This thesis contains two main parts: theoretical and experimental. The theoretical part deals with summarization knowledge of high-volume fly ash (HVFA) concretes. Among others, there are mentioned processes of producing of fly ash, characteristic features and resistance to aggressive environments of HVFA concretes. The theoretical part ends with a suitable example of practical application. In the practical part were tested properties of nine different mixtures containing 40%, 50% and 60% replacement by weight of the cement by fly ash. They were compared with the reference mixtures without fly ash addition. The main endpoints were long-term compressive strength, resistance to aggressive environments, the influence of fly ash on consistency, hydratation temperatures, water absorption and volume changes.

The Portland Cement Association commissioned a research project at Brigham Young University to compare selected laboratory durability tests available for assessing stabilized aggregate base materials. The laboratory research associated with this project involved two granular base materials, three stabilizers at three concentration levels each, and three durability tests in a full-factorial experimental design. The granular base materials consisted of an aggregate-reclaimed asphalt pavement blend obtained from Interstate 84 (I-84) and a crushed limestone obtained from U.S. Highway 91 (US-91), while the three stabilizer types included Class C fly ash, lime-fly ash, and Type I/II Portland cement. Specimens were tested for durability using the freeze-thaw test, the vacuum saturation test, and the tube suction test. Analyses of the test results indicated that the unconfined compressive strength (UCS) and retained UCS were higher for specimens tested in freeze-thaw cycling than the corresponding values associated with vacuum saturation testing. This observation suggests that the vacuum saturation test is more severe than the freeze-thaw test for materials similar to those evaluated in this research. The analyses also indicated that the I-84 material retained more strength during freeze-thaw cycling and vacuum saturation and exhibited lower final dielectric values during tube suction testing than the US-91 material. Although the I-84 material performed better than the US-91 material, the I-84 material required higher stabilizer concentrations to reach the target 7-day UCS values specified in this research. After freeze-thaw testing, the Class C fly-treated specimens were significantly stronger than both lime-fly ash- and cement-treated specimens. In the vacuum saturation test, none of the three stabilizer types were significantly different from each other with respect to either UCS or retained UCS. Dielectric values measured during tube suction testing were lowest for cement-treated specimens, indicating that cement performed better than other stabilizers in reducing the moisture/frost susceptibility of the treated materials. The results also show that, as the stabilizer concentration level increased from low to high, specimens performed better in nearly all cases. A strong correlation was identified between UCS after the freeze-thaw test and UCS after the vacuum saturation test, while very weak correlations were observed between the final dielectric value after tube suction testing and all other response variables. Differences in variability between test results were determined to be statistically insignificant. Engineers interested in specifying a comparatively severe laboratory durability test should consider vacuum saturation testing for specimens treated with stabilizers similar to those evaluated in this research. The vacuum saturation test is superior to both the freeze-thaw and tube suction tests because of the shorter duration and lack of a need for daily specimen monitoring. Although the Class C fly ash used in this research performed well, further investigation of various sources of Class C fly ash is recommended because of the variability inherent in that material. Similar research should be performed on subgrade soils, which are also routinely stabilized in pavement construction. Research related to long-term field performance of stabilized materials should be conducted to develop appropriate thresholds for laboratory UCS values in conjunction with vacuum saturation testing.

The Portland Cement Association commissioned a research project at Brigham Young University to compare selected laboratory durability tests available for assessing stabilized subgrade materials. Improved understanding of these tests is needed to enable more objective selection of durability tests by design engineers and to facilitate more meaningful comparisons of data obtained for different stabilizer treatments using different evaluation procedures. The laboratory research associated with this project involved two subgrade materials, four stabilizers at three concentrations each, and three durability tests in a full-factorial experimental design. The two subgrade soils used were a silty sand and a lean clay, while the four stabilizer types included Class C fly ash, lime-fly ash, lime, and Type I/II portland cement. The three tests used in this comparative study were the freeze-thaw test, the vacuum saturation test, and the tube suction test. On average, to achieve the same 7-day unconfined compressive strength (UCS) values, the sand required 4.4 times more Class C fly ash than cement, 3.6 times more lime-fly ash than cement, and 6.0 times more lime than cement. Likewise, the clay required 10 times more Class C fly ash than cement, 7.5 times more lime-fly ash than cement, and 1.8 times more lime than cement. Analyses of the test results indicated that the UCS and retained UCS were higher for specimens tested by vacuum saturation than the corresponding values associated with freeze-thaw cycling. This observation suggests that the freeze-thaw test is more severe than the vacuum saturation test for these particular fine-grained materials. Testing also suggested that specimens with 7-day UCS values below 200 psi will generally not survive freeze-thaw cycling. After both freeze-thaw and vacuum saturation testing, the sand specimens treated with lime-fly ash had significantly higher UCS and retained UCS than specimens treated with Class C fly ash, lime, or cement. Similarly, the clay specimens treated with Class C fly ash or lime-fly ash had significantly higher UCS values than specimens treated with cement or lime; however, clay specimens treated with Class C fly ash and lime-fly ash were not significantly different. None of the four stabilizer types were significantly different from each other with respect to retained UCS after vacuum saturation testing. Dielectric values measured in tube suction testing were lowest for specimens treated with lime-fly ash and cement with respect to the sand and for specimens treated with Class C fly ash and cement with respect to the clay. The lime-fly ash and cement successfully reduced the dielectric value of sand specimens to a "marginal" rating, while no stabilizer reduced the moisture susceptibility of the clay to a satisfactory level. A strong correlation was identified between UCS after the freeze-thaw test and UCS after the vacuum saturation test, while very weak correlations were observed between the final dielectric value after tube suction testing and all other response variables. Differences in variability between test results were determined to be statistically insignificant in an analysis of the CVs associated with data collected in this research. Although the freeze-thaw test utilized in this research was determined to be more severe than the vacuum saturation test for materials similar to those tested in this study, the vacuum saturation test is recommended over both the freeze-thaw and tube suction tests because of the shorter test duration, usability for specimens with 7-day UCS values even below 200 psi, and lack of a need for daily specimen monitoring.

