The growth of six saxicolous lichens transplanted to lime-rich and lime-poor substrates in south Gwynedd, Wales

The objectives of this study were to investigate: (1) whether foliose lichen thalli could be transplanted from one substrate to another and (2) whether such transplants could be used to study the influence of the substrate on growth. Hence, six saxicolous lichens, with contrasting distributions on lime-rich and lime-poor substrates in South Gwynedd, Wales, were transplanted onto slate, granite, asbestos and cement. Fragments of the perimeters of thalli were glued to the different substrates using Bostic adhesive. Parmelia conspersa (Ehrh. Ex Ach.)Ach. and Parmelia saxatilis (L.)Ach., fragments increased in area over 15 months on slate and granite but decreased in area or did not survive on asbestos and cement. Fragments of Xanthoria parietina (L.)Th.Fr. and Physcia tenella (Scop.)DC. em Bitt. did not survive on slate and granite while some fragments survived but grew poorly on asbestos and cement. Parmelia glabratula ssp. fuliginosa (Fr. ex Duby)Laund. fragments decreased in area on all substrates and especially on cement and asbestos while Physcia orbicularis (Neck.)Poetsch fragments increased in area on granite and cement, decreased on asbestos and did not change significantly on slate. The results suggested that the distribution of P. conspersa and P. saxatilis was determined primarily by physico-chemical properties of the substrate. By contrast, P. glabratula ssp. fuliginosa may have responded to the transplant procedure while X. parietina, Ph. tenella and Ph. orbicularis may require nutrient enrichment to grow successfully on a substrate.

Supercritical carbonation of lime based sustainable structural ceramics

Abstract Structural ceramics were manufactured from industrial byproducts and lime by a compression moulding/vacuum dewatering technique. Treatment of these ceramics with supercritical carbon dioxide was found to both significantly increase their flexural strength and activate cementation in the industrial byproducts at least as efficiently as heat curing. Flexural strengths of up to 10 MPa were achieved. Strength improvements were associated with decreased porosity and conversion of calcium hydroxide to calcium carbonate. Life cycle assessment of proposed products made from such materials indicated that the total reduction in embodied carbon dioxide achieved, as a result of combining use of byproducts with recombination of carbon dioxide, was up to 70%. © 2010 Institute of Materials, Minerals and Mining.

The durability of cement bound minestone

The demand for road making materials continues to pressurise the supply of traditional good quality aggregates. Over the years, therefore, consideration has been given to alternative materials including industrial wastes. This thesis is concerned with potential use of Minestone, the by-product of coal mining, for the lower structural layers of pavement construction. Because of their clay like nature, Minestones do not merit consideration for such applications in an unbound state and, therefore, some form of stabilisation is necessary. Previous research has demonstrated that certain cement bound minestones, containing between 5 and 10 per cent cement, satisfy current Department of Transport requirements for use in pavement construction and, furthermore, they are not frost susceptible. However, doubts concerning the durability of cement bound minestones still remain. The thesis includes a review of both the cement and lime stabilisation techniques and also traces the origin and development of the methods used to assess the quality and durability of stabilised materials. An experimental study is described in which cement bound minestone specimens were subjected to a programme of tests which examined compressive strength, resistance to immersion, and resistance to freezing and thawing. The results of the tests were related to the properties of the raw materials. It was discovered that the response to cement stabilisation was governed mainly by the source of the minestone and, to a lesser degree, the cement content. It was also found that resistance in the durability tests was generally improved when the initial moisture content was raised above the optimum value. The result suggest that current methods for assessing cement stabilised materials are not appropriate to cement bound minestones. Alternative methods and criteria, based on volume change and retained strength following immersion and freeze-thaw tests, have been proposed. It is believed that these methods and criteria should also apply to other cement bound materials.

The beneficiation of steel making slags

The thesis examines the possibilities for the beneficiation of steel making slags by using mineral processing methods. Chemical and Mineralogical investigations have been carried out by SEM and EP}ffi to determine the most suitable separation methods in terms of crystal size, chemical composition and surface properties. Magnetic separation was applied in connection with size reductions for the extraction of the metallic iron prills and other iron containing phases and the results were related to the feed size and operating conditions. The behaviour of the slags in flotation tests was studied with respect to the recovery and grade. It was found that the free lime presence in the slags caused a high acid consumption of both weak and strong acids. It also reacted with acids and consequently produced a white precipitate, (CaS04 for H2 S04 ). The poor response of the phases to the flotation by different types of collector was found to be due to surface alteration caused by the free lime. The flocculation tests were carried out at the natural pH of the slags to prevent surface alterations. Settling tests were done to determine the suitable flocculants for the separation tests. The effect of the settling period, flocculant concentration, conditioning period and number of cleaning cycles were determined to optimize the separation tests. The discussion brings together this study with previous theoretically based work cited in the literature to elucidate the factor5governing the utilisation of steel making slags.

