Research News Blistering in Resinous Systems on Concrete Surfaces Types Causes and Preventive...

5/21/2018 Research News Blistering in Resinous Systems on Concrete Surfaces Types Causes and Preventive Measures

1/11

J P C L J a n u a r y 2 0 0 7 75www.paintsquare.com

ResearchNews

Blistering in Resinous Systems on Concrete Surfaces:

Types, Causes, and Preventive MeasuresBy Ing. Ciro Scial Director, Building DivisionAPI spa, Mignanego (GE) Italy

Continued

listers in resinous systems

on concrete substrates can

compromise the perfor-

mance of the coating and its protection

of the substrate. It is important for

applicators and inspectors to under-

stand the types of blisters that form on

concrete, how they may affect coating

performance, and how they may be pre-vented. This article will distinguish and

discuss different types of blisters. These

types of blisters can be differentiated by

the time they take to develop and their

causes. The first type of blister to be dis-

cussed develops over the short-term,

even during application. A short-term

blister is caused by blow-up. The second

type of blister to be discussed develops

over a medium term, such as a few days

after application, and is caused bydetachment. The third type of blister

develops over the long term, after some

weeks, months, or even one or two

years. Its cause is osmosis.

Blisters Caused by Blow-UpThe first cause of these blisters, which

are superficial imperfections in

resinous linings, is air trapped inside the

pores of concrete. In addition to the

time they take to develop, these blistersmay be distinguished by their typical

shape, that of a crater, with a hole in the

center (Fig. 1). The blisters form when

the resin is still fluid, but the character-

istic crater shape does not develop

immediately during application. The

blisters can be confused with the air

bubbles the product normally incorpo-

rates during mixing. The day after the

application or, just a few hours later, the

normal air bubbles disappear, while the

blisters burst, or blow up, creating the

crater shape that remains easily visible

in the surface. The diameter of the

craters varies between 1 mm and about

4 to 5 mm (Fig. 2).

Two conditions can create blisters by

blow up:

the presence of medium-large cavities

in the surface layer of the concrete slab

connected to the surface through pores,

capillaries, cracks, and other voids; and the heating of the slab during the

application of the resin.

It is common practice to smooth the

surface of a concrete floor by a mechan-

ical troweloften a compactor with

rotary blades. Besides levelling and fin-

ishing the surface, the trowel compacts

the casting, due both to its weight and

the movement of the blades. This opera-

tion usually creates a compact and well-

closed surface layer. But when theoperation does not produce a compact

surface, blast cleaning the surface, as

needed before coating, makes the condi-

tion worse, highlighting the porosity of

the surface.

When the resin is later applied, it

slowly penetrates the capillaries, push-

ing out the air they contain. The air

comes up towards the surface, forms a

bubble, and is released when the bubble

bursts. When the air is released quickly,the lining is still fluid and can close

again after the air bubble bursts. But if

the release is slow, the air reaches the

surface after the lining has plasticized

and cannot close once the bubble bursts.

Hence, a crater is formed where the

bubble burst. This process is what we

are calling blow-up.

It is difficult to foresee if the surface

will create blisters by blow-up, especial-ly if it is compacted. But we can easily

assert that blisters are likely to develop

by blow-up on a surface smoothed by

hand, on old floorings, on repaired

cracks, or after cutting and re-installing

mortar on rebar in a concrete floor.

Heating the slab also causes blisters

by blow-up. When concrete surfaces,

either outside or inside, are exposed to

the sun, the solar irradiation produces

an increase in the temperature of theslab. If the slab is being coated while

exposed to the sun, the heat causes an

increase in pressure within the slab.

The pressure pushes the air that the

slab contains up towards the surface,

and blisters from blow-up form during

or shortly after application.

Blisters caused by blow-up can be

avoided. When a surface is prone to

develop blisters by blow-up, a low sol-

vent, pore-plugging primer can be

B

Fig. 1: Crater and hole in blow-up blisterFigures courtesy of the author

Fig. 2: Blisters caused by blow-up


2/11

J P C L J a n u a r y 2 0 0 776 www.paintsquare.com

Research News

Continued

applied, or the still fresh coating prod-

uct can be dusted to saturation with

fine particle size quartz (0.06 to 0.25

cm). Filling the pores will prevent the

resin from penetrating the cavities.

