Types of air lime and the impact of slaking

Matured Putty- Slaked by immersion and run to putty-Quicklime which is slaked by immersing in water and then matured under water with minimum agitation over differing periods of time. This produces a denser and less capillary active lime which should be used for fine finishes, ie. thin surface coatings. It is also more reflective due to crystal shape and orientation. Carbonates faster on the surface but slower at depth making it harder to tender when used in thicker applications. Produces more micro porous mortars with platelet and fine granular crystals. Poor capillary action. Especially when used with fibres which produces a more micro/macro porous mortar. Average adhesion. Poor water retention. Ph 12.  Excellent plasticity. High water content. High Strength (subject to correct tempering and tending). High potential for failure. No lime inclusions. Slow curing at depth, fast at surface.

Hydrated-Steam slaked and milled-Quicklime which is industrially partially slaked to a powder and then milled fine. Can be used immediately in the same manner as an NHL but can also be matured under water or with sand kept in a wet state producing a mortar similar to putty mortars with enough time. Produces more micro/mesa porous mortars with prism and spike shaped crystals when used immediately. Good capillary action. Maturing will alter it's state to closer match that of putty mortars. Poor to average adhesion. Poor water retention. Ph 12. Poor plasticity. Low water content. High strength. Low potential for failure. No lime inclusions. Average cure speed.

Hot Mixed-Steam slaked-Quicklime which is slaked on site by the gradual addition of water until a powder is formed. Not drowned with water to ensure that it steam slakes. Can be used immediately(used hot) sieved or not(lime inclusions) and/or left to temper after mixing with aggregates(used cold). Produces micro/mesa/macro porous mortars with platelet and granular crystals. Excellent capillary action. Excellent adhesion. Excellent water retention. PH 13,5. Excellent plasticity. Low water content. Low to mid strength. Average potential for failure. Lime inclusions. Fast curing. Best results when produced in a covered roller pan mixer. 

Hot mixed-Slaked by immersion-Quicklime which is slaked by immersing in water and then removing when slaked to a powder. A quicker less precise form of steam slaking. See above. 

Hot Mixed-Sand slaked-Quicklime which is slaked by banking in wet sand with the possible addition of water, then left covered, often overnight. Another form of steam slaking. Can be used immediately(used hot with lime inclusions) or left for an indeterminate length of time which is dependant upon the aggregates(used cold with far less lime inclusions). Some aggregates are unsuitable as they contain too many reactive components but most washed sands are fine. Crushed stone shouldn't be stored for a prolonged period of time, in the majority of cases. 

Hot Mixed-wet slaked-slaking wet without utilising the steam is not hot mixing. The lime must go through a dry state before a wet state to be hot mixed otherwise it is an unmatured putty mortar. 

'Perfect hot mixing';

The 'aeration' produces by steam slaking has many benefits, the heat is of less importance unless you are an excellent preparer and user of hot mixed mortars. It will increase adhesion with the aggregates and cure even faster if you can add precisely the correct amount of water immediately upon mixing with aggregates, later additions of water will severely impact it. Then use it whilst it's still very hot ...and beat it back at the precise moment. This entire process is a matter of minutes rather than days or hours. ie. slake the lime to powder then immediately mix with aggregates adding exactly the right amount of water for it not to remain wet or stiffen too early, never adding more, and use it immediately. This can cure almost fully within hours. Not easy but incredibly effective and easiest to achieve when using a roller pan mixer.  

When steam slaking, the remaining CO2 is driven out of the lime and carried away on the steam. This must be retained wherever possible and is an essential part of hot mixing as it seeds the mortar with carbon inducing a far shorter cure time. The steam also slakes the lime, producing a more porous material.  

Faster curing methods:

Steam slaking- allows faster and deeper penetration of atmospheric CO2.

Spirit of the Lime- retaining Co2 which is driven out during slaking.

Calcite seeding- use of carbonated lime as aggregate to seed with neo-formed calcite.

Slaking with organic additives- carbon seeding.

Milling- increased surface area. 

Perfect Mix- God knows...I have theories about this but it's all unproven. But essentially I think its predominately about carbon seeding and how stuff moves/reacts when hot versus cold. The heat and steam leaving pulls in atmospheric CO2 faster and deeper and it has that carbon from the Spirit of the Lime which was retained. I am 100% certain that there is another more complicated chemical/physical process involved too but your guess is as good as mine as to what. I guess it could be as simple as enhancing ionic exchange type stuff. Heat= faster reactions has to be part of it too.