Design of a new soil concrete as an eco-material: Effect of clay and hemp fibers proportions

Journal of Science and Technology in Civil Engineering NUCE 2020. 14 (1): 77–88

DESIGN OF A NEW SOIL CONCRETE AS
AN ECO-MATERIAL: EFFECT OF CLAY AND HEMP
FIBERS PROPORTIONS
Ngo Duc Chinha,∗, Nguyen Ngoc Tanb
a

University of Transport and Communications, 3 Cau Giay road, Dong Da district, Hanoi, Vietnam
b
Faculty of Building and Industrial Construction, National University of Civil Engineering,
55 Giai Phong road, Hai Ba Trung district, Hanoi, Vietnam
Article history:
Received 09/10/2019, Revised 03/11/2019, Accepted 11/11/2019

Abstract
This study presents a series of soil concrete mix that is made of excavated soils, cement, lime and hemp fibers.
An experimental program was carried out on the testing samples of soil concrete with different proportions of
clayey soil and hemp fibers. This program focuses on several properties of soil concrete, such as compressive
strength, autogenous shrinkage, drying shrinkage and water mass loss with time. The obtained results show that
the compressive strength of soil concrete increases even after 28 days, and can be reduced significantly with
increasing the proportion of clayey soil. The effect of clayey soil on the properties tested of soil concrete is
more than that of hemp fibers. In addition, drying shrinkage associated with water mass loss allows to describe
the drying process of soil concrete.
Keywords: soil concrete; hemp fibers; compressive strength; autogenous shrinkage; drying shrinkage; water
mass loss.
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c 2020 National University of Civil Engineering

1. Introduction
The ecological aspect of building structures and the sustainable development is nowadays of high

importance in the construction domain. Therefore, building material containing a proportion of various ecological composition is a good idea. Soil concrete is defined as an ecological building material
since it uses a high content of clayey and sandy soils that are excavated directly at construction sites,
and a small content of binders. The aim of producing ecological concrete is to reduce CO2 emission,
energy consumption in industry by limiting the use of cement and natural resources. For instance,
building made of low cost raw soils represents real interest since the acoustic and thermal properties
of these materials are improved in comparison with ordinary concrete [1]. The stabilization of soil in
concrete can be realized by using different types of binders as lime and cement [2, 3]. The addition of
cement increases the evolution of the mechanical properties of concrete but can induce shrinkage and
cracking [4].
The use of natural fibers as hemp is particularly interesting as it minimizes the volume of waste in
landfill. It is renewable and environmentally friendly [5]. Moreover, hemp is naturally produced, do
∗

Corresponding author. E-mail address: (Chinh, N. D.)

77


Chinh, N. D., Tan, N. N. / Journal of Science and Technology in Civil Engineering

not require much energy to process, do not require maintenance and consumes CO2 to grow, making
the hemp concrete as a carbon negative building material. The addition of hemp fibers can also reduce
the density, shrinkage and cracking of soil concrete and improve the thermal properties [6, 7]. The
acoustic and thermal properties of soil concrete could be better than ordinary concrete, which are
explained by the use of clayey soil and hemp fibers [8].
Concrete volume change is an unavoidable phenomenon, from very early age to long-term behavior [9] and more particularly with soil concrete containing a high proportion of fines aggregates
[10, 11]. Autogenous shrinkage is defined as a concrete volume change occurring without moisture
transfer to the environment. It depends mainly on the composition of concrete and develops more
rapidly with time than drying shrinkage [12]. Drying shrinkage depends on the age of the beginning
of drying and external parameters such as relative humidity and specimen size. Thus, the understanding of shrinkage process and more particularly drying shrinkage, known as the main cause of micro

and macro cracking, is essential.
In this study, the design of soil concrete mix is presented, which made of clayey soil, sandy
soil, hemp fibers, cement and lime. A series of soil concrete mix has been proposed for considering
different proportions of clay soil and hemp fibers. In the laboratory, an experimental program carried
out on the testing samples of soil concrete. The experimental data allow to determine the compressive
strength at 7, 28 and 180 days, autogenous shrinkage, drying shrinkage and water mass loss with time
of soil concrete. The obtained results are also used to evaluate the effect of clayey soil and hemp fibers
on these physical and mechanical properties of soil concrete.
2. Experimental program
2.1. Materials used
In this study, the soil concrete was made of different compositions, such as soil, cement, lime and
hemp fibers. The soils used were excavated at two construction sites in Bordeaux city, France during
the execution of underground. These soils can be classed into two principal types: (a) clayey soil, (b)
sandy soil.
a. Clayey soil
In the laboratory, some tests such as the Atterberg limits, particle-size analysis and the methylene
blue were carried out on the samples in order to determine the type of used clayey soil (Fig. 1)
according to the unified soil classification system in the American standard ASTM D2487-17 [13].
The experimental results are synthesized in Table 1 for the parameters of soil: liquid limit WL ,
plastic limit WP , plasticity index IP , granulometric composition, and VBS that is the methylene blue
value of the total soil. These results show that the used soil can be defined as low plastic clay (CL)
and has a high content of silt particles.
b. Sandy soil
In the laboratory, some tests such as the particle-size analysis, methylene blue, specific density
and fineness modulus were performed on the samples in order to determine the type of used sandy
soil. Fig. 2 presents the sandy soil after grinding by a rubber hammer.
The experimental results are synthesized in Table 2. These results show that the used soil can be
defined as poorly graded sand with gravel according to the unified soil classification system in the
American standard ASTM D2487-17 [13].
78

