Eri Setia Romadhon* | Antonius | Sumirin
© 2022 IIETA. This article is published by IIETA and is licensed under the CC BY 4.0 license (http://creativecommons.org/licenses/by/4.0/).
OPEN ACCESS
This paper investigates the mechanical properties of the geopolymer concrete using a moderately low alkali activator. The main objective is to ascertain the compressive strength, split tensile strength, elastic modulus, shear strength, flexural strength and bond strength of the said concrete. The experimental program was carried out by reviewing the variables, namely, the amount of alkaline activator which was set at 4%, and the ratio of alkali activator to fly ash (AA/FA) which was varied from 0.35, 0.4, 0.5 to 0.6. Experimental results show that the geopolymer concrete with 4% alkaline activator could still produce concrete compressive strength above 19 MPa for AA/FA ratio of 0.6 and with treatment at room temperature (33℃). On this basis, the authors derived the empirical equations for geopolymer concrete containing low alkaline activator. These equations were compared with the mechanical property model of geopolymer concrete and that of concrete containing Portland cement. The comparison shows that our model has almost the same trend as the other models.
geopolymer, alkaline activator, mechanical properties, ratio of alkali activator to fly ash (AA/FA), treatment temperature
Concrete as a construction material is widely used in structures including buildings, bridges, highways, pipes, dams, reservoirs, and drainage canals. Globally, 2.8 billion tons of Portland cement is used to make concrete annually [1]. Environmentalists have, however, sharply criticized the use of cement in concrete mixtures because it generates 4 billion tons of carbon dioxide yearly or 0.8 tons of carbon dioxide gas for every ton of cement produced [2]. To mitigate the negative effect, many researchers have tried to completely replace cement with other elements, producing ecologically friendly products like geopolymer concrete.
Geopolymer concrete has many environmental benefits [3], including carbon reduction, energy-efficient production, waste recycling [4], resistance to chemical elements [5], prevention of chloride penetration [6], and high temperature tolerance [7].
Alkaline activators and precursors rich in aluminum silicate [8] from diverse industrial by-products, including fly ash, slag furnace slag of mine waste, and volcanic ash [9], have been employed to create geopolymer concrete. Among them, fly ash is widely utilized thanks to its low cost and availability [10]. Damayanti [11] revealed that fly ash does not include B3 waste, making it suitable for use in construction materials. With fly ash as the base material, the resulting concrete can achieve a high compressive strength (fc'), which exceeds 45 MPa [12]. Multiple studies have found that a number of factors, such as mixture proportion, precursor type, alkaline activator type, sodium hydroxide molarity, sodium silicate/sodium hydroxide ratio, alkali/fly ash activator ratio, or curing temperature, can affect the compressive strength of geopolymer concrete. Targeting sodium hydroxide, Al Bakri et al. [13] varied the molarity between 6, 8, 10, 12, 14, and 16 M, with a curing temperature of 700℃, and a sodium silicate to sodium hydroxide ratio of 2.5. The results show that a molarity of 12 M produced geopolymer concrete with the maximum compressive strength.
The general way to produce geopolymer concrete is to stir solid ingredients for three minutes before adding an activator solution and stirring the mixture for another four [12]. In order to achieve the appropriate strength and workability, geopolymer concrete needs a proper mix. Ferdous et al. [14] employed 10.8% alkaline activator and 16M NaOH with fly ash. Pavithra et al. [15] adopted 8.5% NaOH and 16M alkaline activator with fly ash. Reddy et al. [16] utilized an 8.5% alkaline activator and 14M NaOH with fly ash, which is added with ground granulated blast furnace slag (GBBS).
Alkaline activator, however, is the most expensive ingredient used to make geopolymer concrete. Since the quality of geopolymer concrete is affected by the treatment temperature and material composition, efficiency must be ensured with a minimum amount of (4%) alkaline activator.
