#100 – July 25, 2019 – Replete With Concrete!

Dear Friends,

Half of the ISHA Maintenance Shed in Wisconsin now has a fantastic concrete floor! 
Putting a smooth, durable finish on concrete is a skill you can only master with the proper set of tools and lots of practice. We are fortunate to have several volunteers who are skilled in the art of pouring and finishing large concrete floors.
The first truck arrives, and the mighty volunteers have to move all the concrete to the back of the building with heavy wheelbarrows, one load at a time. Concrete is a blend of Portland cement, sand, aggregate (gravel) and water, that hardens when mixed. In general, the speed of the hardening process mostly depends on the temperature and humidity, so our workers had to move fast.
When there’s enough concrete on the floor, two other workers flatten, level, and smooth it with a straight 2×4 “screed board.” The board is pushed and pulled across the forms with a back-and-forth sawing motion. 
Screeding levels the concrete with the top of the forms, and begins to force the large gravel below the surface.
On a large floor, the next step is to smooth out irregularities and fill small holes left by the screeding. In the process, larger aggregate is forced down, leaving a slurry of cement and sand to fill the surface. For small areas, this is done with a trowel called a “darby.” On a large floor, it’s best done with a large “bull float,” as seen in this photo. Overworking the concrete will draw too much cement and fine sand to the top and create a weak surface, so experts will make no more than two passes with the float. 
After the concrete has partially solidified, the edges can be shaped and compacted, and the surface can be floated with a magnesium trowel (shown below) to remove the marks left by edging, and to bring the surface close to a final finish, which can be made with a steel trowel, if desired.
If all of this work is done properly, you end up with a gorgeous, smooth, hard garage floor!
And then you can move your supplies and tools back into that half of the building. The second half of the floor will be poured in mid-August by Ishwar’s cement sevadars and their mighty wheelbarrow helpers.
With warmest regards,
Paul Bauer
Chair of ISHA Building & Fund-Raising Committee