Experimental and numerical analysis of early age behavior in non-reinforced concrete

in Construction and Building Materials (2019), 210

An approach combining numerical simulations and experimental techniques is proposed to investigate the early-age properties of non-reinforced concrete. Both thermo-mechanical and fracture behaviors are ... [more ▼]

An approach combining numerical simulations and experimental techniques is proposed to investigate the early-age properties of non-reinforced concrete. Both thermo-mechanical and fracture behaviors are studied, providing a deep insight into the hydration process. This work makes an important step in understanding the effects of hydration on the performance of cement-based materials. More specifically, in the first part, the shrinkage and fracture properties of a non-reinforced concrete have been experimentally considered, along with the characterization of several material parameters. The experimental results exhibit a high risk of early-age cracking for this kind of concrete. Especially, the fracture phenomena are complex, including multi-evolution-stages, initiation, propagation, stop-growing, and re-growing. In the second part, the computational modeling based on the phase field method of failure mechanism is applied to simulate the thermal, mechanical and fracture behavior due to early-age hydration. A detailed discussion on the identification of model/material parameters and the construction of numerical model including the boundary conditions is given. We provide the following comparison between predictions of the numerical simulation with the experimental observations. An excellent predictive capability of the computational model is noted. More importantly, this work demonstrates the performance of the proposed approach, which requires only a few tests to identify the model inputs. Most of the chemo-thermal parameters can be theoretically determined based on the concrete mix and the chemical/mineral compositions of the cement. [less ▲]

Concept to predict crack initiation and crack development in fairfaced concrete screeds

in Beushausen, Hans (Ed.) Performance-based approaches for concrete structures (2016, November)

Within a research project of the Laboratory of Solid Structures of the University of Luxemburg, a design concept to predict cracks in various concrete structures will be developed. The current paper ... [more ▼]

Within a research project of the Laboratory of Solid Structures of the University of Luxemburg, a design concept to predict cracks in various concrete structures will be developed. The current paper presents the numerical investigation of crack initiation and crack development of an unreinforced cementitious fairfaced concrete floor. Thereby cracking of concrete is divided into cracking of an early stage and into cracking of a later stage. The present study deals with cracking of an early stage. Taking into account shrinkage and the chronological strength development of the used C20/25 concrete and with the use of the Element Failure Method (EFM) it will be possible to predict, within a Finite Element Analysis, a possible crack path spatial as well as temporal. For this purpose a finite element model, based on a commercial FE-Software is developed. The program is tested on H-shaped concrete specimen with an unfavorable size ratio between surface and volume. Besides, shrinkage on this specimen is hindered so that unplanned restrain forces has to occur. Using an algorithm the finite element program is able to calculate the model gradually for several load steps within a loop. Furthermore the net dependency of the EFM can be excluded by the use of suitable load steps. [less ▲]

Untersuchung der Rissentwicklung an zementgebundenen Sichtestrichen

in Beton (2016), (66), 248-252

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