http://hdl.handle.net/2262/67 School of Engineering Sun, 19 May 2013 15:02:46 GMT 2013-05-19T15:02:46Z http://hdl.handle.net/2262/66465 Title: Influence of the mechanical properties of lime mortar on the strength of brick masonry Author: PAVIA, SARA Editor: Jan Valek, John J. Hughes and Caspar J.W.P. Groot Abstract: This paper aims at improving the quality of lime mortar masonry by understanding the mechanics of mortars and masonry and their interaction. It investigates how the mortar’s compressive and flexural strengths impact the compressive and bond strength of clay brick masonry bound with calcium lime (CL) and natural hydraulic lime (NHL) mortars. It concludes that the strength of the bond has a greater impact on the compressive strength of masonry than the mortar’s strength. The masonry compressive strength increased proportionally to the strength of the bond up to 6 months. A regression analysis, giving a second order equation with coefficient of determination (R2) of 0.918, demonstrates a strong and predictable relationship between bond strength and masonry compressive strength. It was noted that CL90s mortar masonry reaching a high bond value was stronger than that built with a stronger mortar but displaying a poorer bond. Finally, the mechanics of lime mortars and their masonry are similar. The predominantly elastic behaviour of the mortars of higher hydraulic strength compares well with the elastic and brittle behaviour of their masonry, with either little (NHL2) or non-existent plasticity (NHL3.5 and 5); in contrast, the CL90 mortar and masonry exhibit a plastic behaviour. Description: PUBLISHED Sun, 01 Jan 2012 00:00:00 GMT http://hdl.handle.net/2262/66465 2012-01-01T00:00:00Z http://hdl.handle.net/2262/66464 Title: Influence of loading rate and specimen geometry on lime mortar strength Author: PAVIA, SARA Abstract: Compressive and flexural strength are important properties because they relate to the quality and durability of a material, and its suitability for a particular design or application. In addition, compressive strength is a principal parameter used to classify and compare materials and establish their requirements in building standards. Therefore, it is important to establish the parameters that affect these properties so that results are comparable. It is known that specimen size and shape, water content, curing conditions, aging and compaction determine the strength of mortars and concrete. This paper sets out the influence of loading rates, increasing from 5 to 900 Newton per second, a n d s p e c i me n g e o me t r y ( c u b e s a n d h a l f p r i sms ) on the compressive and flexural strengths of hydraulic lime mortars. The limes used are NHL5, NHL2 and FL2 which develop strength as a result of hydration and carbonation. The paper concludes that compressive and flexural strength are a function of the loading rate, increasing significantly as the loading rate increases; and that the possible reason for this is that, at high strain rates, micro-cracks do not have sufficient time to search for paths of minimum energy but are forced to propagate along the shortest paths with higher resistance, and this increases the peak load at which the material fails thus increasing its strength. In addition, the results indicate that the shape and size of the specimens also impact strength (half prisms being on average 37% stronger than cubes). The ratio of length to height which determines how strains build up in the specimen is probably one of the main shape parameters that affect the strength measured. Description: PUBLISHED Sun, 01 Jan 2012 00:00:00 GMT http://hdl.handle.net/2262/66464 2012-01-01T00:00:00Z http://hdl.handle.net/2262/66463 Title: Impact of water retainers in the strength, drying and setting of lime hemp concrete Author: PAVIA, SARA Abstract: Lime hemp concrete is a sustainable, carbon negative building material that can be used in certain applications lowering the environmental impact of construction. Hemp absorbs large quantities of mixing water (325% of its own weight at 24hours), and this may not leave sufficient moisture in the binder for hydration or carbonation to take place adversely affecting curing and strength development. This paper investigates the effect of using water retainers to ensure that sufficient water is available for proper curing. Hemp concrete including a lime: pozzolan (either GGBS or metakaolin) binder and three water retainers (methyl cellulose and two commercial water retainers one of which is methyl cellulose based) were investigated. This paper studies the impact of the water retainers on strength, drying, setting and microstructure. It was found that the three water retainers delayed setting and drying. The commercial binders did not significantly affect strength however the methyl cellulose improved the compressive strength of both lime:pozzolan pastes and hemp concrete at later ages (100 days). The increase in compressive strength is partially attributed to an enhanced binder water retention that improves hydration. This assumption is based on the increase in the amount of pozzolanic cements, evidenced with SEM at the hemp interface, in the composite with methyl cellulose. Description: PUBLISHED Sun, 01 Jan 2012 00:00:00 GMT http://hdl.handle.net/2262/66463 2012-01-01T00:00:00Z http://hdl.handle.net/2262/66462 Title: Influence of the aggregate quality on the physical properties of natural feebly-hydraulic lime mortars. Author: PAVIA, SARA Abstract: This paper examines the influence of the shape, average size and calcite content of the aggregate on strength, porosity, water absorption, density and capillary suction of natural feebly- hydraulic lime (NHL 2) mortars. Four types of aggregate were analysed in order to determine calcite content, particle shape and average particle size. Four different mortar mixes were then designed and produced using each of the aggregate types and NHL 2 as a binder. The mixing and curing as well as the aggregate:binder proportions were kept constant in order to attribute variation of mortar properties to the quality of the aggregate. The results suggest that an increase in the aggregate’s calcite content lowers the flexural and compressive strength of the mortar. This study also determined that sharp aggregate as well as aggregate with a small average particle size tends