Ανάπτυξη μεθοδολογίας για την εις βάθος συσσωμάτωση χαλαρών εδαφών

Abstract

A new environmental friendly method, for the stabilization of loose soils to be used as building sites and for the amelioration of the properties of concrete constructions suffering from water leaks or humidity has been developed. The novelty of the proposed method is lying on the in situ precipitation of calcium oxalate monohydrate (COM) within the porous structure of soil or on the pore walls of the construction material (concrete) in order to minimize water leakage. Calcium oxalate, encountered often in kidney stones in the form of COM, is notorious for the formation of hard, non-porous aggregates which adhere tenaciously onto substrates. Calcium oxalate in the form of a protective patina is often met as surface layer in marbles or limestones. Mechanistic information concerning the formation of COM in supersaturated solutions may be obtained in seeded growth experiments. In these experiments, supersaturated solutions are seeded either with seed crystals of the same under investigation salt or of any other insoluble solid material on which the heterogeneous formation of the salt of interest may take place. Among the objectives of the present work was to investigate the role of concrete grains on the nucleation and crystal growth of COM. The analysis of the kinetics data showed that the prevalent mechanism for COM precipitation was surface diffusion. In all cases the only crystalline phase forming in the supersaturated solutions was identified as COM. In the second part of the present work the in situ precipitation of COM into mortar samples was studied. SEM analysis showed that crystallization indeed took place within the pores of the concrete. Best results in terms of waterproofing of concrete material were obtained in the case of treating concrete surfaces with sodium oxalate solution at high temperature.