Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~ 21107-182
A_~y Mortar Mixture
The present invention relates to a dry rnortar mixture
for coating vertical, horizontal, or inclined surfaces, this
mixture comprising a-t least one inoryanic, hydraulic or non~
hydraulic bonding agent and, optionally, at least one additive,
a plastic that is in powder form, dispersed in liquid, or in
liquid form, an additive to increase resistance to freezing and
freeze-thaw cycling, a colouring agent, fibres or other addition-
al additives, for example, natural or artificial pozzuolane,
blast-furnace slags or conventional concrete additives such as
liquifiers, pouring agents, sealants, corrosion inhibitors, and
the like, in association with a granular additive that increases
alkalinity and which has a much lower reaction speed than the
inorganic bonding agent.
Increased surface damage has been noted in structures,
particularly those of concrete, this damage being caused by the
increased diffusion of CO2 and SO2 from the atmosphere into those
zones that are close to the surface of the concrete. The diffu
sion of CO2 leads to carbonisation, to a subsequent loss of
alkalinity, and finally to corrosion of steel within the concrete.
The diffusion of So2 leads to the formation of gypsum or
ettringite and thus to undesirable blowing of the cement. These
problems are exacerbated as a result of subsequent treatment that
is often inadequate. This can involve the formation of a high
level of porosity in those zones contiguous to the surface, which
further facilitates the diffusion of CO2 and SO2.
The problems set out above are made more acute by the
increasing use of thin-wall structural components that are
~.i~ , -- 1 --
frequently applied to heat--insulating layera, for exarnple, sand-
wich panels, and by the high stress levels generated by tempera
ture differentials.
In order to eliminate these disadvantayes, there is a
need for a high-strength coatiny that has both good adhesive
properties on the base and a high level of resistance to gas
diffusion. In part, these objectives can be achieved by plastic
coatings or brushed-on applications. However, plastic coatings or
applications entail the disadvantages that, if they become
damaged, the attack continues immediately on the old front, and
also that the physical properties of the coating, in particular
with regard to thermal expansion, water permeability, aging
(embrittlement) and the like vary greatly from the properties of
the concrete.
A further attempt to overcome the disadvantages se-t out
above has been proposed using a concrete-like layer that can be
applied. Although the so-called mineral sealing slurries of
cement, sand, and water, or the so-called flexible slurries of
cement, sand, plastic, and water, used to this end behave better
than purely plastic coatin~s, they can be applied in coatings of
only limited thickness, which means that in the majority of cases,
gas diffusion cannot be adequately inhibiked, or that the "alkali
deposit" generated by such slurries cannot compensate for the loss
of alkalinity.
West German OLS 28 56 764 describes a concrete or mortar
mixture that contains at least one inorganic bonding agen-t as well
as a plastic that displays low-temperature adhesiveness, at least
-- 2
~5~76~
one part of the additives being forrned of particles or pellets of
organic material, in particular of plastic. Such a coMposition is
said to display a high level of resistance to changes in tempera-
ture while remaining fully efficacious, and in addition to this,
should display greatly improved elastic behaviour at temperatures
below 0C compared to previously used concretes or rnortars.
The basis of West German OLS 28 27 382 is a similar
task,namely the production of structural elements and/or coatings
of concrete, these being resistant to impact, abrasion, and
freeze-thaw cycling. The proposed solution is a bonding agent or
a concrete or mortar that consists of at least one hydraulic
bonding agen-t, as well as of at least one plastic with a specific
Tmax value, and which can optionally contain bitumen and/or tar.
According to West German OLS 26 32 691 or Austrian
Patent 353 156, a cement with increased terminal strength is pro-
posed. In order to achieve this objective, a cement of portland
cement clinker and marl clinker i3 proposed, this containing low-
lime mineral phases that can be hydrated.
On the other hand, Austrian Patent 305 871 proposes an
expanding cement. The process for the production of this
expanding, lime-free portland cement that is described is based on
maintaining a portland cement clinker in a specific temperature
range for a predetermined time and mixing gypsum and, if desired,
the usual additives with, optionally, a portland cement clinker of
conventional composition to the portland cement clinker previously
treated in this way.