To avoid blisters by blow-up due to

heating of the surface, it is usually

enough to begin application during the

period of cooling, when the solar irradi-

ation is lower (in the afternoon); this

practice can avoid the increase in pres-

sure that would force out the air that

causes blisters.

There are cases in which avoiding

blisters by blow-up requires using both

remedies (application during the cooling

period, and priming and dusting to satu-ration) or applying the primer twice.

Blisters Caused by DetachmentSurfaces that are not properly cleaned

and prepared are often the cause of blis-

tering by detachment. Due to its rise

through capillaries and its condensa-

tion, water may also cause blisters to

form by detachment. These blisters

form soon after application, sometimes

the day after, but generally after one ortwo weeks. They have an oval shape,

with the longer dimension varying

between 5 to 6 cm and 10 to 20 cm or

more. The blisters are soft to touch and

look like the blisters in a carpet.

Water on a substrate being coated

behaves like dust on the surface (or an

otherwise poorly prepared surface).

That is, the water collects between the

coating, which is not yet perfectly hard,

and the surface of the concrete, pre-

venting good adhesion. Hence, water or

moisture can seep under an incomplete-

ly hardened coating.

Detachment will occur in a short or

long time, depending on how changes in

temperature affect the thermal move-

ment of the coating. Detachment plasti-

cally deforms the coating and is visible

as blisters.

By opening the blisters, we can verify

the condition of the substrate and checkthe blisters inner surfaces for damp-

ness or polluting substances. We can

then confirm the cause of the blisters.

To avoid blistering by detachment, it is

necessary to prepare and properly

clean the surfaces. In cases of dampness

in the substrate, it is necessary to either

wait until the substrate is dry or use a

water-borne epoxy-concrete product

suitable for damp surfaces.

Osmotic BlistersThe development of osmotic blisters

(bubbles) in resinous systems on con-

crete floorings is a well known phenom-

enon for applicators and operators in

this field. Osmotic blistering is slow and

progressive. It appears some weeks,

months or even one to two years after

application.

There is general agreement that the

cause of these blisters is osmotic pres-

sure. It is necessary to consider the phe-

nomenon of osmosis to identify the ele-

ments that characterize this physico-

chemical process.

Osmosis often occurs in nature, in

both the plant and animal worlds. For

example, if we put some red blood cor-

puscles in water, we can see that they

inflate, grow, and then break. This

process occurs because the cell mem-

brane is permeable to water but not tothe solutes in the cell solution (hemoglo-

bin and other proteins). In trying to

reach a condition of balance between

the two liquids, some water goes into

the cell.

If the cell membrane is strong enough,

there will be equilibrium between the

energy of the concentrated solution

inside the cell, as a result of the hydro-

static pressure, and the energy outside

the cell. That is, the energy inside thecell is high enough to balance the free

molar energy of the solvent (water) of

the diluted solution outside the cell.

To create osmotic pressure, the fol-

Noordhoek 7, 3351 LD Papendrecht P.O. Box 184, 3350 AD PapendrechtThe Netherlands Tel.: +31 (0)78-6546770 Fax: +31 (0)78-6449494

[email protected] www.eurogrit.com

Expendable abrasives recyclable abrasives specialtyabrasives floor and filler products special sand and gravel

Holland, the country of wooden

shoes, but also the country ofthe best blast cleaning abra-sives. Eurogrit is the biggestproducer and supplier inHolland of high quality blastcleaning abrasives for single ormultiple use.

From its own port facilities,

Eurogrit exports its productsall over the world. Eurogrithas an excellent internationalreputation and can deliver atany time and any place accor-ding to international standards.

Famous products from HollandFamous products from Holland

ClickourReadere-Cardatpaintsquare.c

om/ric
http://www.eurogrit.com/http://www.eurogrit.com/http://www.eurogrit.com/http://www.eurogrit.com/http://www.eurogrit.com/http://www.eurogrit.com/http://www.eurogrit.com/http://www.eurogrit.com/http://www.eurogrit.com/http://www.eurogrit.com/http://www.eurogrit.com/http://www.eurogrit.com/http://www.eurogrit.com/http://www.eurogrit.com/http://www.eurogrit.com/http://www.eurogrit.com/http://www.eurogrit.com/http://www.eurogrit.com/http://www.eurogrit.com/http://www.eurogrit.com/http://www.eurogrit.com/http://www.eurogrit.com/http://www.eurogrit.com/


3/11

Corporate Headquarters: 888.732.1270 | www.crownpolymers.com | [email protected] | California: 866.558.9378

Now you can present clientswith the best flooring solutions.Order your free CD-ROMCall 888.732.1270 today!

