THE INNOVATIVE FIBER REINFORCED
GEOPOLYMER FLY ASH-BASED
GEOPOLYMER IN LOOSE SAND
STABILIZATION
Ahmed Katea*
Civil Engineering Department, Engineering College, University of Thi-Qar
ahcieng1991@utq.edu.iq
Professor Alaa H. J. Al-Rkaby
Civil Engineering, University of Thi-Qar
alaa.al-rakaby@utq.edu.iq
Reception: 26/02/2023 Acceptance: 25/04/2023 Publication: 24/05/2023
Suggested citation:
Ahmed K. And Alaa H. J. Al-Rkaby. (2023). The innovative Fiber reinforced
geopolymer fly ash-based geopolymer in loose sand stabilization. 3C
Tecnología. Glosas de innovación aplicada a la pyme, 12(2), 93-105. https://
doi.org/10.17993/3ctecno.2023.v12n2e44.93-105
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ABSTRACT
Geopolymer (GP) has recently emerged as a new and environmentally friendly
alternative to standard soil stabilization agents such as lime and Ordinary Portland
Cement (OPC) to reduce environmental concerns. The addition of fibers to treated soil
limits crack propagation, enhancing its strength even further. This study used high
calcium class C fly ash (CFA) reacted with 10 M NaOH as a geopolymer (GP) binder
to treat weak sand soil. Polypropylene (PP) fibers with a length of 4.5 mm were used
as reinforcement in amounts ranging from 0.3 to 1.5%. Microstructure and unconfined
compressive strength (UCS) testing were performed on the generated specimens.
The study proved the benefits of fiber inclusion in improving the mechanical behavior
of the treated weak soil. Superior strength characteristics were observed in GP-
treated soil mixes with a binder content of 20% and an Activator/Binder (A/B) ratio of
0.4 reinforced with 1.5% PP fibers by weight, indicating that they can be used as a
sustainable alternative to traditional binders in deep soil mixing applications.
KEYWORDS
Sustainable material, Fiber, Geotechnical application, geopolymer, soil stabilization,
SEM
INDEX
ABSTRACT
KEYWORDS
1. INTRODUCTION
2. MATERIALS
2.1. Soil
2.2. Fly Ash
2.3. Alkali activator
2.4. Fiber
3. METHODOLOGY
3.1. Compressive Strength (UCS)
3.2. Flexural Strength (FS)
3.3. Microstructure Analysis
4. RESULTS AND DISCUSSIONS
4.1. Compressive Strength
4.2. FLEXURAL STRENGTH
4.3. SEM of Geopolymer Stabilized Soil
5. CONCLUSIONS
REFERENCES
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ABSTRACT
Geopolymer (GP) has recently emerged as a new and environmentally friendly
alternative to standard soil stabilization agents such as lime and Ordinary Portland
Cement (OPC) to reduce environmental concerns. The addition of fibers to treated soil
limits crack propagation, enhancing its strength even further. This study used high
calcium class C fly ash (CFA) reacted with 10 M NaOH as a geopolymer (GP) binder
to treat weak sand soil. Polypropylene (PP) fibers with a length of 4.5 mm were used
as reinforcement in amounts ranging from 0.3 to 1.5%. Microstructure and unconfined
compressive strength (UCS) testing were performed on the generated specimens.
The study proved the benefits of fiber inclusion in improving the mechanical behavior
of the treated weak soil. Superior strength characteristics were observed in GP-
treated soil mixes with a binder content of 20% and an Activator/Binder (A/B) ratio of
0.4 reinforced with 1.5% PP fibers by weight, indicating that they can be used as a
sustainable alternative to traditional binders in deep soil mixing applications.
