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• Paul Jaquin, MEng and PhD at Durham,

now a Civil engineer for Ramboll in Edinburgh

• 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…...

Unsaturated soil and mud bricks• 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 Mud brick home. Pokara ,Nepal

Sandcastles Weston-super-mare beach

Existing research in earth building

• 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

• 1781 - Ironbridge.

• 1824 - Portland Cement developed

• 1884 - Reinforcement using twisted steel.

• 1917 - ASTM develop standard formula for Portland Cement.

• 1992 – 2010 - Eurocodes developed

• International Building Code - United States

• Little mention of earth building

• Little scientific understanding, therefore difficult to develop codes of practice.

Research this year –Materials testing and structural mechanics

• 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

• Visiting research fellow at Bath University

• Continued by Antonio Borges

• Thermal modelling by Celia Macaedo. Oxford Brookes

RH internal = varies

RHexternal = varies

Water vapour flow

RHexternal = 100% RHexternal = variesRHexternal = 50%

RH internal = 50% RH internal = 75% RH internal = 75%

Building construction 100% RH outside,

raining. Water vapour

flow through the wall,

increasing internal

RH

Water vapour flow

Introduce water vapour

source (eg cooking), water

vapour flow through wall,

reducing internal RH

Over time RH of the inside

of the building becomes

constant

Initial conditions, RH

of room and pore air

are equal at 50%

RH = 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

Air change

Water vapour flow

RH = 60%RH= 50%

RH = 50% RH = 70% RH = 70%

Water vapour flow

Remove water vapour

source, RH of room

increases

RH = 60%

Water vapour flow

Air change, different

RH from outside

RH = 50%

RH = 50%

1 2 3 4

Research this year – Heritage structures

• 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

• Recent posters by UN Habitat -

• Long way from Eurocodes

• New Zealand has developed Standards. These should be used by NGOs when building with earth

• Research such as that presented here to be integrated into design codes and allow engineers for NGOs to design these buildings correctly.

• Eurocode for earth buildings please

Earth building

THANK YOU

PAUL.JAQUIN@RAMBOLL.CO.UK