No description available.

No description available.

The primary aim of this research was to improve the understanding of the influence of the process and the mix constituents on the fresh and hardened properties of wetprocess sprayed mortars and concretes. The main objectives were: to improve the wetmix spraying process; to specify, measure and optimise in-situ properties; and to disseminate the information obtained in appropriate form to practising engineers to accelerate the use of wet-process sprayed mortar and concrete for repair. The research focused on three types of repair mortars/concretes: pre-blended proprietary mortars (<3 mm aggregate), designed laboratory/site batched mortars and fine concretes (<8 mm aggregate). Thirty mixes were pumped and sprayed using seven pumping/spraying systems. Nineteen types of test were conducted to measure the fresh and hardened properties using three types of specimen production (cast mould, sprayed mould and in-situ specimen). Ten repair scenarios generally encountered in the UK were identified and classified in terms of their characteristics and relevant mixes were identified to satisfy these differing requirements. A rheological audit has been developed and a variety of tests were used to characterise the pumpability and sprayability of each mix, including: rotational viscometers (Tattersall two-point test and Viskomat), pressure-bleed, shear vane, slump, build, fresh density, output, stream velocity (using high-speed video), reinforcement encasement and core grading. A new approach that defines the build in terms of the maximum shear and tensile bending stresses generated at failure was also developed. Hardened properties measured include: compressive and flexural strength, tensile bond strength, drying and restrained shrinkage, elastic modulus, air permeability, sorptivity and hardened density. The hardened performance was generally higher when sprayed with the wet process compared with hand application and lower when compared with the dry process (which was expected), although the values obtained were more than sufficient for normal repair work. All the pre-blended mortars could be pumped and sprayed with a small worm pump. Twelve laboratory-designed mortars were pumped and sprayed in a dedicated spraying chamber constructed at Loughborough and the best of these performed as well as, and produced hardened properties that equalled or surpassed, the pre-blended materials. For worm pumping the grading of a mortar was found to be important and a suitable combined material grading zone has been determined. Two pre-blended and a laboratory-designed mortar were sprayed with a piston pump as were the nine designed concrete mixes, the former producing similar in-situ properties to worm pumping. One pre-blended mix was sprayed successfully with five different wet-process pumps (four worm plus one piston) and three pre-blended mortars and one designed fine concrete were sprayed by the dry-process to benchmark performance, along with data from three repair contracts. The hardened property measurements obtained from spraying directly into steel moulds with a low-volume worm pump were consistent enough to have applications for quality control. The research demonstrated that low-volume wet spraying is a healthier, cleaner and more controllable process (compared with the dry process) which can produce consistently high quality mortars and fine concretes suitable for a range of applications in the UK.

The development of electrochemical techniques as applied to self-assembled supramolecular systems (e. g. micelles) has advanced over the past decade. The main properties that have been elucidated by these techniques have been micellar selfdiffusion and size. Although there are reports that have paid attention to the qualitative influence of intermicellar interactions on the behaviour of the micellar system, quantitative assessments of interaction are very limited. In this thesis, the application of rotating disk voltammetry, primarily, has led to a quantitative rationalisation of intermicellar interactions in cationic and nonionic micellar systems over a range of surfactant and electrolyte concentrations. Two `normal' micellar systems are studied with aggregates formed from cationic (CTAC) and nonionic (Triton X-100) surfactants. Initial measurements and analysis yields micellar sizes that are consistent with published values, demonstrating the validity and the ease of application of electrochemical techniques. Measuring self-diffusion coefficients over a range of electrolytes provides a comprehensive assessment of micellar phase behaviour and yields further structural parameters which are conventionally determined using a variety of methods. The first reported study of electrochemistry in a reverse micelle `nanoemulsion' is presented. The growth in micellar size on the addition of a solubilised probe gives important inferences for the careful control of particle growth in a reverse micelle `nano-reactor'. In summary, the thesis, as the title states, gives new insights pertaining to micellar structural evolution and interaction. The thesis will examine the benefits of applying electrochemical techniques to study micellar systems and concentrate, predominately, on the wealth of information that can be obtained by the resultant analysis. The work forms an excellent basis for not only further quantitative analysis but also as a phenomenological template for employment in the study of a diversity of self-assembled supramolecular species.

No description available.

Flow around a cylinder is important in the motion of microorganisms found in biological viscoelastic fluids that propel themselves by flagella. Flow around a cylinder experiments are difficult to perform because of the influence of the walls and ends. An approach was developed to measure the drag on a cylinder by correcting for wall and end effects. Cylinders were vertically dipped into fluids in an annular shaped tank, which was rotated to generate a flow. The force acting on a cylinder was measured using a custom force transducer. This method was used for a Newtonian fluid and two Boger fluids. The drag of the Boger fluids was several times that of an equivalent Newtonian fluid. A cavity was observed to develop behind the cylinders once the flow surpassed a critical velocity. Streakline images taken during the experiment confirmed the presence of a wake region behind the cylinders.

Flow around a cylinder is important in the motion of microorganisms found in biological viscoelastic fluids that propel themselves by flagella. Flow around a cylinder experiments are difficult to perform because of the influence of the walls and ends. An approach was developed to measure the drag on a cylinder by correcting for wall and end effects. Cylinders were vertically dipped into fluids in an annular shaped tank, which was rotated to generate a flow. The force acting on a cylinder was measured using a custom force transducer. This method was used for a Newtonian fluid and two Boger fluids. The drag of the Boger fluids was several times that of an equivalent Newtonian fluid. A cavity was observed to develop behind the cylinders once the flow surpassed a critical velocity. Streakline images taken during the experiment confirmed the presence of a wake region behind the cylinders.

