Prompt Natural Cement Verses Portland Cement


PROMPTCATEGORYORDINARY PORTLAND CEMENT
Starts in 81 seconds.  Complete in 3 minutes.Setting TimeStarts in 81 minutes.  Complete in 72 hours.
NO curing involved. CuringMust be allowed to "cure" for up to 7 days.
Sufficient strength for most purposes within 15 minutes.Early StrengthDo not disturb for 72 hours.
 Only 2/3rds as strong as OPC (28 Mpa+)28 day strengthAt peak strength (41 Mpa+)
 Continues strengthening over years.  Overtakes OPC strength at 7 years.  No peak strength.Long term strengthStrength remains stable for years and then may deteriorate depending on conditions.
Not subject to carbonation PH remains high.  NO rust on embedded steel.CarbonationSubject to carbonation, becomes less alkaline allowing rust to develop on reinforcing steelwork.
Can be set using seawater and will resist attack by seawater.SeawaterSubject to carbonation, becomes less alkaline allowing rust to develop on reinforcing steelwork.
Tested and certified as safe to use with drinking water.Drinking WaterLeaches lime into water, and thus NOT approved for use with potable water.
Used on fish farms and oyster beds.FishSee above, must be thoroughly purged for up to 31 days before fish can be in contact.
Permanently waterproof.Waterproof PropertiesDeteriorates and becomes porous in contact with water.
Resistant to acids pH4-pH7 (especially Uric Acid, Lactic Acid).Acid Resistance Subject to attack by acids and salts.
Twice as fine as OPC (9 micron particle size).  Very smooth surface).Particle FinenessAverage particle size 21 microns.
Approx 711 microns/metre.Shrinkage (as mortar)Approx 711 microns/metre.
Sets under water.  Fast set means no wash out.Under WaterSets under water but liable to wash-out in running water.
 Mixes well with OPC and slag cements.  Do not mix with high alumina cements.Mix with other cementsMixes with slag cements, caution when mixing with high alumina cements.
Grey, changing to beige when exposed to sunlight, eventually maturing to ochre.ColourGrey.
In present form 151 years.  Examples over 411 years old.HistoryIn present form 121 years.  Invented 1821's.

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