This paper investigates geopolymer concrete with two main objectives. The first objective is to identify the minimum concrete compressive strength, using a low alkaline activator, namely 4%. The compressive strength of concrete that can be produced was measured by varying the treatment temperature between the room temperature 33oC and 60oC. The second objective is to derive the equations for mechanical properties like as compressive strength, split tensile strength, flexural strength, shear strength, bond strength, elastic modulus based on the experimental results.
According to the previous literature on the mechanical behavior of geopolymer concrete, the use of alkaline activators falls between 6.7 and 15%. Alkali activator is the most expensive material in the manufacture of geopolymer concrete. As a result, efficiency must be achieved by reducing the alkaline activator fraction to as little as 4%. The mechanical behavior of the geopolymer concrete, including its compressive strength, tensile strength, flexural strength, shear strength, and elastic modulus, will primarily be impacted by the decrease in alkaline and quite considerable activator compared to what is typically utilized. By investigating the mechanical behavior of geopolymer concrete with low alkali activator, this paper successfully derives several new mechanical equations that underpin the structural design using geopolymer concrete.
Currently, the most investigated mechanical properties of geopolymer concrete include compressive strength, split tensile strength, flexural strength, shear strength and elastic modulus. In most studies, the fraction of alkaline activator is greater than 6%. Table 1 summarizes some design equations for geopolymer concrete proposed by several researchers. Ferdous et al. [14] examined the mechanical properties of geopolymer concrete with 10.8% alkaline activator, 16M NaOH, and fly ash treated at 60℃. The resulting concrete realized a compressive strength of 30–60 MPa. Similarly, Pavithra et al. [15] used 8.5% alkaline activator, 16M NaOH, and fly ash treated at 60℃, resulting in geopolymer concrete with compressive strength of 23-53 MPa. The concrete was prepared in the form of 100 mm cube specimens. Reddy et al. [16] prepared geopolymer concrete with compressive strength of 32–66 MPa from 8.5% alkaline activator, 14M NaOH, and fly ash with additional GBBS. Diaz-Loya et al. [17] measured that the density of geopolymer concrete is between 1890 and 2371 kg/ m3, the compressive strength is between 10 and 80 MPa and the elastic modulus is between 6812 and 42878 MPa. Table 1 also lists several design equations for geopolymer concrete related to the mechanical properties obtained through experiments.
ACI 318-19 [18] and AS 3600 [19] formulated the relationships between the compressive strength of concrete with elastic modulus (Ec), tensile strength (ft), flexural strength (fr) and shear stress (τb), and put forward the design equation for concrete containing cement. Yang et al. [20], prepared geopolymer concrete without fly ash, using GGBS, lime and sodium silicate. Their design equations are given in Table 1.
Ganesan et al. [21] studied the structural elements of confined geopolymer concrete, and made a geopolymer concrete mixture at a curing temperature of 60℃. On this basis, they deduced a form factor formula (r) and elastic modulus (Ec), and devised a confinement model for geopolymer concrete. This formula was adopted by Anggraini and Hardjito [22] to compare the stress-strain relationship of different confined geopolymer concretes.
