Dear Rayan;
Yes! – You are doing right.
For SiO2:
As first reaction the also first & second reactions under “Hardening” on: "Portland Cement (http://en.wikipedia.org/wiki/Portland_cement)”
- takes place (Maybe the Ammonium chloride gives a better precipitation.)
The use of HCl speeds up the reaction and builds the soluble Calcium Chloride.
Therefore take a look under: "Calcium Chloride (http://en.wikipedia.org/wiki/Calcium_chloride)”
Good Luck!
ARGOS++