_ 3 -
Even using the ahove described means one cannot achieve
the objective of the present invention, which is to create a high-
strength coating that has both good adhesiveness to the base and a
high level of resistance to gas diffusion,and which introduces a
sufficient alkaline deposit, in particular to compensate fo~ the
loss of alkalinity.
The present invention seeks to provide a dry mortar
mi~ture for coating vertical, horizontal, or inclined surEaces,
this leading to a sufficiently strong layer having a low modulus
of elasticity, it being possible to apply this in thicker layers
of, for example, 10mm, which has a high level of resistance
against CO2 and SO2 diffusion from the air into the concrete, and
which results in an adequate alkali deposit and displays a high
level of adhesiveness to a base, but which differs relatively
little from the base, for example, a concrete base, as far as its
physical properties are concerned.
Thus this invention provides dry mortar mixture of the
type described broadly above, characterized in that in addition it
contains a granular additive that increases the level of
alkalinity, is effective for a long period, the granular additive
also having a significantly lower reaction speed than the
inorganic bonding agent.
As an inorganic bonding agent, the dry mortar mixture
according to the present invention contains ~ortland cement of the
usual composition~ iron portland cement, blast Eurnace slag
cement, sulfate cement resisting white cement, aluminous cement,
modified portland cement on a basis of llCaO.7 A12O3.CaF2; quick
~5~
setting cement, Brunauer cement, Grenoble cernent, hydraulic or
extra-hydraulic lime, Roman lime, white or fat lime, and/or
caustic magnesite.
It is advan-tageous there be a mixture of 30 to 95%
cement with 70 - 5% lime, preferably 50 - 90~ cement with 35 - 10%
lime present in the dry mortar mixture as an inorganic bonding
agent.
A sand mixture can be advantageously contained in the
mixture according to -the present invention, this being present as
a conventional additive, the maximum grain size between 1 and 2 mm
being matched to the intended thickness that is to be used, and
the grain size distribution of the sand being so selected that for
the maximum grain size 4mm to 8mm it falls in the usable or
especially in the favourable range according to Austrian Standard
B ~304, and for another maximum grain size it falls in a
corresponding range.
According to a preferred embodiment of the dry mortar
mix according to the present invention, at a hardening temperature
of 20C the reaction of the granular additive that increases
alkalinity should first reach to over 25~, preferably to over 40%,
in particular over 60~ at a hardening age of the dry mortar mix of
more than 28 days.
In the dry mortar mix according to the present inven-
tion, a coarse grain portland cement clinker, preEerably with a
tricalcium aluminate content of below 5~, especially below 3~, and
most especially below 1~, is suitable as the granular addi-tive
used to increase the level of alkalinity. Because of its large
- 5 -
~25~
grain size, this clinker reacts very slowly~ ~ach time the
coating is we-tted, the clinker releases fresh calcium hydroxide
and thus refreshes the alkalinity and retards corrosion. Even
cracks can to a certain extent be closed by such slow hydration,
as can be seen in some concrete pipes.
Granular blast-furnace slag, fly ash, special dolomite
lime or hydraulic lime can be contained in the dry mortar mix
according to the present invention as the additive that increases
the level of alkalinity. According to a further advantageous
embodiment, a portland cement clinker with a high dicalcium
silicate content of more than 30%, preferably over 45~, in par-
ticular over 55%, can be contained in the dry mortar mix according
to the present invention as the alkalinity reserve. The slow
reaction speed that is desired is achieved by this high content of
dicalcium silicate.
If, according to the present invention, coarse grain
portland cement clinker is used as the alkalinity reserve, its
grain size is best between 0006 to ~ mm, preferably from 0006 to
4 mm, in particular from 0.1 to 1 mm.
Furthermore, it has been found to be advantageous to
select the grade line for the conventional additives so that the
volume of the granular materials that increase the alkalinity is
considered when setting the grade line for the conventional
additive.
