Tuesday, February 17, 2009

How things change


It's the following week, we've properly observed the ancient presidents' birthdays, and most of us are back to work. Unfortunately, the economy's swift sword has cut me loose from the Hanley Wood team. However, the February issue of Concrete Construction has hit the street, and the Web, and links to Joe's project overview and Tim's synopsis of its long-term coverage in the magazine are posted in the righthand navigation column. Both are worth reading.

The third day

I was not on site on Thursday, the third day of concrete placement for this project. According to Joe's reports, all went well.

In his words, "We wondered how the 6B concrete would be and the first truck was a little low in slump. Jack [Gibbons] came to the site from the batch plant to see how the first loads would be so he was the one to adjust the first one. It was pretty clear that 6 oz of poly C was needed. Once that happened there was no trouble at all..."

"I went back Friday morning to mark out points for the D meter and talk with the guys doing the 3-D laser work. The 3rd day pour looked good; couldn't see a single hair sticking up in the 6B area. Jerry [Holland] said it should be that way."

Friday, February 13, 2009

Day 2

It makes a big difference when you have a relatively steady supply of concrete. Even though Wednesday's 20,000-square-foot placement involved four different mixes, it went a good bit more smoothly than the first day. All the concrete was down by 3:30 and the power trowels were doing their best to finish it off.

Meanwhile the testing firm made several runs with the D Meter, provided by the Allen Face Companies. The device is similar to a Dipstick, but uses a somewhat different measuring protocol. The readings from the first section, bounded by column lines C/D and 3/4, gave an FF of 46.4 and an FL of 29.1.

Another crew also came in and scanned the previous day's slab, using a Trimble laser scanner. In addition to comparing this information with future scans, the plan is to share the collected data with the ACI 117 Tolerances committee as an example of real-world slab-on-grade placement.

Again it was clear that the vapor barrier, although puncture resistant, takes a beating as ready-mix back over it to deliver the early loads, especially as they turn their wheels to navigate around the tube steel columns. And how the crew deals with folds and other deformations is most interesting. Enough on that for now.

While the weather on Tuesday, the first day, was clear, sunny and breezy with near-record high temperatures in the 60-degree range, Wednesday brought dropping temperatures and it rained throughout the day - good concrete weather when you're inside a warehouse with the doors only partially open.

Thursday should be interesting, as it will include the stiffest, most high-fiber mixes. They tried placing one trial load of it this afternoon by one set loading docks. The way it hung in the rebar graphically demonstrated the effect of the fiber. Thursday should be interesting.

Tuesday, February 10, 2009

Two (plus) down

The first two 10,000-square-foot test sections are in place. The first used a heavy dosage of fibers (7-1/2 pounds per cubic yard of concrete) and 3/4-inch aggregate. The second included just 1-1/2 pounds of fiber per cubic yard and a top size aggregate of 1-1/2 inches in a more well-graded mix.

A small section also was placed with seven different surface finishes. This is the area where CTL's Howard Kanare will be monitoring moisture movement.

Today's other highlights? Two RFID-based maturity meters were put in place and will enable the testing firm to wirelessly obtain the logged data. No wires - just point and shoot, sort of. One is entirely embedded. The other consists of a probe embedded in the concrete and a lead that connects to the RFID device temporarily taped to one of the steel columns. When the second one's task is completed, only the probe will be left in the concrete rather than the entire RFID device.

Also, the crew got to try out Allen Engineering's new HDX 740 power trowel, which features 5-foot-diameter blades and joystick controls. They seemed to like it.


Tomorrow (Wednesday) should be an interesting day. The crew will be placing 4 different mixes in 5000-square-foot increments. (They put the vapor barrier down this afternoon.) Meanwhile, the testing firm will measure slab flatness (FF and FL) on the Tuesday pour, which also will be the object of a laser scan. Both of these data sets will be used to help evaluate slab shrinkage and curling over the next two years. More information will be posted here as we proceed.

Monday, February 9, 2009

Monday's final preparations

After a morning glued to the telephone, Joe went to the site this afternoon to finalize plans for this highly collaborative project. The various parties involved are showing an amazing amount of cooperation and tolerance.

The vapor barrier was to have been placed today, and I haven't heard anything to the contrary. As always, no news is good news. But in these final moments before the concrete is batched, there are seemingly endless decisions and details to attend to, as well as some concessions to be made. It is no small feat to get everyone on any project to cooperate. But here we're working with a group of leading authorities in the concrete industry, from all across the country, and all of them want it to turn out just right. And getting consensus decisions in that environment requires significant diplomacy.

I've worked under enough different bosses over the years - with management styles ranging from cool and calm to screaming maniac (you know who you are) - to appreciate Joe's negotiating skill and the calming influence he brings to the group. From all reports, things are about as ready as they could be, given all the variables in this project. For you who have yet to learn the details, trust me and be patient. We'll soon be laying them out. And of course, it will be a lot easier to accurately report once the concrete has actually been placed.

Sunday, February 8, 2009

Pre-pour notes

The Warehouse Floor Field Test being coordinated by Concrete Construction's senior editor Joe Nasvik is slated for construction this week. The 60,000-square foot slab on grade is going into a warehouse in Barlett, Ill., which has been enclosed and heated since the beginning of this year or so. Right now the schedule calls for final preparations to be made on Monday (Feb. 9) and concrete placement over the course of the following three days. More information (including photos) will follow here as the job progresses.

Joe's short article describing the project and what we expect to learn is in the February 2009 issue of Concrete Construction. We'll post a link here as soon as it's available. [Note: See links above right.]

Please feel free to comment at any time.