Durability of Fly Ash Based Geopolymer Concrete Against Chloride and Sulphuric Acid Attack

Volume 5, Issue 6, June – 2020 International Journal of Innovative Science and Research Technology
ISSN No:-2456-2165
Durability of Fly Ash Based Geopolymer Concrete

against Chloride and Sulphuric Acid Attack
1 2
Kartika Ilma Pratiwi, currently pursuing Master Degree Saloma, lecturer in Civil Engineering
Program in Civil Engineering, Sriwijaya University, Department in Sriwijaya University, Indonesia,
Indonesia
Abstract:- The aim of this study was to replace Portland media were tested by comparing the effects of conventional
cement with fly ash-based geopolymer as precursors, to concrete. Singh et al. [5] reported on the excellent acid
serve as a binder after reacting with NaOH and Na2SiO3 resistant ability of fly ash-based geopolymer concrete (GPC)
activators. The test object existed in the form of a cube against sulfuric and chloride attack, compared to the
of size 50 x 50 x 50 mm. The mortar was treated for 28 conventional type (OPC).
days and then immersed in a sulfate solution at similar
interval using the wet-dry cycle and non-cycle methods. Kumar et al. [6] analyzed the effect of chemical
The compressive strength of the geopolymer mortar was solutions on the behavior of geopolymer concrete. The
estimated as 45.90 MPa before immersion. Therefore, results showed the acid to be stronger than the sulfate,
35.79 MPa, 41.09 MPa, as well as 37.85 MPa were evidenced by the smaller reduction value in compressive
reported after submersion in the respective solutions of strength. Meanwhile, a value between both mix is observed
5% H2SO4, Na2SO4, and NaCl, using wet-dry cycle. with the chloride.
Based on the non-cycle approach, the resulting strength
was 37.36 MPa, 43.05 MPa and 39.52 MPa According to Wiyono et al. [7], durability is the main
correspondingly. factor to consider during concrete production, therefore
further research is needed to ensure improvement. The
Keywords:- Geopolymer mortar, durability, acid solution, concrete specimen was exposed to diluted sulfuric acid to
sulfate solution, chloride solution. accelerate the damage process, through wet-dry cycle
application. This paper discusses the resistance of fly ash-
I. INTRODUCTION based geopolymer as a substitute for Portland cement in the
manufacture of geopolymer mortar.
Portland cement, comprising silica, alumina and lime,
is the main material used as a binder in making concrete. II. MATERIAL
These chemical compounds are created through combustion
at temperatures above 1,000 ͦC, followed by the release of The basic material used in the formation of
CO2. This is a leading cause of environmental pollution, geopolymer was fly ash, obtained from PT, Pupuk
hence, the need to replace Portland cement use with Sriwidjaja Palembang. Table 1 provides an outline of the
geopolymer alternatives [1]. chemical composition, based on the XRF test results. This
showed the presence of high SiO2 and Al2O3 compounds,
The coal combustion process is known to generate instigating the possible application as a geopolymer bond.
abundant fly ash as waste materials, using electric steam In addition, the grains structure was observed using the
power plants. These products are possibly used as Scanning Electron Microscopy (SEM), and the results are
substitutes for Portland cement, due to the similarity in shown in Figure 1. Meanwhile, Figure 2 demonstrates the
particle size. In addition, the high SiO2 and Al2O3 content is level of fly ash reactivity, obtained through XRD test.
implicated in geopolymer bonds. Joseph Davidovits Figure 1 shows the Scanning Electron Microscope (SEM)
introduced the term “Geopolymer” in 1978 to describe a test results of the fly ash, indicating the a dominant round
mineral binder of varying chemical composition [2, 3]. These shape with a maximum grain diameter of ± 50 μm. Figure 2
include the high silica (Si) and alumina (Al) content, present presents the result of XRD analysis, designating the
as the primary elements in natural form, which play an amorphous characteristics as well as a high silica and
important role in the binding process. alumina content. The concentration of NaOH solution used
was 14 M with a Na2SiO3/NaOH ratio of 2. Specifically,
Sanni and Khadiriaikar [4] used fly ash as a precursor Na2SiO3 was applied in mortar mixtures to improve the
in geopolymer concrete research. This was activated using polymerization process, and also to ease the stirring process
sodium hydroxide and sodium silicate treated at 60C for 24 by serving as a superplasticizer at 5% of the fly ash content.
hours. The treatment duration is capable of increasing the However, dry materials as fine aggregate and fly ash are
polymerization process, subsequently yielding products with mixed for 3 minutes to increase homogeneity.
higher compressive strength. Subsequently, the wet mixture is put into the dry material
for 4 minutes [8], and curing is performed using the steam
The synthesized geopolymers were evaluated to method at of 60C for 24 hours.
determine the durability under different aggressive chemical
environments. For example, acidic, sulfuric and chloride
IJISRT20JUN831 www.ijisrt.com 1507

