Gypsum-based binder modified by clay has properties close to the gypsum binder and can be used as plaster formulations or mortars. There are several reasons and chief among them is the lack of scientific based theory of formation and hardening properties of gypsum-based binder modified by clay without additives and that modified by additives. One of the classic ways of studying the mechanism of hydration of gypsum binders is the analysis of the heat liberation: hydration heat of the binder. With the thermos method of determining the heat liberation the ambient temperature is constant and the temperature of the sample which was at the beginning of the experiment changes as a result of the released heat of hydration of the gypsum; heat exchange between sample and the environment. Heat transfer is minimized through the use of thermos technology and effective insulation. The article presents the results of studying the dynamics of heat liberation during hydration of gypsum-based binder modified by clay without additives, with addition of superplasticizer and with the addition of setting retarder. Results in all cases are satisfactory. The highest degree of hydration evaluated by kinetics of heat liberation from a binder is with the addition of the superplasticizer. Application of setting retarder somewhat reduces the maximum degree of hydration and increases the hydration time. The degree of hydration of the binder with the addition of C3 additive and retarder is observed to be higher than that of gypsum-based binder modified by clay without additives. The studies confirm the possibility of using gypsum-based binder modified by clay in the composition of dry plaster mixtures for interior decoration works in premises.
Clay-gypsum of each deposit are ecologically safe natural materials. They differ from others in their mineralogical and phase composition, they have different properties. Such a spread of properties of natural clay-gypsum, including after their heat treatment, makes it difficult to process them and, ultimately, use. The factor of "unpredictability of the obtained results" is one of the reasons why this type of natural composites are practically not used in modern construction. The paper presents the results of studies of the properties of model compositions of a clay-gypsum binder. The theoretical basis of the research is the methodology for the creation of new building materials, developed at the MSUCE. According to the proposed provisions, the properties of composite (or multicomponent) systems can be evaluated using the concept of a model body, in our case a "model material", manufactured with observance of certain technological parameters. According to the results of the first stage, the optimum temperature for calcination of an artificial clay-gypsum binder (which was 230-250°C) was established, and a graphical interpretation of the results was carried out using triple diagrams. By results of researches it is established, that the majority of natural structures in the natural state, or after modification can be used as a basis for reception of interior plaster mixes.
The applying of local building materials is an effective contribution to the savings of mineral resources, which are used for the production of basic building materials. Clay and gypsum compositions are the local raw materials in many regions of the country and some neighboring countries. The article discusses the method for determining the clay fraction in the clay and gypsum composition, as well as the method for assessing the rheological characteristics of the plaster mixtures for interior work based on clay and gypsum binder. It was established that the content of the clay fraction in the studied clay and gypsum composition is in the range of 30–32%. Plaster mixtures based on clay and gypsum binder can be considered as optimal compositions under the following conditions. The grade of mobility is not less than PK3 (8–12 cm) in cone penetration test, the ultimate shear stresses in the first seconds of the thixotropic hardening ensure no runoff for the adjusted thickness of the applied layer. With the mentioned mobility, the “creeping” on the concrete surface is 10% and less, and the “creeping” on the brick surface is no more than 5%. The allowable water-solid ratio is 0,46–0,50.
АННОТАцИЯ. Известково-белитовое вяжущее получают обжигом природных мергелей, мергелизованных или запесоченных известняков, а также искусственных кремнеземсодержащих смесей при температурах около 1000 °С с выдержкой 90 мин. Наряду с оксидом кальция вяжущее содержит значительные количества двухкальциевого силиката и некоторые другие минералы, состав и количество которых зависят от химического состава и температуры обжига используемого сырья. Однако оксида кремния недостаточно для образования в продуктах обжига сырьевого мергеля нужного количества белита, необходимого для получения высоких прочностных свойств. Основными целями работы являлись подбор состава исходных композиций и изучение химического и минералогического состава вяжущего на основе мергелей месторождений Акбурлы и Порлытау, чтобы повысить содержание белита (β-С 2 S) в продуктах термообработки и получения высокопрочного вяжущего. Для повышения содержания белита β-С 2 S в продуктах термообработки в состав сырьевого материала вводили 5, 10 и 20 % молотого кварцевого песка. Кварцевый песок измельчался до полного прохождения через сито № 008. Удельная поверхность находилась в пределах 2500…3200 см 2 /г. Показано, что константа основности с увеличением содержания песка уменьшается, а содержание алюминатов, ферритов и сульфатов кальция практически не изменяется, так как в составе песка отсутствуют глинистые составляющие. Результаты исследований совместной термообработки мергелей с молотым кварцевым песком предполагают, что оптимальное содержание песка в сырьевой смеси должно составлять 10 %. При таких соотношениях компонентов термообрабатываемого сырья происходят взаимодействия с образованием относительно наибольшего количества белита, который будет обеспечивать высокие прочностные свойства изделий на основе этого вяжущего.
The article substantiates using a modified binder based on clay-gypsum as the main component of dispersed reinforced and plasters mixtures. The rheological properties of such mixtures and the performance characteristics of plaster coatings have been studied. It is proved that the use of clay-gypsum as part of a modified dispersed reinforced binder contributes to the creation of favorable environmental conditions and the formation of a comfortable climate inside the agricultural premises, as well as increases the degree of protection of structures in fire conditions. It is established that the technological properties of dispersed reinforced plaster mixtures depend primarily on the composition of the modified clay-gypsum binder and the consumption of mineral fiber and its length. The fiber diameter within 3.2-3.4 microns does not significantly affect the properties of mixtures. Dispersed reinforcement in the range from 1 to 5% slightly affects the average density of clay-gypsum mixtures and plaster coatings based on them. Dispersed reinforcement has the greatest effect on the mobility of the mortar plaster mixture and, to a lesser extent, on its thixotropy. The introduction of mineral fibers has a significant impact on the strength characteristics of plaster coatings, and, to the greatest extent, on the strength of bending, the compressive strength is most affected by the content of semi-aqueous gypsum in the composite binder. An increase in bending strength by 20% determines the greater resistance of plaster coatings to temperature influence and this allows us to state an increase in the duration of the functioning of clay plaster barriers when protecting load-bearing structures and insulation systems from the effects of high temperatures.
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