Building with earth - Gernot MINKE (1)

2.39 Field test to derive
the bond strength of
mud mortar
2.40 Apparatus to test
the resistance against
abrasion, BRL
2.41 Amount of abrasion
of different earth plasters
2.42 Apparatus to measure
the strength of
corners against dynamic
impacts
2.43 Shelter effect of different
building materials
against high-frequency
electromagnetic radiation
Cushioning effect in dB / %
Reduction of high-frequency electromagnetic radiation
60
99.9999%
50
99.999%
40
99.99%
30
99.9%
20
99%
10
90%
mobile network, 900 MHz
GPS satellite navigation
mobile network, 1760 MHz
mobile network, 1950/2150 MHz
radar
radio link system
Frequency in GHz
radio link system
radio link system
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
1 Vegetation roof with 16 cm of substrate, 20 cm
thermal insulation, 24 cm green bricks (earth blocks)
2 Vegetation roof as in 1, without green bricks
Radioactivity
Measurements of the radiation of beta and
gamma rays show that loam has values no
higher on average than concrete or baked
bricks. On the contrary, some bricks tested
by this author exhibited much more radiation,
probably caused by additives like fly
ash or blast furnace slag. Much more important
than the beta and gamma rays are the
alpha rays emitted by the radioactive gas
radon and its short-lived decay products.
The “soft” rays cannot penetrate the human
body as they are absorbed by the skin, but
can be inhaled by breathing and, therefore,
may cause lung cancer. The following table
shows the exhalation rate of radon given
by the OECD (1979) for Germany, measured
in m becquerel/kg h.
Natural gypsum 25.2
Cement
57.6
Sand
54.0
Baked clay bricks 5.0
Lime-sand bricks 13.3
Porous concrete 18.0
3 24 cm green bricks (1,600 kg/m 3 , 15 cm loam plaster)
4 2 cm lime plaster, 25 cm lightweight loam (800 kg/m 3 ),
1.5 cm lime plaster
5 10 cm lightweight loam block (1,400 kg/m 3 )
6 17.5 cm porous concrete (500 kg/m 3 )
7 24 cm hollow bricks (1,200 kg/m 3 )
This shows that a clay brick from a clayey
soil discharges very little radon.
2.41
Samples
2.43
Abrasion in g
0.5 1.0 1.5 2.0 2.5 3.0 3.5
8 24 cm lime-sand-stone (1,800 kg/m 3 )
9 1.3 cm tile
10 aluminium sunshade element
11 metal insect grid (1x1 mm mash)
12 double glazing, gold film covered
pH-value
Shelter against high-frequency electromagnetic
radiation
Illustration 2.43 shows the differing degrees
of effectiveness of solid building materials in
screening (reducing) high-frequency electromagnetic
radiation, as measured at the University
of the Federal Armed Forces at
Loam mortars
0.2
0.1
0.1
0.0
0.7
0.3
1.3
1.5
2.5
3.2
Clayey soil is usually basic, with pH-values
between 7 and 8.5. Nowadays, due to acid
rain, earth dug from industrial areas may be
slightly acidic just below the topsoil. The
basic state usually prevents fungus growth
(the favourable pH-value for fungus usually
lies between 6.5 and 4.5).
Munich.
In the area of 2 gigahertz frequencies at
which most cellular (mobile) phones are
working, a 24-cm-thick mud brick wall
creates a reduction of 24 dB (decibels),
whereas an equal tick wall of a lime-sand
stone only absorbs 7 dB.
0.3
0.5
2.3
2.4
0.3
35
Properties of earth