Notes from Windward: #58

Working on the dining hall

Part II

Preparing buckets of sand and rock
The first task to attend to when we're getting ready to mix is to fill up buckets of sand and rock. Once we start mixing, we want to keep the concrete coming as best we can, so we try to do as much ahead of time as is practical. Now that the backhoe is up and running, we're able to dispense with having to have rock and sand delivered to the work site. Instead, we now have big cribs where we have the material delivered in 10 cubic yard quantities. Then, as needed, we use the front bucket on the backhoe to bring amounts of sand and rock to the actual worksite. This is gaining us the twin benefits of less waste and more convenient placement.

Working off the back of the truck goes faster
When you're dealing with things as heavy as a five gallon bucket of rocks, convenience is a real issue. One of the little tricks we've worked out is to use the pickup's tailgate as an interim platform. Just lifting the bucket of rocks to chest high is stressful enough without having to shift it so that you can then pour the contents into the rotating cement mixer. The easier way is for two of us to lift the buckets onto the tailgate, and from there it's a lot easier to move it laterally to the mixer and dump it in. That may not sound like a big deal, but when you're doing a twenty mix run, each little bit helps.

Bob putting together another mix
When we mix concrete, we use what's called a "1-2-3 mix." That is, one part portland cement, two parts sand and three parts crushed rock. In actual practice, we add almost five gallons of rock to the mixer, followed by three gallons of sand. After that's mixed for a couple of minutes, we add a gallon and a half of cement

Getting the amount of water right is perhaps the trickiest part of the job. Too little, and the cement is too hard to work (or sometimes to even get out of the mixer). If you add too much water, the mix is too "soupy" and won't set up as strong as it would otherwise. The goal is to coat all the particles with cement, and too much water tends to wash the cement off of and away from the sand and gravel it's supposed to stick together.

One mix coming down
After all the ingredients are in the mixer, and we've gotten the consistency right, it's time to make the transfer. If the mix is a little on the wet side, as we were running that day, sometimes it can splash a bit if you're the one handling the wheelbarrow. That's why Jerry has his head turned aside in the picture.

By now, we're able to steadily generate a mix every five minutes which comes to about one half cubic yard an hour. That's not going to outrun a cement delivery truck, but then again by mixing it ourselves, we don't have to pay the $100 delivery charge either. Our average pour comes to between a dozen and sixteen mixes.

With three people working together, it's not too demanding an effort, and if the project calls for it, we don't hesitate to do one run in the morning and another in the evening. When we're working with forms, we can only pour once a day since the concrete has to set upbefore we can strip and replace the forms. With other work, such as the concrete piers under Finney trailer, the twice-a-day mixing schedule works well.

Hauling a cubic foot at a time
While it's work to move the concrete around a foot at a time, it also means that we're able to do concrete work in tighter areas than would be possible if we were working right from the truck. Those monsters aren't very maneuverable, and since our construction is purposefully sited on the hilly portion of our property, the use of wheelbarrows offers a notable advantage. In commercial work, when access is a problem, the standard solution is to call in a pumper. This is a piece of equipment that accepts the concrete from the delivery truck, then pumps it up to 150 feet to the point where it's needed. That's really nifty, but it's also an additional $100, so we're back to using the trusty old wheelbarrow again.

On a long pour, Jerry and Walt hustle to keep up with Bob
When Bob's on a roll and it's a long run, the form crew has to take time out to refill buckets. It's important for the mixer to stay focused on the task, because otherwise it's easy to make a mistake. The strength of the final product is based on getting the proper portions mixed correctly, so it's up to the rest of the crew to keep the mixer stocked with materials. The most common mistake is forgetting to add the sand, something you don't notice until you dump the mix into the wheelbarrow. It's really tedious, let alone embarassing, to stop and shovel it back into the mixer and correct the mistake.

When the pour is going into the ground, as with a perimeter footing, or into the first course of the retaining wall, it's simply a matter of scraping the concrete out of the wheelbarrow and into the form. As the wall gets progressively higher, the task gets progressively more challenging.
Transferring the cement to the form
By the time we're working on the uppermost pass on the retaining wall, we're having to use buckets and stand on a ladder in order to get the concrete up and into the form. Still, it's such a pleasure to see another section of the wall reach completion that the inconvenience of the bucket brigade is soon forgotten. The crowning step on the final pass is to insert anchor bolts into the wet concrete. These will be used to bolt down a treated 2x8 to the top of the wall (code requires that any wood in contact with concrete be treated.) When it's time to put the roof joists into place, they'll rest on, and be nailed into, this topping sill.

With Jerry sparking the work on the dining hall, substantial progress was made during the month he was with us. It's no exaggeration to say that he got a project which was caught in the doldrums, over the hump. Not only was the entire perimeter foundation completed, most of the retaining wall was formed and poured. Even now while Jerry's up in central Washington helping a cousin harvest apples, the final pours on the west end are continuing. Unless something quite unexpected happens, we should have the retaining wall completed before the end of this season. Thanks, Jerry.

To view a drawing of the cement work, click Here

To view a drawing of the interior layout,
along with commentary on what goes where and why,
click Here

Index for Notes Issue # 58 ---- The Windward Home Page