Particle packing of concrete containing blended cement

Physical particle packing is becoming a hot topic in concrete technology as more and more types of granular materials are used in concrete either for ecological or for engineering purposes. Aggregate is used as concrete’s skeleton, whereby the particles are stabilized by the cementitious matrix. Packing efficiency governs the spatial characteristics of this structure and thereby influences concrete’s properties. Fine-grained sand can be used to further improve density of the aggregate structure. The particulate cement is also frequently blended by fine mineral admixtures to influence performance of the paste and the properties of the matured concrete. The so-called filler effects increase packing density of the blended cement and possibly reduce water demand. High performance characteristics require suitable blending materials of proper properties (fineness, shape, chemical components, etc.).

A number of theoretical packing models have been proposed for prediction of packing characteristics and the resulting concrete properties. A minimum voids ratio has been mathematically derived for certain particle size distributions. This allowed establishment of some optimum graded mixtures for concrete production. On the other hand, the computer simulation approach provides a powerful tool for simulating particle packing. Computational concrete (compucrete) has been developed for a wide range of research purposes. Application of computer simulation to particle packing offers a promising perspective in concrete technology; it provides a proper representation of the heterogeneous concrete material, and renders the possibility of studying the effects of a wide range of technological parameters.

In this study, an advanced DEM will be utilized for investigate the packing properties of admixtures blended cement. This new-developed system is capable of packing simulations of arbitrary-shaped particles. Experimental shape analysis of each identical group of particles provides fundamental references of shape simulation strategy. Finally, computer simulation structures of blended cement paste both in fresh and hardened states will be compared with the experimental approach. Correlation of particle packing characteristics and properties of blended cement paste will be analyzed and discussed. Optimization of blending efficiency and improvement of concrete properties are pursued using packing modeling.