KEYWORDS
Sustainable material, Fiber, Geotechnical application, geopolymer, soil stabilization,
SEM
INDEX
ABSTRACT
KEYWORDS
1. INTRODUCTION
2. MATERIALS
2.1. Soil
2.2. Fly Ash
2.3. Alkali activator
2.4. Fiber
3. METHODOLOGY
3.1. Compressive Strength (UCS)
3.2. Flexural Strength (FS)
3.3. Microstructure Analysis
4. RESULTS AND DISCUSSIONS
4.1. Compressive Strength
4.2. FLEXURAL STRENGTH
4.3. SEM of Geopolymer Stabilized Soil
5. CONCLUSIONS
REFERENCES
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1. INTRODUCTION
Weak soils are found in many parts of the world and are distinguished by high
natural water content combined with poor shear strength, making them unsuitable for
supporting civil engineering constructions. (Han, 2015). However, Because of the
significant economic activity in such places, substantial infrastructure such as multi-
story buildings will be developed atop such deposits. (Porbaha, 1998). Chemical
treatment with conventional binders can improve several significant engineering
properties of soils (e.g., lime and cement). The carbon footprint of such binders has
raised considerable environmental concerns during the last decade. The production of
ordinary Portland cement (OPC) is expected to produce 7% of artificial CO2.
(Pacheco-Torgal et al., 2014). With this possibility of emissions and the other
unavoidable environmental disadvantages of nonrenewable raw materials, there is a
motivation to find more environmentally cost-effective and friendly alternative binders
to replace OPC. As a result, recycling process materials derived from aluminosilicate
industrial wastes and alkali-activated cement have been prioritized. (Davidovits,
2008). Geopolymers (GP) are cementitious binders made from amorphous (Si and Al)
industrial wastes such as fly ash (FA) and metakaolin (MK) and alkaline activators
such as potassium/sodium silicate or hydroxide. (Singhi et al., 2016).
Geopolymerization is a four-step chemical reaction that begins with ion dissolution,
then moves on to diffusion, gel formation by polymerizing Si and Al compounds with
an activator, and gel hardening. (M. Zhang et al., 2013a). GP can have outstanding
mechanical qualities such as high strength, low permeability, long durability, and
insignificant volume variations depending on the synthesis circumstances. (van
Deventer & Xu, 2002). However, it may be affected by the rate of the source material, the
chemical qualities of the activator, the temperature, and the curing period. The mechanics of
GP. The most difficult aspect is implementing the curing temperature in the field. (van
Deventer & Xu, 2002; M. Zhang et al., 2013a)
. Because they are processed at
60-90°C, most GP can only be utilized in dry heat-cured or steamed concrete. (Gianoncelli et
al., 2013). Because treating GPs at high temperatures is impractical, geotechnical engineering
uses them at room temperature. Since geopolymerization is slower at low temperatures, GP-
soil has lower impact strength and takes longer to impact than cement-treated soil. (Cristelo et
al., 2012a). Thus, in comparison to cement, FA-based GP requires higher activator
concentrations to be appropriate for soil stabilization. The bulk activator content, on the other
hand, raises the cost of this stabilization approach. (Bernal & Provis, 2014)
. Formerly,
class F fly ash (FFA) from bituminous coal combustion was used in the FA GP study. (Phair
& van Deventer, 2002). This work used FA with a high Ca concentration to increase GP
reactivity and decrease activator ratio (i.e., cost-effectiveness) while retaining satisfactory
room temperature curing. The calcium content of FFA and class C fly ash differs the most
(CFA). Both are composed of silica and alumina. CFA is made up of GGBFS and FFA.
(Duxson & Provis, 2008)
. Because GGBFS and FFA combinations are chosen for GP
manufacturing, CFA can produce them. Brittle failure was seen in the stabilized soil as the
GGBS-based geopolymer dosage was raised. (Sargent, 2015). Furthermore, the shrinkage
characteristics of slag-geopolymer stabilized soil are several orders of magnitude
greater than those of cement. (Collins & Sanjayan, 2001), This may limit its ability to
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deal with failure. As a result, reinforcing the treated soil with fibers enhances
mechanical performance by minimizing crack development. (Aydın & Baradan,
2013; Syed et al., 2020). Many studies in the last decade demonstrated that
introducing Polypropylene (PP) fibers into soil improves strength and ductility. (Freitag,
1986; Gaspard et al., 2003; Syed et al., 2020; L. Zhang et al., 2008; Ziegler et al.,
1998) As a result, Reinforcing the CFA geopolymer with discrete PP fibers could be a
feasible solution/alternative for increasing engineering properties like toughness and
ductility. (Syed et al., 2020). Soil stabilization with CFA-based geopolymers and fiber
addition has received minimal attention in the literature. As a result, a complete
examination of the mechanical and durability performance of Fiber Reinforced
Geopolymer (CFA-GP) with PP fibers in DSM technology is necessary, as disclosed in
this work.
