Towards a New Analytical Creep Model for Cement-Based Concrete Using Design Standards Approach

Abstract

Creep properties are determined in design standards by measuring the creep coefficient, noted φ, as a function of time, t, and the age of the concrete at loading, t0. The work aims to study the validity of the analytical models proposed in the most used international standards and to check the possibility of their extension to estimate the creep of recycled aggregates concrete (RAC). A database was built from experimental results available in bibliographic references including 121 creep curves divided into 73 curves for natural aggregates concrete (NAC) and 48 curves for RAC. The comparison between the experimental and predicted values showed a significant dispersion for NAC and RAC. For the remediation of this dispersion, a new analytical model was developed for NAC. The parameters being the conventional creep coefficient, φ0, the power of the ageing function, named α, and βh, which accounts for the relative humidity and the compressive strength in the ageing function, were identified by inverse analysis. It was found that the power of the ageing function is 0.44 and not 0.3, as fixed by Eurocode 2 (EC2). Moreover, new expressions were proposed for φ0 and βh. The presence of recycled aggregates was considered through the equivalent replacement ratio.