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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
301

Impact resistance of deflection-hardening fiber reinforced concretes with different mixture parameters

Banyhussan, Q.S., Yildirim, Gurkan, Anil, O., Erdem, R.T., Ashour, Ashraf, Sahmaran, M. 31 January 2019 (has links)
Yes / The impact behavior of deflection-hardening High Performance Fiber Reinforced Cementitious Concretes (HPFRCs) was evaluated herein. During the preparation of HPFRCs, fiber type and amount, fly ash to Portland cement ratio and aggregate to binder ratio were taken into consideration. HPFRC beams were tested for impact resistance using free-fall drop-weight test. Acceleration, displacement and impact load vs. time graphs were constructed and their relationship to the proposed mixture parameters were evaluated. The paper also aims to present and verify a nonlinear finite element analysis, employing the incremental nonlinear dynamic analysis, concrete damage plasticity model and contact surface between the dropped hammer and test specimen available in ABAQUS. The proposed modelling provides extensive and accurate data on structural behavior, including acceleration, displacement profiles and residual displacement results. Experimental results which are further confirmed by numerical studies show that impact resistance of HPFRC mixtures can be significantly improved by a proper mixture proportioning. In the presence of high amounts of coarse aggregates, fly ash and increased volume of hybrid fibers, impact resistance of fiberless reference specimens can be modified in a way to exhibit relatively smaller displacement results after impact loading without risking the basic mechanical properties and deflection-hardening response with multiple cracking.
302

A geochemical analysis of municipal solid waste ash

Kirby, Carl Scott 07 June 2006 (has links)
Bulk chemical analysis of a combined municipal solid waste (MSW) bottom and fly ash from one facility showed most elements enriched over average soil abundances. Eleven minerals were identified using powder X-ray diffraction (XRD). Standard additions using XRD gave the following weight % minerals (±2σ): gypsum, 1.8 ± 1.9; hematite, 3.7 ± 1.7; quartz, 2.3 ± 1.0; spinel, approximately 3.5; halite, 0.5 ± 0.4; calcite 3.5 ± 1.9; rutile, 1.1 ± 1.3. Mullite, sylvite, anhydrite, and wüstite were also identified. The ash contained 18% minerals, 9% structural and adsorbed water, and 72% glass. Chemical sequential extraction showed that most Cr is present in phases resistant to chemical weathering, while significant Cd and Pb are sequestered in acid soluble (carbonate) phases. Little of these toxic trace metals are water soluble or in exchangeable surface sites. Batch reactors experiments showed that ash-water solutions were dominated by ions released by soluble salts. Three types of reactions are identified. 1) After rapid exhaustion of soluble salts, sodium and potassium exhibited nearly steady state behavior due to slow release of ions from less-soluble minerals and glasses. 2) Calcium and sulfate concentrations are controlled by either gypsum or anhydrite equilibrium after a few hours. Iron, aluminum, and manganese concentrations rapidly equilibrate with respect to hydroxide or oxide solid phases. 3) Silicon clearly shows temperature dependent kinetic behavior, but its rate of release into solution is slowed by back-reaction of a secondary silicate phase. Calculation of the CIPW normative minerals for MSW ash showed it to be analogous to a tholeiitic basalt. Over the long term, the concentrations of elements in MSW ash will continue to change and can be predicted by Goldschmidt's concept of ionic potential, and mineralogical changes can be predicted based on weathering of basalts. Comparisons of literature values showed that field MSW ash leachates contained higher concentrations of soluble salts and lower concentrations of magnesium, iron, zinc, copper, and nickel than uncombusted refuse leachates. Comparison of chromium, cadmium, lead, and arsenic concentrations did not clearly delineate which leachate contains more of these elements. / Ph. D.
303

