Experimental evaluation and modelling of early-age basic tensile creep in high-performance concrete

Accurate quantification of early-age tensile creep is vital to determine the stress build-up and the related crack sensitivity of concrete structures. Performing tensile creep testing in concrete is a challenging task and therefore reliable test data reported in literature is rather limited. The available test data indicates a large scatter and there is no consensus in the scientific community regarding early-age basic creep in tension. Besides, most of the prediction models in design codes are mainly calibrated using long-term compressive creep test data and their capabilities for predicting early-age tensile creep remain questionable. This paper first presents a comprehensive set of test data on early-age tensile creep of high-performance concrete using two unique methods, namely a Temperature Stress Testing Machine and a direct tensile test setup. The reliability of the collected data is demonstrated through the good agreement between the test data generated by these two test setups. Autogenous shrinkage measurements are performed simultaneously and used for determining basic tensile creep profiles. The governing factors affecting tensile creep including loading age, strength and temperature are experimentally explored in depth. The limitations of the widely utilized basic creep prediction model in the fib Model Code 2010 are identified. Based on the newly measured test data, modifications to the existing model are proposed. The proposed model better reflects not only the data collected in this study, but also that in other published data, thereby highlighting the capabilities of this model for accurate assessment of early-age basic tensile creep of high-performance concrete.