Results of the theoretical analysis of experimental diagrams of deformations of columns made of wood sawdust and concrete mixtures and of wood sawdust and gypsum mixtures exposed to uniaxial compression are provided in the paper. The findings of the prototype testing include identification of the two areas of deformations: areas of elastic deformations and areas of intensive development of deformations. The first area of partial elastic deformations is characterized by the linear stress function, while the second area demonstrates that this relationship is nonlinear. Permanent deformations appear as of the startup of the loading process and disproportionate stress is demonstrated throughout the deformation process. However, in the first area (partial elastic deformations) residual deformations are so small that this area is considered as the area of "the area of incomplete elasticity".