Evaluation of static and dynamic behaviour of fibre reinforced concrete incorporating polypropylene fibres

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This thesis represents a systematic study on the behaviour of special engineered concrete material and its behaviour in the structural elements. The approach of this research has been to create an innovative material which is beneficial to the improvement of the structures and infrastructure and at the same time produce an environmentally friendly concrete by using Fly ash and polymeric waste material. Using polypropylene (PP)fibre and Styrene Butadiene Latex (SB latex)polymer, different mix designs of fibre reinforced concrete (FRC), polymer modified concrete (PMC) and fibre reinforced polymer modified concrete (FRPMC) have been studied. At first stage of the project, material characteristics of each engineered concrete mix design is evaluated and tested. This initial study led to a comprehensive understanding of the behaviour of FRC, PMC and FRPMC using PP fibres and SB latex. Generally, using SB latex in the concrete mix without the addition of any anti-foaming agents or any other modifier, especially at higher percentages, lowers the mechanical properties of concrete. This phenomenon is of more attention where fibres are used together with the SB latex in the mix. In FRCs, the matrix mechanical characteristics are enhanced at specific percentages which led us to choosing some of the best mix designs for the structural studies. In terms of the dynamic properties of the concrete mix, for example the damping ratio, PMC and FRPMC showed good behaviour and as a result, from among many, one best mix has been chosen for the dynamic structural testings. Two types of PP fibres have been used in this project namely the monofilament and fibrillated PP fibre with the length of 18 mm and 19 mm, respectively. Amongst the monofilament fibres, 0.25% volume of the mix showed promising results and between different percentages of fibrillated fibre, 1% fibre is chosen for the structural testing. Reinforced beams have been constructed to evaluate the structural behaviour under 4 point static loading and 3 point cyclic loading. Two types of mentioned FRCs as well as the two reference concrete mix designs were used for the static beam testing. With regards to the cyclic testing, again the two references as well as the two FRCs had been prepared and tested. At the same time a PMC beam and an FRPMC beam was prepared to be tested under the cyclic loading. Results of the structural tests show that by adding higher percentage of the fibre to the mix, the ductility of the structural beam is enhanced more than in case of using lower percentages. In the cyclic tests, each cycle has been evaluated separately and also all cycles together. Results indicate that where elastomeric materials are present in the mix i.e. PP and SB latex, the damping ratio of the first cycles are much higher than the conventional concrete. This is beneficial due to the serviceability loading areas. The principal conclusion can be that by adding higher percentage of fibres, the structural behaviour of concrete beam can be enhanced in terms of both static and dynamic characteristics.
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