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European Journal of Applied Sciences – Vol. 10, No. 4
Publication Date: August 25, 2022
DOI:10.14738/aivp.104.12617. Gouafo, C., Keyangue Tchouata, J. H., Barthelemy, N., Djousse Kanouo, B. M., & Mathurin, M. Z. G. (2022). Litho Stabilization of Silty
Sands by Crushed Basalt Stones for Their Use in the Base Layers of Pavements. European Journal of Applied Sciences, 10(4). 111-
135.
Services for Science and Education – United Kingdom
Litho Stabilization of Silty Sands by Crushed Basalt Stones for
Their Use in the Base Layers of Pavements
Gouafo Casimir
University of Dschang Cameroon
Keyangue Tchouata Jules Hermann
University of Gaoundere Cameroon
Ndongo Barthelemy
University of Dschang Cameroon
Boris Merlain Djousse Kanouo
University of Dschang Cameroon
M. Zoyem Gouafo Mathurin
University of Dschang Cameroon
ABSTRACT
This study shows the improvement of the clayey sand of Maka in center Cameroon.
This improvement is made with crushed basalt stone of class 0/31.5 mm, for its use
in road construction according to the CEBTP of standard. The validation of this litho
stabilization method was carried out in determining the plastic index, the optimum
water content, the dry densities and the CBR index of the various mixtures. The
results of the mixtures made in the laboratory with the choices of the following
percentages: 90% silt sand + 10% crushed basalt stones, 85% silt sand + 15%
crushed basalt stones, 80% silt sand + 20% of basalt crushed stone and 70% silt
sand + 30% crushed basalt stones meets the criteria of the Practical Guide to
Pavement Design for Tropical Countries (CEBTP) for the base course of flexible
pavements. In fact CBR at 95% OPM has increased from 23% for loamy sand to 47%;
55%; 58% and 64% respectively for the same mixtures. Optimal Proctor water
content decreased from 10.1% for silty sand to 10.08%; 10%; 9.60% and 8.0 %
respectively for the same mixtures. The plastic index went from 9.8 % for silty sand
to 9.6 %; 9.4 %; 8.9 % and 5.8 % respectively for the same mixtures, these values
above indicates weakly clayey mixtures according to Guide of road earthworks
(GTR). Moreover, we were able to observe that the granulometric curves of the
mixtures of clayey sands with basaltic gravels extend beyond the reference
spindles. These mixtures cannot be used as a base course for rigid pavements.
Stabilization must be improved with at least 1% cement for rigid pavements. The
increase in dry density from 1.75 to 2.024, more than compensates for the relative
loss of optimal water content and thus allows the mixture to have a better bearing
capacity for compaction than non-silt sand improved, all these properties are
greater than those of natural clay sand. This confirms that the addition of crushed
basalt makes clayey sand more rigid and dense.
Key words: Litho stabilization, Base layer, pavement, CBR index, silty sand.
