Acid Insoluble Residue

Acid insoluble residue is a standard laboratory test for cement. All the clinker in cement is soluble in acid  it is a measure of proportion of the non-clinker material in cement. Usually clay minerals added with the gypsum. In CEM 1 or pure Portland cements it is a measure of the added filler. It has less meaning with blended cements such as CEM 2.  

Dear Michael ,

 My inquiry is in reference to Rawmix.

Sincerely Yours,

Gulam Dastgir

In the rawmix, the acid insoluble residue can give an approximation of the crystalline silica content. Cyrstalline silica being very refractory and diffciult to combine, it is important for assessing the burnability of the raw mix. To get an accurate measurement of crystalline silica content, one should use microscopy, which is a difficult and time-consuming process. This is why acid-insoluble residue is often used as an approximation.

To assess burnability, the acid insoluble residue should be determined on different sieve residues. It is generally admitted that crystalline silica particles > 50µm will not combine completely.

As an example, here is a formula from FLS institue to assess burnability:

(Free Lime at 1400°C) = 0.35*(LSF-96) + 1.58 (MS-1.6) + 0.55 * (Acid insoluble residue > 45µm) + 0.12 * (total residue > 125µm)