MichaelAlan, that is a complete and utter boo
Could we get some pictures of that?
Though I might go out on a limb and say that it might be possible that boiling the rock in acid
might have been a bit of overkill...
I could go into a whole spiel about what the industry says about Chloride and Cement. Sufficit to say, salt is not good for cement. Period. Especially cement destined for use in saltwater. And porous cement has a greater chance for failure than dense cement does. Which is sort of a "Catch 22" - we need the rock to be porous to fulfill its required duties, but by being porous it is at higher risk from Sulphate Attack and Chloride Attack.
And subjecting rocks to temps over 160°F (boiling acid???) can also cause problems - mainly in the form of ettringite, which can literally split rock apart. This is why I have been looking at other ways to make rock - the JRM currently uses high heat to create steam, but the high heat can potentially cause DEF (Delayed Ettringite Formation) - so can boiling rock to speed the kure - never let the water get above 160°F (the hottest most of our water in our houses are anyway) to avoid this problem.
Then, when you remove the Calcium Hydrates from the matrix of the rock, (kuring), you then further handicap the cement in terms of susceptibility. That is why I've been on the whole "carbonation" kick. If, instead of leeching the calcium hydroxide out of the rock, we encourage a carbonate layer to form, the rock has a higher resistance to chemical attack while still being safe to use - the carbonate layer "seals" the rock in a way.
And then this also sort of leads to
Lowfi's question. There most certainly are differences in cement. By slightly changing the composition of the materials used to form the clinker, cement can be changed to preform differently. In a perfect world, we would all have access to "Type 5 (V)" or "Type HS" cement - cement formulated to withstand the chemical attacks that sea water can bring against cement. High Alumina cement is also a choice for marine environments, but all of these types of cements are a denser, less porous cement, so again, the Catch 22. Though personally, if I could get it, I would use either Type V or HS.
Cement Types
Type I - Normal (Can be used)
Type II - Moderate Sulfate Resistance (Better than I)
Type III - High Early Strength (No point)
Type IV - Low Heat of Hydration (No Point)
Type V - High Sulfate Resistance (Best to use)
Type GU - General Use (Ok to use)
Type HE - High Early-Strength (Pointless)
Type MS - Moderate Sulfate Resistance (Better than I or GU)
Type HS - High Sulfate Resistance (Best to use)
Type MH - Moderate Heat of Hydration (Pointless)
Type LH - Low Heat of Hydration (Pointless)
Type HAC - High Alumina Content (Good/best to use)