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Research Article
The Effect of Organic and Inorganic Modifiers on the Physical
Properties of Granite Residual Soil
Bingxiang Yuan , Weijie Chen, Jin Zhao, Fei Yang , Qingzi Luo, and Tianying Chen
School of Civil and Transportation Engineering, Guangdong University of Technology, Guangzhou 510006, China
Correspondence should be addressed to Fei Yang; 1875104541@qq.com
Received 28 January 2022; Accepted 18 April 2022; Published 30 April 2022
Academic Editor: Qian Chen
Copyright ©2022 Bingxiang Yuan et al. is is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is
properly cited.
As a kind of highly weathered special soil in South China, granite residual soils (GRS) feature high strength and high void ratio in a
dry environment, so they tend to disintegrate in water and cause geological disasters including collapse. erefore, modifying GRS
for higher strength has become a hot spot. Glass fiber reinforced soils boast fewer cracks, higher energy absorption, and residual
strength. is study aims to analyze the reinforcement effect of glass fibers on GRS with inorganic and organic solutions and its
environmental feasibility. e inorganic solution contains silicon ion and sodium ion at the ratio of 1 : 4 (hereinafter referred to as
Si : Na �1 :4 solutions), and the organic one is a modified polyvinyl alcohol solution (hereinafter referred to as SH solution). e
reinforced samples were subjected to plate and impact load tests, SEM, and XRD analysis to investigate their mechanical
properties, microcharacteristics, and the components produced. Results indicate that the reinforcement effect of glass fibers on
GRS under Si : Na �1 : 4 solutions was better than that of SH solutions. After being reinforced by Si : Na�1 : 4 solutions, the
samples reached maximum impact resistance. SEM results show that glass fibers bond more soil and form an integral structure;
thereby the strength was improved as glass fibers share external impact load. XRD results show that geopolymer and alkali-
activated materials and potassium feldspar were formed. Geopolymer and alkali-activated materials are pollution-free, inorganic
polymers featuring viscosity and high compressive strength. Potassium feldspar is an aluminosilicate mineral with high strength
and stable chemical properties, which can adhere to more granules and form a stronger whole structure with geopolymers playing
a role. erefore, it is feasible to reuse these soils sustainably by reinforcing them with glass fibers and the best Si : Na �1 : 4
solutions. is study finds a new direction for recycling and reusing construction waste, GRS.
1. Introduction
As China’s economy takes off in recent years, domestic
infrastructure projects expand at a frenetic pace, some of
which are subways, deep foundation pits, and other urban
underground space construction projects. Accompanied
with that, concerns over construction waste soil are picking
up. It is estimated that China excavated more than 2 million
tons of construction waste in 2019 alone [1], most of which
in South China is granite residual soil (GRS). Owing to its
porosity and water absorption, collapse and erosion occur
under the influence of wetting-drying cycles, so the soil is
usually excavated and carried off as waste in engineering [2].
However, in South China, the thickness of GRS often reaches
a depth of over 10–20 meters or even 30 meters. In practice, a
huge stack area is required for excavation and a large amount
of dust will be generated during transportation, resulting in a
huge expense and environmental pollution [3, 4]. Widely
distributed in South China, GRS is produced under specific
geographical conditions, climate, and geological environ-
ments. Since it has special composition and structure, it is
also called a regional special soil [5]. e physical and
chemical weathering made its distinctive structure with
heterogeneity and anisotropy and its unique engineering
geomechanical characteristics [6–8]. e majority of South
China is characterized by the subtropical and tropical
monsoon climate. Affected by the dry-wet cycle climate in
this region, GRS is easy to soften and disintegrate in water
and, once disturbed, prone to induce geological disasters
including landslides and collapse (Figure 1), which will
Hindawi
Advances in Materials Science and Engineering
Volume 2022, Article ID 9542258, 13 pages
https://doi.org/10.1155/2022/9542258
interrupt the construction of slopes and subgrade [9–11].
