Numerical Analysis of Moisture Flow and Concrete Cracking by means of Lattice Type Models

Modelling of fluid-flow and the resulting effects on shrinkage and microcracking by means of a combination of two lattice models are presented. For the moisture transport, a Lattice Gas Automaton (LGA) is adopted since it can effectively model moisture loss, whereas for cracking simulation a Lattice Fracture Model (LFM) is used. The resultant...

Effect of Different Bar Embedment Length on Bond-Slip in Plain and Fiber Reinforced Concrete

This research aims to study the behaviour of the concrete-steel bond using numerical models, taking into account the effect of the different bar embedment length. Both plain and fiber reinforced concrete (FRC) are modeled. The interface bond stress as well as load-displacement response of the reinforcing steel is studied. The asociated cracking...

Preliminary Investigation of Drying Shrinkage Cement Paste Specimens

In order to perform drying shrinkage observations in ESEM (Environmental Scanning Electron Microscope), a preparation procedure for cement paste samples is developed. Instead of casting standard prisms (40 x 40 x 160 mm3), cement paste samples were cast in specially designed moulds of 30 x 30 x 2 mm3 and 10 x 10 x 2 mm3 in size. A special...

Fracture Analysis of Beam-Column Joints due to Bond-Slip Mechanism

In order to predict a bond-slip behavior of the reinforcement bar in inner joint in a ‘seismic’ reinforced concrete frame structure, experiments and numerical analyses were conducted. A reinforced cylinder with a centrally embedded deformed rebar served as a simple joint model. The bar was fully loaded on a protruding end. Cyclic loading was...

Drying of Porous Media: Numerical and Experimental Approach

Drying of porous media, such as cement paste, is observed through different types of experiments at meso- and micro-scales. Important aspect is the transport of water through the porous material. The results from Nuclear Magnetic Resonance (NMR) drying experiments have been numerically modeled by means of Lattice Gas Automaton (LGA) from...

Study of Drying Shrinkage Cracking by Lattice Gas Automaton and Environmental Scanning Electron Microscope

Numerical modeling of moisture flow, drying shrinkage and crack phenomena in cement microstructure, by coupling a Lattice Gas Automaton and a Lattice Fracture Model, highlighted the importance of a shrinkage coefficient (?sh) as the most significant parameter for achieving realistic numerical results. Therefore, experiments on drying of cement...

Lattice Gas Automata: Drying Simulation in Heterogeneous Models

Moisture flow in porous media is the driving force behind early age drying shrinkage. Cracking in the ITZ, between cement paste and aggregate-inclusion, is related to restraint caused by, among others, aggregates that obstruct free deformation of the paste. ESEM test results are used as a base for the developed method for measuring shrinkage...

Study of ‘real’ shrinkage by ESEM observations and digital image analysis

Defining the 'real' shrinkage values of concrete is still a subject of much debate. In shrinkage experiments size effects are inherently present. Through an attempt to determine the real shrinkage of cement-based materials, these size effects have to be eliminated or at least reduced as much a possible. In this contribution drying shrinkage...

ESEM drying tests: Microcracking initiation in thin cement paste due to early age drying

Scattered and discontinues microcracking as a subsequent side-effect of deformations due to early age drying, occurs in thin (approximately 1 mm thick) cement paste samples, when stepwise dried in ESEM. Microcracking of cement paste and restrains appear to be practically unavoidable. They are related to a phenomenon of interfaces (‘matrix’ and ...