The question of truck vs on site comes down to volume (cubic yards) and time (how long do you need to place it). Also, additional consideration, for columns, the wet concrete is gonna need to be lifted to the top of the columns, or pumped.
Take a 10" column, that's 8' high. That's 4.36 cu/ft, or .16 cu/yd of concrete per column. That's not much, at all. You only need to be sure to get each column done, from start to finish, in one go. You don't want to fill it halfway, let the concrete set, then fill it to the top.
I'd suggest buying aggregate (crushed rock and sand) from Puna Rock or Yamada's, and having it delivered on site. Then buy Portland cement from Hilo, and store it on site, OUT OF THE RAIN. Rent a cement mixer. Now mix the aggregate, cement, and water in the mixer, in batches. Take the wet concrete in buckets up a ladder and drop it into the forms. Figure you can lift 50lbs up a ladder per trip, that's about a dozen trips up the ladder per column. Not too bad.
Don't try this approach for big concrete work, it will kill you. But for 600ish pounds of concrete per column, done one at a time, totally doable for a owner builder. I'd guess with two people you could knock out a column per hour without breaking your back.
As for the formwork and rebar and all that, take your time setting all that up, and making sure they are plumb and level. I'd put 4 sticks of gatorbar in each column, spaced equally.
I'm sure some will say just put the columns directly on top of the lava, but then in a big earthquake there's not anything really holding the column to lateral movement. By having footings sunk into holes in the lava, and rebar tying the footings to the columns, it's much more likely to stay put when things start shifting.
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[quote pid='329402' dateline='1615832784']
I recently built a small 8' x 8' x 7' high blockhouse out of concrete blocks. I first poured a slab with steel rebar reinforcement and some #4 copper wire in it for a Ufer ground. I laid the block on top of the slab with rebar projecting up through the cells. Some of the vertical rebar was horizontal reinforcement in the slab that I bent vertical. It was a pain to get it all placed so it came up in the right places. I decided later to put in more vertical rebar so I drilled the slab in the appropriate places and epoxied in those pieces. The vertical rebar was not full height to start. I remember lifting many, many blocks over my head and easing them down into place over the rebar.
I would fill the cells about every 3 courses. I had a plastic ice scoop that held about a quart of concrete. Drop a few scoops in then settle the concrete by stabbing into it with a short length of rebar and by banging on the vertical rebar. I can not imagine carrying 50 lbs up at a time. I must have climbed that ladder hundreds of times.
You can mechanically join (extend) the rebar if you have the fittings but the most common method is just overlapping by 40 diameters. I was using 1/2" rebar so that means 20" overlap. I made sure that there was at least 20" rebar sticking out with 3 or 4 courses to go, built up the last courses without filling them, positioned the wood members along the top, then screwed "candy canes" of rebar to the wood with the appropriate length of rebar hanging down into the middles of the cells and the hooks at the top held in the right place against the wood by the screws, then topped off the cells in the block with concrete. When the concrete cured I finished off the wood work of the roof, sandwiching the hooked ends of the rebar between two pieces of 2 x 6 lumber with the bolts going through the hooks of rebar. You could probably lift the whole building by the wood parts of the roof. Where wood touched concrete I painted the wood with several coats of primer in lieu of the more traditional tar paper barrier.
It was a lot of work but I am very satisfied with the results. In large part I was following the FEMA plans for a concrete storm shelter. I would put one of them at each corner of your structure instead of columns. The engineering of the columns to not collapse in an earthquake is not a trivial task whereas the storm shelters as specified by FEMA are designed to stand up to a house falling on them. Plus, four storm shelters, amiright? One at least can be your mechanical room for pumps, etc. Another for electrical, then two more for unspecified storage. You will be glad for all of that in a real hurricane or earthquake.
Next time around I will probably do what it takes to build an oversized slab both in thickness and horizontal dimensions and have it poured professionally with a concrete truck. It is really great having a nice flat clean surface to work on. I may be alone in thinking this but having a thick layer of fill under the slab and a good strong slab to tie everything together at ground level would help a lot during an earthquake. In an earthquake the ground is moving. Let it move underneath the structure. If the fill acts like a bond breaker like flowering a cake pan then the house is subjected to less severe shaking.
Anyway I wish I had poured a larger, thicker slab and had someone skilled do it and not tried to mix so many bags of concrete by hand for the single largest continuous pour. Hand mixing was sort of necessary when building the walls due to the slow rate of progress.
