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Master of Science / Department of Civil Engineering / Kyle Riding / Some limestone coarse aggregate in concrete pavement can break down under repeated freeze-thaw cycles. Application of rock salt may increase the severity of exposure conditions because of trace compounds, such as calcium sulfate, in rock salt. Subsequently, limestone aggregate in concrete was subjected to freeze-thaw cycling in two methods: salt-treating the aggregate before batching concrete, and half-immersing concrete specimens in rock salt solution during freeze-thaw cycling. Concrete and saw-cut limestone specimens were also subjected to wet-dry cycles in varying salt solutions to examine the influence of trace compounds in rock salt. Freeze-thaw test results indicate that the test methods used were not severe enough to determine if a limestone aggregate was durable or not. The wet-dry testing was also not severe enough to determine the effects of trace compounds in salt solution.

Master of Science / Department of Civil Engineering / Kyle Riding / Fly ash is a by-product of coal-fired power plants. This material can be used as a partial cement substitute in portland cement concrete. Use of fly ash can improve concrete durability as well as utilize an industrial by-product that would otherwise be discarded in landfills. However, research on fly ash concrete has shown that in some cases, concrete with high volumes of fly ash can have deicer salt scaling problems. Salt-scaling is the flaking of a concrete surface that when severe enough may result in lower skid resistance and service life of the concrete. In this study, concrete mixtures with six different fly ashes were tested in a laboratory using the ASTM C 672 standard. Curing compound, a wax-based coating sprayed on the fresh concrete surface to reduce evaporation, was used to compare the effects of curing on salt scaling of concrete containing high volumes of fly ash. Different variables measured were the type of fly ash, curing conditions, and total paste volume included in the mix. Results showed that curing compounds will improve the salt-scaling resistance of concrete containing a fly ash that only marginally exhibits salt scaling. However, the salt-scaling performance of concrete that contains fly ash from a source that performs poorly in ASTM C 672 is not markedly improved by using a curing compound. Additionally, results showed that salt-scaling resistance of concrete containing fly ash performs better when the total paste volume is not increased by the addition of fly ash to the mixture. The Kansas Outdoor Concrete Exposure Site (KOCE) at the Kansas State University Civil Infrastructure Systems Laboratory (CISL) was constructed to compare laboratory results to actual field conditions in the future. The site was developed based on experiences from the University of Texas-Austin outdoor exposure site and the CANMET exposure site in Ottawa, Canada. Alika silica reaction blocks were made to develop the procedure for future concrete durability testing at KOCE.

Reinforced concrete structures deteriorate throughout their lifetime. This is particularly apparent in structures subjected to aggressive environments, which results in corrosion of reinforcing steel. Designers make allowances for accelerated deterioration in these environments in an attempt to ensure the durability of the structure. To combat corrosion, improved concrete characteristics and additional concrete cover are used to increase the protection provided by concrete to reinforcing. In spite of these measures, cracking of structures in service and from natural hazards can limit the effectiveness that these measures provide. Ultimately, this results in structures suffering from corrosion, which affects their strength, stiffness, and ductility. While strength reduction can be associated directly with a reduction in bar area, impacts on stiffness and ductility are associated with more complex mechanisms, one of which is bond deterioration. A key assumption in reinforced concrete design is that there is perfect bonding between steel reinforcing and surrounding concrete to allow for strain compatibility to be assumed. Perfect bond does not exist and diminished bond performance due to corrosion deterioration further violates this assumption, the effects of which are not fully understood. This thesis investigates the effects of bond deterioration due to corrosion on the seismic performance of reinforced concrete structures. 60 monotonic and cyclic pull-out tests were undertaken on corroded reinforced concrete specimens, with corrosion levels ranging from 0% to 25% reinforcing mass loss. Additional tests were also conducted on specimens with variations in the amount of confining steel to simulate losses in confinement associated with corrosion of confining steel. Experimental results were used to develop corrosion and confinement dependent cyclic bond-slip model. The proposed bond-slip model was then used to modelling pull-out of reinforcing bars detailed in accordance with New Zealand design standard NZS3101. Analyses were performed at a range of corrosion levels, levels of confinement, and uncorroded bond strengths. These showed that pull-out of reinforcement occurred at as little as 8% corrosion in low strength, unconfined conditions. Multi-spring modelling of standard reinforced concrete columns, representing a bridge pier to foundation connection, was performed at the full range of deterioration with allowance for bond slippage. These analyses showed significant reductions in stiffness occurring with increased corrosion levels as well as reduced ductility and possible pull-out of reinforcement.

