“It’s a dangerous business going out your door. You step onto the road and if you don’t keep your feet there’s no knowing where you might be swept off to.”-Bilbo Baggins. The concrete business is a dangerous business…I hope I’m being swept in the right direction.
I met the building inspector Thursday afternoon at 2:15. I had to leave work early but this was the latest appointment I could get with him. It wasn’t too bad work wise because we had gotten rained out around 10:00AM so I really didn’t have to be there for anything special. I got up to the site around 2 and had a bunch of things I needed to finish for the pour anyway so I got set up while I was waiting for the inspector.
The inspector arrived promptly at 2:15 and proceeded to walk to the edge of the site. He turned and looks at me and says, “It looks like you know what you’re doing, pour away.” That was music to my ears. The final step before pouring is in place.I also asked him about the under slab plumbing. Did it really need to be cast iron pipe under the slab? He said no and that I must have gotten an old checklist from the building department. More music to my ears. That would have been such a pain to take on a cast iron job. At least for me it would have been. If you make a mistake with PVC you just cut it out and reglue a new piece on.
Once the building inspector left I really got into it. I started finishing off the little things I needed to do before this Saturday’s pour.I called the concrete plant and set up concrete for 8AM Saturday and called the pump company and set them up for 7:30. It takes about a half hour to prep the pump before concrete arrives.
One of the things that I really wanted to do was lock up this area where there is a step in the footing. I used #9 wire at the top of the footing and through the footing about 9 inches off the bottom. I put 3X4 stongbacks on either side of the forms and wrapped these with the #9wire. Once this is done you take your handy dandy lineman pliers and twist the #9 wire to tighten it up. Here’s a picture.
The other thing I did Tuesday after work was pin the rock where it’s exposed to the footing. I didn’t have my camera that day but basically what you do is take a Hilti drill with a 3/4 inch bit on it and drill 8 inches into the rock. Once the hole is drilled you take a vacuum blower and blow any dust that is in the hole out. I brought a tube of Hilti HY150 epoxy with me from work and using the dispenser for it you squirt the epoxy into the drilled hole and insert a #5 bar. On a warm day the stuff sets up in less than a half hour. (You can use non-shrink grout in lieu of epoxy.The epoxy is a snap though) It was raining when I did this so I just did one hole at a time. I also epoxied some 1/2 inch coil rod in place as well. I used the coil rod to help brace a couple of the forms for safety reasons.Here’s a picture.
By the end of the evening on Thursday I was pretty much ready for a Saturday pour. I had about two hours of work left to finish things up which I was planning to do Friday night or early on Saturday.
Then something happened on Friday that was most unexpected…and also quite unusual. We lost power to the placeing boom at work while we were pouring.This is a placing boom.
We actually lost power to the placing boom right before we started to prepour the columns on this job. As soon as I heard that I called the plant and told them to stop shipping concrete until they hear back from me. That part was fine. They had only shipped the grout truck that’s used to prime the pump and two ten yarders of 5950 psi concrete aka 5950 (pronounced fiftyninefifty in the business if you want to sound like you know what your talking about.) The electrician foreman Tony was working on it already so that was great and Johnny aka Johnnie Chiz, aka Chisel,aka Super Chiz was with him monitoring the situation. There was an electrical connection on the 15th floor that had gotten “fried” because water had run down into the fitting during the rain storm the day before. There was a slightly heated discussion about whose fault it was for not leaving a rain loop in the line but we were able to get past that. It took about twenty minutes to fix it and we were back in business and started to pump the concrete up the building. I called the plant back and released the balance of the concrete for the day which was only seventy yards. I also reminded them to put retarder in the last truck because it takes a while to clean out the line once you’re done pouring.( Retarder in a concrete mix slows the set time of the concrete once it is mixed. We use this in the summer all the time.)
Placing Boom 101:
For the uninitiated the concrete goes into a hopper in the street and gets pumped into a 5 inch riser pipe that goes straight up the building into the placing boom turret and into the placing boom itself. When you finish pouring you put a round sponge into the tip of the placing boom and blow it back down the riser pipe with compressed air into a box in the street. This cleans out the pipe for the next pour and you wind up with a box full of concrete that gets thrown out the next day.
What happens to the placing boom if the concrete starts to get hard? That’s when trouble really begins.
And things cease to be fun.
This is the short version: We lost power to the pump when we were almost done pouring 60 yards. The electrician was on it right away. He was on the deck. I met him on the 13th floor.”I found the problem and it will be fixed in ten minutes.” OK. You should have power. We still don’t have power. ..Let me try something else. It’ll take 5 minutes. I call Johnny Boo and tell him we have to get ready to move fast if this doesn’t work because the concrete is going to start to set up in the line.The next thing Tony the electrician tried didn’t work either. The placing boom can’t move we are totally screwed now. I waited too long to make a move. So much went on in the next half an hour I could write a book on it. (I keep forgetting that this is the short version.) When we went to blow back the line they couldn’t switch the diverter valve over.( The diverter valve is used for the blowback so the concrete goes into the box I mentioned before.) I broke open the line in the street before the diverter valve and the concrete started to come out of the line like 5 inch diameter sausages two to three feet long.(It really did look like sausage albeit concrete sausage) The concrete really started to pile up. I thought we were going to be a able to clear the line. At that moment I thought we were going to be fine.
Why didn’t the sponge ball come through at the bottom? Because the concrete in the boom never moved. The concrete that I had gotten in the street was all from the 22 stories of concrete in the riser pipe(It was a lot of concrete). Gravity had forced it all down the line. The last position of the boom was completly horizontal. The worst possible position. We lost the boom. We were doomed. I couldn’t believe it. We were done, finished, game over. What a mess. I called and cancelled the footing pour for the Hobbit House for Saturday. To say I was upset is an understatement…so were my wife and kids.
Saturday was spent taking the boom down to the street replacing all the lines and then reinstalling the boom. It took six hours. There were a couple of gliches during the day but we got it to work and everything seems to be OK. Here are some pictures.
Well, we are ready to rock and roll for next weekend. Hopefully the weather will cooperate! (And my day job will go a little more smoothly!) Enjoy your week!