Part 2-How to form Self - Leveling and What do you Think about It?

Part 2

 Types of SLS (Self Leveling Screed-Self leveling Mortar)

 To meet different market needs and specifications it is necessary to have more than one type of self-leveling. It is very difficult to deal with the different specifications with only one type of self-leveling. So usually the SLS are divided into 4 groups.

 SLC groups

 1. Low Cost - Composed primarily of cement and sand and a plasticizer.

2. 20-25 Mpa - to meet demands often in residential areas.

3. 25-30 Mpa - To meet demands light industry.

4. > 30 Mpa - to meet demands of the industry.

 This group is not strictly composition, many different variations can be made within these 4 groups presented above. The price is usually the driving force. Some companies may have a total of 5-10 different products within the four main groups. That is to optimize the cost for each application. The group n° 2 represents much of the self-leveling market in Europe and expansion in Brazil.

 Definitions of Types of mortars

 SCS-(Standard Cement Sand)-Mortar of cement and sand

The formulation is based only on the sand and Portland cement (OPC). The mortar is applied manually. The demand for this product in Brazil is high due to the low cost though there is a very strong job of introducing other systems. Typically this product is applied in thicknesses of about 40 to 50 mm. A thick lower layer will cause diseases such as cracks, due to the low tensile strength of the mixture.

 SLS-(Self Leveling Screed) Mortar Self Leveling.

 There are formulations based of Aluminous Cement, Portland cement and Calcium sulfate (HAC or OPC). The mortars from this group are pumpable, so using mechanized equipment to mix and pump. Normally the thicknesses are up to 30 mm, commercially speaking are available on the market, but it is possible applying thicker layers, although the cost will be the limiting factor and that technically can be avoided. The flow values must be greater than 150 mm for a ring (ring H = 22 mm and d = 50 mm) to be qualified for as an SLS. The minimum resistance to compression shall be 20 Mpa, although the resistance to abrasion is actually the most important parameter.

 ISLS-(Industrial Self Leveling Screed) Mortar self Leveling for industrial use.

 The basis of the formulation of this group is mainly of Aluminous Cement (HAC). This group also mortars are pumpable, so using mechanized equipment to mix and pump. Normally the thicknesses are up to 10 mm which are available in the market. The minimum resistance to compression is 30 Mpa. The industrial application the abrasion resistance is really the most important parameter to consider.

 4. specification.

 Let's look carefully for each of these factors below and see how we can summarize them to meet demand. The demands are variable, but what is more important to keep in mind is to know exactly what the profile you define the product. Without this dynamic, you will have difficulties to learn what their limits to reach them. Below are some of the parameters that we need to consider:

 

·Compression Resistance------------------------------ Which resistance value is?

.Mixing time--- The maximum time between the application of two consecutive lots.

·Internal or external Use-------------------- If it will use in the external or external.

·Type of flooring--------- How many must be the thick coating? your resistance to abrasion? how must be the surface to which it is applied?

·Substrate Type---------------------------------- Concrete, drywall or wood for example.

·Cost Price Late------ Row material with good quality, as we can use?

·Define Thickness---------- What is the thickness in mm, thin or thick.

·Drying time-------------------------------------------------------- Slow or fast.

·Environment------- identify the hazardous substance or what type of emissions can be.

·Patterns and standards to meet------------------- market requirements or Institute.

 Some of these factors may be in conflict with each other. You must define which of these factors are more important. The profile you set up can have a positive or negative effect and change the quality of the product. For example, to get to these properties, the raw material you have chosen can change what type of product you would use. In some cases, it may be difficult to define the desirable profile, some raw materials may not be available on the market or in the region. Then you have to reset your profile to your reality, change the product profile and rethink again. Many times you may have set an ambitious profile, but to serve you the cost will be high. In this case, the price is a very strong factor. In most cases, these assessments will define profiles with inferior properties. It is important to keep in mind that quality, high level, and high cost always go hand in hand.

An important thing to consider is that we should always focus on opportunities and not only the problems. Generally, define the specification and profile are hard work and to share the demands on various products to hit each profile for the best price. 

5 demands and actions

 I'm not going to enter the field of formulations but some adjustments can be obtained, to OPC-based formulations or HAC by changing the proportion of OPC/HAC with the goal to reduce costs and change drying time.

 And be careful on changes or combinations with the aim of reducing costs. OPC example gives a sulfate mixtures do not stable. Under conditions of humidity and rain may Sulphate OPC and generate a second expansion, called Ettringite late. This could be detrimental to the macroscopic structure of hardened material, for instance, can cause the formation of cracks.

Volume changes can, however, have the opposite effect, Retraction. There is a close relationship between the amount of cement in the mix and retraction.

 Another example of how we can improve the product profile is to hit the take time for mortars.

The applied manually, you need to have a long handle for handling larger than the pumped. That you can regulate handling fire retardant that you use.

In the case of pumpable Mortar, it is important that the mortar is mixed quickly and you can achieve this by adjusting or dispersants wetting agents.