Currently, most of the granite residual soil is treated by
landfills. e profound reason for the waste of GRS is its
special structure performance, to be more specific, its high
porosity, which makes it unstable and easy to collapse in
water [12–14]. However, as the concept of sustainability and
environmental protection takes root in people, modifying
and reusing GRS has become a heated topic in recent years
and attracted the attention of many scholars [15–17].
For instance, a reinforcement system for kaolin was
formed by using industrial waste, steel slag, and slag as raw
materials, and adding active magnesium oxide and calcium
oxide. Results show that the overall skeleton structure
formed by the reinforcement system enjoys greater strength
[18, 19]. In another research, the properties of modified
concrete were improved by using kaolinite from waste soil as
raw material and adding concrete [20–22]. All the above
methods improve the mechanical properties and water
stability of granite residual soil. However, these methods are
difficult to apply widely because they cannot improve soil’s
mechanical properties and water stability while being en-
vironmentally friendly and achieving lower carbon emis-
sions. erefore, to improve GRS, several scholars have
made in-depth research. Some studies found that GRS’
porosity and hydrophilicity are the main reason for its poor
mechanical performance [7, 23, 24]. For hydrophilicity,
some scholars conducted disintegration resistance tests and
found that GRS is very easy to disintegrate in water, resulting
in the loss of strength [25–27]. e hydrophilicity of GRS is
related to kaolinite clay, its main mineral component. e
octahedral surface containing hydroxyl in the kaolinite
crystal structure is prone to form a strong hydrogen bond
with water, so kaolinite exhibits strong hydrophilicity, which
makes GRS prone to collapse in water [28–30]. At the same
time, some studies have shown that some properties of
transparent soil reinforcement are similar to those of granite
residual soil [8, 19, 31, 32]. GRS also contains a large amount
of silica, which can affect the strength of the soil [30, 33–35].
To deal with GRS’ special structure and the poor water
stability in an environment-friendly way, some scholars
studied changing the chemical composition of soil with
inorganic and organic solutions [36–38]. By changing the
content of ions in the soil, it was found that the proportion
and concentration of ions will affect the strength of granite
residual soil [39–41]. e organic SH solution can improve
the strength and bearing capacity of GRS by changing the
content of hydroxyl in it [42–44]. Different lengths of
polypropylene fibers were used to reinforce soft soil to study
the effect of fibers on soft soil reinforcement [45–47]. Results
show that their shear strength rises as the content and length
of the fibers increase. Fiber reinforcement also results in a
reduction of the compressibility of the soft clay at consec-
utive consolidation and shear stages. Meanwhile, some
studies have shown that adding glass fibers to GRS with the
organic solution can reduce cracks and improve water
stability and bearing capacity [42, 48–52].
From the above studies, many scholars have studied
reinforcing GRS with fibers, organic solutions, or chemical
treatments and verified the reinforcement effect by static
load tests. But there is no sufficient in-depth research on the
microscopic mechanism of different green chemical solu-
tions and organic modifiers on GRS, leaving their mecha-
nism unclear. erefore, the purpose of this study is to
compare the effects of different modifiers (SH solution and
Si : Na �1 : 4 solutions) on reinforcement and the impact
resistance of GRS, to analyze the mechanism of different
modifiers, and to investigate their influences on the chemical
and physical properties of the soil by SEM and XRD.
2. Experimental Materials and Methods
2.1. Raw Materials. Granite Residual Soils (GRS) are char-
acterized by strong structural connections and high strength.
ey are produced under specific climates, landforms, and
geological environments, featuring special composition and
structural characteristics. e granite residual soils used in
this experiment came from the Guangzhou area, often
comprised of mottled reddish-brown, yellowish-brown,
gray-white colors, mainly constituted of cohesive soil and
partly cobbly cohesive soil. Figure 2(a) shows the granite
residual soil used in the experiment, and its basic soil en-
gineering properties are reported in Table 1. Figure 2(b)
shows the A.P. sodium hydroxide used in the experiment.
