Mortar, Cement, and other Pookey

There are three main types of materials that can be used to install ceramic tile and stone. Each of these materials are used in what is referred to as the "thinbed" method of tile setting. The "thin" in thinbed refers to fact that the material bonding the tile or stone to the substrate is relatively very thin in cross section.

The thinbed method is contrasted by the older "thickbed" method. With the thickbed method, the substrate is produced and the tile/stone set and grouted in one step. The tile/stone is thus bonded with a relatively thick cross section of material.

For most of the jobs that we do, as well as virtually all projects undertaken by the DIY'ers that visit us here at the JB Forum, the thinbed method will be used.

The three main types of setting materials are:

1. Mastic

2. Portland cement mortar

3. Epoxy


Mastic is a latex or solvent based glue that cures by evaporation. Mastics are premixed and ready to use immediately. They have relatively low strength and water resistance as compared to cement mortar and epoxy. They are comparatively easy to use because there is no mixing or slaking involved, and because mastic grabs tile and prevents it from sagging. Home Depot, among other retailers, now sells something called "premixed thinset adhesive". This is not thinset in the traditional use, and is nothing more than mastic with sand in it.

On a case by case basis, your project may be suitable for the use of mastic. Please be sure to ask for advice on this before you start.

Portland cement mortar is what we typically refer to as "thinset". It is a mix of fine sand, portland cement, and other ingrediants to make it sticky, workable, and other desirable properties. It may be mixed with water only, a latex admixture, or come with powdered latex already in the mix.

All thinsets need to be mixed at the time of use, and all need to slake before use. Slaking is a period of time after mixing where all the dry and wet ingrediants continue mixing and reacting to yield a better, more workable mix.

Thinsets have tremendous strength, flexibility, water resistance, and virtually every other property that is desirable, when compared to mastics. Thinset will be the correct choice for your project in almost every case. Some types of natural stone, for example, require the use of epoxy. To be certain, be sure to ask us before you start for a recommendation for a particular type of thinset and possibly even a brand specific recommendation, based on what is available to you in your area.

One important note: thinsets are not a corrective material for substrate deficencies. Plan on using a trowel that gives good coverage on the back of the tile, with a thickness of thinset under the tile from 1/16" to 1/8". If this is not possible, you likely need to correct flaws in your substrate, and we will discuss those options separately.

Epoxy is very expensive, very strong, and generally not a user friendly type of product. You will need to use this to set tile/stone only in very rare situations. We will discuss the use of epoxy for projects that require its use.

[Edited by Rob Zschoche on 03-30-2002 at 11:29 AM]

[flatfloor]

Portland cement: A cement consisting predominantly of calcium silicates which reacts with water to form a hard mass.

In 1824 Joseph Aspdin of England invented portland cement by burning finely ground chalk with finely divided clay in a lime kiln until carbon dioxide was driven off. The sintered product (cause to become a coherent mass by heating without melting) was then ground and he called it portland cement named after the high quality building stones quarried at Portland, England.

Portland cement today, as in Aspdin's day, is a predetermined and carefully proportioned chemical combination of calcium, silicon, iron, and aluminum. Natural cement gave way to portland cement, which is a predictable, known product of consistently high quality.

Types of Portland Cement
Type 1
normal portland cement. Type 1 is a general use cement.

Type 2
is used for structures in water or soil containing moderate amounts of sulfate, or when heat build-up is a concern.

Type 3
high early strength. Used when high strength are desired at very early periods.

Type 4
low heat portland cement. Used where the amount and rate of heat generation must be kept to a minimum.

Type 5
Sulfate resistant portland cement. Used where the water or soil is high in alkali.

Types IA, IIA and IIIA are cements used to make air-entrained concrete. They have the same properties as types I, II, and III, except that they have small quantities of air-entrained materials combined with them.

http://www.concretenetwork.com/concr...tis/index.html

[John Bridge]

Here is a link to the Materials and Methods Standards Assn.'s bulletin on what latex and latex polymers actually do in thin set, grout and other portland cement products. Submitted by Jim Whitfield of Mercrete.

http://mmsausa.com/bulletin/14/