Uniaxial compression

The rupture tension by uniaxial compression is an indicative of the stone resistance to the shear when submitted to the load pressure, what normally occurs in structural functions.

The test of uniaxial compression is demandable for all the possible uses of an ornamental stone (vertical coverings, floors, steps and boards).

The evaluation essay is done on five test bodies, rectangularly shaped in dry state, according to the rules of the ASTM-C170, the results being expressed in kgf/cm2 or MPa.

Anisotropic stones and mainly the active ones, with placoid minerals defined structures (micas), tend to present distinct values for the rupture-strain, according to the axis position of the test body in relation to these structures. Isotropic stones, with fine or average granulation, are normally more resistant to rupture by uniaxial compression.

With the most modern techniques of fixation in vertical coverings, through metallic inserts, load accumulation does not occur between the plates. In more general terms and independently of the framing technique, a direct mathematical relation does not exist between the breaking strength of the materials and the recommended dimensions for the plates in the coverings.

What really exists is the indication of the health and firmness of the stones, with minimum values suggested by the ASTM, for the main lithological groups used in ornamentation and covering.

It is considered inconvenient, the parallel or transversal positioning of the scarfing/foliation plans of the anisotropic rocks, in relation to the compression axis alignment to which they will be submitted in a specified work.