Master of Science / Department of Civil Engineering / Kyle Riding / Corrosion of reinforcing steel is one of the most common and serious causes of reinforced concrete deterioration. While corrosion is normally inhibited by a passive layer that develops around the reinforcing steel due to the high pH environment of the surrounding concrete, chlorides will break down this protective layer, leading to reinforcement corrosion. Decreasing the diffusivity of the concrete would slow the ingress of chlorides into concrete, and is one of the most economical ways to increase the concrete service life. Optimized concrete mixtures blending portland cement and supplementary cementing materials (SCMs) have become popular throughout the construction industry as a method of improving both fresh and long-term concrete properties such as workability, strength and porosity. It has been shown that use of Class F fly ash, silica fume and ground granulated blast furnace slag (GGBFS) in binary concrete mixture blends can result in a significant reduction in concrete diffusivity. This study investigates the ability of Class C fly ash and ternary concrete mixture blends to also aid in diffusivity reduction. In order to study the effect of incorporation of SCMs into concrete, mixtures containing Class C and Class F fly ash, silica fume and GGBFS were tested following the ASTM C 1556 procedures to measure the concrete’s apparent chloride diffusivity. Structure life cycles were modeled using the measured apparent chloride diffusivities with two finite-difference based life-cycle analysis software packages. To determine whether a correlation between diffusivity and deterioration due to freezing and thawing exists, samples were also tested for their ability to resist deterioration from freezing and thawing cycles using a modified ASTM C 666 Procedure B test. Results show that the use of Class C fly ash yields some service life improvements as compared to the portland cement control mixtures, while ternary mixture blends performed significantly better than the control mixture and equal to or better than the binary SCM mixtures tested. Freeze-thaw tests showed all mixtures to be equally resistant to deterioration due to freezing and thawing.

Modern societies produce large quantities of municipal solid waste (MSW), which is commonly disposed of by incineration. This has several advantages: it reduces the waste’s volume and sterilizes it while also enabling energy recovery. However, MSW incineration has some notable disadvantages, the most widely debated of which is probably the production and release of persistent organic pollutants (POP) such as polychlorinated dibenzofurans (PCDF), dibenzo-p-dioxins (PCDD), biphenyls (PCB) and naphthalenes (PCN). Of the 210 PCDF and PCDD congeners, 17 are toxic, with hormone-disrupting and carcinogenic properties. Twelve of the 209 PCB congeners and at least 2 of the 75 PCN also exhibit such properties. These POP form in the post-combustion zones of MSW incineration plants and are removed from the flue gas using filtering devices that trap them in the fly ash This thesis concerns the formation and degradation of POP in processes related to MSW incineration. The first paper describes a case study in which PCDD were forming in filters designed to remove them from flue gases, causing emission-related issues in a full-scale MSW incineration plant. It was shown that the PCDD formation was probably due to chlorophenol condensation on the filters’ surfaces. The second paper describes the validation of a cooling probe designed to prevent POP formation during high temperature (>450 °C) flue gas sampling. The results obtained also confirmed that PCDF and PCDD formation takes place at temperatures below 600 °C. In the third paper, three different fly ashes were subjected to thermal treatment under an inert atmosphere in a rotary kiln and in sealed ampoules at 400 °C. The concentrations, degrees of chlorination and congener profiles of the POP in the treated ashes and emitted gases were compared to those for the untreated ashes. The trends observed for PCDF mirrored those for PCN, while the trends for PCDD closely resembled those for PCB. The PCDF congener profiles of the kiln ash were similar regardless of the initial ash composition, suggesting that the mechanisms of PCDF formation were similar in all cases. The fourth paper describes the surface characterization of the three fly ashes studied in paper three by SEM, EDX, XPS and XRD. In addition, the thermal desorption and subsequent degradation of POP from the ashes was studied at temperatures of 300-900 °C. The composition of the gases released as the temperature increased differed between the ashes and depended on their composition. Doping experiments using isotopically labelled PCDF and PCDD suggests that PCDD desorbed at lower temperatures than PCDF. This thesis examines several problems relating to POP formation during MSW incineration, from sampling to the ultimate fate of incineration residues. The results obtained illustrate the wide range of processes that contribute to thermal POP formation and degradation during and after MSW incineration. / Förbränning av hushållssopor är en vanlig metod för att hantera ett växande avfallsproblem. Metoden har flera fördelar, såsom minskning av volym och vikt, sterilisering och energiåtervinning. Sopförbränning har dock vissa nackdelar och det mest debatterade är sannolikt utsläpp av persistenta organiska föroreningar (POPs) som polyklorerad dibensofuran (PCDF), dibenso-p-dioxin (PCDD), bifenyl (PCB) och naftalen (PCN). Det finns totalt 210 PCDF- och PCDD- kongener, med mellan ett till åtta klor på kolskelettet, varav 17 är giftiga med hormonstörande och cancerframkallande egenskaper. Även tolv av totalt 209 PCB-kongener samt minst två av totalt 75 PCN-kongener uppvisar liknande egenskaper. Dessa klorerade organiska föroreningar bildas då rökgaserna kyls ner i sopförbränningsanläggningarna och avlägsnas från rökgaserna med hjälp av filter och hamnar i flygaskan. Denna avhandling handlar om bildning och nedbrytning av POPs i sopförbränningsrelaterade processer.   Den första artikeln är en fallstudie där PCDD bildas i filtren i en fullskalig sopförbränningsanläggning. Bildningen ledde till förhöjda halter organiska föroreningar i rökgaserna, vilket ledde till ökade utsläpp. Den funna bildningsvägen för PCDD i filtren befanns sannolikt bero på kondensation av klorfenoler på filterytorna. Den andra artikeln är en valideringsstudie av en kylprob avsedd att användas vid rökgasprovtagning vid hög temperatur (> 450 °C) för att undvika bildning av POPs under provtagningen. Studien bekräftade att majoriteten av PCDF- och PCDD- bildning i rökgaser från sopförbränning sker vid temperaturer under 600 °C. I den tredje artikeln berättas om behandling av tre olika flygaskor från olika sopförbränningsanläggningar. Askorna behandlades vid 400 °C i inert atmosfär i både en roterugn och i förseglade ampuller. De resulterande koncentrationerna, kloreringsgraderna och kongenprofilerna av de organiska föroreningarna jämfördes. Likheter hittades mellan PCDF och PCN, medan PCDD och PCB betedde sig på ett annat sätt. Studien fann också att PCDF kongenprofiler i aska som behandlats i roterugnen liknade varandra, oberoende av askornas sammansättning, vilket tyder på en liknande bildningsväg. För den fjärde artikeln, genomfördes ytkarakterisering (SEM, EDX, XPS och XRD) på de tre flygaskorna från artikel tre som sedan hettades upp från 30 °C till 900 °C i vacuum. Det som frigjordes på grund av uppvärmningen samt nedbrytningsprodukter från askorna studerades med hjälp av masspektrometri och infraröd spektroskopi. Studien fann att de gaser som frigjordes när temperaturen ökade skilde mellan askorna, beroende på deras sammansättning. Studien fann också att när aska dopad med isotopmärkt PCDF och PCDD utsattes för samma behandling, frigjordes PCDD vid lägre temperatur än PCDF. Denna avhandling berör flera aspekter av problematiken kring klorerade organiska föroreningar som bildas vid sopförbränning, från provtagning till hur man ska hantera flygaskan. Avhandlingen belyser även olika typer av bildning och nedbrytning av POPs i varma processer kopplade till sopförbränning.