Sodium hydroxide analytical pure is white uniform granules
with a density of 1.09 g/cm
3
and a relative molecular mass of
40, soluble, and transparent after dissolving in water.
Figure 2(c) shows the A.P. sodium silicate used in the ex-
periment. Sodium silicate is white uniform granules with
Figure 1: Granite residual soil in Youxi, Fujian province.
2Advances in Materials Science and Engineering
about 64% of silicon dioxide and 22.5% of sodium oxide,
transparent after dissolving in water. Its relative molecular
weight is 284.22.
SH polymer was a liquid-modified polyvinyl alcohol
polymer with a 5% solute mass fraction in the original
solution, from Lanzhou University, China [53]. SH polymer
could be infinitely diluted with water, its density was 1.09 g/
cm
3
, and its relative molecular mass was about 2000. e
solution shown in Figure 2(e) was the original SH polymer.
As illustrated in Figure 2(d), the average length of the glass
fiber used in the test was 12 mm. e glass fiber was an
environmentally friendly inorganic nonmetallic material
with excellent performance, which was used for the rein-
forcement of GRS in this experiment. e specific param-
eters of the glass fiber are shown in Table 2.
2.2. Preparation and Curing of Samples. e soil samples
were baked in an oven for 7 h at about 105°C. e samples
were removed from the oven after they dropped to room
temperature, crushed, and sieved at 1.18 mm. e
reinforcement materials were mixed with the soil samples
evenly. A small compaction instrument was used to make
the samples into a cylinder with a diameter of 100 mm and
a height of 50 mm (Figure 3) by adding the soils three
times. e samples were placed in a ventilated and dry
indoor place and air-dried for 14 days. e sample weight
is 1600 g.
2.3. Experimental Tests. e optimal water content test was
carried out to investigate the optimal moisture content of the
soil. e reinforced samples with optimal water content were
subjected to a static load test and drop weight impact test,
respectively. e reinforcement solutions containing dif-
ferent ratios of Si and Na were prepared under the optimal
water content. Static load tests were applied to the samples
with reinforcement solutions. Static load test plan 1 is given
in Table 3. Different amounts of sodium hydroxide and
sodium silicate were added to adjust the ratio of Si and Na in
the samples (Table 3). ree samples were made for each
ratio.
(a) (b) (c)
(d) (e)
Figure 2: Material diagram: (a) granite residual soil, (b) sodium hydroxide, (c) sodium metasilicate, (d) glass fiber, (e) SH solution.
Table 1: Properties of granite soil samples.
Specific gravity d
s
Water content ω(%) Density (g/m
3
) Liquid limit ω
l
Plastic limit ω
p
2.67 13 16.5 48.3 27
Advances in Materials Science and Engineering 3
e drop weight impact load test is given in Table 4. e
optimal content of SH solutions is 3.5% and glass fibers 3%,
both of which are formulated based on the mass of pure soil
[42]. erefore, the SH solution content is 3.5%, and glass
fiber is 3% in this study. Group H was the control group,
pure soil with a water content of 13%. Groups F and G were
experimental groups. Group F consists of 3.5% SH solution
and 3% glass fiber with a water content of 13% in addition to
pure soil. Group G consists of Si : Na �1 : 4 solutions and 3%
glass fibers with a water content of 13% in addition to pure
soil with a water content of 13%. ree samples were made
for each condition. e word “LIT” represents samples with
drop weight tests, “01” the SH solutions, “02” Si : Na �1 : 4
solutions, and “00” pure soils. For example, LIT00 refers to
pure soil samples.
2.4. Methods. e samples were prepared with seven water
percentages (11%, 12%, 13%, 14%, 15%, 16%, 17%, and 18%)
and compacted by a light compactor, after which the quality
and water content of the samples were measured. e op-
timal water content curve raging within the range of 11–18%
is given.
