Smeu, S. et al / Journal of Environment (2014), Vol. 03, Issue 03, pp. 47-50
ISSN 2049-8373
Research Review
Environmental Friendly Building Materials:
Unfired Clay Bricks
Silvia Smeu*, Andrei Gal and Cătălin Badea†
Dept. of Civil, Industrial & Agri. Buildings, Faculty of Civil Eng. Politehnica Uni. of Timisoara, Timisoara, Romania
*E-Mail: [email protected], †E-Mail: [email protected]
Abstract
The continuous search for affordable and environmental friendly housing, led to investigations into new building masonry
materials. Clay is a natural resource of the planet and one of the most common and has been recently “rediscovered” as an
ecologically sound and healthy building material. Due to problems with shrinkage and swelling of clays and changes in
material properties, we tried to stabilize the mixtures realized with clay using cement, lime and sand as binder, and we also
added sawdust in each batch made. The tests that we made were concerning: apparent density, bending tensile strength and
compressive strength. By using clay and sawdust in this “rediscovered” building material, results a good impact on
environment. The values obtained for compressive strength were within the acceptable standards for clay masonry units.
Keywords: Unfired Clay Bricks, Building Materials, Thermal Insulation, Environmental Friendly
1. Introduction
Clay is one of the most abundant natural resources of
Earth. Since early times, it has provided human beings
with a very useful building material (Oxburgh, 2002 and
Badea et al, 2014). Almost third of the world’s inhabitants
live in houses made of soil. Since the 1980s, environmental considerations became increasingly important throughout Europe as well as internationally. Earth has been “rediscovered” as an ecologically sound and healthy building
material (Schreckenbach, 2004).
The shortage of affordable housing has lead to many
investigations into new building masonry materials. Fired
clay masonry bricks are conventionally used for masonry
wall construction but suffer from the rising price of energy
plus other related environmental problems such as high
energy usage and carbon dioxide. The use of stabilised unfired clay bricks for masonry construction may solve these
problems (Oti et al, 2009a). Sun-baked clay bricks are one
of the earliest basic building materials used by mankind
and are still used today. This is thanks to their simplicity
and low cost, good thermal and acoustic proper-ties, and at
the end of a building’s life, the clay material can be reused
by grinding, wetting or returned to the ground without any
interference with the environment. However, the main problem of sun-baked bricks is its susceptibility to water damage. This deficiency is overcome in our days by stabilising
the clay soil with the addition of cement and lime, thereby
producing an improved construction material (Kinuthia &
Wild, 2001; Mckinley et al, 2001; Rao & Shivananda,
2005 and Oti et al, 2009b).
The two principle problems that we are dealing with are
shrinkage and swelling of clays and changes in material
properties. Volume change in clays can be significant and
occur as the moisture content changes (Prusinski & Bhattacharja, 1999).
2. Experimental Programme
In this study, experimental determinations were made on
building materials realized from clay mixed with cement
(C), lime (L), sand (S) and sawdust (SD). We tried to stabilize the mixtures with clay using cement and lime as
binder (Badea, 2004).
The cement (C) used is a Romanian product, type CEM I
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Smeu, S. et al / Journal of Environment (2014), Vol. 03, Issue 03, pp.
ISSN 2049-8373
52.5 R (Carpat Cement Holding).
The soil used is from Timis County, Romania, from a 1.00
m depth. The sawdust (SD) was a wood furniture industry
waste from Hunedoara County, Romania.
Different mixtures were realized with the following compositions:
Batch 1:
- Water: 25%
- Dry Material:=75%
1) Cement: 10%
2) Sawdust: 5%
3) Clay: 85%
Figure 1. Sawdust.
The cement (C) was 10% and 5%, lime (L) was 15% and
5%, sand (S) was 10% and sawdust (SD) was 2.5% and
5% as we considered for each series so we can obtain good
results for bricks made with clay to be used in loadbearing
walls.
Batch 2:
- Water: 25%
- Dry Material: =75%
Table 1. Materials Composition
1) Lime: 15%
2) Sawdust: 5%
3) Clay: 80%
Batch
Batch 3:
Series 1
C10
SD5
Series 2
L15
SD5
Series 3
L15 S10
SD5
Series 4
C5 L5
SD2,5
- Water: 25%
- Dry Material:=75%
1)
2)
3)
4)
Lime: 15%
Sawdust: 5%
Sand: 10%
Clay: 70%
Batch 4:
- Water: 15%
- Dry material:=85%
1)
2)
3)
4)
Dry Material (%)
Water
(%) Cement Lime Sawdust Sand Clay
25
10
0
5
0
85
25
0
15
5
0
80
25
0
15
5
10
70
15
5
5
2.5
0
87.5
The materials compositions can be seen in Table 1.
Cement: 5%
Lime: 5%
Sawdust: 2.5%
Clay: 87.5%
Prismatic samples were made with 40x40x160 mm dimensions.
The dimensions of the sawdust used are given in Figure 1.
To establish the blended binders compositions, the next
model was used (Badea et al, 2008 and 2010):
The samples were realized in three steps:
First we combined the water with the binder (cement or
lime, or both), for the 3rd Series we added to the binder in
this phase sand
%ΣDry materials=%Σ(classic binders+clay +SD)=100%
Where:
-Classic mineral binders=cement (C); lime (L); sand (S)
-SD= Sawdust
-Clay= Soil from -1.00 m depth
Secondly, clay was added, the mixture was mixed manually 30 seconds
Thirdly, sawdust was added and the mixture was mechanically mixed for 60 seconds.
