Influence of Crystallization Additives on Morphology of Selected Benzoic Acids - A Molecular Dynamics (MD) Simulation Study

The possibility to modify the morphology by crystallization additives of model substances was studied using molecular dynamics simulations. For this 2,6-dimethoxybenzoic acid and 3-hydroxybenzoic acid, each having two polymorphic forms, including a form without carboxylic acid homodimers in their crystal structure were selected. For each polymorph 2-3 largest crystal faces were selected for the study and the crystal was cut along these planes by preparing a simulation box with these planes facing towards solution containing additives. In the performed study it was evaluated which additives potentially can influence the crystal morphology and possibly also polymorph obtained in the crystallization by significantly changing the growth rate of crystal by adsorbing on the surface. For the study 4-5 additives providing different intermolecular interaction possibilities were selected. Among the studied additives urea showed the most complete adsorption and the longest residence time on surfaces of both substances, with the exceptions of few specific planes.

Analysis of the Effect of Crystallization Additives on the Resistance of Self-Compacting Concrete Exposed to Aggressive Gases

The article deals with the influence of crystallization additives on the life of self-compacting concrete (so-called SCC concrete), which are exposed to chemically aggressive environments. The focus is not only on the effect of the crystallization additive on the characteristics of the capillary-pore structure of SCC concrete, but especially long life durability of self-compacting concrete (two years expozition). The effect of individual types of aggressive environment is assessed on the basis of a set of physico-mechanical and physico-chemical analyzes.