 Coatings and interference in your profile and formulation

There are many different types of finishes, but we can divide them into 3 different types:

1- Flooring without glue. The lining is loose from the subfloor. The surface resistance force need not be very large. Just enough to deal with the resistance to understanding.

 2- Coat with glue. Type: PVC, linoleum and tiles, ceramics.

For example, the strength of the surface is important so that no coating material may lose grip with the sub floor SLS. The higher the applied load, the greater must be the surface force.

3- Industry. Base coating with epoxy. This type of flooring the subfloor SLS requirements are very high on the surface.

 Depending on the Substrate which will be applied if the SLS is porous or porous, concrete, wood, plaster, steel, plastic, PVC, linoleum you must adjust it with polymers, and Ether of cellulose.

 SCS and SLS are usually developed to be applied in concrete.

SCS and SLS however, can be used in other substrates, but due to the wide variety of conditions and environments, there are no general rules and consumer warnings, information concerning the use, must be given on presentation of the profile.

 Examples:

 Wood-often provides a good grip, but moves due to diffusion of moisture in the wood substrate usually cannot be avoided.

 Stone, tiles and bricks-Require pre-test to determine adhesion properties. Different types of hidrófobas substances may be present in these substrates that will compromise adhesion.

 -Steel requires a special type of flexible primer. Again pre-test is recommended. Because of the relatively high moving a steel substrate is also needed a flexible coating to ensure good adhesion.

 Important to note that in all substrate must be applied a primer that should be related to the type of flooring in most cases. The main reason for application of the primer is to avoid suction from the substrate, another reason is to prevent the air from the substrate can penetrate the SLS again and create bubbles and depression on the surface. The second benefit of the application of the primer is the increased resistance adhesion and connection between the materials. Sometimes two layers of the primer may be necessary.

 Strongly contaminated substrate surfaces require preparation prior to application of the primer. Usually, the epoxy base which in this case are recommended. Treatment of concrete surfaces contaminated with sand to increase adhesion on the substrate should be attentive to the sand grain size, must be related to the thickness of application of SLS that will be applied.

 Drying time

 We can divide the drying time into two categories.

 Setting time and Drying time.

Setting time ( Initial and Final Handle) the Handle time is important to assist the implementation of the SLS, how long the applicator has between one and another since the handle is important to know how much time you have to release the floor and walk on it after application. This point in the formula can be adjusted with accelerators, for example. (also see more details in Vicat). 

Drying Time (Total cure) means chemical drying, how long the binder material leads to a link with the water, which in the case of the SLS is the cement.

The higher the cement content the greater the reduction of free water content in the mixture, this water can cause water pressure, humidity. Important this item for a release of coating, adhesives, coating many types are only recommended to install after the time needed to heal. It is common to this type of problem because some works need quick release the floor over to application of coatings such as epoxy or Vinyl. (This information is important to the consumer) and reports it correctly can prevent complaints).

These two parameters must and can be of course be combined. 

Environment

 Some certifications require and require low-VOC products, for example, this is a market that is growing. Try to avoid products with high emissions. Normally this isn't a problem. Today there are low in SLS products construction market.

 Standards

You can often find different types of standards within the same country. In this case, follow the higher standard. The specification and profile of the SLS should be adapting to the current regulations. If no standard is in effect, required or available, you can compare the SLS with concrete.

Price.

 Each country has its own condition of your price and that price level that you can produce and accept, or what kind of raw material that you can buy. But save the raw material, you run the risk of never reaching the specification and meet the profile of the product. In this area of mortar, nothing is worse than not achieve specified quality defined in the profile.

 6. the Formulation

 To go ahead with the formulations it is necessary to go through these steps to a simple way to up here in my first article.

As we can see, some of these materials are more important than others and it means many important properties in the formulation.

 What should be in the formulation an SLS in a way summed up:

 Binders: Cement

Fillers: sand, Filler

Dispersing agents

Stabilizers

Accelerator 

Flame retardant,

Anti-caking agents

Polymers

Anti-retraction agents

Plasticizers

 7. Summary

 This article deals with a small part of the recipe.

The main idea of this article is to give you an idea of how a formulation of SLS can be, but we have a lot of work before checking the specs.

I'm going to highlight some important materials to finish.

They are:

 -                     Concrete type

-                     Polymers

-                     Dispersing agent

 These can control 3 important demands:

-                     Retraction/cracking control

-                     Flexibility

-                     Flow properties

 Well when these materials are under control, you can go further and get good results.

However, could not stop talking about the applicator that has a fundamental role in the application of cement to meet and identify your needs is another part that has aimed at another article comment. An example is when we have applications of low thickness up to 10 mm SLS that due to friction against the substrate flatness probably won't fill all depressions. Consequently, the final result depends to a certain extent the skill of the installer.

 Anselmo Policarpo. Manufacturer of Self Leveling- Email: anselmo@werden.com.br

 Anselmo Policarpo