No description available.

No description available.

Alternative materials represent an important potential source of aggregates for road construction. At present, their use remains limited owing to the abundance and low cost of high quality natural aggregates, low costs of landfill disposal and generally restrictive specifications for pavement materials. Nevertheless, their influence in relation to the primary aggregates is likely to increase in the future with the enforcement of more strict environmental regulations at national and European levels. The objective of this research project was to investigate a wide range of alternative materials and provide a practical framework for their assessment enabling pavement engineers to deal with most applications in road construction. Initially secondary materials were assessed according to the present UK specifications and were found to fail the requirements in most cases. However, the current approach does not assess fundamental properties such as stiffness, resistance to permanent deformation, tensile strength, resistance to fatigue and the development of these with time, leading to an inadequate assessment of these materials. To advance towards the development of performance-based specifications repeated load triaxial and indirect tensile tests were used. For their performance the Nottingham 150x300 mm triaxial apparatus was used and an indirect tensile apparatus developed which evolved from the Nottingham Asphalt Tester used for bituminous materials. In triaxial testing, models used to study the resilient behaviour of granular materials were found to give good results for unbound but not for lightly-treated secondary materials. For these, a new resilient model was developed. Testing and specimen preparation techniques together with performance classification systems were developed for both tests and recommendations for an overall methodology for the evaluation of secondary materials are presented. An application of this methodology was made to the study of thirteen mixtures to be considered for full-scale trials. The application of secondary materials in pavements was evaluated using analytical methods of pavement design which demonstrated the potential of these at levels in the pavement as high as the roadbase and the overall thickness reduction that may result.

This document contains the detailed results and conclusions of work carried out during a PhD to investigate the processing, production and performance of dynamically compacted cement-stabilised soil blocks suitable for sustainable low-cost building. An earlier project carried out by the author demonstrated that full-size blocks could be manufactured by dynamic compaction. It was hoped that this technique could be applied to the self-evident need for low-cost housing in the humid tropics. The apparent advantages of this process, over quasi-static compression (slow steady squeezing), have led to further investigation into the critical factors influencing the production of such building units. Initial tests on small cylindrical samples produced by both quasi-static compression and dynamic compaction provided a means of comparison and helped to develop relationships between dominant variables. These tests showed that the moisture content of the compact was a critical variable, influencing its consolidation and its final cured strength. Optimisation studies were undertaken to determine acceptable parameters for impactor mass, drop height and number of applied blows. These chosen parameters were then extrapolated to full-size block production with the necessary adjustments for practicality and cost. Full-size block production using the Test Rig indicated similar relationships as those discovered at the smaller scale, including the more effective consolidation offered by dynamic compaction. From this experience a production prototype was designed and disseminated to a collaborator in India for further trials and feasibility studies. These trials demonstrated that dynamic compaction could produce blocks with a 7-day wet compressive strength of between 3-5MPa with only 5% cement, (typical building regulations require block strength greater than 3.5MPa after 28-days). Feasibility studies there indicate dynamic compaction offers potential savings of 40% compared with local high-tech CSSB manufacture.

No description available.

[by] Albert G. H. Dietz.

The focus of this thesis has been the feasibility of a novel load transfer concept for a carbon fibre reinforced plastic (CFRP) tendon system using non-laminated pin-loaded straps. The principle of these straps is that, as the tensile load increases, the relative slip between the layers produces a more uniform strain distribution in the layers leading to a higher load carrying capacity than when the laminate is fully consolidated (i.e. a laminated strap). This principle has been shown to occur by observing relative displacement between individual layers and strain measurements. Such components could be used for post strengthening purposes of existing structures. They have the potential to alleviate the current problems associated with the corrosion of externally applied steel reinforcement. Furthermore, the low density of CFRP’s in combination with appropriate design procedures can provide a cost competitive solution. This advantage of choosing a non-metallic material is strengthened when whole life cycle costs are considered since composites are expected to outlive the conventional repair materials. One objective of the project was to develop a tape material with continuous parallel fibres at low cost. At the start of the project no material available was suitable in terms of cost or quality. To drive the cost of the material down, thin lamina tapes with a thermoplastic matrix were considered. The various manufacturing processes for thermoplastic prepreg tape were reviewed and the powder impregnation process was found to meet the project's specifications. This method can produce high quality prepreg at a higher production rate compared to pultrusion with a thermosetting matrix. Sulzer Innotec Ltd. had an existing aqueous powder impregnation facility for research and development purposes. The author collaborated with the company to make specific modifications to the facility with the objective of improving material quality. This was achieved towards the end of the project, and in the thesis this material is referred to as Tape IV. Preliminary development work was carried out throughout the duration of the project to characterise five thermoplastic materials. Two practical connection methods where developed to anchor the final outer layer in the non-laminated strap option. It was found that the clamping method was superior to the fusion bonding method; both methods will, however, find applications. A new manufacturing process for laminated pin-loaded straps was developed and is reported. The author used MARC K6.2, a commercial finite element software, to predict the stress concentrations in the region where the strap makes contact with the steel pin. The difficulties associated with the advanced numerical modelling included contact and friction. The required results from MARC K6.2 were highly dependent on a sliding velocity parameter for which no accurate value was known. Because of the lack of rigor in the formulation of the finite element model, the stress concentrations predicted could not be used to optimise strap detailing. For completeness the MARC K6.2 modelling is described and the results reported. To exploit the technology, research and development work will be needed, and the thesis shows where there are gaps in our knowledge and understanding.