Chinh, N. D., Tan, N. N. / Journal of Science and Technology in Civil Engineering

Figure 1. Clayey soil after grinding

Figure 2. Sandy soil after grinding

Table 1. Characteristics of used clayey soil

Test

Criterion

Value

USCS* [13]
Low plastic clay (CL)

Atterberg limits (%)

Liquid limit WL
Plastic limit WP
Plasticity index IP

51.74
30.08
21.66

Particle-size analysis (%)

Clay (< 0.002 mm)
Silt (0.002 – 0.06 mm)
Sand (0.06 – 2 mm)
Gravel (> 2 mm)

25.06
55.94
19
0

Methylene blue

VBS

5.72

Lean clay (CL)

*USCS: The Unified Soil Classification System is a soil classification system used in engineering and geology
to describe the texture and grain size of a soil.
Table 2. Characteristics of used sandy soil

Test

Criterion

Value

Particle-size analysis (%)

Silt (0.002 – 0.06 mm)
Sand (0.06 – 2 mm)
Gravel (> 2 mm)
VBS

0.64
72.54
26.82
0.67
2.33
2.57

Blue methylene
Specific density (kg/m3 )
Fineness modulus

USCS* [13]

Sandy soil
Poorly graded sand
with gravel (SP)

c. Hemp fibers
In this study, hemp fibers were used as an additional composition for improving the tensile
strength of soil concrete. The hemp fibers have been often used among the natural fibers with low
price, such as like sisal, jute, rice husk, flax, bamboo, banana fiber, oil palm fiber, sugarcane bagasse,
wood fiber, etc [14]. The diameter of these fibers is less than 2 mm, and the length ranging from 5
79

Chinh, N. D., Tan, N. N. / Journal of Science and Technology in Civil Engineering

to 25 mm. The density of hemp fibers is about 100 kg/m3 in the ambient conditions. The thermal
conductivity is equal to λ = 0.05 W/m.K. The tensile strength varies between 300 and 1100 MPa. The
hemp fibers are highly hydrophilic and can absorb water up to 2.5 times of their mass.
d. Cement
The Portland cement CEM V/A (S-V) 42.5N according to the European standard EN 197-1 was
used as the first binder of soil concrete. This cement has been chosen since it has two important
criterias as clinker ratio and CO2 impact. The compositions of the cement are provided by the manufacturer and presented in Table 3. In the tested soil concrete mixes, the cement content has been used
ranging from 125 to 155 kg/m3 .
Table 3. Composition of cement

Main composition (% by mass)
Cement

Portland clinker

Blast furnace cinder

Fly ash

40 – 64

18 – 30

18 – 30

CEM V/A (S-V)

Additional composition
0–5

e. Lime
In the soil concrete mix, the lime can also be used as the second binder in order to reduce the
cement content. In this study, the pure natural lime named 100 NHL5 according to the European
standard EN 459 was used that has no additives. The specific density of the lime used is 700 kg/m3 .
In the tested soil concrete mixes, the lime content has been used about 40 kg/m3 .
2.2. Soil concrete mix
The design of soil concrete mix aims to increase the clayey soil content while decreasing the
sandy soil content. For this purpose, the clayey soil content was varied from 0%, 20%, 30% and 40%
in the mass total of the soil, named 0A, 20A, 30A and 40A, respectively. For each clayey soil content,
the volume fraction of hemp fibers was mixed ranging 0%, 0.6% and 1.2% in mass, named 0F, 0.6F
and 1.2F, respectively. In this study, 12 soil concrete mixes studied were presented in Table 4. In fact,
when increasing the proportion of clayey soil from 0 to 40%, the cement content can be reduced from
158.1 to 126.6 kg/m3 , meanwhile the water content must increase for the workability in the mixing.
The casting of concrete mixtures has been realized by vibration, as normal concrete, to obtain the
requirement of workability on construction sites. After mixing soil concrete, the consistence was
measured by the slump test and ranging from 65 to 165 mm in function of the proportion of clayey
soil and hemp fibers.
2.3. Compression test
The compression test aims to determine the compressive strength of soil concretes that were
made of different mixes as presented in Table 4. The Young’s modulus of soil concretes can be also
determined from the stress – strain curve. The results of this test can be used to assess the effect of
clay and hemp fibers on the soil concrete compressive strength at the target age.
This test was carried out on the cubic samples with the dimensions of 100×100×100 mm. Fig. 3
shows the compression test that carried out on a typical sample of soil concrete. During the test, four
devices were installed at the center of the lateral faces of each sample, two devices for measuring the
vertical displacement, and two another for measuring the horizontal displacement. The axial load was
applied on the sample with the constant speed of 0.5 mm/minute.