to increase the mechanical strength and bulk density of a mortar simultaneously reducing porosity, water absorption and capillary suction. Furthermore, this paper concludes that aggregates containing particles of a wide size range will also increase the mechanical strength and bulk density of the hardened mortar diminishing porosity, water absorption and capillary suction. Description: PUBLISHED Tue, 01 Jan 2008 00:00:00 GMT http://hdl.handle.net/2262/66462 2008-01-01T00:00:00Z http://hdl.handle.net/2262/66461 Title: A study of the workability of natural hydraulic lime mortars and its influence on strength Author: PAVIA, SARA Abstract: Lime mortars are currently used for both repairs to historic buildings and new construction. An important mortar property is workability. Lime mortars are often described as highly workable, however, due to the many variables contributing to workability, this is difficult to quantify. Workability largely depends on water content, and this will greatly affect compressive and flexural strengths, which in turn will determine the overall quality and durability of a mortar. The objective of this paper is to examine the relationship between workability and strength of naturally hydraulic lime (NHL) mortars in order to optimize their properties for a more efficient use in building. To this aim, mortars of several hydraulic strengths were mixed with different water contents in order to vary flow diameters and charac- terize workability. Compressive and flexural strength were then tested to measure the effect of the initial flow on the strength of the hardened mortar. This paper demonstrates that NHL 3.5 and 5 mortars require a flow value close to that of 185 mm prescribed by the European standards whereas NHL 2 mixes require a significantly lower value. This paper concludes that one universal flow value is inadequate when trying to optimize strength of NHL mortars and that, in order to optimize strength,should be mixed to attain a different flow diameter for each hydraulic strength. However, other properties such as bond strength and water retention need to be considered before unique flow diameters are prescribed to lime mortars of different hydraulic strengths. Description: PUBLISHED Tue, 01 Jan 2008 00:00:00 GMT http://hdl.handle.net/2262/66461 2008-01-01T00:00:00Z http://hdl.handle.net/2262/65807 Title: Use of cognitive radio to improve spectrum usage efficiency and data capacity Author: NOLAN, Keith Description: PUBLISHED Sat, 30 Jun 2012 23:00:00 GMT http://hdl.handle.net/2262/65807 2012-06-30T23:00:00Z http://hdl.handle.net/2262/65806 Title: Cognitive Radio: Ten Years of Experimentation and Development Author: NOLAN, KEITH EDWARD Description: PUBLISHED Tue, 01 Mar 2011 00:00:00 GMT http://hdl.handle.net/2262/65806 2011-03-01T00:00:00Z http://hdl.handle.net/2262/65805 Title: Applications and Opportunities for Cognitive Radio and Networks Author: Nolan, Keith; Doyle, Linda Abstract: we present three aspects of cognitive radio and networks of importance to the research and commercial development community. We firstly outline key emerging application areas for CR/geo-location. Secondly, we look how the concept of whitespaces can be extended beyond the UHF band to other candidate spectrum segments. Thirdly, we examine regulatory policy changes being considered to increase spectrum efficiency and to support future demands for ubiquitous connectivity and capacity Description: PUBLISHED Sat, 30 Jun 2012 23:00:00 GMT http://hdl.handle.net/2262/65805 2012-06-30T23:00:00Z http://hdl.handle.net/2262/65749 Title: An overview of the University College Dublin hollow cylinder apparatus Author: Naughton, P.J.; O'KELLY, B.C. Abstract: Most sedimentary soils are inherently ansiotropic. Their response to loading will depend on the directions of the principal stresses. In most geotechnical problems the principal stresses gradually rotate during loading. As a consequence, deformations occur due to both change in the magnitude and change in the direction of the principal stresses. The Hollow Cylinder Apparatus (HCA) is the only soil test device that can facilitate independent control of both the magnitude and the direction of the principal stresses. The stress history and loading conditions at a point in a soil deposit can be reproduced on a hollow cylindrical specimen and its constitute behaviour and pore pressure response measured. This paper is divided into two sections: First, an example showing the influence of the principal stresses on the strength and deformation characteristics of a soil is discussed. Second, an overview of a unique HCA currently being commissioned in the Department of Civil Engineering, University College Dublin (UCD) is presented. The operating principles and the instrumentation used to load the sample and measure its deformational response are discussed. Description: PUBLISHED Mon, 01 Jan 2001 00:00:00 GMT http://hdl.handle.net/2262/65749 2001-01-01T00:00:00Z http://hdl.handle.net/2262/65748 Title: Design approach for improving rampart roads Author: O'KELLY, BRENDAN; MC ELVANEY, JAMES; FARRELL, ERIC RAYMOND; Osorio, J.P. Abstract: Approximately 17% of the land surface of Ireland is covered with peat. However, some counties have significantly higher values, particularly in the midlands and western counties. County Leitrim, for instance, has peat coverage of about 36%. In Ireland, the roads across the peatlands started to be properly developed during the eighteen century to gain commercial and military access to remote rural areas. During the eighteenth and nineteenth centuries peat was the only fuel most people had. The roads built across the peatlands provided better access and made peat harvesting for fuel easier. Peat harvesting led to a rapid cut away of the peat in the vicinity of the roads leaving the road surface, in some cases, many meters above the surrounding surface, creating what is known in Ireland as rampart roads. There is an urgent need to improve rampart roads in Ireland to meet the modern traffic demands, the safety requirements and to reduce maintenance costs. The roads have to be widened and the quality of the road surface has to be improved. Challenges arise from different sources when improving rampart roads. Description: PUBLISHED Tue, 01 Jan 2008 00:00:00 GMT http://hdl.handle.net/2262/65748 2008-01-01T00:00:00Z