Multicriterion optimisation approach in a design of cementitious composites with improved resistance to freezing/thawing

摘要

The presented experimental investigation forms part of a wider research programme directed to explore the microstructural properties of cementitious composites with improved resistance to freezing and thawing. A series of air-entrained mortars were subjected to alternating environmental conditions over a prolonged period of time. Significant alterations at the microstructural level resulting from the exposure to 480 cycles of freezing and thawing (F/T) were examined by means of the Mercury Intrusion Porosimeter (MIP) and the Scanning Electron Microscope (SEM). The pore size distribution gave evidence of the dominating range of pores being shifted towards the higher values of pore diameters. The MIP also indicated a significant change of a threshold pore diameter from 60 nm to 500 nm, which was followed by a concurrent decrease in the material's mechanical properties. In contrast to the previous investigations, it has been observed that the most vulnerable and therefore the most important pores are those with diameters between 100-1000 nm. The results of the microstructural analysis were ultimately utilised as source data for an optimisation procedure run with a Computer Aided Multicriterion Optimisation System (CAMOS).