80


Chinh, N. D., Tan, N. N. / Journal of Science and Technology in Civil Engineering

Table 4. Soil concrete mix studied in the laboratory

No

Soil
Clayey soil
concretemix (kg/m3 )

1
2
3
4
5
6
7
8
9
10
11
12

0A0F
0A0.6F
0A1.2F
20A0F

20A0.6F
20A1.2F
30A0F
30A0.6F
30A1.2F
40A0F
40A0.6F
40A1.2F

0.0
0.0
0.0
247.8
241.4
236.6
368.3
356.3
345.3
501.1
476.6
454.4

Sandy soil
(kg/m3 )
1386.8
1306.2
1238.2
991.4
965.7
946.7

859.5
831.5
805.7
751.7
714.9
681.6

Cement Lime
(kg/m3 ) (kg/m3 )
151.8
144.3
138.0
135.6
133.3
131.9
134.4
131.2
128.3
137.1
131.6
126.6

45.0
42.8
40.9
40.2
39.5
39.1
39.9
38.9

38.1
40.7
38.8
37.6

Hemp fibers
(kg/m3 )
0.0
12.0
22.9
0.0
11.1
21.9
0.0
10.9
21.3
0.0
10.9
21.0

Water Slump
(kg/m3 ) (mm)
330.6
314.2
300.6
398.9
392.1
388.0
417.6
407.7

398.7
466.1
447.3
430.5

165
162
157
105
148
95
95
65
140
125
73
105

Figure 3. Compression test on the cubic sample of soil concrete

2.4. Shrinkage and water loss measurements
As soil concrete presents a high volumetric change that can cause the infiltration of water and
impact its durability, the measurements of shrinkage were carried out on the prismatic samples of the
dimensions 40×40×160 mm exposed to controlled ambient conditions with the temperature of 20◦C
and the relative humidity of 60%. All samples were overlaid by a thin plastic sheet at the top of sample
mold during 24 first hours in order to prevent water loss. Then, the samples were demolded, including
two types: (i) uncovered samples for drying shrinkage test and mass loss test (Fig. 4(a)); (ii) covered
samples by self-adhesive aluminum paper for autogenous shrinkage test (Fig. 4(b)).
Fig. 4(c) presents the shrinkage test that was carried out on uncovered samples for determining
the total shrinkage of soil concrete. The longitudinal deformation of each sample is measured by a

displacement device (LVDT). The shrinkage of each sample is calculated by the ratio between the
81


Chinh, N. D., Tan, N. N. / Journal of Science and Technology in Civil Engineering

(a) Uncovered samples of soil concrete

(b) Covered samples of soil concrete

(c) Shrinkage measurement

Figure 4. Shrinkage and mass loss measurements of soil concrete samples

absolute deformation and the length of sample. The shrinkage of each soil concrete is the average
value of three samples. In this study, six soil concrete mixes having three proportions of clayey soil
ranging from 0%, 20% and 40%, and two proportions of hemp fibers of 0% and 1.2% were measured
the shrinkage and mass loss in function of time. There were the total of 36 samples tested. At the
same time, the mass loss was measured on the uncovered samples for a better understanding of drying
shrinkage phenomenon. The measurements of mass loss were performed by the electronic balance
with 0.01 gram readability. The mass loss is calculated in percentage by the ratio between the water
loss mass by evaporation and the initial mass of sample.
3. Results and discussions
3.1. Compressive strength of soil concrete
For each soil concrete mix, three cubic samples with the dimensions of 100×100×100 mm were
tested to determine the average value of the compressive strength, as well as the standard deviation and
the coefficient variation. The experimental results of compressive strength are presented in Figs. 5, 6
and 7 for 12 soil concretes at 7, 28 and 180 days, respectively. In this study, 36 sets of soil concrete
samples were tested.
At 7 days, 12 sets of tested soil concrete samples show that the average values of compressive

