Валентин Анатолійович Свідерський

The effect of nitrogen-containing organic admixtures on the chemical processes of cement hardening

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.

Utilization of the heat-treated silicate rocks in the cement and cement slurry manufacturing

Reliable operation of oil and gas wells depends largely on the quality of cementing. Currently lightweight cements with large water-cement ratio are used. To improve the properties of cement slurries we can use fine lightweight additives with the components, which are capable of reacting with the hydration products of clinker component to produce additional amounts of calcium hydrosilicates. An influence of the natural and heat-treated silicate rocks on the properties of cement and cement slurries is studied. It is found that the heat-treated silicate materials have a positive impact on the strength of cements and cement slurries. Research results show that strength of the samples, which contained heat-treated additives, higher than strength of the samples, which contain a corresponding amount of natural additives, at all concentrations of additives and all hardening time. The increased strength of cements and cement slurries based on heat-treated materials is provided, first of all, by reactive decomposition products of clay minerals. During the heat treatment of materials is not only the initial decomposition of minerals, but also the formation of new ones. However, this does not lead to deterioration in the rheological properties of cement slurries. Feasibility of using heat-treated silicate rocks as facilitating additives in the production of cements and cement slurries is confirmed under the conditions of factory laboratory. Cement slurry based on heat-treated kaolin clay meet regulatory requirements for such materials. Values of water separation, setting time, thickening time and bending strength are almost identical within the control bentonite clay-based sample, and the strength of cement slurry at the age of 180 days with the heat-treated additive nearly in 1,5 times higher.

Comparative analysis of the mineralogical composition of the natural chalk deposits of Ukraine

Using the methods of quantitative infrared spectroscopy and the X-ray phase analysis it is analyzed sedimentary chalk of five different domestic deposits compared to chemically precipitated and import calcite. Presence of calcite, dolomitic, aragonite in their composition is fixed. It is given a quantification of the content (for half-width within the 562-1047 cm -1 for imported calcite, 440-703 cm -1 for the national sedimentary chalk and 530 cm -1 for the chemically-deposited chalk, and the ratio of the intensities of characteristic absorption bands of carbonate anion respectively 10,38-45,33; 26,80-47,33 and 35,15) of the main structure minerals of these kinds of carbonates. It is received the data confirmation of IR spectroscopy by X-ray phase analysis of the main types of natural chalk and it is obtained quantitative structure of main content (calcite, dolomite) and extrinsic (quartz, kaolinite, iron hydroxide) minerals. According to the parameters of characteristic absorption bands in the range of 712-876 and 2512-2522 cm -1 modification of calcium carbonate - calcite – it is conducted differentiation of quantitative indicators, depending on the origin of the material. It is noted greater uniformity of mineralogical composition of import carbonates. These data allow formulate reasonable frameworks of use of domestic sedimentary chalk and assess its competitiveness compared with chemically-deposited chalk and Turkish calcite.

Purposeful modification of carbonate fillers for waterborne paints

In order to maximize the potential of Ukrainian carbonate deposits in composition of waterborne paints were studied properties and their possible for modification by mechanochemical activation in the presence of CH 3 Si(OH) 2 OK . Filtration coefficient, size of the effective specific surface, hydrophilic factor for initial and modified materials are determined during the work in the methodology of moistening research at leaking of polar and nonpolar liquids. Based on the data can be argued that the surface modification of carbonate by hydroalcoholic solution CH 3 Si(OH) 2 OK makes its surface less hydrophilic, increases dispersion, reduces the size of interparticle capillary, increases the effective surface area and will enhance the properties of the finished composite materials. Thus, investigations have shown that at filling of waterborne paints by carbonates of Ukrainian deposits is reasonable to conduct their preliminary mechanical activation using hydroalcoholic solution CH 3 Si(OH) 2 OK at a concentration of 0,5 % wt, because this treatment allows to bring the nature of carbonate surface to film former and improve moistening and distribution of the filler particles in the coating structure.

Дисперсність і морфологія природної крейди родовищ україни

Composition, morphology and dispersion of natural chalk in Ukrainian deposits are investigated. It is given their quantitative assessment in comparison with imported calcite production in Turkey. It is proved that granulometric parameters of domestic chalk are not inferior, and in some cases dominate foreign counterparts. It is established that the domestic chalk contain the fine-grained fractions with a minimum size of the particles that allows to create finishes on dense structure on its basis

Use of the admixture consisting of products of processed polymer fraction of municipal solid waste as a cement hardening accelerator

Досліджено вплив хімічної добавки на основі продуктів переробки полімерної фракції твердих побутових відходів, на процеси тужавлення та тверднення цементів. Виявлено, що добавка пришвидшує тужавлення і тверднення цементу за нормальних та низьких температур, а основний ефект від застосування добавки залежить від її концентрації, типу цементу та температурних умов.