W I N D , R A I N , S L E E T O R S N O W

Crown Polymers Products Will Keep

You In Business 365 Days Per Year.

From a freezer floor installation in the

Arizona summer heat, to a factory floor

in the middle of a Midwestern blizzard,

our experts can keep you productive

year round, no matter your location.

In addition, at Crown we are always

creating new products and improving

our expansive collection of special

product formulations.

For industrial & institutional

applications, self-leveling CrownShield SL

solves floor damage problems. Our high

performance products, including our

high and low temperature cure overlays,

are designed to be applied and perform

superbly in even the most hostile

environments.

Crown Polymers offers the industry's

most qualified technical, marketing

and finest customer service department.

We promise to provide the best

products and service in the business.

JPCL

1-

07

For Information About Our Winter

Training Programs, Call Today!

CrownShield

SL CrownQuartz& CrownHybrid SpeedCove

Visit Our New Website!

CrownSpatter

Click our Reader e-Card at paintsquare.com/ric
http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/http://www.crownpolymers.com/


4/11


Click

ourReadere-Cardatpaintsquare.c

om/ric

Research News

lowing elements are necessary:

a defined space containing a pure solvent or a dilute solu-

tion;

a defined space containing a concentrated solution; and

a semi-permeable membrane separating the two spaces.

That is, the membrane must be one through which the sol-

vent can pass but the solute cannot.

The system described above is defined as an osmotic cell.

How and When an Osmotic Cell Develops in ConcreteTo understand how and when an osmotic cell develops in the

surface layer of the concrete surface, we will look at features

of the cell and the development of osmotic blisters.

The Diluted Solution and the Concentrated Solution

Research carried out by different authors has verified that

the surface layer of a concrete slab shows physical-chemicalcharacteristics that differ from those of the inner layers.

During the first phase of concrete maturity, water transports

most of the soluble salts toward the surface. This transport

is helped by mechanically smoothing and compacting. This

surface part of the concrete slab is exposed to air and subject

to continuous evaporation, and therefore takes up a different

structural configuration from the inner parts of the same

slab. The area of the concrete nearest the surface has more

cement, more soluble salt concentration, more trapped air,

and more micro-cracks.

Inside the concrete slab, two areas with different chemical-

physical structures can be distinguished:

a first area, near the surface, with more soluble salts in the

pores and with more micro-cracks; and

a second area, more internal, with less soluble salt content.

Water is fundamental in determining the solutions, and the

presence of water may be due to different sources.

Water from the concrete mixture may not have complete-

ly evaporated;

Ground water may be present in the strata or subsoil.

Water may have leaked from pipes or other structures

under the concrete layer.

The water, rising through the concrete slab, will create thetwo solutions by dissolving the soluble salts in the concrete

pores.

The Semi-Permeable Membrane

The semi-permeable membrane is formed solely from con-

crete. In the surface layer, besides more inorganic soluble
http://www.crownpolymers.com/http://www.innovatechproducts.com/


5/11


Research News

WITH OXFORD INSTRUMENTS

NEW MODEL 150,COATING THICKNESS

MEASUREMENT IS AS EASY AS:

800-678-1117847-439-4425 fax

[email protected]

The 150 recognizesferrous vs. nonferroussubstrates and employs the

correct test method automatically.

Visitwww.oicm.com/powdercoatingtoday.Call 1-800-678-1117for more info.3

12

BUTTON OPERATION

MEASUREMENTTECHNOLOGIES

WAYS TO LEARN MORE:

Accurate results atthe press of a button.No operator training,no calibration, no hassles.

BUTTON OPERATION

MEASUREMENTTECHNOLOGIES

WAYS TO LEARN MORE:

Continued

salts, there are also more micro-cracks. The saltsessentially

sodium, calcium, magnesium and potassium

hydroxidesreact with carbon dioxide (CO2) in the air over

the surface of the slab. As a result of the reaction, along with

other products, calcium carbonate CaCO3, which is an insol-

uble salt, will be formed. The reactions with regard to the

sodium salts, may be written as follows.

