3.5. Influence of technology factors
3.5. Influence of technology factors
Химические и минеральные добавки в цементы и бетоны - Синайко Н.П.
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Thus, the
anti-freeze admixture promotes decrease of crystallization temperature of a
porous liquid, quantity of ice, volume of pores and reduction of their sizes.-
without the admixture; 2 and 3 -1 % and 2 % of the admixture
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name=bookmark52>3.4. Intensification of hydration
Complex admixture
intensifies and deepens hydration of cement. It is developed in propagation of
indexes of speed and completeness of heat evolution (fig. 4). In particular, duration of an induction period contracts at increase of
concentration from 1 up to 2 % from 1,75 without the admixture up to 1,7 and
1,65 h, accordingly. Values of the basic exo-effect and hydration heats grow
from 37 without the admixture up to 38 at 1 % and 44cal/g at 2 % of the
admixture.
3.5.
Influence of technology factors
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name=bookmark54>3.5.1. The water-solid ratio
Propagation W/S
from 0,3 up to 0,7 promotes increase of the sizes and expansion of area of
distribution of pores. At W/S=0,3 the fine-pored structure of a cement stone
with pore sizes from 2 up to 5 nm is formed. Increase of W/S up to
0, 7 results in formation of pores in a range 12,3... 122 nm due to the
exuberant water-contents. Presence of SAS in composition of the complex
admixture allows to provide necessary rheological behavior of a concrete mix at
W/S=0,3, that it is important not only from the point of view of improvement of
physical-mechanical properties of concrete, but also from positions of
reduction of negative influence of a frost in conditions of winter
concreting.Temperature effect of concreting on an ice formation at freezing a
cement stone is reflected with the data of fig. 5.
With reduction of
temperature the quantity of ice at freezing a cement stone grows that is caused
by retardation of hydration. Decrease of speed of an ice formation in an
interval of temperatures 0... 10°C is caused by structural change of water.
Below 0°C speed of an ice formation monotonously grows with reduction of
temperature.
Introduction of the anti-freeze admixture promotes reduction of quantity
of formed ice at all temperatures. The most intensive ice formation occurs in
temperature range 5...-15°C. On other interval of temperatures speed of an ice formation is low fidelity identical and
averages 2,5 mg/g-°C.
The carried out experiments
have allowed constructing of forecasting model of concrete properties at use of
the given complex admixture in dependence of concreting conditions and its
concentration (fig. 6). As the determining factor the quantity of formed ice
was chosen. On model possible minimum and maximal deviations of parameters of
an ice formation also are submitted.
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name=bookmark55>Conclusions:
Researches of
influence of the complex anti-freeze admixture on character of concreting and
gelation of a cement stone and concrete have shown, that it