Thesis (MScAgric)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Coal mining in South Africa is estimated to produce 200 Ml of acid mine drainage (AMD) per day in the Pretoria-Witwatersrand-Vereeniging (PWV) area alone, while electricity production resulted in approximately 27 Mt of ash in 2001. A large number of collieries in South Africa are tied to power stations where these two waste streams, acid mine drainage and fly ash, have the capacity to neutralize each other and provide an opportunity for co-disposal. The aim of this study was to investigate the reactions that occur during the co-disposal of fly ash leachate (FAL) and AMD and to examine the precipitates that result from the neutralisation reactions. Potentiometric titration was employed to investigate the neutralisation of Al-Fe salt solutions, simulating acid mine drainage (AMD), with alkaline solutions of Ca or Na hydroxide as well as fresh alkaline leachate from fly ash (FAL). The effectiveness of fly ash in removing metals and other salts from acid mine water was examined by analysing the neutralised water and modelling the results thermodynamically. Precipitates, prepared from large scale synthetic AMD and FAL co-disposal at various pH levels and Fe:Al ratios, were characterised according to composition, mineralogy and surface properties. The experimental neutralisation of synthetic acid mine drainage was achieved through titrating the components of SAMD (Fe and Al salt solutions) and solutions of various Fe:Al mole ratios with different bases in air and N2, and comparing the SAMD-FAL system with these simple acids and bases. The FAL used in all experiments was produced from fresh fly ash collected at Arnot power station. The SAMD was prepared as a solution with a pH of 2.5 and containing 12.7 mmol/L Al, 10.9 mmol/L Fe and 40.8 mmol/L SO4. The characterisation of reaction solids was achieved by collecting the precipitates formed from the co-disposal of FAL and SAMD with Fe:Al ratios of 7.3, 0.8 and 2.5. From the titration experiments it was found that upscale potentiometric titrations of SAMD show buffer zones at pH values of 3.5, 4, 6 and 10 corresponding to Fe(III)precipitation, Al precipitation, Fe(II) hydrolysis and oxidation, and Al redissolution, respectively, while downscale potentiometric titrations with SAMD show buffer zones at pH values 12 – 11, 9 and 4.5, which correspond to Fe oxidation and precipitation, Al precipitation and Al re-dissolution, respectively. A high concentration of Al in the simulated AMD inhibited the crystallinity of the precipitates and resulted in a large quantity of SO4 being removed from solution, which suggests that an aluminium sulphate phase is precipitating, but it is not crystalline and cannot be identified by XRD. Titrations performed up-scale by adding FAL to AMD showed near-complete metal and substantial SO4 removal from solution. The characterisation of reaction solids by x-ray diffraction, infrared spectroscopy, thermal gravimetric and differential thermal analysis revealed that the precipitates consist of poorly crystalline, highly Al-substituted goethite and ferrihydrite with large amounts of SO4 included in the structure. Poorly crystalline bayerite appears at a high pH and high Al concentration, and calcite is present in precipitates made by adding SAMD to FAL. High surface charges of between 330 cmolc/kg positive and 550 cmolc/kg negative charge and potentially large specific surface areas between 7 and 236 m2/g suggest a strong potential for the precipitates to function as low-grade adsorbents in wastewater treatment. The similarity of these ochre precipitates to soil minerals implies that land disposal of