Natural stone can be classified into two general categories according to its composition: siliceous stone or calcareous stone. Siliceous stone (Granite, slate, sandstone, quartzite, brownstone and bluestone) is composed mainly of silica or quartz-like particles and relatively easy to clean with mild acidic cleaning solutions. Calcareous stone (marble, travertine, limestone and onyx) is composed mainly of calcium carbonate. It is sensitive to acidic cleaning products and requires different cleaning procedures than siliceous stone.
All natural stones are porous, made up of countless interconnected capillary pores through which liquids and gases can move. This is the most critical aspect of all the natural stones. It is understood that these natural beauties can get ugly patch marks on them due to their high absorption property. As a thumb rule, the experts say that the dark colored natural stones have low absorption and the light colored natural stones have high absorption. The reason why we prefer and use black/ dark green granite as the kitchen top or table top is that it has very low absorption and hence does not look ugly when in use.
On the contrary, all the light colored and white natural stones absorb liquid materials quickly and so the color of the liquid gets into the pours of the stone making it look ugly with patches on the surface of the stones. This phenomenon is called picture framing when the stone gets ugly on the borders due to absorption from stone edges as shown in the picture 1.1 and 1.2.
|Picture 1.1 (Picture Framing)||Picture 1.2 (Picture Framing)|
The absorption of stones also results in the following problems surfacing over a period of time:
|Rusting||Moss and Fungus formation||Discoloring or staining of stones|
|Chemical reaction with minerals in the Natural stones and hence change in color of stones||Soil accumulation (Stones like Travertine)|
Besides the above problems in Floorings, there are other problems which occur on the Natural stone installations on walls. Some of them are:
|Efflorescence||Permanent wet patches|
It is imperative that we take care of these natural stones to keep the natural look and yet sealing them from absorption of liquids. Let's look at the possible liquid attacks on these stones.
- Excess Water in the Traditional Cement Sand mortar mix installation method
- Water raising from the sub-layers of the flooring due to capillary action,
- Cutting of stones using wet cutting technology
- Curing water absorbed by the natural stone
- Water from the washing of the installed surfaces
- Spillage of food materials and beverages
- Spillage of paints, warnish and other coating liquids
- Excessive humidity in the environment
- Absorption of liquid from various adhesives used for various applications on the project site.
- Acid washing of the stones for keeping them clean and tidy.
How do we address this problem of absorption of Natural Stones?
- By creating a moisture free sub - base or underlayment below the stone so that there is no excessive free moisture to moving into the stone.
- By using a Polymer modified and Polymer fortified adhesive materials for installation of natural stones. They have a characteristic to absorb and utilize (for hydration) all the excess water used during the installation and also acts a water resistant layer between the substrate and the stone.
- By sealing the stones from absorbing the liquid materials. While doing so, we should not do this by coating of the surface with leak proof materials as they can form a water proof barrier on top or bottom surface of the stone and can spoil BREATHABILITY of the natural stone. This breathability is very essential for the stones as this phenomenon allows vapour to move freely through the stone, thereby releasing any stress that may have developed by restricting the vapour movement.
- Besides this, the very purpose of having the natural stone installation TO BE ONE WITH NATURE is defeated by external coating on the stone.
Latascreed 100 as a Surface Preparation MaterialLatascreed 100, Engineered cement powder, is best recommended for granite stone installation screed system where prevention of moisture ingression to the surface is of utmost importance. Latascreed 100 is chemically designed to incorporate self cure and self contain technology (SCT). The self cure technology (SCT) enables the Latascreed 100 to cure itself without need for any external addition of cure water. The self contain technology (SCT) prevents any excess water evaporation from the screed material during and after hydration. The other advantages of Latascreed 100, Engineered Cement, are:
- Water retaining and self-curing
- Interior and Exterior applications -12 mm to 60 mm thickness
- Flexibility to use local aggregates
- Flexibility to use with "wet on wet" or "wet on dry" adhesive systems
- Dimensionally stable-shrinkage free
- Meets or exceeds traditional screed system on compressive strength (3000 psi (21 Mpa)) for 4: 1 mix after 28 days
- Economical yet high performing
Polymer Modified Adhesive as a Bonding MaterialMYK LATICRETE's one part system polymer modified adhesives or a two part polymer fortified adhesive is highly recommended for marble/granite stone installation. These products are formulated to provide superior bonding and high flexibility to protect the stones from movement and stress. These formulations were chemically designed to have a very high water retention property. High water retention property helps the adhesive to cure uniformly and ensure the adhesive to retain all the excess hydration water from evaporating to the stone matrix. The various polymer fortified systems of MYK LATICRETE are listed in Table 1.
