The effect of dispersion of dirt particles in oils on their electrical conductivity and mechanical strength

It has been shown theoretically and confirmed experimentally that the dispersion of dirt particles found in engine oils and working fluids affects significantly their physical properties. In particular, it has been established that if dirt particles are artificially dispersed in a lubricant, its electrical conductivity increases. This, in turn, is expected to lead to a decrease in the share of electrostatic wear of the tribo units. Such particles are also able to increase the mechanical strength (surface tension) of lubricating films, that is, to make the boundary layers more durable, due to which we can expect a decrease in wear of tribo units. In this case, the thermal conductivity of oil lubricating films with highly dispersed dirt particles does not change.

Increasing the Durability and Freeze-Thaw Strength of Concrete Paving Stones Produced from Ahlat Stone Powder and Marble Powder by Special Curing Method

This study highlights an investigation of using construction waste materials, i.e., Ahlat stone powder and marble powder, in fabricating interlocked paving stones. In this study, the durability and freeze-thaw strength of concrete paving stones produced from Ahlat stone powder and marble powder were increased by the special curing method. Six different types of paving stones were fabricated for study and were subjected to two different curing regimes. Tests of water absorption, splitting tensile strength, surface abrasion, and freeze-thaw were carried out for the specimens. In 3 days and at 20 ± 5°C of water curing, the splitting tensile strength was 3.7 MPa, the surface abrasion value was 9.8 cm3/50 cm2, and the freeze-thaw value was 0.39 kg/m2 for those interlocked paving stones produced from Ahlat stone powder. After special combined curing, these improved to 3.9 MPa, 17.2 cm3/50 cm2, and 0.63 kg/m2, respectively. Accordingly, for interlocked paving stones produced from marble powder, in 3 days and at 20 ± 5°C water curing, the splitting tensile strength, surface abrasion, and freeze-thaw were 3.9 MPa, 7.9 cm3/50 cm2, and 0.34 kg/m2, respectively. After special combined curing, these values improved to 4.1 MPa, 14.8 cm3/50 cm2, and 0.57 kg/m2, respectively. The findings of this study validate increase in durability and freeze-thaw strength of concrete paving stones with special curing.