Geoenvironmental aspects of coal refuse-fly ash blends

Albuquerque, Allwyn J. 04 December 2009 (has links)
The separate land disposal of coal refuse and fly ash presents difficulties throughout the Appalachian region, both in terms of disposal costs per acre and in terms of its potential environmental impacts on soil, ground water, revegetation, and slope stability. The purpose of this study was to determine how fly ash addition to coal refuse would impact on certain geotechnical properties of the refuse disposal piles, and whether the refuse-fly ash blends would be suitable as co-disposed materials. Accordingly, the compaction, permeability and shear strength characteristics of the refuse-fly ash blends were experimentally determined for varying fly ash percentages. The compaction test results indicated that, with increasing fly ash, the maximum dry density of these blends marginally decreased. The permeability test results showed that the permeability of the test specimens progressively decreased with the increase in fly ash. The shear strength results demonstrated that the addition of fly ash did not significantly influence the shear strength of the refuse. The critical factor of safety determined during slope stability analysis revealed that the tested slope geometries were stable for long term, drained conditions (using the STABGM computer program). The volume change analysis determined that there was a minimal expansion in the volume of refuse when it was blended with fly ash. However, it may be noted that all the stated results depend on a number offactors, including the nature of the refuse and fly ash used. Therefore, these findings would be specific to bulk blends of coal refuse and fly ash only. In general, this study indicates that fly ash can be beneficially reused with respect to the geotechnical properties evaluated. Co-disposal of fly ash and coal refuse may be a reasonable alternative to present disposal methods. / Master of Science
304

Influence of fly ash and other treatments on acid mine drainage from coal refuse

Jackson, Meral Lyn January 1993 (has links)
Most Appalachian coal refuse materials contain significant amounts of pyritic sulfur and are likely to produce acid mine drainage (AMD). A column technique was designed and implemented to evaluate the effects of various AMD mitigation treatments including fly ash, topsoil, lime, and rock-P. Two types of fly ash were tested, one at four blending rates, the other at two rates. Conventional lime plus topsoil, lime without topsoil, topsoil only, topsoil with fly ash, rock-P plus topsoil, and rock-P plus fly ash were also evaluated and compared with pure refuse controls. The columns were dosed weekly with 2.5 cm of simulated acid rain, an amount equivalent to 152 cm (60 in.) rainfall per year and remained unsaturated at all times. The experiment was conducted for 40 weeks. The drainage from the unamended columns rapidly dropped to less than pH 2 with very high levels of Fe, Mn, B, S, and Al. Alkaline fly ash dramatically reduced drainage Fe concentrations as well as Mn, Al, Cu and S when compared to the untreated refuse. As expected, lime treatments also reduced the drainage Fe, Mn, Al, Cu and S concentrations. The rock-P treatments initially reduced Fe, Mn, Al and S, but eventually decreased in mitigation capability over time. Leachate B concentrations were initially high for some of the ash columns but eventually followed the same B elution trend as the untreated refuse. The combined treatments of phosphate/ash, ash/topsoil, and pure refuse with topsoil were intermediate between the pure ash treatments and unamended refuse in drainage quality. The data were analyzed to determine treatment effectiveness in reducing AMD, and to evaluate the overall replicability of the column design. All treatments varied greatly for the first 5 weeks as the initial flush of salts from the materials occurred, but most treatments stabilized by week 6 with relatively low within treatment variability. The high ash blending rates remained alkaline for extended periods of time and stabilized pyrite while neutralizing any acidity. The rock-P treatment appears to have bound free Fe and other elements released from pyrite oxidation but did not prevent acidification. Long term analysis may prove fly ash to be a viable alternative to conventional topsoiling/lime treatments to ameliorate AMD if adequate alkalinity is present in the ash/refuse mixture. If fly ash alkalinity is inadequate to balance potential acidity, accelerated leaching of ash bound metals may occur. / M.S.
305