the neutralised solids is also viable. / AFRIKAANSE OPSOMMING: Steenkool mynbou in SA produseer na benaming 200 ML suur mynwater per dag in die PWV area alleenlik, terwyl opwekking van elektrisiteit naastenby 27 Mt vliegas geproduseer het in 2001. ’n Groot aantal steenkoolmyne in SA word verbind met kragsentrales, waar hierdie twee strome afval, suur mynwater en vliegas, die kapasiteit het om mekaar te neutraliseer en die weg te baan vir gesamentlike wegdoening. Die doel van hierdie studie was om die reaksies wat plaasvind gedurende gesamentlike wegdoening van vliegas loog (VAL) en suur mynwater (SMW) te ondersoek, asook die neerslae wat mag vorm as gevolg van neutralisasie reaksies. Potensiometriese titrasies was gebruik om die neutralisering tussen Al:Fe-sout oplossings te ondersoek as nabootsing van SMW met gebruikmaking van alkaliese oplossings van Ca of Na hidroksied asook vars loog van VA. Die effektiwiteit van VA om metale en soute uit SMW te verwyder was getoets deur outleding van die geneutraliseerde water en modellering van die termodinamika. Neerslae berei uit groot-skaal sintetiese SMW en VAL en met gelyktydige storting by verskeie pH vlakke en Fe:Al verhoudings, was gekarakteriseer volgens samestelling, mineralogie en oppervlak eienskappe. Die eksperimentele neutralisering van sintetiese suur mynwater (SSMW) was gedoen deur titrering van die SSMW komponente en oplossings van verskeie Fe:Al molêre verhoudings met verskillende basisse in lug en N2, en vergelyking van SSMW-VAL sisteem met hierdie eenvoudige sure en basisse. Die VAL gebruik in alle eksperimente was geproduseer van vliegas verkry van die Arnot kragsentrale. Die SSMW was berei as ’n oplossing met ’n pH van 2.5 en bevat 12.7 mmol/L Al, 10.9 mmol/L Fe en 40.8 mmol/L SO4. Die karakterisering van vastestowwe uit die reaksie was gedoen deur die bemonstering van neerslae gevorm as gevolg van die gelyktydige wegdoening van VAL en SSMW met Al:Fe verhoudings van 7.3, 0.8 en 2.5.Die was waargeneem in die titrasie eksperimente dat hoër-skaal potensiometriese titrasie van SSMW buffersones, by pH waardes 3.5, 4, 6 en 10, ooreenstem met Fe(III) presipitasie, Al presipitasie, Fe(II) hidrolise en oksidasie, en Al her oplossing, terwyl laer skaal potensiometriese titrasie met SSMW buffer sones by pH waardes 12 - 11, 9 en 4.5 ooreenstem met Fe(III) presipitasie en oksidasie, Al presipitasie en heroplossing respektiewelik. ’n Hoë konsentrasie Al in die sintetiese SMW het kristalliniteit van die neerslae geïnhibeer en veroorsaak dat ’n hoeveelheid SO4 uit oplossing verwyder is, wat suggereer dat die AlSO4 fase neerslaan maar nie kristallyn is en gevolglik nie opgetel word met x-straal diffraksie nie. Titrasies gedoen by hoërskaal deur byvoeging van VAL tot SSMW, het feitlik volledige metaal en SO4 verwydering uit oplossing getoon. Die karakterisering deur x-straal diffraksie, infrarooispektroskopie, termies gravimetries en differentiële termiese analise, het getoon dat die presipitate bestaan uit swak kristallyne, hoë Al-gesubstitueerde goethiet en ferrihidriet met groot hoeveelhede SO4 vasgevang in die struktuur. Swak kristallyne bayeriet verskyn by hoë pH en hoë Al-konsentrasies en kalsiet is teenwoordig in neerslae gevorm deur byvoeging van SSMW tot VAL. Hoë oppervlakladings van tussen 330 cmolc/kg positief en 550 cmolc/kg negatiewe lading en ook potensieel groot spesifieke oppervlak van tussen 7 en 236 m2/g, dui op ’n sterk potensiaal vir neerslae om as laegraadse adsorbeermiddels in afvalwaterbehandeling gebruik te word. Die ooreenstemming in hierdie geelbruin neerslae met grond minerale, impliseer dat die land storting van geneutraliseerde vastestowwe ook lewensvatbaar is.

