Environmental concerns arising from the over-dredging of sand have led to restrictions on its extraction across India, with direct economic impacts on concrete construction. A suitable environmentally friendly alternative to sand must be found to match the huge demand from the concrete construction industry. At the same time, waste plastic is rarely recycled in India, with as much as 40% left in landfill. The dumping of such materials which degrade at extremely low rates meaning they persist in the environment is a long-term environmental concern. To tackle both issues, it is proposed to process waste plastic to create a partial replacement for fine sand in a novel mix for structural concrete. In this paper eleven new concrete mixes are evaluated to study five plastic material compositions, three groups of particle sizes, three different aspect ratios, and two chemical treatments and establish an appropriate choice of material to act as partial replacement for sand. The results show that replacing 10% sand by volume with recycled plastic is a viable proposition that has the potential to save 820 million tonnes of sand every year. Through suitable mix design the structural performance of concrete with plastic waste can be maintained. This preliminary work was supported through funding from the British Council under the UKIERI (United Kingdom India Educational Research Initiative) programme for the project 'Development of structural concrete with the help of plastic waste as partial replacement for sand'.

This paper describes the outcomes of recent research that is, for the first time, aiming to completely replace internal steel reinforcement in concrete structures with knitted prefabricated cages made of highly durable fibre reinforced polymer (FRP) reinforcement. The proposed manufacturing technique, based on the filament winding process, allows the reinforcement to be fabricated in a precisely calculated geometry with the aim of providing tensile strength exactly where it is needed. The resulting Wound FRP (W-FRP) cage designs capitalise on the extraordinary flexibility and lightness offered by FRP construction materials. This paper presents fundamental analytical and experimental studies that demonstrate the effectiveness of the wound reinforcement system and forms the basis of future efforts to develop fully automated manufacturing methods for concrete structures.

The winding of Fibre Reinforced Polymer (FRP) tows around longitudinal reinforcing bars provides a novel method for the fabrication of reinforcement cages for concrete structures. A key limitation on the contribution of FRP to the shear capacity of a concrete member is found at corners, where stress concentrations can lead to premature failure. An experimental programme, comprising 30 test samples, was undertaken to assess the bend capacity of filament wound FRP (W-FRP) shear links manufactured using a carbon tow impregnated with epoxy resin. A new methodology was developed to allow for rapid testing of the samples as well as their self-realignment during load application. A fixed bend radius of 5mm and six non-circular fibre cross sectional areas having different width-thickness ratios were considered. Additionally, 18 samples were tested to measure the tensile properties of the straight reinforcement. The results indicate that W-FRP exhibit improved bend strength as compared to conventional FRP with circular sections, as a larger width-thickness ratio of the reinforcement provided more strength for a given cross sectional area. A good correlation between the test results and predictions of the W-FRP bend strength was observed when the specimens were modelled as a collection of transformed individual circular sections.

The built environment accounts for 39% of global energy related CO2 emissions, and construction generates 13% of global GDP. Recent success in reducing operational energy and the introduction of strict targets for near-zero energy buildings mean that embodied energy is becoming the dominant component of whole life energy consumption in buildings. One strategy that may be key to achieving emissions reductions is to use materials as efficiently as possible. Yet research has shown that real buildings use structural material inefficiently, with wastage in the order of 50% being common. Two plausible mechanisms are 1) that some engineers hold individual misconceptions, or 2) that inefficiency is a cultural phenomenon, whereby engineers automatically and unquestioningly repeat previous methods without assessing their true suitability. This paper presents a survey of 129 engineering practitioners that examined both culture and practice in design relating to material efficiency. The results reveal wide variations and uncertainty in both regulated and cultural behaviours. For the first time, we demonstrate that embodied energy efficiency is not a high priority, with habitual over-design resulting in more expensive buildings that consume more of our material resource than necessary. We show wide variability in measures that engineers should agree on and propose research through which these culture and individual issues might fruitfully be tackled within the timeframes required by climate science.

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a b s t r a c tCodes of practice rely on the effective length method to assess the stability of multi-storey frames. The effective length method involves isolating a critical column within a frame and evaluating the rotational and translational stiffness of its end restraints, so that the critical buckling load may be obtained.The non-contradictory complementary information (NCCI) document SN008a (Oppe et al., 2005) to BS EN 1993-1 (BSI, 2005) provides erroneous results in certain situations because it omits the contribution made to the rotational stiffness of the end restraints by columns above and below, and to the translational stiffness of end restraints by other columns in the same storey.Two improvements to the method are proposed in this paper. First, the axial load in adjoining columns is incorporated into the calculation of the effective length. Second, a modification to the effective length ratio is proposed that allows the buckling load of adjacent columns to be considered. The improvements are shown to be effective and consistently provide results within 2% of that computed by structural analysis software, as opposed to the up to 80% discrepancies seen using the NCCI (Oppe et al., 2005).

This paper explores the potential of thin concrete shells low-carbon alternatives to oor slabs and beams, which typically make up the majority of structural material in multi-storey buildings. A simple and practical system is proposed, featuring pre-cast textile reinforced concrete shells with a network of prestressed steel tension ties. A non-structural ll is included to provide a level top surface. Building on previous experimental and theoretical work, a complete design methodology is presented. This is then used to explore the structural behaviour of the proposed system, rene its design, and evaluate potential carbon savings.Compared to at slabs of equivalent structural performance, signicant embodied carbon reductions (53-58%) are demonstrated across spans of 6-18 m. Self-weight reductions of 43-53% are also achieved, which would save additional material in columns and foundations. The simplicity of the proposed structure, and conservatism of the design methodology, indicate that further savings could be made with future renements.These results show that considerable embodied carbon reductions are possible through innovative structural design, and that thin-shell oors are a practical means of achieving this.

By replacing conventional concrete moulds with flexible sheets of permeable fabric, the construction of optimised concrete elements that provide material savings of up to 40% when compared with an equivalent strength prismatic member is possible. This paper details the results of recent tests undertaken at the Building Research Establishment Centre for Innovative Construction Materials at the University of Bath that demonstrate significant additional durability advantages for fabric-cast concrete. Using accelerated test methods, 50% average reductions in both the non-steady state chloride diffusion coefficient and carbonation coefficients were found when comparing concrete samples cast against permeable and impermeable surfaces. Sorptivity, surface hardness and scanning electron microscopy tests demonstrate further beneficial changes in the fabric-cast concrete. The combined results demonstrate that fabric formwork may be used to create structures optimised for strength and durability. Notation B j coefficient of carbonation for formwork type j C a, j depth of carbonation for formwork type j at time a (mm) C i initial chloride content (% by mass of concrete) C i, j depth of carbonation for formwork type j at time i (mm) C r reference chloride concentration (0 . 05 mass%) C s calculated chloride content at exposed surface (% by mass of concrete) C x,t chloride content measured at depth x and exposure time t (% by mass of concrete) D nss non-steady state chloride diffusion coefficient (m 2 /s) K Cr chloride penetration parameter t a time of exposure in carbonation chamber (days) t i time of exposure to atmospheric conditions (days) ç correlation factor between accelerated test conditions and in-situ results (dimensionless)