The effect of nitrogen-containing organic admixtures on the chemical processes of cement hardening
DOI:
https://doi.org/10.15587/1729-4061.2016.59505Keywords:
chemical additive, amide of terephthalic acid, cement hardening, alkaline environment, oversaturation of a pore solution, insoluble calcium terephthalate, crystallizationAbstract
Improved crystallization conditions for new hydrate formations can secure a dense, strong and minimally hard structure of cement stone and improve its building and technical properties as well as durability. This can be achieved by limiting oversaturation of the liquid phase of hardening cement while maintaining high concentrations of mineral-forming ions. Construction industry uses organic and inorganic additives for this purpose.
Since many studies are aimed at the search, purposeful synthesis or chemical recycling of industrial waste to obtain additives for cements, mortars and concretes, the topical problem is to study the mechanism of influence of the obtained compounds on cement hardening, which would provide a more selective approach to the methods of synthesis or chemical recycling.
We have studied the effect of additives on the chemical processes of cement hardening. The additive is a product of processing a polymer fraction of solid waste that consists of amides and ammonium salts of terephthalic acid. The use of additives intensifies milling, provides plasticizing effect, accelerates the setting and hardening time and increases the brand strength of cement in normal and low temperatures.
It is determined that the action of additives consists in the following: in a strongly alkaline environment of hardening cement, components of the additives are hydrolyzed to form insoluble calcium terephthalate, which reduces both the concentration of calcium ions in a pore solution and oversaturation with calcium hydroxide. This phenomenon accelerates the reaction of hydrolytic dissociation of clinker minerals to restore equilibrium concentration of calcium ions.
It is proved that such mechanism of action facilitates hydration of silicate and aluminate minerals of clinker, which accelerates the gel and crystalline phases, crystallization of hydro-silicates, and their conversion from high-base into low-base ones.
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Copyright (c) 2016 Ганна Юріївна Флейшер, Володимир Володимирович Токарчук, Валентин Анатолійович Свідерський
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