Zeolites are among the least-known products for environmental pollution control, separation science and technology. Due to their unique porous properties, they are used in various applications in petrochemical cracking, ion-exchange and separation and removal of gases and solvents. The preparation of synthetic zeolites from chemical reagents is expensive. Therefore, in order to reduce costs, zeolite researchers are seeking cheaper aluminosilicate bearing raw materials, such as clay minerals, to produce synthetic zeolites. This research concerns the synthesis of zeolites and zeotypes derived from low-cost materials like kaolinite (KAO), natural clinker (NC) and fly ash (FA). The motivation for using these sources as the starting materials in zeolite synthesis is driven by factors, such as they are cheap and available in bulk quantities, are currently under-utilized, have high workability, and require less water (or solution) for activation. The raw materials were activated by two different routes: (1) classic alkaline hydrothermal synthesis and (2) alkaline fusion prior to hydrothermal synthesis. In the first method, the synthesis of zeolitic materials was carried out generally in alkaline media, although KAO or its calcination product, metakaolinite (MTK), was also activated in the presence or absence of structure directing agents (SDAs) and additional silica (precipitated SiO2), with the last one determining the SiO2/Al2O3 ratio of the reaction mixture and the time given for zeolitization. Synthesis in fluoride- and calcium-bearing media was also used to activate kaolinite. The process of synthesis was optimized by applying a wide range of experimental conditions with a wide range of reaction temperature, time, mineralizer concentration and solid/solution ratio. In the second approach, an alkaline fusion step was conducted prior to hydrothermal treatment, because it plays an important role in enhancing the hydrothermal conditions for zeolite synthesis. On the other hand, this approach was adopted because it can dissolve more aluminosilicates. The main synthesis products obtained after activation of KAO in NaOH solutions included zeolite LTA (LTA), sodalite (SOD), cancrinite (CAN), faujasite (FAU), zeolite Na-P1 (GIS), JBW-type zeolite (JBW), analcime (ANA), whereas the activation of KAO in KOH solutions produced chabazite (CHA), zeolite Barrer-KF, phillipsite (PHI) and K-feldspar. The hydrothermal conversion of kaolinite in fluoride media did not produce successful results, although traces of FAU, GIS, CHA, SOD and CAN crystallized. The activation of KAO in the system CaO-SiO2-Al2O3-H2O promoted the formation of different calcium silicate hydrate (C-S-H) phases, including hydrogarnet (HYD) and tobermorite (TOB). Following the fusion approach, the main zeolitic phases obtained using NaOH as mineralizer were LTA and CAN. The main as-synthesized zeolites obtained from NC by the conventional hydrothermal treatment method include PHI, SOD and CAN. Using the fusion approach, FAU and LTA were obtained with NaOH as an activator, whereas non-zeolitic material crystallized when KOH was used. The main as-synthesized zeolitic materials obtained by hydrothermal reaction of FA include PHI, zeolite Barrer-KF, CHA and SOD with traces of TOB, ANA, zeolite LTF (LTF) and herschelite (HER), appearing occasionally. By the fusion approach, FAU was obtained with NaOH as activator, whereas no zeolitic material crystallized using KOH. Experimental results indicate that the method, mineralizer, concentration and time have strong effects on the type and degree of crystallinity of the synthesis products. On the other hand, the type and chemical composition of the as-synthesized products are strongly dependent on the chemical composition of the starting material. The chemistry of zeolite synthesis was subject to perturbations caused by the presence of impurities in the raw materials, which may remain insoluble during crystallization and cause undesired species to nucleate, developing mixtures of different types of zeolites. However, other physicochemical factors may play a very important role in the thermodynamics and kinetics of zeolite formation. The raw materials have very high contents of SiO2 and Al2O3, with SiO2/Al2O3 ratios appropriate for the synthesis of low-Si zeolitic materials with high crystallinity and cation exchange capacity (CEC). However, although zeolites’ CEC represents a very important characteristic quality in the removal of undesired species from polluted effluents, it is not the deciding factor in determining zeolite performance during ion exchange processes, since numerous other factors also need to be considered. Finally, the potential application of the raw materials and their as-synthesized products as low-cost sorbents in the remediation of metal ions and ammonium from wastewater effluents was investigated. PHI showed a lower efficiency than FAU. Selectivity of FAU for metal removal was, in decreasing order, Fe>As>Pb>Zn>Cu>Ni>Cr. Based on these results, the use of these materials has the potential to provide improved methods for the treatment of contaminated effluents.

