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Abstract

Fig 1: Fig 1: Unsatisfactory path at Catherine Zane Middle School.

The purpose of the project was to replace a incorrectly installed permeable pathway (Fig 1) at Catherine Zane Middle School in Eureka, CA with a functioning permeable pathway. The previously installed pathway was uneven, and impermeable and produced undesirable loose gravel. The project was successfully implemented and the middle school now has a solid, level, and permeable concrete pathway in the Peace Garden.

Background

The project is being design and installed by Team^2 (Fig 2) whose members are Ailynn Andersen, Jesse Bobrow, Catherine Carbajal and Julian Sicaud. Team^2 is a team in HSU's Engineering 215: Intro to Design course taken in Spring 2018 and taught by Lonny Grafman. The client of the project is Catherine Zane Middle School, a Science Technology Engineering and Math (STEAM) school which has had a relationship with facilitation projects on their campus for ENGR 215 courses. Team^2's client representative is Trevor Hammons, a school administrator.

Fig 2: Team^2!

Problem statement and criteria

In the Peace Garden a previous engineering team had incorrectly installed a permeable concrete pathway. We hypothesized that there was too much water in their mix which caused the cement to sink to the bottom of their installation and harden into an impermeable layer. This left too little cement in the top layer to properly set aggregate. Aggregate erosion resulted in loose gravel, which pedestrians tracked across campus. Our client wished us to solve these issues by implementing a pathway that was strong, durable, level, permeable, and seamless with the other pathways.

Criteria Weight (1-10)
Durability 10
Permeability 10
Functionality 8
Maintenance 7
Cost 6
Educational Value 5

Description of final project

The final product should be a permeable concrete pathway that seamlessly merges with the surrounding pathways and curbs. The path should be level and smooth ensuring an effortless user experience. The pathway material should also be porous to allow water to permeate through the pathway into the surrounding garden beds.

Prototyping

Fig 3: Prototype Porous concrete block.

Permeable Concrete is made from a mix of round aggregates of equal size and Portland cement. Typical mixtures usually consist of a 3:1 ratio of three parts 3/8" pea gravel aggregate to one part Portland cement. We decided to test both permeability and viability as product of this ratio by testing it against both a 4:1 and 2:1 ratio of aggregate to cement. We poured samples (fig 3) of each ratio into one foot square molds to the depth of three inches.

Testing Results

We ran three tests on each prototype ratio concrete sample in order to determine the rate of permeability or the speed at which water drained through the material. To test our prototype slabs we built a box of wood around each block and added silicone to seal the inside seams and corners. We leveled the boxes and placed two water balloons filled with approximately 2 gallons of water in each (Fig 4). We then popped both of the balloons at the same time and measured the time it took for the volume of water to permeate through the each sample. The table below contains the results of our tests. With each ratio (4:1, 3:1, and 2:1) of aggregate to cement, we found that they all produced a strong and highly permeable concrete sample. This told us that mixing a precise ratio of aggregate to cement was not as crucial in producing a viable concrete as other concerns, such as adding the correct moisture level or properly curing the mix after installation.

PERMEABILITY CHART.JPG

Fig 4: Prototype permeability testing set up.

We decided to make site measurements of the old path installed in the Peace Garden. We made measurements of each section's dimensions, which we then entered into AutoCAD and rendered into a viable blueprint plan Fig 5) for the pathway. We also rendered a 3D example of a typical path section block of porous concrete (Fig 6). The pathway in the garden is approximately 62 feet long and is composed of ten sections that are approximately six feet long by two and a half feet wide by three inches tall. We calculated that the overall volume of concrete needed to pour was a little under forty cubic feet or just over a cubic yard.

Fig 6: 3D render of path section.
Fig 5: Plan for path install.

Costs

Our project would never have come to fruition without generous donations. The project budget was $400 but our expected costs rose to over $1000! Because of our donations and community help we spent less than $200.

Materials Source Quantity Unit Retail Price per unit ($) Total Retail ($) Expenses ($)
3/8" Washed Pea Gravel Mercer-Fraser 2 Cubic Yard 60.00 120.00 Donated
3/8" Washed Pea Gravel Hensell Materials 2 5 gallon bucket 4.00 4.50 Donated
Weed Cloth Zane Middle School 1.2 100 feet 68.99 68.99 Donated
Mixing Wheelbarrow Larry Nichols/Zane 2   150.00 300.00 Donated
5 Gal. Bucket Julian Sicaud 4 4.99 4.99 Donated
1 Foot Wooden Stakes Zane Middle School 1 100 Stakes 17.50 17.50 Donated
Bender Board Zane Middle School 6 20 Feet 19.99 120.00 Donated
Fill Dirt Zane Middle School 2 Cubic Yard 7.99 15.99 Donated
Portland Cement Piersons Hardware 5 97 lb bag 16.99 84.95 Donated
Tarp Julian Sicaud 2 15.99 31.98 Donated
Shovel Julian Sicaud 2 23.86 23.86 Donated
Portland Cement Hensell Materials 1 47 lb bag 6.07 6.77 6.77
Portland Cement Shafer's Hardware 1 47 lb bag 9.99 10.84 10.84
Line Level Piersons Hardware 1 3.69 4.00 4.00
Shovel Piersons Hardware 1  21.99 23.86 23.86
Garden Hoe Shafers Hardware 2 16.99 16.99 16.99
Hose Valve Key Shafers Hardware 1  1.79 1.79 1.79
#9 x 2-1/2"  Deck Screws Hensel's Hardware 1 50 screws 9.78 9.78 9.78
Wood Almquist 14 Feet 1.09 16.44 16.44
1" x 4" pine Piersons Hardware 30 Feet 0.69 20.42 20.42
Wheel barrow Tube Miller Farms 2 9.64 19.28 19.28
Caulking Gun Harbor Freight Tools 1  2.99 2.99 2.99
Silicone caulk Harbor Freight Tools 2 Tube 3.99 7.98 7.98
Balloons Dollar Tree 5 Bag of 25 1.00 5.43 5.43
Caution Tape Shafers Hardware 1 Roll 7.59 7.59 7.59
Gloves Harbor Freight Tools 5 pair 7.99 7.99 7.99
Push Broom Shafers Hardware 1 7.99 7.99 7.99
Plastic Sheeting Piersons Hardware 1 9 x 400 Feet 24.99 27.11 27.11
TOTAL 990.01 197.25

Design Hours

The team spent the most time testing materials and on implementation which required time top acquire tools and materials before installation and the curing time after installation.

Permeablepath18 Designhours 1.png

Final Product

Images coming soon!

File:Permeablepath18_Sledgehammer_1.jpg
How to Install a Permeable Concrete Pathway

Maintenance

Recommended maintenance of the pathway consists of powerwashing twice a year. This ensures that small objects will not clog the holes in the path way.



References

See Help:Footnotes for more. Template:Reflist Paths for All. (2014). “Permeable Material (Surface).” <https://www.pathsforall.org.uk/pfa/glossary-of-path-construction-terminology/permeable-material-surface.html> (Feb. 18, 2018).

How Cement is Made. (n.d.). Retrieved February 21, 2018, from http://www.cement.org/cement- (Links to an external site.)Links to an external site. concrete-applications/how-cement-is-made

Pervious Concrete. (n.d.). Retrieved February 21, 2018, from http://www.washingtonconcrete.org/pervious-concrete

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