Proceedingsedge.rit.edu/edge/P16485/public/Detailed Design Documents... · Web viewJamiya Cook Mechanical Engineering Abstract The goal of this project was to design, build and test

Multidisciplinary Senior Design ConferenceKate Gleason College of Engineering

Rochester Institute of TechnologyRochester, New York 14623

Project Number: P16485

BIOCHAR CONCRETE ROOFING SHEETS FOR NICARAGUA

Cindy WidergrenIndustrial and Systems Engineering

Peter ChynowethMechanical Engineering

Adrian IzbickiMechanical Engineering

Jamiya CookMechanical Engineering

ABSTRACTThe goal of this project was to design, build and test low cost roofing made from concrete and biochar for

houses in Nicaragua. A partnership was formed with two organizations: the 4 Walls Project and the Ithaka Institute. Our first task was to research whether biochar, a charcoal like material made from many types of biomass, could be used for this application. We were further tasked with redesigning the roofs of the houses being built in Nicaragua by 4 Walls so that it eliminates their current roofing problems, can be produced locally, and best of all, is affordable. Another goal would be to create a process that could potentially start a small business in El Sauce. This way the roof would not only make it so 4 Walls could build more roofs, but also it could help employ the local people. The process involved research and experimentation into three subsystems for the roof: the shingle design, the concrete biochar mix design, and the molds for creating our shingles. Special attention was given to finding a useful biochar concrete mix since this is a new use for the material and there currently isn’t much research done on using biochar in concrete.

In the end, a final mix was decided on that utilized plastic bottle fibers, final molds were designed using a vacuum forming process, and the final shingle design involved the use of two styles of shingles. A prototype of the roof was built to test different properties of the design and to ensure it meets all of our customer’s requirements. All of the engineering requirements were satisfied and with a little refinement, the product of this project will improve the living conditions and quality of life for people in Nicaragua, and create a sustainable product that potentially improves the world’s carbon footprint.

BACKGROUNDIn El Sauce, Nicaragua, an organization called 4 Walls helps the local people by building homes for those

in need. They were looking for an updated design that would fix some of the problems with the current roof. Some of the problems include the roof uses imported materials, has large solar heat gain, is loud in the rain, and is not an ideal cost. If these problems could be fixed they would have not only improved living conditions for those in the homes, but also have the opportunity to build more roofs and to potentially create new local businesses to help employ the people in El Sauce.

When this project was proposed, another group, the Ithaka Institute, was interested. This group is a research foundation particularly interested in an innovative material called biochar. This material is a charcoal made from many types of biomass, which has many environmental benefits. Recently, this material has been identified as potentially bringing benefits to building construction but little research has been done. The Ithaka institute proposed that a roof made from a concrete mixture, containing biochar as an aggregate, could be the perfect solution for the roof.

Copyright © 2016 Rochester Institute of Technology

Proceedings of the Multidisciplinary Senior Design Conference Page 2

This project was designed to address the ideas and needs of both organizations. A new roof that would eliminate the problems seen in the current 4 Walls roof was the ultimate goal. Research into whether biochar could be used in this application and the benefits it would bring in the construction would be another objective. Ideally this research will help further knowledge of biochar, will present 4 Walls with an improved roof design, and would help the people of El Sauce by giving the opportunity for the formation of a new small business.

PROCESS

Design ProcessThis project required the design of three different subsystems: the concrete mix, the shingle design, and the

mold. All three had to be designed simultaneously in order to ensure they would work together for the overall system.

Concrete MixtureThe roof required a mix to be created that would involve the use of biochar, could support a person, would

be waterproof, be affordable, and not too heavy. The mix design involved mixing and testing concrete composed of different amounts of components in order to determine the optimal mix for our purposes. Table 1 shows the mixes that were created and later tested.