2. MATERIALS
Soil, fly ash class C, activator, and fiber were the primary ingredients in this
investigation.
2.1. SOIL
The soil utilized in this study was locally available sand. Table 1 Its physical
properties were summarized, including grain size distribution, Specific gravity, voids
ratio, relative density (RD), maximum and minimum dry density, and angle of internal
friction. The Unified Soil Classification System classifies this sand as (poorly graded)
SP (USCS), as shown in Figure 1.
Figure 1. Grain size distribution of sand soil
0
10
20
30
40
50
60
70
80
90
1 00
0 ,010,1110
Percent passing, %
Grain size, D (mm)
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deal with failure. As a result, reinforcing the treated soil with fibers enhances
mechanical performance by minimizing crack development. (Aydın & Baradan,
2013; Syed et al., 2020). Many studies in the last decade demonstrated that
introducing Polypropylene (PP) fibers into soil improves strength and ductility. (Freitag,
1986; Gaspard et al., 2003; Syed et al., 2020; L. Zhang et al., 2008; Ziegler et al.,
1998) As a result, Reinforcing the CFA geopolymer with discrete PP fibers could be a
feasible solution/alternative for increasing engineering properties like toughness and
ductility. (Syed et al., 2020). Soil stabilization with CFA-based geopolymers and fiber
addition has received minimal attention in the literature. As a result, a complete
examination of the mechanical and durability performance of Fiber Reinforced
Geopolymer (CFA-GP) with PP fibers in DSM technology is necessary, as disclosed in
this work.
2. MATERIALS
Soil, fly ash class C, activator, and fiber were the primary ingredients in this
investigation.
2.1. SOIL
The soil utilized in this study was locally available sand. Table 1 Its physical
properties were summarized, including grain size distribution, Specific gravity, voids
ratio, relative density (RD), maximum and minimum dry density, and angle of internal
friction. The Unified Soil Classification System classifies this sand as (poorly graded)
SP (USCS), as shown in Figure 1.
Figure 1. Grain size distribution of sand soil
0
10
20
30
40
50
60
70
80
90
1 00
0 ,010,1110
Percent passing, %
Grain size, D (mm)
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Table 1. The physical properties of sand soil
2.2. FLY ASH
Local fly ash was used in this investigation, which was supplied by the Nasiriya
power generating facility as a byproduct waste material generated during the
generation of electricity. Figure 2 depicts a picture of fly ash and the particle
distribution as determined by the hydrometer test
Figure 2. The particle size distribution curve of fly ash
Soil property Standard Value
Coefficient of uniformity (cu)
ASTM D 422
2.75
Coefficient of curvature (cc) 0.81
Mean effective diameter (D50) 443
Specific gravity (Gs) ASTM D 854-00 2.65
Maximum dry density (gm/cm³)
ASTM D 4253
1.703
Minimum void ratio 558
Minimum dry density (gm/cm³)
ASTM D 4254
1.357
Maximum void ratio 0.84
Internal friction angle φASTM D 3080 36
Relative density --------------- 50
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2.3. ALKALI ACTIVATOR
In this work, sodium silicate and sodium hydroxide (NaOH) were employed to make
sodium hydroxide was 2.0.
2.4. FIBER
Commercially available fiberglass was used in this study, as shown in Figure 3.
Table 2 illustrates some of its properties.
Table 2. Fiberglass properties
Figure 3. Used Fiber
Properties Value
Length (mm) 4.5
Diameter (µm) 10
Strength (MPa) 650
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2.3. ALKALI ACTIVATOR
In this work, sodium silicate and sodium hydroxide (NaOH) were employed to make
the alkaline activator solution since they were less expensive and more readily
accessible than a potassium-based solution. Moreover, NaOH has a high ability to
release silicate and aluminate monomers. 98 percent pure sodium hydroxide pellets
were acquired. Sodium silicate was bought in liquid form. A precise amount of sodium
hydroxide pellets was dissolved in distilled water to make a NaOH solution.
