making concrete more sustainable

Dale Hodgins wrote:For me, glass is primarily a disposal issue, since I haven't seen much that I would like to replicate, in the bottle glass category. I have used it effectively, to replace some of the gravel, when mixing concrete. Gravel is very inexpensive, so it's not about any cost savings. It's about not having a buildup of glass which  ends up mixed with soil in so many cases, if left lying about.

I have seen a few art glass items, made from recycled glass. Some of them are quite nice. But, when I look at the quantity of fuel burned, to turn a pound of glass into something useful or decorative, I always come back to the idea of just getting rid of it in concrete.

since concrete is not exactly sustainable, is this really a sustainable solution? can crushed glass be used in hempcrete (a sustainable form of crete)?

michael beyer wrote:

since concrete is not exactly sustainable, is this really a sustainable solution? can crushed glass be used in hempcrete (a sustainable form of crete)?

I cannot see how hempcrete is any more sustainable than concrete made with reused glass, both require open cast mining of materials, and tons of energy in their creation.

Skandi Rogers wrote:

michael beyer wrote:

since concrete is not exactly sustainable, is this really a sustainable solution? can crushed glass be used in hempcrete (a sustainable form of crete)?

I cannot see how hempcrete is any more sustainable than concrete made with reused glass, both require open cast mining of materials, and tons of energy in their creation.

from my understanding, hempcrete is made from hemp (a renewable resource) and lime(stone)

is the mining of limestone especially ecologically destructive?

Turning limestone into Portland cement takes a lot of heat,  usually in the form of fossil fuels.
It's a very energy intensive process, so things built with Portland cement have a high embodied energy.

If hempcrete uses Portland cement in the same amounts  as other 'cretes then it's still might have an edge in that the hemp is effectively sequestered carbon.

On the other hand,  are crucial nutrients tied up in the hemp?
Would we better off composting the hemp, feeding it to animals,  turning it to biochar, wearing it as clothing,  writing in it as paper, running it through a biodigester for fuel,  eating it,  processing it into medicine  or something else?
Some if these things can be done consecutively, and might leave enough fiber to still make hempcrete.

I think every container sold should have a deposit on it,  high enough to make not recycling them a luxury for the well to do.

Meanwhile,  a solar powered tumbler could turn glass into a safe and useful aggregate.
It still might be cost prohibitive,  and direct solar heating might be a better choice.

I wonder if glass could be set up to be melted via solar and automatically fall into water or oil, and what the resulting product would be.

William Bronson wrote:

If hempcrete uses Portland cement in the same amounts  as other 'cretes then it's still might have an edge in that the hemp is effectively sequestered carbon.

hempcrete doesn't use portland cement — it uses lime

michael beyer wrote:

William Bronson wrote:

If hempcrete uses Portland cement in the same amounts  as other 'cretes then it's still might have an edge in that the hemp is effectively sequestered carbon.

hempcrete doesn't use portland cement — it uses lime

Lime is created by burning limestone, that means some fuel has to be burned to make it.

Redhawk

Using hemp for any of the other valuable uses you mention will not get your slab poured or your house built, so it's sort of apples to oranges. The idea of using the residual hemp fibers rather than the whole plant is a good one but sourcing waste fibers is probably not as easy as sourcing the whole plant.

michael beyer wrote:



is the mining of limestone especially ecologically destructive?

Sorry I missed this, no more destructive than any other open cast mining,

one of many mines in Denmark

michael beyer wrote:

William Bronson wrote:

If hempcrete uses Portland cement in the same amounts  as other 'cretes then it's still might have an edge in that the hemp is effectively sequestered carbon.

hempcrete doesn't use portland cement — it uses lime

Sorry, Michael, I am not contradicting you, but the institution that put the idea out trying to distinguish lime from cement.  This kind of green washing is all too common.  The idea put forth that hempcrete is "sustainable" that it uses "lime", which as noted is produced the same way as portland cement.  

It is so exhausting to have to fact check everything, isn't it?

Thekla McDaniels wrote:

Sorry, Michael, I am not contradicting you, but the institution that put the idea out trying to distinguish lime from cement.  This kind of green washing is all too common.  The idea put forth that hempcrete is "sustainable" that it uses "lime", which as noted is produced the same way as portland cement.  

It is so exhausting to have to fact check everything, isn't it?

I've researched further and you are correct. It seems limestone or "lime" is a main ingredient in Portland cement as well. Perhaps hempcrete is more sustainable in that it doesn't have to go through as many industrial processes to produce it? It especially doesn't need to be heated to such a high temperature. Also, there are claims it is carbon negative after some time as it sequesters carbon. I don't know if these claims are true or not, but in some senses, it may be considered more sustainable than Portland cement but it still has the ecological consequences of mining limestone whatever those are. What do you think about this?

Thekla McDaniels wrote:
Sorry, Michael, I am not contradicting you, but the institution that put the idea out trying to distinguish lime from cement.  This kind of green washing is all too common.  The idea put forth that hempcrete is "sustainable" that it uses "lime", which as noted is produced the same way as portland cement.  

It is so exhausting to have to fact check everything, isn't it?

This article also claims the ability to source lime binder components locally. How they define "locally" and how the process of mining effects the overall ecology is not clear though.

https://www.greenbuildermedia.com/buildingscience/hempcrete-keeping-it-local

Thekla McDaniels wrote:
Sorry, Michael, I am not contradicting you, but the institution that put the idea out trying to distinguish lime from cement.  This kind of green washing is all too common.  The idea put forth that hempcrete is "sustainable" that it uses "lime", which as noted is produced the same way as portland cement.  

It is so exhausting to have to fact check everything, isn't it?

This seems to be the most comprehensive scientific paper studying life cycle analyses of 36 different formulations of hempcrete. It seems their conclusion is that many formulations of hempcrete are carbon negative, especially the formulations which do not include Portland cement.

https://www.sciencedirect.com/science/article/abs/pii/S095965262031893X

You can find other less comprehensive life cycle analyses through a search like this as well...

https://duckduckgo.com/?q=life+cycle+analysis+of+concrete+vs+hempcrete&t=iphone&ia=web

I would love to know the negative ecological consequences of mining limestone and producing limebinders outside of the context of just calculating carbon-score and embodied energy. Are these types of considerations taken into account in life cycle analyses or do I need to start an organization that takes some of these other factors into account? xD