In the static load test, the uniaxial compressive strength
of the sample was measured with a 4 W uniaxial nonlateral
compressive tester (Figure 4). Specifically, the specimen was
placed in the center of the plate to ensure that no eccentric
loads occurred. e loading rate was 0.5 MPa/s. e loading
axial force when the sample failed was recorded to calculate
the uniaxial compressive strength of each sample with the
following formula:
R�P
A
.(1)
Ris the ultimate compressive strength of the sample, Pis
the maximum load when the sample failed, and Ais the
cross-sectional area of the sample.
e strength of the three samples under the same
concentration was recorded. e strength values were av-
eraged following the principle that the limit load does not
exceed 10%. A static load test was used to obtain the best
silicon-sodium ratio by measuring the compressive strength
of samples under different ratios.
e Instron Ceast9350 floor drop weight impact
tester for the dynamic impact load test is shown in
Figure 5 [54]. e mass of the dropping weight was
3.065 kg. e load weight in the impact load test was
36.674 kg. e falling rate of the weight was 4.5 m/s, and
the corresponding instantaneous impact energy was
403.13 J. e impact load on the sample was recorded by
the pressure sensor on the drop weight. e compression
was the displacement the drop weight had after touching
the sample [54].
Table 2: Glass fiber parameters.
Density (g/cm
3
) Linear density (dtex) Elastic modulus (MPa) Tensile strength (MPa) Melting point (°C) Elongation (%)
0.91 8.21 4286 346 169 36.4
Figure 3: Reinforced soil sample.
Table 3: Static load test plan.
Group Si : Na Water content (%) Na
2
SiO
3
(g) NaOH (g)
Static load test
O 0 13 0 0
A 1 : 1 13 40 5.80
B 1 : 2 13 40 22.34
C 1 : 3 13 40 40.0
D 1 : 4 13 40 55.20
E 1 : 5 13 40 71.68
4Advances in Materials Science and Engineering
3. Results and Discussion
3.1. Optimal Water Content Test. e curve graph of the
optimal water content and dry density from the compaction
test is shown in Figure 6. erefore, with the same amount of
compaction, the dry density of the soil first increased with
the rise of water content and topped at 1.81 g/cm
3
when the
water content was 13% and decreased with the rise water
content after that.
3.2. Static Load Test. In the static load test, the compressive
strength of the reinforced samples is found to be 780 kPa,
1250 kPa, 4250 kPa, 4550 kPa, and 1600 kPa for incorpora-
tion of solution with a Si/Na ratio of 1 : 1, 1 : 2, 1 : 3, 1 : 4, and
1 :5 (Groups A, B, C, D, and E), respectively, and 800 kPa for
Control Group O. e stress-strain curve of each group with
different silicon-to-sodium ratios is depicted in Figure 7. e
result signifies that different silicon-sodium ratios have
different reinforcement effects on soils, and the effect was
remarkable at the optimal ratio (1 : 4). From Figure 7, a
considerable rise in strength is witnessed with the decrease of
the Si/Na ratio from 1 : 1 to 1 : 4. e strength at the ratios of
1 : 3 and 1 : 4 was about 300% higher than that of 1 : 1 and 1 : 2.
However, when the Si/Na ratio decreases to 1 :5, the strength
dropped back to 1600 kPa, so the strength of the soil is not
directly proportional to the ratio. Only in a certain range can
the soil be strengthened and reinforced remarkably. us, the
Figure 4: Uniaxial compression test instrument.
Table 4: Drop weight test plan.
Group Specimen number SH solution (%) Si : Na solution Glass fiber (%) Water content (%)
Drop weight test
F LIT01 3.5 0 3 13
G LIT02 0 1 : 4 3 13
H LIT00 0 0 0 13
Control panel
Acquisition instrument
Loading area
Figure 5: Drop weight tester.
1.3
1.4
1.5
1.6
1.7
1.8
Dry density (g/cm3)
18 191716151413121110
Water content (%)
Figure 6: Optimal water content curve.