A utilização de cinza volante na composição de material cimentício o torna mais sustentável, além de conferir à matriz hidratada características peculiares que melhoram o desempenho frente à ação de diferentes agentes deletérios. A principal desvantagem da utilização de pozolana no sistema cimentício é a maior susceptibilidade à carbonatação. A maior taxa de neutralização da solução aquosa dos poros é devida ao teor remanescente menor de portlandita na matriz. O conhecimento das características da cinza volante que influenciam a interação com a cal, é necessário para subsidiar medidas preventivas com relação ao consumo de portlandita. A presente pesquisa objetiva verificar a eficiência da adição de cal hidratada em concreto executado com cimento pozolânico como forma de reduzir a susceptibilidade à carbonatação. As etapas realizadas para cumprir o objetivo abrangem: a caracterização da cinza volante, com ênfase na determinação do teor de fase vítrea; a cinética de reação em sistema de cinza volante e hidróxido de cálcio; a evolução da hidratação, e a decorrente variação microestrutural. Nos sistemas cimentícios de concretos cujas composições são 100% de cimento ou 50% de cimento e 50% cinza volante, com e sem a adição de 20% de cal hidratada, foi caracterizado a microestrutura da camada de cobrimento e o seu desempenho frente à ação do anidrido carbônico, em ensaio acelerado. Na cinza volante estudada, o teor de fase vítrea foi de 57%, e o consumo máximo por atividade pozolânica, função da área específica BET, foi de 0,69 gramas de Ca(OH)2/grama de fase vítrea de cinza volante. No cimento portland pozolânico, este consumo é menor devido à estrutura formada pela hidratação do cimento. A adição de cal hidratada à pasta de cimento e cinza volante, além de aumentar o consumo de cal por atividade pozolânica, restabeleceu, parcialmente, o teor remanescente de portlandita na matriz. A interação da cinza volante com a cal hidratada não interfere no volume total de vazios da matriz hidratada, porém, refina a microestrutura, aumentando o volume de mesoporos. A carbonatação, em concretos com mesma resistência à compressão de 55 MPa, atingiu maior profundidade quando executado com cimento pozolânico. A adição de cal hidratada não foi eficiente em reduzir a susceptibilidade à carbonatação acelerada. / The use of fly ash in the composition of the cementitious material makes it more sustainable, besides conferring to the hydrated matrix peculiar characteristics which improve its performance with relation to the action of different deleterious agents. The main disadvantage of pozzolan utilization in cementious systems is its susceptibility to carbonation. The greatest neutralization rate of the aqueous solution of the cement pore is, generally, attributed to the smallest amount of portlandite remaining in the matrix. It is necessary to widen knowledge about the characteristics of the fly ash which influence the interaction with calcium hydroxide in order to promote preventive measures with regard to portlandite consumption. This current research aims at verifying the efficiency of hydrated lime addition to concrete by using pozzolanic cement as a way of reducing its susceptibility to carbonation. The steps employed to attain this objective include: fly ash characterization with an emphasis on glass content; fly ash and calcium hydroxide systems kinetics; hydration evolution; and the consequent microstructure variation. In cementious systems of concrete whose composition is either 100% cement or 50% cement and 50% fly ash _ with or without 20% addition of hydrated lime _ it was characterized the microstructure of covercrete and its performance with regard to the interaction with carbon dioxide in accelerated testing. In the studied fly ash, glass content was 57% and the maximum consumption per pozzolanic activity, which is function of BET specific surface area, was 0.69 g of Ca(OH)2/g of glass content in the fly ash. As far as pozzolanic Portland cement is concerned, this consumption is smaller due to the structure formed by the cement hydration. The addition of hydrated lime to the cement paste and fly ash, besides increasing the consumption of lime per pozzolanic activity, partially, reestablished the remaining content of portlandite in the matrix. The interaction of the fly ash with the hydrated lime does not interfere in the total volume of void spaces in the hydrated matrix; however, it refines the microstructure by increasing the volume of mesopores. Carbonation in concrete with the same compressive strength of 55 MPa reached its deepest point when performed in pozzolanic cement. The addition of hydrated lime was not efficient at reducing susceptibility to accelerated carbonation.