strength range from 0.5 to 1.2 MPa (Fig. 5). The compressive strength of soil concrete decreases significantly with increasing the proportion of clayey soil. The effect of hemp fibers on the compressive
strength is only observed for the soil concrete without clayey soil (100% sandy soil). This effect is
negligible for soil concrete having clayey soil.
At 28 days, the average values of soil concrete compressive strength range from 1.0 to 2.4 MPa
(Fig. 6). The same remarks are idenfied on the effect of the proportion of clayey soil and hemp fibers.
The compressive strength can be reduced to 1 MPa with beyond 20% clayey soil. Meanwhile, it can
be reduced from 0.5 to 0.8 MPa with the hemp fibers contents of 0.6 - 1.2%. The effect of hemp fibers
on the compressive strength may be due to the lower density and the modification of the soil concrete
structure and pore distribution by introducing voids and discontinuity.
At 180 days, the compressive strength of soil concrete increases about two times in comparison to
that at 28 days. The average values of compressive strength range from 2.5 to 5.1 MPa (Fig. 7). The
evolution of soil concrete compressive strength occurs in more time in comparison to ordinary concrete that is normally characterized the mechanical properties at 28 days. Fig. 8 shows the evolution
of compressive strength of 12 soil concrete mixes during 180 first days. The obtained results allow
to quantify the effect of curing time on the compressive strength of soil concrete. These results show
82


Compressive strength (M

concrete samples show that the
1.0
concrete average values of compressive
0.8
range from
1.2 MPa of 0.6
mix, three strength
cubic samples
with0.5theto dimensions
0.4
(Figure 5). The

compressive
strength
Chinh,
N. D., Tan,
N. / compressive
Journal of Science and Technology in Civil Engineering
o determine
the average
value
of N.the
Chinh,0.2
N. D., Tan, N. N. / Journal of Science and Technology in Civil Engineering
of
soil
concrete
decreases
that
the
compressive
strength
of
soil
concrete
increases
ard deviation and the coefficient variation. The 0.0 even after one month. This is an important
strengthterm,
can be reduced
to 10 MPa with strength
significantly
with

theshort
mechanical
property
soilincreasing
concrete. In the
the compressive
of soil concrete
is
0.6
1.2
ve strength
are presented
inofFigures
5, 6, 7 for 12
soil20% clayey
Hemp fibers content (%)
beyond
soil.
Meanwhile,
mainly
associated
to
the
cement
hydration.
Meanwhile,
in
the
long
term,

it
may
be
provided
by
the
proportion of clayey soil. The effectit can be reduced from 0.5 to 0.8 MPa
respectively.
In this
study,
36pozzolanic
sets of soil
concrete
hydration
reaction
and the
reactions
between
clay minerals
and calciumstrength
hydroxide
Figure
5. Compressive
offormed
soil
with the hemp
fibers contents
of 0.6 of
hemp
fibers

on
the
compressive
by the cement hydration [15].
1.2%. The effect of hemp concrete
fibers on
at 7 days
strength
is
only
observed
for
the
soil
the compressive strength may be due
1.4
2.8
the lower density and the
0A
20A
30A
40A
0A
20A
30A
40A
d soil
concrete
without
clayey

soil
(100%tomodification
1.2
2.4of the soil concrete
the
sandy
soil). This effect is negligiblestructure and2.0 pore distribution by Figure 7. Compressive strength of soil
1.0
introducing voids and discontinuity.
concrete at 180 days
ssive
for
0.8 soil concrete having clayey soil.
1.6
At 180 days, the compressive strength of soil concrete increases about two times
MPa
0.6
At 28 days, the average valuesin comparison1.2to that at 28 days. The average values of compressive strength range from
0.4
2.5 to 5.1 MPa
0.8(Figure 7). The evolution of soil concrete compressive strength occurs
ength
of soil concrete compressive strengthin more time in comparison to ordinary concrete that is normally characterized the
0.2
0.4
eases
mechanical properties at 28 days. Figure 8 shows the evolution of compressive strength
range
from
1.0

to
2.4
MPa
(Figure
6).
0.0
of 12 soil concrete
0.0 mixes during 180 first days. The obtained results allows to quantify
the
0.6
1.2
0 compressive strength
0.6 of soil concrete.
1.2These results show
the effect of curing time on the
The same0remarks
are
idenfied
on
the
Hemp fibers content (%)
Hemp fibers content (%)
that
the
compressive
strength
of
soil
concrete
increases