Hardening peculiarities of blended cements with silicate admixtures of different origin

The influence of silicate-containing materials of different origin on cement properties was investigated. Selected mineral silicate-containing admixtures have significant differences in the chemical and mineralogical composition. It was found that the cement hardening rate is affected by the condition of silicate and aluminate admixture component. The presence of amorphous silica or glass in the admixture leads to a slow strength gain of cements in early hardening periods, and the introduction of heat-treated materials with high thermoactivated aluminate content into cements allows to significantly accelerate the process. Using natural silicate-containing materials (flask, tripoli, zeolite) in the production of blended cements is limited by high values of normal cement density that indirectly affects the ultimate cement strength. The study of the processes taking place in early hydration stages allows to evaluate the admixture effectiveness and predict cement properties. Kinetics of changes in pH of an aqueous solution of cements can be used as a criterion. Thus, introducing several admixtures that would have a positive impact on the sample strength in early hardening periods and grade cement strength is advisable in selecting compositions of blended cements. It was proposed to use rock dump processing waste of coal mining as a mineral admixture in cement production.

Influence of composition mineral additives on cement properties

The influence of silicate-containing materials of different origin on cement properties was studied. The selected mineral additives have significant differences in both chemical and mineralogical composition. It was found that the condition of a silicate and component admixture affects the rate of cement hardening. The presence of amorphous silica or glass in the additive slows down the cement strengthening in early hardening periods, while the introduction of heat-treated materials with a high content of thermally-activated aluminates to cement can speed up the process significantly. In this regard, a number of additives, containing the amorphous silica cannot be used as such in the production of composite cement. Adding them to the composition of the latter causes a significant increase in the cement paste normal density that will certainly leads to significant degradation of strength properties of hardened cement paste. The presence of a small amount of chemically inert solid minerals in the admixture material can improve the cement strength. Such materials can act as microfillers, thereby increasing the mechanical strength of samples. Thus, when developing the composition of composite cement, it is appropriate introducing several additives that would have a positive effect either on the strength of samples in early periods of hardening or the grade strength of cement. The wastes of recycling coal mining debris are proposed to be used as mineral additives in cement production.

Effect of alkohols as hardening-accelerating admixtures on the cement properties

The effect of alcohols as hardening-accelerating admixtures on physicomechanical properties of cement, particularly strength indexes in early hardening period is investigated. Alcohols can be used as an effective hardening accelerators of cement. The effectiveness of the influence of alcohols on the cement properties depends on their spatial structure and the number of hydroxyl groups. It was found that the largest increase in the cement strength is promoted by individual admixtures of alcohols with 2-3 hydroxyl groups (ethylene glycol and glycerol). Comparative analysis has revealed that alcohols behave as hardening accelerators only in the early periods (up to 3 days, especially on the 1st day), and known and widely used accelerator - calcium chloride, on the contrary, has no influence on the strength development on the 1st day of hardening, but contributes to a significant increase in strength on the 3-28 day. It was found that alcohols can be used as components of complex additives. The influence of alcohol on the cement strength in the complex additive “superplasticizer + hardening accelerator” was studied. It was found that the effectiveness of alcohols as accelerators is strongly affected by the components of complex additives since the best results were in modifying superplasticizer by ethanol, which had no significant effect on the cement strength as an individual additive. Alcohols are effective chemical additives that can be used as hardening accelerators, both individually, and as part of multi-component additives.

Influence of the nitrogen-containing compositions on the grinding process and physico-mechanical properties of cements

To utilize the waste, accumulated in Ukraine, and optimize the clinker grinding process, chemical additive, which is a product ofprocessing the polymer fraction of solid domestic waste was developed. The polymer fraction was used to obtain nitrogen-containing organic compounds, which have a significant influence on the clinker grinding process and physico-mechanical properties of cements and products based on them in the composition of additive.It was found that additive effectively influences clinker grinding processes within the concentrations of 0,045-0,065 wt % and has almost no impact on the process of grinding active mineral additives. The additive in a broader concentration range (0,025-0,085 wt %) increases the strength of composite cements in all hardening periods and accelerates the setting time.Additive, obtained by chemical processing of polymer fraction of solid domestic waste can be used in the construction industry as clinker grinding activator and cement strength increasing additive. Thus, it is possible to reduce the energy consumption in grinding technology operation and improve the physico-mechanical properties of composite cements, which in turn reduces the content of the cement component in such cements.