Reply To: Catch Phrase

[Rematog]

If it is setting up that fast, it is something other than portland cement based concrete. Special addatives are used to get foundations to be ready to take a load in seven days. (referred to ash “High Early”). Normal, non-accelerated concrete cures for 14 to 28 days before use.

And cement does not DRY. That would ruin it. The cementous bond is formed by the water in the mix linking molecules together. It’s called a hydrolic bond. Care is taken to keep fresh concrete moist, so that it cures well and develops it’s full intended strength.

Don’t have any idea what they are proposing to use, but it is not regular portland cement based concrete.

From Wikipedia:

When water is mixed with Portland cement, the product sets in a few hours and hardens over a period of weeks. These processes can vary widely depending upon the mix used and the conditions of curing of the product, but a typical concrete sets (i.e. becomes rigid) in about 6 hours, and develops a compressive strength of 8~ MPa in 24 hours. The strength rises to 15~ MPa at 3 days, 23~ MPa at one week, 35~ MPa at 4 weeks, and 41~ MPa at three months. In principle, the strength continues to rise slowly as long as water is available for continued hydration, but concrete is usually allowed to dry out after a few weeks, and this causes strength growth to stop.

Setting and hardening of Portland cement is caused by the formation of water-containing compounds, forming as a result of reactions between cement components and water. Usually, cement reacts in a plastic mixture only at water/cement ratios between 0.25 and 0.75. The reaction and the reaction products are referred to as hydration and hydrates or hydrate phases, respectively. As a result of the reactions (which start immediately), a stiffening can be observed which is very small in the beginning, but which increases with time. The point in time at which it reaches a certain level is called the start of setting. The consecutive further consolidation is called setting, after which the phase of hardening begins.