even
after
one
month. This is an
ffect
effect of the proportion of clayey soilimportant mechanical
property
of
soil
concrete.
In
the
short
term,
the compressive
Figure
6.
Compressive
strength
of
soil
Figure 5.
strength
of soil concrete
Figure 6. Compressive strength of soil concrete
Figure
5.Compressive
Compressive
strength
of soil

urnal
and
Technology
in
Civil
Engineering
ssiveof Science
strength
of
soil
concrete
is
mainly
associated
to
the
cement
hydration.
Meanwhile, in
and hempconcrete
fibers.
compressive
at 7 days
at 28atdays
concrete
28reaction
daysand the pozzolanic reactions
atThe
7 days
the long term, it may be provided

by the hydration
e soil
between clay minerals and calcium hydroxide formed by the cement hydration [15].
2.8
0A
20A
30A
40A
6.0
00%
6.0
with
0A0F
0A0.6F
0A1.2F
2.4
7
0A
20A
30A
40A
20A0F
20A0.6F 20A1.2F
gible
5.0
while,
5.0
30A0F
30A0.6F 30A1.2F
2.0

40A0F
40A0.6F 40A1.2F
oil.
MPa
4.0
4.0
1.6
0.6 1.2
3.0
3.0
alues
0.8
rs on
2.0
2.0
ength
0.4
e due
1.0
1.0
re 6).
0.0
the
0.0
0
0.6
1.2
0.0
n the
0

0.6content (%)
1.2
Hemp fibers
0
30
60
90
120
150
180
210
crete
Hemp fibers content (%)
Time (day)
y soil
Figure 6. Compressive strength of soil
n by
Figure
8. Evolution
of soil concrete
strength with time
Figure 7.7.Compressive
strength
of soil concrete
Figure
8. Evolution
of soilcompressive
concrete compressive
ssive
Figure

Compressive
concrete
atdays
28strength
days of soil
at 180
strength with time
uity.
concrete at 180 days
6.0

Compressive strength (MPa)

0A

20A

30A

40A

5.0
4.0
3.0

2.0
1.0
0.0

1.2

Compressive strength (MPa)

0.6
Hemp fibers content (%)

Compressive strength (MPa)

(MPa)
strength
Compressive
(MPa)
strength
Compressive

Compressive strength (MPa)

0

8 1.0 to 2.4 MPa at 28
The measured compressive strength of soil concrete is low ranging from

7days
ive strength
ofcompared
soil concrete
increases
aboutThe
two
times

with ordinary
concrete.
range
of compressive strength is acceptable regarding the
application
this kind of concrete
which
is used
as a filling concrete and not for assuring high load
The average
values ofofcompressive
strength
range
from
capacity (e.g. wall, block, etc.). This is due to low cement content, the higher porosity of soil concrete
volution of soil concrete compressive strength occurs
constituted of fine grained mixtures and the higher water content required to achieve an acceptable
ordinary concrete
workability.that is normally characterized the
Figure 8 shows the evolution of compressive strength
3.2. Young’s modulus of soil concrete
180 first days. The obtained results allows to quantify
Fig. 9 shows the typical diagram of stress – strain that presents the relationship between commpressive pressive
strengthstrength
of soiland
concrete.
These results
show deformations of the soil concrete mix named
both longitudinal
and horizontal

oil concrete increases even after one month. This is an
83
of soil concrete. In the short term, the compressive
y associated to the cement hydration. Meanwhile, in
by the hydration reaction and the pozzolanic reactions


3.2. Young’s modulus of soil concrete
Figure 9 shows the typical diagram of stress – strain that presents the relationship
between compressive strength and both longitudinal and horizontal deformations of the
soil concrete mix named 40A1.2F having 40% clayey soil and 1.2% hemp fibers at 7,
Chinh, N. D., Tan, N. N. / Journal of Science and Technology in Civil Engineering
28, and 180 days. Young’s modulus is calculated by the slope of the curve between 10%
40A1.2F
having
clayey
soil and 1.2%
hemp The
fibers
at 7, 28,results
and 180
days.
Young’s
modulus is
and 30%
of 40%
ultimate
compressive
strength.
obtained

show
that
the Young’s
calculated
by the
of the curve
betweenwith
10%aand
30%
of even
ultimate
compressive
The obmodulus
of slope
soil concrete
increases
high
rate
after
28 days. strength.
The elastic
tained results show that the Young’s modulus of soil concrete increases with a high rate even after 28
modulus of tested soil concrete increases from 2 GPa at 7 days to 8 GPa at 180 days.
days. The elastic modulus of tested soil concrete increases from 2 GPa at 7 days to 8 GPa at 180 days.
stress-strain
curves
ofconcrete
soil concrete
a higher
ductility

with increasing
the
The The
stress-strain
curves
of soil
showshow
also aalso
higher
ductility
with increasing
the proportion
proportion
of clayey soil.
Moreover,
the addition
ofreinforcement
hemp fibers asinreinforcement
in soil
of clayey
soil. Moreover,
the addition
of hemp
fibers as
soil concrete can
prevent
horizontal
deformation
during
compression

loading.during compression loading.
concrete
can prevent
horizontal
deformation

Compressive strength (MPa)

