Week 5

We’ve made tremendous progress this past week. Thanks to Abby, we finally found a way to get our blocks to release smoothly from the mold by lining them with a thin layer of plexiglass. While this works really well, we decided to break down and buy premade concrete blocks so that we’d have more time to work on the more important stuff. However, we made a new custom mold with the plexiglass lining to make the smaller uniquely sized blocks we need for around the door and the window.

Our premade concrete blocks arrived last Monday, and already we are laying the final course of our structure. All of our smaller custom blocks have been cast and should be dry enough to use tomorrow. With the walls almost complete, all we really need to do is decide on how we want to attach our roof before we can start taking observations and measurements to compare to future models. 

At this point, we hope that each person will be able to develop their own idea that they can take the lead on in implementing into our existing structure or future structures, whether this be a new variation on the standard block or some other innovative component to incorporate into the walls, roof, window, or door. This is where all our early research will really help. We are having our weekly faculty dinner tonight to discuss our progress and where we would like to go next.

Week 4

With two new block molds ready to go, we started the week with high hopes. Because we’re constructing a fairly small building, we’ve decided to build two new molds at 75% the size of the original. We figured this would allow us to produce more blocks in less time, and at a more manageable size. After making some initial alterations to the new molds on Monday, we started laying our new blocks on Tuesday. Unfortunately we’ve since had a few setbacks since. While we’ve gotten pretty good at mixing the concrete, filling the molds, and flipping them, we’ve been having a lot of trouble with the release. The corners and insides of the blocks are not coming out cleanly.

After altering our mix ratios and varying how much we packed the molds and having little success, we decided to look into ways to facilitate the release of the concrete mix from the wood mold. The bad news is we still haven’t found the perfect solution. The good news is it has forced us to be pretty creative. So far we’ve tried spraying the mold with cooking spray, lining it with recycled plastic bags, brushing it with vegetable oil, and lining it with heavy duty aluminum foil. We may try vaseline, but based on the results using other oils, we are not too hopeful for this approach either. We would like to have a metal mold like they use in Senegal, but unfortunately these are not for sale and would take too much valuable time to make for just the control building. We are having a planning meeting tonight with our advisers to develop our next strategy.

On a more positive note, all of our group members are now woodshop and 3D printer certified as of this week. We have also had some downtime to start drawing and making small scale models for future projects to begin once the control building is built, like a miniature sandbag mock-up out of sand, balloons, and glue. Although we don’t have a ton to show from our work this week, we’ve definitely learned a lot and remain optimistic.

Check out Lehigh’s website for an article by Kelly Hochbein about our project! http://www1.lehigh.edu/news/better-buildings-senegal

Week 3

There was plenty to do this week! With all of our materials here and plenty of sun, we were able to start the heavy lifting. We spent the beginning of the week mixing concrete with different cement to sand to water ratios and then tested all of these ratios in smaller molds, so not to waste too much material. While ideally we would like to use as little cement and water as possible to make it most realistic for the Senegalese, we kept finding that the concrete blocks with lower ratios were not holding up well enough. Ultimately, we decided that we will use the same cement to sand ratio as they would in Senegal (about one to three), but we will be using slightly more water since the sand we are using is a little different. Since we are not specifically looking to change the materials of the blocks right now, we decided it is okay to alter the block composition to fit our needs even though it is not entirely accurate. We are still getting an authentic Senegalese experience by mixing all the materials by hand and laying the blocks in the hot mountaintop sun!
Once we had a rough idea of what ratios worked best, we started mixing larger quantities to fill our actual block mold. It took some trial and error trying to determine the best ways to pack and flip our blocks, but we now have some pretty good samples! After all of our experimentation, we are now looking into how we can alter our mold to make the process run more smoothly. We’re on the right track! We will continue making blocks and hopefully be able to start constructing something next week.

Week 2

We have received permission to start building and have marked off our designated site! We received a few bags of cement, lime and sand today as well as other necessary building supplies.  As soon as the rest of the materials arrive early next week, we will begin making blocks and constructing our model home. In the meantime, we have been researching possible directions we would like to explore once our control model is built. To maximize productivity, we split into two groups to look at different components.

One group has done comprehensive research on ventilation, looking into several ways they can modify the existing techniques to allow for more airflow. This is a vital and often lacking component to homes in Senegal, but poses a lot of potential issues. The goal is to create air circulation while preventing heat, bugs, and sand from entering the homes with the fresh air. Our first idea is to create all of the walls out of CMU, with a bottom row made of brise soleil blocks. We want to incorporate a type of screen mechanism in the brise soleil openings to prevent the entry of mosquitoes. The top of the building will have a row completely open brise soleil. There will be a barrier below that row which acts as a ventilation barrier and bug screen between the living space and the top of the house.  The top brise soleil blocks will be where most of the sunlight enters the house for visibility.

The big question of the week was Why do homes in Senegal not have screens when disease carrying mosquitoes are such a big issue? We came up with a few reasons, such as screens make the homes appear unwelcoming, they can easily damage in weather, or they are simply not cheap for people in Senegal to buy. We tried to experiment with different ways we could hide a mesh screen into a brise soleil block so it is not visible. Next week we want to explore different textiles people could use instead of metal to make it cheaper and easier to obtain for senegalese people. The 3D printing sustainable development group wants to work with us in the future and we are hoping to find a way we could 3D print screens with plastic made from recycled plastic bags.

We also experimented with different ventilation systems such as thermal chimneys and wind scoops. Thermal chimneys have a metal material on the top which attracts heat.  Below there is a corridor that allows air to rise and then funnel out of the building, circulating cooler air up through the house. The same concept can be applied to the south facing fall of a building. Heat is attracted to the metal wall and then a corridor helps funnel hot air up and out of the building. The corrugated metal roof is beneficial to these types of systems, instead of heating up the building to extreme temperatures like they are currently doing in Senegal.  Wind scoops can be used in multiple sides of the dwelling to help direct incoming winds through the space.

The other group continued researching earthbag construction and brainstormed how we could expand upon existing techniques being used in similar areas. A square or rectangular home constructed out of sandbags would look very similar to the existing concrete homes in Senegal once they had been covered in cement. The problem is that a rectangular structure typically needs wood frames distributed among the sandbags. Since wood is not widely available in Senegal, dome shaped structures would probably be a more viable solution. While these may provide different aesthetics, they also open up other opportunities for building.  

Since the dome shape tapers up to the top, one idea we had was to build a screen or some kind of low emissivity barrier into the sand bag layers towards the top and then leave the very top open. This way air would enter through the door and windows then the hot air would rise to the top and exit the building through the top. The screen would prevent bugs from coming in and then some kind of slightly elevated, removable or permanent cap could go on top to prevent rain and direct sunlight from entering. We could also easily incorporate a rain collecting device by adding a slanted ledge near the bottom of the dome that would collect the rain and siphon it into one area to be collected.

Another idea we looked into was incorporating sandbag homes into the traditional Senegalese compound and courtyard. One way this could be done is by creating one large, torus shaped building that housed a courtyard in the middle. Some things to consider are the fact that this type of building would probably require a separate roof and the shape of the building would not really allow for additional buildings to be added on to the compound as they typically are in Senegal. We also considered building lots of small domes and bridging them together as they get added on. This would allow for small corridors that could be treated as communal space and would also allow for an outdoor courtyard to develop naturally as it does with the current building techniques.

Ideally we would like to be able to construct two additional smaller scale models to test some of these ideas once our initial building is complete. Then we can compare them to see what is the most efficient building.