Table 1: Summary of mix components by volumeIn order to create the most effective concrete mix, it was found through research that vibrating your mix was a beneficial process. This method ensures your mix spreads evenly and that air bubbles are allowed to escape the mix. A vibrating table was built out of a tire, a sander and a piece of wood and can be seen in figure 1. This was used to vibrate each shingle poured. It was also learned that adding plastic fibers to concrete is a commonly used method to increase the tensile strength of the mix. Since Nicaragua has a problem with too many plastic bottles, a device was built that could turn plastic bottles into string that could be cut into plastic fibers. These fibers were added to our final mix.

Figure 1: Vibrating table Figure 2: plastic bottle shredder

Shingle DesignWe started with the initial design to make large slabs for the roofing tiles, almost emulating the current

metal roofing design. This can be seen in our ER, which had max dimensions of 3 feet and a max weight of 30 lbs. It was then decided that this would be too brittle and cumbersome. It was then thought to do many small rounded shingles, much like the terra cotta roof style. Then it was found out that making this geometry consistently would be extremely hard using concrete as a medium, because unlike clay, which is formable, the concrete would have to set and settles while drying instead of maintaining it shape without support. The next iteration involved making flat shingles, much like a cedar shake roofing, the problem was then the gaps between the shingles that would be then have to be covered by another shingle, essentially doubling the weight of the roof. After all these were considered, it was then decided to take the best of both worlds and use a flat shingles that used a curved shingle to cover the gaps between them. These shingals would then stack upon each other with the lip of the flat shingle catching on the

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Proceedings of the Multi-Disciplinary Senior Design Conference Page 3

bamboo trusses of the roof. The curved shingle was attached with a plastic bottle string. This method would divert water away from the curved shingles and down the flat shingles and off of the roof. Putting these two shingle designs together optimized weight and rain management, with the least complex shingle design and fastening.

Figure 3: Flat shingle Figure 4: Rounded shingle Figure 5: Shingle assembly

Test Process A three-point load test was used to find the maximum allowable load on several mix designs. The test

specimens were poured in a 14” x 4” x 1” form factor. The results are shown below in figure 7.

Figure 6: 3 Point load test

Figure 7: Results of the 3 point load test

A cost analysis was performed on each mix based on the components to get an estimate of overall roof cost. The weight of the roof was calculated for the mixes to determine feasibility of being able to work on the current trusses. The results of these two analyses on the final 3 mixes can be seen in table 2. Other engineering requirements like waterproofness, wind test, solar heat gain, and installation time were all performed on a test rig as seen in figure 8. Test procedures were also written up to ensure tests would be done consistently and properly.



Table 2: Summary of cost and weight for top 3 mix designs

Figure 8: Test rig for final shingle tests

Finally, shown in Fig 9 below are the results of the solar heat gain test performed on 5/7/2016. The biochar concrete roof was considerably better than the tin roof at staying closer to ambient temperature. The biochar roof was 29.42% better on average.

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Temperature of Biochar Roof vs. Tin Roof

Biochar Roof Sensor

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Figure 9: Results for Temperature During Solar Heat Gain Test

RESULTS AND DISCUSSION A final mix design, shingle design, and mold design were all chosen based on the analysis completed.A Force/Weight ratio graph was created, as you can see in Figure 10 below, which helped to a make a decision

about choosing a mix.

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Figure 10: Force to weight ratio for the specimen in contention for our final mixEven though Mix 6 had the highest force to weight ratio and Mix 8 had the lowest (shown in Fig.10), the decision was made to go with Mix 8 for a number of reasons. First, the weight for Mix 8 is in a sweet spot in between the other two mixes. The whole roof weight using this mix is 3660 lbs versus 4000 lbs (shown in Table 2) for Mix 6. While not the lowest weight, it does meet our engineering requirement. Another reason mix 8 was chosen is this mix withstood a sufficient amount of weight and the addition of fibers provides a factor of safety since it holds load as the shingle cracks. For this final mix, 10.73 grams of fibers made from the plastic bottle shredder were added for each shingle. Another reason this mix was chosen is the cost of Mix 8 is right between Mix 5 and Mix 6 and does meet our engineering requirement of cost. Finally, the mix was chosen because Mix 6, 7 and 8 fractured at around the same crosshead extension, whereas Mix 5 fractured much sooner (shown in Fig.7). This shows that Mix 5 would have been a poor choice while the other 3 were similar in this regard.