ISSN No:-2456-2165
No. Chemical Compounds Percentage (%)
1. Silicate (SiO2) 50.67
2. Alumina (Al2O3) 30.41
3. Iron Oxide (Fe2O3) 40.28
4. Lime (CaO) 4.12
5. Manganese (MnO) 0.06
6. Sodium (Na2O) 4.88
7. Potassium (K2O) 0.78
8. Phosphate (P2O5) 0.27
9. Titanium (TiO2) 0.81
10. Sulfur (SO3) 0.35
Table 1:- Chemical Composition of Fly Ash
Fig 3:- Slump flow test
Figure 4 shows the time setting test using the Vicat

needle. The results show the initial and final setting time on
mortar with 14 M NaOH concentration as 66.43 and 105
minutes respectively. This outcome is relatively faster
compared to the conventional mortar method, due to
several influencing factors, including high alkaline solution
ratio (Na2SiO3/ NaOH) and large NaOH concentrations
used in geopolymer mixtures. Furthermore, the fineness of
the fly ash grains used is also an indicator while
accelerating the setting time.
Fig 1:- SEM test results of fly ash.
Fig 4:- Setting time.

Fig 2:- XRD test results of fly ash.
B. Decrease in Mass
Geopolymer mortar cured for 28 days was weighed
III. RESULTS AND DISCUSSION and immersed in sulfuric and chloride acid solution of 5%
similar to curing period. The aim of mortar immersion was
A. Slump Flow and Setting Time
to determine the decline in mass after exposure, as show in
Slump flow testing is carried out on a mixture of fresh
Figure 5. The percentage decrease in mass of mortar
mortar, and measured using a flow table. Figure 3 shows a
immersed in H2SO4 solution is greater compared to Na2SO4
slump flow diameter of 13.50 cm, while the introduction of
and NaCl solutions using wet-dry cycle and non cycle
14 M NaOH concentration influences the properties of
methods. The drop resulted from the chemical reactions
fresh concrete produced, including the mortar mixture
between the mortar and individual test solutions during the
thickness. This leads to reduced workability, hence a
immersion process by the wet-dry non cycle method.
smaller diameter is generated.
Meanwhile, for wet-dry cycle approach, after immersion
for a day, drying is then carried out also for additional one
day. This caused a decline in the geopolymer motar
components and structure.

ISSN No:-2456-2165
C. Decrease in Compressive Strength featuring larger pores and cracks. This phenomenon was
Figure 6 shows the results of mortar compressive implicated in the degradation of compressive strength and
strength, and 45.90 MPa was recorded - 28 days before mass observed with the mortar.
being immersed. Subsequently, 35.79 MPa, 41.09 MPa and
37.85 MPa were measured by the wet-dry cycle method
after soaking in H2SO4, Na2SO4 and NaCl respectively.
Meanwhile, non cycle technique for the same set of
solutions reflected 37.36 MPa, 43.05 MPa, and 39.52 MPa
respectively after submersion.
Furthermore, all mortars dipped in sulfate and

chloride experienced degradation in strength as seen by the
deposition of a white crystal layer on the surface, while
samples immersed in H2SO4 showed the highest percentage
strength reduction (Figure 7). The decrease in mass and
compressive strength was as a result of the presence of
active calcium hydroxide (Ca(OH)2). In addition, H2SO4 (a) 28 days without immersion
exhibited greater aggressive properties, hence decreased
more significantly.
(b) 28 days of 5% Na2SO4 immersion by the wet-dry non

cycle method
Fig 5:- Percentage of decrease in mortar mass
(c) 28 days of 5% Na2SO4 immersion by the wet-dry cycle

method
Fig 6:- Decrease in compressive strength of mortar.
D. Microstructure
Figure 7 shows the result of Scanning Electron
Microscope (SEM) evaluation, performed to determine the
geopolymer mortar microstructure experiencing strength
degradation. In addition, the materials without immersion
comprised a dense and fairly smooth surface with several
scattered pores. However, attacks by sulfate and chloride
solutions led to the incidence of surface damage,
characterized by significant pore and crack formation on
the layers as the reaction proceeds. Similarly, the wet-dry (d) 28 days of 5% NaCl immersion by the wet-dry non
cycle method produced a non-dense geopolymer matrix,
cycle method

