Rammed earth mix design
This presentation is the property of its rightful owner.
Sponsored Links
1 / 14

Rammed Earth: Mix Design PowerPoint PPT Presentation


  • 144 Views
  • Uploaded on
  • Presentation posted in: General

Rammed Earth: Mix Design. Will Hunter ECI 281a Term Paper Presentation. Overview. Brief History Materials Construction Methods Stabilization Problems?. (Courtesy Rammed Earth Development, 2004 [1]). Origins & History. Related to Adobe, cob, and brick construction

Download Presentation

Rammed Earth: Mix Design

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Rammed earth mix design

Rammed Earth: Mix Design

Will Hunter

ECI 281a

Term Paper Presentation


Overview

Overview

  • Brief History

  • Materials

  • Construction Methods

  • Stabilization

  • Problems?

(Courtesy Rammed Earth Development, 2004 [1])


Origins history

Origins & History

  • Related to Adobe, cob, and brick construction

  • Dates back 10000 years [2]

  • Found on all continents except Antarctica [2]

(Courtesy Takeuchi Nozomu, 2006 [2])

(Courtesy Takeuchi Nozomu, 2006 [2])


Materials

Materials

  • Historically 70% sand, 30% clay [3]

  • Modern construction

    • Well graded

    • Quarry fines

    • Optional stabilizer

  • As little organics as possible (1-2%) [4]

  • Prepare at optimum moisture content

  • 200 tons of soil for a typical home

Typical particle-size distribution for rammed earth soils. The names of the soils correspond to their composition in terms of sand, gravel, and clay (ie 712 has 7 parts sand, 1 part gravel, and 2 parts clay) [4]


Construction methods 3

Construction Methods [3]

  • Constitutive soils thoroughly mixed and moistened

    • Buckets, loaders, rototillers

  • Soil laid in forms (similar to concrete)

    • Numerous form styles

  • Compacted using impact methods

    • Done monolithically in lifts of ~8” (~4-5” compacted)

    • Maximum compaction indicated by “ringing sound”

  • Typically tied together with concrete bond beam at top

Pneumatic backfill tamper (Courtesy Kehm Equipment, Inc. [5])


Stabilization

Stabilization

  • Unstabilized Rammed Earth

    • Relatively high compressive strength ( up to 800 psi) [6]

    • Water-soluble

    • No tensile strength

  • Basis for Stabilization

    • Higher strengths required in seismically active areas

    • Waterproofing in wet areas

  • Stabilizing Agents [8]:

    • Portland cement

    • Lime

    • Asphalt emulsion

    • Fly ash


Stabilization cont

Stabilization (cont.)

  • Most common stabilizing agent: Portland cement

    • Essentially becomes well-compacted soil-cement

    • Cement content: anywhere from 3-15% by weight

    • Optimum content ~6-9% depending on soil type [7]

    • Benefits include higher strength and greater resistance to moisture ingress / damage

Unstabilized RE sample (at left) compared to a 6% cement stabilized RE sample (right) after a 1 hour absorption test [7]


Rammed earth use in california concerns

Rammed Earth Use in California: Concerns

  • Seismic Performance

    • Bond beams

    • Cement stabilization

    • Semi-cold joint between lifts

  • Waterproofing / Moisture Ingress

    • Clay content

    • Variations in density


Water resistance

Water Resistance

  • Unstabilized RE is essentially a water-soluble material

  • High clay content (up to 30%) – swelling / expansion / cracking [8]?

    • Kaolinite: low expansion potential, suitable for use

    • Montmorillonite, Bentonite: high expansion potential, unsuitable


Water resistance cont

Water Resistance (cont.)

  • Factors in Moisture Ingress [7]

    • Capillary suction

    • Pressure differential

    • Surface finish

  • SSA / % Clay – Proposed indicator of granular stabilization

    • 3.35 Ratio [9]

Mass of water absorbed due to capillary suction versus the square root of time [9]

SSA & 3.35 Ratio for different soil mixes [9]


Factors governing mix recipes

Factors Governing Mix Recipes

  • Soil particle-size distribution is the single biggest factor in the ultimate properties of a RE wall

  • Fines Content

    • Silt: undesirable

  • Addition of Cement?

    • Increases fines content

    • Optimum moisture content for compaction compared to that for cement hydration

    • Excess cement = essentially silt (bad)

  • Strength Requirements (Seismic Zone?)

  • Aesthetics


Mix recipes cont

Local soils versus imported?

Quarry fines typically used

Nun’s Canyon Quarry locally [8]

Mix typically chosen by architects, contractors

Aesthetics

Moisture content

Proper mixing

Field tests (thread test, ribbon test, soil ball test [3])

Mix Recipes (cont.)

Soil ball test [6]


Additional concerns

Additional Concerns

  • No building codes

    • Typically falls under “unreinforced masonry” [6]

    • Submittal to building department… how?

  • Openings in walls?

    • Lintels

  • Construction strength versus ultimate strength

    • 30 psi immediately, up to 300 psi (unstabilized) [6]

  • Bond strength between reinforcing/earth

  • Uniform mix, uniform water content

Compaction using pneumatic backfill tamper [1]


References

References

  • Rammed Earth Development. Rammed Earth Development. 2004. 02 Dec. 2006 <http://www.rammedearth.com/>

  • Takeuchi, Nozomu. The Western China. 2006. 03 Dec. 2006 <http://www-es.s.chiba-u.ac.jp/~takeuchi/China.html>

  • Easton, David. The Rammed Earth House. Vermont: Chelsea Green Publishing Company, 1996.

  • Hall, Matthew, and Youcef Djerbib. “Rammed Earth Sample Production: Context, Recommendations, and Consistency.” Construction and Building Materials 18 (2004): 281-286.

  • Kehm Equipment, Inc. Model 131. 2001. 02 Dec. 2006 <http://www.kehm.com/apt_5214_backfill_tamper.htm>

  • McHenry, Paul Graham Jr., and May, Gerald W. Adobe and Rammed Earth Buildings: Design and Construction. New York: John Wiley & Sons, Inc., 1984.

  • Hall, Matthew, and Youcef Djerbib. “Moisture Ingress in Rammed Earth: Part 2 – The Effect of Particle-Size Distribution on the Absorption of Static Pressure-Driven Water.” Construction and Building Materials 20 (2006): 374-383.

  • King, Bruce. Buildings of Earth and Straw: Structural Design for Rammed Earth and Straw-Bale Architecture. California: Ecological Design Press, 1996.

  • Hall, Matthew, and Youcef Djerbib. “Moisture Ingress in Rammed Earth: Part 1 – The Effect of Soil Particle-Size Distribution on the Rate of Capillary Suction.” Construction and Building Materials 18 (2004): 269-280.


  • Login