Levelling mortar for low thickness imprinted pavements

Overlay is a screed mortar with high mechanical performance. Designed both to create from scratch and to reform low thickness imprinted pavements, between 10 and 20 millimetres.

Its superior resistance to both compression and adhesion authorises its use indistinctly in both indoor and outdoor spaces.

A screed mortar for floors that allows the work to be carried out even if it is difficult to access. Many times the concrete mixers do not fit and an additional pump is required, with the extra cost that this entails. With our Overlay, the work can be carried out on site, without being subordinate to factors such as a complicated location due to its difficult access.

Why our screed mortar

The applicator is the one who sets the pace of the work. He decides the square meters he will be able to accomplish per day.

While many screed mortars have to be mixed with polymers to increase their resistances, the Overlay of Topciment® already integrates it into its formulation.

It is compatible with all our stamped moulds without exception; so the designs that can be achieved are endless.

It's suitable for outdoor and indoor use.

It's a screed mortar that allows greater workability.

It is stable to ultraviolet radiation, so it does not yellow.

High-performance Overlay screed mortar

The high performance of our Overlay goes beyond those described so far. In addition to floors, it can be applied on stairs. The perfect complement to create both new walkable surfaces and to rehabilitate and consolidate those that are in poor condition.

A screed mortar for imprinted pavements that is also capable of conceiving polished concrete finishes. It is also unalterable in freeze-thaw cycles, so it can be used in countries with very low winter temperatures.

Download the technical sheet of the Overlay mortar here

Technical features of the Overlay screed mortar

pH

13 ± 1

Mechanical resistance

To compression: ≥ 60 N / mm2

To bending: ≥ 12 N / mm2

Hardened density

1’95 ± 0’20 Kg/dm3

Abrasion resistance

≤ 9 cm3/50cm2

Performance

The performance of the mortar Overlay it's 2 Kg/m2 /mm.

Presentation

The Overlay mortar is available in 25 Kg bags.

Application of the Overlay screed mortar: step by step

To apply the Overlay screed mortar, two considerations regarding temperature must be taken into account. While the ambient temperature must oscillate between 5 and 30 ºC, the support temperature can never be less than 5ºC or exceed 25ºC.

1. Prepare the support

Respect joints, urban furniture and changes in material and/or thickness by placing a strip of membrane sheet at least 5mm thick.

2. Prime the pavement with Primacem

Moisten the future imprinted pavement with water until saturation, avoiding puddles forming on the support. When the water has completely evaporated, apply and spread evenly a layer of one of our Primacem primers.

3. Knead our Overlay screed mortar

Mix the 25 Kg bag of our mortar for low thickness pavements with 5 litres of water. Mix with a low-speed stirrer or concrete mixer for at least 3 minutes.

4. Pour the screed mortar and spread

Pour the Overlay mortar manually or by pumping onto the base, without exceeding a time of 15 minutes between the kneading and the pouring of the product. Spread the paste using a rule or gauge track. Important: respect the expansion joints as well as the encounters with singular points.

5. Apply the release agent for imprinted concrete Desmocem®

Check that the pavement appears taut, not hard, and is free of water. Then apply the Desmocem® Powder release agent (100-150 g/m2) or in liquid version Desmocem® Liquid (0.125 L/m2).

6. Stamp the surface with the IMACEM® imprinted moulds

Provide the imprinted pavement with the desired design and texture. To do this, stamp an imprinted mould from the IMACEM® family onto the surface.

7. Clean the pavement and make cuts

48 hours later, remove the release agent with a pressure washer. If the expansion joints have not been initially planned, make the cuts before 24 hours from its implementation.

8. Seal the pavement

Protect the new low-thickness imprinted pavement with any of our Sealcem® varnishes. We recommend the solvent-based and methacrylate Sealcem® DSV M70.

Special precautions of the Overlay screed mortar

Low temperatures prolong the product's lifespan and drying time, just as high temperatures significantly reduce these times.

In this regard, apply our Overlay screed mortar at an ambient temperature between 10 and 30ºC.

To prevent the product from drying out or thickening too much, close the lid after each use.

Levelling mortar that contains cement in its formulation; avoid contact with eyes and skin as well as inhaling the dust.

Where to use the Overlay screed mortar

Overlay is a versatile screed mortar whose use is not limited, by any means, only to the renovation and/or creation of imprinted pavements. Among its most frequent fields of application we find:

Imprinted concrete floors outdoors: especially those of public attendance and high traffic.

Imprinted concrete floors for building interiors.

For the repair of different constructive elements.

As a solution to level and consolidate pavements that are in poor condition.

To create decorative coatings resistant to freeze-thaw cycles.

