**1. Introduction**

Attention to the quality, durability and rapid construction process is one of the major challenges for the concrete industry. Prediction of the temperature field in concrete objects allows us to use the proper care of young concrete as well as to estimate development of compressive strength. In the case of massive structures, it is particularly important to not exceed the temperature difference between the interior and the concrete surface. Too high temperature gradient generates an increase in thermal-shrinkage stresses, what could be the reason of exceeding the tensile strength and as a consequence cracking occurrence [1]. Knowledge about the temperature distribution is important not only for the type of construction discussed above, but also for medium-weight and thin-walled concrete elements, for which time is a major factor to achieve the required strength to start prestressing or formwork removal. The temperature field in concrete combined with maturity method equations gives the possibility to estimate concrete strength changes over time and space [2,3].

In recent years, there has been growing interest in rationalization of the building schedule. Supporting the process of designing, curing and monitoring concrete features with the use of computer technologies, provide a lot of benefits, especially for contractors [3,4]. ElSafty et al. [5] developed the complex tool (The Deck Cracking Spreadsheet) to predict the early-age cracking of concrete bridge

decks. The thermal aspect of concrete hardening is described there using time-dependent parameters. The concrete heat of hydration is calculated based on the concrete mixture proportions and the constituent material properties. The detailed input data in this tool can improve temperature forecast. However, the developed spreadsheet is limited to the decks with thickness about 20 cm and there are no analysis comparing the measured and predicted temperature evolution of concrete bridge deck [5].

The key aspect in the prediction of temperature distribution of cast-in-place (CIP) concrete is the choice of the numerical model, which should be consistent with the measurement capabilities. The multi-field mathematical models of young concrete [6,7] are well documented in a literature, but very often an application of the theoretical formulations are adopted only at the laboratory level. The major problem is that there are many constants that cannot be determined under field conditions. Therefore, the main purpose of this work is the determination of thermophysical model parameters of CIP concrete for numerical modeling of concrete temperature distribution in the bridge deck, as a part of the service offered by the Structural Health Monitoring (SHM) system.

The well-defined model parameters and initial-boundary conditions corresponding to the real environmental conditions at the construction site are the basis of reliable predictions of the in-place concrete temperature distribution. In this paper, two thermo-chemical models of hardening of concrete [8,9] were used. The heat flow equations were solved with the finite difference method in Matlab environment. The preliminary calculations of temperature evolution in bridge slab were published in the works [10,11], wherein the selection of model parameters based on the literature. A novel element of the paper is a complex proposition to identify model parameters and boundary conditions i.e., the heat transfer coefficients of free and protected concrete surfaces. Numerical simulations were confirmed by concrete temperature data measured on the construction site of extradosed bridge located in Poland. An own monitoring system was applied to register the advancement of hydration reaction of high performance concrete, C 60/75 class. Based on the temperature field and augmented maturity method, the dates of prestressing of individual sections of bridge deck, was also determined.