Corrosion and passivation of steel in concrete

A study of several chemical and electrochemical factors which affect the behaviour of embedded steel in cement pastes and concrete has been made. The effects of internal and external sources of chloride ions on the pore solution chemistry of Portland cement pastes, with and without additions of anodic corrosion inhibitors, have been studied using a pore solution expression device which has enabled samples of pore solution to be expressed from hardened cement pastes and analysed for various ionic species. Samples of pure alite and tricalcium aluminate have been prepared and characterised with respect to morphology, free lime content and fineness. Kinetics of diffusion of chloride ions in hardened pastes of alite and alite blended with tricalcium aluminate have been investigated and an activation energy obtained for the diffusion process in alite. The pore structures of the hardened pastes and the chloride ion binding capacity of alite have also been determined. Concrete cylinders containing embedded steel with four different surface conditions were exposed to various environments. The electrochemical behaviour of the steel was monitored during the period of exposure by means of rest potential measurements and the steel corrosion products analysed before and after being embedded. An examination was made of the nature of the interfacial zones produced between the embedded steel and cement. Rest potential measurements were monitored for steel embedded in alite paste in the presence of chloride ions and cement paste containing various levels of inhibitors in combination with chloride ions. In the latter case the results were supported by polarisation resistance determinations.

The deoxidation of steel with simple and complex deoxidisers

The deoxidation of steel with complex deoxidisers was studied at 1550°C and compared with silicon, aluminium and silicon/aluminium alloys as standards. The deoxidation alloy systems, Ca/Si/Al, Mg/Si/Al and Mn/Si/Al, were chosen for the low liquidus temperatures of many of their oxide mixtures and the potential deoxidising power of their constituent elements. Product separation rates and compositional relationships following deoxidation were examined. Silicon/aluminium alloy deoxidation resulted in the product compositions and residual oxygen contents expected from equilibrium and stoichiometric considerations, but with the Ca/Si/Al and Mg/Si/Al alloys the volatility of calcium and magnesium prevented them participating in the final solute equilibrium, despite their reported solubility in liquid iron. Electron-probe microanalysis of the products showed various concentrations of lime and magnesia, possibly resulting from reaction between the metal vapours and dissolved oxygen.The consequent reduction of silica activity in the products due to the presence of CaO and hgO produced an indirect effect of calcium and magnesium on the residual oxygen content. Product separation rates, indicated by vacuum fusion analyses, were not significantly influenced by calcium and magnesium but the rapid separation of products having a high Al2O3Si02 ratio was confirmed. Manganese participated in deoxidation, when present either as an alloying element in the steel or as a deoxidation alloy constituent. The compositions of initial oxide products were related to deoxidation alloy compositions. Separated products which were not alumina saturated, dissolved crucible material to achieve saturation. The melt equilibrated with this slag and crucible by diffusion to determine the residual oxygen content. MnO and SiO2 activities were calculated, and the approximate values of MnO deduced for the compositions obtained. Separation rates were greater for products of high interfacial tension. The rates calculated from a model based on Stoke's Law, showed qualitative agreement with experimental data when corrected for coalescence effects.

The effects of coloured light filter overlays on reading rates in age-related macular degeneration

Purpose: To determine the effect of coloured light filter overlays on reading rates for people with age-related macular degeneration (AMD). Method: Using a prospective clinical trial design, we examined the null hypothesis that coloured light filter overlays do not improve reading rates in AMD when compared to a clear filter. Reading rates for 12 subjects with non-exudative AMD, associated with a relative scotoma and central fixation (mean age 81 years, SD 5.07 years) were determined using the Rate of Reading Test® (printed, nonsense, lower case sans serif, stationary text) with 10 different, coloured light filter overlays (Intuitive Overlays®; figures in brackets are percentage transmission values); rose (78%), pink (78%), purple (67%), aqua (81%), blue (74%), lime-green (86%), mint-green (85%), yellow (93%), orange (83%) and grey (71%). A clear overlay (Roscolene # 00) (360 cdm-2) with 100% transmittance was used as a control. Results: ANOVA indicated that there was no statistically significant difference in reading rates with the coloured light filter overlays compared to the clear filter. Furthermore, chi-squared analysis indicated that the rose, purple and blue filters had a significantly poorer overall ranking in terms of reading rates compared to the other coloured and clear light filters. Conclusion: Coloured light filter overlays are unlikely to provide a clinically significant improvement in reading rates for people with non-exudative AMD associated with a relative scotoma and central fixation. Copyright © Acta Ophthalmol Scand 2004.

Supercritical carbonation of calcareous composites:influence of mix design

This work combined compression moulding with subsequent super-critical carbonation treatment (100 bar, 60 °C, 24 h) to fabricate cement and/or lime based ceramic composites with various aggregates. Composites were examined using mechanical testing, XRD, He pycnometry and thin-section petrography. Composites with lime-only binders were significantly weaker than those with cement-lime binders regardless of the degree of carbonation. Flexural strengths in excess of >10 MPa were routinely achieved in large (>100 mm) specimens. Aggregate type (calcareous vs. siliceous) had a significant effect on the microstructure and properties of the composites. Calcareous aggregates appear to augment the strength enhancement effected during super-critical carbonation by encouraging preferential precipitation of calcite at the binder-aggregate interface.