Comparative study of the long-term deflection of conventional and self-compacting concrete with light-weight concrete slabs

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Long-term deflection of concrete slabs is often the main governing design criteria to determine the appropriate thickness of the slabs to meet the required serviceability limit state. Due to the nonlinear nature of the material, predicting the long-term deflection of concrete structures is complex. Also, the complicated behaviour of concrete in the presence of reinforcement makes the problem more challenging to study. In general, codes of practice give an overall estimation of the long-term deflection as a multiplier of the short-term or elastic deflection of concrete structures. Such estimation sometimes may lead to an entirely wrong prediction of deflection and consequently unsafe, unrealistic and unprofitable concrete design and construction. Recent developments in concrete technology have led to produce new construction materials by significant strength and performance features. Many of these developments are engineered solutions to technical and commercial problems by either improvement of the current practices or overcoming of limitations in the existing construction technology. Lightweight and self-compacting concrete are the main two innovative concrete types used in the construction industry along with conventional concrete. This study examines and evaluates the time-dependent deflection of reinforced concrete one-way slabs made of two concrete types versus the conventional concrete. The presented investigation comprises both experimental and analytical components. The experimental part consists of laboratory investigation of the time-dependent flexural deflection and monitoring of the strains in reinforced concrete slabs. Since lightweight concrete is very prevalent in building construction in Australia, and there are limited studies on its long-term behaviour, the current study examines the lightweight concrete slabs identical to the previously tested conventional concrete slabs (Nejadi, 2005) and self-compacting concrete slabs (Aslani, 2014) subjected to the identical long-term loading. In addition, an analytical study consists of verification of the recorded experimental data and parametric study of the effective factors in the time-dependent behaviour and deflection of the conventional and self-compacting concrete slabs are conducted. Recently developed high-capable ATENA software is utilized in the numerical analysis. Load-deflection behaviour of the slabs under short-term loading is also recorded and compared with those of self-compacting and conventional concrete slabs. Finally, the results of this study are used to evaluate and verify the existing and proposed models associated with the parameters that affect the flexural deflection of reinforced concrete slabs with different types of concrete.
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