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The corrosion of embedded steel rebar in reinforced concrete (RC) structures, which are the backbone of every nation's infrastructure, is a major issue. Interventions relating to the corrosion of RC structures are estimated to amount to about 35% of the total volume of all work in the global building sector. Reinforcement corrosion is induced via mobile chloride ions or other structurally harmful contaminates within the reinforced concrete, which happens due to a variety of reasons such as marine environment, de-icing salt in winter seasons, chloride content in concrete mixing and the use of sea sand, etc. With reinforcement corrosion, the load-bearing resistances of RC structures are reduced, with severe potential safety issues and also immense economic loss. A new intervention method, ICCP-SS (impressed current cathodic protection and structural strengthening), has recently been proposed. ICCP-SS combines the merits of impressed current cathodic protection (ICCP) and structural strengthening (SS) technologies, but uses one dual-functional material - carbon fibre reinforced cementitious matrix (C-FRCM). In this dual functional material, the carbon fibre (CF) mesh serves as the anode for ICCP and also the strengthening material for SS, while the cementitious matrix is the conductor for ICCP and the bonding material for SS. Previous studies have demonstrated effectiveness of the ICCP-SS technology for RC members. However, it has been found that prolonged ICCP would cause calcium leaching in the cementitious matrix at the anode interface, leading to drastic loss of mechanical properties and significant increase of electrical resistance of the bond between the cementitious matrix and CF mesh. Reducing calcium leaching to a level that does not adversely affect structural resistance is possible by increasing the compactness and the electrical conductivity of the cementitious matrix to achieve a more uniform electrical resistive field in the anode interface; introducing a tiny amount of graphene into the cementitious matrix has the potential to do so. The key to solving the problem is to prevent (or significantly slow down) the breakdown of C-S-H gel (i.e. loss of calcium) at anode interface under the same ICCP current density and duration. The remarkable properties of graphene make it a potentially ideal solution to this problem by producing a more uniform electrical field and more compact microstructures of the cementitious matrix. This project aims to solve two issues: to quantify the bond mechanical behaviour (for SS) and the electrical resistance at the CF/cementitious matrix interface (for ICCP) due to leaching, and to investigate means of reducing leaching. In summary, the ICCP-SS intervention method has vast potential in prolonging life of RC structures and introducing a small amount of graphene flakes in the dual-functional cementitious matrix has a number of beneficial synergistic effects to help realise the full potential of ICCP-SS.

The lifetime extension of existing highway and building reinforced concrete infrastructure is a priority in terms of economic prosperity and a more sustainable future. The ability to reduce disruption, and amortise the embodied energy and the environmental impact of construction over an extended period will lead to direct, tangible and significant savings in energy and resource consumption. As construction typically accounts for up to 10% of the UK's GDP, and half of UK construction activity is associated with refurbishment and repair, it is clear that there is substantial scope to implement efficient technological innovations in the construction sector. In the UK, a major challenge is that, not only is the average age of our infrastructure increasing, but also the loading requirements are becoming more demanding. So the national pool of structures requiring intervention due to deterioration, changes of use, and/or a lack of strength is growing. For reinforced concrete (RC) structures, fibre-reinforced polymer (FRP) materials have been used as additional reinforcement to increase, or reinstate, strength capacity. These materials have a high strength-weight ratio, are durable and easy to install. To date, carbon FRP resin bonded strengthening systems have been the most common. The market share of FRP-strengthening applications has resulted in a proliferation of usage across the industry, and indeed continues to grow year on year. However, the development of our understanding has not kept pace with the growth in applications. There are significant gaps in our knowledge when typical large bridge or building structures and practical strengthening configurations are considered. The shear strengthening of RC structures is a particular challenge due to accessibility issues, the brittle nature of shear failures and the complex mechanics of the behaviour. Initial design guidance has played an important role in establishing the basis for the use of FRP systems but this guidance has necessarily drawn upon the results of specific studies which often only encompass a subset of possible parameters and interactions e.g. small-scale rectangular beams. However, there is an increasing body of evidence that suggests that a number of aspects of the fundamental shear behaviour are not captured in existing guidance. Recent studies have highlighted apparent contradictions between the predicted and observed behaviour of FRP strengthened large scale structures and structures with complex geometries. In particular, work at Cambridge University and Bath University have shown that in T-beams, which are considered representative of slab-on-beam structures, the current guidance can be unconservative yet for large scale rectangular beams, overly conservative. These contradictions pose difficulties since large-scale, slab-on-beam structures constitute a large proportion of the infrastructure that surrounds us and represents a target area for the use of FRP strengthening for lifetime extension. In the current project, a comprehensive experimental and analytical programme will be undertaken to understand the fundamental mechanics of beams strengthened in shear using bonded carbon FRP fabric systems. The effect of size will be investigated by considering strengthened T-beams with scales ranging from 'laboratory' scales to realistically sized structures found in practice. These targeted studies will lead to improved design approaches which reflect a comprehensive understanding of the failure mechanisms and the interactions that depend on the geometry and size of the structure. The deliverables will have a significant and timely impact through the provision of practical, safe and durable technological advances to enable the upgrading of existing RC structures to meet the demands of the 21st century.

