P14416: Concrete Arborloo Base System Design Review
October 1, 2013
Member Role
Victoria Snell (ISE) Project Manager
Evan Burley (ME) Engineer
Joe Omilanowicz (ME) Engineer
Mac Keehfus (ME) Engineer
Anthony Deleo (ISE) Engineer
Team Introduction & Roles
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
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
Arborloo
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
Problem Statement
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
Open Items
Customer Requirements
9
The system costs less than $50-$100 to users (at production level quantities).
The system is lightweight and moveable (by donkey or person walking for up to 6 hours)
The system can be installed in less than 4 hours.
The system can be installed with simple hand tools.
The system confers social status to the owner.
3
The system supports the user over an arborloo hole 18-20” in diameter, 3-4 feet deep
The system is safe to use for users (falling, tripping, slipping, moving to new hole).
The system keeps pests out of the pit.
The system looks “modern” in a Haitian context.
The system is welcoming and comfortable.
The system can be financed in parts.
1 The system is a product, not a DIY project.
The system resists weather and pest damage.
The system minimizes environmental impact throughout the lifecycle.
Importance Scale
Cost
Easy Transport
Quick to Assemble
Strength
Safe
Visually Appealing
Comfortable
Accommodates Large Hole in Ground
Modular
Importance Scale - 9
Importance Scale - 3
Customer Requirements
…. Based on Concept Selection
Criteria
Engineering Requirements
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
Peter Morgan’s Arborloo
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
Other Arborloos?
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
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 reinforcement
s
Test standards already
created and available
• 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
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
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
Concrete Background
Functional Decomposition
Functional Architecture
Concept Generation
Functions
Covers Hole in Ground
Support Weight
(reinforcement)
Support Weight
(aggregates)
Transports Waste
Easy to Transport
Simple to Assemble
Withstands Damage
During Transport
Remains Stable
Easily Cleaned
Withstands
Environmental
Damage
Reduces Odor
Stability
No Pests
Modular
Interface with Shelter
Aesthetics
Ergonomic
Concept Generation: Key Functions
Functions
Covers Hole in Ground
Support Weight
(reinforcement)
Support Weight
(aggregates)
Transports Waste
Easy to Transport
A B C D E F G H
Selection Criteria
Dome
(hollowed out)
Cone
(hollowed out)
Peter Morgan's
Arborloo
Oval
(Puzzle)
"X" "Lincoln Logs" Square Triangular
Low cost - - 0 - - - 0 +
Easy to transport - - 0 + + + - -
Safe - - 0 - - - 0 0
Quick to install 0 0 0 - - - 0 0
Visually appealing + + 0 + + + 0 +
High strength + + 0 - - - 0 0
Comfortable + + 0 0 0 - 0 0Accomodates variable
holes 0 0 0 0 - - 0 -
Modular 0 0 0 + + + 0 0Can be done in 2
semesters + + 0 + + + + +
Sum + 's 4 4 0 4 4 4 1 3
Sum 0's 3 3 0 2 1 0 8 5
Sum -'s 3 3 0 4 5 6 1 2
Continue? Y Y - N N - Y
Concept Selection Peter Morgan’s as Datum
Concept Selection Dome as Datum
A B C D E F G H
Selection Criteria
Peter Morgan's
Arborloo
Cone
(hollowed out)
Dome
(hollowed out)
Oval
(Puzzle)
"X" "Lincoln Logs" Square Triangular
Low cost + + 0 + + + + +
Easy to transport + 0 0 + + + + +
Safe + 0 0 0 0 - + -
Quick to install 0 0 0 - 0 - 0 0
Visually appealing 0 0 0 - 0 0 - +
High strength - - 0 - - - 0 0
Comfortable - + 0 - - - - -Accomodates variable
holes 0 0 0 0 - - 0 -
Modular 0 0 0 + 0 + 0 0Can be done in 2
semesters + + 0 + + + + +
Sum + 's 4 3 0 4 3 4 4 4
Sum 0's 4 6 0 2 4 1 4 3
Sum -'s 2 1 0 4 3 5 2 3
Continue? Y Y - - - N Y Y
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
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
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
Concept Selection #4- Circular “Peter Morgan’s”
CONS
Not modular
Not comfortable
Not visually appealing
PROS
Accommodates large hole in
ground
Safe
Relatively easy mold
Easy to transport
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
2D Circle and Triangle Slabs
3D Dome and Cone Slabs
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
Test Plan
Flexural Test Compression Test
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
ASTM Standards
Materials to Test- Aggregates (course and fine)
Chopped up rubber tires
Sand
Coconut shell
Bean bag filler
Glass bubbles
Grass/leaves
Styrofoam
Ground up water bottles
Clay
Effect the weight and compressive strength of concrete:
Materials to Test- Reinforcements
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
Effect the strength by absorbing some of tensile stresses
Risk Assessment
Risk Item Effect Cause Lik
eli
ho
od
Se
veri
ty
Imp
ort
ance
Action to Minimize Risk Owner
Spend more than our
budget allows
Unable to purchase
necessary items
Overspending on
unnecessary
materials 1 2 2
Develop a Bill of Materials that is
well under our given budget
Budget Tracker
Anthony
Hole in concrete is deemed
unsafe Child could fall through
Inability to follow
customer
requirements 1 3 3
Pay close attention to the safety of
the hole size relative to the rest of
the base
Check against playground standard
after design drawings are done
Mac
Design is too hard to
transport
Device becomes
immobile defeating the
purpose of improved
sanitation
Not modular and/or
too heavy 2 3 6
Research ways to make concrete
more light and implement that into
our design
Research and test lighter aggregates
Test multiple times and recreate
Joe
Base cracks under minimal
load Useless device
Lack of
reinforcement 2 3 6
Obtain multiple reinforcement
materials that increase tensile
strength by November
Mac/Evan
Poor concrete
mixture 2 3 6
Research ways to mix concrete and
talk to concrete experts Team
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
Other potential issues
Specimen testing
Continue aggregate research
Optimize concrete performance
Create more detailed designs
Update EDGE
Continue to consider Customer requirements as we make decisions
Moving Forward
Shapes
Feasibility
Additional materials to test
Additional Questions/Opinions?