CO2 + 2 NaOH = Na2CO3

Na2CO3 + Ca(OH)2 = CaCO3 + 2NaOHThe calcium carbonate (CaCO3) settles on the walls of the

pores and of the superficial micro-cracks reducing their

diameter. As this process continues, more calcium carbonate

will settle into the micro-cracks and pores, producing sedi-

ment that is insoluble in water. The sediment narrows the

bigger pores and, together with the sediment, build the semi-

permeable membrane. I do not think the primer applied

before the resinous coat could form the semi-permeable

membrane. In my opinion, the primer may help reduce the

diameter of the biggest pores, and so help form the mem-

brane, but the primer cannot be the membrane itself.In addition, if formulated with organic solvents soluble in

water, the primer can increase the osmosis phenomenon or

even cause it. In this case, the solvents could help to develop

the concentrated solution under the coating. The primer

alone cannot be the semi-permeable membrane, as proven by

the blisters I found in a resinous coating in an application car-

ried out directly on concrete surfaces without any primer

application.

The Development

of the Osmotic Cell in ConcreteInside a concrete slab, two different areas can be distin-

guished on the basis of their constitution and the presence of

higher or lower levels of soluble inorganic salts (Fig. 3).

Moreover, as established above, the walls of the various

pores, generally those very near to the surface, form semi-

permeable membranes because they are exposed directly to

the carbon dioxide action. The membranes allow passage of

the water but not of the salts contained in the pores.

Whatever its source may be, water reaches the coating

after it has hardened and set on the surface. If water came

into contact with the coating before the coating hardened and

Fig. 3: Two areas in the concrete slab distinguished bytheir constitution and levels of inorganic soluble salts
http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/http://www.oicm.com/


6/11


Click


om/ric

Research News

Continued

set, an osmotic cell would not develop, but the coating would

not adhere to the substrate. Hence, water must be under the

coating, but, after the coating has adhered well to the surface

and has hardened well.

Except in certain instances, the main cause of the two solu-

tions is moisture that moves up through the concrete slab.

The presence of water in a slab is never really clear. In fact, it

is not easy to know when a flooring is at risk of developing

osmosis. Every time osmotic blistering occurs, the slab looks

dry, and there are no signs of the presence of water (such as

efflorescence, damp patches, or a damp surface). If noting the

presence of water on the surface were enough to avoid

osmotic blistering, there would not be so many cases of it. It

is also not possible to establish a percentage of dampness at

or above which osmotic blistering will occur.

Values under 3% of relative humidity, measured with a

carbide hygrometer CM in samples taken in the inner areas

of the slab, indicate that osmotic blistering is unlikely but still

possible. Another method of evaluation to be used with the

above method, to find out the presence of water, is to spread

a quite thick plastic sheet of about 3 x 3 meters on the sur-

face, seal all its edges, and determine after 24 to 48 hours if

there is condensate under the plastic. If so, there is excess

moisture in the concrete.

While we do not know how much moisture is needed to

indicate without a doubt that osmotic blistering will occur, it

is clear that moisture is the decisive element in the develop-

ment of osmosis inside a concrete slab.

The Development of the Blisters

Blisters depend on moisture coming up through the concrete

slab, meeting the barrier of the resinous coating, and begin-

ning to condense under the coating and into the pores.

Because of moisture condensation under the lining, we can

find critical points near the surface of the concrete, such as

cavities, small discontinuities, and micro-cracks with concen-

trated solutions of soluble inorganic salts. In contrast, in the

inner layers, condensation will create the diluted solution.

The critical points, where the concentrated solution isfound, are very small, and their walls are the semi-permeable

membranes that the water from diluted solutions slowly pen-

etrates. To cause the development of the blisters, it is neces-

sary for the critical points (where the concentrated solution

is) to be bounded on one side by the resinous coating, which

will act as a plug. That is, the coating must have good adhe-

sion to the surface, be at least 1 mm thick to be waterproof,

and must be able to oppose, by becoming deformed, the push

of the osmotic pressure.

In contrast to what has been asserted by other authors, I

am arguing that the development of osmotic blisters is not
http://www.lumiflon.com/


7/11

Please visit our Booth at PACE

Click our Reader e-Card at paintsquare.co
http://www.pace2007.com/http://www.pace2007.com/http://www.pace2007.com/


8/11

Research News

possible if there is no adhesion of the

coating to the surface.

