Slab pour
Earlier in the week, I had scheduled the cement delivery for Saturday, August 28. I ordered 20 yards of 3,000 PSI , which would equate to 2 trucks full. I calculated 19.3 yards, and was hoping that 20yds. would be enough. Additives- fibers and Super-P would also be put into the mix. The fibers would help resist cracking. Super-P, (plasticizer) would make the cement easier to work with by making it more fluid. The chemical has a short effective time, (about 40 minutes) before the cement goes back to the thickness or viscosity that it was before the Super-P was added.
The strength of cement depends on the water to portland ratio, the more water, the weaker the cement. Super-P allows the cement to flow like it has more water in it, but does not affect the strength. The consistency of cement is measured by a slump test using a 12" cone. Like a snow cone, it is filled with cement and then inverted. When the mold is removed, the cement will slump down. The amount of this slump is measured from the top down. A very stiff mix will have a slump of 2 or 3. A very soupy, or loose mix will have a slump of 8 or 9.
When the truck arrived, the driver added water to make the cement a 3 to 4 slump and added the Super-P which then brought the slump to a 7. We used 2 rented chutes to transport the mix to the far end of the smaller workshop slab.
We paused for a short time to float the first half and in so doing, allowed the Super-P to wear off. When we picked up and tried to get the cement to the far side of the garage slab, it wouldn’t flow in the chute. By this time, the second truck was waiting. We had to get the cement out of the first truck and get the next truck in. We found that the stiffer cement still left in the first batch would flow down a steeper chute, so we dropped it at the close end of the garage and raked it down to the tubing. This let us get the next truck in. This fresh batch would flow to the far side of the garage. This was successful and in 45 minutes, the truck was empty- 1 wheelbarrow of cement short.
We made the last batch by hand and filled it in.
The truck driver cleaned up and left. We were left alone to finish the floating of the slabs.
The work was cleaned up by 1:00pm and burgers and dogs were served for lunch.
The cement is then cured by keeping it wet for at least 1 week.
I bought 3 lawn sprinklers and propped them up on the slab. An electronic sprinkler timer turned on the water 6 times a day for a few minutes. To keep the water from running off quickly, I distributed 3 bails of hay on the slabs.
During the pour, samples from each truck were collected for later testing.
These 6"x12" cylinders are crushed in a testing machine and the pressure at failure is recorded. Tests are preformed after a time period. I chose a 7 and 30 day test. A testing company named Geo Tech Services was recommended. I gave the owner, Al Farruggia a call. He was very helpful. He could perform the 8 tests for around $100. I don’t know what I will do if the samples don’t pass the test. I’m not inclined to start chipping out the slabs.
As it turned out, the cement was poor. The first truck barely passed the 30 day test, and the second truck failed by a little. I am very disappointed with Weldon.
1 week later the framers started the demolition