HR: 1340h
AN: H53E-1459 [WITHDRAWN]    [Abstracts]
TI: Numerical and experimental studies of drying and shrinkage induced microcracking in concrete
AU: * Jankovic, D
EM: dj32826@yahoo.com
AF: TU Delft, Stevinweg 1, Delft, 2628 CN, Netherlands
AB: The aim of this research is to investigate moisture flow in cement paste and Interface Transition Zone, around aggregate, as well as associated shrinkage induced strains, and subsequent microcracking. Two coupled methods are used: numerical simulations and experiments. The moisture flow is numerically simulated by Lattice Gas Automata, while drying experiments are performed in Environmental Scanning Electron Microscope (ESEM) in order to determine drying deformations and shrinkage coefficient. The moisture movement simulation by Lattice Gas Automata, a type of cellular automata, involves different drying collision rules, which results in different density (moisture content) at each node. Special attention is given to the effect of the presence of aggregate particles on the moisture flow in concrete, which are considered rigid obstacles. The shrinkage deformation is considered a linear function of the moisture content if the relative humidity, RH does not exceed 40%. The calculated moisture gradient from the numerical analysis and an assumed shrinkage coefficient are used to calculate drying shrinkage induced strains and stresses using the basic equations. To determine the drying shrinkage coefficient for the RH range 100% to 20%, new experimental techniques of drying in ESEM are used. Small paste samples are cast in a specially developed mould with 2 mm thickness and afterwards carefully grounded and polished to a thickness of required 1 mm. The used variables in the tests are: various cement types, w/c ratio, sample age and curing conditions. Drying shrinkage displacements and strains are determined in order to calculate the drying shrinkage coefficient. These experimentally obtained values of the coefficient are compared with the literature data and used in numerical simulations of shrinkage induced strains, stresses and cracking in drying concrete.
DE: 1800 HYDROLOGY
DE: 1847 Modeling
SC: Hydrology [H]
MN: 2007 Fall Meeting