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European Journal of Applied Sciences (EJAS) Vol. 10, Issue 4, August-2022
Services for Science and Education – United Kingdom
INTRODUCTION
Silty sands have long been used as base course materials in road networks. But nowadays, given
the population explosion, the road infrastructure is very much in demand due to the increase
in traffic. It becomes essential to stabilize these soils. We are going to study the litho- stabilization of silty clay using crushed basalt aggregates 0/31.5 mm. It is a technique that
stabilizes loose or less compact soils by adding more rigid materials. The principle consists in
improving a soil by iteration, by adding a proportion of crushed stone or other more structured
material, then subjecting it to tests in order to determine the new geotechnical properties. It
was the subject of a study for the first time for Trenter and Thomas.(2001). [2] as part of the
Ouagadougou-Yako road development project. Then Thilloux and R. Requirand. (1983) [3] also
report the execution works of the pavements of the Tabou-Arlit road in Niger where crushed
stones were widely used. In Chad, litho-stabilization was used for the first time due to the low
bearing capacity of silty sand, materials frequently used as a base layer in Ndjamena, and the
surrounding area over a radius of 100 km. [4]evaluated the performance of a lateritic soil,
through the modification of the grain size by the insertion of sand from 0 to 45%. Several
studies have attempted to find a method to improve the properties of bar soil by adding other
locally available slightly coarser granular materials. Other materials used are sand, crushed
concrete and rubble [5]. Cabalar and W. S. Mustafa.(2017) [6] studied the behavior of sand-clay
mixtures for pavement subsoils. Test results showed an increase in CBR values with an increase
in the amount of sand. Niangoran et al.(2020) [7] studied the improvement of a natural lateritic
gravel by adding crushed stone to the gravel which improved the geotechnical properties of
this material. Babaliye et al. (2020) [8] carried out the litho stabilization of lateritic gravels by
crushed granite for their use in flexible pavement in Benin, all their properties were larger than
those of natural laterite except the cohesion of the crushed mixture at 40% . This confirmed
that the addition of crushed stone makes the laterite stiff and dense. [9] studied the lateritic
materials used in road construction in Niger by litho stabilization. They used nodules from
these lateritic soils taken in situ. This technique has improved the geotechnical properties of
this material. For pavement base layers, the material used must meet the following
specifications according to [10]: the index carrying CBR at 95% equals 40 and CBR at 98%
equals 80% at least after 4 days of soaking. The technical specification recommends a plastic
index less than 15; a percentage of fines less than or equal to 25; and a dry density OPM greater
or equal to 2.1.
The objective of this study is to find the best combinations of silty sands with crushed basalt
stones 0/31.5 mm, giving the best properties. Figure 1 shows what silty sand looks like.
Figure 1: Silty Sand
METHODOLOGY
Identification tests consist in determining the physical and mechanical properties of a material.
Particle size analysis, Atterberg limits, modified Proctor and CBR tests will be performed.
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Gouafo, C., Keyangue Tchouata, J. H., Barthelemy, N., Djousse Kanouo, B. M., & Mathurin, M. Z. G. (2022). Litho Stabilization of Silty Sands by
Crushed Basalt Stones for Their Use in the Base Layers of Pavements. European Journal of Applied Sciences, 10(4). 111-135.
URL: http://dx.doi.org/10.14738/aivp.104.12617
Furthermore, it should be noted that these tests are carried out on a representative sample of
the material concerned. Thus, to obtain such a sample, it is necessary to proceed by sampling
according NF P18-553 standard [11]. For this research we proceeded by quarter.
• Water content
The water content was determined according to NF P94-050 standard [12], using the formula
(1)
Where Pw is the weight of water in N; Ps the weight of the dry matter in N and W% the water
content.
• Modified Proctor test
The purpose of the Proctor test is to determine for a given compaction intensity the water
content to which the soil must be compacted to obtain maximum dry density,the test was
carried out according to NT P 94-093 [13].
• Granularity
Particle size analysis was done according to NF EN 933-1 and NF 94-056 [14], [15] and the
finesses modulus was determined used NFP 18-540 standard.
Fineness Modulus according to NF P18-540 [16].
• CBR index
According to NF P 94-078 [17], the Californian Bearing Ratio or CBR index, makes it possible to
define road soils used as purely empirical index, thanks to which one can therefore calculate
using charts the thickness of pavement layers as a function of loads and expected traffic. The
CBR is determined at 2.5 mm and 5 mm penetration into the sample from the punch probe.
(2)
(3)
Where IP5mm and IP2.5mm are respectively the CBR index at 5 mm and 2.5 mm of penetration into
the sample of the punching probe; F5mm and F2.5mm the respective values in KN of the
corresponding forces. The CBR index is the greatest value.
• Atterberg limits
The Atterberg limits consist of plastic and liquid limit. Which were respectively determined
used NF P 94-051 [18] and Casagrande method. Then, the plastic index was calculated using
the formula �� = WL − Wp (4)
The water content variation curve as a function of the number of strokes is therefore:
� = f(N) (5)
*100 % Pw W
Ps =
100* 5 5
70
F mm IP mm =
100* 2.5 2.5
105
F mm IP mm =
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European Journal of Applied Sciences (EJAS) Vol. 10, Issue 4, August-2022
Services for Science and Education – United Kingdom
RESULTS AND DISCUSSIONS
Location
Administratively, the district of Maka is located in Cameroon, Sanaga Maritime Department in
the Littoral Region. Figure 2 below locates the locality of Maka where the samples were taken
for the research.