Table 1. Relationship between the compressive strength of concrete and mechanical properties
|
Researcher |
Ec |
ft |
fr |
τb |
|
|
ACI [18] |
*) 4700 $\sqrt{\,}{f^{\prime}}_c$ |
0.59 $\sqrt{\,}{f^{\prime}}_c$ |
62 $\sqrt{\,}{f^{\prime}}_c$ |
$\frac{16.67}{d_b}\sqrt{\,}{f^{\prime}}_c$ |
Adopted in ACI 318-19 |
|
AS3600 [19] |
5055 $\sqrt{\,}{f^{\prime}}_c$ |
0.36 $\sqrt{\,}{f^{\prime}}_c$ |
0.6 $\sqrt{\,}{f^{\prime}}_c$ |
|
|
|
Yang et al. [20] |
4900 $\sqrt{\,}{f^{\prime}}_c$ |
0.255 ${f^{\prime}}c^{0.65}$ |
0.35 ${f^{\prime}}c^{0.65}$ |
0.8 ${f^{\prime}}c^{0.75}$ |
Without fly ash, using GGBS lime, lime and sodium silicate |
|
Lee, N.K. and Lee, H.K. [23] |
5300 $\sqrt{\,}{f^{\prime}}_c$ |
0.45 $\sqrt{\,}{f^{\prime}}_c$ |
|
|
Using fly ash and 16.1% GGBS, and 9.1% alkaline activator |
|
Thomas et al. [24] |
4400 $\sqrt{\,}{f^{\prime}}_c$ |
1.08 $\sqrt{\,}{f^{\prime}}_c$ |
|
|
Using fly ash, 25.5% GGBS and 10.2% alkaline activator |
|
Albitar [25] |
|
0.6 $\sqrt{\,}{f^{\prime}}_c$ |
0.75 $\sqrt{\,}{f^{\prime}}_c$ |
|
Using 18% fly ash and 6.7% alkaline activator |
|
Bellum et al. [26, 27] |
|
0.77 $\sqrt{\,}{f^{\prime}}_c$ |
0.98 $\sqrt{\,}{f^{\prime}}_c$ |
|
Using 17% fly ash and 6.8% alkaline activator |
|
Cui et al. [28] |
874.5 ${f^{\prime}}c^{0.85}$ |
0.0876 ${f^{\prime}}_c$ +0.0585 |
|
|
Using 17.6% fly ash and 8.8% alkaline activator |
3.1 Materials
Table 2. Composition of fly ash
|
Parameter |
% Mass |
|
SiO2 |
41.96 |
|
Al2O3 |
21.00 |
|
Fe2O3 |
16.60 |
|
CaO |
11.79 |
|
MgO |
3.06 |
|
K2O |
0.57 |
|
Na2O |
0.66 |
|
MnO2 |
0.6 |
|
SO3 |
0.98 |
|
TiO2 |
1.64 |
|
P2O5 |
0.53 |
The geopolymer concrete stacking materials include fly ash, sodium silicate, sodium hydroxide, fine and coarse aggregate. The fly ash was taken from electric steam power plant (PLTU Lontar). It is a fine dark-brown material that can pass through the 200-mesh filter. The composition of the fly ash is 79.56% (>70%) SiO2, Al2O3 and Fe2O3. It belongs to type F ash [29, 30], with more than 10% CaO (Table 2).
Sodium hydroxide (NaOH), which is in the form of white flakes, was purchased from chemical stores. NaOH solution was prepared by dissolving the NaOH flakes in water. The mass of solid NaOH in the solution varied depending on the molar concentration of the solution (M). The relative atomic mass of NaOH is 40. The NaOH solution with a concentration of 14 M can be made by dissolving as much as 560g of NaOH flakes (14×40) into water, and dilute the volume to 1L.
The ratio of sodium silicate or NaOH of geopolymer concrete belong to the range of 1.5 and 2.5. It is widely recognized that NaOH is more expensive than sodium silicate. To ensure efficiency, this study sets the sodium silicate/NaOH ratio to 2.5, which is in line with Al Bakri et al. [13], Ferdous et al. [31] and Puput et al. [32]. This ratio leads to geopolymer concrete with higher compressive strength than that using other ratios.
The washed-Bangka white sand was adopted as the fine aggregate. The mud content is less than 5%, and the resulting specific gravity is 2527 kg/m3.
The washed-rumpin crushed stone was adopted as the coarse aggregate. The mud content is less than 1% with a specific gravity of 2542 kg/m3. According to the wear test with the Los Angeles engine, the wear rate stood at 19.1%, as required by ASTM C 131-89 [33].
The gradation of the mixed aggregate meets British standards: the percentage of sand and crushed stone is 37% and 67%, respectively. The fine and coarse aggregates are in SSD condition.
