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?