The aim of the research was to examine the possibilities
and ways of application of S. Z. Lewin’s method
in limestone reinforcement. The method constists in
limestone impregnation with the solution of carbamide
and barium hydroxide. As a result of the chemical
reaction in limestone pores the insoluble barium
carbonate is precipitated; it is to play the function of
the reinforcement. '
At the first stage of the research work the experiments,
as described by S. Z. Lewin, were carried out.
They dealt with the cementation of powdered chalk
in reinforcing solution. Results of these experiments,
however, proved to be a failure: after the six-month
period of impregnation the cementation of limestone
powder did not occur.
The second stage consisted in extending the scope of
the research. It included the influence of temperature
and duration upon the processes of barium carbonate
precipitation and limestone powder cementation
as well as the effects of the duration of impregnating
solution action on mechanical and physical
properties of limestone. Moreover, derivatographic
and X-ray structural analyses of impregnated
limestone were made.
As a consequence of the above experiments it was
stated that the efficiency of the process of barium
carbonate precipitation in room temperature was very
small ((about 26 per cent after 30 days). It increases
proportionally to the growth of temperature, being
sufficient at 95°C.
The increase of limestone strength was not stated on
the grounds of influence of duration of the solution
action (up to 3 months) in room temperature. Absorbing
and capillary capacities of limestone, however,
decreased and this proved the partial seal of limestone
pores caused by barium carbonate.
The application of barium hydroxide solution (free
of carbamide) brought similar results. In the latter
case the chemical reaction of barium hydroxide with
calcium carbonate took place.
The above-mentioned results were confirmed by
X-ray structural investigations.
It should be stressed that the cementation of limestone
powder and chalk did not occur although hardening
solutions of raised temperature (up to 95°C) were
being used.
Because of negative results of the tests carried out
we cannot apply S. Z. Lewin’s method in limestone
hardening. This method seems to be sufficient only
for protecting the stone against the destructive components
of atmosphere (chiefly S 0 2).
There are two possible explanations of this situation:
in his publications S. Z. Lewin did not make the conditions
of limestone hardening clear enough or he
might have used some additional substances which
caused crystalline barium carbonate to emerge. Crystalline
barium carbonate is capable of making crystalline
concretions with calcite. In this case both the
cementation of limestone powder and thereby reinforcing
of limestone should occur.
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