Monday, April 16, 2007

Concrete is always exciting

Four years ago, we did a little project on this farm that required some concrete. To make a long story short, on that project, a concrete truck went "wheels up" with 10 yards of concrete in the drum and yes, the concrete set-up in the drum before we could get the truck upright. We've poured cubic 300 yards since then, but still, every time we pour concrete, my adrenalin gets pumping. I've noticed the same thing happens with seasoned concrete people too. Concrete has a way of making people nervous.

Last fall, the dirt road to the house site became too muddy before we could pour the slab for our fireplace. Given my previous luck with concrete trucks, I decided not to press my luck. We boxed in the house, added (most of) a roof, and waited for better weather. A few days ago, I declared the road "almost passable" and decided it was time to finally pour that slab in the middle of our great room. The forms had been ready for weeks - there were just a few knick-knacks to take care of... some rebar to secure... and a road to smooth out... so I ordered 4 yards of concrete for 12:30 pm. One of my bro-in-laws hopped on the backhoe and started hauling "crick rock" to some of the rough spots in our road. I followed behind him on the dozer and graded the road smooth. My other bro-in-law removed some rigid insulation from our house so the truck could shoot concrete through the hole in the wall when it arrived.

By 11:30, the road looked fine, so one of my b-i-l's jumped in his truck and headed home to get the concrete tools and some food. At 11:57 I looked at the clock in my truck and thought about going to grab some food too before the concrete truck arrived. But then I looked down the hill to the main road (half a mile away and 300 feet down from the house site). Was that our concrete truck coming up the road? half an hour early? Impossible - they're never early. Just then the truck turned off the main road and came across an abandoned road through one of our fields, headed straight for the creek. The driver had been to our site almost 18 months ago... before we had a bridge, and had just assumed that we were still driving through the creek. Not so! In fact, I wasn't even sure one of my tractors could go through that creek location after the spring gully washer we had received recently. Panicked, I jumped in my truck and raced down our hill to try and re-route the driver before he attempted to cross the creek. By the time I got to the creek, the driver had already drove through it and was grinning. "You crazy son-of-a-gun!" I yelled - "we have a bridge - you didn't have to go through the creek." "Awwwwl, that's the funnest part!" he said.

My b-i-l showed up with the concrete tools just as we were ready to pour the first concrete into the forms. At that point I realized that I had absent-mindedly left the concrete vibrator on the other end of the farm. So, off the hill I drove once more - knowingly violating what I think is one of the most important rules of concrete - "never leave the pour!" "Don't let your brother add too much water... please," was my last request before I ran for the concrete vibrator.

By the time I got back, half of the forms were full, the slump looked fine, the forms weren't leaking into the basement, and everything was under control. In fact, by 12:30 (when the truck was scheduled to arrive), we were done with the fireplace slab and had finished pouring the leftover concrete into the cores of some cinderblocks (these cinderblocks form the below-grade stone ledge around my basement.)

Minutia and technical stuff for the DIY folks:

In picture #2:

*the blue conduit is for electrical service to the mantle. A few weeks ago my cousin reminded me not to forget the wires to the mantle before I started building my fireplace. She said she has to run an extension cord up the front of ther fireplace to her christmas lights.

*the white painted doo-hickies are ends of oak timbers. Rather than frame my sill timbers around the fireplace structure, I got lazy and poured the dovetailed timbers into the fireplace slab. I pity the folks that try to replace these timbers in a few hundred years. The white paint is to keep the water in the concrete from wicking into the timbers as it cures. This slab is 9 feet above the basement slab - I don't think water will wick up 9 feet from the basement and rot these white oak timbers. If it does, I might be the fool I pitied in the previous sentence. :)

*the trapezoidal 2x4 structure in the form work is a form itself. It allowed us to recess the slab 1.5" into the main slab. This is so the firebrick in my hearth will be at eactly the same level as my finished floor. My original idea was to block out this space with something that would displace the concrete. My b-i-l knew better though. The problem with using a solid form to block out something like this is that it's darn near impossbile to evacuate all of the air bubbles from beneath a horizontal concrete form. I wanted a smooth level surface to lay my firebricks on, so we went with his idea. About an hour after pouring the concrete, it was firm enough that we could scoop out 1.5" of concrete from inside of the trapeziodal forms.

* in the middle of the trapezoidal 2x4's is a foam block out that will be removed after the concrete cures. It is the size of a single 4.5x9" firebrick. This opening can function as a fresh-air make-up to the fireplace, and as an ash dump. The 2x4 across the top of this foam block out is to keep it from floating while the concrete is wet.

* there is another foam blockout to the left of the trapezoid. it is for a flue that will allow me to put a furnace or hot-water heater in the basement and vent it through the chimney - if I should ever decide to do so.

*water bottles on the rebar are to keep us from accidentally cutting ourselves. (whoops, some were removed when I took these pictures!) That stuff is very sharp after being cut with an abrasive chop saw. A person would be well advised to cover vertical ends of rebar with something even more substantial.


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