Geochemical Investigations of Respirable Particulate Matter

Jurinski, Joseph Bernard Jr. 22 July 1998 (has links)
Over the course of our lives we are exposed to airborne particulate matter in the workplace, home, and environment that results in the deposition of millions of particles in the lung. These exposures may result in disease if they are significant enough. The potential for harmful exposure depends in part on the dust's biodurability and the bioavailability of harmful constituents derived from the particles. A mixed flow reactor was used to evaluate two applications of geochemical methods to characterize the behavior of inhaled particles in the body. Dissolution rates of a well-characterized sample of powdered talc were measured in solvents that mimic fluids found in the human lung. These studies showed that variation of solvent chemistry, including the addition of organic chelators and proteins at intercellular fluid concentrations, does not markedly affect the measured dissolution rate of talc at 37 degrees Celcius and the data further indicate that the dissolution mechanism for talc in aqueous solutions is independent of pH over a range of pH from 2 to 8. The dissolution rate, determined by measuring the silicon release rate per unit surface area of talc is 1.4 (+/- 1.0) x 10-11 mol Si/(m2 -sec). A geometric shrinking particle model using this dissolution rate predicts an estimated lifetime (upper limit) of approximately 8 years for a 1 micron talc particle under pulmonary conditions. Talc dissolves considerably faster than quartz, but slower than chrysotile and olivine in the body. These data can be used to place constraints on the role of particle dissolution in the disease models associated with airborne respirable particulate matter. Secondly, the bioavailability of As and Cr was determined from a sample of coal fly ash from an eastern U.S. power plant. The time-release profiles of As and Cr were determined for these materials in physiologically-based solvents and incorporated into a toxicokinetic model to predict the exposure potential to As and Cr from occupational exposures to the coal fly ash. Predicted occupational exposure contributions from the ash relative to total environmental exposures were insignificant. The exposure predicted from the geochemical approach was compared with results observed in a cohort occupationally exposed to coal fly ash and found to be within one order of magnitude of the response of the occupational cohort. These results support the application of geochemical techniques to evaluate exposures to complex respirable materials. / Ph. D.
306

The dissolution of limestone, coal fly ash and bottom ash in wet flue gas desulphurization

Koech, Lawrence 03 1900 (has links)
M. Tech. (Department of Chemical Engineering, Faculty of Engineering and Technology): Vaal University of Technology / Strict environmental regulation on flue gas emission has led to the implementation of FGD technologies in power stations. Wet FGD technology is commonly used because it has high SO2 removal efficiency, high sorbent utilization and due to availability of the sorbent (limestone) used. SO2 is removed by passing flue gas through the absorber where it reacts with the slurry containing calcium ions which is obtained by dissolution. This study presents the findings of the dissolution of a calcium-based material (limestone) for wet FGD process. This was done using a pH stat apparatus and adipic acid as acid titrant. Adipic acid was used because of its buffering effect in wet FGD process. The conditions used for this study are similar to what is encountered in a wet FGD process. The extent of dissolution was determined by analyzing the amount of calcium ions in solution at different dissolution periods. The dissolution kinetics were correlated to the shrinking core model and it was found out that chemical reaction at the surface of the particle is the rate controlling step. This study also investigated the dissolution of coal fly ash and bottom ash. Their dissolution kinetics showed that the diffusion through the product layer was the rate controlling step due to an ash layer formed around the particle. The formation of ash layer was attributed to pozzolanic reaction products which is calcium-alumino-silicate (anorthite) compounds were formed after dissolution. The effect of fly ash on the dissolution of rate of limestone was also studied using response surface methodology. Limestone reactivity was found to increase with increase in the amount of fly ash added and the pH was found to be strong function of the rate constant compared to other dissolution variables. The presence of silica and alumina in fly ash led to a significant increase in the specific surface area due to hydration products formed after dissolution. / Eskom
307

Cendres volantes d'électrofiltres d'incinérateur d'ordures ménagères: traitement et incorporation dans des matériaux cimentaires / Municipal solid waste incineration electrofilter fly ash: treatment and incorporation in cementitious materials

