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Impact of drying rate on delayed strain behavior of cement-based materials - experimental and numerical study

Abstract : This work aims to contribute to the understanding of drying, shrinkage and creep mechanisms at the cement paste scale through innovative experimental tests, including drying rate and Pickett effect. Then, in the light of these results, the objective is to propose a model taking into account these hydric effects on the delayed behaviour of concrete.Firstly, an experimental campaign is carried out to study the effect of drying rate on creep and shrinkage. A difficulty in characterising shrinkage and drying creep is the cracking of the samples due to drying gradients within the sample. Thus, in order to isolate the purely "material" effects at the cement paste scale, it was decided to carry out shrinkage and creep tests on 2 mm thick cement paste samples. These microscopic tests were carried out: (1) under environmental scanning electron microscope (ESEM) at EDF R&D MMC and (2) in the Mini-Astrée biaxial tension-compression machine of the LMT at ENS Paris-Saclay, placed under climatic chamber with controlled CO2 concentration and monitored by an ultra high-speed camera. In parallel, a macroscopic campaign was undertaken on drying and pre-balanced samples at different relative humidities: 80%, 58% and 30%. These tests highlighted the decrease in basic creep kinetics when relative humidity decreases.Secondly, the objective of the numerical study is to propose drying, shrinkage and creep models that best integrate the impact of drying rate. A drying model taking into account the permeation of liquid water and the diffusion of water vapour has been adopted. It is demonstrated that this drying model allows the passage from the scale of the laboratory specimen to that of the structure. A very simplified shrinkage model is proposed and has been shown to be particularly effective in reproducing the drying shrinkage behaviour of samples of different sizes, drying at different rates. Finally, creep was studied: two models well known from the literature (Burger and MPS) are compared; it is shown that the Burger model is able to take into account the effect of size and drying rate on drying creep, which is not the case for the MPS model.
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Submitted on : Saturday, January 1, 2022 - 1:16:11 AM
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  • HAL Id : tel-03505908, version 1

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Justin Kinda. Impact of drying rate on delayed strain behavior of cement-based materials - experimental and numerical study. Génie civil. Université Paris-Saclay, 2021. Français. ⟨NNT : 2021UPAST020⟩. ⟨tel-03505908⟩

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