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

Abstract

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.

Simulation of chemo-thermo-mechanical problems in cement-based materials with Peridynamics

“…where A T represents the ratio of the maximum value of the heat production rate to the latent hydration heat for a normalized definition of the hydration function [1,29,32], the damage variable / affects the heat during hydration reaction as assumed in [29]. Moreover, E a is the activation energy characterizing the rate of heat generation and R ¼ 8:314 Â 10 À3 kJ K À1 mol À1 is the ideal gas constant.…”

“…Generally, there are many ways to choose this specific function e.g. a piecewise linear or exponential approximation of the experimental data [1,20,29,33,71]. In the present study, the power form of the evolution function, f ðaÞ, for the normalized heat production rate is considered as presented in [1,29,32]:…”

“…Cement hydration and shrinkage is a phenomenon characterized by inhomogeneous stresses occurring in plain and non-reinforced concrete. Concrete is widely used in infrastructures such as airfields, slabs and dams [1]. A significant disadvantage of concrete is its sensitivity with respect to the early-age cracking in aforementioned structures.…”

“…A significant disadvantage of concrete is its sensitivity with respect to the early-age cracking in aforementioned structures. Hence, a basic understanding of material performance due to early-age cracking is required in the design of concrete structures [1,2]. Due to the fast change of mechanical properties such as strength of the material [3,4], prediction of the behaviour of concrete is still not a trivial task.…”

“…Other numerical approaches such as microplane approach in [27] or lattice approach in [28] are used to investigate the early-age concrete behaviour. Soon afterwards, Neguyen et al [1,29] have proposed a phase field model to investigate complex fracture induced by early-age shrinkage and hydration heat in cement based materials. Other numerical methods in this field can be traced in [30][31][32].…”