Transcript EARTHBLOCKS IN THE SUDD: FINDING SOLUTIONS ON UNLIKELY TERRAIN

EARTHBLOCKS IN THE SUDD:
FINDING SOLUTIONS ON UNLIKELY TERRAIN
Chris Rollins, P.E.
Senior Engineer, AECOM International South Sudan
[email protected]
The SUDD
The
PROBLEM
The SOIL
The CATTLE
The YOUTH
The ROADS
The AID
The GOVERNMENT
The SOLUTION?
Dablual - Galvanized roof
Jaac - Largest roof overhang
Manajoka - Concrete block
Alor - Average construction
10 similar projects in 2013, 20+ in 2014
+/-$150k each
How to achieve quality in this environment:
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Modular 3m x 4m layout
Reinforced Concrete frame with CEB non-load bearing wall
All rebar sizing & detailing SAME throughout
Prefab steel doors and windows in city
QA/QC manual with photos
1200W PV System, Rainwater Catchement, VIP Latrine
Energy considerations:
• Building at +/- 10˚N Latitude – sun on S and N!
• Passive Cooling principles – venting, shading, light colored roof, reduce
reflected radiation
• Orient building on E-W axis for shade and max PV energy production
Blockmaking
Makiga Engineering (Nairobi) block press replicates size and shape of Hydraform block (Johannesburg).
Confined
Masonry
Generally a good idea, but in area of extreme wet and dry cycles (and no seismic problems), this
constraining can cause cracking in plaster between dry stack joints when blocks contract when dry.
Typical Construction
2013 Best Practices Grant
WHAT
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Identify methods and materials to develop standards for rural South Sudan
o Theoretical AND practical
o Pave way for future building code?
WHY
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Current construction is very low quality
Keep pre-fabs (‘containers’) and air conditioning (‘split units’) out of the bush
Big Picture - Promote good ideas in a warming world
HOW
• Energy study with temperature and humidity data analysis
• Soil stabilization study with CBR and compression testing
• Earthbag prototype
Other topics in Best Practices Grant:
• PV system optimization, ferrocement and CEB water storage tanks
• QA/QC manual, seminars, training, networking with government and industry
RAISE THE BAR SO THAT OTHERS MUST FOLLOW.
Temperature and Humidity Data Study
Temperature and Humidity Data Study
- Questions
• How does the current design perform?
• How can the design be improved?
Temperature and Humidity Study
- Answers
• Buildings cooler than ambient by as much as 12°C
• Galvanized roof has significantly lower temperatures.
• Concrete Masonry Units underperform CEB buildings –
hotter day AND night.
• 2-hour lag between the hottest ambient (2:30 p.m.)
and the hottest interior (4:30 p.m.)
o Good for office building
• Nighttime interior temp 2-3°C higher than ambient
o Poor for housing
o May not find more efficiency without active cooling
11:30 a.m.
12:30 p.m.
9:30 a.m.
7:30 a.m.
2:30 p.m.
3:30 p.m. – hottest time of day
5:30 p.m.
4:30 p.m.
Psychrometric Chart at 95.5 kPa
0.0220
0.0200
Manajoka
0.0180
Dablual
0.0160
Jaac
0.0140
0.0120
0.0100
0.0080
0.0060
0.0040
ASHRAE Comfort Zone
0.0020
0.0000
0
10
20
30
40
50
Dry Bulb Temperature (°C)
• Cannot hit ASHRAE zone without reducing humidity!
Humidity Ratio (kgw/kgda)
Alor
Performance in afternoon sun
• Shade from water tank lowers building surface temp up to 10˚C
• Should emphasize landscaping and/or curtain wall going forward.
Soil Stabilizer Study
Soil Stabilizer Study –
Questions
• What compression strength are we achieving with
current techniques and mixes?
(10-12% cement by volume)
• What compression strength is possible?
• Can we use CBR data to infer compression strength?
• What alternative stabilizers might be stronger, more
durable, easier to use, and cheaper?
Soil Stabilizer Study –
Answers
• Current compression strength is terrible: <1 MPa.
• Lime has very good CBR results but poor
compression testing results
(no correlation between CBR and compression methods)
• Liquid stabilizers (Earthzyme and Claycrete) appear
to achieve 2Mpa strength at much lower cement %
• Weatherization study ongoing – which stabilizer will
return best long term results in this wet/dry cycle?
Traditional Authority Center 2011
Oldest building in program, built in most unfavorable conditions.
Cohesion and Adhesion Failure
Is this due to salt build-up, use of cement bag wash, internal wet/dry cycles in block, or combination?
GRADATION TEST
• South Sudan is a swamp - soils are very fine due to low energy
• Inconsistent results on same sample from three different labs
(See Gudele samples)
California Bearing Ratio test
CBR test measures pressure required to
penetrate a soil sample (soaked in water); divide
by the pressure required for equal penetration
on a standard crushed rock material.
Compression Testing
Hydraform block press (Johannesburg) used to make blocks for more consistent ‘laboratory’ conditions.
Curing is typical
Hydraform block testing machine (Johannesburg) will be used solely for field testing in future, but a more
accurate test device must be procured first.
Compression testing results are not consistent with CBR data, and also not rational – must repeat.
Blocks are currently curing for long term (90-day) compression testing, one sample of each removed from
tarp for weatherization study.
4% cement
4% lime
4% ANSS
Claycrete + 4% cement
Earthbag Prototype –
Questions
• Are earthbags a suitable alternative to
chemical stabilization?
• Is this cheaper (product + transport + labor)?
• Can local people use this technology at home?
• Could this create cottage industry making
bags?
Earthbag Prototype –
Answers
• Very difficult getting outside expert to assist,
therefore project was not managed.
• AECOM team and local community very
enthusiastic about technology:
‘I am going to build my house like this!’
• Problems filling bags in rainy weather,
resorted to 1:12 stabilized sand.
• Will try again in dry season on larger project.
Bags from Eternally Solar in Capetown
What’s Next?
• Soils lab necessary for accurate engineering study!
• Build 1-2 buildings with earthbags, using better
management and outside expert.
• Build 1-2 buildings with different stabilizers: Claycrete,
other.
• Study stabilizer combinations (i.e. lime + cement)
• Attempt some kind of active cooling system – undecided
o floor - earth temp may be higher than ambient at night!
o evaporative – potential mold problems, legionnaires’ disease?
• Emphasize landscaping or low-cost curtain wall to reduce
reflected and direct radiance.
• Try new ideas from US, Germany, Mexico, Brasil, Spain, etc.
Thank you!
Chris Rollins, P.E.
Senior Engineer, AECOM International South Sudan
[email protected]