Cold crushing strength (CCS) of a refractory brick represents its strength. That is it tells us how much load that refractory can bear in cold conditions. The concept of testing CCS of a refractory material has perhaps, come from metallurgy. This is because for any refractory brick it is rather; rare that it would fail simply due to load on it in cold condition and therefore, the determination of cold crushing strength does not appear to be important from that point of view.
But still testing of this property i.e. knowing the strength of the refractory brick is done to check some other properties which are direct result of strength such as ‘abrasion’. The stronger a material is the greater is the resistance to abrasion. Also stronger refractories are expected to have higher resistance to slag attack. The determination of cold crushing strength (CCS), however, is highly important in case of refractory insulating bricks where bricks have to be porous as well as strong.
It can be determined by following the steps given in any of the Standard Methods for Refractory Testing like - ASTM, Indian Standards (IS), Ghost, DIN etc. CCS of refractories is determined by placing a suitable Refractory Specimen on a flat surface followed by application of a uniform load to it through a bearing block in a standard mechanical or hydraulic compression testing machine. The load at which cracks appear in the refractory specimen represents the CCS value of the specimen. Load is to be applied uniformly and slowly, depending on the standard testing method followed, with a rate of load varying from 35 – 100 kg/cm2/min. Refractories being anisotropic in nature, the direction of load applied may be stated while reporting the results. The adjacent figure shows an assembly used for conducting the test.
(Fig. Courtsey: Indian Standards Institution, Ref. IS: 1528 of 1974, Part IV)
CCS = Total Load ÷ Total Area
Precaution must be taken that the refractory specimens must have the maximum possible original surfaces, have absolutely parallel and flat faces for applying load, and are free from cracks, voids etc. The size of the refractory test specimen (sample taken for testing) is usually equivalent to a 230 mm standard refractory brick except in case of smaller and other special refractory shapes where the test specimens are of smaller sizes or representative samples of 75 mm cube shape. The value of CCS can be expressed in either lbs. per square inch or kg/cm2.