Advances in Materials Science and Engineering 5
Si/Na ratio of 0.25 is the most economical choice for rein-
forcement regarding strength and deformation.
3.3. Drop Weight Test. e drop weight test can evaluate the
ability of the sample to resist impact load. e dynamic
response of the sample can be reflected by analyzing the
instantaneous impact load of the falling weight, the com-
pression of the sample, and the response time.
3.3.1. Impact Load Analysis. Results of the impact test with
an initial velocity of 4.5 m/s (initial energy of 403.13J) show
that the SH solutions and the Si : Na �1 : 4 solutions both can
improve samples’ ultimate bearing capacity as given in Fig-
ure 8. e ultimate bearing capacity of the undisturbed soil
sample (LIT00) was 17.6 kN. at of SH solutions reinforced
sample (LIT01) was 19.8 kN, 12.5% more than LIT00. e
ultimate bearing capacity of Si : Na �1 : 4 solutions sample
(LIT02) was 98.5 kN, 459% and 397% higher than LIT00 and
LIT01, respectively. In terms of deformation, the final de-
formation of LIT01 and LIT00 was quite similar, close to
38 mm, while that of LIT02 was only 17 mm. e deformation
of LIT02 was 55.3% lower than that of LIT00 and LIT01,
nearly half. It follows that glass fibers with Si : Na �1 : 4 so-
lutions can reinforce soil better than SH solutions, strengthen
the soil, and reduce deformation significantly.
e effect of drop weight on the two samples reinforced
with glass fibers under different solutions is given in Fig-
ure 9. e relationship between impact force and defor-
mation is that the latter increases with the rise of the former
in each test and vice versa. e impact load compressed the
pores of GRS and forced soil grains to rearrange. ese
impact force-compression deformation curves can be di-
vided into four stages: rearrangement, strengthening, peak,
and weakening stage. is is consistent with the conclusions
of Yuan et al. [42].
e peak impact load of the Control Group H (LIT00)
stood at 17.6 kN, smaller than the experimental groups:
Groups G and H. Both the Si : Na �1 : 4 solutions and the SH
solutions can significantly improve the impact load resis-
tance of the samples. Although LIT01 and LIT02 were
treated with different reinforcement solutions, their impact
force-time travel curves are similar, as shown in Figure 8 that
both curves have four stages. e impact load of LIT01 went
straight up rapidly with the deformation range 0–3 mm,
reached the first peak load, and then went downward. After
hitting the first lower point, it climbed again, finally reached
the ultimate load peak with about 30 mm deformation, and
then dropped to 0 over with the final deformation of 38 mm.
e impact load of LIT02 also went straight up rapidly with
the deformation range 0–3 mm, reached the first peak load,
and then went downward. After hitting the first lower point,
it climbed again, finally reached the ultimate load peak with
about 10 mm deformation, and then dropped to 0 over with
the final deformation of 17 mm.
In the early stage, the impact load of the two shot up
because elastic deformation happened in a short time under
the impact speed of 4.5 m/s. At this moment, the external
force disturbed soil granules and made them move and
tumble, whereafter granules rearranged and aggregated.
Pores became smaller, and the effective stress between
particles increased, leading to a higher impact load. After the
first peak, the impact force of the two samples began to
decrease. rough analysis, the reason is that sample began
to crack after the elastic deformation reached the maximum
and aggravated the compression, thus resulting in a gradual
reduction of impact load. e impact load rebound at about
4 mm deformation and then rose to the maximum peak. is
is because the soil was compacted and its deformation
modulus increased after it cracked to a certain extent.
Meanwhile, the mixture of glass fibers and soil jointly bore
the impact load of the falling weight, so the sample can be
further compressed without being destroyed, which has been
proved in Dey’s study [55, 56].
