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Article

Marine Geopolymer Concrete—A Hybrid Curable Self-Compacting Sustainable Concrete for Marine Applications

by
Sherin Khadeeja Rahman
* and
Riyadh Al-Ameri
School of Engineering, Deakin University, Waurn Ponds, VIC 3216, Australia
*
Author to whom correspondence should be addressed.
Appl. Sci. 2022, 12(6), 3116; https://doi.org/10.3390/app12063116
Submission received: 2 March 2022 / Revised: 11 March 2022 / Accepted: 16 March 2022 / Published: 18 March 2022
(This article belongs to the Special Issue Latest Advances in Cement and Concrete Composites)
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Abstract

:

Featured Application

This research work features the mechanical properties of a novel marine geopolymer concrete that can be used under marine exposure conditions without any strength deterioration.

Abstract

Marine environments are widely addressed as a serious threat to coastal concrete structures due to higher repair and rehabilitation costs. The rising concerns of climate change and related issues also require marine structures to be resilient and sustainable at the same time. Geopolymer concrete has been given more significant consideration as an alternative, reporting better resistance to harsh and hazardous environmental exposure, including sulphate attacks, chloride attacks, and freeze–thaw climates. This study investigated the mechanical properties of fly ash (FA) and ground granulated blast furnace slag (GGBFS)-based self-compacting geopolymer concrete (SCGC), subjected to short term ambient and marine curing conditions. The mechanical performance, inclusive of compressive strength, tensile strength, and modulus of elasticity under three-month marine exposure compared to an ambient environment, indicates that the SCGC mix offered an increase in strength. It is reported that the compressive strength of SCGC increased to the range of 50 MPa after marine exposure in comparison to the 40 MPa strength after 28-day curing. A similar increase in indirect tensile strength and modulus of elasticity were observed for the test specimens, with no signs of leaching of salts under marine exposure. Thus, the current SCGC acts as a sustainable construction material in counteracting the threats of marine degradation in civil structural components.

1. Introduction

The development of self-compacting concrete (SCC) by Okamura facilitates better constructability and confers benefits to the production and placement of concrete, especially in structural components with denser reinforcements [1]. Combining the benefits of SCC with eco-friendly geopolymer concrete-made industrial waste products such as fly ash and slag as binder materials contributes to a sustainable construction technique offering significant environmental benefits [2,3]. The similarity in properties provided by the eco-friendly sustainable concretes such as geopolymer concrete compared to ordinary concrete has received greater attention from researchers [4]. Thus geopolymer concrete is considered a viable alternative to conventional cement concrete, offering environmental benefits and decreased carbon emissions [3,4].
The geopolymer concrete is generally composed of aluminosilicate-rich binders sourced from industrial combustion by-products (fly ash and slag), along with a highly alkaline activator such as sodium hydroxide sodium metasilicate and potassium hydroxide [3,5,6,7]. In recent decades, extensive research on geopolymer concrete shows that blended geopolymer concrete containing one or more binder materials, such as slag, fly ash, and micro fly ash, aids in developing cementitious mortar under ambient conditions [8,9,10]. This type of blended concrete reduces the need for additional heat treatment, which was initially required for metakaolin-based or fly-based geopolymer concretes [7,11]. Along with the inherent environmental benefits, the geopolymer concrete offers higher mechanical strengths, fire resistance, and resistance to chemical attacks. These properties make them a suitable candidate for harsh weather applications, including in marine and saline environments where concrete structures are exposed to unstable weather or water [2,3,12,13]. Various studies have shown that heat treatment will improve the early age strengths of geopolymer concrete. Heat exposure beyond 60 °C may create a porous and non-uniform matrix of geopolymer concrete [4,14,15]. Many studies have focused on applying geopolymer concrete in hazardous environments, including elevated temperatures, freeze–thaw exposure, sulphate attack, and acid exposure; however, no specific publications have reported the behaviour of SCGC in marine/tidal conditions [16,17,18,19].
The marine environments often lead to corrosion attacks in steel-reinforced concrete structures and are severely influenced by the tidal conditions, temperature, and moisture variations, along with abrasion attacks [16,20]. The simulation of these factors proves to be complicated and is equally warranted for promoting the use and development of suitable mixes of geopolymer concrete in the marine environment. Earlier studies on geopolymer with liquid-based activator and high sodium concentrations under 3-year exposure in seawater caused a strength gain in geopolymer concrete [17,21]. Furthermore, research on artificial reefs for marine biodiversity protection adopted the use of geopolymer binders due to reduced carbon emissions and better performance in marine climate [22,23]. The activator compositions in geopolymer concrete can reduce the level of chloride ingress in geopolymer concrete, unlike the conventional OPC [17,18,24]. Sodium hydroxide, sodium silicates, and similar sodium-based high alkaline reagents are the most used activators in geopolymer concrete, which has been found to reduce the chloride binding capacity [16,17,25]. In addition to the role of activator composition, the curing conditions of the geopolymer concrete has also been assessed for the performance in marine environments against degradation by various researchers. An ultrasonic pulse velocity and surface resistivity in geopolymer concrete cured in saline water recorded higher resistance to salt ingress due to a denser internal geopolymer matrix [26].
Despite promising studies, there still exists a knowledge gap on the effect of water-immersed conditions, especially harsh marine weather conditions, on geopolymer concrete [3,4,14,27]. It is necessary to undertake further investigations on the recently developed geopolymer concrete to expand its utility to various environmental conditions. Hence, in this research work, the performance of a blended fly ash/slag based self-compacting geopolymer concrete under accelerated harsh marine weather exposure using aging tanks was assessed. This study aimed to understand and report the comparative performance of self-compacting geopolymer concrete used as an in situ structure in ambient conditions and under marine environments. This study recorded the mechanical properties for three months, including compressive strength, indirect tensile strength, and modulus of elasticity.