Figure 2: Location of the localities of Maka in Cameroon Littoral Region, Sanaga Maritime
Department
Summary of the results of the identification and load-bearing tests
Results of tests on unimproved silt sand
The clayey sand from this Maka quarry has been used on several occasions to execute the base
course of roads in Cameroon. The results of the identification tests carried out on a sample
taken from this site are summarized in the table1 below:
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Gouafo, C., Keyangue Tchouata, J. H., Barthelemy, N., Djousse Kanouo, B. M., & Mathurin, M. Z. G. (2022). Litho Stabilization of Silty Sands by
Crushed Basalt Stones for Their Use in the Base Layers of Pavements. European Journal of Applied Sciences, 10(4). 111-135.
URL: http://dx.doi.org/10.14738/aivp.104.12617
Table 1: Results of test on silt sand sample from Maka quarries: Granulometry, Atterberg
Limits, Proctor and CBR at 95 % OPM
Nature Granulometry = % passing through the sieve of Atterberg
Limits
Proctor CBR
at
95
%
OPM
0.08 0.5 1 2 5 10 20 31.5 WL Wp Ip d Wopm
Sample 26.4 98.3 98.8 99.7 100 100 100 100 26 16.2 9.6 1.75 10.1 23
Legend: CBR = Californian bearing ratio; OPM = Modified Optimum Proctor; WL = liquidity limit
;WP = plastic limit ;IP= plasticity index
Figure 3: Particle size curves of the unimproved silt sand of Maka not inscribed in the standard
spindle recommended by the CEBTP [10] as a base layer
This material is not efficient for road works, in fact: in its grain size, the elements are not
distributed continuously, from fines of 0.08 mm sieve to pebbles of 31.5 mm sieve (100 %). The
material need stabilization, in the context of this study is a mixture of silty sand with crushed
stones at different percentages.
Results of tests on crushed basalt stones
The crushed basalt stones used for this research were 0/31.5 mm. It is gravel resulting from
the crushing basalt stones. The results of the identification tests are shown in (Table 2 and
figure 2):
0
10
20
30
40
50
60
70
80
90
100
100 10 1 0.1 0.01 0.001
% Passing
Openings of the sieve in (mm)
Pebbles Gravels Sand Silt
Clay
silt sand of
Maka
upper curve
of the
standard
spindle
Lower curve
of the
standard
spindle
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European Journal of Applied Sciences (EJAS) Vol. 10, Issue 4, August-2022
Services for Science and Education – United Kingdom
Table 2: Identification tests for crushed basalt stones 0/31.5 mm
Nature Granulometry = % passing through the sieve of Los Angeles Trials
0.08 0.5 1 2 5 10 20 31.5 19.6
Gravel
crushed
to 0/31.5
mm
7 12 21 29 38 63 97,5 98
Figure 4: Particle size curves of the crushed Basalt stones very well inscribed in the typical
spindle recommended by the CEBTP [10] as a foundation layer
This material is one of the most efficient for road works, in fact: in its grain size, the elements
are distributed continuously, from fines of 0.08 mm sieve (7%) to pebbles of 31.5 mm sieve
(98%) (Figure 4). This material will play a great role in strengthening and improving the
structure of silty sands on the pavement base layer, it is an excellent road material.
Results of tests of improved silt sand with differents percentage of crushed Basalt stones
The litho stabilization in the context of this study is a mixture of silty sand with crushed Basalt
stones at different percentages. The basic principle of material mixtures is the Dreux-Gorisse
factor, based on dividing lines; but this factor is only effective if the smallest material arrives at
the 5.0 mm sieve, but our silty sand only arrives at the 2.0mm sieve. We therefore proceeded in
the laboratory to a choice of percentages so the values vary from: 90 % silt sand + 10% of basalt
crushed stones, 85 % silt sand + 15% of basalt crushed stones, 80 % silt sand + 20% of basalt
crushed stones and 70 % silt sand + 30% of basalt crushed stones. At less than 10 %, the litho- stabilization of crushed stone with sand no longer has any basis because the results obtained
are closer to sands; at more than 30 %, stabilization loses its purpose because the values
obtained are those of crushed aggregate.The contents of the tests and the results obtained on
the various mixtures are presented in the (table 3 and figure 5).
