The activation theory of slag in blended cement

As it is well-known, the activation of latent slag in blended cement is implemented by calcium hydroxide (CH, Ca(OH)2) which is the main cause maintaining the high pH value of pore solution.

The activation happens as the break of glass layer of slag particles. However, how does the break take place in detail? Researchers have already proposed a theory to explain the process, which will be discussed in the post. The main composition of glass is SiO2, thus the break of glass layer is actually the break of chemical bond between Si and O (Si-O). In the first step, the bond Si-O is broken by hydroxyl,

Then the other part of broken bond Si-O- further react with water (H2O), as the following reaction equation,

By the second step, hydroxyl is returned. The break of Si-O bond is finished. Therefore, the two steps can be combined into one equation,

From the overall process, it can be seen that hydroxyl acts as activator and is not consumed.

This is the theory which explains the activation of slag by CH in slag blended cement.

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