2. Materials and Methods

2.1. Binder Materials

The authors developed the self-compacting geopolymer concrete used in this study using a combination of Class F fly ash, ground granulated blast furnace slag, and micro fly ash [3,28,29]. The fly ash was procured from Cement Australia, ground granulated blast furnace slag (GGBFS) was supplied by Independent Cements, and Micro Fly Ash was from Fly Ash, Australia. The material properties and the chemical composition of the precursor materials used as binders in this study were obtained from the manufacturers respectively; the details as obtained are depicted in Table 1 and Table 2 below.

2.2. Alkali Activators

Liquide alkali activators are usually used in conventional geopolymer concrete production. However, this study used solid alkali activators to produce one-part geopolymer concrete [3,30]. Thus, anhydrous sodium metasilicate (Anhy.Na2SiO3)—an alkali activator powder sourced from Redox Pty Ltd.—was adopted for the study [3].

2.3. Aggregates

For a self-compacting concrete, the European Guidelines for Self-Compacting Concrete (EFNARC Guidelines) [31] recommends limiting the coarse aggregates to 50% of the total aggregate and increasing the fine aggregates for better fluidity. Due to this reason, this study adopted a ratio of 53% fine aggregates to 47% coarse aggregates to achieve self–compactness. The basalt coarse aggregate (<14 mm) and ramp-washed coarse sand (4.75 mm) supplied by Boral Construction [3] were used as coarse and fine aggregate, respectively.

3. Mixing and Casting

The self-compactness of the geopolymer concrete is dependent on the water/binder ratio; as a result, the authors optimised the water/binder ratio to 0.45 in the previous studies [3,28,29]. Similar to previously reported studies, the mixing of the self-compacting geopolymer is performed by adding the weighed binder materials (fly ash, ground granulated blast furnace slag, micro fly ash), along with the alkali activator in the dry form and the coarse and fine aggregates in a pan mixer for four minutes [3,28,29]. Then, the water was added to the mix slowly and the mixing was continued for 8 min with a rest period of two minutes between [3,28,29]. After mixing, the workability tests, including slump flow and T500, were carried out as per the EFNARC guidelines [31]. Finally, the self-compacting geopolymer concrete was poured into cylindrical moulds of 100 mm diameter and 200 mm height, and subjected to ambient curing for 28 days prior to three-month exposure to ambient and marine conditions. Ambient curing in this study refers to the air curing of the samples at a temperature of 23 ± 2 °C in the laboratory facility of Deakin University-Waurn Ponds Campus, Geelong [3,28,29]. The mix proportion and workability properties of the SCGC mix used in this study are given in Table 3 below.