0
10
20
30
40
50
60
70
80
90
100
100 10 1 0.1 0.01 0.001
Passers in%
Openings of the sieve in mm
Pebbles Gravel Sand
Silt Clay
Upper
curve of
the...
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Gouafo, C., Keyangue Tchouata, J. H., Barthelemy, N., Djousse Kanouo, B. M., & Mathurin, M. Z. G. (2022). Litho Stabilization of Silty Sands by
Crushed Basalt Stones for Their Use in the Base Layers of Pavements. European Journal of Applied Sciences, 10(4). 111-135.
URL: http://dx.doi.org/10.14738/aivp.104.12617
Table 3: Stabilization of silt sand with differents percentage of crushed stone: Atterberg Limits;
Proctor ; CBR at 95 % OPM and CBR at 98 % OPM
Nature Atterberg Limits Proctor CBR at
95 %
OPM
CBR at
98 %
OPM
WL Wp Ip dma
x
WOPM
100 % silt sand + 0% of basalt crushed
stones
26 16.2 9.8 1.75 10.1 23 43
90 % silt sand + 10% of basalt crushed
stones
25 15.4 9.6 1.90
4
10.0
8
47 56
85 % silt sand + 15% of basalt crushed
stones
25.
7
15.6 9.4 1.91
2
10 55 70
80 % silt sand + 20% of basalt crushed
stones
25.
6
16.7 8.9
0
1.94 9.60 58 88
70 % silt sand + 30% of basalt crushed
stones
24.
2
18.4 5.8
0
2.02
4
8.00 64 100
Legend : CBR = Californian bearing ratio; OPM = Modified Optimum Proctor; WL = liquidity limit
;WP = plastic limit ;IP= plastic index, dmax = Dry density; WOPM =Water content at Modified
Optimum Proctor
Figure 5: Particle size curves of Litho stabilization of silt sand with different percentages of
crushed basalt stones are not inscribed in the standard spindle recommended by the CEBTP
[10] as a base layer
The Percent of fines (passing 0.08 mm sieve) decreased from 26.43% for silty sand to 18.8 %;
14.4 %; 13.8 % and 12.6 % respectively (figure 5), for the mixtures at 90 % silt sand + 10% of
basalt crushed stones, 85 % silt sand + 15% of basalt crushed stones, 80 % silt sand + 20% of
basalt crushed stones and 70 % silt sand + 30% of basalt crushed stones. Similar variations
were observed for the other grain sizes. Californian bearing ratio at 95 % Modified Optimum
Proctor (CBR at 95 % OPM) increased from 23 for silty sand to 47; 55; 58 and 64 respectively
for same mixtures, these meets the criteria of the Practical guide to pavement design in tropical
countries [10] for the base course of flexible pavements. The growth of the CBR index indicates
the growth of the bearing capacity of the soil, with the increase in the percentage of gravels in
the clayey sand. The dry density increased from 1.75 for the silty sand to 1.904; 1.912; 1.94 and
2.024 respectively for same mixtures. The improvement of the clayey sand is expressed by this
increase in the dry density of the mixture, so it is more favorable. The water content at the
optimum proctor decreased from 10.1 for silty sand to 10.08; 10; 9.60 and 8.0 respectively for
same mixtures. The plastic index decreased from 9.8 % for the silty sand to 9.6; 9.4; 8.9 and 5.8
0
10
20
30
40
50
60
70
80
90
100
100 10 1 0.1 0.01 0.001
Passers in%
Openings of the sieve in mm
Pebbles Gravel Sand Silt
Clay Upper
curve of
the
standard
spindle
Basalt
crushed
stones
curve