.
.
Химические и минеральные добавки в цементы и бетоны - Синайко Н.П.
150 
The
dependencies dQ/dx=f(x) and Q=f(x) are objectively reflect of the admixtures
influence on a rate and completeness of heat evolution. At the same time, these
data are explicitly not enough for a quantitative estimation of effectiveness
of admixtures effect. Therefore, as indexes of such estimation it is expedient
to accept the following criteria.
Depending on
effect of admixtures influence the values of kj and k2 can be
positive and negative, i.e. testify about intensification or retardation of
hydration.
In tab. 1 the
results of thermokinetic analysis of clinker mineral and cement hydration are
analyzed with use of the offered criteria at the presence of the individual
admixtures (fig. 2).
The values of
thermokinetic indexs and criteria correlate with data about effectiveness of
plasticizing and water lowering of cementitiuos mixtures. So, maximal negative
value of criterion ki - more than 50 % - corresponds to the greatest effect of
a water-contents decrease - down to 27% - in mixtures, owing to introduction a
plasticizing component of a system “Relaxol”.
The information
of thermokinetic and technological character accumulates in computer databanks
for a decision making at selection and adjusting of compositions of concrete.
In tab. 2 thermokinetic indexes of hydration of Portland cement at the presence
of different combinations of the admixtures of a system are resulted.
The table data
testify possibilities of regulating of indexes of a hydration rate and
completeness by variation of relations of components. A choosing of required
properties, necessary for reaching, of mortar and concrete are manufactured in
view of this information. The duration of an induction period is connected with
duration of saving of rheological properties of concrete mixture. For example,
xind increases from 4,7 for a control sample to 6,5 h for
combination # 3. Thus the negative values of criteria ki and k2 are
maximum, and the amount of heat for 24 h
- 24,2 cal/g - is minimum. Character of hydration indexes at the presence
of a admixtures combination “the accelerator - stabilizer” is other. The values
ki and k2 are positive, and t^j reduces practically to 4 h.
Even more high
level of information of thermokinetic analysis data for a justification of the
admixtures choice, their concentrations and relation in complexes composition
is ensured by mathematical simulation of an estimation of admixtures influence.
On fig. 3 the diagrams of dependencies of criteria ki and k2
On the basis of
the physical-chemical and mathematical approaches, given in this report, within
the framework of an information technology of concrete “Thermobet” /5/ the
compositions of the chemical admixtures of a system “Relaxol” and
recommendation for their application are offered on thermokinetic analysis data
and results of physical-mechanical trials. Their effectiveness confirms by
results of an water-need estimation (fig. 4) and strength trials (fig. 5). The
digital labels correspond to tab. 2.