4. Experimental Program

4.1. Exposure Conditions

As explained earlier, the experimental program subjected the 28-day cured cylindrical specimens to prolonged exposure to ambient and marine conditions for a period of three months. Thus, 27 specimens were subjected to extended ambient exposure after the 28-day curing for a period of three months. Similarly, another set of 27 specimens was subjected to marine exposure conditions for a period of three months after the 28-day ambient curing, making it a hybrid cured specimen set. The ambient conditions refer to exposing the test specimens in laboratory conditions, which were mainly in the range of 23 ± 2 °C for an extended period of three months, as shown in Figure 1 below.
The seawater conditions were simulated under laboratory environments for the marine conditions with reference to the previous literature [3,32,33,34,35]. Various researchers have simulated the marine exposure conditions by adopting different wet–dry cycles, high salt content, and higher water temperatures [32,33,36,37,38]. Introducing wet–dry cycles and adding salt into artificial water tanks better simulate tidal and marine environments [33,36,37,39]. Thus, this study adopted an accelerated weathering tank (also called aging tanks) to better represent the harsh marine conditions, as shown in Figure 2, Figure 3 and Figure 4 below.
An electronically automated tidal cycle comprising 6 h wet followed by a 6 h dry cycle was set to simulate the tidal conditions. Thus, after every 6 h, the seawater was pumped from one tank to the other, as shown in Figure 3. Hence, the specimens were subjected to a three-month exposure period of 6 h wet–6 h dry cycles. Again, the maximum cycle temperatures were set at 50 ± 2 °C, and the weathering tank’s salt content had 5% (mass fraction) of NaCl, simulating the salinity of seawater. All the specimens used in this study were completely immersed in the water tanks during the wet cycles, and dried during the dry periods with the help of fans and vents provided in the weathering tanks.

4.2. Test Methods

The mechanical responses of the test specimens subjected to the various exposure conditions detailed above were assessed through an experimental program. This included monthly tests for compressive strength, tensile strength, and modulus of elasticity.

4.2.1. Compressive Strength

The compressive strength test was carried out in accordance with the Australian Standard AS 1012.9:2014 [40]. A 3000 kN compression testing machine with a loading rate of 0.33 MPa/sec was used for testing the cylinder specimens at the Structures Engineering Laboratory facility at Deakin University. Three numbered cylinder specimens were used for each test and the average of those is reported as the test value.

4.2.2. Indirect Tensile Strength

A loading rate of 785 N/S in accordance with the Australian Standards, AS 1012.10:2000 [41], was adopted for recording the indirect tensile strength of the cylinder specimens. Similar to the compression test, three cylinders were used for each set of tests performed for different curing and exposure conditions in monthly intervals.

4.2.3. Modulus of Elasticity

The modulus of elasticity tests were carried out according to AS 1012.17-1997 [42]. A 3000 kN universal testing machine was used to test specimens, and the test load adopted was 16 MPa, which is equivalent to 40 percent of the design characteristic strength for the moulded concrete cylinder [3,28,42]. The test was conducted for three cycles of loading for each specimen under testing.
Thus, the monthly record of mechanical properties and performance of the specimens subjected to two types of exposure conditions, namely ambient and marine conditions, were reported in this study. In addition to the tests on mechanical properties, visual observation of the specimens was conducted regularly to check for the impact of seawater exposure, inclusive of discolouration of the samples.

5. Results and Discussion

The performance of the cylindrical specimens’ exposure to ambient and marine conditions was compared. Before this exposure, all samples were cured for 28 days under ambient conditions of 23 ± 2 °C in the Deakin University laboratory facility. For all the tests carried out in this study, at least three cylindrical specimens were used. The results of the experimental program are detailed below.