Lenormand, Thibault 19 February 2013 (has links)
Les Cendres Volantes d’Electrofiltres (CVE) d’incinération d’ordures ménagères sont considérées comme des déchets dangereux et mises en décharges après une phase de stabilisation et de solidification par un liant hydraulique. Leur utilisation dans des matériaux cimentaires permet l’élimination d’un déchet en diminuant la demande de matériaux de construction. Cependant, avant leur incorporation dans des matériaux cimentaires, les CVE doivent subir plusieurs traitements. Premièrement, un lavage à l’eau permet de diminuer fortement la concentration en chlorures. Dans un deuxième temps, une séparation granulométrique des CVE est appliquée afin de ne sélectionner que la fraction la moins contaminée en métaux lourds, notamment en plomb et en zinc, ces métaux lourds étant connus comme retardateurs de prise. Enfin, une troisième étape consiste à oxyder l’aluminium métallique présent dans les CVE à l’aide d’un lavage basique à l’hydroxyde de sodium. S’il n’est pas oxydé durant la phase de traitement, l’aluminium métallique se transforme en aluminates dans la matrice cimentaire tout en produisant de l’hydrogène, responsable de l’apparition de vides et de fissures endommageant ainsi le matériau. Une fois traitées, les CVE peuvent alors être utilisées en substitution partielle du ciment pour une étude de leur réactivité potentielle. Les résultats de cette étude ont montré que l’activité des CVE traitées à l’hydroxyde de sodium est principalement d’origine physique (granulométrique et surface développée). Les CVE ne présentent pas de nature pouzzolanique. Les essais de lixiviation ont montré une durabilité équivalente et une très bonne stabilisation du chrome, du plomb et du zinc, qui permet de respecter les normes environnementales européennes./Municipal Solid Waste Incineration (MSWI) Electrofilter Fly Ash (EFA) is considered as hazardous waste and landfilled after stabilisation and solidification with a hydraulic binder. Its use in cementitious materials allows the elimination of a waste and a decrease of construction materials use. However, before its incorporation in cementitious materials, EFA has to be treated. Firstly, a water washing allows an important decrease in chloride concentration. In a second time, size-based separation is used to select the less heavy metals contaminated fraction, especially in lead and zinc. Indeed, these heavy metals are knows as setting retarders. Finally, a third step involves oxidizing of metallic aluminium contained in EFA during a basic washing with sodium hydroxide. Indeed, if it is not oxidize during the treatment, metallic aluminium converts in aluminates in the cementitious material, and produces hydrogen, generating cracking and voids, and damaging the cementitious material. After the treatment step, a study of the potential reactivity of EFA used in partial replacement of cement is carried out. Results show the activity of EFA treated with sodium hydroxide is mainly physical (grading and developed surface). EFA presents not pozzolanic effect. Leachability tests show an equivalent durability and a very efficient stabilisation of chrome, lead and zinc, allowing the respect of the European environmental standard. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished
308

Reclamation of fly ash lagoons: an ecological approach.