Submitted by Andrea Pereira (andrea.pereira@unipampa.edu.br) on 2017-04-10T17:48:36Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação_Rodrigo_Final_Impressão.pdf: 2591713 bytes, checksum: 3d6be77e2f47aca595d592660db94e02 (MD5) / Approved for entry into archive by Andrea Pereira (andrea.pereira@unipampa.edu.br) on 2017-04-10T17:48:55Z (GMT) No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação_Rodrigo_Final_Impressão.pdf: 2591713 bytes, checksum: 3d6be77e2f47aca595d592660db94e02 (MD5) / Made available in DSpace on 2017-04-10T17:48:55Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação_Rodrigo_Final_Impressão.pdf: 2591713 bytes, checksum: 3d6be77e2f47aca595d592660db94e02 (MD5) Previous issue date: 2015-08-21 / Esta pesquisa estudou o desgaste por erosão atuante nos tubos de troca térmica do economizador de uma caldeira por meio de testes in loco, testes em laboratório seguindo os padrões da norma (ASTM G76-95) e simulações computacionais. Durante as análises, foram avaliados os comportamentos das ligas de aço como: ASTM A213T2, ASTM A213T22, ASTM A213T91, ASTM A210C e ASTM A106B, em função das variáveis velocidades, concentração, composição da cinza volante, temperatura e erosão quando expostos às mesmas condições operacionais. Esta investigação objetivou fornecer subsídios às premissas de projeto e seleção de materiais, bem como aumentar o tempo de vida útil dos componentes quando submetidos a condições adversas na caldeira em função das variáveis observadas. O controle da erosão e desgaste dos tubos tem como propósito a contribuição para a redução dos custos de manutenção, verificando-se falhas nos tubos do economizador prematuras, que causam indisponibilidades forçadas da caldeira o que gera prejuízos de grande vulto. Utilizou-se difração de raio x para análise de composição mineralógica das cinzas volantes. Para auxiliar na escolha da região de estudo, foram realizados cálculos de simulação CFD com o propósito de verificar o local exato onde a ação da velocidade dos gases de exaustão mais prejudicam os dutos no interior do economizador da caldeira. A avaliação da erosão por cinza volante, oriunda da Caldeira 4, do Complexo Termelétrico de Candiota, ocorreu em duas etapas distintas. A primeira foi realizada em condições de processo e, a segunda, em testes de bancada. Os testes em condições de processo foram acompanhados por ensaios para avaliar a evolução do desgaste das ligas de aço, como, pesagem, medição de espessura por ultrassom, digitalização em scanner 3D e dureza. O teste de bancada utilizou, como referência, a norma ASTM G76-95, fornecendo parâmetros para a confecção das amostras, assim como a própria bancada de testes. Os ensaios foram fundamentais para quantificar os resultados, como, pesagem e digitalização em scanner 3D. Os resultados encontrados por meio deste estudo possibilitaram um maior conhecimento dos mecanismos de erosão nas ligas de aço com o uso das cinzas volantes. Dessa forma, foi possível encontrar soluções para melhorar as premissas de projeto, assim como identificar os limites de aplicação dos materiais estudados em um projeto dessa natureza. / This research studied the erosion mechanism active in heat exchange tubes of a boiler by means of in site tests, laboratory tests following the standard (ASTM G76-95) and computer simulations. During the analysis, we evaluated the behavior of alloy steel such as: ASTM A213T2, ASTM A213T22, ASTM A213T91, ASTM A210C and ASTM A106B, in function on the variable speed, concentration, fly ash composition, temperature and erosion when exposed to the same conditions operational. This objective investigation to provide inputs on design assumptions and material selection, and increase the service life of components when subjected to adverse conditions in the boiler depending on the observed variables. Control of erosion and wear of the tubes are intended to contribute to the reduction of maintenance costs, checking for failures in premature economizer tubes, causing forced outages boiler which generates large-scale losses. It was used x ray diffraction for the analysis of mineralogical composition of fly ash. To auxiliary in choose the region the study, were performed CFD simulation studies with the purpose the verify the exact place where the action of the velocity of the exhaust gases more prejudice the ducts inside the boiler economizer. The assessment of erosion by fly ash, coming from the boiler 4, the Thermoelectric Complex Candiota, occurred in two distinct stages. The first was realized in process conditions and, the second in bench tests. The tests in process conditions were followed tests to assess the evolution of wear of alloy steel, as, weighing, measuring thickness by ultrasound, 3D scanner and hardness. The test bench utilize as a reference to ASTM G76-95, providing parameters for confection the samples, as well as own bench tests. The tests were fundamental to quantify the results, as, weighing and scanning 3D. The results found by means of this study allowed a more knowledge of erosion mechanisms in alloy steel with the use of fly ash. In this way, it is possible to find solutions to improve the design assumptions, as identify the application limits of the materials studied in a project of this nature.