This study investigated the natural durability of 8 and 60 year old Eucalyptus bosistoana (coast grey box). The sample’s heartwood compounds were extracted with an optimised extraction process and then incorporated into agar. Trametes versicolor (white rot) and Gloeophyllum trabeum (brown rot) fungi were grown upon these agars and their growth rate was used to assess the fungicidal abilities of the extracts. The extraction method of cell wall compounds was optimised. An Accelerated Solvent Extraction system (ASE) was used with the following settings: • 2 cycles per sample • 70°C extraction temperature • 50% rinse • 5 minute static time Ethanol was found to extract the compounds of the highest fungicidal activity. Ethanol was found to extract similar amounts to water (~13% of dry weight for a 60 year old sample), however analysis of both water and ethanol extracts with a FTIR spectrometer, found that they were of different chemical composition. A difference in fungicidal activity of extracts was found between the 8 year old and 60 year old samples. There was a large difference in the percentage of extracts present between the samples as well as the type of compounds present, shown by FTIR.

Modern data centers are increasingly using shared storage solutions for ease of management. Data is cached on the client side on inexpensive and high-capacity flash devices, helping improve performance and reduce contention on the storage side. Currently, write-through caching is used because it ensures consistency and durability under client failures, but it offers poor performance for write-heavy workloads. In this work, we propose two write-back based caching policies, called write-back flush and write-back persist, that provide strong reliability guarantees, under two different client failure models. These policies rely on storage applications such as file systems and databases issuing write barriers to persist their data, because these barriers are the only reliable method for storing data durably on storage media. Our evaluation shows that these policies achieve performance close to write-back caching, while providing stronger guarantees than vanilla write-though caching.