|Table 1: Product Guide for Moisture Free Stone Installation|
|L 226 + L 3642||Two Part system||M 30 Grade|
|Latascreed LS 100||One Part System||M 25 Grade|
|Polymer Modified Adhesives|
|L 252||One Part System||ANSI A 118.4|
|L254||One Part System||ANSI A118.4 and A118.11|
|L111+73||Two Part System||ANSI 118.4 and A 118.11|
|L111+4237||Two Part System||ANSI 118.4 and A 118.11|
|L290+333||Two Part System||ANSI 118.4 and A118.11|
|Latapoxy SP 100||Three Part System||ANSI 118.3|
|Aquashield||Powder to be mixed with L1776 grout admix||ANSI 118.6|
|Stone and Tile Sealer|
|Laticrete 190 Sealer||Water Based Stone and Grout Protector|
|Maxiseal Plus||Solvent Based High porous to Dense Stone Sealer|
LATICRETE 190 Sealer and MAXISEAL Plus as a Moisture BarrierDespite the screed and adhesive's superior moisture retention mechanisms, the heat generated during the adhesive hydration will result in some water evaporation and condensation of moisture on the stone surface. To prevent any such moisture transporting to the stone, we highly recommend to pre coat the stones on the bonding side as well all the four edges of the stone with LATICRETE 190 Sealer. LATICRETE 190 Sealer is an invisible, penetrating sealer which forms an invisible water repellant surface. It will not change the color of the stone. This sealer has an excellent compatibility with cement based adhesives and grouts. Once the stone is installed, the top surface should be sealed with MAXISEAL Plus. MAXISEAL Plus is a nano -technology based impregnating sealer designed for the protection of all highly porous tile/ stones and grout surfaces. This product imparts oleo phobic properties, highly resistance to oil, water, alkalis, acids staining and freeze thaw damages. It penetrates into the surface and forms an invisible barrier by allowing vapor to escape (breathability). It keeps the natural colour of tile & stone intact. All surfaces treated with MAXISEAL Plus are harder and less slippery. It is ideal for interior as well as exterior application and recommended for granite, marble, sand stone, porous slate, brick and sanded grout.
LATAPOXY SP 100 or Aquashield as a Grout MaterialIt is very critical that all the stone joints howsoever small have to be sealed with appropriate joint or grout material in order to prevent any water or harsh cleaning material penetrate in to the stone joints and subsequently to the stone matrix.
MYK LATICRETE offers two great grout systems for the sensitive stone installation systems. LATAPOXY SP 100 is a stainfree, color-fast, chemical resistant 100% Solid Epoxy Grout for tile or stone installation. This product provides 100% water and stain resistance and excellent abrasion resistance in heavy traffic areas like airport and shopping malls. MYK LATICRETE also offers hydrophobic cement based grout called "Aqua Shield" for the same purpose. This product has been specially formulated to have a high water resistance characteristics. When mixed with LATICRETE 1776 Latex admixture Aqua shield offers the same superior water resistance and stain resistance property as LATAPOXY SP 100.
However for best results, it is highly recommended to perform field test of minimum 10 sft to understand the absorption nature of the stone. Please refer to technical data sheet for installation instructions.
Dr. P Arjunan, V.P - R&D & Mr. N. Radhakanth, Sr. Manager - Technical Services - MYK LATICRETE, Hyderabad