making cement with black cinder

[flowerhill]

Hi I am looking for info and experience of using cinder & cement to make concrete. I have a pile of black cinder, and a desire to make stepping stones. I also have a cement mixer, so I hope to do apx 2x2'-3x3' pads.
Any advise gladly appreciated

[Rob Tucker]

There is nothing wrong with this in a non structural use such as stepping stones or pavers. Volcanic cinder has been used for ages for light weight concrete. The cinder is lighter than crushed granite. Red cinder is preferred as it is stronger than black cinder so you may have to experiment a bit with thickness to get a durable paver or use some steel reinforcement. Black cinder is more fragile. That is why red is use for roads and black for agriculture.

[PauHana]

Google pumice-crete. It's interesting stuff.
I seem to remember reading it comes out at about 600 psi. I don't see it working as stepping stones unless they are very thick.

[Wao nahele kane]

Sort of on this topic - does anyone know a good source for bulk Perlite both coarse and fine?

Flowerhill - I'd like to add the following with regard to use of cinder and or any of the island sourced aggregates. Keep the following in mind - mixes using our local aggregates are not equal to using most mainland aggregates that are relatively smooth surface stones.
1) It's a good Idea to add a small amount of detergent to your mix to establish slip when using local aggregates, (detergent is a final additive and only use liquid dish detergent, ie - no laundry or dishwasher detergents).

2) Aggregates such as cinder and crushed blue rock/basalt here tend to absorb a great deal of the water within the mix and the rough surfaces of the aggregates tend to make the mixes less workable. So, it’s a good idea to find out how much water per lb of your aggregate is absorbed into the aggregate and compensate by preparing a hydrated aggregate prior to mixing the otherwise normal desired strength/recipe proportions.

Edit to add - If you're on catchment make sure the water you're using in the mix is 1ppm or less in clorine content and check that the PH etc is in the nuetral range. Unbalanced water levels can lead to poor preformance of your concrete recipe. IE - weak concrete and even abnormal curing properties. Salt can also damage the recipe (beach sands).
E ho'a'o no i pau kuhihewa.

[Rob Tucker]

I think you car order bagged Perlite from Honsador. They store it Kona side and truck things over daily.

[janeadams]

Perlite -- Nursery Things carries bagged perlite (Pahrock).

UAP -- carries a different brand that's harder. Usually 2 or 3 sizes. We use #3 from Nursery Things in our potting media.

Jane
White Cloud Nursery

[DanielP]

BEI?