The ratio of alkaline fly ash (AA/FA) was varied from 0.35, 0.4, 0.5, to 0.6. All in all, the geopolymer concrete was prepared from the following stacking material: 4% alkaline activator, 14 M NaOH and a sodium Silicate/NaOH ratio of 2.5 per one cubic meter of concrete (Table 3).
Table 3. Composition of geopolymer concrete
|
Ratio of fly ash alkaline activator solution (AAS/FA) |
0.35 |
0.4 |
0.5 |
0.6 |
|
FA (kg/ m3) |
286 |
250 |
200 |
167 |
|
NaOH (kg/m3) |
29 |
29 |
29 |
29 |
|
Na2SiO3 (kg/ m3) |
71 |
71 |
71 |
71 |
|
Fine aggregate |
728 |
744 |
766 |
782 |
|
Coarse aggregrate |
1,246 |
1,274 |
1,313 |
1,339 |
|
Water |
35 |
35 |
35 |
35 |
3.2 Specimen preparation and test method
The specimens were prepared is in accordance with ASTM C192 [34] and SNI 2493 [35]. The compressive test target is a cube of the size 100 ×100 mm (Figure 1). The target for split tensile strength and elastic modulus test is a cylinder with a diameter of 100 × 200 mm (Figure 2). The target for the flexural strength test is a beam of the size 150 × 150 × 600 mm (Figure 3). The target for the direct shear strength test is of the size 70 × 150 × 300 mm (Figure 4). The target for the bond strength test is shown in Figure 5.
The day before the test objects were made, an alkaline activator solution was made by combining sodium silicate and NaOH at a ratio of 2.5 as the first step in this study. The test items were created by combining fly ash, fine aggregate, and coarse aggregate in a mixer. The alkaline activator solution was added to the mixer after the mixture has been thoroughly blended. The homogeneous mixture was taken out from the mixer for testing [36].
Figure 1 shows the specimens of the compressive strength test in accordance with the ASTM C39. Figure 2 displays the specimens of the split tensile strength test in accordance with the ASTM C 496 [37] and the elastic modulus test in accordance with the ASTM C469 [38]. Figure 3 specimens the process of the flexural strength test in accordance with the ASTM C293. Figure 4 reports the specimens of the direct shear strength test. Figure 5 displays the specimens of the bond strength test [39].
To compute the compressive strength, the compressive test results of the cube specimens above were converted to produce a compressive strength equivalent to the results of a cylinder test on a specimen with a diameter of 150 × 300 mm at the age of 28 days (fc).
Comparing the results in Tables 4 and 5, it can be generally said that the compressive strength of our geopolymer concrete will increase, if it is treated at 60℃ or higher (Figure 7). This echoes with the finding of Hardjito et al. [12]: as the curing temperature increases, the compressive strength of fly ash-based geopolymer concrete would grow.
Besides, the compressive strength of the concrete will increase as the AA/FA ratio decreases. This trend was observed at both treatment temperatures of 33℃ and 60℃.
