03-15-2021, 06:26 PM
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.
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.