January 1999 (has links)
Chan Chik-yu. / Thesis submitted in: December 1998. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 128-152). / Abstract also in Chinese. / Acknowledgments --- p.i / Abstract --- p.ii / Table of Contents --- p.vi / List of Tables --- p.ix / List of Figures --- p.xi / List of Plates --- p.xiii / Chapter Chapter 1 --- INTRODUCTION --- p.1 / Chapter 1.1 --- Fly Ash --- p.1 / Chapter 1.1.1 --- Formation of fly ash --- p.1 / Chapter 1.1.2 --- Physical and chemical properties of fly ash --- p.1 / Chapter 1.1.3 --- Disposal --- p.3 / Chapter 1.2 --- Problems Associated with the Reclamation of Fly Ash --- p.5 / Chapter 1.2.1 --- Physical problems --- p.6 / Chapter 1.2.2 --- Nutrient problems --- p.6 / Chapter 1.2.3 --- Toxicity problems --- p.6 / Chapter 1.2.4 --- Biological problems --- p.7 / Chapter 1.3 --- Ecological Considerations on Wasteland Reclamation --- p.7 / Chapter 1.3.1 --- Ecological basis --- p.7 / Chapter 1.3.2 --- Problems of ecosystem development and its treatments --- p.11 / Chapter 1.4 --- Obj ectives of the Present Study --- p.17 / Chapter Chapter 2 --- EDAPHOLOGICAL CHARACTERISTICS OF FLY ash and vegetation composition on fly ASH LAGOON --- p.23 / Chapter 2.1 --- Introduction --- p.23 / Chapter 2.2 --- Materials and Methods --- p.24 / Chapter 2.2.1 --- Site description --- p.24 / Chapter 2.2.2 --- Collection of fly ash and soil samples --- p.25 / Chapter 2.2.3 --- Physical analysis --- p.26 / Chapter 2.2.4 --- Chemical analysis --- p.26 / Chapter 2.2.5 --- Vegetation analysis --- p.27 / Chapter 2.2.6 --- Statistical analysis --- p.27 / Chapter 2.3 --- Results and Discussion --- p.28 / Chapter 2.3.1 --- Physical properties --- p.28 / Chapter 2.3.2 --- Chemical properties --- p.33 / Chapter 2.3.3 --- Vertical ash profile --- p.42 / Chapter 2.3.4 --- Vegetation survey --- p.48 / Chapter 2.4 --- Conclusions --- p.58 / Chapter Chapter 3 --- GREENHOUSE PLANT SELECTION AND AMELIORATION TRIALS ON LAGOONED FLY ASH --- p.60 / Chapter 3.1 --- Introduction --- p.60 / Chapter 3.2 --- Materials and Methods --- p.62 / Chapter 3.2.1 --- Collection of lagooned fly ash and planting materials --- p.62 / Chapter 3.2.2 --- Plant selection trial --- p.63 / Chapter 3.2.3 --- Amelioration trials --- p.66 / Chapter 3.2.4 --- Statistical analysis --- p.68 / Chapter 3.3 --- Results and Discussion --- p.68 / Chapter 3.3.1 --- Plant selection trial --- p.68 / Chapter 3.3.2 --- Amelioration trials --- p.75 / Chapter 3.4 --- Conclusions --- p.83 / Chapter Chapter 4 --- LEACHING OF SOLUBLE SALTS AND BORON FROM LAGOONED FLY ASH --- p.84 / Chapter 4.1 --- Introduction / Chapter 4.2 --- Materials and Methods --- p.86 / Chapter 4.2.1 --- Setup of column --- p.86 / Chapter 4.2.2 --- Leaching regimes --- p.86 / Chapter 4.2.3 --- Growth of ryegrass on leached ashes --- p.89 / Chapter 4.2.4 --- Chemical analysis on ashes --- p.89 / Chapter 4.2.5 --- Statistical analysis --- p.89 / Chapter 4.3 --- Results and Discussion --- p.90 / Chapter 4.3.1 --- Leaching of soluble salts and B --- p.90 / Chapter 4.3.2 --- Plant growth in leached ashes --- p.101 / Chapter 4.4 --- Conclusions --- p.105 / Chapter Chapter 5 --- EFFECTS OF ORGANIC AMENDMENTS ON plant growth on pre-leached fly ash --- p.106 / Chapter 5.1 --- Introduction --- p.106 / Chapter 5.2 --- Materials and Methods --- p.108 / Chapter 5.2.1 --- Collection of materials --- p.108 / Chapter 5.2.2 --- Chemical analysis of planting media --- p.108 / Chapter 5.2.3 --- Plant growth experiment --- p.109 / Chapter 5.2.4 --- Statistical analysis --- p.110 / Chapter 5.3 --- Results and Discussion --- p.110 / Chapter 5.3.1 --- Chemical properties --- p.110 / Chapter 5.3.2 --- Plant growth on organic-amended ash --- p.116 / Chapter 5.3.3 --- Plant elemental uptake --- p.118 / Chapter 5.4 --- Conclusions --- p.123 / Chapter Chapter 6 --- GENERAL CONCLUSIONS --- p.125 / References --- p.128
309