Throughout the investigation, the molarity of the NaOH solution was held constant at
10 M. The solution's molarity was obtained by dissolving 400 grams of NaOH pellets
in one liter of distilled water. In this investigation, the weight ratio of sodium silicate to
sodium hydroxide was 2.0.
2.4. FIBER
Commercially available fiberglass was used in this study, as shown in Figure 3.
Table 2 illustrates some of its properties.
Table 2. Fiberglass properties
Figure 3. Used Fiber
Properties
Value
Length (mm)
4.5
Diameter (µm)
10
Strength (MPa)
650
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3. METHODOLOGY
3.1. COMPRESSIVE STRENGTH (UCS)
To study the compressive strength of geopolymer-treated soils, a series of
unconfined compressive strength tests were performed on treated samples that had
been cured for 28 days. The UCS test samples were manufactured from 50 mm
diameter and 100 mm height (PVC) cylindrical split tubes with a height-to-diameter
aspect ratio of 2:1. This sort of plastic mold has been recommended by several
researchers because it is more resistant to the alkali mixture. A longitudinal incision
was made to ease sample extraction. Before compaction, the mold was constrained
by three stainless steel clamps to avoid volumetric expansion produced by
compaction and movement.
A compressive strength test was performed on treated soil specimens using a
uniaxial machine with a loading capacity of 50 kN by (ASTM D1633-00, 2007) as eq
(1). The applied load and consequent displacements were determined using a load
cell and a Linear Variable Displacement Transducer (LVDT). The displacement rate for
all UCS tests was 0.1 mm per minute. Table 3 depicted the details of the samples.
(1)
where P = applied load (N) and A = cross sectional area of specimens (mm2).
3.2. FLEXURAL STRENGTH (FS)
Three-point bending tests were performed on specimens according to ASTM 1635/
D1635M-19, 2019, using an ARD-Auto flexural testing machine with a loading
capacity of 50 kN to investigate the flexural strength of the geopolymer-treated soil.
Samples with 35 x 35 x 130 mm dimensions were processed in rectangle molds. The
resulting displacements were measured using an LVDT. The load and its
corresponding displacement were recorded at a given time offset period. The flexural
strength of samples was calculated using the equation below:
(2)
Where FS is flexural strength (MPa),
•P is the breaking load (N).
•l is the span of the simple supports (mm).
•b is the width of the specimen (mm).
•h is the thickness of the specimen (mm)
U
CS =
P
A
F
ss=
3Pl
2bh2
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Table 3. Details of samples
*The combinations were identified using M(f). The letter M is a shortened version of the word
"Mixture," followed by the ratio (fiber), denoted by brackets.
3.3. MICROSTRUCTURE ANALYSIS
Field Emission Scanning Electron Microscope (FESEM) with Energy-Dispersive
Spectrometer was used to evaluate the microstructure samples (EDS). That test was
carried out using small prepared samples collected from UCS samples.
4. RESULTS AND DISCUSSIONS
4.1. COMPRESSIVE STRENGTH
The key factor influencing the efficiency of a fly-ash-based geopolymer as a binder
is temperature. The effects of fiber ratios on soil stabilization were investigated to
identify a viable geopolymer mixture for soil stabilization and to evaluate the
dependability of employing these new binders in weak soil stabilization. The
unconfined compressive strength (UCS) test was chosen according to the
methodology to investigate the degree of reactivity of different geopolymer content
fiber components in treated soils.
To examine the influence of fiber inclusion on soil-geopolymer strength behavior,
the UCS of treated fibers of the geopolymer-soil was tested using different fiber ratios
(0,0.25, 0.5, 0.75, 1,1.25, and 1.5%). The UCS of geopolymer-treated fibers was
determined for the above fiber ratios (1.85,2.15,2.3,2.55,2.62,2.75, and 2.81) MPa.
