АНАЛИЗ ВЛИЯНИЯ ТОРФЯНЫХ МОДИФИЦИРУЮЩИХ ДОБАВОК НА СВОЙСТВА МИНЕРАЛЬНЫХ ВЯЖУЩИХ МАТЕРИАЛОВ

The paper describes an assessment of peat hydrophobic additive influence on properties of the modified portland cement.  Content of organic and mineral components in the investigated materials has been determined in the paper. An increase of durability of the modified cements is caused by higher dispersion of particles during mixed grinding of clinker and additives. The developed method allows to isolate cement from influence of liquid-drop and vaporous moisture. Isolation is carried out  by means of  binding  solid particles of  a modifier being from several dozens to hundreds of nanometers in size with cement particles, and also due to processes which occur at the nanolevel when  cement is treated by liquid components of hydrophobic modifying additive. Interaction between dispersive cement phase and molecules of organic additive is carried out into practice by hydrogen bonding formation of surface silanol groups of cement particles with oxygen-containing groups of additive. Dispersion non-specific (van der Waals) interaction contributes to adhesion energy of “cement – additive” system.  The paper shows that covalent forces are not formed during additive molecule adsorption on the surface of dispersive cement phase.Проведена оценка влияния торфяных гидрофобных добавок на свойства модифицированного портландцемента. Определено содержание в исследуемых материалах органических и минеральных компонентов. Повышение прочности модифицированных цементов вызвано увеличением дисперсности частиц при совместном помоле клинкера и добавок. Разработанный метод позволяет изолировать цемент от воздействия капельно-жидкой и парообразной влаги. Изоляция происходит посредством связывания твердых частиц модификатора размером от нескольких десятков до сотен нанометров с частицами цемента, а также за счет процессов, происходящих на наноуровне при обработке цемента жидкими компонентами гидрофобно-модифицирующей добавки. Взаимодействие между дисперсной фазой цемента и молекулами органической добавки осуществляется путем образования водородных связей поверхностных силанольных групп частиц цемента с кислородсодержащими группами добавки. Дисперсионное неспецифическое (Ван-дер-Ваальсовое) взаимодействие также вносит определенный вклад в энергию адгезии системы «цемент – добавка». Ковалентных связей при адсорбции молекул добавки на поверхности дисперсной фазы цемента не образуется

Scientific basis of a new method for hydrophobic modification of mineral binders using peat products

This study deals with the issue of caking of mineral binding materials during storage and transportation. The author conducted a critical analysis of known methods for the protection of cement from exposure to moisture and water vapour. Common disadvantages of these methods are their low effectiveness and complexity of use in industrial and domestic environments. This article introduces a new method for hydrophobising construction materials using peat, which achieves high water repellency in the modified materials with relatively low expenditure on organic materials. The author proposes film coating of the mineral particles of dispersed hydrophilic materials as a protection mechanism against their undesirable exposure to moisture during storage. The insulating film consists of hydrophobic products (bitumens) released during thermal decomposition of the organic matter in peat. The estimated thickness of the bitumen film is about 12 nm and it does not adversely affect the flow properties of the powder. A model of the formation of film coatings on mineral particles is provided and their elemental chemical composition is determined. It is shown experimentally that the modified hydrophobic cement is protected from exposure to liquid vapours, and optimal values of organic component concentrations in the dispersed mineral matter that do not reduce the strength of cement mortar are identified

The hydrophobic modification of gypsum binder by peat products: physico-chemical and technological basis

Gypsum binder is a quick-setting and fast-hardening material that is used widely in the construction industry for plastering and as an ingredient of concrete, other binding materials, etc. The issue addressed here is its short shelf life (around three months) which arises because it is hygroscopic, i.e. it readily absorbs moisture and begins to set during transport and storage. The main methods that are currently available for protecting gypsum binder against unwanted exposure to moisture and water vapour are considered, and hydrophobic modification with the bitumen released during peat thermolysis (a method previously considered for cement) is proposed as a promising alternative. Because there is overlap in the temperature ranges used in the manufacture of gypsum binder and those required for the initial stages of thermal decomposition of the organic matter in peat, it is expected that hydrophobisation could be achieved during the established manufacturing process without any changes to plant or procedures. The optimum concentration of organic (peat) additive for gypsum rock mined from the Shushokskoye deposit in Russia is derived experimentally. With 0.5–1 % of peat additive, the strength grading of the gypsum plaster is preserved and its storage time without caking and hydration increases, even under adverse conditions (100 % relative humidity). The proposed method is compatible with current gypsum production technology, it does not require any changes in equipment, and the prices of mineral raw materials and semi-finished peat products are approximately the same. Thus, the incorporation of hydrophobic modification using peat into the manufacturing process for gypsum binder is unlikely to increase the cost of the product

ANALYSIS OF PEAT MODIFYING ADDITIVE INFLUENCE ON PROPERTIES OF MINERAL BINDING MATERIALS

The paper describes an assessment of peat hydrophobic additive influence on properties of the modified portland cement.  Content of organic and mineral components in the investigated materials has been determined in the paper. An increase of durability of the modified cements is caused by higher dispersion of particles during mixed grinding of clinker and additives. The developed method allows to isolate cement from influence of liquid-drop and vaporous moisture. Isolation is carried out  by means of  binding  solid particles of  a modifier being from several dozens to hundreds of nanometers in size with cement particles, and also due to processes which occur at the nanolevel when  cement is treated by liquid components of hydrophobic modifying additive. Interaction between dispersive cement phase and molecules of organic additive is carried out into practice by hydrogen bonding formation of surface silanol groups of cement particles with oxygen-containing groups of additive. Dispersion non-specific (van der Waals) interaction contributes to adhesion energy of “cement – additive” system.  The paper shows that covalent forces are not formed during additive molecule adsorption on the surface of dispersive cement phase