Concrete is the most widely used construction materials in the world with more than 1 m3 of concrete being produced every year for every person on the planet. However, concrete has much lower tensile strength than compression strength and, therefore, is easy to crack under normal service conditions. Cracking in concrete can reduce load carrying capacity and may lead to premature deterioration. In the case of reinforced concrete, cracks reduce overall durability of structures by allowing the penetration of water and aggressive agents, thereby accelerating the deterioration of reinforcing steel. Corrosion of the reinforcing steel in concrete structures such as motorway bridges, buildings and marine installations costs the UK an estimated 550m per year according to Building Research Establishment. Most of these structures continue to require extensive maintenance or replacement. Over the years, engineers have sought to develop simple tests to assess how susceptible a given concrete mixture may be to cracking. Currently, there are three main test methods for assessing cracking potential of concrete mixtures: the ring, the beam and the plate tests. Though the circular ring test has become a standard method, it has very low cracking sensitivity, making it very time-consuming and not cost effective. Besides, cracking can appear anywhere along the circumference of a circular ring specimen, making it very difficult to be located. On the other hand, it has been found difficult to provide a constant restraint and end condition for the beam and plate tests, making their applications very limited.In this project, we will develop a new test method by using elliptical ring specimens to assess cracking tendency of concrete mixtures. Compared to circular ring specimens, the elliptical ring specimen can lead to a higher stress concentration and increased cracking sensitivity, making the elliptical ring test method less time-consuming and more efficient. Besides, due to stress concentration, the location of cracking will concentrate on predictable positions along the circumference of an elliptical ring specimen, thus making it much easier to be detected. The elliptical ring test is therefore helpful for determining the relative likelihood of cracking of concrete mixtures in a much shorter period and for aiding in the selection of concrete mixtures that are less likely to crack before they are used for construction projects. We will also establish a theoretical model to provide design engineers with a tool to predict cracking potential of various concrete mixtures. The theoretical model will be able to predict when and where crack will occur in a concrete elliptical ring specimen. We will also explore the effects of specimen size/geometry and the degree of restraint on shrinkage cracking of concrete to provide the guidance on choosing the geometries of both the elliptical concrete ring specimen and the restraining steel ring for estimating cracking tendency of concrete in the field.Dissemination of the findings to the academic community will be made by quality journal papers and presentations at prestigious conferences. The technique explored in this research will be transferred to the construction industry through technical seminars organized by the project partners through their network, articles published in magazines of the concrete industry, the project website and consultancy service. We will also present our findings obtained from this project to relevant standard organisations, particularly the European Committee for Standardization (CEN), for possible recommendation as a standard test method for estimating cracking tendency of concrete mixtures.

There are substantial commercial pressures driving the current trend in reinforced concrete multi-storey structures towards longer spans and thinner structural depths. The potential benefits of clear open spaces, the freedom of placing services and the reduction of building height (and the subsequent potential reduction in cladding costs) or conversely, the ability to incorporate an extra floor in the building (thus increasing rental potential) can have a significant effect on the overall economics of a scheme. However, these benefits cannot be fully exploited until it is possible to predict accurately the long-term deflection of concrete elements.A major problem in predicting the long-term deflection of cracked concrete flexural elements has always been the difficulty in isolating the deformation due to shrinkage from the effect of other parameters such as creep and tension stiffening. Current codes predict the long-term deflection of cracked concrete elements by using the approach developed for uncracked sections but incorporating cracked section properties. Whilst there is no question of the correctness of this in relation to uncracked sections, it has never been experimentally validated for cracked sections. Consequently, it may be extremely conservative and, therefore, have a restrictive influence on design strategy. The effect of shrinkage on a cracked section remains uncertain as it has not been possible to confirm the influence experimentally. The applicants now believe it is possible to overcome this difficulty and this application proposes an extremely innovative experimental approach which will allow the effect of shrinkage on the deformation of cracked members to be isolated for the first time. Recently, research by the applicants under a previous EPSRC funded project has resulted in a much better understanding of the tension stiffening phenomenon and, in particular, its decay with time. The effects of creep are already generally well understood. The results of the proposed research, and the data obtained by the Leeds and Durham concrete research team on tension stiffening, will finally allow designers to predict the long-term deflection of cracked concrete flexural elements with greater reliability.The current climate within the construction industry and the effect this has had on the cost and availability of steel is leading, and will continue to lead, to an increased use of concrete in construction (e.g. the major new Clarence Docks development in Leeds, where previously steel would have been chosen). The research is, therefore, very timely. It is now even more critical that this information is available to designers to ensure that maximum efficiency in the design and use of concrete is achieved so as not to restrict their competitiveness within the UK and EU construction industry.The proposed research will be performed at both the University of Leeds and the University of Durham. The experimental programme consists of two stages. The initial stage is concerned with confirmation of methodology. The second stage will isolate the effect of shrinkage using the innovative approach proposed by the investigators, contributing to an improved design method and more accurate assessment of shrinkage. The proposal has 6 industrial collaborators providing in-kind and cash contributions totalling 33,460. The total amount of funding being sought by the two universities is 274,537.

