Footings, Day 3, First Concrete

Today was day 3 of the footings… Our first day pouring concrete on the site.  The actual work was really all done in about 2 hours, half an hour if you just count the concrete pour time, so it is hard to call it a day.  The inspector, Dale, needs to check the footings before the pour and his MWF 10 to noon schedule meant we couldn’t fit this into Monday afternoon like the footings guys wanted.

Here is today’s timelapse video;

Thunderstorms were predicted for 1:00, so I called the building inspector to see if he could put me early on his rounds.  He agreed and put me first.  I texted Doug Dysert by 8:30 and hoped that would be enough lead time to move the pour earlier…

The inspector arrived just after 10 AM.  Keep in mind, this was my first inspection, so I was a little bit nervous.  The first thing he did was check out my posted permits.  Then he went down into the excavation and gave the forms a good look.  The inspector was actually very friendly and said the design was a “work of art” and the execution was “very well done”.  He found a couple spots where the rebar was a bit too close to the boards (there is supposed to be at least 2” between the rebar and the forms) and told me to sort that out before the pour.   We chatted a bit and then he handed me my “Inspection Notice”, with “approved” written on it.  He left by 10:15.

I texted Doug to say we were all ready for concrete, but it turned out that the concrete was scheduled to come at noon anyway.  Two of Doug’s guys (Don and Chris from the previous day) arrived at about 11:45.  The concrete mixers (two of them) and the pump truck all arrived around noon. It was pretty awesome to see the pump truck extend its huge feet and then unfold its 135 ft arm.  I wish the timelapse camera had been angled to catch it.

The concrete pump truck was pretty huge.  Its 400 horsepower Cummins diesel motor powers 4 powerful pumps that push the concrete at 4800 psi.  The operator told me that he could pump up to 210 yards per hour, but he had it set on the slowest possible setting for my small job. I got my order slip from the driver to confirm that it was 2500 PSI concrete with a slump of 5 inches.  It had the ¾ inch natural stone aggregate (6A) along with sand and fly ash.

Fly ash is what Charles Dickens would have seen coming out of the smoke stacks of dirty coal factories before they started capturing it.   Trapping that pollutant it in concrete is a good thing.  It is also pretty much free (waste product) and replaces some of the Portland cement, which has high embodied energy (and cost).  Its tiny particle size increases workability (think tiny ball bearings) of the concrete, so the water content can be reduced, which increases strength and durability… It is really a win-win additive.

 

Then the clouds parted and the sun came out.  The concrete got pumping and things went pretty fast after that.  They pumped out most of the 23 cubic yards of concrete in about half an hour.  I don’t think the crew had enough people to keep up like they would have preferred.  I jumped in to help with the screeding.  Even the pump truck operator helped moved the concrete pipe around when he got tired of waiting.  The concrete was pretty thick with ¾ inch stones.  None of the footings blew out, but it did bulge in a couple spots, which used up more concrete than we were expecting…

For footings, they just screed, they don’t trowel or float.  Since the tops of the forms were already level, screeding was just a simple process of “sawing” a board back and forth over the top of the form to level it out.

 

We ended up needing to use the concrete that was in the bottom half of the long pipe to fill in the last bit of the forms.  The pump driver basically dumped it on the sand at the top end of the driveway and we had to bucket it over and down to the footing.  Don was using a 5 gallon bucket and I was using a 2 gallon bucket (only other bucket available), but I joked that at least I was filling mine up all the way.

With the last bit of concrete, I built myself a 5 gallon bucket rocket stove.  I made the inner form out of cardboard (the night before) and wrapped rope and saran wrap around it to “spiral” the flow.  My hope is that it will make a little flame tornado that will push even more heat into the concrete and increase the draft further.  I’ll make a separate post on that if it works. This concrete wasn’t exactly designed for high heat so it may not last long.

Then the rain came down again.  It was actually a line of storms, hundreds of miles long, all lined up to pass over my site, and nowhere else. They guys thought it would blow over soon and decided to wait it out in the truck.  I got in with them and asked how long we would be able to push the vertical rebar dowels into the concrete.  They told me not to worry about it, we had “hours”…

Well, nearly an hour later, and the township tax assessor called and asked me to drop off a copy of the plans.  The assessor had been out to view the site while we were not there and was totally confused by my footing.  She was only about 2 miles away, and I wasn’t doing anything right then, so I took the plans over to her.  I hope she devalues the home as much as my bank’s appraiser does.  Unfortunately, she seems to like it.

When I got back, Doug was on the phone.  Understandably, He didn’t want his guys to sit there waiting any more.  He said they could just drill the rebar in later (for ~60$/hr).  As I hung up with him, the rain stopped.  We went down to check out the concrete and found it was already too stiff to hammer the rebar into anyway.  It wasn’t my plan, but now I will have more time to carefully mark the position of the dowels, so it may be for the best.

Not sure if it was just the dollars talking, but Doug really didn’t like idea of the PVC tubes as rebar receptacles.  He pointed out that they would be a weak point in the connection between the footings and the rebar.  They do not have the strength or the grip.  I was more interested in the convenience because I don’t think I need strength or grip in that location.  Perhaps we were thinking about different locations.  I agree drilled rebar will be critical for the pillars under the concrete ribs.  Not sure if we will use the PVC when we get to the main footings, but I have 250 of these things cut and ready to go.

 

The rain washed off the concrete “crème” and left an exposed aggregate look.  I kind of like it and I think the shotcrete will stick to it well.  Another “day” done.

I still haven’t seen the bill (or paid anything).  In order to get a reasonable bid on this unusually complicated project, I had to get the bid based on “volume and materials”.  I thought that was safer than “time and materials” because at least the volumes were calculated beforehand.  Basically, I agreed on the cost per cubic yard for forming and pouring as well as the cost, per ton of rebar, for placing and tying the rebar.  But I do not yet know what he will charge for the materials (such as the wood, rebar, and concrete) or the total cost of the pump truck, or how the over-orders of material will affect the bill.  I am a tiny bit nervous about that.