Take a 10" column, that's 8' high. That's 4.36 cu/ft, or .16 cu/yd of concrete per column. That's not much, at all. You only need to be sure to get each column done, from start to finish, in one go. You don't want to fill it halfway, let the concrete set, then fill it to the top.
I'd suggest buying aggregate (crushed rock and sand) from Puna Rock or Yamada's, and having it delivered on site. Then buy Portland cement from Hilo, and store it on site, OUT OF THE RAIN. Rent a cement mixer. Now mix the aggregate, cement, and water in the mixer, in batches. Take the wet concrete in buckets up a ladder and drop it into the forms. Figure you can lift 50lbs up a ladder per trip, that's about a dozen trips up the ladder per column. Not too bad.
Don't try this approach for big concrete work, it will kill you. But for 600ish pounds of concrete per column, done one at a time, totally doable for a owner builder. I'd guess with two people you could knock out a column per hour without breaking your back.
As for the formwork and rebar and all that, take your time setting all that up, and making sure they are plumb and level. I'd put 4 sticks of gatorbar in each column, spaced equally.
I'm sure some will say just put the columns directly on top of the lava, but then in a big earthquake there's not anything really holding the column to lateral movement. By having footings sunk into holes in the lava, and rebar tying the footings to the columns, it's much more likely to stay put when things start shifting.
[/quote]
[quote pid='329402' dateline='1615832784']
I recently built a small 8' x 8' x 7' high blockhouse out of concrete blocks. I first poured a slab with steel rebar reinforcement and some #4 copper wire in it for a Ufer ground. I laid the block on top of the slab with rebar projecting up through the cells. Some of the vertical rebar was horizontal reinforcement in the slab that I bent vertical. It was a pain to get it all placed so it came up in the right places. I decided later to put in more vertical rebar so I drilled the slab in the appropriate places and epoxied in those pieces. The vertical rebar was not full height to start. I remember lifting many, many blocks over my head and easing them down into place over the rebar.
I would fill the cells about every 3 courses. I had a plastic ice scoop that held about a quart of concrete. Drop a few scoops in then settle the concrete by stabbing into it with a short length of rebar and by banging on the vertical rebar. I can not imagine carrying 50 lbs up at a time. I must have climbed that ladder hundreds of times.
You can mechanically join (extend) the rebar if you have the fittings but the most common method is just overlapping by 40 diameters. I was using 1/2" rebar so that means 20" overlap. I made sure that there was at least 20" rebar sticking out with 3 or 4 courses to go, built up the last courses without filling them, positioned the wood members along the top, then screwed "candy canes" of rebar to the wood with the appropriate length of rebar hanging down into the middles of the cells and the hooks at the top held in the right place against the wood by the screws, then topped off the cells in the block with concrete. When the concrete cured I finished off the wood work of the roof, sandwiching the hooked ends of the rebar between two pieces of 2 x 6 lumber with the bolts going through the hooks of rebar. You could probably lift the whole building by the wood parts of the roof. Where wood touched concrete I painted the wood with several coats of primer in lieu of the more traditional tar paper barrier.
It was a lot of work but I am very satisfied with the results. In large part I was following the FEMA plans for a concrete storm shelter. I would put one of them at each corner of your structure instead of columns. The engineering of the columns to not collapse in an earthquake is not a trivial task whereas the storm shelters as specified by FEMA are designed to stand up to a house falling on them. Plus, four storm shelters, amiright? One at least can be your mechanical room for pumps, etc. Another for electrical, then two more for unspecified storage. You will be glad for all of that in a real hurricane or earthquake.
Next time around I will probably do what it takes to build an oversized slab both in thickness and horizontal dimensions and have it poured professionally with a concrete truck. It is really great having a nice flat clean surface to work on. I may be alone in thinking this but having a thick layer of fill under the slab and a good strong slab to tie everything together at ground level would help a lot during an earthquake. In an earthquake the ground is moving. Let it move underneath the structure. If the fill acts like a bond breaker like flowering a cake pan then the house is subjected to less severe shaking.
Anyway I wish I had poured a larger, thicker slab and had someone skilled do it and not tried to mix so many bags of concrete by hand for the single largest continuous pour. Hand mixing was sort of necessary when building the walls due to the slow rate of progress.