Mixing heat resistant mortar without using a concrete mixer
Heat resistant refractory concrete
There are two ways, two types of heat resistant concretes that can be prepared. Cheaper and more expensive - stronger and weaker. The first one is a high heat refractory concrete. This type will survive in real high heat and can be used in hot-face (What is hot face? Hot face is a wall facing the main heat from a source. Internal walls, floor and arches made from firebricks inside a pizza oven is hotface. Firebricks face the heat, the hot flames from wood fire and the red hot embers.) Refractory concrete can be mixed with heat resistant cement, or, can be purchased ready in bags (the packed one is most often referred to as castable.) But saying that, even though it's refractory, still it is not so straight forward to cast large hot face section/s out of it. It is different to fill holes and awkward spaces with castables. Large blocks tend to crack as a result of something called heat differences in material, or temperature differences in material in other words, which is a very powerful natural phenomena. But hey no worries Mate, we still have firebricks here luckily (firebricks those nice little fragments) for making the dome part properly (read more about heat differences in materials - basically it deals with shrinking of cooled down edges and also surfaces while middle's still hot expanded).
It would be a wise idea to mix heat resistant cement, e.g. Calcium Aluminate cement, with firebrick grog. The grog comes basically from crushed firebrick/s. Companies who manufacture refractory material (like Claypave Pty. Ltd. in Dinmore, Qld. Au.), or those who only resell firebricks, usually sell also firebrick grog, ready premixed refractory mortars and fireclay. There are many different refractory cement types, some of them allowed to mixed in lime, plaster, or fireclay, but others cannot be mixed with these because