With reference to quantitative composition, in one
advantageous embodiment, -the dry mortar mix according to the
present invention is characterized in that it contains 2 - 75~,
- 6 -
~25~
preferably 5 - 50%, in particular ]0 - 25% coarse granular
portland cement clinker relative to the mass of the dry mortar
mix.
In addition, the dry mortar mix can contain a plastic
that is present in powder form, dispersed in liquid and/or in
dissolved form. The proportion of plastic can vary within wide
limits, depending of the modulus of elasticity that is desired.
As an example, insofar as a very high breaking elongation appears
necessary, the proportion of plastic can amount to 60% by mass or
even higher, so ~hat the inorganic bonding agent acts, at least in
part, as a filler. However, in these mixtures, too, the main-
tenance of the alkalinity is provided by the addition of the
granular additive (coarse grain portland cement clinker), as pro-
vided for according to the present invention. Of course, as a
rule--particularly for reasons of cost--a plastic content of
1 - 10~ mass or from 2 - 4% mass is adequate, and for this reason
this range seems preferable. In any case, a plastic that is
present in powder form, dispersed in li~uid and/or dissolved,
having a Tmax value determined according to DIN 53 445 of less
than -5C and preferably less than -8C, in particular less than
-12C, is used.
Solid bodies that either contain pores and/or in which
pores are formed during the hardening process, can be contained in
the dry mortar mix as the additives that increase frost resistance
and resistance to ice-melting salt; the pore volume amounts to
0.3 - 6%, preferably 0.5 - 4%, in particular 0.5 - 2% relative to
the volume of the dry mortar mix. The pores that are either con-
- 7 -
tained or generated in the solid bodies that are added are best of
a predominant diameter of 20 - 200~ m, preferably 25 - lO0~ m, in
particular 30 - 70 ~ m (microme-ters).
T'ne dry mortar mix can be reinforced with fibres in a
very simple manner, for example, with glass fibres, synthe-tic
fibres, or coated or stainless steel fibres, and can be filled
with pigmenting agents. As an example, inorganic and/or organic
colouring pigments in a quantity of 0.05 - 2%, preferably
0.1 - 1.5~ relative to the volume of dry mortar mix can be used as
colouring additives.
The dry mortar mix according to the present invention is
characterized even at a greater layer thickness of, for example,
10 mm, by a high degree of adhesiveness to the base, displays
physical properties (coefficient of thermal expansion, water per-
meability, aging, and behaviour at different temperatures) like
-those of the base, and because of the plastic additive is highly
resistant to CO2 and SO2 diffusion. Because of the content of
coarse grain clinker, its alkalinity is constantly refreshed,
whereby in particular corrosion of the steel reinforcement is
hindered.
Most surprisingly, it was also found that a mortar
modified according to the present invention has a greatly
increased resistance to chlorine diffusion; this is of great
importance during chloride attack, as when ice-melting salt is
used. Appropriate variation of the cement/lime ratio and the help
of plastic additives can determine the modulus of elasticity to
the desired extent, thereby making it possible to achieve a very
- 8 -
~s~
high breaking elongation. In addition to this, a coating that is
produced from the dry mortar mix according to the present inven-
tion is easily worked, e.g., by spraying, trowelling, or the like,
and either a thick or thin coating can be applied. The rnortar is
applied to -the surface that is to be protected, either by hand or
by means of a conventional plastering machine, preferably by a
spiral pump machine, and then worked. In order that the full
alkalinity increasing effect of the mortar according to the
present invention is felt, it has been shown to be effective to
select a coating thickness of approximately 0.5 to several centi-
metres, preferably 1.0 to 1.5 cm. Naturally, a lesser chickness
can be applied, although this will result in less protection
against corrosion. It is expedient that after being worked, the
mortar be given a coating to protect it against evaporation. This
secondary treatment film can be applied by spray or by brush, or
the like. If the film displays increased resistance to CO2 and/or
S2 diffusion, it will further increase the corrosion effect of
the dry mortar.
The following examples describe the invention in greater
detail.