Synthesis and Characterization of Geopolymers as Construction Materials

Acharya, Indra Prasad January 2014 (has links) (PDF)
Geopolymers are a relatively new class of materials that have many broad applications, including use as substitute for ordinary Portland cement (OPC), use in soil stabilisation, fire resistant panels, refractory cements, and inorganic adhesives. Geopolymers are an alternative binder to Portland cement in the manufacture of mortars and concrete, as its three-dimensional alumino silicate network develops excellent strength properties. Use of geopolymers in place of ordinary Portland cement is also favoured owing to the possible energy and carbon dioxide savings. Geopolymer is typically synthesized by alkali activation of pozzolanas at moderate temperatures (< 1000C). The focus of the thesis is synthesis and characterization of geopolymers as construction materials. In this context, the role of compositional factors, such as, pozzolana type (fly ash, kaolinite, metakaolinite, ground granulated blast furnace slag, red soil), alkali (sodium hydroxide is used in this study) activator concentration, Si/Al (Si= silicon, Al = aluminium) ratio of the pozzolana and environmental factors, namely, curing period and temperature are examined. Besides synthesizing geopolymers that could be an alternate to concrete as construction material, sand-sized aggregates were synthesized using geopolymer reactions. This was done as river sand is becoming scarcer commodity for use as construction material. Several compositional and environmental factors were varied in geopolymer synthesis in order to identify the optimum synthesis conditions that yield geopolymers with maximum compressive strength. Besides varying external (compositional and environmental) factors, the role of internal microstructure in influencing the compressive strength of the geopolymer was examined. Micro-structure examinations were made using X-ray diffraction (XRD), scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) studies. The studies on compositional and environmental factors in geopolymer synthesis brought out several interesting results. The results firstly brought out that amongst the pozzolanas studied, ASTM class F fly ash is most suited for maximum compressive strength mobilization upon geopolymer reactions. Moderate temperature (75-1000C) was adequate to mobilize large compressive strengths. Room temperature curing needed more than 7 days before the pozzolana-NaOH paste began to develop strength. Curing period of 56 days was needed for the geopolymer to develop significant strength (19.6MPa). A similar range of compressive strength could be developed by the pozzolana-NaOH paste upon curing for 3 days at 1000C. Likewise curing the pozzolana-NaOH paste at temperatures > 1000C led to reduction in compressive strength from shrinkage and breakage of bonds. A caustic soda (NaOH) concentration of 10 M was adequate to develop maximum compressive strength of the geopolymer. Caustic soda concentrations in excess of 10 M did not result in further improvement of strength. The Si/Al ratio also contributes to strength mobilization. The Si/Al ratio of the geopolymer was enhanced by mixing commercially obtained silica gel with the pozzolana. Maximum strength mobilization was observed at Si/Al ratio = 2.45 corresponding to 6.5 % silica gel addition to the pozzolana (on dry mass basis). Comparing compressive strengths of geopolymers with varying silica gel contents, geopolymer specimens with least water content and largest dry density did not exhibit maximum compressive strength indicating that the physico-chemical (bond strength, micro-structure) played a pivotal role than physical parameters (dry density, water content) in dictating the strength of the geopolymer. MIP results showed that bulk of the porosity in fly ash geopolymer specimens is contributed by macro pores and air voids. Geopolymerization leads to bulk consumption of cenospheres in fly ash and forms polymerized matrix with network of large pores. After geopolymerization, all the main characteristic peaks of Al–Si minerals observed in fly ash persisted, suggesting that no new major crystalline phases were