From Figure 4 the UCS of the specimens has improved with an increase in fiber
content from 0% to 1.5%. The increased strength can be due to the uniform
distribution of fibers throughout the treated soil matrix, which reduced the formation of
micro-cracks under loading. This could be attributable to an increase in ductility of the
treated samples as the fiber content increases. Among the various fiber contents
tested, the treated specimens reinforced with 1.5% fiber content had the highest
ductility. Figure 5 shows that at (0.25, 0.5, 0.75, 1, 1.25, 1.5%) fiber content, the
treated fibers reinforced geopolymer-earth resulted in an approximate 116, 124,
Mixture No. Mixture ID* Fly ash (%) Activator/Fly ash (A/FA) Fiber (%)
1 M (f0.25)
20 0.4
0.25
2 M (f0.5) 0.5
3 M (f0.75) 0.75
4 M (f1.25) 1.25
5 M (f1.5) 1.5
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Table 3. Details of samples
*The combinations were identified using M(f). The letter M is a shortened version of the word
"Mixture," followed by the ratio (fiber), denoted by brackets.
3.3. MICROSTRUCTURE ANALYSIS
Field Emission Scanning Electron Microscope (FESEM) with Energy-Dispersive
Spectrometer was used to evaluate the microstructure samples (EDS). That test was
carried out using small prepared samples collected from UCS samples.
4. RESULTS AND DISCUSSIONS
4.1. COMPRESSIVE STRENGTH
The key factor influencing the efficiency of a fly-ash-based geopolymer as a binder
is temperature. The effects of fiber ratios on soil stabilization were investigated to
identify a viable geopolymer mixture for soil stabilization and to evaluate the
dependability of employing these new binders in weak soil stabilization. The
unconfined compressive strength (UCS) test was chosen according to the
methodology to investigate the degree of reactivity of different geopolymer content
fiber components in treated soils.
To examine the influence of fiber inclusion on soil-geopolymer strength behavior,
the UCS of treated fibers of the geopolymer-soil was tested using different fiber ratios
(0,0.25, 0.5, 0.75, 1,1.25, and 1.5%). The UCS of geopolymer-treated fibers was
determined for the above fiber ratios (1.85,2.15,2.3,2.55,2.62,2.75, and 2.81) MPa.
From Figure 4 the UCS of the specimens has improved with an increase in fiber
content from 0% to 1.5%. The increased strength can be due to the uniform
distribution of fibers throughout the treated soil matrix, which reduced the formation of
micro-cracks under loading. This could be attributable to an increase in ductility of the
treated samples as the fiber content increases. Among the various fiber contents
tested, the treated specimens reinforced with 1.5% fiber content had the highest
ductility. Figure 5 shows that at (0.25, 0.5, 0.75, 1, 1.25, 1.5%) fiber content, the
treated fibers reinforced geopolymer-earth resulted in an approximate 116, 124,
Mixture No.
Mixture ID*
Fly ash (%)
Activator/Fly ash (A/FA)
Fiber (%)
1
M (f0.25)
20
0.4
0.25
2
M (f0.5)
0.5
3
M (f0.75)
0.75
4
M (f1.25)
1.25
5
M (f1.5)
1.5
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137,141, 148, and 152% increase in UCS compared to untreated fibers. Although
increasing the treated fiber ratios increased UCS, the rate of improvement became
slower after (0.75) fiber ratio. As a result, it is approved for use in the soil remediation
process.
Figure 4. UCS values of fiber-reinforced specimens treated at geopolymer content (20%FA
and 0.4 A/F)
Figure 5. Variation UCS for treated and untreated fibers reinforced geopolymer- soil at the
different fiber content
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1
1,1
1,2
1,3
1,4
1,5
1,6
0 ,25 0,5 0 ,75 11 ,25 1,5
UCSf / UCS
Fiber content, %
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4.2. FLEXURAL STRENGTH
percentages of fiber content (0.25, 0.5, 0.75, 1, 1.25, and 1.5).