~5~
o,
.,,.,, ~ U~
~W
la ~ a) o d~ C~) d' o~ ~ d' C5
r~ 0 1~3 ~ ') t~l ~/ ,_~
Q 1
O U .
h ~ O
0
S ~ ~
u~ Q, a) (:S ~ o o~) lo ~r) ~ ~ ~ U~ d' ~ O
,a Q~ O ~ ~ ~1 ~1 ~1
~ ~ O
,1 W
O
0-~1 ~ o ~ ~ ~ ~ ~ ~ _J ~ ~ ~ ~ L~
.,,
~ 0~ d~ o~ o~O o~O o~o o~o O~o
P~ O
~ ~ o~ o~ o~ o~ o~ o~ o~ o~ o~ o~ s::
3 (~ d' d' d' d' ~ ~ ~ ~ d' d' to
O
a~ ~1
0~ d~ d~ o~O o~o d~ d~o O
-i h --1 It- ~ O ~g d' I I I I ~ d' U
O N N N .~
r ~ Z O 1~
--CO o~O d~ d~ 0\ ~I)
~~ I I I I I O O L~ O I I ~
t~) ` rl 1 ~ ~7 ~ (r) R
~: U7 ,a h ~1 .,1 ,a
,~ t.q ~ a
~X
~ ~ ~ O
O ~ C)--l
U ~
O
(1~ r-l Z d~ o\O d~ d~O d~O o~ o`~O d~O d~
O E-l O 1~:1 I I d"X) O d' ~ d' ~ O 0 ~1
~) P4 0 N ~ ~ ~ ~ ~ r-l U
O ~ r~ ~
~ m
~1 ~a _ O~o 0~ d~
O r d~O - - - - d~O dp ~
~1 0~ ~ O l` ~` I` t~ 1` ~1 ~1 ~) /~ ~ 0 4-1
~I Fi ~ N N N N N ~ '7 ~ N N C.) O
O
R
O 0
O ~I N ~ d' U'l ~9 ~ Cl:) Ci~ ~1 ~ ,~
~ ~ 1 0
~25~;~6~
Example 1:
Concrete panels measuring 20 x 20 x 10 cm were given
various coatings, at an age of ~ months. The concrete had been
produced with PZ 275 (H), had a cement:water ratio of 0.67, and at
the time the carbonatisation coatings were applied had an averaye
depth of carbonatisation of 10 mm. The types of coatings and
their effects on the continued increase in the depth of
carbonatisation can be seen in Table 1. The coated panels had
been stored in the open air in an urban environment.
A powdered acrylic resin dipersion was used; the clinker
in tests 3 to 9 was a portland cement clinker with a dicalcium
silicate content of 35%; for test 10 this was 48~, and for test
11, 56%.
As can be seen from Table 1, the addition of the coarse
grain clinker reduced the progress of carbonatisation consider-
ably, particularly in the later stages. The effect was clearly
greater than was the case using commercially available coatings to
protect against corrosion.
Example 2:
A ferroconcrete facade panel measuring 2 x 5m (water:
cement ratio 0.65) was divided into 10 equal sections, each 50 cm
wide, all of which were exposed to the weather in the same way.
In each instance, the concrete coating was 10 mm thick. At an age
of two years--when the depth of carbonatisation was a uniform 5 -
6 mm-- eight of these sections were coated as shown in Table 2.
Observation of the progress of carbonatisation and the behaviour
~` ~
~5~
of the reinforcing stee] are set out in the results presented in
Table 2.
As can be seen from this table, coating the panels with
the coarse grain clinker accorcling to the present invention
resulted in a considerable reduction in the rate of carbonati-
sation and reduced corrosion of the reinforcing steel.
Example 3:
Equal concrete test pieces measuring 12 x 12 x 36 cm
(water:concrete ratio 0.64) were used for this test. At an age of
6 months, test piece 1 was provided with a commercially available
anticorrosion coating that was brushed on. Test piece 2 was given
a 9 mm thick coating, composed in accordance with the present
invention, of 30% PZ 275 (H) portland cement, 28~ coarse grain
clinker with a grain size of 0.2/1 mm with a tricalcium aluminate
content of 2.2%, 3% copolymer plastic based on styrene-butadiene,
37.5% limestone sand 1/4 mm and 1.5% conventional flow agent
(calculated water-free). Test piece 3 was given a coating that
differed from that used for test piece 2 only in that, instead of
the PZ 275 (H) portland cement, a portland cement with a tri-
calcium aluminate content of 0% was used. Test piece 4 remaineduncoated.