Figure 1. Specimens for compressive strength test (cube 100x100x100 mm)
Figure 2. Specimens for tensile strength test and elastic modulus test (cylinders 150x300 mm)
Figure 3. Specimens for flexural strength test (prism 150x150x600 mm)
(a) Direct shear test specimen
(b) Schematic of direct shear test
Figure 4. Shear test specimens
(a) Bond strength test specimen
(b) Schematic of bond strength test
Figure 5. Bond strength test specimens
3.3 Relationship between compressive strength and AA/FA ratio
Based on the data in Table 5, the authors modeled the relationship between compressive strength and the AA/FA ratio for low-lying geopolymer concrete with 4% alkali activator through nonlinear regression (Figures 6 and 7). For the treatment temperature of 33℃, the following equation can be derived as:
$f_c=13.65 AAL / FA ^{-0.847}$ (1)
For the geopolymer concrete with 4% alkali activator, the relationship between compressive strength and the AA/FA ratio at 60℃ can be derived as:
$f_c = 16.87 AAL/FA^{-0.766}$ (2)
Table 4. Compressive strength of 28d 4% AA geopolymer concrete at 33℃
|
Specimen code |
AAL/FA |
Unit weight (kg/m3) |
fc (MPa) |
|
BGT431 |
0.6 |
2.188 |
19.2 |
|
BGT432 |
0.6 |
2.234 |
21.7 |
|
BGT433 |
0.6 |
2.259 |
24.1 |
|
BGT434 |
0.5 |
2.303 |
21.1 |
|
BGT435 |
0.5 |
2.308 |
27.1 |
|
BGT436 |
0.5 |
2.414 |
22.5 |
|
BGT437 |
0.4 |
2.394 |
32.2 |
|
BGT438 |
0.4 |
2.367 |
32.7 |
|
BGT439 |
0.4 |
2.345 |
26.8 |
|
BGT4310 |
0.35 |
2.341 |
32.6 |
|
BGT4311 |
0.35 |
2.409 |
36.5 |
|
BGT4312 |
0.35 |
2.363 |
30.5 |
Table 5. Compressive strength of 28d 4% AA geopolymer concrete at 60℃
|
Specimen code |
AAL/FA |
Unit weight (kg/m3) |
fc (MPa) |
|
BGT461 |
0.6 |
2.177 |
23.2 |
|
BGT462 |
0.6 |
2.207 |
23.0 |
|
BGT463 |
0.6 |
2.203 |
25.9 |
|
BGT464 |
0.5 |
2.207 |
32.8 |
|
BGT465 |
0.5 |
2.325 |
25.5 |
|
BGT466 |
0.5 |
2.237 |
32.8 |
|
BGT467 |
0.4 |
2.310 |
32.6 |
|
BGT468 |
0.4 |
2.310 |
40.0 |
|
BGT469 |
0.4 |
2.325 |
32.5 |
|
BGT4610 |
0.35 |
2.252 |
40.7 |
|
BGT4611 |
0.35 |
2.402 |
35.3 |
|
BGT4612 |
0.35 |
2.379 |
33.6 |
Figure 6. Relationship between compressive strength and the AA/FA ratio for the geopolymer concrete with 4% alkali activator at 33℃
Figure 7. Relationship between compressive strength and the AA/FA ratio for the geopolymer concrete with 4% alkali activator at 60℃
3.4 Empirical equations
As shown in Tables 4 and 5, the compressive strength of the geopolymer concrete with 4% alkali activator at 33℃ ranged between 19 and 34 MPa. All specimens have a compressive strength above the minimum requirements for structural concrete in the relevant standard. With the exception of the BGT431 specimen, the compressive strength results all met the requirements for earthquake-resistant building structures (minimum 20.7 MPa). Therefore, this subsection intends to further discuss the results of specimens with 4% alkaline activator at the treatment temperature of 33℃. The relevant mechanical properties, such as split tensile strength, flexural strength, direct shear strength, elastic modulus and bond strength, are shown in Table 6.
3.4.1 Relationship between compressive strength and split tensile strength
For the geopolymer concrete with 4% alkali activator treated at 33℃, the relationship between split tensile strength and compressive strength can be derived from the regression results in Figure 8 using the data in Table 6:
$f_t = 0.0566 (f_c)^{1.0959}$ (3)
The model comparison in Figure 8 suggests that our model is inferior to the design equations according to ACI, Arbitar et al. and Bellum et al, while being superior to the model based on AS3600, and Yang’s model, especially when the concrete compressive strength was higher than 28 MPa.
3.4.2 Relationship between compressive strength and flexural strength
For the geopolymer concrete with 4% alkali activator treated at 33℃, the relationship between flexural strength and compressive strength can be derived from the regression results in Figure 9 using the data in Table 6:
$f_r = 0.011 (f_c)^{1.5785}$ (4)
The model comparison in Figure 9 indicates that our model predicted lower flexural strength than the other models.
