Barbara Klemczak

Prediction of Coupled Heat and Moisture Transfer in Early-Age Massive Concrete Structures

The issues connected with the determination of thermal and moisture fields in early-age massive concrete are discussed here. The coupled equations, which govern the heat and mass transfer in early-age mass concrete as well as the initial and boundary conditions are presented. Next, the discretization in the space was made using the finite element method; the finite difference method was introduced for the discretization in time. As a result, the matrix form of the heat and moisture transfer equations was obtained. The proposed model was implemented in the original computer program TEMWIL, which can be applied to spatial massive structures in order to forecast the temperature and moisture distribution. Essential thermodiffusion coefficients for early-age concrete were also discussed. Finally, some computations concerning different curing conditions for the massive foundation slab were presented.

Comparison of Analytical Methods for Estimation of Early-Age Thermal-Shrinkage Stresses in RC Walls

Abstract The volume changes caused by coupled temperature and moisture variations in early-age concrete elements lead to formation of stresses. If a restraint exists along the contact surface of mature concrete against which a new concrete element has been cast, generated stresses are mostly of a restraint origin. In engineering practice a wide range of externally restrained concrete elements can be distinguished such as tank walls or bridge abutments cast against an old set foundation, in which early-age cracking may endanger their durability or functionality. Therefore, for years methods were being developed to predict early-age stresses and cracking risk of externally restrained concrete elements subjected to early-age thermal-moisture effects. The paper presents the comparative study of the most recognised analytical approaches: the method proposed in EC2, the method proposed by ACI Committee 207 and the method developed at the Luleå University of Technology.