P14416: Concrete Arborloo Base

1. P14416: Concrete Arborloo Base System Design Review October 1, 2013

2. Team Introduction & Roles

3. Agenda Background/Problem Statement Open Items Specifications Benchmarking/Concrete Introduction Concept Generation Concept Selection Engineering Analysis Test Plan Materials Considered Potential Risks Plans Moving Forward

4. Arborloo • A latrine-like sanitation device designed to function over a small pit and to be moved to a new pit when filled • Utilize compost by planting tree in used pit • Purpose to provide affordable sanitation in poor, underdeveloped areas • Originally designed for use in Zimbabwe

5. Problem Statement • Current State • Today’s arborloo takes two days to install and is not easily transportable. The current design is also not socially appealing to the Haitian population. • Desired State • Provide an affordable concrete base that is easy to move and install. The desired base should be aesthetically pleasing to users and a worthwhile purchase for sanitation improvements rather than storage or social status. • Project goals • Low cost (<$50 to purchase) • Base design that safely covers an 18-20” diameter, 3-4 ft. deep hole • Easily constructed using simple hand tools • Portable • Resistant to environmental damage • Has modular design • Haitians want to purchase • Constraints • Proposed budget= $1500 • Base must be relatively lightweight for transportation • Base must be made using concrete

6. Open Items • Safety Rating • Considered separately from main function of supporting weight • Other factors (tripping and slipping hazards) don’t influence design decisions as significantly • Clarified that time constraint refers to home setup • Changed tripping hazard definition to comply with OSHA standard • Changed survey method to choosing between multiple alternatives

7. Customer Requirements Importance Scale

8. Cost • Easy Transport • Quick to Assemble • Strength Importance Scale - 9 Customer Requirements • Safe • Visually Appealing • Comfortable • Accommodates Large Hole in Ground • Modular Importance Scale - 3 …. Based on Concept Selection Criteria

9. Engineering Requirements

10. Peter Morgan’s Arborloo • DIY Project • Composition • Bag of cement • “Good river sand” • Thick wire • Mounted on a “ring beam” of bricks or concrete • Molded from bricks • Addition of soil, wood ash & leaves creates compost

11. Other Arborloos? • Current concrete Arborloos have typical cement, sand, and gravel composition • Wire or rebar for reinforcement • Flat or slightly domed circle and square shaped • Catholic Relief Services reports $5-8 for Arborloo in Ethiopia • 2-3 slabs made from one bag of cement

12. Benchmarking • Effective fiber volume is at a 0.75% fraction • Variety of Different aggregates and reinforcements • Reinforcement patterns • Material Properties of different fibers • Haitian Perspective * Based on Pedro Cruz-Dilone Paper

13. Why Use Concrete? Available in Haiti Tough/ Durable Strong in compression Only basic Tools are needed Minimally skilled Haitian Mason can make Materials are cheap Easy to provide good tensile strength with the additions of reinforcements Test standards already created and available

14. Concrete Background Holly Holevinski Cement + water = paste Aggregates: Coarse (>1/4”) Fine (<1/4”) Reinforcement (rebar) Fiberglass, plastic, steel Add mixtures: reduce weight Air-entrainment Foaming materials Accelerators and retarders

15. Concrete Background • 5 types of Portland cement • Types I – V • Type I & II General use • Type IV- “High Early” • Reaches its maximum strength within 24 hours • Window when paste is moldable 0-90 minutes • Final set at 120 minutes • 3000 psi goal for slab

16. Concrete Background • Concrete Tips: • Concrete cannot go below 80% RH during cure process • Rebar should not touch any open areas • Use plastic to keep moisture in, spray concrete regularly if possible • Mix parts of Portland cement with cheap substitutes (fly ash, silica fume) • Concrete must be at least 30% Portland cement

17. Functional Decomposition

18. Functional Architecture

19. Concept Generation

20. Concept Generation:Key Functions

21. Concept SelectionPeter Morgan’s as Datum

22. Concept SelectionDome as Datum

23. Selected Concept #1 - Dome • PROS • Round edges allow for compressive strength advantages • Attractive design • Safe • Comfortable • CONS • Difficult to make modular • Difficult mold design • Hard to transport • Cost

24. Selected Concept #2- Hollow “Puzzle Piece” Cone • PROS • Comfortable • Visually appealing • Modular • Pieces provide support for each other • CONS • Less safe • Mold design • Cost • Long assembly time

25. Selected Concept #3 - Triangle • PROS • Less Material • Simple Mold Design • Low Cost • Visually Appealing • CONS • Difficult to transport • Not modular • Difficult to interface with hole • Stress concentrations in corners

26. Concept Selection #4- Circular “Peter Morgan’s” • PROS • Accommodates large hole in ground • Safe • Relatively easy mold • Easy to transport • CONS • Not modular • Not comfortable • Not visually appealing

27. Engineering Analysis • Using ANSYS and material properties of standard concrete: • Poisson’s Ratio: 0.3 • Elastic Modulus: 4e6 psi • Assumed an applied Pressue of 500 lbs

28. 2D Circle and Triangle Slabs

29. 3D Dome and Cone Slabs

30. Test Plan • Compression Test • Verify strength of concrete • Determine how aggregates/fillers effect strength of concrete • Flexural Test (with/without reinforcement) • Determine advantages of certain reinforcement concepts • Tensile Strength • Transportation • User Interaction

31. Compression Test Flexural Test

32. ASTM Standards C150- Standard Specification for Portland Cement C330-Standard Specification for Lightweight Aggregates for Structural Concrete C470-Standards for Specification for Molds for Forming Concrete Test Cylinders Vertically C39- Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens C78-Standard Test Method for Flexural Strength of Concrete

33. Materials to Test- Aggregates (course and fine) Effect the weight and compressive strength of concrete: • Chopped up rubber tires • Sand • Coconut shell • Bean bag filler • Glass bubbles • Grass/leaves • Styrofoam • Ground up water bottles • Clay

34. Materials to Test-Reinforcements Effect the strength by absorbing some of tensile stresses • Rebar • Snow fence • Window screen • Chicken wire • Corrugated metal sheets • Steel rods • Fishing line • Nylon rope • Onion bags (mesh) • Plastic bags • Bicycle spokes • Banana fibers • Sisal fibers

35. Risk Assessment

36. Other potential issues • Instructions do not allow for easy assembly or installation • Plan: Provide simple picture instructions • Aggregate mixtures are inconsistent and unrepeatable • Plan: Document every quantifiable value for mixtures and measurement • Base is not “attractive” to purchase • Plan: Research through interviews/surveys with Haitian locals and visitors • Time constraint (EPA in DC) • Stay ahead of Mycourses outline • Work during Intercession break

37. Moving Forward • Specimen testing • Continue aggregate research • Optimize concrete performance • Create more detailed designs • Update EDGE • Continue to consider Customer requirements as we make decisions

38. Additional Questions/Opinions? Shapes Feasibility Additional materials to test