The construction industry is heavily reliant on production of Portland cement and, in the UK alone, 12 MT of cement is produced per annum. Depending on the specific production processes used, manufacture of 1 kg of Portland cement produces 0.7 kg - 1.0 kg of CO2. Many sources suggest that cement manufacture accounts for up to 5% of the world's CO2 emissions. There is an urgent need for a step change in technology to achieve the radical reductions in carbon emissions necessary to stabilise climate change. Many different approaches can be used to mitigate the effects of cement production. Considerable improvements have been made with kiln efficiency and waste fuels are now commonly used. However, during the production process, calcium carbonate decomposes into calcium oxide and carbon dioxide. This calcination reaction causes over half the CO2 emissions from the production process so there is limited scope for improvement. A number of initiatives have examined cement alternatives or replacement materials to reduce the Portland cement requirement of concrete. "Novacem" is an innovation from Imperial College London that made significant progress on a radical alternative to calcium-silica based cements based on magnesium oxide produced from magnesium silicates. Although these developments are encouraging, this process would require entirely new plant and with world production of cement at 2.5 billion tonnes per annum, this technology will take a long time to make a significant impact. Other initiatives such as "Ecocem" in Australia are based on cement replacement materials. A considerable amount of research and development of cement replacement materials has been carried out but replacement levels have specified maximum limits in current standards to ensure concrete behaviour does not differ significantly from Portland cement concrete. Fly ash is a by-product from coal-fired power stations which can be used as a partial cement replacement in concrete. It reacts with calcium hydroxide (produced during hydration of Portland cement) to form stable calcium silicate and aluminate hydrates - the pozzolanic reaction. Fly ash typically replaces 20% - 35% of the cement content within a concrete mix but there are obvious environmental benefits for incorporating higher proportions of cement replacement. However, the pozzolanic reaction between the fly ash and calcium hydroxide occurs quite slowly, which increases setting times and reduces the rate of strength gain of the concrete. This can cause problems associated with surface finishing, delayed removal of formwork etc. which can increase the cost and duration of a construction project. Researchers have consistently found that the higher the proportion of fly ash, the lower the early age strength of the concrete. Therefore, improvement of early age strength of fly ash concrete, particularly when incorporating high volumes of fly ash, warrants investigation. This project has been developed by Coventry University after detailed discussions with key industry figures representing cement, fly ash and admixture suppliers and concrete users. A comprehensive experimental programme will investigate the use of mineral activators to reduce setting times and enhance early age strengths of HVFA concretes. Cement kiln dust is a by-product of the cement manufacture process and its high alkalinity makes it a suitable activator of fly ash. Waste gypsum is also available in abundance and has been shown to increase the rate of strength gain of fly ash concrete. The aim of this study is to incorporate these by-products into HVFA concrete mixes to give comparable early age performance to equivalent Portland cement concretes. The effect of intergrinding the cementitious materials and activators will also be assessed. Also, a range of fly ash sources will be investigated to account for variations in chemical composition of the fly ash, which have been shown to affect concrete strength.