The dimension of the bubbles, which

varies between 3 to 4 mm and a maxi-

mum of 2.5 to 3 cm, proves that there is

adhesion between the coating and the

surface. If there is no or low adhesion,

the osmotic process should produce

more and larger swollen areas because

the opposing forces are low or negligi-

ble. The moisture condensation would

occur in very large areas without the

creation of an osmotic cell, and the

detachment would take place because of

thermal movements of the coating.

Examples from the FieldVarious applications of coatings with

osmotic blistering have been analyzed.

One of the biggest applications analyzed

occupied 1500 m2 of surface, which

was completely covered with blisters of

various dimensions.

Osmotic blisters are easily recog-

nized. The blisters become visible on

thick, deformable, and impermeable

resinous coatings (Fig. 4). If not on the

whole surface, the blisters often are

localized in areas that I would call criti-

cal: near openings, adjoining outer walls,

along particular lines. The blisters arevery hard to touch, and if they are per-

forated, a pressurized liquid comes out.

Analysis of the liquid proves it to be a

watery inorganic solution of sodium,

potassium, and calcium salts.

The coatings in which the blisters

form can create a perfectly imperme-

able plug to hold in liquids (and gases),

which is necessary for the development

of the osmotic cell. The coatings also are

thick enough to lose their shape, but

without bursting, under the pushing

thrust of the osmotic pressure.

One particularly instructive case that

I analyzed involved osmotic blistering

in a floor coating applied in a shop near

Cagliari in Sardinia. The osmotic blis-

ters developed after the application of a

self-levelling coating over an existing

thin film coating (approximately 0.300

mm thick) that had not caused any

problems. The blistering astonished the

application technician and angered thecustomer, who ascribed the cause of the

defects to the poor quality of the prod-

uct of the second application.

My examination showed blisters

throughout the entire thickness of the

original and the new coatings, which

Fig. 4: Osmotic Blisters

Click our Reader e-Card at paintsquare.com/ric
http://www.pace2007.com/http://www.keyresin.com/http://www.keyresin.com/


9/11


Research News

Continued

adhered perfectly to one another. The

test of the fluid extracted from the blis-

ters determined that it was a watery

solution of inorganic sodium and potas-

sium salts, indicating that osmotic pres-

sures caused the blisters. A further

indication of osmotic blistering was that

the original thin film coating was blister

free for yearsuntil one month after

the self-levelling layer was applied.

In this case, which is typical for

osmotic blistering, no one expected that

blisters would develop on that flooring.

So why did they form? There was no

condensation under the original resin

because it could not create a barrier to

the moisture rising through the floor.The application of the new coating with

a greater thickness created the barrier

to the moisture that helped the conden-

sation build up under the coating. The

buildup of condensation started the

osmotic process, which led to the devel-

opment of the blisters after one month.

Another important point emerging

from the analysis is that new concrete

surfaces provoke osmosis more easily

than old surfacesthose that are morethan three years from the casting. In my

opinion, old surfaces are less prone to

osmosis because soluble salts, which

were in the surface cracks, have been

almost completely removed or trans-

formed into insoluble salts from normal

wear and cleaning of the flooring and

from carbonation. Hence, if there is con-

densation but no soluble salt content,

osmotic cells do not develop. This find-

ing also confirms that the superficialcritical points are small and are the

areas where the concentrated solution

of soluble salts develops.

Preventing the Development ofOsmotic Blisters

In the case of floorings on the ground,

the elements that cause the develop-

ment of an osmotic cell are listed below:

an area with a highly concentrated

solution due to the inorganic salts and

water in concrete,

an area with a diluted solution due to

the inorganic salts and water in con-

crete,

a semi-permeable membrane,

the capability of the resinous coating

to form a thick and moisture imperme-

able plug, and

the adhesion of the coating to the sur- Fig. 5: Forces causing the developmentof osmotic blisters
http://www.keyresin.com/http://www.polycoatusa.com/


10/11


Click


om/ric

Research News

face before the condensation of water.

Figure 5 shows how osmotic blisters

develop.

To control or avoid the development

of osmotic blisters, it is necessary to

intervene with one of the above ele-

ments. I think, and I had the opportuni-

ty to verify it, that even a particular and

careful preparation of the surface by

double peening, followed by water

washing, is not enough to eliminate the

soluble salts or the osmosis.

