[Strawbale] Rlimestone screenings

[Chris Green]

Rob Tom wrote:
> Limestone screenings (aka "stone dust") are the fines left over from  
> grading crushed limestone; particle sizes typically from under 3/8" and on  
> down.
>   

<snip>
> Compaction obviously creates more surface contact between the particles,  
> and I suspect, creating more opportunities for bonding.
>
> I suspect that what's happening is not unlike the process of autogenous  
> healing that occurs with lime mortars.
>
> My guess is that crushing the stone exposes virgin carbonation-susceptible  
> surfaces that were previously cut-off from CO2 in the atmosphere and in  
> rainwater.
>   
Your guess is probably quite accurate: the fines will have much more 
surface area exposed., Since the parent limestone deposit will probably 
have a lot of calcium carbonates which have not had the opportunity to 
undergo complete carbonation, exposure to fresh carbon donor materials 
(i.e., CO2 ) over a much larger area will allow the carbonization 
process to be completed.
> The degree to which compacted limestone screenings resembles (no fines)  
> concrete seems to depend upon the degree of compaction and the amount of  
> time the compacted mass has had to age.
>
> Of course, the material will never be a dead ringer for 35 MPa concrete in  
> terms of appearance and strength but as a road base or floor base it does  
> the job extremely well.
>   
Crushed limestone can also be used in rammed earth or, now, S.I.R.E.wall 
earthen construction. The bottom left hand photo at this page shows the 
first house built in Canada using rammed crushed limestone.
http://www.solumbuilders.ca/

Meror Krayenhoff and the folks at Terra Firma Builders sometimes use 
limestone tailings- the powder left over from screening the rock--as 
part of their Stabilized Insulated Rammed Earth, or S.I.R.E. wall mix.

http://www.terrafirmabuilders.ca/

http://www.sirewall.com/

There are many more rammed crushed limestone houses around; most of the 
ones I've come across are in the UK.

Not many Limestone Cowboys over here at this time.


Cheers,

Chris Green.