3.0
2.5

2.0

7 days
28 days

1.5

180 days

1.0
0.5

0.0
-0.02
-0.01
0.00
Horizontal deformation (%)

0.01

0.02
0.03
Longitudinal deformation (%)

0.04

Figure
9. 9.
Compressive
strength
in function
of longitudinal
and horizontal
deformationsdeformations
of soil concrete
Figure
Compressive
strength
in function
of longitudinal
and horizontal

of soil concrete
3.3. 3.3.
Shrinkage
of soil
Shrinkage
of concrete
soil concrete
Fig. 10 presents the evolution of autogenous shrinkage of soil concrete having 0%, 20%, 40%

Figure 10 presents the evolution of autogenous shrinkage of soil concrete having
clayey soil and 0%, 1.2% hemp fibers during 70 first days. The autogenous shrinkage of soil concrete
0%, 20%,
clayey
soiltheand
hemp
fibers gradually
during 70in first
days.
The Auincreases
with a 40%
high rate
during
three0%,
first1.2%
days and
decreases
function
of time.
autogenous
shrinkage
of soil concrete
increases
withloss
a high
during
three shrinkage
first
togenous
shrinkage

occurs independently
of external
water
and israte
a result
of the
chemical
and decreases
gradually
in of
function
ofintime.
Autogenous
shrinkage
occurs
and days
self-drying
shrinkage. The
reduction
humidity
the pore
system causes
water–air
meniscus
that subjects the pore walls to considerable stress and leads to substantial self-drying shrinkage. The
obtained results show that the autogenous shrinkage
9 of soil concrete without hemp fibers increases
with the proportion of clayey soil. The autogenous shrinkage of soil concrete having 40% clayey soil
and 0% hemp fibers (40A0F) at 67 days increases about four times in comparison with that of soil
concrete having 20% clayey soil (20A0F) and 0% clayey soil (0A0F), 1900 µm/m versus 450 µm/m.

The addition of 1.2% hemp fibers causes a slight increase of autogenous shrinkage for soil concrete
having 20% and 0% clayey soil (20A1.2F and 0A1.2F). However, the autogenous shrinkage of soil
concrete having 40% clayey soil and 1.2% hemp fibers (40A1.2F) decreases significantly in comparison to that of soil concrete having 40% clayey soil and 0% hemp fibers (40A0F). This difference may
be related to the variation of the global porosity between soil concrete mixes and the water absorption
of hemp fibers [16, 17]. The autogenous shrinkage of soil concrete having 1.2% hemps fibers is in
the range of 600 – 800 µm/m.
In general, the drying shrinkage is defined as the contracting of a hardened concrete mixture
due to the loss of capillary water. This shrinkage causes an increase in tensile stress, which may
84


clayey soil and 0% hemp fibers (40A0F). This difference may be related to the variation
of the global porosity between soil concrete mixes and the water absorption of hemp
fibers [16, 17]. The autogenous shrinkage of soil concrete having 1.2% hemps fibers is
in the rangeChinh,
of 600
– 800 µm/m.
N. D., Tan, N. N. / Journal of Science and Technology in Civil Engineering
0A0F

0A1.2F

20A0F

20A1.2F

40A0F

40A1.2F

Autogenous shrinkage (µm/m)

2000
1600
1200
800
400
0
0

10

20

30

40
50
Time (day)

60

70

80

90

Chinh,
N. D., Tan,

N.
N. / of
Journal
of
Science
and
Technology
in Civil
Engineering
Figure 10.
Autogenous
shrinkage
soilofconcrete
with
different
contents
ofcontents
clay
and of
hemp
Figure
10.
Autogenous
shrinkage
soil
concrete
with different
clayfibers
and
hemp fibers

atthe
the drying
beginning
andstructure,
laterisstabilizes
10 and
15 days.
effect
lead increases
to cracking,
deterioration
of concrete
before between
thethe
concrete
is subjected
to
any
kind of
In quickly
general,
shrinkage
defined
as
contracting
of a The
hardened
loading.
Fig.
11

presents
the
evolution
of
drying
shrinkage
of
soil
concrete
having
0%,
20%,
of the proportion
of clayey
the dryingwater.
shrinkage
is significant.
Foranexample,
concrete
mixture due
to the soil
loss on
of capillary
This shrinkage
causes
increasefor
in40%
clayey
and 0%,having
1.2% hemp