The best results for controlling or

avoiding osmotic blistering are obtained

by preventing water infiltration. There

are measures for preventing infiltration

that can be taken before or after the

application of the concrete flooring.

Before the concrete casting, a proper

water barrier can be applied on the bal-

last to prevent the moisture coming up

through the slab.

After the concrete casting, two differ-

ent kinds of products can be used to

prevent water infiltration: a water-

borne epoxy-based concrete primer and

a breathable resinous coating.

In my opinion, based on my experi-

ence, there are two possible reasons

that a primer layer based on a water-

borne epoxy-concrete product may

help eliminate the osmotic process.

First, during application, the primer

can dissolve part of the soluble salts on

the surface and trap them in the epoxymatrix as it hardens. In approximately

80% of the cases in which we applied

only this product, no osmotic blistering

occurred, while in the remaining 20%,

the problem decreased drastically, with

just a few blisters appearing on large

surfaces.

Second, unlike solvent-borne prod-

ucts, waterborne products do not help

semi-permeable membranes form.

Breathable resinous products canalso be applied after concrete casting,

and, in fact, this approach to preventing

water infiltration produced the best

results, even where the problem had

developed seriously. The use of breath-

able products avoids moisture conden-

sation and thus prevents the develop-

ment of the diluted and concentrated

solutions of inorganic salts. I have found

that application of breathable resinous

systems with moisture permeability Sd= 22.5 m (where Sd is the equivalent

thickness of air) gave excellent results

in every application carried out, even in

critical situations with high water con-

tent in the surface and in case of the

repair of an already developed osmotic

problem.

The waterborne epoxy-concrete

product can be combined with the

breathable resinous product, or the

breathable product can be used alone,

with the restrictions described above in
http://www.wiwa.com/


11/11


Research News

case it is necessary to use thick, imper-

meable coatings.

ConclusionsThe results of the experiences, assess-

ments, and analyses carried out on dif-

ferent applications, suggest the follow-

ing conclusions.

Blisters caused by blow-up result

from the nature of concrete, particular-

ly, the air it contains. Air comes out

because of the increasing pressure

caused by temperature changes or by

liquid resin replacing the air. The blis-

ters can be avoided by using a high-

solids product, by dusting the coating to

saturation with 0.060.25 cm powder,and/or by applying the product when

the surface is cooling down.

Blisters caused by detachment are

ascribed to an improperly cleaned sur-

face and to water. Cleaning the surface

more carefully and using products suit-

able for damp substrates may help

avoiding this these blisters.

Osmotic blisters are caused by osmot-

ic pressure that develops after an

osmotic cell forms in the surface area ofthe concrete flooring. The main ele-

ments in osmotic blistering are moisture

condensation in areas separated by sol-

uble inorganic salts and micro-structure

differences. These elements must be

controlled to contain or eliminate the

development of osmotic pressures.

Osmotic pressure can be controlled or

eliminated before the concrete casting,

by applying a proper moisture barrier,

or after the concrete casting, by usingbreathable and/or waterborne epoxy-

concrete products. Breathable products

avoid or at least restrict condensation.

Waterborne epoxy-concrete products,

together with a very careful surface

preparation, avoid or reduce the forma-

tion of the concentrated solution and

incorporate the soluble salts into the

epoxy matrix.

References1. Rogest W. Dively III, Materials

Performance, May 1994.

2. Frederick A. Pfaff and Frederick S.

Gelfant, Osmotic Blistering of Epoxy

Coatings on Concrete, Journal of

Protective Coatings & Linings,

December 1997, pp. 5264.

3. David White, Paints and Varnishes,

1997.

4. Robert R. Cain, Solving Problems

Caused by Moisture Vapor

Transmission on Coated Concrete

Floors,Journal of Protective Coatings

& Linings, February 2001, pp.

96105.

5. Daryl Fleming, Shedding Light on

Osmosis in Resin Flooring,Journal of

Protective Coatings & Linings,

February 2004, pp. 5357.
http://www.pda-online.org/

Research News Blistering in Resinous Systems on Concrete Surfaces Types Causes and Preventive...

Documents

Transcript of Research News Blistering in Resinous Systems on Concrete Surfaces Types Causes and Preventive...