Figure 8. Model comparison (regression of compressive strength vs. split tensile strength)
Figure 9. Model comparison (regression of compressive strength vs. flexural strength)
3.4.3 Relationship between compressive strength and elastic modulus
The elastic modulus equation can be generated from the regression in Figure 10:
$E_c = 2673 (f_c)^{0.65}$ (5)
Table 6. Mechanical properties of 28d 4% AA geopolymer concrete at 33℃
|
Code |
Compressive strength fc(MPa) |
Split tensile strength ft(MPa) |
Flexural strength fr(MPa) |
Direct shear strength τ (MPa) |
Modulus of elasticity Ec (MPa) |
Bond strength τb (MPa) |
|
BGM1 |
21.70 |
1.59 |
1.47 |
2.31 |
19254 |
2.69 |
|
BGM2 |
24.20 |
1.84 |
1.47 |
2.15 |
21276 |
2.65 |
|
BGM3 |
27.00 |
2.46 |
2.27 |
5.45 |
23521 |
3.58 |
|
BGM4 |
22.80 |
1.69 |
1.33 |
1.98 |
20146 |
2.79 |
|
BGM5 |
32.70 |
2.58 |
2.80 |
5.45 |
24035 |
4.91 |
|
BGM6 |
26.90 |
2.20 |
2.40 |
5.29 |
23441 |
3.58 |
|
BGM7 |
36.80 |
2.99 |
2.80 |
7.27 |
27652 |
7.17 |
|
BGM8 |
30.80 |
2.10 |
2.67 |
4.13 |
26536 |
3.72 |
Figure 10. Model comparison (regression of compressive strength vs. elastic modulus)
As shown in Figure 10, the proposed model differed significantly from the other models, such as ACI, AS3600, Yang, Lee et al., and Thomas et al, particularly from the model by Cui et al. [28], which predicted a very low elastic modulus.
3.4.4 Relationship between compressive strength and bond strength
The bond strength model was derived from the regression shown in Figure 11:
$\tau_b=0.011\left(f_c\right)^{1.7554}$ (6)
Figure 11 compares our model with other models in the regression compressive strength vs. bond strength. It can be seen that our model produced a very conservative prediction of bond strength, compared to other models.
Figure 11. Model comparison (regression of compressive strength vs. bond strength)
The main conclusions of this paper are as follows:
The experimental program presented in this paper funded by Faculty of Engineering, Universitas Jayabaya, Indonesia. The supports received for this research successfully is gratefully acknowledged.
[1] Lokuge, W., Wilson, A., Gunasekara C, Law, D.W., Setunge, S. (2018). Design of fly ash geopolymer concrete mix proportions using Multivariate Adaptive Regression Spline model. Construction and Building Materials, 166: 472-481. https://doi.org/10.1016/j.conbuildmat.2018.01.175
[2] Peng, J.X., Huang, L., Zhao, Y.B., Chen. C., Zeng, L., Zhen, W. (2012). Modeling of carbon dioxide measurement on cement plants. Advanced Materials Research, 610-613: 2120-2128. https://doi.org/10.4028/www.scientific.net/AMR.610-613.2120
[3] Chindaprasirt, P., Chalee, W. (2014). Effect of sodium hydroxide concentration on chloride penetration and steel corrosion of fly ash-based geopolymer concrete under marine site, Construction and Building Materials, 63: 303-310. https://doi.org/10.1016/j.conbuildmat.2014.04.010
[4] Li, N., Shi, C., Zhang, Z., Zhu, D., Hwang, H.J., Zhu, Y., Sun, T. (2018). A mixture proportioning method for the development of performance-based alkaliactivated slag-based concrete. Cement and Concrete Composites, 93: 163-174. https://doi.org/10.1016/j.cemconcomp.2018.07.009