Continuous accumulation of Mature Fine Tailings (MFT) is a major challenge to oil sands industry. To reduce the inventory of MFT through development of novel tailings treatment technologies, it is essential to understand the stabilization mechanism of fine solids in MFT. This project aims at characterizing fine solids of MFT. A novel method is developed in this study to understand characteristics of fine solids in MFT by studying their response to the changes in water chemistry and chemical treatment. Settling and rheological response of MFT to chemical additives is determined. Combined with solids characterization of the different layers of settled MFT, an enhanced understanding of stabilization of fine solids in MFT is gained. The knowledge generated through this study will provide a scientific basis for technology development of MFT treatment. / Chemical Engineering

Taken as an engineering material, mozzarella cheese can be considered as a complex food system that has dynamic structure and complex flowproperties. Food scientists have been actively developing methods to characterize mozzarella cheese rheologically, but most of these methods are empirical in nature. In the past decades, there has been a paradigm shift towards the utilization of well-developed rheological methods which have been widely applied in the study of commercial synthetic polymers. In this work, the rheology of mozzarella cheese was studied using well-developed rheological techniques. Utilizing various rheometers, the linear and non-linear rheology of mozzarella cheese was examined. General practical properties of mozzarella cheese such as meltability, flowability and stretchability were extracted from these results. Capillary flow and rolling experiments were also performed to determine their suitability as innovative post-production processing techniques for mozzarella cheese. Finally, a comparative study on the effect of frozen storage on the rheology of three different brands of mozzarella cheese was performed. In general, it was found that mozzarella cheese can be classified as a pseudoplastic (shear thinning) semi-solid material possessing a yield stress at room temperature. Upon heating, the yield stress gradually diminishes and it can be considered as a viscoelastic fluid. The results obtained from the various rheometers indicate that the yield stress, duration of experiment, sample geometry and temperature greatly affect the consistency of the results. It was also shown that extrusion can be used as a processing technique for mozzarella cheese above a certain temperature where the cheese is in a melt state. Rolling was also found to be a potentially feasible processing method. Finally, in terms of the effect of frozen storage, in general, the dynamic moduli decrease with the period of storage due to the freezing of the proteins in the cheese.

Rheological and processing behavior of a number of linear low-density polyethylene(LLDPE)/low-density polyethylene (LDPE) blends was studied with emphasis on the effects of long chain branching. First, a linear low-density polyethylene (LL3001.32) was blended with four LDPE's having distinctly different molecular weights. At high LDPE weight fractions, DSC melting thermograms have shown three different polymer phases; two for the pure components and a third melting peak of co-crystals. Different rheological techniques were used to check the thermo rheological behavior of all blends in the melt state and the effect of long chain branching. It was found that all blends are miscible in the melt state at small LDPE concentrations. The elongational behavior of the blends was studied using a uniaxial extensional rheometer, SER. The blends exhibit strain hardening behavior at high rates of deformation even at LDPE concentrations as low as 1%, which suggests the strong effect of branching added by the LDPE component. On the other hand, shear rheology was found to be insensitive to detect addition of small levels of LDPE up to lwt%. The second set of blends prepared and studied consisted of two Ziegler-Natta LLDPE's (LL3001.32 and Dowlex2045G) and two metallocene LLDPE's(AffinityPL1840 and Exact 3128) blended with a single LDPE. In DSC melting thermograms, it was observed that blends with metallocence LLDPE's exhibit a single melting peak at all compositions; whereas the Ziegler-Natta blends exhibit three melting peaks at certain compositions. It was found also that the metallocene LLDPE's are miscible with the LDPE at all concentrations. On the other hand, the Ziegler-Natta LLDPE's were found to be miscible with LDPE only at small LDPE concentrations. The processing behavior of all blends with emphasis on the effects of long chain branches was also studied in capillary extrusion. The critical shear stresses for the onset of sharkskin and gross melt fracture are slightly delayed with the addition of LDPE into LLDPE. Furthermore, the amplitude of the oscillations in the stick-slip flow regime, known as oscillating melt fracture, were found to scale with the weight fraction of LDPE. Amounts as low as 1 wt% LDPE have a significant effect on the amplitude of pressure oscillations. These effects are clearly due to the presence of LCB. It is suggested that the magnitude of oscillations in the oscillating melt fracture flow regime can be used as a method capable to detect low levels of LCB. Finally, the sharkskin and stick-slip polymer extrusion instabilities of a linear low-density polyethylene were studied as a function of the type of die geometry. The critical wall shear stress for the onset of flow instabilities, the pressure and flow rate oscillations, and the effects of geometry and operating conditions on the instabilities are presented for a LLDPE. It was found that sharkskin and stick-slip instabilities were present in the capillary and slit extrusion. However, stick-slip and sharkskin in annular extrusion are absent at high ratios of the inside to outside diameter of the annular die. This observation also explains the absence of these instabilities in polymer processing operations such as film blowing. These phenomena are explained in terms of the surface to volume ratio of the extrudates.