5.1. Comparison of Mass and Density Properties

Recording the change in mass of specimens under the two exposure conditions was carried out in this study along with reporting the density changes. After 28 days of curing, the cylindrical specimens recorded an average weight of 3.53 kg and a density of 2251 kg/m3. The test specimens immersed in the marine tanks were taken and surface dried before recording the weight at each interval. The test specimens’ weight changes were recorded monthly and are depicted in Table 4 and Figure 5 below.
It is observed that after three months of exposure in ambient conditions, the weight changes remained in the range of 3.50 to 3.52, reporting a weight loss of up to 1%, which confirms the observations from other studies reported in the literature [43,44,45]. This is also less than that of conventional OPC concrete/self-compacting concrete under similar conditions, where the weight loss was reported in the range of 1.1% to 2% [43].
For the marine exposure, the sample weight increased in the range of 1.1% to 1.9% over three months of exposure compared to the 28-day weight of specimens. Under marine conditions, a significant amount of water is trapped inside the samples because the natural evaporation is prevented by the alternating wet–dry cycles and higher moisture in the environment [4]. This additional water aids in the hydration of any unreacted species in the geopolymer concrete, creating a more robust geopolymer matrix, which can be reflected by the slight increase in the weight of the specimens [4]. Specifically, in a calcium-rich geopolymer concrete, such as like SCGC, this additional hydration reaction will lead to the formation of C-A-S-H gels, which reduce the porosity and condense the microstructure of the alkali-activated geopolymer matrix, leading to weight changes as reported in similar studies [4,46,47]. The weight change was reflected in the density changes, as shown in Table 5 and Figure 6 below.
As in the case of the weight change patterns, the ambient conditioned specimens followed a decreasing trend in density, reporting a loss in the density of up to 1% compared to conventional OPC-based concretes during a three-month exposure. Again, the marine exposed specimens reported an increase in density proportionate to weight changes, which seemed to stabilise over three months. However, the lack of a drop in the weight after the three-month exposure to harsh marine conditions ensured that no leaching or salt attack occurred on the cylindrical specimens after three months of exposure to wet–dry conditions.

5.2. Comparison of Compressive Strength

The mechanical tests were conducted on the test specimens monthly, corresponding to 30, 60, and 120 days of exposure to wet–dry cycles. After exposure to ambient and marine conditions, the compressive strength results along with the 28-day compressive strength values are depicted below in Table 6 and Figure 7.
The results show that, under ambient conditions, the compressive strength of the test specimens remained comparatively stable for three months. A minimal increase of 5.75% in compressive strength is observed compared to the 28-day cured specimen, attributed to the difference between individual test specimens. However, a steady increase in the compressive strength is observed for the marine exposed samples. In the first month of exposure to seawater, the compressive strength increased by 24% compared to the 28-day cured specimen and 19% for similar specimens under ambient exposure. This shows the greater affinity of geopolymer concrete mixes towards heat treatments and favourable saline conditions for the activator content. After two months of exposure to marine conditions, the compressive strength showed a slight increase of 6%; however, after three-month exposure, the strength development remained stabilised at three months of exposure to the wet–dry cycles, which simulates harsher marine exposure. It is interesting to note that, in comparison to the ambient exposed specimens, there was a 10 MPa increment in the compressive strength of the cylinder specimens even under these harsh marine exposure conditions. This is similar to the observation by Hasnoui et al. [4], wherein the geopolymer concrete cured under humidity (90% RH) and/or water immersion reported higher compressive strengths. This can be attributed to the formation of stronger bonds by hydration of slag particles that had not yet reacted with the alkaline activator [4] while avoiding the leaching phenomenon under higher humidity conditions [4]. Again, it is reported in the literature that higher temperatures are known to favour strength increments in geopolymer concrete, which can be confirmed here. It is understood that a higher temperature offered by the 50 ± 2 °C wet–dry cycles creates a heated environment that aids in the development of the strength of the core of the geopolymer concrete; thus, any unreacted species polymerises during the process. Moreover, due to the formation of geopolymeric solid bonds, the salt content was found to have a negligible effect on the degradation of the specimens in the early stages of exposure to harsh weather conditions.

5.3. Comparison of Indirect Tensile Strength

The indirect tensile tests were also conducted on the test specimens on a monthly interval with tests recorded on the 30th, 60th, and 120th days of the exposure conditions. The comparison of indirect tensile properties along with the 28-day value is depicted in Table 7 and Figure 8 below:
The marine conditioned specimens continued to develop higher tensile strength, as in the case of the pattern exhibited in the compressive strength tests. In contrast, ambient exposed samples reported minimal strength variations for the controls. However, contrary to the first-month compressive strength patterns, the tensile strength of the specimens after one month in marine conditions dropped by 11% compared to the 28-day values and similar samples in ambient exposure. However, after three months, the tensile strength reported a 9% increase, reaching 2.96 MPa. Hence, increasing tensile properties, like the compressive strengths, confirm the favourable heated environments under marine exposure. Unlike the conventional concrete, the self-compacting geopolymer concrete reports splitting tensile strength to be less than 10% of the compressive strength values, which is attributed to a greater fine content with high content of low calcium fly ash in the SCGC [3,48].

