spin issues on soil cement construction

8/13/2019 Spin Issues on Soil Cement Construction

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ISSUES ON SOIL-CEMENTCONSTRUCTIONHC UzoegboUniv of the Witwatersrand South Africa

The built environment is estimated to contribute

approximately 40% of total energy use and associated greenhouse gas (GHG) emissions globally

the biggest contributors to GHG are found to be

concrete and steel. Cement in concrete is main contributor to GHG.

Followed by transportation of materials.


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Greener Concrete

Reduce the amount of cement without

compromising quality.

Partial cement replacement (eg pozzolans)

Deposits of natural pozzolans in Rift Valley, E. Africa

Use soil of soil cement for low-rise housing

Reduce distance of material transportation


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Why soil-cement blocks


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CASE STUDY


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Basic Mix Design


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Sieve the soil after excavation, use the

soil from the construction site.


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Load the soil and cement into the mixer


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Mix the soil, cement and water

5% Cement

(by volume)4MPa block

8% Cement

(by volume)

7MPa block


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BLOCK PRODUCTION

M7 MOBILE BLOCK MACHINE


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Manual Block Machine


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After 2-3 minutes mixing move the mix

to the compression chamber


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Carry and stack the block, cure for 7

days


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Hydraform Blocks

Length- 240mm

Width - 220mm ( or 140mm)

Height - 115mm


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Hydraform Blocks

37 blocks / m2 of wall.

1m3 soil for 75 blocks.

1 bag of cement for 100 blocks. Minimal mortar between blocks, dry stacked

interlocking speeds up construction, 220mm

block.


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Cost Comparison


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COST COMPARISON


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Lessons from Ancient Dry-Stack

Construction

Great Zimbabwe Ruins

Capital 15th Century

Shona Kingdom


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FREE-STANDING WALLS

Need to tie top

courses to prevent

toppling


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BULGING OF RETAINING WALL PANELS


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SPLITTING IN WALL PANELS


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VERY LOW ARCHING MECHANISM


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Construction with Interlocking Blocks


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House in Johannesburg, SA


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House in Malawi


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Hydraform House in Malawi

f


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Hydraform House in Malawi


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Assessment of Block Unit Strength

A real challenge due to irregular shape

Test method must be developed for every

interlocking design

Three methods of testing for compression

strength of Hydraform blocks


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1. Centre Top Loading

Hydraform Block

Top machinesteel platen

Bottom machine

steel platen

P

Hard board


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Failure mode


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2. Shoulder Loading

Aditional Steelbearing platen

Hydraform Block

Top machinesteel platen

Bottom machinesteel platen

P

Hard board


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Failure Mode


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3. Cube Testing

Cube - 1

Cube - 3

Cube - 2

Cube - 4

Top Side(Low Density)

Bottom Side(High Density)

Hydraform Block

Top machine

steel platen

Bottom machinesteel platen

P

Hard board

Hard board


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Normalised strength factors


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Center Vs. Shoulder Testing

(15% cement content blocks)

0

3

6

9

12

15

18

Wet Specimens Dry Specimens

SpecimensStrength[MPa]

Centre

Loading

Shoulder

Loading

ll l


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Dry-Wall Panel Assessment

L t l L di W ll P l


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Lateral Loading on Wall Panel

Test Wall


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Test Wall3 June 2008 The Structural Engineer 25, C. Mundell

Dry Wall Prior to Failure


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Dry-Wall Prior to Failure3 June 2008 The Structural Engineer 25, C. Mundell


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E i l f l l l d


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Experimental set-up for lateral load test

LATERAL LOADING


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LATERAL LOADING

O S


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FAILURE MODE: MEDIUM SPAN


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FAILURE MODE: LONGSPAN

FAILURE MODE:PLASTERED DRY-STACK


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FAILURE MODE:PLASTERED DRY STACK

WALL


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FAILURE MODE:CONVENTIONAL WALL


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Load-Deflection Curves

Conventional MasonryLoad-deflection behavior for standard mansory brick wall

0.00

1.00

2.00

3.00

4.00

5.00

6.00

-20 0 20 40 60 80 100 120

Deflection (mm)

Load(Kn/m2)

gage1

gage2

gage3

gage4


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Load-Deflection CurvesCombination plot of middle point (gage1)

0

1

2

3

4

5

6

7

-20 0 20 40 60 80 100

Deflection (mm )

Loadcapacity(kPA)

5PB

5RBG

PW

2RBG(10mm)

2PB

RPW

2RBG(20mm)

SMW

Conclusions


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Conclusions

Cement stabilised soil block is cheaper than

conventional concrete block

Clay content of soil is necessary for early age

handling and stability

Approx. 40% loss in strength under sustained wet

conditions

spin issues on soil cement construction

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