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Waterproofing WithCementitious SlurriesBy Dr. Hermann Lutz, Wacker Polymer Systems

Water in liquid or in vapour form

is the most destructive

weathering element for

building constructions, like concrete,

masonry, and natural stone structures.

Waterproofing and damp-proofing

techniques have to preserve a structures

integrity, functionality and usefulness

throughout its whole life time. To prevent

all possible water intrusion causes, theexterior (side) of a building must be

protected form top to bottom with

waterproof materials. All waterproof

measures have to be part of a whole

system and must interact integrally for

complete effectiveness and to prevent

water infiltration. Should one of these

systems (parts) fail or not act integrally

with all other protection systems, leakage

will occur. Adequately controlling

groundwater, rainwater and surface water,

as well as the transport of humidity in

form of water vapour will avoidunnecessary repairs to building exterior

or its damage or even destruction

(deterioration). Apart form protecting the

exterior of building constructions, there

are a multiplicity of waterproofing

materials for interior use, as for bath

rooms, toilets, swimming pools, water

tanks, etc. Some of the waterproofing

measures are used to protect against the

detrimental action of aggressive

substances like salts and acids

transported by the water.

Waterproofing Systems

The different components of a buildings

exterior can be classified in:

Roofing: has to prevent as an external

layer water intrusion in horizontal or

slightly inclined directions.

Below-grade waterproofing:

materials and measures that prevent

surface and ground water or water under

hydrostatic pressure from entering into astructure or its components. These

systems usually are not exposed or

Flashing: materials or systems

installed to direct water entering through

the building skin back to the exterior.

Flashings are installed as backup systems

for waterproofing or dampproofing

systems.

Traditional seal ing and waterproofing

systems, e.g. according to the German

standard DIN 18195, include bituminousmaterials, plastic waterproofing foils and

metal tapes for interior and exterior

applications. In order to seal and to

protect the surface of buildings and

structural components against the action

of dampness and water, in addition to this

traditional systems nowadays products

based on reactive resins (e.g. epoxy or

polyurethane resins), purely dispersion-

bound paste-form products (so-called

paintable waterproofing membranes) and

mineral waterproofing slurries

(cementitious waterproofing membranes)are widely used. In the following the

cementitious waterproofing slurries and

their application will be discussed.

Cementitious waterproofingslurries

Cementitious waterproofing membranes

have been successfully used for more than

40 years in Europe for protection of a wide

range of building structures and structural

components either exposed periodic or

long-term wetting (surface water,seepage water), low hydrostatic pressure

(soil dampness) or in combination with

subjected to weathering such as by

ultraviolet radiation. Examples for below-

grade waterproofing materials are metal

and plastic films, cementitious

waterproofing sealing slurries and

bituminous waterproofing systems

(materials).

Above -g rad e waterpro of ing: a

combination of materials or systems thatprevent water intrusion into exposed

structure elements, including protective

decorative barrier systems. These

materials are not subjected to hydrostatic

pressure but are exposed to weathering

and pollutant attack. Examples for above-

grade waterproofing are all kinds of paints

including cementitious paints, mineral

finish plasters and renders if they are in

accordance with the Knzels rule, which

requires an extremely low coefficient of

water absorption (water repellent effect),

combined with a sufficiently high watervapour permeability (requirement:

coefficient of water absorption W < 0,5kg/

m2h; and water-vapour diffusion

equivalent air-layer thickness Sd< 2 m; and

Sdx W < 0,2 kg/m2h).

Damp-proofing : materials which

reduce or prevent water vapour

transmission and which are resistant to

water vapour or minor amounts of

moisture; these systems may act as back-

up systems to primary water-proofing

materials. Damp- proofing materials arenot subject to weathering or water

pressure.


2/53 r d Q u a r t e r 2 0 0 5

rticleAappropriate engineering even high

hydrostatic pressure.