ISSN No:-2456-2165
geopolymer mortars dipped in H2SO4, Na2SO4 and NaCl
were 22.03%, 10.48% and 17.54% for the wet-dry cycle
method, while 18.61%; 6.21% and 13.90% were observed
for the wet-dry non cycle respectively. SEM test results
proved a 28-day geopolymer mortar, without immersion,
has a dense and fairly smooth surface with several scattered
pores. Meanwhile, mortar immersed for similar interval by
wet-dry cycle and non-cycle methods, produced a non-
dense geopolymer matrix, with the pores and crack getting
bigger.
ACKNOWLEDGMENT
(e) 28 days of 5% NaCl immersion by the wet-dry cycle
method The research presented in this paper was supported by
a grant from Unggulan Kompetitif Universitas Sriwijaya
2018 and PT. Semen Baturaja.
REFERENCES
[1]. S. Kumaravel and K. Girija, “Acid and salt resistance

of geopolymer concrete with varying concentration of
NaOH,” Journal of Engineering Research and
Studies, 2013.
[2]. J. Davidovits, “Chemistry of geopolymer system,
terminology,” Paper presented at the Geopolymer
International Conference, Saint Quentin, France,
1994.
[3]. Saloma, Hanafiah, D. O. Elysandi and D. G. Meykan,
(f) 28 days of 5% H2SO4 immersion by the wet-dry non “Effect of Na2SiO3/NaOH on Mechanical Properties
cycle method and Microstructure of Geopolymer Mortar Using Fly
Ash and Rice Husk Ash as Precursor,” AIP
Conference Proceedings, 1903, 050013, 2017.
[4]. S. H. Sanni and R. B. Khadiranaikar, “Performance of
Alkaline Solutions on Grades of Geopolymer
Concrete,” International Journal of Research in
Engineering and Technology, pp. 366-371, 2013.
[5]. N. Singh, S. Vyas, R. P. Pathak, P. Sharma, N. V.
Mahure, S.L. Gupta, “Effect of Aggressive Chemical
Environment on Durability of Green Geopolymer
Concrete,” International Journal of Engineering and
Innovative Technology, 3(4), pp. 277-284, 2013.
[6]. C. Kumar, K. Murari, and C. R. Sharma,
“Performance of Geopolymer Concrete at Elevated
Temperature and Against Aggressive Chemical
(g) 28 days of 5% H2SO4 immersion by the wet-dry cycle Environment,” Internationl Journal of Innovative
method Research in Science, Engineering and Technology,
Fig 7:- Microstructure. 3(6), 2014, pp. 13366-13373.
[7]. D. Wiyono, Antoni and D. Hardjito, “Improving the
IV. CONCLUSION durability of pozzolan concrete using alkaline
solution and geopolymer coating,” Procedia
Based on the research on fly ash-based geopolymer Engineering, 125, pp. 747 – 753, 2015.
mortar, the following conclusions, the slump flow diameter [8]. J. Davidovits, 30 Years of Successes and Failures in
of geopolymer mortar of 13.50 cm indicates good Geopolymer Applications, Market Trends and
workability. Initial and final setting time take 66.43 and 105 Potential Breakthroughs, in: Proceeding of Keynote
minutes respectively, signifying a rapid polymerization Conference on Geopolymer Conference, Melbourne,
process. Cyclic and non-cyclic methods were explored in 2002.
testing durability. The decrease in mass of mortar immersed
in H2SO4, Na2SO4 and NaCl solutions was 1.57%; 1.20%
and 1.37% for the wet-dry cycle; while 1.46%; 1.10% and
1.28% were obtained for the wet-dry non cycle procedure.
Meanwhile, the decrease in compressive strength of

Durability of Fly Ash Based Geopolymer Concrete Against Chloride and Sulphuric Acid Attack

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Volume 5, Issue 6, June – 2020 International Journal of Innovative Science and Research Technology

Durability of Fly Ash Based Geopolymer Concrete

IJISRT20JUN831 www.ijisrt.com 1507

Figure 4 shows the time setting test using the Vicat

Fig 1:- SEM test results of fly ash.

Fig 4:- Setting time.

IJISRT20JUN831 www.ijisrt.com 1508

Furthermore, all mortars dipped in sulfate and

(b) 28 days of 5% Na2SO4 immersion by the wet-dry non

(c) 28 days of 5% Na2SO4 immersion by the wet-dry cycle

Fig 6:- Decrease in compressive strength of mortar.

IJISRT20JUN831 www.ijisrt.com 1509

[1]. S. Kumaravel and K. Girija, “Acid and salt resistance

IJISRT20JUN831 www.ijisrt.com 1510

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