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Smeu, S. et al / Journal of Environment (2014), Vol. 03, Issue 03, pp.
The compacting was performed manually as follows: 30
jolts in 30 seconds for all fresh material quantity. The
samples were kept in natural conditions until 7 and 28 days
age, respectively.
ρ a [kg/m3]
ISSN 2049-8373
Apparent density
1467
1500
1390
1323
1318
1259
1200
1215
1132
1108
Legend:
7 days
900
3. Results and Discussion
28 days
The values obtained for apparent density, bending tensile
strength and compression strength at 7 days age and at 28
days age are represented in Table 2.
600
300
0
Table 2. Physical and Mechanical Characteristics of Hardened Mixtures
10%
Series 1 C10SD5
15%
Series 2 L15SD5
25%
Series 3
L15S10SD5
10%
Series 4
C5L5SD2.5
Σ(L+C)
BATCH
Figure 2. Apparent Density
No.
Batch
Apparent
Density
ρa, (kg/m3)
Bending Tensile Compressive
Strength,
Strength,
ft, (N/mm2)
fc, (N/mm2)
7 days 28 days 7 days 28 days 7 days 28 days
age
age
age
age
age
age
1.
Series 1
C10 SD5
1323
Series 2
L15 SD5
1259
1132
0.40
0.50
2.19
2.75
Series 2, where we used only lime as a binder had a
significantly and visible shrinkage of the dimensions of the
batches tested: from 160 mm length to 147 mm length at
28 days. This is also a result of the big amount of water
used (25%) that was quickly absorbed into the mixture.
Tensile strength
fcti [N/mm2]
2,46
2,5
2
2.
1108
0.40
2.46
1.25
6.2
Legend:
7 days
1,5
1,27
28 days
1,1
3.
4.
Series 3
L15 S10
SD5
1390
Series 4
C5 L5
SD2,5
1467
1,05
1
1215
1.10
1.27
3.41
0,87
3.64
0,4
0,5
1318
0.87
1.05
4.97
5.17
0,5
0
10%
Series 1 C10SD5
The apparent densities at 28 days age for the batches presented in Table 2 have the values between 1108 kg/m3 and
1318 kg/m3 (Figure 2), which frame the materials in nonloadbearing masonry elements.
0,4
15%
Series 2 L15SD5
25%
10%
Series 3 L15S10SD5 Series 4 C5L5SD2.5
Σ(L+C)
BATCH
Figure 3. Bending Tensile Strength
fc [N/mm2 ]
Compressive strength
7
6,2
6
It can be seen that the bending tensile strengths are increasing at 28 days age compared to those tested at 7 days. The
values at 28 days are between 0.50 N/mm2 and 2.46
N/mm2 (Figure 3). Also the compressive strengths are increasing at 28 days compared with 7 days. They are between
2.75 N/mm2 and 6.2 N/mm2 (Figure 4). We can see a biger increase of the compressive strength when lime is used.
Using cement or lime as binder results in good values for
the bending tensile strength and compressive strength.
Based on the results on the tests made, it can be seen in
Figure 3 and Figure 4 that the bending tensile strengths
and the compressive strengths are increasing from 7 days
age to 28 days age. We can also see that if we use lime as a
binder instead of cement (Series 2), the compressive strengths will increase significantly at 28 days age compared
with Series 1 where we used only cement.
5,17
4,97
5
Legend:
7 days
28 days
4
3,41
3.64
2,75
3
2,19
2
1,25
1
0
10%
Series 1 C10SD5
15%
Series 2 L15SD5
25%
10%
Σ(L+C)
Series 3 L15S10SD5 Series 4 C5L5SD2.5 BATCH
Figure 4. Compressive Strength
Compared with Series 2 that has 15% lime and 5% sawdust from dry material, in Series 3 we added 10% sand to
the same mixture. When we added sand, the compressive
strength and also the bending tensile strength are lower at
28 days age than the values obtained for the bending ten-
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Smeu, S. et al / Journal of Environment (2014), Vol. 03, Issue 03, pp.
ISSN 2049-8373
sile and compressive strengths for Series 2.
181-192.
In Series 4, where we used less water (15%) and tried a better compacting, the apparent density increased and it has
good values for bending tensile and compressive strengths.
Oti, J.E., Kinuthia, J.M., and Bai, J. (2009a) Engineering
properties of unfired clay masonry bricks. Engineering
Geology, 107(3-4), pp. 130-139.
4. Conclusion
Oti, J.E., Kinuthia, J.M., and Bai, J. (2009b) Compressive
strength and microstructural analysis of unfired clay
masonry bricks. Engineering Geology, 109(3-4), pp. 230240.
The Series that have values for the compressive strengths
over 5 N/mm2 at 28 days age (Series 2 and Series 4) can be
used to make unfired clay bricks for loadbearing walls.
The other two Series (Series 1 and Series 3) can be used
for non-loadbearing walls made of unfired bricks.
Acknowledgement
This research was supported by the Laboratory of Materials from the Department of Civil Constructions and Installations of Faculty of Civil Engineering, Timisoara, Romania.
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