Cementitious membranes (slurries) are

used for waterproofing wet rooms and

water tanks, and due to their excellentweathering resistance for exterior

surface protection as well. Typical

applications are the sealing and

waterproofing of e.g. basement walls,

water tanks, swimming pools, walls and

floors in wet-rooms like toilets and bath-

rooms, balconies and terraces (as a

waterproofing layer to be tiled over). In

addition flexible cementitious

waterproofing membranes are often

used as a protective surface-coating

system for structural concrete (e.g.

protection of reinforced structuralconcrete for new structures as well as for

concrete structures after rehabilitation;

protection against penetration of water,

chlorides and free carbon dioxide in

order to avoid corrosion of the

reinforcement) or as a protective layer for

building constructions against

aggressive chemicals (sulphates, acids,

e.g. in waste-water drains).

Advantages of cement-based

waterproofing slurries are their excellent

resistance against water, even if exposedpermanently, their excellent resistance

against long term weathering, a good

scratch resistance, a good load-carrying

capacity and a much higher water vapour

permeability compared to most of the

other systems (consequently no problems

with blistering when water vapourpermeates through the waterproofing

membrane). Cement based

waterproofing slurries are easy to use, are

non-toxic, they provide a fully bound and

monolithic surface without joints, they

can easily be applied on substrates with

complex surface shapes. In contrary to

other systems, cementitious

waterproofing slurries can be applied

even on damp and wet mineral surfaces

and their physical properties are less

temperature-dependent compared to

bitumen based materials. Pure and simplecement-based slurries are still used for the

protection against surface water, but they

are not suitable to seal against water

under hydrostatic pressure.

In order to improve the poor adhesion, the

poor water tightness, and the extremely

low deformability or flexibility of pure

cementitious slurries, polymers are added

in form of liquid dispersions on job-site or

in form of a redispersible powder already

mixed in the dry-mix mortar. The use of

special additives in the dry-mix mortarslike water retention agents, thickening

agents and rheological additives in

combination with the polymeric binder in

form of the Vinnapas Redispersible

Powder, provide an excellent workability

and make sure that there is no need for a

post water-treatment of the appliedslurry.

Today different systems of cementitious

waterproofing membranes or slurries are

available:

Standard or rigid mineral

waterproofing slurries

Standard, rigid mineral waterproofing

slurries are polymer-modified prepacked

dry-mix mortars which are mixed

(gauged) with water before being applied

as a slurry by brush, roller or airlessspraying, as well as by trowel if less

gauging water is used. Standard or rigid

waterproofing slurries can only be used

for mineral substrates which are stable,

sound and solid, and if there is no risk for

crack formation, movements or

dimensional changes (e.g. shrinkage). A

typical composition for such a rigid

membrane is given in Table 1, some typical

characteristics in Table 2. The water

tightness depends on the cement

content, the shape and particle size

distribution of the fillers, the type ofchemical additives used and the amount

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rticleAof polymer in form of Vinnapas

Redispersible Powder.

Redispersible powders are used as

polymer binders in order to improve the

adhesion of the slurry on differentsubstrates, to improve its cohesion, the

flexibility, the abrasion resistance and

toughness and last but not least the water

tightness and density of the mortar. Such

polymer modified cementitious

waterproofing slurries can withstand the

water pressure not only form the positive

side, but to a limited extend, due to their

excellent adhesion and cohesion, in

addition form the negative side, too, if this

is necessary for some special practical

applications. Preferentially, a redispersible

powder with a hydrophobic (waterrepellent) effect like Vinnapas RI 551 Z is

incorporated in the dry-mix mortar.

Typical dosage is 2 to 10%, depending on

the quality of the raw materials available,

the formulation and the requirements in

respect of the water tightness and

mechanical characteristics. If tightness

against hydrostatic pressure is required,

higher amounts of polymer in form of a

Vinnapas Redispersible Powder have to

be used (5 to 10%). It is important to know,

that the use of water repellent agents will

provide to a cementitious mortar water-repellent or waterproofing characteristics,

but does not make the mortar

impermeable against water under

hydrostatic pressure. In order to achieve

this, the mortar must be very dense

(appropriate filler particle size

distribution) with a low air-pore content

and a sufficient high polymer content (the

polymer has to close the cavities and

pores).