(Sakthivel et al., 2019; Sukontasukkul & Jamsawang, 2012).
between the fibers and the geopolymer soil matrix. Treated fibers were able to restrain
the fibers and the geopolymer soil matrix sustain a higher load.
Figure 6. Flexural strength values for different fiber content samples
00,2 0,4 0,6 0,8 11,2 1,4 1,6
0
0,5
1
1,5
2
2,5
3
3,5
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
00 ,25 0,5 0 ,75 11 ,25 1,5 1 ,75
Fsf/ Fs
Fs, MPa
Fiber content, %
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4.2. FLEXURAL STRENGTH
Beams of geopolymerized loose sand based on the selected ratio of fly ash 20%
and A/F 0.4 were tested to investigate the flexural strength considering six different
percentages of fiber content (0.25, 0.5, 0.75, 1, 1.25, and 1.5).
Figure 6 showed the variation between the flexural strength and the fiber content.
Fiber content has an important role in increasing flexural strength. For example, with
increasing fiber content from 0% to 0.25, 0.5, 0.75, 1, 1.25, and 1.5%, the flexural
strength increased from 0.22 MPa for unreinforced sand to 0.27, 0.37, 0.56, 0.63,
0.67, and 0.72 MPa respectively. This means that the flexural strength increased by
122, 168, 254, 286, 304, and 327% respectively compared with the unreinforced
geopolymerized sand. These observations are in line with the results reported by
(Sakthivel et al., 2019; Sukontasukkul & Jamsawang, 2012).
When the untreated soil beam was exposed to flexural loading, just as concrete,
there was a tendency for flexural stress to develop, leading to fracture when the soil
carrying capacity was exceeded. The load developed approximately linearly with the
deflection until fracture. Finally, failure occurred when a fracture developed at the
bottom of the beam owing to stress. With the existence of fibers as reinforcements,
the external load could be transferred to such fibers through the interfacial bonding
between the fibers and the geopolymer soil matrix. Treated fibers were able to restrain
the crack propagation and traverse across the cracks to transfer internal force, and
the fibers and the geopolymer soil matrix sustain a higher load.
Figure 6. Flexural strength values for different fiber content samples
00,2 0,4 0,6 0,8 11,2 1,4 1,6
0
0,5
1
1,5
2
2,5
3
3,5
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
00 ,25 0,5 0 ,75 11 ,25 1,5 1 ,75
Fsf/ Fs
Fs, MPa
Fiber content, %
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4.3. SEM OF GEOPOLYMER STABILIZED SOIL
The compact, stable structures of geopolymer-treated samples improved
engineering properties. This primary reinforcement is caused by industrial soil bonding
reinforcement materials. In geopolymer, an alkaline media dissolves silica and
alumina oxides from fly-ash particles, creating Sodium Aluminum Silicate Hydrate (N-
A-S-H), which hardens and cement soil particles. (Cristelo, Glendinning, Miranda, et
al., 2012b; Phummiphan et al., 2016). Figure 7 shows an SEM analysis of a soil-
geopolymer sample with 20% fly ash and a ratio of activator/fly ash (0.4). A higher fly
ash ratio increases dissolution rate and binding activity, resulting in the most compact
form. (Figure 7). Typically, fly ash gaps carved by silica and aluminum breakdown are
filled by smaller particles and cementitious products, forming a thick matrix. This
technique modifies the soil structure and strengthens the treated soil., similar to
geosynthetic soil research (Abdullah et al., 2019; Cristelo et al., 2013; M. Zhang et al.,
2013b).
Figure 7. SEM images of geopolymer sample (20% fly ash, 0.4 activator)
5. CONCLUSIONS
1.
In the first stage of this work, UCS tests on treated specimens were used to
assess the strength and stiffness improvement of sand soil treated with various
combinations of fly-ash, activator, and/or fiber. The effect of the fiber-to-fly ash
ratio was the major variable explored here. The addition of fiber greatly
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improved the strength and stiffness characteristics of soil treated with fly ash-
based geopolymer. According to the findings of the studies, the ideal fiber ratio
for sand soil was 1.5%.
2.
