Macroscopic effective mechanical properties of porous dry concrete

The pores and voids within concrete have a great influence on the macroscopic elastic modulus, strength and other mechanical properties of concrete. The present study determines the macroscopic mechanical properties of porous dry concrete composed of hollow void inclusions embedded in a concrete matrix. Based on a three-phase sphere model, the effective bulk modulus of a concrete composite with a hollow sphere in concrete matrix is obtained. The investigation on the influence of porosity on the effective shear modulus of porous dry concrete is carried out by using a hollow cylindrical tube model. Based on the assumption that the material is isotropic, homogeneous and elastic, the effective Young's modulus and Poisson's ratio of porous concrete composites are derived. A comparison between the elastic modulus and Poisson's ratio derived from the present model and those from open literature indicates a good agreement. Furthermore, on the basis of the developed simplified analytical model, the quantitative effect of porosity on the macroscopic effective tensile and shear strengths of porous concrete in dry state are studied. Besides, their corresponding effective peak strains when porous dry concrete reaches its macroscopic effective tensile/shear strengths are also investigated and discussed. Also a comparison between the available tensile strength and two classical solutions is made to verify the rationality and accuracy of the present approach. The consistent results indicate that the proposed approach can predict the effective mechanical properties of porous dry concrete well, and the formulas are simple and convenient to use.