5.4. Comparison of Modulus of Elasticity

The tests on the modulus of elasticity (MOE) were also carried out at 30-, 60-, and 120-day intervals for the ambient and marine conditioned specimens, along with the 28-day testing. The MOE test results of the conditioned specimens also reveal that the marine exposure conditions favoured the test specimens under short-term exposure, as shown in Table 8 and Figure 9 below.
Generally, super-workable geopolymer concrete such as SCGC has lower modulus of elasticity values than the regular workable concrete of the same grade. This can be observed from the results of the ambient exposed specimens, whose MOE was reported in the range of 15–17 GPa for a 40 MPa strength SCGC specimen. After three months of ambient exposure, the MOE values climbed by 13%, but remained lower than the modulus of elasticity values of conventional concrete. This growth concurs with the increase in compressive strength over the exposure period. Similar studies have confirmed these trends in geopolymer concrete by various researchers [49,50,51], reporting lower modulus of elasticity for geopolymer/alkali-activated concretes [3,8,49,52,53]. However, under marine exposure, the modulus of elasticity values increased with one month of exposure, with the test specimens reporting 23.73 GPa versus 15 GPa of the ambient exposed specimens. After a three-month marine exposure, there was a 10% increase from the first month MOE of the marine specimens and a 50% increase compared to the three-month ambient exposed specimen. This can be strongly attributed to the decrease in porosity of the SCGC specimens under marine environments due to better hydration of the slag species in the SCGC mix. The Young’s modulus values improve for geopolymer concrete materials with lower porosity values. Moreover, most of the existing literature on geopolymer concrete has investigated its performance under elevated curing temperatures where the water evaporates, leading to higher porosity and lower densities. However, in the current study, ambient cured concrete was further subjected to marine water exposure, leading to the lower porosity of SCGC specimens and better MOE values [49]. This again confirms the importance of various curing and exposure conditions for the strength development of geopolymer concrete mixes.

5.5. Comparison of Visual Observation

In addition to the mechanical tests, visual observation of the specimens was also carried out to note any visible changes in the two types of test specimens. It is understood that a three-month exposure is a very short period for the assessment of the specimens’ deterioration. There was no efflorescence on the samples after three months of exposure in marine or ambient conditions. There was no crack development on the surface of the cylinder specimens. However, the core of the ambient exposed samples looked much lighter in colour compared to the marine exposed ones, as shown in Figure 10 below.
This can indicate much denser packing of the hydration of binder materials, especially slag species, due to the heated environments under marine exposure. In addition, the fairness of ambient exposed specimens may be due to lower moisture content and evaporation. However, the sample under marine environments seems denser and less porous than the ambient exposed models.
These short-term observations lead to the understanding that this novel SCGC, originally developed by the authors as a 40 MPa geopolymer concrete, offers substantial potential to be used under marine weather conditions without any strength degradation. Again, SCGC is found to provide a strength gain under marine environments with no potential salinity impacts on the structure under severe exposure conditions. The study confirms the sodium ions in the saline water and the activator favour the solidification of any unreacted species to form a denser geopolymer matrix. However, more work on long-term durability is warranted to confirm this behaviour of the SCGC mixes.
The test results suggest the hybrid curing potential of the newly developed SCGC mix. In addition to the inherent benefits of self-compacting, flowable concrete, this mix can be cured under ambient conditions and saline conditions without loss of any design strength. This ensures that the mixture can be used for in situ marine structures or precast applications. Further exposure to marine weather will not initiate any degradation in the early days of curing or exposure.

6. Conclusions

The current experimental investigation scrutinised the mechanical properties, including compressive strength, tensile strength, and modulus of elasticity, of SCGC specimens exposed to ambient and marine weather conditions. This study thus records an exciting observation of the mechanical strength developments of the short-term exposed ambient cured self-compacting geopolymer concrete, and provides a novel contribution to the body of knowledge on self-compacting geopolymer concrete. The following conclusions can be made from the experimental observations of this study:
  • When exposed to marine conditions under accelerated wet–dry cycles, the specimens did not report any loss of mass or leaching of salts in the exposure period.
  • The cylinder specimens that were exposed to hybrid exposures (28-day ambient curing followed by 3 months of immersion in artificial seawater) reported improved mechanical properties, specifically a 30% increase in compressive strength compared to the 28-day strength of 40 MPa.
  • This study confirms that the selected SCGC mix can be successfully used for marine applications, and can acquire a design strength of 40 MPa with added strength development of up to 50 MPa, under harsh marine conditions without any strength deterioration from this exposure.
  • The improved mechanical performance of SCGC confirms that the heated and humid environments favour the strength development of the mix by aiding geopolymerisation of any unreacted species in the core of the specimens.
  • This study also warrants more research to promote geopolymer concrete as a sustainable solution for marine water structures.
The authors acknowledge the need for further investigation, and ongoing research into long-term mechanical properties, and studies on sorptivity, porosity, and microstructural analysis, are underway.