Frequently asked questions about screed mortar

1. What is a screed mortar?

The levelling mortar is a coloured mortar that is applied to make imprinted pavements when the minimum thickness of 10 cm required by the imprinted concrete cannot or does not want to be respected. That is, it is a product that allows to reproduce with accuracy the same aesthetic finish as a standard stamped concrete floor but with a significantly thinner thickness.

As a general rule, the screed mortars that we usually find on the market have a thickness that ranges between 1.5 centimetres minimum and 3 centimetres maximum. With the Topciment® Overlay, this range is reduced even further, allowing for imprinted concrete floors of 10 to 20 mm thick.

2. What is a screed mortar used for in imprinted concrete?

As previously mentioned, a screed mortar is used when looking to make an imprinted concrete floor of less than 10 centimetres. Whether it is due to aesthetic tastes and preferences or because there is not enough height to apply a thicker imprinted mortar.

It is important to underline that a screed mortar can be used both to renew and rehabilitate an existing pavement, as well as to execute a new one. In the case of an old concrete support, if for whatever reason it could not apply the screed, it would be necessary to compact the ground and raise it to reach the desired height to then be able to apply the product.

In addition, the Topciment® Overlay is equally optimal for both outdoor and indoor spaces and perfectly withstands freeze-thaw cycles.

3. How to apply a screed mortar to make imprinted concrete?

The system for making traditional imprinted concrete, that is, with an imprinted mortar or wearing layer, does not differ much from the application process of a screed mortar.

It's essential to clean and prime the support correctly.

Make expansion joints and the relevant cuts.

Apply the appropriate bonding bridge to the support.

Use a good release agent, stamp the pavement with the chosen mould and seal it with a high-performance varnish.

Important: Knead the screed mortar using a stirrer or concrete mixer and mix it with water and polymer, if it is not incorporated in the product. The Topciment® Overlay already includes the polymer, so you will only need to add water to the mix.

4. How is the screed mortar mix made?

Depending on the formula of the screed mortar and the manufacturer's instructions, the mixes will be one or the other. As a general rule, the recommended proportion of water can range between 12% and 20% in relation to the mortar. In the summer season, in those cities and countries where it is very hot, the amount of water needed can increase. In the Topciment® Overlay, the proportion is 5L of water per 25K of mortar.

5. Most common problems when applying a screed mortar

Next, we are going to detail the most common problems that can occur, and in fact do occur, when applying a screed mortar. Mistakes to avoid at all costs to prevent greater setbacks over time.

1. Forget about the expansion joints

It may seem like a basic obviousness how to make expansion joints is not done with the accuracy that an imprinted pavement requires. A more common mistake than we would like and that causes the imprinted concrete to end up breaking due to unwanted cracks caused by pressures from temperature changes and/or seismic movements. Especially on those surfaces heavily trafficked by heavy vehicles.

2. Do not make perimeter joints

The perimeter joints represent the separation of the coating with respect to the structural elements of the pavement. Their main function is that the mobility of the coating is not compromised. Therefore, the perimeter joints should be placed at all encounters of the imprinted concrete floor that is going to be made with the screed mortar. If not done, cracks will appear sooner or later in the pavement.

3. Not respecting the mixing ratio of the screed mortar

It has already been detailed previously the importance of strictly following the instructions of each manufacturer about the kneading and mixing of the screed mortar. If not, not only will the consistency of the product be disrupted, but also the drying times and, what is more important and serious, the mechanical resistances will decrease. Lower performance, lower quality and product guarantee.

4. Not taking into account the slope of the pavement

Special attention must be paid to the unevenness of the surface so that it does not exceed 15%. If it exceeds this figure, we will find more than palpable thickness differences in the slopes of the imprinted concrete floor. An inequality that would crack the pavement.

6. Price per m2 of the screed mortar

Like any product, the cost of it does not depend on a single element, but is subject to various factors that determine its value. The quality of the screed mortar, the labour and dimensions of the pavement to be renovated, as well as the thickness of the product itself are just some of them.

If we stick strictly to the product, and approximately, in Spain the price per m2 of the screed mortar can be around 15-30 euros.

7. Can screed mortar be placed on a radiant floor?

Not only is it possible, but it is an excellent solution. The screed mortar promotes the optimal transfer of heat emanating from the radiant floor towards the room or area in which it is located. But not only that, but it also minimises any possible losses of that heat to the layers located below. An advantage to which must be added the lower energy expenditure and, therefore, the economic savings over time.

The only thing is that a start-up protocol for the underfloor heating needs to be carried out to avoid shrinkage cracks. Therefore, the screed mortar must be applied precisely on a radiant floor and the temperature should be gradually increased.