In the increase phase and peak phase, the reinforcement
effects of the two solutions are particularly different. For
LIT01, although the impact force increased gradually, its
deformation rose significantly and deformed 30 mm at the
maximum impact force, while LIT02 deformed 10 mm at the
maximum impact force, over 50% less than LIT01. e
reason is that an adhesive substance similar to geopolymer
was produced between soil particles under the Si : Na �1 : 4
solutions. e substance can better bind the soil particles
together into a whole with higher strength. By contrast, the
SH solution is significantly inferior to the Si : Na �1 : 4 so-
lution in terms of viscosity.
3.3.2. Analysis of Compression and Test Response Time.
e sample was compressed under the impact load. e time
history curve of the displacement from compression is given
in Figure 10. e compression displacement of the Control
Group H (LIT00) is proportional to the time, and the slope
of the curve is approximately equal to 4.5 m/s. e sample
failed when the weight hit the sample with a speed of 4.5 m/s.
Compressive stress (Kpa)
Si:Na=1:1
Si:Na=1:2
Si:Na=1:3
Si:Na=1:4
Si:Na=1:5
Si:Na=0:0
0.03 0.06 0.09 0.12 0.15 0.180.00
Strain (%)
0
800
1600
2400
3200
4000
4800
Figure 7: Compressive strength curve.
6Advances in Materials Science and Engineering
e force that acted on the weight was little, so the slope of
the displacement compression curve is 4.5. It can be seen
from Figure 10 that, under the impact load of drop weight,
the compression of Group F (LIT01) and Group G (LIT02)
in the initial stage first increased linearly with time and then
nonlinearly to the maximum. e amount of compression
fell after the peak, indicating that the sample had a certain
degree of elastic spring back in the later loading stage. In
sample LIT02, the maximum compression was 10 mm. Due
to the elastic rebound of the soil, the final compression was
6 mm, and the response time 4.5 ms. In sample LIT01, the
maximum compression amount was 29.8 mm. Due to the
elastic rebound of the soil, the final compression amount was
28.6 mm, and the response time 14.8 ms. us, the com-
pression amount and response time of LIT02 under impact
load are minimum. is means when the glass fiber content
is maintained at 3.0%, the Si : Na �1 : 4 solutions have a
much stronger effect on GRS than the SH solution, so it can
be concluded that the reinforcement effect of Si : Na �1 : 4
solution is better than the SH solution. Furthermore, SEM
and XRD techniques can offer a microscopic perspective to
analyze the influence of the two solutions on the mechanical
properties of soil samples with glass fibers.
3.4. Scanning Electron Microscopy (SEM). Figure 11 shows
images under SEM of some samples in Groups F, G, and H
after being subjected to a drop weight test. As shown in the
picture, at the magnification of 300x, the soil of the control
Group H was granular particles with weak particle con-
nections. As a consequence, the sample could not withstand
the impact energy during shock loading and failed [57].
LIT01
LIT00
0
5
10
15
20
25
Force (kN)
5 10152025303540450
Compression Deformation (mm)
(a)
LIT02
LIT00
0
25
50
75
100
125
Force (kN)
5 10152025303540450
Compression Deformation (mm)
(b)
Figure 8: Diagram of impact force and compression deformation of specimen. (a) Groups F and H. (b) Groups G and H.
weakened phase
peak phase
increase phase
rearrangement phase
0
5
10
15
20
25
Force (kN)
5 10152025303540450
Compression Deformation (mm)
LIT01
(a)
weakened phase
peak phase
increase phase
rearrangement phase
0
25
50
75
100
125
Force (kN)
51015200
Compression Deformation (mm)
LIT02
(b)
Figure 9: Diagram of impact force and compression deformation of specimen. (a) Group F. (b) Group G.
Advances in Materials Science and Engineering 7
(a) (b) (c)
(d) (e) (f )
(g)
Figure 11: SEM of test soil magnification: 300. (a) F1. (b) F2. (c) F3. (d) G1. (e) G2. (f ) G3. (g) H.
Displacement (mm)
LIT00
LIT02
LIT01
4.5 m/s line
0
10
20
30
40
50
60
70
80
4 8 12 16 200
Times (ms)
Figure 10: Compression amount time history curve.
