Electrophysical parametres of process of
consolidation of concrete, as diagnostic sign of quality of products.
ENÓ of
L.N.Gumilev. Kablbekova Otkir Mominovnaà
The constant
control of process of consolidation of a concrete mix since the mixing moment,
on the one hand, reduces a spoilage in production and raises efficiency of
management, and other party opens possibilities of use of not destroying
quality monitoring.
It is known that, process of
structurization of a concrete mix is accompanied by
humidity change. After linkage of the
most part of a moisture the concrete structure represents dielectric with the
conductors-grains distributed inside.
The basic
electric property dielectricîâ is their ability to polarisation in a range of
high frequencies of electric field. About ability dielectricà to be polarised judge on increase in capacity of
the condenser at a premise between its facings of it dielectricà [1].
If between condenser facings
we will place polar dielectric turn of not elastic dipoles are late concerning
pressure change on size of time relaxation
Thus, the displacement
current (Iñì) is caused by electronic polarisation characterised
by reduction of the maintenance of a free moisture causing occurrence and
growth of a capacitor component, and an absorption current (Iàá) - dipol. Besides,
in dielectricå exists through òîê
|
Ià Iñì U
Fig. 1. The vector diagramme |
Fig. 2. Electric chain R, L, C, fed with pressure U=UmSinωt |
Corner δ, supplementing to 90º a corner of phase shift
between a current and pressure, name a
corner of dielectric losses. A tangent of a corner of dielectric losses,
as it follows from the vector diagramme (a Fig. 1), it is possible to calculate
under the formula (1)
Because of presence of current
As
According to researches of
dielectric structures of consolidation of a concrete mix it is possible to
notice, that with reduction of humidity conductivity of concrete has complex
character: one cases it is accurately expressed in time, in others on it
process of destruction of structures is imposed. In the first ïðèáëèæåíèé it is possible to present a concrete mix in the
form of an electric chain with the concentrated parametres from active
resistance (R) and jet (L and C) elements (a Fig. 2).
Really,
concrete mix containing a significant amount of a free moisture in an initial
stage of consolidation, has active conductivity with small value of inductance.
This results from the fact that the channels filled with water with the minimum
impurity, are a conductor therefore the network of conductors in the semiisolating
environment is formed. Such structure possesses basically active conductivity,
at the expense of the channels forming through structure with some inductance
at the expense of directed in volume of the sample of magnetic fields. In
process of chemical linkage of water channels (time) are divided by dielectric
stoppers êðèñòàëëîãèäðàòîâ both air and the conductivity current decreases,
decreases also inductive components. Reduction of the maintenance of a free
moisture causes occurrence and growth of a capacitor component by corresponding
currents of displacement. After linkage of the most part of a moisture the
concrete structure represents dielectric with the conductors-grains distributed
inside, with the moisture rests in a spending time and with prevalence jet -
capacitor conductivity. At the same time, presence of residual humidity does
not exclude possibility of occurrence of vortical currents with the advent of
some inductance and active conductivity [3].
Fig. 3. A window of the task of parametres.
According to experimental
researches [4], a curve And (t) (hydration degree) for cement well describes
above specified circumstances: gradually reduction of quantity of a free
moisture involves respective alteration of the general conductivity. Its
practical value consists that on an initial site defined by experiment
dependence And (t) it is possible to define parametres of process and to
predict its further course.
Thus, in process of reduction of humidity conductivity of concrete
has complex character, and it can be represented in the form of a vector of
complex resistance Z (7) with angular factor φ (8).
By data schemotechnical modelling of an electric chain resulted on
fig. 2 in system Mikro-Cap8, it is established that, accurate nonlinearity of
complex resistance Z is shown in a range of frequencies, from 2 to 7 ÌGz.
Fig. 4. Schedules AFR and FFR
Results of frequency researches are resulted on fig. 4. On which
schedules peak-frequency (AFR) and fazo-frequency (FFR) researches, and also
parametres of their imaginary and valid part for construction ãîäîãðàôà are resulted.
Thus, on the bases
theoretical and experimental researches, it is possible to confirm that,
characteristic splashes in parametres the consolidations revealed in an initial
stage (which continuation can will last in currents of 6 and 8 hours it agree
fig. 4, occur in a range of high frequencies characterised by dielectric
properties of structure and new growths.
It is necessary to notice
that, ãîäîãðàô complex resistance in the
course of consolidation are in dependence from structure and humidity of
concrete. Change of module Z in time characterises humidity change.
Thus, the information about
êèíåòèêå changes ïðî÷íîñòíûõ characteristics of a processed material, receive already at an initial
stage of process that creates possibility of correction of its course.
The literature
1. Pavlov P. V,
Crests À.Ô. Physics of a firm body. - Ì: the Higher school, 2000.
2. Kabilbekova
U.M. Forecasting of durability of easy concrete designs
Under their electric characteristics at
early stages of consolidation. Ì: Works
MADY. 1990.
3. Kabilbekova
U.M. Matematicheski modelling êèíåòèêè a durability set
Building products on easy fillers. Architecture and building, 2002