Because of global warming the energy production development has progressed towards more renewable energy sources. Biomass has great potential in this matter and pellet is already a big market that has increased seven times the past decade. A periodically strained woodchip resource market and statements of short supply in the future has got actors exploring opportunities with other commodities. Grasses such as Canary grass has shown great potential in this matter and in this study a wetland grass is tested as an additive, 0,5, 1,0, 1,5, and 1,9%, with spruce woodchips. The test production series was performed at a production unit located at the department of environmental and energy system at Karlstad University, Karlstad. Quality was controlled accordingly to the European standard and parameters such as energy consumption, moisture content, mechanical durability and bulk density was tested. For comparison, a sample with only spruce wood chips was produced, and a sample containing 1% of a commonly used additive, potato starch. The results showed that a decrease in energy consumption with 14% when 2% wetland grass was added, part of the decline may be due to the increased production flow compared with the reference sample. The positive effects on decrease in energy consumption, that 1% potato starch results in, is equal to reults from 1% wetlandgrass. This indicates lubricating properties in wetlandgrass. This is attributed to that herbaceous plants have a high content of extracts such as waxes and that they cause less friction in the press. Tests also showed that pellet with wetland grass did not qualify the European standard in terms of mechanical durability. Extracts can form a weak boundary layer in the pellet and cause this. A possible trend shows a better mechanical durability with more grass in pellets. The presence of different size of particles can be a reason. Moisture content qualifies according to the European standard but is below optimum 8%. This despite to relatively high moisture content in the mixer. Higher moisture content in the press would certainly result in a generally higher quality. Suggestions for future studies are to produce pellets with greater distribution on the wetland grass added, to easier interpret a connection. Also examine the extracts behavior with different moisture content. For a sustainable development accordingly renewable energy it is important to ensure the future commodity market for pellets. Further studies should be performed to help the development of alternative raw materials in conjunction with pellet production. / Den globala uppvärmningen är en påverkande faktor gällande dagens energiutveckling. Europeiska unionens krav på mer förnyelsebar energi är därtill en anledning till det ökade intresset för bioenergi. Pelletsmarknaden har sjufaldigt ökat globalt det senaste decenniet med tidvis ansträngd resursmarknad som följd. Träspån anses komma bli en bristvara i framtiden och aktörer ser sig redan om efter alternativa råvaror. Olika typer av gräs som till exempel rörflen har visat sig ha stor potential. I denna studie testas ett våtmarksgräs som additiv i bränslepellets, med 0,5, 1, 1,5, och 1,9% inblandning. Pelletsproduktion samt tester gjordes i pilotanläggningen på Karlstads universitet, avdelningen för miljö-, och energisystem.  Energiförbrukning, fukthalt, hållfasthet och bulkdensitet är några av de variabler som testades. Pellets med våtmarksgräs jämfördes med ett referensprov med endast granspån samt ett prov med ett vanligt förekommande additiv (potatisstärkelse 1%). Kvalitén på pellets bedömdes utifrån den europeiska standarden. Resultatet visade att den specifika elförbrukningen minskade med 14% när 2% våtmarksgräs adderades, en del av den minskningen kan bero på det ökade produktionsflödet jämfört med referensprovet. De positiva effekter på specifik elförbrukning som 1% potatisstärkelse resulterade i, visade våtmarksgräs 1% liknande effekt. Detta indikerar smörjande egenskaper hos våtmarksgräset. En orsak kan vara den höga halt extrakt, såsom vaxer, som många örtartade växter består av. Dessa har i tidigare studier setts minska friktionen i pressen vilket reducerar elförbrukningen. Pellets med våtmarksgräs som additiv klarade inte de Europeiska kraven på hållfasthet. En låg fukthalt och närvaron av extrakt kan ha medfört svaga gränslager i pellets och därmed påverkat hållfastheten negativt. En svag trend visade på förbättring av hållfastheten vid högre andelar våtmarksgräs. Den varierande storleken på partiklar som sampelleteras kan ha bidragit till detta. Fukthalten är godkänd enligt den europeiska standarden men under det optimala 8%. Detta trots en relativt hög uppmätt fukthalt innan pressen. En högre fukthalt i samband med pressning hade troligen höjt kvaliteten generellt. Förslag till vidare studier är att utföra tester med större variation på mängden våtmarksgräs, för att få ett tydligare resultat. Extraktivens beteende i samband med andra varierande parametrar som exempelvis fukthalt, borde studeras närmare för att kunna bedöma våtmarksgräsets möjligheter som additiv. För en hållbar utveckling av förnybar energi är det viktigt att säkerställa den framtida råvarumarknaden för pellets. Fortsatta studier bör göras för att bidra till utvecklingen av alternativa råvaror i samband med pelletsproduktion.

The interest in superhydrophobic coatings have increased exponentially in the recentdecades due to their potential and versatility in their applications. The use forsuperhydrophobic surfaces range from water repellent fabric, to self cleaning surfacesand numerous applications in industry. In this project the durability of 6 differentsuperhydrophobic coatings have been examined. The durability was tested bydropping sand on the surfaces from a set hight of 10 cm and a flow of 40 g/min. Thesurfaces were mounted on a 45° angle. The surfaces were abraded for 30 seconds ata time and the static, receding, and advancing contact angles along with the roll-ofangle was measured. Five of the surfaces were built up with nano particles and onewas sand blasted and anodized to create a superhydrophobic structure. The surfacesthat withstood the most abrasion was the surface that had been calcined to improveadhesion and the surface that had been sand blasted and anodized. Measurementsshowed that the roll-off angle and the receding contact angle were the two bestindicators of the deterioration of a surface, while the static contact angle and theadvancing contact angle varied little with abrasion. The project was done at thecompany Technical Research Institute of Sweden (SP) at their chemistry, surfaces andmaterials department in Stockholm. All coatings and equipment was supplied by SP.