8Advances in Materials Science and Engineering
Compared with the SEM results of Group H, the soils of
Groups F and G were more integral after impact load since
the glass fiber bonded the soil together into an integral
structure and jointly bore the external shock load. Glass
fiber is the reinforcer in the soil, which increases the
connection between particles and fibers, increases the
friction force between them, improves the integrity of the
soil, and thus improves the ultimate bearing capacity of
the soil [58–61].
Figure 12 shows 2000x magnified images under SEM,
which were taken at the junction of glass fiber and soil. us,
less soil is attached to the glass fiber under the SH solution
than under Si : Na �1 : 4 solution. e glass fiber and the soil
formed an interactive structure under Si : Na �1 : 4 solu-
tions. In the test, the load could be transferred from soil to
fiber owing to its high tensile performance. e fiber shares
part of the load; hence the overall impact resistance of the
sample is improved. By contrast, glass fibers could not bond
soil under SH solution as they did under Si : Na �1 : 4 so-
lution. erefore, the connection between glass fibers and
soil differs between the two solutions, which leads to a
difference in the effective stress between soil particles and
fibers. Si : Na �1 : 4 solutions perform better than SH solu-
tions in terms of reinforcing soil with glass fibers. is
conclusion is proved by the drop weight test and confirmed
by SEM.
3.5. XRD. XRD spectra (Figures 13 and 14) were obtained
from test residues of LIT00, LIT01, and LIT02. e solid
phase of GRS, reinforcement solutions, and glass fibers all
changed during mechanical mixing. According to the
powder diffraction file, the XRD pattern indicates that the
main mineral components in LIT00 are kaolinite (as high as
67.8%), quartz, as well as a small amount of illite, and so-
dium-potassium feldspar. In LIT01, the diffraction strength
and angle of quartz’s characteristic diffraction peak (101) did
not change markedly compared to LIT00, indicating that the
quartz remained intact during mechanical mixing due to its
high chemical stability [62]. Kaolinite, on the other hand,
had three main reflections, with the strongest reflection at
12.3°. Compared to the XRD chart of LIT00, although their
diffraction angle remained the same, the diffraction intensity
fell significantly, indicating a decrease in the crystallinity of
kaolinite and a lower kaolinite content. e most likely
reason for this is that kaolinite particles bond with polymer
SH, which lowers the crystallinity of the kaolinite. Micro-
scopically, soil particles became more “integrated” and
therefore more difficult to destroy when resisting shock
loads [63].
In LIT02, the diffraction angle of quartz’s characteristic
diffraction peak was quite the same as in LIT00, as shown in
Figure 14, and the quartz also maintains integral. However,
the diffraction strength reduced remarkably, indicating that
(a) (b)
(c) (d)
Figure 12: SEM of Group F and Group G magnification: 2000. (a) F1. (b) F2. (c) G1. (d) G2.
Advances in Materials Science and Engineering 9
the crystallinity of quartz and its content reduced. e most
likely reason is that the kaolin particles react with a 1 : 4
sodium silicate solution, which affects the stability of quartz
during decomposition and repolymerization. At the same
time, potassium feldspar changes significantly after adding
1 : 4 sodium silicate solution, and the content of potassium
feldspar increases significantly when the reflection angle is
27.8°. e added 1 : 4 sodium silicate solution may interact
with potassium feldspar [64]. Potassium feldspar belongs to
the monoclinic crystal system, whose main components are
alumina, silicon dioxide, and potassium oxide. It is char-
acterized by high stability, high strength, and excellent
compressive performance. Most substances in LIT02 are
quartz and potassium feldspar, both of which are stable. A
small number of geopolymers and alkali-activated materials
were formed in LIT02 after adding 1 : 4 sodium silicate
solution [65, 66], and the generated geopolymers and alkali-
activated materials had higher viscosity and strength. It fills
in the pores of particles and adheres to them more firmly,
which enhances the effective stress greatly and thus
strengthens the soil [67]. Geopolymer bonds soil particles
better with fibers into a whole load of the structure, which
echoes the analysis in SEM. erefore, the overall structure
of the soil is stronger and more stable than LIT01, so it enjoys
a higher bearing capacity.