Flexible cementitious waterproofing

slurries (two-component systemsDevelopments in the late 1970s have led

in Europe, in addition to the traditional

rigid waterproofing slurries, also to

flexible waterproofing slurries which to a

limited extent are capable of bridging

over small cracks (up to approx. 1 mm) in

the substrate. The flexibility of such

products strongly depends on the

polymer/cement ratio and, to a lower

extent, on the flexibility of the polymer

itself. In addition the flexibility of a

cementitious waterproofing membrane

depends after application and during itslife-time upon the environmental

conditions it is being exposed to. These

conditions can be simulated by laboratory

test methods, using different storage

conditions. When a flexible cementitious

slurry is applied and stored under dry

conditions, especially at high

temperatures and on absorbantsubstrates, only a minor part of the

cement of this thin-layer system is able to

react. Therefore the actual effective

polymer/cement ratio is higher than the

theoretical value and thus the whole

system is very flexible, being dominated

by the polymer binder. When later the

cement has rehydrated under humid or

wet conditions, the system will achieve his

final strength, with the consequences that

the tensile strength will increase, and the

elongation and so the flexibility will

decrease. Therefore, the mechanicalcharacteristics of cementitious

membranes can only be compared, if the

cement used in the formulation is fully

hydrated. This means, that cementitious

slurries have to be tested in the

laboratories under conditions providing a

full hydration of the cement in order to

check the remaining flexibility after long

water immersion. This is important to

avoid failures due to insufficient flexibility

after the complete hydration of the

cement in practice.

Flexible waterproofing cementitious

slur ries are used on substrates being

supposed to shrinkage, vibrations,

movements, stresses, crack formation and

on substrates difficult to be coated like

wood, steel, aerated light weight blocks

and gypsum. Due to their high polymer

content, they are diffusion and chemically

resistant against chloride, sulphate ions

and carbon dioxide and other aggressive

materials.

Two-component flexible cementit iouswaterproofing slurries can be offered in

two different types of product forms:

(a) as a two-pack system composed of a

prepacked dry-mix mortar based on

cement, fillers and other additives plus

a liquid dispersion in the second pack.

The dry-mix mortar is mixed on job-

site with the diluted aqueous

dispersion which contains

preservatives and some other

additives. This is the mostly used

system nowadays for two-componentflexible waterproofing membranes. In

most cases the dry-mix mortar already

contains a minimum of polymer in

form of a Vinnapas Redispersible

Powder.

(b) as a system based on a wet premix

(aqueous dispersion), fillers andadditives. This paste-form product is

blended on job-site with the locally

available Portland cement, giving a

flexible waterproofing slurry,

depending on the dosage and

quality of the cement. A typical

composition for such a rigid

membrane is given in table 1, typical

characteristics in Table 2. In most

cases aqueous styrene-acrylic

dispersions with a Tg between 0and40C are used as a liquid component.

One-component flexible cementitious

slurries

The disadvantage of two-component

systems for their practical application is

the occurrence of mixing errors due to the

lack of knowledge, experience and

education of the workers concerning the

appropriate dosage of the liquid

component. Wrong doses may also

happen by chance or even intentionally in

order to save money in the short term.

Using too low dosages of the liquid

dispersion, the resulting membrane mayloose its waterproofing capability if

exposed to hydrostatic pressure or will at

least provide a reduced flexibility with

failure of the system as a consequence.

Other reasons for not using two-pack

systems, apart from the difficult and risky

handling, are the expense and logistics

difficulties (e.g. the need for additional

containers and the problem of their safe

disposal; storage and transport of liquid

dispersions which could freeze or

deteriorate through microbiological

attack) and more time consuming andharder work on the job-site when

handling two-pack systems).

Because of these many disadvantages of

modifying mortars with liquid

dispersions, today more and more the so-

called one-component flexible

ce mentitious slurries in form of a

premixed dry-mix mortar are used.

Wacker Polymer Systems developed

special Vinnapas Redispersible Powders

with a very low Tg, a low water

absorption and a high water resistance inorder to be able to formulate one-

component flexible cementitious

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waterproofing sealing slurries. The

technical performance for this products

is comparable with two-component

cementitious waterproofing slurries as

shown in Table 2.