Author Contributions

S.K.R.: Methodology, Investigation, Writing—Original Draft; R.A.-A.: Supervision, Writing—Review and Editing. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Available on request from authors.

Acknowledgments

The authors gratefully acknowledge the material assistance received from Independent Cements, Melbourne, and Fly Ash Australia for supplying the slag and micro fly ash, respectively, for our research work. The authors also extend their gratitude for the wholehearted support from Technical Staff Lube Veljanoski and Michael Shanahan in the completion of the experimental investigation at the Structures Laboratory, Deakin University.

Conflicts of Interest

The authors declare no conflict of interest.

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Applsci 12 03116 g001 550
Figure 1. Specimens under ambient exposure conditions.
Figure 1. Specimens under ambient exposure conditions.
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Figure 2. Accelerated weathering tanks.
Figure 2. Accelerated weathering tanks.
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Figure 3. Control panel of the accelerated weathering tank.
Figure 3. Control panel of the accelerated weathering tank.
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Figure 4. Automated tidal cycle settings.
Figure 4. Automated tidal cycle settings.
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Figure 5. Weight of ambient and marine exposed specimens.
Figure 5. Weight of ambient and marine exposed specimens.
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Figure 6. Density of ambient and marine exposed specimens.
Figure 6. Density of ambient and marine exposed specimens.
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Figure 7. Compressive strength of ambient and marine exposed specimens.
Figure 7. Compressive strength of ambient and marine exposed specimens.
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Figure 8. Indirect tensile strength of ambient and marine exposed specimens.
Figure 8. Indirect tensile strength of ambient and marine exposed specimens.
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Figure 9. Modulus of elasticity of ambient and marine exposed specimens.
Figure 9. Modulus of elasticity of ambient and marine exposed specimens.
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Figure 10. Ambient exposure vs. marine exposure after three months.
Figure 10. Ambient exposure vs. marine exposure after three months.
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Table
Table 1. Material properties of binder materials [3].
Table 1. Material properties of binder materials [3].
Material *Material Properties
Fineness (Passing through 45 µm Sieve)Loss on
Ignition		Moisture ContentSO3 ContentAvailable AlkaliRelative
Density		Chloride Ion
Content
Fly ash88%1.0%0.1%0.2%---
Micro fly ash99%0.7%0.01%0.2%0.2%2.350.001%
Ground Granulated Blast Furnace Slag97%----2.86-
* Sourced from-1. Fly Ash—Cement Australia, 2. Micro Fly Ash—Fly Ash Australia, 3. Ground Granulated Blast Furnace Slag—Independent Cements.
Table
Table 2. Chemical composition (percentage by weight) of fly ash, slag, and micro fly ash [3].
Table 2. Chemical composition (percentage by weight) of fly ash, slag, and micro fly ash [3].
Chemical
Composition		SiO2CaOAl2O3MgOK2OSO3V2O5TiO2Na2OP2O5FeO
Fly Ash (%)65.75-32.87----1.38---
Slag (%)35.1941.4713.666.32-2.430.200.73---
Micro Fly Ash (%)63.09-32.26-0.83--1.670.410.621.12
Table
Table 3. Mix proportion and workability properties of self-compacting geopolymer concrete.
Table 3. Mix proportion and workability properties of self-compacting geopolymer concrete.
Mix Proportion of SCGC (Kg/m3) [3,28]
Fly Ash480
Slag360
Micro Fly Ash120
Sodium metasilicate (Anhy.) Alkali Activator96
Fine Aggregate763
Coarse Aggregate677
Workability Properties of fresh SCGC
Slump Flow (mm)670
T500 (sec)4.10
Table
Table 4. Comparison of weight changes under ambient and marine exposure conditions.
Table 4. Comparison of weight changes under ambient and marine exposure conditions.
Days of ExposureWeight of Specimens, kgPercentage change in weight between 28-day value and ambient conditioned samples (%)Percentage change in weight between 28-day value and marine conditioned samples (%)Percentage change in weight between ambient and marine conditioned samples (%)
