P14416: Concrete Arborloo Base

System Design ReviewOctober 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 Requirement

s

…. 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 compressio

n

Only basic Tools are needed

Minimally skilled Haitian

Mason can make

Materials are cheap

Easy to provide

good tensile strength with the

additions of reinforceme

nts

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 Generatio

n

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 0Quick to install 0 0 0 - - - 0 0Visually appealing + + 0 + + + 0 +High strength + + 0 - - - 0 0Comfortable + + 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 3Sum 0's 3 3 0 2 1 0 8 5Sum -'s 3 3 0 4 5 6 1 2

Continue? Y Y - N N - Y

Concept SelectionPeter Morgan’s as Datum

Concept SelectionDome 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 0Visually appealing 0 0 0 - 0 0 - +High strength - - 0 - - - 0 0Comfortable - + 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 4Sum 0's 4 6 0 2 4 1 4 3Sum -'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

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 budgetBudget 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 baseCheck 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 designResearch and test lighter aggregatesTest 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?