General physical properties of ceramic materials include:-

General physical properties of ceramic materials include:-
1- Density:- there are three types of density:
a) Green density:- represents the mass of a material before firing divided by its total volume it is significant in:
* Consider a good indicator for material toughness (dry toughness), whereas increments in green density increase dry toughness.
* Consider a good indicator for interrelate process happening between grains after firing by comparison it with density of materials after firing. Green density increases by increasing
1) compaction pressure. 2) decreasing applied compaction rate. 3)decreasing particles hardness. 4)particle size. 5)particle size distribution.
b) Apparent density(bulk density):- it’s a ratio between fired mass and exterior
volume (total volume)
c) True density:- its also called true specific weight and it’s the ratio between fired
mass to the volume of solid part only and it’s a constant property for each material.
2- Porosity and water Absorption:- Most ceramic products can be classed as pores solids, in which the continuity of the solid matter is interrupted by voids of different kinds.
In general there are two main types of pores: open and sealed or closed pores.
Open pores are voids which are accessible to penetrate by a fluid they exist because of the imperfect packing of the particles of the material and also due to escape of gases during drying and firing processes.
Sealed pores are formed on firing when bubbles of gas are frozen into the glassy matrix, or when open pores are sealed by molten materials, so pores were isolated inside material. Two types of porosity
a) Apparent porosity:- is the ratio of the open pores volume to the total volume of the object.
b) True porosity:- is the ratio of the open and closed pores volume to the total volume of the object.
c) Water absorption:-is the ratio of open pore volume to the dry weight of the test piece.
2- Specific gravity:- is the ratio of material density to the water density at 4°C or it’s the ratio between ceramic material weight to the weight of water volume equal to the volume of solid material part.
In calculating these physical properties we depend on the ASTM standard (C-373-88) and each test result is the average of three samples.