2014-02-17
850
В Б.Ратинов и Т.И. Розенберг разделили ускорители твердения по механизму действия условно на четыре класса:
1. изменяющие растворимость вяжущего и вступающие с ним в химическую реакцию;
2. химически взаимодействующие с вяжущим с образованием труднорастворимых соединений;
3. являющиеся центрами кристаллизации
4. ПАВ, адсорбирующиеся на зернах вяжущих и новообразованиях.
К добавкам первого класса относятся соединения различной природы (электролиты, неэлектролиты), изменяющие пересыщение в растворе, а следовательно и скорость гидратации и твердение вяжущих материало. Неэлектролиты (например, спирты), химически не взаимодействуя с исходным и конечными фазами, обычно только понижают их растворимость и поэтому относятся к числу замедлителей твердения.
Добавки второго класса образуют в результате химической реакции с вяжущими и продуктами их гидратации труднорастворимые вещества или малодиссоциированные комплексные соединения.
Добавки третьего класса, являясь кристаллическими затравками, облегчают выделение новой фазы из пересыщенных растворов, поэтому их введение целесообразно в тех случаях, когда лимитирующей стадией твердения является скорость кристаллизации новообразований.
Четвертый класс составляют органические ПАВ, позволяющие при их добавлении в очень малых количествах значительно изменять свойства цементного камня, а иногда и придать ему некоторые новые.
The Lecture 11 FHS.
Subject: Colloidal-chemical phenomenas in technologies astringent
The Inorganic astringent- material (in the manner of тонкодисперсных powder usually, capable at mix with water (shutterring) form plastic-viscous mass (the dough), which gradually solidifies, превращаясь in strong камневидное body.
We shall Consider the factors, conditionning пластичность вяжущего test, theories of the repeating over and over again astringent, influence of the additives on processes of the repeating over and over again, phenomenas смачивания and адгезии.
Plastichnosti вяжущего test. The Astringent at mix with water (or the other затворителями) forms practically uniform пастообразную mixture - вяжущее dough. This dough presents itself высококонцентрированную суспензию particles вяжущего (powder) in liquids, which on Rebinderu, possible consider the твердообразной by liquid. Vyazhuschee dough capable under influence external mechanical influence be deformed without breaches сплошности and save the got form, when action of external power is stopped. Such characteristic is identified the пластичностью of the test. Under good пластичности masses to operations of her(its) mix, stowages, формования and compactions speed up and are reduced the price of. Using it is enough plastic masses promotes also increasing to density and homogeneity of the final products that favourable tells on their physical, chemical and mechanical characteristic.
Repeating over and over again astringent. Repeating over and over again i.e. conversion plastic вяжущего test in hard камневидное body, results from chemical processes, specific for each вяжущего. We shall Consider the general scheme of the mechanism гидратационного repeating over and over again. In process of the repeating over and over again is accepted distinguish two periods: схватывание and repeating over and over again.
The Beginning схватывания corresponds to the moment, when вяжущее dough begins загустевать and loses пластичность, but together with her and тиксотропную ability. Hereinafter, the dough changes in землисто-friable hard body, which does not possess essential toughness that corresponds to the end схватывания. Herewith runs the inconvertible chemical interaction source component with formation new высокодисперсной hard phase with each other and conversion грубодисперсной гетерогенной systems in микрогетерогенную colloidal-дисперсную system.
The Clarification of the mechanism гидратационного repeating over and over again astringent long ago attracted attention of the researchers. One of the first theory of this process was кристаллизационная theory Le-SHatelie (1882) designed by him on example of the description полуводного sulphate calcium (gypsum вяжущего). On Le-SHatelie, the astringent s with water, forming join, greatly differring on characteristic from source material. Later, преждложена colloidal theory (In Mihaelis, In Ostvalid, L.M. Blyumen,1892). On this theories process formation гидратных phases occurs the топохимически - as a result of interactions of the molecules of water with surface small part mineral phases, being included in вяжущего in consequence of which it is formed colloidal mass - коагуляционная structure, consisting of the most small particles гидратных phases. Toughness of the system grows on measure of the increase degree compactions helium, which constantly increases to account of the continuinging collecting to liquids by surface of the hard particles, as well as as a result of loss влаги in consequence of высыхания.
A.A.BAYKOV has offered the theory of the repeating over and over again (1923), in which were taken into account glances and the main positions as кристаллизационного, so and colloidal mechanism of the shaping to toughness.
M.M.SYCHEV in process of the repeating over and over again essential role conducts physico-chemical condition of water on miscellaneous stage shaping the structure. Under гидратообразовании surrface energy of the system vastly increases to account of the increase to specific surface that does the system unstable.
The Influence of the additives on processes of the repeating over and over again astringent.
In B.RATINOV and T.I. Rozenberg have separated the boosters of the repeating over and over again on mechanism of the action on four classes conditionally:
1. changing растворимость вяжущего and enterring with him in chemical reaction;
2. chemical interacting with вяжущим with formation труднорастворимых join;
3. being centre to crystallizations
4. SUNG, adsorbing on grain вяжущих and new formation.
Joining the different nature pertain To first-class additive (the electrolytes, неэлектролиты), changing пересыщение in solution, but consequently and velocity гидратации and repeating over and over again вяжущих материало. Neelektrolity (for instance, alcohols), chemical not interacting with source and final phase, usually only lower their растворимость and so pertain to count;calculate;list замедлителей of the repeating over and over again.
The second-class Additive form as a result of chemical reaction with вяжущими and product their гидратации труднорастворимые material or малодиссоциированные complex join.
The third-class Additive, being crystalline затравками, relieve the separation of the new phase from пересыщенных solution so their introduction in that events reasonable, when limiting stage of the repeating over and over again is a velocity to crystallizations of the new formations.
The Fourth class form organic SUNG, allowing under their accompaniment in very small amount vastly to change the characteristic cement stone, but sometimes and add him some new.