Within the UK traditional masonry construction techniques are struggling to deliver the quantity and ecological quality of housing required by an ever increasing UK population. This research employs a case study review of a mainstream mixed timber frame and masonry housing development - Green Street, in order to explore the ecological viability of timber prefabrication as an alternative to the established masonry construction methods currently employed in the majority of British housing. Four houses of each construction type in the Green Street development were outfitted with a number of environmental monitoring sensors for continuous monitoring. In addition the study incorporates fabric testing in the form of air permeability testing, Co-heating analysis, thermography, and a life cycle analysis. Building Use Survey, project management and design team interviews and an industry questionnaire form the final part of the evaluation protocol. The study revealed that heating the timber dwellings ultimately required less energy per degree difference between inside and outside temperatures. During the summer the timber housing displays a greater diurnal temperature swing, while on average the temperature remains consistently lower than the masonry housing. The masonry housing was found to be both more air tight and exhibiting a lower heat loss coefficient, despite that, the performance gap between design and reality for space heating is less in the timber prefabricated housing. The life cycle analysis revealed that the timber walls have a lower impact on climate change. BUS methodology results found that construction type had little to no impact on occupants. The design team review highlighted the need for a greater level of prefabrication in timber housing to increase precision and work around a serious skills shortage. An industry questionnaire suggested that timber construction in the UK can often suffer from poor construction practice, predicated by a gap in specialized knowledge. The research concludes that in this instance, the timber prefabrication technique produced dwellings that perform ecologically on par with their masonry counterparts. In answering the research question, the evidence suggests that at this stage the technique would be better employed on a case by case basis and supported by specialists in timber fabrication, rather than implemented as a blanket alternative for existing masonry construction. Already a number of insights from this research have filtered into industry practice and will continue to better inform both industrial and academic partners in their decisions regarding the use of timber prefabrication in mainstream UK housing.

The United Kingdom published a legally binding document to reduce national greenhouse gas emissions by year 2020 up to 34% against the 1990 levels. This target also fulfils the Europe 2020 strategy of 20% carbon emission reductions by year 2020 (EC, 2010). Emissions due to space heating count for around 60% of the total domestic emissions (DCLG, 2012). The report “Rethinking Construction” published in 1998 emphasised the opportunities to improve the quality and efficiency of the UK construction sector (Egan, 1998). More recently, a framework has been published by the Government to tackle fuel poverty by building more energy efficient homes (DECC, 2015). In terms of energy performance, Passivhaus is recognised as one of the most energy efficient and researched construction standards which requires an exceptionally high-level of insulation and airtightness. Closed-panel timber frames are a relatively new system in UK with an opportunity for growth. These advanced panels are pre-fitted in the factory, reducing the on-site work. However, closed-panel systems present a more complex sole plate fixing detail which can have an undesirable long-term impact on the structural and thermal performance of the building. The work presented in this thesis investigates the structural considerations, racking performance, of timber frame closed panel systems for future building regulations. The thesis underlines the significance of structural stability, serviceability and detailing in relationship with long-term thermal efficiency and airtightness, according to Passivhaus standard. An experimental study was carried out to investigate the structural racking performance of advanced closed panel systems. A comparison was made between the behaviour of the timber frame panels and the analytical PD 6693-1. A set of different wall panel built-ups is presented for optimised Passivhaus design, including thermal bridge-free sole plate details. A timber frame racking software application was developed to optimise the structural design of shear walls. A parametric study was carried out with this tool to generate efficient timber frame wall design tables for different applied racking loads and U-values. The software application also allows for direct specification of robust sole plate base fixings and thermal bridge free details.

The research is based on the European Directive aimed at harmonising standards for construction products. Harmonised standards remove technical barriers to trade allowing manufacturers to sell their products anywhere in the European Economic Area (EEA) provided the product complies with the standard and has affixed the CE marking. This should lead to greater competition in all EEA markets. A review of relevant literature covered three distinct areas; developments of the European Union and the Construction Products Directive (CPD), the UK construction industry and materials sector and strategic management concentrating on market barriers and entry strategies. The research combined these areas together by investigating the impact of the CPD on the UK construction product manufacturers specifically considering the strategic decisions of the UK brick industry. As there was little previous empirical research into this area, data was generated through exploratory interviews with manufacturers and bodies involved with the UK implementation of the Directive, through a self-completion postal questionnaire survey with manufacturers from six product groups and by a case study approach used to examine the UK brick industry. The research demonstrated that the Directive is having little impact to date on the strategic decisions of UK construction product manufacturers. Also, there are a disturbing number of producers that were not aware of the Directive and its possible implications. By applying previous research findings to the UK brick industry, conclusions were drawn highlighting the specific nature of this industry and identifying specific characteristics that influence its competitiveness. The Directive and the UK brick industry have never previously been examined in such a manner and areas for further research have been suggested.