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Technical Information

Pratliperl – Thermally insulating and Fireproof Plaster

Mixing Cement with Pratliperl

In order to achieve an homogeneous mix, Cement must be mixed into the Pratliperl in a “dry state”. What this means is that before adding any water to the mix, one must mix the Pratliperl and Cement together until the entire mix is light grey in colour. Remember that mixing the correct ratio of Cement to Pratliperl is imperative. These ratios may be found on the back of every bag. Ratios are all Volume based which means that a 3:1 ratio means that three wheelbarrows of Pratliperl must be mixed with one Wheelbarrow of Cement. It does not mean that 3 bags of Pratliperl must be added to 1 bag of Cement.

Adding Water to the Pratliperl Mix

Before adding any water, ensure that the Pratliperl and Cement is mixed together in a “dry state”. What this means is that before any water is added, the dry Cement and Pratliperl must be mixed together until the mix is the same light grey colour throughout. Only once a homogeneous dry mix has been achieved should water be slowly added to the mix. Correct Water quantities are illustrated on the back of each Pratliperl bag. One must stick to these quantities as adding too much water during the mix will lead to poor results.

As with ordinary concrete and Plasters, once the Pratliperl screed of Plaster has been applied, it is recommended that the newly applied Pratliperl surface is kept damp. This process will ensure proper curing of the Cement and prevent the material drying out too quickly.

Using the Correct Mix Ratio

Mixing Pratliperl correctly and in ratios appropriate to the required application is imperative. Mixing ratios are both graphically and empirically displayed on the back of each and every bag. One must however remember that a 3:1 mix ratio does not mean that three bags of Pratliperl must be mixed with one bag of Cement. What this 3:1 ratio means is that the volume of Pratliperl used must be three times more than the volume of cement used (i.e. Three Wheelbarrows of Pratliperl to one Wheelbarrow of Cement).

On the back of each and every Pratliperl bag is a suitability chart. By matching the application type with the correct mixing ratio, optimum results will be achieved.

Water Permeability

Water Permeability tests on Pratliperl concrete were conducted by the Portland Cement Institute of South Africa. Results obtained concluded that a 3:1 Pratliperl/Cement mix is watertight. As with ordinary screeds, we do however recommend that Pratliperl Screeds where there is possibility of water accumulating be waterproofed. Conventional waterproofing materials including those applied using heat may be used.

Pratliperl Fire Resistance

Fire resistance tests conducted by the CSIR revealed that Pratliperl concrete has a 4 hour fire rating. Results also established that Pratliperl Concrete in non-combustible and does not liberate smoke or toxic gas during a fire. This is one of the reasons why Pratliperl is preferred to other insulating products such as expanded polystyrene foam which emits deadly fumes when exposed to fire.

Calculating the Correct Amount of Bags

As a rule of thumb, 11 bags of Pratliperl are required to produce one cubic meter of Pratliperl concrete/plaster. Approximately 62 square meters of a wall can therefore be plastered 16mm thick using 11 bags of Pratliperl.

Pratliperl is Non-Toxic

Fire resistance tests conducted by the CSIR revealed that Pratliperl does not liberate any toxic fumes when exposed to fire. This is of particular importance when selecting an insulating material as many materials such as expanded Polystyrene emit dangerous fumes during a fire.

Pratliperl Types

The company supplied two types of Pratliperl. These are easily identifiable by merely looking at the colour of the bag. “Pratliperl for Plaster Screed and Concrete” has red writing on the bag whereas the other Pratliperl bag has black writing on the bag.

Pratliperl in the black bag is primarily used as a loose fill insulating material whereas Pratliperl in the red bag has been treated so that it is compatible with Cement ultimately rendering it suitable for any applications where Cement is required (I.e. Screeds, Plaster, Lightweight Castables)

Pratliperl’s Exceptionally Smooth Finish

If applied correctly, Pratliperl plaster gives an extremely smooth finish. Finishing plasters used to get walls smooth before painting are therefore not necessary, ultimately saving cost.

What type of Cement should I use with Pratliperl? For Plaster applications a reputable 32.5N Cement is adequate. Screed applications, where greater compressive strength is required, a 42.5N of higher Cement is recommended.

Industries using Pratliperl concrete in refectory environments may use a High Alumina Cement.

Pratliperl Curing Times

Curing times are similar to those of ordinary Concrete and plaster. Before applying a straight edge to Pratliperl plaster a simple “Thumb Test” can be used to determine if the plaster is dry enough for the straight edge. This test is done by simply pushing your thumb onto the Pratliperl plaster. If a small dent is made in the plaster, a straight edge may be used. If a large dent occurs, more time is needed before a straight edge is applied.

As will all concrete mixes, 28 days is required until the material reaches full strength.


Any form of waterproofing, including membranes applied using a torch may be used.


Loose fill Pratliperl (i.e. Pratliperl that has not been mixed with Cement) has a density of approximately 100kg’s per cubic meter. Practical Pratliperl Concrete densities ranging from 300 to 800kg’s per cubic meter (i.e. Concrete that can even float on water) can be achieved. One must remember that by adding more Pratliperl to the mix, the density as well as the strength of the concrete will be lowered.

Use Pratliperl for Texturizing

Pratliperl may be added to ordinary paint in order to texture and bulk up the paint. This process produces an attractive surface which will ultimately hide and reduce the occurrence of the Paint cracking. A finer product called Thermoperl may also be used to create a finer textured paint.

Applying Pratliperl to Smooth Surfaces

As with all plasters, with a bit of preparation, Pratliperl plaster can be applied to smooth surfaces. To improve adhesion, smooth surfaces should either be chipped or a slush mix applied to the wall before plastering. A suitable slush mix can be produced by mixing Cement, Pratliperl, River sand, Pratley Plaster Grip Primer. This mix can then be splashed onto the wall and allowed to dry before Pratliperl plaster is applied.