Staff

Abstract:
The kinetics of heat transfer in hardening concrete is a key issue in engineering practice for erecting massive concrete structures. Prediction of the temperature fields in early age concrete should allow for proper control of the construction process to minimize temperature gradients and the peak temperatures, which is of particular importance for concrete durability. The paper presents a method of identification of the thermophysical parameters of early age concrete such as the thermal conductivity, the specific heat, and the heat generated by cement hydration in time. Proper numerical models of transient heat conduction problems were formulated by means of finite-element method, including two types of heat losses. The developed experimental–numerical approach included the transient temperature measurements in an isolated tube device and an in-house implementation of an evolutionary algorithm to solve the parameter identification task. Parametric Bezier curves were proposed to model heat source function, which allowed for identifying such function as a smooth curve utilizing a small number of parameters. Numerical identification tasks were solved for experimental data acquired on hardening concrete mixes differing in the type of cement and type of mineral aggregate, demonstrating the effectiveness of the proposed method (the mean-squared error less than 1 °C). The proposed approach allows for the identification of thermophysical parameters of early age concrete even for mixtures containing non-standard components while omitting drawbacks typical for classical optimization methods.

Keywords:
early age concrete, evolutionary algorithm, inverse solution, heat transfer problem, mass concrete, thermal properties

Abstract:
In this paper, the evolutionary computation procedures for identifying thermophysical properties in hardening massive concrete structures are presented. The heat of cement hydration, thermal conductivity and specific heat are determined for the purpose of modeling temperature evolution in massive concrete elements. Knowledge about temperature fields is very important due to their link with undesirable thermal stresses that can cause a weakening of structures because of thermal cracking. The proposed method is based on point temperature measurements in a cylindrical mould and the numerical solution of the inverse heat transfer problem by means of the finite element method and evolutionary computation

Keywords:
thermal properties of concrete, inverse heat transfer problem, early age concrete, evolutionary algorithm, FEM

Abstract:
The evolutionary computation procedures in identification of thermophysical properties of hardening concrete in massive structures are presented. Heat of cement hydration, thermal conductivity and specific heat are determined for purpose of modelling temperature evolution in massive concrete elements. The knowledge of temperature fields is very important due to a link with undesired thermal stresses, which can cause a weakening of the structure because of thermal cracking. The proposed method is based on point temperature measurements in a cylindrical mould and the numerical solution of the inverse heat transfer problem by means of finite element method and evolutionary computation

Keywords:
heat of cement hydration, inverse heat transfer problem, early age concrete, evolutionary algorithm, finite element method, thermophysical properties of concrete