The increase in flexural strength values follows the same pattern as the
increase in compressive strength. When the fiber content was increased, the
flexural strength increased. Flexural strength increases from 0.22 MPa to 0.72
MPa when fiber content increases from 0% to 1.5%.
3.
The cementitious products on the fly ash surfaces are observed in FESEM
analysis, indicating a geopolymerization response. The etched holes in fly ash
surfaces created by silica and aluminum breakdown are generally filled with
smaller particles, resulting in a thick matrix.
REFERENCES
(1) Abdullah, H. H., Shahin, M. A., & Sarker, P. (2019). Use of Fly-Ash Geopolymer
Incorporating Ground Granulated Slag for Stabilisation of Kaolin Clay Cured at
Ambient Temperature. Geotechnical and Geological Engineering, 37(2), 721–
740. https://doi.org/10.1007/s10706-018-0644-2
(2) Aydın, S., & Baradan, B. (2013). The effect of fiber properties on high
performance alkali-activated slag/silica fume mortars. Composites Part B:
Engineering, 45(1), 63–69.
(3) Bernal, S. A., & Provis, J. L. (2014). Durability of alkali-activated materials:
progress and perspectives. Journal of the American Ceramic Society, 97(4),
997–1008.
(4) Collins, F., & Sanjayan, J. G. (2001). Microcracking and strength development of
alkali activated slag concrete. Cement and Concrete Composites, 23(4–5), 345–
352.
(5) Cristelo, N., Glendinning, S., Fernandes, L., & Pinto, A. T. (2013). Effects of
alkaline-activated fly ash and Portland cement on soft soil stabilisation. Acta
Geotechnica, 8(4), 395–405. https://doi.org/10.1007/s11440-012-0200-9
(6) Cristelo, N., Glendinning, S., Miranda, T., Oliveira, D., & Silva, R. (2012a). Soil
stabilisation using alkaline activation of fly ash for self compacting rammed earth
construction. Construction and Building Materials, 36, 727–735.
(7) Cristelo, N., Glendinning, S., Miranda, T., Oliveira, D., & Silva, R. (2012b). Soil
stabilisation using alkaline activation of fly ash for self compacting rammed earth
construction. Construction and Building Materials, 36, 727–735.
(8) Davidovits, J. (2008). Geopolymer. Chemistry and Applications. Institute
Geopolymere, Saint-Quentin, France.
(9) Duxson, P., & Provis, J. L. (2008). Designing precursors for geopolymer
cements. Journal of the American Ceramic Society, 91(12), 3864–3869.
(10) Freitag, D. R. (1986). Soil randomly reinforced with fibers. Journal of
Geotechnical Engineering, 112(8), 823–826.
(11) Gaspard, K. J., Mohammad, L., & Wu, Z. (2003). Laboratory mechanistic
evaluation of soil-cement mixtures with fibrillated polypropylene fibers.
Proceeding of the 82th Transportation Research Board Annual Meeting.
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improved the strength and stiffness characteristics of soil treated with fly ash-
based geopolymer. According to the findings of the studies, the ideal fiber ratio
for sand soil was 1.5%.
2. The increase in flexural strength values follows the same pattern as the
increase in compressive strength. When the fiber content was increased, the
flexural strength increased. Flexural strength increases from 0.22 MPa to 0.72
MPa when fiber content increases from 0% to 1.5%.
3. The cementitious products on the fly ash surfaces are observed in FESEM
analysis, indicating a geopolymerization response. The etched holes in fly ash
surfaces created by silica and aluminum breakdown are generally filled with
smaller particles, resulting in a thick matrix.
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740. https://doi.org/10.1007/s10706-018-0644-2
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performance alkali-activated slag/silica fume mortars. Composites Part B:
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(3) Bernal, S. A., & Provis, J. L. (2014). Durability of alkali-activated materials:
progress and perspectives. Journal of the American Ceramic Society, 97(4),
997–1008.
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alkali activated slag concrete. Cement and Concrete Composites, 23(4–5), 345–
352.
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Geotechnica, 8(4), 395–405. https://doi.org/10.1007/s11440-012-0200-9
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Ed.44 | Iss.12 | N.2 April - June 2023
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