Yes / The paper reports an investigation on the mechanical durability of textured thermoplastic surfaces together with their respective wetting properties. A range of laser-induced topographies with different aspect ratios from micro to nanoscale were fabricated on tool steel inserts using an ultrashort pulsed near infrared laser. Then, through micro-injection moulding the topographies were replicated onto polypropylene surfaces and their durability was studied systematically. In particular, the evolution of topographies on textured thermoplastic surfaces together with their wetting properties were investigated after undergoing a controlled mechanical abrasion, i.e. reciprocating dry and wet cleaning cycles. The obtained empirical data was used both to study the effects of cleaning cycles and also to identify cleaning procedures with a minimal impact on textured thermoplastic surfaces and their respective wetting properties. In addition, the use of 3D areal parameters that are standardised and could be obtained readily with any state-of-the-art surface characterisation system are discussed for monitoring the surfaces’ functional response. / The full-text of this article will be released for public view at the end of the publisher embargo on 23 Jan 2020.

A degradação do adesivo e colágeno é considerada uma das principais causas de falhas nos processos adesivos à dentina. A completa infiltração de resinas hidrofóbas facilitada pelo etanol, associada à presença de inibidores de metaloproteinases presentes na dentina, poderia construir a união ideal, resistente à hidrólise e atividades enzimáticas. Este estudo examinou os benefícios do uso combinado de clorexidina como inibidor de metaloproteinases e etanol, na durabilidade de uniões resina-dentina. Foram utilizados 48 terceiros molares hígidos para obter superfícies planas de dentina que foram condicionadas com ácido fosfórico a 32% por 15 segundos, lavadas por 30 segundos, e secas com papel absorvente. Imediatamente após, uma das seguintes soluções foi aplicada por 30 segundos: água (A); etanol (E); solução aquosa de clorexidina a 1% (CA); solução alcoólica de clorexidina a 1% (CE). O excesso foi removido com papel absorvente e um dos adesivos, All Bond 3 (AB3) ou Excite (EX), foi aplicado à superfície sob agitação por 15 segundos, seguido por um jato de ar por igual tempo, e fotoativado por 20 segundos. Uma coroa de aproximadamente 4 mm foi construída incrementalmente em resina composta e os dentes foram armazenados por 24 horas em água destilada à 370C. A seguir foram cortados em paralelogramos para o teste de microtração. Um terço dos corpos de prova foi ensaiado imediatamente e os demais permaneceram armazenados por 6 ou 15 meses. Os efeitos dos tratamentos e períodos de armazenagem foram analisados para cada adesivo. Os resultados não demonstraram interação entre os fatores para ambos os adesivos. AB3 foi significantemente afetado pela armazenagem, mas não pelos tratamentos. EX foi significantemente afetado pelo tratamento, mas não pela armazenagem. Concluiu-se que o uso de clorexidina/etanol não melhorou a estabilidade da união após 15 meses. AB3 quando tratado com A ou CA, e EX com todos os tratamentos não foram afetados pela armazenagem. / Both adhesive and collagen degradation have been regarded as major causes of resin-dentin bonds failures over time. Complete infiltration of hydrophobic resins facilitated by ethanol, and the presence of MMPs inhibitors within the hybrid layer would build the ideal interface, resistant to hydrolysis and enzymatic activities. This study examined the benefits of the adjunctive use of chlorhexidine and ethanol on the durability of resin dentin bonds. Forty-eight flat dentin surfaces were etched (32% phosphoric acid), rinsed (30s) and blot-dried with absorbent paper. The surfaces were re-wetted with either water (Water); 1% chlorhexidine diacetate in water (CHX/Water); 100% ethanol (Ethanol); and 1% chlorhexidine diacetate in ethanol (CHX/Ethanol) solutions for 30s. They were then bonded with All Bond 3 (AB3, Bisco) or Excite (EX, Ivoclar- Vivadent) using a smooth, continuous rubbing application (15s), followed by 15s gentle air dry. The adhesives were light-cured (20s) and resin build-ups constructed incrementally for the microtensile method. Bonded beams were obtained and tested after 24-hours, 6-months, and 15- months water storage at 370C. Effects of treatment and testing periods were analyzed (ANOVA, Holm-Sidak, p<0.05) for each adhesive. There were no interactions between factors for both adhesives. AB3 was significantly affected by storage, but not by treatments. Excite was significantly affected by treatments, but not by storage. Adjunctive use of ethanol/chlorhexidine did not improve bond stability after 15 months. AB3 treated either with ethanol or CHX/ethanol resulted in reduced bond strengths after 15 months. AB3 treated with water or CHX/water and all treatments for Excite were not affected by storage.