We analyse the process of gravitational collapse using Press-Schechter theory in order to predict the existence of Primordial Black Holes, PBHs, using the Josan’s restriction and the latest cosmological parameters measured by Planck satellite. Assuming a gaussian fluctuation on the perturbation in the early Universe, we find that PBHs with mass M > 1012 kg, have not evaporated yet. Comparing with the mass fraction PBH = 10−20 and assuming that the PBHs energy density should not exceed the Cold Dark Matter, CDM, energy density, we constraint the spectral index (blue espectra) to ns < 1.4 and obtain a value of the power spectrum P ≈ 10−2.

The continuous population increase in recent years requires a greater number of households to be built quickly, with good materials and produced under quality standards that guarantee their manufacturing process. The prefabricated concrete, produced and supplied by concrete plants, is poured into the different structural elements, the mezzanine slabs being the most careful surfaces in the appearance of fissures; because being horizontal and having larger dimensions, the dimensional changes in the concrete appear more frequently due to the rapid loss of water from the surface of the concrete before setting; which generates superior stresses to the resistant capacity of the concrete at early ages, which affect the durability and reduce the resistance of the structures, causing greater economic expenses in maintenance and repairs. In the present investigation, 5%, 10% and 15% of rice husk a...