanol yields were investigated. Adaptation to the conditions present in the hydrolysate through repeated cell sub-culturing was used. The objectives of this present study were to adapt S. stipitis CBS6054 to a dilute-acid pretreated lignocellulosic containing waste stream; compare the physiological, metabolic, and proteomic profiles of the adapted strain to its parent; quantify changes in protein expression/regulation, metabolite abundance, and enzyme activity; and determine the biochemical and molecular mechanism of adaptation. The adapted culture showed improvement in both substrate utilization and ethanol yields compared to the unadapted parent strain. The adapted strain also represented a growth phenotype compared to its unadapted parent based on its physiological and proteomic profiles. Several potential targets that could be responsible for strain improvement were identified. These targets could have implications for metabolic engineering of strains for improved ethanol production from lignocellulosic feedstocks. Although this work focuses specifically on the conversion of HPW to ethanol, the methods developed can be used for any feedstock/product systems that employ a microbial conversion step. The benefit of this research is that the organisms will the optimized for a company's specific system.

IMPROVING FLOW DISTRIBUTION IN SMALL-SCALE WATER-SUPPLY SYSTEMS THROUGH THE USE OF FLOW-REDUCING DISCS AND METHODS FOR ANALYZING THE EFFECTIVENESS OF SOLAR POWERED PUMPING FOR A DRINKING WATER SUPPLY IN RURAL PANAMA

As continued global funding and coordination are allocated toward the improvement of access to safe sources of drinking water, alternative solutions may be necessary to expand implementation to remote communities. This report evaluates two technologies used in a small water distribution system in a mountainous region of Panama; solar powered pumping and flow-reducing discs. The two parts of the system function independently, but were both chosen for their ability to mitigate unique issues in the community. The design program NeatWork and flow-reducing discs were evaluated because they are tools taught to Peace Corps Volunteers in Panama. Even when ample water is available, mountainous terrains affect the pressure available throughout a water distribution system. Since the static head in the system only varies with the height of water in the tank, frictional losses from pipes and fittings must be exploited to balance out the inequalities caused by the uneven terrain. Reducing the maximum allowable flow to connections through the installation of flow-reducing discs can help to retain enough residual pressure in the main distribution lines to provide reliable service to all connections. NeatWork was calibrated to measured flow rates by changing the orifice coefficient (θ), resulting in a value of 0.68, which is 10-15% higher than typical values for manufactured flow-reducing discs. NeatWork was used to model various system configurations to determine if a single-sized flow-reducing disc could provide equitable flow rates throughout an entire system. There is a strong correlation between the optimum single-sized flow- reducing disc and the average elevation change throughout a water distribution system; the larger the elevation change across the system, the smaller the recommended uniform orifice size. Renewable energy can jump the infrastructure gap and provide basic services at a fraction of the cost and time required to install transmission lines. Methods for the assessment of solar powered pumping systems as a means for rural water supply are presented and assessed. It was determined that manufacturer provided product specifications can be used to appropriately design a solar pumping system, but care must be taken to ensure that sufficient water can be provided to the system despite variations in solar intensity.

Screening Swiss water bodies for potentially pathogenic free-living amoebae

Free-ling amoebae (FLA) including Acanthamoeba spp., Naegleria fowleri, Balamuthia mandrillaris and Sappinia pedata, can cause opportunistic infections leading to severe brain pathologies. Human infections with pathogenic FLA have been increasingly documented in many countries. In Switzerland, thus far, the occurrence and distribution of potentially pathogenic FLA has not been investigated. Swiss water biotopes, including swimming pools, lakes, rivers and ponds, have now been screened for the presence of FLA, and assessment of their pathogenicity potential for a mammalian host has been undertaken. Thus, a total of 17 isolates were recovered by in vitro cultivation from these different aquatic sources. Characterization by sequence analysis of Acanthamoeba spp.-specific and 'FLA-specific PCR products amplified from 18s rDNA based on morphological traits, thermotolerance, and cytotoxicity towards murine fibroblasts yielded the following findings: Echinamoeba cf. exundans (3 isolates), Hartmannella spp. (3), Vannella spp. (4), Protacanthamoebica cf. bohemica (1), Acanthamoeba cf. castellanii (1) and Naegleria spp. (5). B. mandrillaris and N. fowleri did not range amongst these isolates. None of the isolates exhibited pronounced cytotoxicity and all failed to grow at 42 degrees C; therefore, they do not present any potential for CNS pathogenicity for humans.

Target genes for virulence assessment of Escherichia coli isolates from water, food and the environment

The widespread species Escherichia coli includes a broad variety of different types, ranging from highly pathogenic strains causing worldwide outbreaks of severe disease to avirulent isolates which are part of the normal intestinal flora or which are well characterized and safe laboratory strains. The pathogenicity of a given E. coli strain is mainly determined by specific virulence factors which include adhesins, invasins, toxins and capsule. They are often organized in large genetic blocks either on the chromosome ('pathogenicity islands'), on large plasmids or on phages and can be transmitted horizontally between strains. In this review we summarize the current knowledge of the virulence attributes which determine the pathogenic potential of E. coli strains and the methodology available to assess the virulence of E. coli isolates. We also focus on a recently developed procedure based on a broad-range detection system for E. coli-specific virulence genes that makes it possible to determine the potential pathogenicity and its nature in E. coli strains from various sources. This makes it possible to determine the pathotype of E. coli strains in medical diagnostics, to assess the virulence and health risks of E. coli contaminating water, food and the environment and to study potential reservoirs of virulence genes which might contribute to the emergence of new forms of pathogenic E. coli.