How to measure path length?

Path length measuring is a relevant engineering problem. Leonardo Da Vinci designed for the military appropriate equipment, the podometer, to do so. Modern equipment such as step meters and map meters are quite similar to Da Vinci?s design, despite geometrical statistical - stereological - methods based on theorems of Cauchy and Buffon that were...

Packing of non-spherical aggregate particles by DEM

Loose random and dense random mono-size pacl<ing states were investigated by the discrete element modelling (DEM) for eight types of polyhedral grains, for ellipses with different aspect ratio, for cubes and for spheres. Focus was on density, sphericity of the grains and average value and frequency distribution of coordination number. The 3D...

Analogue simulation by dem of material structure for property estimation of cementitious materials

Realistic simulation of particulate materials like concrete on meso- as well as micro-level is nowadays possible by fast developments in computer technology. This would be a more economic way than by physical experiinents, which are more time-consuming, laborious and thus expensive. This concern the production of the aggregate structure or of...

Brazil Nut Effect and CONCRETE: Entering Terra Incognita

This paper presents some evidence of the impact of the Brazil nut effect (BNE) on concrete’s particulate structure on meso-level (aggregate) as well as on micro-level (cement paste). BNE is associated with long-range size segregation in particle mixtures due to vibration in slurry state of concrete, both near boundaries and in bulk. Presented...

Particulate structure and microstructure evolution of concrete investigated by DEM: Part 1: Aggregate and binder packing

Experimental approaches in concrete technology are time-consuming, laborious and thus expensive. Developments in computer facilities render possible nowadays realistically simulating the particulate structure and microstructure of cementitious materials. For that purpose, discrete element methods (DEM) are required because of more correctly...

Particulate structure and microstructure evolution of concrete investigated by DEM: Part 2: Porosimetry in hydrating binders

Durability of concrete in engineering structures is becoming more and more of a major problem. Research into such problems is complicated and expensive, however. Developments in computer technology make it possible nowadays realistically simulating cementitious materials and studying its pore network structure. In this paper use is made of the...

Discrete element modeling approach to porosimetry for durability risk estimation of concrete

The paper introduces a novel approach to porosimetry in virtual concrete, denoted as random node structuring (RNS). The fresh state of this particulate material is produced by the DEM system HADES. Hydration simulation is a hybrid approach making use of wellknown discretization and vector methods. Particle interferences (overlap) in the dynamic...

Numerical assessment of concrete damage: Procedures and pitfalls

The paper focuses on the quality of predicting the damage characteristics of the loaded engineering structure by subjecting section images of cores supposedly drawn from the concrete of the structure to quantitative image analysis by sweeping test lines. Automation of this data acquisition stage is shown, generally leading to information that is...

Low-cycle compression fatigue of reinforced concrete structures

Paper reports on experiments performed in the low-cycle compression fatigue domain, considering two relatively high upper load levels and several lower ones. Two frequency levels were emphasized, i.e. 17.5 Hz and 0.175 Hz. An overview is given of characteristics of mechanical behaviour and of the state of damage close to fracture. Particular...

On a micro-meso two-scale damage model for concrete

In this contribution, we present the mechanical behaviour of the hardening cement paste explicitly taking into account its complex microstructure. The microstructure of the cement paste is obtained via numerical cement hydration simulation. A simple nonlocal isotropic damage model is adopted for different constituents of the cement paste. The...

Modern routes ro explore concrete's complex pore space

This paper concentrates on discrete element computer-simulation of concrete. It is argued on the basis of stochastic heterogeneity theory that modern concurrent-algorithm-based systems should be employed for the assessment of pore characteristics underlying durability performance of cementitious materials. The SPACE system was developed at Delft...