O emprego de resíduos da indústria como materiais alternativos na Engenharia vem sendo tópico recorrente em pesquisas de desenvolvimento de novos materiais, devido a uma maior consciência da opinião pública quanto ao impacto ambiental oriundo da produção industrial. Buscando colaborar com esta discussão, esta pesquisa procurou inserir dois resíduos (cinza volante e cal de carbureto), gerados na região metropolitana de Porto Alegre, como alternativa de solução em Engenharia. Analisando-se a microestrutura da cinza volante, observa-se que ela é formada por esferas ocas e plerosferas (esferas ocas preenchidas por esferas menores). Foi estudado o ganho de resistência da mistura promovido pela moagem da cinza volante em um moinho de bolas cerâmicas, visando uma potencialização da reatividade do material. A fim de possibilitar a utilização destes resíduos, é necessário um estudo do seu comportamento mecânico decorrente da cimentação proporcionada pela mistura e compactação destes materiais. A presente pesquisa busca fornecer subsídios para que seja possível determinar o seu comportamento, através do uso da relação porosidade (η)/teor volumétrico de cal (LV) obtidas a partir da identificação e quantificação das variáveis mais importantes no controle da resistência da mistura dos dois resíduos, com e sem o processo de moagem da cinza, levando a formulação de equações para previsão da resistência à compressão simples do material cimentado para cinza volante com diferentes tempos de moagem e cura acelerada. Para isso, foram realizados ensaios de compressão simples em corpos de prova com 5, 10 e 15% de cal, com peso específico aparente seco de 11, 12 e 13 kN/m3, curados por 7 dias, com umidade de 18% para os tempos de moagem 0, 2 e 6h nas temperaturas 23 e 40°C, e 0 e 6h a 60°C. Os resultados apontam que o aumento do teor de cal gerou ganhos de resistência para as maiores temperaturas de cura; a diminuição da porosidade proporcionou um ganho de resistência para todas as combinações; o aumento da temperatura foi importante no ganho de resistência entre 23oC e 40oC; a moagem da cinza por 2h promoveu ganhos significativos de resistência em relação à não moída, porém, para 6h de moagem os ganhos não foram significativos para as temperaturas de cura de 23oC e 60oC. A relação η/LV, ajustada por um expoente [η/(Lv)0,07], mostrou-se adequada na formulação de equações na previsão da resistência do material cimentado para todas as temperaturas e tempos de moagem estudados. Além disso, a existência de relações únicas e distintas no controle da resistência à compressão simples em função da porosidade, teor volumétrico de cal, temperatura de cura e tempo de moagem, mostraram-se úteis para formulações de dosagem. Os resultados foram submetidos à análise de variância que comprovou que todos os fatores controláveis escolhidos para o experimento são significativos, assim como todas suas interações. / The use of industry by-products as alternative materials in Engineering has been a recurring topic of research in development of new materials, mainly, due to a larger public conscience regarding the environmental impact of industrial production of waste. Aiming to contribute on this discussion, this research sought to introduce two by-products (fly ash and carbide lime), produced on the metropolitan area of Porto Alegre, as an alternative Engineering solution. Analyzing the microstructure of the fly ash, it is observed that it is composed by void spheres and plerospheres (void spheres filed with smaller ones). Having that in mind, it was studied the admix strength gain promoted by the grinding of de fly ash on a ceramic ball mill, aiming an enhancement of the reactivity of the material. In order to enable the use of these byproducts, it is necessary the study of its mechanical behavior due to the cementation provided by the mixture and compaction of these materials. The current research seeks to provide subsides in order to determine its behavior, through the use of the ratio porosity (η)/ volumetric lime content (LV), obtained from the identification and quantification of the most important variables on the control of the strength of the admixes of both by-products, with or without the process of fly ash grinding. This means, the formulation of equations for the simple compressive strength forecast of the cemented material for the fly ash with different grinding times and accelerated curing temperature. In order to do so, it were realized simple compression tests with 5, 10 and 15% of lime, with a specific dry unit weight of 11, 12 and 13 kN/m3, cured for 7 days, with water content of 18% for the grinding times of 0, 2 and 6h to the curing temperatures of 23 and 40oC, and 0 and 6h to 60oC. The results show that, the increase of lime content provided strength gains for the higher temperatures; the decrease of porosity generated strength gain to all the combinations; the increase in curing temperature was important on the strength gain between 23oC and 40oC; the grinding of fly ash for 2h promoted significant strength gains when compared to the not ground samples, however, for 6h of grinding the strength gain wasn’t significant for the 23oC and 60oC curing temperatures. The η/LV ratio, adjusted by an exponent [η/(LV)0,07], presented itself adequate for the formulation of the equations for the forecast of the strength gain of the cemented material to all the studied temperatures and grinding times. Besides that, the existence of unique and distinct relationships on the control of the simple compression strength depending on the porosity, volumetric lime content, curing temperature and grinding time, have been shown useful for the dosage formulation. The results were submitted to variance analysis, which demonstrated that all the factors chosen on the experiment were significant, as all their interactions.