Analyzed from a microscopic perspective, more sub-
stances with higher strength and stability were generated
after adding Si : Na �1 : 4 solutions and glass fibers. Soil
particles were wrapped by the viscous geopolymer and
aggregated as a whole structure with higher compressive
strength and stability. In conclusion, based on microscopic
analysis, the reinforcement effect of glass fibers under Si :
Na �1 : 4 solutions is significantly better than that of SH
solutions.
4. Conclusions
GRS samples were subjected to static load tests and drop
weight impact load tests with a control group. is study
analyzed the influence of silicon-sodium ratios on GRS,
discussed glass fibers’ influence on the mechanical properties
of GRS under different reinforcement solutions, and in-
vestigated the microscopic mechanism behind it. e main
conclusions can be drawn below:
(1) e static load test shows that the sample exhibited
the highest compressive strength of 4550 kPa with Si :
Na �1 : 4 solutions, significantly higher than pure
soil samples. e ultimate compressive strength fell
to 180 Mpa when the ratio went down, so the best
reinforcement solution should be the one with sili-
con and sodium at the ratio of 1 : 4.
(2) e drop weight impact test shows that the glass fiber
had the best reinforcement effect on GRS when its
content was maintained at 3.0 under Si : Na �1 : 4
solutions, which performed far better than SH so-
lutions. e ultimate impact load of samples with Si :
Na �1 : 4 solutions was 98.5 kN, the response time
was 4.5 ms, and the final compression was 6 mm. By
contrast, the ultimate impact load of samples with
SH solutions was 19.8 kN, the response time 14.8 ms
and the final compression 28.6 mm.
(3) SEM and XRD analysis show that glass fibers can
significantly improve samples’ strength because of
their high tensile strength. Glass fibers bound to-
gether with soil granules and formed an integral
structure, jointly bearing the external load, thereby
improving the strength. e Si : Na �1 : 4 solutions
are superior to the SH solutions because a kind of
adhesive and high-strength geopolymer was pro-
duced under the Si : Na �1 : 4 solutions. e geo-
polymer and alkali-activated materials clump the soil
particles together more tightly. In addition, some
(001)
(-3-31)
(002)
(101)
Quartz (SiO2)
Kaolinite (AI2Si2O5 (OH)4)
LIT00
LIT01
PDF#65-0466
PDF#14-0164
10 20 30 40 50 60 70
2 Theta (degree)
Intensity
Figure 13: XRD patterns of LIT00 and LIT01.
10 20 30 40 50 60 70 80 90
2Theta (degree)
Intensity
Quartz
Kaolinite
K-feldspar
illite
Na2 (Si2O5)
Figure 14: XRD patterns of LIT02.
10 Advances in Materials Science and Engineering
substances with stable chemical properties and high
strength including potassium feldspar were also
formed. With these substances binding the soil
tightly, the effective stress between soil granules was
enhanced, so the soil was reinforced with higher
bearing capacity and stability. Geopolymers and
alkali-activated materials are green and environ-
mentally friendly materials, in line with the concept
of sustainable development, and can provide a
possibility for improving granite residual soil.
Data Availability
If necessary, data can be obtained from the corresponding
author.
Conflicts of Interest
e authors declare that they have no conflicts of interest in
this work.
Acknowledgments
e authors would like to gratefully acknowledge the sup-
port provided by the National Natural Science Foundation
of China (nos. 51978177, 41902288, and 12072079). e
editorial help from Professor Galen Leonhardy of Black
Hawk College is also greatly appreciated. In addition,
Taishan Fiberglass Inc. which provides glass fiber for ex-
periments in this paper is also worthy of appreciation.
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