- 12 -
~s~
o ~ 0 l l o o o
r~)
o u
l ~ ~ o ~ ~ o o o
,~ o7
~ ~ ~ 0
Ua~ ~ ~ooo o oooo
u~
0
o o ~ l l l l l l l l l
~ o
0 rl
h
U 0
0. ~ I u~ ~ I ~ d' I I I
.Q ~( ~1
s~ 0 a
0
U ~ ~
a~ 0 0
O~ ~III I IIII
0
S
0
~ ~ O l l l l l l l l l
C
.~ dP dP dP dP r~
U~
~q I .. ...
~1 d' ~ ~ d' d'
ra dP o~O o'P H o`P dP dP a
d'O O O H 1-1 0 0 0
0 ~ ~
U~ ~01
.~ .~
O
O`P o~ ~ ~
~U~ ~ I O O I I I aJ
O ~ ~ U U ~
Z O 0
OD (I) a) ~,
c ~ R R
a) 0 ,~ I I 1 0 0 1 1 1 S
w a)~ 3) ~ ,, ,, ~ o`P
0 1 ~:~ X ~ 0
o ~ ~ ~ ,~ ^ ^ ~
u aJ ua) ,~ ,~ ~ 0 ~ 0 ra ~ ~ o
J,J rl VJ r~ r~J oP ~ rj) dP dP d~ ~ ~I Ei ~
w 0 S~ u ~ o I I u~ U )~ 0 0
0 3 F~l 0 ~1 U ~ r~ ~ r l 0 N 1:~ N + ~ 0 ~ ~1
o c~ --~ R -~ R ~ ,Y ~ ~
~ O O (d 0 ~ U ~ U
o ~ ~ z ,~ u ,~ u --~ ,~ 0 ,~ a
r~ U r~ U ~rl _~ * ~J X r1 ~-1 p U~
~) 0 U~ ~ ~ J * * .~J ~ U U tJ~ r~
~r~ r1 t~ m 0,O o~P ~ P o~P o~P ~ .,, ~ q aJ
U~ J E~ ~ U~ 0 ~3 ~ U'\ 1~ Lt') U~ r~ r~ ~r~
O U 11 o~ E; rl ~i -'1 I U tr) tJ~ Q
r1 0\ I~ 10 0 0 0 ~ 0 C4 0 O O X C) ~ 0
0 t~ ~ d~ ~ o 3 (~1 -I 1~
r~ ~ ~) O
r~ 1~4 01 ~ I I I
0 0 =~: ~ ~ * ~ P~;
E~ æ o ,~ * * ~ ~ ~ o
." ,, ,~ -- 1 3
~25~q~6~L
All of the test pieces were exposed to an outside atmos-
phere eontaining a somewhat enriched level of SO2 (in the vicinity
of a garbage incinerator). After eighteen months, considerable
eracks and incipient decornposition were observed in test piece 4.
Damage could also be seen in test piece 1 (considerable arching at
the edges and on the eorners, numerous craeks)~ There were only
two hair-line craeks, eaeh 3 or 4.5 mm long in test pieee 2.
There was no visible damage to test piece 3.
The coatings according to the present invention eontrib-
uted greatly to protecting the test pieces.
