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The mechanical performance and durability of hardened granular- cement paste material such as mortar and concrete are affected by its earlier stage behavior which is defined in terms of consistency and/or workability. Therefore understanding the behavior of the mixture during this early period is a crucial requirement for the technical and economical success of professional production sites. This paper presents a numerical approach based on Discrete Element Method (DEM) to simulate the macroscopic behavior of a fresh granular-cement paste mixture in which the pasty behavior is dominant. The research approach is based on a conceptual idea where the particle-paste interaction system is explicitly modelled by means of a two phase particle interaction system. The effect of the characteristics of paste on the macroscopic fresh behavior of a mixture has been studied and compared by the mini slump cone test regarding the excess paste theory. Modelling and experimental laboratory test results show good agreement.

For developing a unique model in which the rheological performance of fresh concretes from zero-slump to self compacting concrete can be described, it is necessary to define workability in terms of fundamental physical entities. In order to achieve this, the concept of capillary cohesion from science of granular physics has been considered as the first step for investigation. In this paper, focus is on this concept and providing some preliminary achievements of the experimental work. In wet granular material the presence of liquid generates cohesion between particles and affects the mechanical properties of the granular media to a large extent. For the simulation of the behavior of this material by considering pendular state for liquid content, a discrete element method (DEM) is used. The cohesion between a grain-pair is expressed as an explicit function of local geometrical and physical parameters. In this study emphasis is on static and/or quasi-static situations. Since the cohesion dominates over other effects of the liquid, such as viscosity and lubrication, the effect of the size of particles on the cohesion arising from the liquid bridge is investigated explicitly. Based on experimental results, a closed-formula approximation is developed that can be used to calculate the capillary force acting between two glass spheres as a function of the separation distance for a given bridge volume.

The slump test is a very important industrial test for evaluation of workability of fresh granular-cement paste material, especially concrete. The test method is used as a generic tool for classification of a wide range of mixtures and can deal with a wide range of workabilities. The current paper presents a numerical approach, based on Discrete Element Method (DEM), with the aim to study the effect of the mix composition on the rheological behavior of a mixture after demolding, i.e. lifting the slump cone. The research approach is based on a conceptual idea, where the particle-paste interaction is explicitly modelled as an interactive two phase “paste –particle” system. Each mixture is considered to consist of these elements with the rheological behaviour characterized by the “excess paste” model. Simulations and experimental laboratory test results show good agreement.