3-D Virtual Mortar and Concrete Model at Mesoscale

Concrete is a multiscale and multiphase heterogeneous construction material. Regular concrete is made from coarse aggregates (e.g. crushed stones, river gravels), fine aggregates (e.g. sands), cement and water. A chemical reaction starts immediately when water is mixed with cement, and reaction products are produced. The resulting cement paste keeps aggregates together and forms a system which is able to carry loads. Typical, mortar consists of cement paste and sand, and concrete is composed of mortar and coarse aggregates. From the cross-scale modeling point of view, the material mesostructures of both mortar and concrete can be represented by particles embedded in matrix material model. The particles are considered as sands, and the matrix as cement paste for mortar model; while the particles are coarse aggregates, and the matrix is mortar in the concrete model. Hence it is applicable to make a universal material mesostructure model for mortar and concrete.

However, the particle shape characterizations can be different for sands and coarse aggregates, and furthermore they are different for various classes of sands or coarse aggregates. This requires the universal material model to be able to recognize various particle shape characterizations. It is shown that spherical harmonics is a good mathematical tool to characterize the shape of particles numerically, and the procedures to retrieve particle shape characterizations for a given class of aggregates from CT (computational tomography) scanned digital images are also established [1]. The following procedure is to place multiple irregular shape particles into a customized empty container (geometrical domain) to build up a complete particles embedded in matrix material model. An application of the proposed material model is given bellow, for the purpose of modeling the mesostructures of mortar and concrete respectively.

3-D stone-based material modeling using real particles represented by spherical harmonic expansions

The particle parking algorithm for star-shaped particles that has been developed can be useful in many ways. One way is to use the algorithm to place real-shaped particles in a box to create a microstructure. For many materials, one would rather be able to pack the particles in the box, but for concrete, the sand and gravel particles form a suspension in the cement paste matrix, and are in general not touching. This work is performed using stored shape databases of sand and gravel particles of various sources.

Front view of virtual cement concrete model after random packing