Often the best laid plans get a little “mixed up”….
This week I started with a “new” group teaching the module “Footings and Walls” which, in brief, is a module that concentrates on the wooden formwork necessary to make concrete structures.
Usually, I start in the classroom and we explore the nature of the concrete that is going to be placed in the forms and its make up and the correct methods to put it into the forms. Normally, I would get the students to mix a little bit of concrete from scratch and put it into a little form not much larger than a box, knowing that it will probably be discarded at some point.
However, with this amazing weather that we have be having, and with a specific need for some concrete entryways at the people doors of our new building, I thought that I would take the students right out into the yard and make some forms, mix some concrete and place it into the forms. In this way we could have a hands on lesson and I could turn this little project into a “teachable moment”.
First, there was some excavation…..many hands make light work, so we divided the class into two teams and got at it. We created the forms, place insulation in the bottom of the holes, and created rebar armatures for the tensile strength required:
Then it was time to mix (mix it up!!!!) the concrete according to the mix requirements and to place it in batches into the form:
As you can imagine, there was going to be a lot of mixing and placing!
All of this took some time, especially as we were experiencing the active learning of water/cement ratio, segregation, consolidation, concrete mix (cement powder, aggregates, potable water in the correct and consistent proportions), slump….and of course, the fact that once started, we could not break for lunch until the two “slabs on grade” were finished.
Once the forms were filled, we screeded the top, jointed the edges, polished and broomed the finished the surface.
Then we had to clean up, level the work areas and cover the surface for the weekend to prevent evaporation.
Concepts we discovered in a tactile way included the use of additives (in this case, cement glue), bleed water, hydration, setting, curing, strength in MPA and in PSI, rebar tying and placement, coverage, compressive vs tensile strength, curing and setting.
We also discovered concepts like slab on grade, structural slabs, shoring and re-shoring, water retention, green concrete, temperature placement, the fragility of “liquid” concrete, Portland cement, rebar sizing in metric and imperial systems, rebar cutting, bending and placement….and much much more!
Every one of these words represent the most essential vocabulary of the so-called “theory” of concrete……all of which we normally would have “discovered” in the classroom. (If there is any confusion about this vocabulary, let’s discuss it tomorrow!)
Don’t you just love the classroom when it is not in the building?
That’s what I call a concrete learning experience 😉
Tomorrow, we are going to mix it up in a different way…see you then!