Concrete is the most widely used construction material and is essential to the global programme of infrastructure updating (global estimate ~$100tn including UK National infrastructure plan £400bn) (www.oxfordeconomics.com/publication/open/283970). Excessive cracking due to restraint in poorly designed reinforced concrete (RC) structures is a widespread problem in the concrete construction industry and leads to many instances of costly remedial measures and delays. For example, a recent project in England was delayed due to excessive cracking caused by the restraint of imposed strains (from early thermal and shrinkage actions). Subsequent changes recommended by the applicants during the construction programme to limit the edge restraint of early thermal and shrinkage strain produced a real cost saving to the client of approximately £1.75M. The design guidance developed in this research will increase the performance and efficiency of new RC infrastructure as well as prolong the life of existing infrastructure through improved understanding of cracking. There are many situations when cracking due to the restraint of imposed deformations may be difficult to avoid. In fact, cracking from the restraint of early thermal movements (often referred to as 'non-structural' cracking) is the most common form of restraint induced cracking. In design, cracking is managed by the provision of reinforcement intended to distribute internal strains in such a way as to control the cracking pattern and limit crack widths. Current UK/EU design guidance on restraint induced cracking is encapsulated in EN1992-3:2006 and CIRIA report C660/766. The underlying design methodology in these documents has been used for over 30 years and is flawed. This is reflected in field observations identifying cracking patterns contrary to - and crack widths in excess of - those predicted by EN1992-3:2006. It is apparent that such 'non-compliance' cases result from erroneous basic assumptions; in particular; the boundary (restraint) conditions play a more significant role in determining the crack pattern than assumed in the current design guidance. The outcome of this research will provide practising engineers with the ability for the first time in three generations of UK/EU codes to correctly design RC elements for the restraint of short and long-term imposed strains. Planned dissemination routes will significantly aid the reduction in frequency and overall number of non-compliance cases, which currently result from the poor understanding of restraint induced cracking and affect all aspects of concrete construction in the UK.

This proposal from Loughborough University outlines the case to renew the funding for the Industrial Doctorate Centre for Innovative and Collaborative Construction Engineering (CICE) as part of the Industrial Doctorate Centres call aginst the Towards Better Exploitation element of the EPSRC Delivery Plan. In partnership with an established industry base, CICE is delivering a high quality research and training programme that: meets the core technical and business needs of the construction industry; enhances its knowledge base; and produces high calibre doctoral graduates that can drive innovation. The Centre addresses a wide range of research issues that concern the UK construction industry including: Innovative Construction Technologies; Construction Business Processes; Advanced Information and Communication Technologies; Sustainable Design and Construction; and Transport and Infrastructure. Many of these areas have been highlighted in various reviews of the industry including the Latham Report, the Technology Foresight Report, the Egan Task Force Report, and more recently the National Technology Platform's research priorities. It also contributes to the EPSRC Delivery Plan as part of the knowledge transfer research and training activities. The research areas of the Centre align with the Engineering and Science for Sustainability research theme, as outlined in the EPSRC's Research Priorities and Opportunities, and fall under the 'Construction and the Built Environment' and 'Transport' sub-themes. Within the Construction and Built Environment, the Centre builds on existing strengths in the Department of Civil and Building Engineering established as part of the Engineering Doctorate Centre and other related industry based research to address some of the EPSRC research priorities to improve efficiency across the supply chain, including: encouraging the uptake of ICT to promote efficiency; improving building performance to minimise impacts on the environment ; and the analysis and design of civil engineering structures . Within the Transport area Sustainability and Innovation are key themes of the research that centres on transport operation and management, transport telematics, and minimising energy use and environmental impact . The Engineering Doctorate Centre (CICE) was established in 1999 and has subsequently recruited a total of 94 research engineers sponsored by a total of 63 large, medium and small companies. Loughborough University is a research intensive institution, which integrates its research and teaching activity at every opportunity to provide a top quality research led learning experience for all its students. The Department of Civil and Building Engineering has consistently achieved high research rating in the RAE assessments and the last RAE results were 5* in Built Environment. The Engineering Doctorate is part of Loughborough University's excellent doctoral research training programme, which in addition to supporting the pursuit of a particular project aims to provide a basic professional training to support the research and offer personal development opportunities. The training programme integrates taught and research elements tailored to suit the needs of the research engineer, project, and the sponsoring company while maintaining the expected quality of the academic standards required for a doctoral study. The Centre is managed by the Director, Prof. Dino Bouchlaghem supported by a Deputy Director, a Centre Manager and an Administrator. A Centre Management Board consisting of the Director, Deputy Director, and Industrial Representatives meets twice a year and is chaired by a senior industrialist from one of the sponsoring companies, oversees the work of the Centre and provides direction and guidance on strategic matters. This proposal has the full support of the University and has been subject to an internal review process to ensure synergy with the University's Research Strategy.