Mortars are the dagha for sticking bricks together. Every type of brick requires a mortar of the same chemical composition.

House-bricks are very inadequate dimensionally. Their geometric tolerances are also quite poor.  They are commonly laid with the mortar thickness of about 15 mm.  Refractory bricks are laid with a mortar thickness of 1 or 2 mm. 

Since the commonest bricks are aluminosilicate the commonest mortars are aluminosilicates. They have poor shelf lives. The best known of these is "Sairset", an air setting mortar, supplied ready mixed. It has a shelf life of about 3 months. Keramicalia's chamotte mortar has an even shorter shelf life and I recently discovered that after about 6 months sealed in a bucket you can't even break it with an axe.

More esteemed and widely used is "Blakite" of American origin. Delta asked me to develop an equivalent. It looked very easy. I thought it would take less than a week. Years later I am still not happy with it.  We call it "Kerablack". 

Most aluminosilicate mortars are supplied dry, and contain spray dried sodium silicate powders. These dissolve slowly. You have to wet mix them the day before use. This is counter intuitive to refractories installers. They don't stick very well. Fireclay can be used as mortar. A structure cemented with fireclay can be dismantled after years of service, which is sometimes useful. 

Kerasil mortar and CMR80 are almost pure silica. Kerasil has a very long grab time, making it perfect for arches, like pizza ovens and bad for straight up high walls. When you put mortar between bricks you can wiggle the top brick to get the mortar layer thinner.  The bricks suck out the water and after a time you can't wiggle them anymore. This is called grab time and is most commonly around 20 seconds. 

Kerasil mortar has a shelf life of years. CMR80 changes consistency during the first 2 weeks. 

CMR 80 is very popular, but most users think it is 80% alumina. We don't supply a data sheet with it. 

Chrome alumina mortars are bright green. Jade Set Super is popular as a mortar and as a coating to reduce metal and slag adhesion. Resitect is similar, also made with green chrome oxide.  Keramor 9 is our equivalent, but our Refractory Paint Green is more popular as a coating. 

"Air setting" mortars are sodium silicate based and get very hard on drying. Heat setting mortars are phosphate based. 

Alumina mortars are generally heat setting and can have long shelf lives. Our X9 mortar has a shelf life of 10 years. 

Magnesia mortars cannot be stored wet. Same with chrome mag mortars. I once cut a lot of chrome mag bricks and the wet grindings ran out of Factory 1 and became extremely hard and strong. Our mag chrome mortar tends to go hard in the bags.  We have a water free mastic which may be usable as a mortar, but is used more as a release agent.

We also have a zircon mortar. 

I want to make a graphite glue / mortar.

Mortar can be "buttered" onto the brick, which can be “picture framed”, or it can be made soft enough for dipping the brick into it. 

Properties of mortars:

Maximum particle size should be 500 micron or less.

When scooped up it must not slide off the trowel.

It should not settle out leaving liquid on top, but most do this to some extent and should be easily re-mixable. 

Grab time can be short or long depending on the application. 

It should not go hard during storage. 

It should stick very tight, and on IFB's the brick should break before the joint. 

The melting point should be almost as high as the brick. 

It should be soft and spread easily. 

Soft butter is a good consistency.