Example 4:
Concrete test pieces measuring 12 x 12 x 36 cm (water:
eement ratio 0.64) were used for test purposes. At an age of six
months these were coated with a 10-mm thiek layer eomposed of 30%
275(H) portland cement, 38% limestone sand 1/4 mm, and 29.5% "fine
grain 0.1/1 mm with reserve alkalinity." 0.5% of a eopolymer
plastic based on styrene-butadiene, 1% fibres, 0.4% methyl-
eellulose, and 0.6% thixotropie agent were used as extra
additives. The following substanees were used as fine grain 0.1/1
mm with reserve alkalinity for the test pieces as shown:
Test pieee 1: blast furnaee slag A
Test pieee 2: blast furnaee slag B
Test pieee 3: fly ash
Test piece 4: hydraulie limestone (grain size 0.25/1)
Test pieee 5: speeial dolomite limestone
Test pieee 6: portland eement clinker
14 -
6~
Test piece 7: limestone sand (test sample)
The chemical composition of these substances was as
follows (annealing loss-free state):
TABLE III
SiO2 A123 ~eO~Fe203 CaO MgO
Blast furnace slag A 33% 12% 0.6% 45~ -
Blast furnace slag B 36~ 7% 0.5% 48%
Fly ash 28% 11% 5.3~ 37%
Hydraulic lime 11% 5% 3% 76%
Special dolomite2% 2% 1% 56%*) 40%
limestone
*)As indicated by X-ray diffraction testing, the total CaO is
present as inert, insoluble CaC03. The alkalinity increasing
effect of the special dolomite limestone is attributable to the
content of reactive MgO.
All the test pieces were exposed to an outside atmos-
phere with enriched C02 levels (exhaust outlet of a vehiclegarage). At the beginning of the comparison testing, at an age of
six months, i.e., when the mortar coating was applied, the test
pieces displayed an average depth of carbonatisation of approxi-
mately 5 mm. Twenty months after application of the mortar
coating in comparison piece 7 the mortar coating was carbonated to
full depth, and carbonatisation in test piece 7 itself had risen
on average to 11 mm. In all the other pieces, a carbonatisation
depth of 2 - 4 mm was established in the mortar coating; in no
instance had the depth of carbonatisation exceeded 5 mm.
- 15 -
Example 5:
For this test, as in Example 4, four concrete test
pieces measuring 12 x 12 x 36 cm (water:cement ratio 0.6~) were
used for the tests. At an age of 6 months these were coated with
a 10-mm thick layer. The coating mortar for this layer was
composed of 25% 275(H) portland cemen-t, a further 25~ alkalinity
reserve granulate with a grain size of 0 - 0.25 mm, of 15~ lime-
stone sand 0.2 - 0.8 mm, and of 35~ limestone sand 0.8 - 1.4 mm.
The following substances were used for alkalinity reserve in the
test pieces as indicated below:
Test piece 1: portland cement clinker with 58~ dicalcium
silicate;
Test piece 2: limestone sand (test sample);
Test piece 3: here, a commercially available anticorrosion coat
was brushed on in place of the mortar coating.
All of the test pieces were exposed to an outside atmos-
phere with enriched levels of S02 and C02 (in the vicinity of a
garbage incinerator). At the beginning of the test, at an age of
6 months, i.e., when the protective coating was applied, the test
pieces displayed an average depth of carbonatisation of approxi-
mately ~ mm. Two years after application of the protective
coatings the concrete of test piece 2 was carbonated to its full
depth; the carbonatisation in test piece 2 had progressed on
average to 9 mm. In test piece 3, too, the depth of carbonatisa-
tion had increased on average to 8 mm. In test piece 1 a car-
bonatisation depth of only 1 - 2mm could be detected,on the body
itself there was at the time the protective mortar was applied a
- 16 -
r~ ~ ~. .,
layer of carbonatisation on average 4 mm thick, with adequate
reserve alXalinity still available, which could be established by
dyeing with phenolphthalein solution. Thus, not only had carbona~
tisation been avoided by the reserve alkalinity in the ~ortar
coating, but it had also been possible to build up adequate
alkalinity in the concrete that had originally undergone carbona-
tisation and been coated with the mortar.
In contrast to the substance that increases alkalinity
described in the previous examples, the portland cement clinker
used in the above example was ground relatively fine. The reac-
tion time, which was slow in comparison with the other portland
cement clinker present in the others in the bonding agent, was
achieved not by a coarser grain size, but by an extraordinarily
higher dicalcium silicate content of 58%.
- 17 -