fibers
during
70 first
days.
The fibers
drying(40A1.2F)
shrinkage isthe
calculated
by
soilsoilconcrete
40%
clayey
soil and
1.2%
hemp
drying
tensile
stress, which may
lead
to cracking,
deterioration
of concrete
structure, before
the
the subtraction of the autogenous shrinkage from the total shrinkage. The drying shrinkage of soil
shrinkageisreach
a high any
value
about
11800 µm/m,

corresponding
to approximately
8
concrete
subjected
kind
of loading.
Figure
11
presents
of drying
concrete
increases
quickly to
at the beginning
and later
stabilizes
betweenthe
10evolution
and 15 days.
The effect
times
higher
than
that
of
soil
concrete
having
0%

clayey
soil
(0A1.2F
and
0A0F).
The
shrinkage
of of
soil
concrete
having
0%, 20%,
40% is
clayey
soil and
1.2% hemp
of the
proportion
clayey
soil on
the drying
shrinkage
significant.
For0%,
example,
for soilfibers
concrete
effect
of
hemp

fibers
on
the
drying
shrinkage
depends
also
on
the
proportion
having
40% 70
clayey
and The
1.2%drying
hemp fibers
(40A1.2F)
the drying
reachofa clayey
highthevalue
during
firstsoil
days.
shrinkage
is calculated
byshrinkage
the subtraction
of
soil
in the

ofshrinkage
soil
concrete
In
fact,
the drying
shrinkage
increases
for
aboutautogenous
11800
µm/m,
corresponding
to approximately
8 times
higher than
that ofsignificantly
soil
concrete
having
frommix.
the
total
shrinkage.
The
drying
shrinkage
of
soil
concrete

0% clayey
soil (0A1.2F
and 0A0F).
The effectwith
of hemp
on the
drying40%
shrinkage
soil concrete
of 40A1.2F
in comparison
that fibers
of 40A0F
having
clayeydepends
soil andalso
on the
of clayey
soil in
concrete mix.
In fact,
the drying
shrinkage
increases
0%proportion
hemp fibers.
This may
bethe
dueoftosoil
modification

in pore
system
structure
and transfer
significantly for soil concrete of 40A1.2F in comparison
that of 40A0F having 40% clayey soil
10 at thewith
properties that modify the water evaporation
surface of soil concrete.
0A0F

0A1.2F

20A0F

20A1.2F

40A0F

40A1.2F

Drying shrinkage (µm/m)

12000
10000
8000
6000
4000

2000

0
0

10

20

30

40
50
Time (day)

60

70

80

90

Figure
Drying shrinkage
shrinkage ofofsoil
concrete
withwith
different
contents
of clay and
hempand

fibers
Figure
11.11.Drying
soil
concrete
different
contents
of clay
hemp
fibers

3.4. Water mass loss

85

The water mass loss of soil concrete was also measured at the same time of the
measurement of drying shrinkage. The obtained results are presented in Figure 12 for


Chinh, N. D., Tan, N. N. / Journal of Science and Technology in Civil Engineering

and 0% hemp fibers. This may be due to modification in pore system structure and transfer properties
that modify the water evaporation at the surface of soil concrete.
3.4. Water mass loss
The water mass loss of soil concrete was also measured at the same time of the measurement
of drying shrinkage. The obtained results are presented in Fig. 12 for soil concrete with 0%, 20%,
40% clayey soil and 0%, 1.2% hemp fibers. The variation of water mass loss transcribes the diffusion
capacity of the material. The mass loss is important during 15 first days and later stabilizes. The
water mass loss with time shows similar trend as the drying shrinkage. The water mass loss increases
when rising the proportion of clayey soil, which could explain the increase of drying shrinkage. The

addition of hemp fibers causes the increase of the water mass loss for soil concrete having 0% and
20% clayey soil
(0A1.2F
Meanwhile,
causes
the decrease
the water mass loss for
Chinh,
N. D.,and
Tan,20A1.2F).
N. N. / Journal
of Scienceitand
Technology
in CivilofEngineering
soil concrete having 40% clayey soil (40A1.2F).
0A0F

0A1.2F

20A0F

20A1.2F

40A0F

40A1.2F

25

Mass loss (%)

20
15
10
5
0

0

10

20

30

40
50
Time (day)

60

70

80

90

Figure
12.12.
Evolution

massloss
lossofof
concrete
Figure
Evolutionof
of water
water mass
soilsoil
concrete
Drying shrinkage deformation (µm/m)