The higher costs for such a product, due to

the high dosage of the redispersible

powder, is compensated by the

advantages having a one-component

premixed polymer-modified dry-mix

mortar, like e.g. low-cost logistics and

packaging, safety and reliability for the

application by exclusion of mixing errors

on job-site, higher productivity on job-site.

Paintable, ready-to-usedispersion-bound

waterproofing membranes

Ready-to-use (paste-form) dispersion-

bound waterproofing membranes

provide an extremely high and long-

lasting flexibility and very good adhesion

on all inorganic and organic substrates.

These products are mainly used, besides

the flexible cementitious slurries, if very

flexible waterproofing membranes are

demanded and for substrates with poor

adhesive characteristics (e.g. on

bituminous substrates, on gypsum

substrates, on plywood). Thesemembranes have a relatively low

cohesion and show some softening after

prolonged water immersion with a

certain risk of blistering. Forming an

impermeable film by physical drying,

these products are not suitable to be

applied under high humidity conditions.

Such products are not suitable for

exterior and floor applications and

cannot be used for applications with

permanent water immersion. In addition

there are disadvantages concerning the

logistics with liquid or paste-formproducts like risk of bacterial growth,

transport of water and expensive

packaging.

Installation and application ofcementitious waterproofingmembranes

Before applying cementitious systems,

the substrates must be free of dirt,

laitance, release agents, and other

foreign materials. The substrate must be

sound and solid, all tie holes honeycomb,and cracks must be filled with

appropriate cement mortars. When using

flexible waterproofing cementitious

slurries, construction joints, wall-to-wall

and wall-to floor joints must not be

sealed, for these joints an elastic sealant

(e.g. silicone sealant) or embedded

elastic plastic foils have to be used.

Cementitious waterproofing membranes

can be applied by brush, roller, trowel or

by an airless spraying machine. Mostly a

brush is used to apply a slurry-like mortar,

for this reason these products are very

often called cementitious waterproofing

slurries.

All cementitious waterproofing sealing

slurries or membranes have to be

applied in a such a way that after drying

a layer with a thickness of at least 2 mm

will result. This is generally obtained

only with multiple coating, mostly with

two or three coats (typical drying time

is 2 to 5 hours before application of the

second layer). In order to assure the

imperviousness of the membrane, at

least 2 coats have to be applied in order

to seal pores and micro cracks whichmay have been formed or left within the

first coat, even if a layer of 2 mm or more

could be applied in one step e.g. by

trowelling the slurry at 3 mm thickness.

It is not necessary to keep the freshly

applied polymer modified slurry moist

or to post-treat it with water, but it is

important to ensure that it can dry

slowly. Exposure to rain or excessive

sunshine must be avoided in the first

few hours, or, even better, for the first

day. For areas where permanent

hydrostatic pressure is anticipated, the

application of the adequate

waterproofing slurry must be done atthe positive side of the structure to be

waterproofed. If waterproofing

membranes should be used for drinking

water tanks, local restrictions about the

use of polymer modified mortars in

contact with drinking water have to be

respected.

Technical requirements andperformance of waterproofingslurries

Typical compositions for different classesof cementitious waterproofing slurries

are given in Table 1.


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Vinnapas is the commercial name for thermoplastic

polymer binding agents of Wacker Polymer Systems.

In combination with mineral binders (mainly cement

Vinnapas Redispersible Powders are used in theconstruction industry with great success for more

than 45 years.

Typical applications for polymer modified dry-mix

mortars are: ceramic tile adhesives and building adhesives,

jointing and grouting mortars,

thermal insulation adhesives and base-coat mortars,

self levelling mortars and screeds, concrete repair mortars and mortars for concrete

rehabilitation systems,

all types of plasters,renders and mineral finishing coats,

Technical requirements for waterproofing membranes (e.g. concerning flexural strength, compressive strength, tensile strength,

elongation at break, water vapour permeability, crack overbridging capability, water-uptake, impermeability under hydrostatic

pressure, adhesion on the substrate) are defined, based on more than 40 years of practical experience in Europe, together with theguidelines for the application for this type of products in the technical rules and recommendations of the Deutsche Bauchemie

(formerly IBH).