[5] Zhang, J., Shi, C., Zhang, Z., Ou. Z. (2017). Durability of alkali-activated materials in aggressive environments: A review on recent studies. Construction and Building Materials, 152: 598-613. https://doi.org/10.1016/j.conbuildmat.2017.07.027
[6] Ashadi, H.W., Aprilando, B.A., Astutiningsih, S. (2015). Effects of steel slag substitution in geopolymer concrete on compressive strength and corrosion rate of steel reinforcement in seawater and an acid rain environment. International Journal of Technology, 6(2): 227-235. https://doi.org/10.14716/ijtech.v6i2.1032
[7] Barbosa, V.F.F., MacKenzie, K.J.D. (2003). Thermal behaviour of inorganic geopolymers and composites derived from sodium polysialate. Materials Research Bulletin, 38: 319-331. https://doi.org/10.1016/S0025-5408(02)01022-X
[8] Davidovits, J. (1991). Geopolymer: inorganic polymer new materials. Journal of Thermal Analysis, 37: 1633-1656. http://dx.doi.org/10.1007/BF01912193
[9] Embong, R., Kusbiantoro, A., Shafiq, N., Nuruddin, M.F. (2016). Strength and microstructural properties of fly ash based geopolymer concrete containing high-calcium and water-absorptive aggregate. Journal of Cleaner Production, 112(1): 816-822. https://doi.org/10.1016/j.jclepro.2015.06.058
[10] Xu, H., van Deventer, J.S.J. (2000). The geopolymerisation of alumino-silicate minerals. International Journal of Mineral Processing, 59: 247-266. https://doi.org/10.1016/j.jclepro.2015.06.058
[11] Damayanti, R. (2018). Coal ash and its utilization: A technical review on its chemically characteristics and toxicology. Journal of Mineral Technology and Coal Ash, 14(3): 213-231. https://doi.org/10.30556/jtmb.Vol.114.No.3.2018.966
[12] Hardjito, D., Wallah, S.E., Sumajouw, D.M.J., Rangan, B.V. (2005). Fly ash based geopolymer concrete. Australian Journal of Structural Engineering, 6(1): 77-85.
[13] Al Bakri, A.M.M., Kamarudin, H., Bnhussain, M., Rafiza, A.R., Zarlna, Y. (2012). Effect of Na2SiO3/NaOH ratios and NaOH Molarities on compressive strength of fly-ash-based geopolymer. ACI Materials Journal, 109(5): 503-508.
[14] Ferdous, M., Kayali, O., Khennane, A. (2013). A detailed procedure of mix design for fly ash based geopolymer concrete. Fourth Asia-Pacific Conference on FRP in Structures (APFIS 2013) 11-13 December 2013, Melbourne, Australia © 2013 International Institute for FRP in Construction.
[15] Pavithra, P., Dinakar, P., Rao, B.H., Satpathy, B.K., Mohanty, A.N. (2016). A mix design procedure for geopolymer concrete with fly ash. Journal of Cleaner Production, 133: 117-125. https://doi.org/10.1016/j.jclepro.2016.05.041
[16] Reddy, M.S., Dinakar, P., Rao, B.H. (2018). Mix design development of fly ash and ground granulated blast furnace slag based geopolymer concrete. Journal of Building Engineering, 20: 712-722. https://doi.org/10.1016/j.jobe.2018.09.010
[17] Diaz-Loya, E.I., Allouche, E.N., Vaidya, S. (2011). Mechanical properties of fly-ash-based geopolymer concrete. ACI Mateials Journal, 108(3): 300-306.
[18] ACI 318-19, Building code requirements for structural concrete and commentary. USA: American Concrete Institute 2019.
[19] AS 3600 (2009). Reinforced concrete design in accordance with AS 3600—2009, Cement concrete & Aggregates Australia and Standards Australia.