The water mass loss has 0A0F
a good 0A1.2F
correlation
with the
drying shrinkage
of tested soil concretes.
20A0F
20A1.2F
40A0F 40A1.2F
Fig. 13 presents the
relationship between these two parameters for six tested soil concrete mixes.
12000
There are some phases that can be distinguished in Fig. 13. In the first phase called “dormant zone”,
10000
the water loss without
shrinkage is observed on the tested samples of soil concrete. In fact, the water
content gradient in soil concrete due to drying generates a stress gradient, so a high tensile stress at
8000
the sample surfaces exposed to the atmosphere and causes cracks. The surface area to volume ratio is

an important factor 6000
in this phase. During the second phase, the gradients become more pronounced,
the cracks at the surface remains unchanged. The drying shrinkage is proportional to water mass
loss (linear zone), with
4000 a slope that reflects the fineness of the porous network. In the last phase,
a stabilisation phase is observed with a lower shrinkage rate. Soil concrete shrinkage is higher in
2000 concrete due to the lack of coarse aggregates that inhibit the total shrinkage
comparison to ordinary
and the higher porosity related to incorporating clayey soil and high water content.
0

0

5

10
15
Mass loss (%)

20

25

Figure 13. Correlation between drying shrinkage and water mass loss of soil concrete
86
The water mass loss has a good correlation with the drying shrinkage of tested
soil concretes. Figure 13 presents the relationship between these two parameters for six
tested soil concrete mixes. There are some phases that can be distinguished in Figure

0

0

10

20

30

40
50
Time (day)

60

70

80

90

Figure 12. Evolution of water mass loss of soil concrete
Drying shrinkage deformation (µm/m)

Chinh, N. D., Tan, N. N. / Journal of Science and Technology in Civil Engineering

0A0F

0A1.2F

20A0F

20A1.2F

40A0F

40A1.2F

12000
10000
8000
6000
4000
2000
0

0

5

10
15
Mass loss (%)

20

25

13. Correlation between drying shrinkage and water mass loss of soil concrete

FigureFigure
13. Correlation
between drying shrinkage and water mass loss of soil concrete

The water mass loss has a good correlation with the drying shrinkage of tested
4. Conclusions
soil concretes. Figure 13 presents the relationship between these two parameters for six
The
present
study aims
to consider
series
of phases
soil concrete
mixes
with different in
proportions
tested
soil concrete
mixes.
There aare
some
that can
be distinguished
Figure of
clayey
soil
(0%,
20%,
30%,

40%)
and
hemp
fibers
(0%,
0.6%,
1.2%).
The
experimental
results
13. In the first phase called “dormant zone”, the water loss without shrinkage is observedallow
to evaluate
the effect
of clayey
soilconcrete.
and hempInfibers
physicalgradient
and mechanical
properties of
on the tested
samples
of soil
fact, on
theseveral
water content
in soil concrete
soil concrete, such as compressive strength, Young’s modulus, autogenous shrinkage, drying shrinkdue to drying generates a stress gradient, so a high tensile stress at the sample surfaces
age and water mass loss.
exposed
thetheatmosphere

causes
The surface
area1.0
to to
volume
ratio
an and
For
tested to
mix,
compressiveand
strength
of cracks.
soil concrete
ranges from
2.4 MPa
at 28isdays
important
factor
this phase.
During
second
phase,
the2.5
gradients
become
increases
even after
oneinmonth
with the

averagethe
values
ranging
from
to 5.1 MPa
at 180more
days. The
results
show that the
strength
of soil
concrete
decreases when
increasing
the proportion
pronounced,
thecompressive
cracks at the
surface
remains
unchanged.
The drying
shrinkage
is
of clayey
soil
and
hemp
fibers,
which

could
be
related
to
increasing
concrete
porosity.
The
proportional to water mass loss (linear zone), with a slope that reflects the fineness ofeffect
of clayey soil is higher than hemp fibers. The hemp fibers cause a slight reduction of compressive
strength that is due to lower density and modification of soil concrete structure and pore system by
12
introducing voids and discontinuity.
The soil concrete deformation due to autogenous and drying shrinkage increases significantly
when rising the proportion of clayey soil, especially with the use of 40% clayey soil of the total mass
of soils used. The drying shrinkage increases reaches important value for soil concrete having 40%
clayey soil, which corresponds to about 8 times higher than that without clayey soil. The addition of
1.2% hemp fibers influences slightly the shrinkage of soil concrete that has less than 20% clayey soil.
Meanwhile, it causes a significant increase of drying shrinkage for soil concrete having 40% clayey
soil. Thus, the obtained results show that it recommends to use less than 40% clayey soil and 1.2%
hemps fibers in order to design the soil concrete mix as a building material.
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