It was decided that this mix was the perfect compromise between cost and weight. It also met the engineering requirements of cost, weight and strength. This final concrete mix is once again summarized in figure 11 and includes 10.73 grams of plastic fibers in each shingle.

Figure 11: Components by volume of our final mix design Figure 12: Final Shingle CAD drawing

The final shingle design was composed of a flat shingle piece and a rounded shingle piece as explained before. The flat shingle contains a concrete lip on the underside that allows it to hook onto the bamboo strapping of the roof and the rounded shingle fits on top of two flat shingles like a puzzle piece. The CAD model of this design can be seen in figure 12. This design will ensure no water leaks through and will handle holding a person. It was also chosen because it was easy to design molds that fit these shapes. Six flat shingles and 3 rounded shingles were poured, built, and placed on the test rig for the final prototype. This can be seen in figure 13. These two pieces ended up fitting well together and were simple to install.



Figure 13: Completed prototype of the roof

The molds started off as wooden molds, but that process was very time consuming and costly. The final molds used to create the shingles were created through a vacuum forming process and can be seen in figure 14. This process involves creating a blank of the shingle out of wood, then placing it under a sheet of 60 mil plastic that had been heated up, and finally sucking to the shape of the shingle using a table that pulls a vacuum. This gives you a reusable, simple, and somewhat durable mold. Each of these molds cost around $2 and many were made to speed up the shingle building process.

Figure 14: Molds for each shingle type

With the prototype built, the remaining engineering requirements could be tested. The results from these tests and whether we satisfied our customer requirements can be seen below in table 3. As you can see, this design passed all of the tests that were performed. Overall, this roof shows great potential and should highly satisfy the customer.

Table 3: Summary of engineering requirements and test results for the prototype

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CONCLUSIONS AND RECOMMENDATIONS

A recommendation for a future project would be to experiment more with the concrete mixture to find the absolute best mix for this application. We were able to find a mix that would meet our engineering requirements but more time was needed to find the best mix. When it came to the 3 point load test, the resulting plot resembled an exponential growth curve as the amount of biochar decreased. It would be interesting to make more mixes in between in order to get a better understanding of the relationship between mix amounts and the strength.

Another recommendation would be to do a little more work with the rounded shingle design created. With the current design, there is about a half inch gap created by the rounded shingle that poses issues if a hurricane were to hit this roof. If this gap could be decreased and the rounded shingle could be more flush with the flat shingle, the design of this roof would improve dramatically. In addition to that would be optimizing the molds of the shingles. A larger draft angle is necessary, because the shingles were difficult to remove from the molds without causing damage to the molds or shingles. A release agent could also be put in the molds to make the shingle release easier.

Another recommendation would be to create a project that looks at the plastic fiber creation and use in more detail. We were able to create a prototype that worked reasonably well. However, it would be interesting to focus on the device and build a sophisticated string maker that would be of higher quality with a faster string making rate. It would also be great to find a way to use all plastic bottle types and not just bottles made of stiff plastic.

In conclusion, the roof created solves many of the problems that are found with the current roofs being constructed in El Sauce. The roof design involves using only locally sourced materials and is cheaper than the current design. It also meets many other specifications set by the customer, like the roof does not leak water and it reduces the solar heat gain in the house. Another benefit of this design is there are many opportunities for the creation of new businesses in Nicaragua. For example, a shingle making business or a plastic string making business are both great opportunities. Overall, this roof is a great option as is or could be a great starting point in the design of a new roof for 4 Walls.

ACKNOWLEDGMENTSWe would like to thank the following groups and individuals for their contribution to our project

● 4 Walls● Ithaka Institute● Manitou Concrete● Civil Engineering Tech Department● Mike Caldwell● Steve Barber