formed. Presence of small amount of inorganic contaminants in fly ash can drastically reduce the strength of the fly ash geopolymer. For example, 5-20 % presence of red soil reduces the strength of fly ash geopolymer by 16 to 59 %. Presence of unreacted clay coupled with less porous structure is responsible for the reduction in compressive strength of fly ash geopolymer subjected to red soil addition. MIP studies with geopolymers also revealed that there is good bearing between compressive strengths and maximum intruded volume (from MIP test) of geopolymers. For example, fly ash geopolymer specimen exhibits highest total intruded volume (0.3908 cc/g) and largest compressive strength of 29.5 MPa, while red soil geopolymer specimen exhibit least intruded volume (0.0416 cc/g) and lowest compressive strength (5.4 MPa). Further, analysis showed that specimens with larger airvoids+macropores volume had larger compressive strength, suggesting that geopolymers with more porous microstructure develop larger compressive strength. All geopolymer specimens exhibited tri-modal nature of pores i.e. macro-pore mode (entrance pore radius: 25-5000 nm), mesopore mode (entrance pore radius: 1.25 to 25 nm) and air void mode (entrance pore radius >5000 nm). The micro pores (entrance pore radius < 1.25 nm) do not contribute to porosity of the geopolymer specimens. Sand particles prepared from geopolymer reactions (FAPS or fly ash geopolymer sand) predominated in medium sized (2mm to 0.425 mm) sand particles. Their particle size distribution characteristics (uniformity coefficient and coefficient of curvature) classified them as poorly graded sand (SP). Dissolution, followed by polymerization reactions led to dense packing of the Si–O–Al–O– units that imparted specific gravity of 2.59 to FAPS particles which is comparable to that of river sand (2.61). Dissolution in strongly alkaline medium imparted strongly alkaline pH (12.5) to the FAPS particles. The river sand is characterized by much lower pH (7.9). Despite being characterized by rounded grains, the FAPS particles mobilized relatively high friction angle of (35.5o) than river sand (∅ = 28.9o). The river sand-mortar (RS-M) and fly ash geopolymer sand-mortar (FAPS-M) specimens developed similar 28-day compressive strengths, 11.6 to 12.2 MPa. Despite its higher water content, FAPS-mortar specimens developed similar compressive strength and initial tangent modulus (ITM) as river sand-mortar specimens. The FAPS-M specimen is more porous (larger intruded volume) with presence of larger fraction of coarser pores. Total porosity is majorly contributed by macro-pores (67.92%) in FAPS-M specimen in comparison to RS-M specimen (macro-pores = 33.1%). Mortar specimens prepared from FAPS and river sand exhibit similar pH of 12.36 and 12.4 respectively. FAPS-mortar specimens have lower TDS (1545 mg/L) than river sand-mortar specimens (TDS = 1889 mg/L). The RS-M and FAPS-M specimens exhibit leachable sodium levels of 0.001 g Na/g RS-M and 0.007 g Na/g-FAPS-M respectively in the water leach tests. The larger leachable sodium of FAPS-M specimen is attributed to residual sodium hydroxide persisting in the FAPS even after washing. The ultra-accelerated mortar bar test (UAMBT) shows that the percentage expansion of FAPS-M and RS-M specimens are comparable and range between 0.07 to 0.08 %.
310

Vývoj vysokopevnostních betonů s vysokým obsahem el. popílků / The development of high-strength concrete with a high content of el. fly ash

Roubal, David January 2019 (has links)
This diploma thesis deals with the study of high-strength, high-volume fly ash concrete. The theoretical part of this thesis focuses on the detailed characteristic and main principles of high-strength concrete, high-volume fly ash concrete. In addition, according to the findings, the technology of high-strength and high-volume fly ash concrete, including principles of high strength, has been described. On the basis of the findings, high-strength, high-volume fly ash concrete for specific compressive strengths has been designed and created in the experimental section. These concretes were then subjected to a number of tests.

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