Value of 28-daycured specimenAmbient conditionsMarine conditions
303.533.523.570.28 (−)1.13 (+)1.42 (+)
603.513.600.57 (−)1.98 (+)2.56 (+)
1203.503.610.85 (−)2.26 (+)3.14 (+)
Note: (+) corresponds to an increase in value, (−) corresponds to a decrease in value.
Table
Table 5. Comparison of density changes under ambient and marine exposure conditions.
Table 5. Comparison of density changes under ambient and marine exposure conditions.
Days of ExposureDensity, kg/m3Percentage change in weight between 28-day value and ambient conditioned samples (%)Percentage change in weight between 28-day value and marine conditioned samples (%)Percentage change in weight between ambient and marine conditioned samples (%)
Value of 28-daycured specimenAmbient conditionsMarine conditions
3022512245.152272.730.26 (−)0.97 (+)1.23 (+)
602236.662291.830.64 (−)1.81 (+)2.46 (+)
1202228.172293.951.01 (−)1.91 (+)2.95 (+)
Note: (+) corresponds to an increase in value, (−) corresponds to a decrease in value.
Table
Table 6. Comparison of compressive strength under ambient and marine exposure conditions.
Table 6. Comparison of compressive strength under ambient and marine exposure conditions.
Days of ExposureCompressive strength, MPaPercentage change in weight between 28-day value and ambient conditioned samples (%)Percentage change in weight between 28-day value and marine conditioned samples (%)Percentage change in weight between ambient and marine conditioned samples (%)
Value of 28-daycured specimenAmbient conditionsMarine conditions
304041.749.614.25 (+)24.02 (+)18.97 (+)
6042.552.736.25 (+)31.82 (+)24.07 (+)
12042.352.585.75 (+)31.45 (+)24.30 (+)
Note: (+) corresponds to an increase in value.
Table
Table 7. Comparison of indirect tensile strength under ambient and marine exposure conditions.
Table 7. Comparison of indirect tensile strength under ambient and marine exposure conditions.
Days of ExposureIndirect tensile strength, MPaPercentage change in weight between 28-day value and ambient conditioned samples (%)Percentage change in weight between 28-day value and marine conditioned samples (%)Percentage change in weight between ambient and marine conditioned samples (%)
Value of 28-daycured specimenAmbient conditionsMarine conditions
3033.032.681 (+)10.67 (−)11.55 (−)
602.912.773 (−)7.67 (−)4.81 (−)
1202.982.960.67 (−)1.33 (−)0.67 (−)
Note: (+) corresponds to an increase in value, (−) corresponds to a decrease in value.
Table
Table 8. Comparison of modulus of elasticity under ambient and marine exposure conditions.
Table 8. Comparison of modulus of elasticity under ambient and marine exposure conditions.
Days of ExposureModulus of Elasticity, GPaPercentage change in weight between 28-day value and ambient conditioned samples (%)Percentage change in weight between 28-day value and marine conditioned samples (%)Percentage change in weight between ambient and marine conditioned samples (%)
Value of 28-daycured specimenAmbient conditionsMarine conditions
301515.1423.730.93 (+)58.2 (+)56.74 (+)
6016.522.6110 (+)50.73 (+)37.03 (+)
12017.126.1514 (+)74.33 (+)52.92 (+)
Note: (+) corresponds to an increase in value.
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Rahman, S.K.; Al-Ameri, R. Marine Geopolymer Concrete—A Hybrid Curable Self-Compacting Sustainable Concrete for Marine Applications. Appl. Sci. 2022, 12, 3116. https://doi.org/10.3390/app12063116

AMA Style

Rahman SK, Al-Ameri R. Marine Geopolymer Concrete—A Hybrid Curable Self-Compacting Sustainable Concrete for Marine Applications. Applied Sciences. 2022; 12(6):3116. https://doi.org/10.3390/app12063116

Chicago/Turabian Style

Rahman, Sherin Khadeeja, and Riyadh Al-Ameri. 2022. "Marine Geopolymer Concrete—A Hybrid Curable Self-Compacting Sustainable Concrete for Marine Applications" Applied Sciences 12, no. 6: 3116. https://doi.org/10.3390/app12063116

APA Style

Rahman, S. K., & Al-Ameri, R. (2022). Marine Geopolymer Concrete—A Hybrid Curable Self-Compacting Sustainable Concrete for Marine Applications. Applied Sciences, 12(6), 3116. https://doi.org/10.3390/app12063116

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