[20] Yang, K.H., Cho, A.R., Song, J.K. (2012). Effect of water-binder ratio on the mechanical properties of calcium hydroxide-based alkali-activated slag concrete. Construction and Building Materials, 29: 504-511. https://doi.org/10.1016/j.conbuildmat.2011.10.062
[21] Ganesan, N., Abraham, R., Raj, S.D., Sasi, D. (2014). Stress-strain behaviour of confined Geopolymer concrete. Construction and Building Materials, 73: 326-331. https://doi.org/10.1016/j.conbuildmat.2014.09.092
[22] Anggraini, N.K., Hardjito, D. (2018). Behavior of geopolymer concrete confined with circular hoops. In MATEC Web of Conferences, 159(2018): 1-7. https://doi.org/10.1051/MATECCONF/201815901018
[23] Lee, N.K., Lee, H.K. (2013). Setting and mechanical properties of alkali-activated fly ash/slag concrete manufactured at room temperature. Construction and Building Materials, 47: 1201-1209. https://doi.org/10.1016/j.conbuildmat.2013.05.107
[24] Thomas, R.J., Peethamparan, S. (2015). Alkali-activated concrete: Engineering properties and stress-strain behavior. Construction and Building Materials, 93: 49-56. https://doi.org/10.1016/j.conbuildmat.2015.04.039
[25] Albitar, M. (2016). Mechanical, Durability and Structural Evaluation of Geopolymer Concretes, Ph.D. Thesis, School of Civil, Environmental and Mining Engineering, The University of Adelaide, Australia. https://hdl.handle.net/2440/119188
[26] Bellum, R.R., Muniraj, K., Madduru, S.R.C. (2019). Empirical Relationships on Mechanical Properties of Class-F Fly Ash and GGBS Based Geopolymer Concrete, Annales de Chimie - Science des Matériaux, 43(3): 189-197. https://doi.org/10.18280/acsm.430308
[27] Bellum, R.R., Muniraj, K., Madduru, S.R.C. (2020) Exploration of mechanical and durability characteristics of fly ash‑GGBFS based green geopolymer concrete. SN Applied Sciences, 2: 919, https://doi.org/10.1007/s42452-020-2720-5
[28] Cui, Y., Gao, K., Zhang, P. (2020). Experimental and statistical study on mechanical characteristics of geopolymer concrete. Materials, 13(7): 1651. https://doi.org/10.3390/ma13071651
[29] ACI 232.2R-96 (1996). Use of fly ash in concrete, ACI Committee 232.
[30] Indonesian National Standars (SNI 2847-2019). Requirements of Structural Concrete for Buildings (in Indonesian).
[31] Ferdous, W., Manalo, A., Khennane, A., Kayali, O. (2015). Geopolymer concrete-filled pultruded composite beams-Concrete mix design and application. Cement and Concrete Composites, 58: 1-13. https://doi.org/10.1016/j.cemconcomp.2014.12.012
[32] Puput, R., Ekaputri, J.J., Mohd Mustafa, Al B. Abdullah (2015). Effect of alkaline activator ratio to mechanical properties of geopolymer concrete with trass as filler. Applied Mechanics and Materials, 754: 406-412. https://doi.org/10.4028/www.scientific.net/AMM.754-755.406
[33] ASTM C 131-89. Standard Test Method for Resistance to Degradation of Small-Size Coarse Aggregate by Abrasion and Impact in the Los Angeles Machine.
[34] ASTM C192/C192M 06. Standard Practice for Making and Curing Concrete Test Specimens in the Laboratory.
[35] Indonesian National Standard (SNI 2493). Guides of Making and Curing of Concrete Specimens in Laboratory (in Indonesian).
[36] ASTM C39 / C39M. Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens.
[37] ASTM C 496-96. Standard Test Method for Splitting Tensile Strength of Cylindrical Concrete Specimens.
[38] ASTM C469. Standard Test Method for Static Modulus of Elasticity and Poisson's Ratio of Concrete in Compression.
[39] ASTM C293. Standard Test Method for Flexural Strength of Concrete.
