Free calcium oxide analyzer

FC17AFree calcium oxide analyzer

Related standards: GB/T 176-2017 "Methods for Chemical Analysis of Cement"

The significance of measuring free calcium oxide

During the calcination process of cement clinker, the vast majority of calcium oxide can be combined with acidic oxides (SiO2, Al2O3, and Fe2O3) to synthesize minerals such as calcium silicate, calcium aluminate, and calcium ferroaluminate. However, due to factors such as raw material composition, raw material fineness, raw material uniformity, and calcination temperature, there is still a small amount of calcium oxide in the cooked material that exists in a free state instead of a chemical state, commonly known as free calcium oxide (f-CaO).

Free calcium oxide mainly includes:

1、 Low temperature free calcium formed due to undercooked clinker, also known as undercooked free calcium, has a loose and porous structure, reacts quickly with water, and has little harm to the stability of cement;

2、 Due to the high saturation ratio of raw materials, low amount of flux minerals, coarse or uneven mixing of raw materials, and insufficient residence time of clinker in the burning zone, high-temperature unreacted free calcium, also known as primary free calcium, is generated. This type of free calcium has undergone high-temperature calcination and is wrapped in clinker minerals, with a relatively dense structure that is not easy to hydrate, posing a great threat to the stability of cement;

3、 Due to the slow cooling rate of clinker or the presence of water vapor, secondary free calcium oxide is produced during the decomposition of clinker. This free calcium hydrates quickly and does not affect the stability of cement, but it can reduce the strength of clinker.

From the above content, we know that free calcium oxide directly affects the stability of cement and has a certain adverse effect on strength. It is an important indicator for measuring the quality of cement clinker. Therefore, determining the content of free calcium oxide in clinker and cement is particularly important for controlling cement production and ensuring the quality requirements of cement.

Principle of measuring free calcium oxide

After mixing cement samples with glycerol ethanol solution, free calcium oxide in the clinker combines with glycerol to form weakly alkaline calcium glyceroate, which dissolves in the solution. Phenolphthalein indicator makes the solution appear red. Titrate the generated calcium glyceroate with anhydrous ethanol solution of benzoic acid until the solution fades. The free calcium oxide content can be calculated from the consumption of benzoic acid.

FC-17AFree calcium oxide analyzer

The results of free calcium oxide measured by FC-17A cement free calcium oxide rapid analyzer meet the requirements compared with the national standard sample, and the quality is more guaranteed.

FC-17A cement free calcium oxide rapid analyzerIt is an instrument designed based on the ethylene glycol extraction benzoic acid titration method in GB/T 176-2017 "Methods for Chemical Analysis of Cement". It is specifically used to accurately and quickly detect the content of free calcium oxide in cement clinker and is suitable for various testing institutions, cement enterprises, concrete mixing plants, research institutes and other laboratories.