Table 1: Typical composition of cementitious waterproofing slurries

Type of waterproofing slurry A B C D

Flexural strength [N/mm2], after 28 d sc 5 - 10 8 - 12 * *

Compressive strength [/mm2], after 28 d sc 20 - 30 20 - 30 * *

Shrinkage [mm/m], after 28 d sc with 16x4x4 cm prisms 1 2 1 2 * *

Tensile adhesion strength [N/mm2] on concrete slab as a 2 mm layer

28 d sc 0,5 1,0 1,0 1,5 1,0 2,0 1,0 2,0

7 d sc + 21 d in water 0,5 1,0 1,0 1,5 0,5 1,0 0,5 1,0

28 d sc + 14 d 70C + 1 d sc 0 0,5 1,0 2,0 1,0 2,5 1,0 2,57 d sc + 21 d in water + 25 cycles freeze/thaw 0 1,0 1,0 1,5 1,0 1,5 1,0 1,5

Tensile test with 2 mm film at 23C, after storage 28 d sc (EN 196)Elongation at break [%] * * 10 - 100 10 - 70

Tensile strength at break [N/mm2] * * 0,5 2,0 0,5 2,5

Capillary water absorption [kg/m2.h], DIN 52617 > 2 0,2 - 2 0,05 0,5 0,1 0,5Water vapour permeability Sd [m], DIN 52615 0,05 0,4 0,05 0,4 1 - 5 1 - 5

Water impermeability test; no water penetration for 14 days 0 3 - 7 3 - 7 3 - 7

under a hydrostatic pressure of [bar], IBH guidelines

Crack-overbridging properties [mm], IHB guidelines 0 0 0,5 1,5 0,5 1,5* not to be determined due to low strength or low flexibility

A = simple, rigid cementitious waterproofing slurry with no resistance against hydrostatic pressure

B = rigid standard waterproofing slurry resistant against hydrostatic pressure

C = two-component flexible waterproofing slurry resistant against hydrostatic pressure

D = one-component flexible waterproofing slurry resistant against hydrostatic pressure

Type of waterproofing slurry A B C D

Portland cement or special cement 50 60 40 50 20 - 35 5 - 15

Filler (silica sand, special lamellar fillers, carbonates) compl. to compl. to compl. to compl. to

100% 100% 100% 100%Thickening agents (organic and mineral like bentonites) 0 5 2 5 2 5 2 5

Water retention agents (e.g. cellulose ether) 0 0,1 0,2 0,2 0,2

Defoaming agent 0 0,5 0,5 - 1 0,5 1 0,5 1

Vinnapas Redispersible Powder 1 2 2 10 0 5 20 40

Vinnapas Dispersion (50% polymer) - - 40 - 80 -

Table 2

If multiple layer systems are used in order to waterproof a construction structure, the modulus of elasticity of each coating should be

lower or at least not higher than the modulus of the layer below it, in order to prevent crack formation and failure of the system.

lime-cement paints and cement-free powder paints,

sealing slurries,

joint fillers,

trowelling and smoothing compounds.

Very simple products such as masonry mortars, thick-

layer screeds and base-coat plasters or renders are

usually not modified with Vinnapas Redispersible

Powders.

Vinnapas Redispersible Powders are polymer binding

agents that are produced by a spray drying process of

special water based polymer dispersions. Dispersionpowders were invented in 1958 by Wacker Chemie, and

today Wacker Polymer Systems is the world-wide

market leader for redispersible powders.

The polymer modification of dry-mix mortars with

Vinnapas Redispersible Powders will, depending on

the dosage, improve:

the water retention and the workability of thefresh mortar,

the adhesion on all substrates,

the flexibility and deformability of the mortar,

its flexural strength and

abrasion resistance, its toughness,

cohesive strength and

density (impermeability).

In addition, special Vinnapas Redispersible Powders

can confer a hydrophobing effect making the mortar

strongly water repellent. MBJ

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@waterproofing(72 76)

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