Concrete carbonation, as it is well known, is one of the major causes which affect the concrete durability. The carbonation on the fresh concrete in the first days of its hardening determines the structure deterioration and especially reinforcement corrosion. The main consequence of carbonation process is a reduction of the pH value, which leads to the reinforcement depassivation and its corrosion.
In the paper are examined the carbonation process in old construction realized in Romania in 1888-1921 in correlation with their mechanical properties. For comparison have been chosen a relative new building which was damaged in 1977 at earth-crack and a standard concrete sample realized in 2005.These buildings were chosen because they are representatives for the beginning to use the concrete in construction in our country (1900-1915) and a lot of these construction still be in good shape.
Carbonation process were evaluated by the carbonation depth and carbonation degree in the concrete. global carbonate content was quantitatively determined, by selection, using chemical, roentgenographical and thermal methods. The result obtained on each sample represented media of three cores-samples.
paper tries to contribute to understanding the connection between carbonation process of the concrete and its physical-mechanical properties, respectively its durability. Also one evidences the importance of binding composition and mineralogical nature. A higher content of belite in the Portland cement has appositive influence upon concrete durability and particularly upon rate of carbonation.
Often in the concrete samples appears agglomerate of crystals of calcium carbonate as calcite and waterite, as a compact layer which improve mechanical properties. Calcium carbonate crystals are fixed in the superficial pores and filing these as a protective layer - clogging layer. Thus the CO2 diffusion inside of the concrete is stopped and concrete present a high durability and the physical-mechanical properties of the concrete are not negative influenced.