HOW MUD BRICKS WORK: A YEAR OF RESEARCH

HOW MUD BRICKS WORK:
USING UNSATURATED SOIL MECHANICS TO EXPLAIN THE
MATERIAL PROPERTIES OF EARTH BUILDINGS
A YEAR OF RESEARCH
DR PAUL JAQUIN
EDINBURGH, RAMBOLL UK
Introduction
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Paul Jaquin, MEng and PhD at Durham,
now a Civil engineer for Ramboll in
Edinburgh
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This presentation - a year of research
Last year’s paper
Mud bricks and unsaturated soil
The state of research into earth building
Comparisons to other more conventional
building materials
Structural and mechanics research
Low carbon and building physics
Heritage structures
The way forward…...
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Unsaturated soil and mud bricks
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Based on my PhD work, where we
showed that mud bricks are basically like
sandcastles, held together by little
bridges of water.
Potentially a step change in
understanding of mud bricks, enabling a
more scientific understanding.
5μm spheres with water bridges between
Sandcastles Weston-super-mare beach
Mud brick home. Pokara ,Nepal
Existing research in earth building
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Materials specification method
based and improvement based on
experience
Structural design based on empirical
methods and very simple testing
Most NGOs work to simple
guidelines which are not developed
from year to year.
Only New Zealand has developed full
design guidelines
Scale model earthquake tests. Minke (2001)
Steel,concrete, timber and masonry
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1781 - Ironbridge.
1824 - Portland Cement developed
1884 - Reinforcement using twisted steel.
1917 - ASTM develop standard formula for
Portland Cement.
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1992 – 2010 - Eurocodes developed
International Building Code - United States
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Little mention of earth building
Little scientific understanding, therefore
difficult to develop codes of practice.
Research this year –
Materials testing and structural mechanics
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Durham University – Chris Beckett
Bristol University – on next!
University of Western Australia – Cyclone
loading
Poured particle arrangement
Shaking table
Wind loading test apparatus
Research this year – Low carbon and
building physics
RHexternal = varies
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Visiting research
fellow at Bath
University
Continued by
Antonio Borges
Thermal modelling
by Celia Macaedo.
Oxford Brookes
RHexternal = 100%
RHexternal = 50%
Water vapour flow
Water vapour flow
RH internal = varies
RH internal = 50%
RH internal = 75%
Building construction
100% RH outside,
raining. Water vapour
flow through the wall,
increasing internal
RH
RH = 50%
1
RH= 50%
RHexternal = varies
RH internal = 75%
Introduce water vapour
source (eg cooking), water Over time RH of the inside
vapour flow through wall,
of the building becomes
reducing internal RH
constant
RH = 70%
2
RH = 50%
Water vapour flow
RH = 70%
3
RH = 60%
4
RH = 60%
RH = 50%
Water vapour flow
Water vapour flow
RHAir=change
50%
Initial conditions, RH
of room and pore air
are equal at 50%
Introduce water vapour
source, increase in water
content of the earth wall,
RH of room remains
constant as water vapour
is absorbed into the wall
Remove water vapour
source, RH of room
increases
Air change, different
RH from outside
Research this year – Heritage
structures
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University of Seville - Jacinto Canivell
Pan- European – New Integrated
Knowledge Based Approaches to the
protection of cultural heritage from
Earthquake induced Risk (NIKER)
The way forward
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Recent posters by UN Habitat Long way from Eurocodes
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New Zealand has developed
Standards. These should be used by
NGOs when building with earth
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Research such as that presented here
to be integrated into design codes and
allow engineers for NGOs to design
these buildings correctly.
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Eurocode for earth buildings please
Earth building
THANK YOU
PAUL.JAQUIN@RAMBOLL.CO.UK