A study of Fly-Ash and Slag Based Alkali Activated Binder Using Sea Water Based Alkaline Activator

doi:10.21203/rs.3.rs-3599495/v1

This paper presents investigation in alkali activated paste and alkali activated mortar produced by combinations of flyash collected from coal based thermal power plant and ground granulated blast furnace slag collected from steel manufacturing facilities. The flyash and ground granulated blast furnace slag are industrial by products rich in aluminosilicates. The present study focuses on effect of utilization of seawater-based alkali activator solution in alkali activated paste and mortar. Alkali activator solution activates the chemical processes in binder materials when used in right concentrations and right proportion. This paper discusses the mechanical properties and microstructure characteristics of seawater-based alkali activated paste and mortar in comparison with conventional distilled water-based alkali activator. The usage of sea water shown insignificant change in setting times and compressive strengths for various combinations of binder material. The microstructure analysis also showed less variation in mineralogical formations when conventional distilled water is replaced with sea water in preparation of alkali activator solution.

Seawater based alkali activators

Flyash

Ground Granulated Blast Furnace Slag (GGBS)

Compressive Strength

Alkali Activated Mortar

Mineralogical Composition

Fresh water resources are depleting due to climate change, population growth, urbanization, and industrialization. Usage of fresh water in concrete production is inevitable. Fresh water is also required for curing of concrete. As the water resources are depleting an alternative to usage of fresh water must be addressed. Natural salt water from sea or ocean accounts for approximately 97% of surface and subsurface water and it could be a potential choice for using in concrete when fresh water is too expensive to be used or unavailable [1]. It is expected that by 2050 approximately 75% of water demand to produce concrete will happen in areas most likely to experience water scarcity [2]. The cement based concrete production involves extensive use of water and caters higher emissions of CO₂. The global CO₂ emissions due to production of cement is also increasing rapidly. In the last decade cement production rose from 3.8 giga tons (Gt) to 4.5 Gt approximately. It is equivalent to 3.2 Gt of CO₂ emissions, and it is about 8% of the annual anthropogenic CO₂ emissions worldwide [3]. The CO₂ emissions in cement production has been increased by 1.8% per year during years 2015–2020. To achieve net zero CO₂ emissions by year 2050 a reduction rate of 3% in CO₂ emissions per annum is required [4]. Ordinary Portland cement (OPC) is the main raw material of concrete having advantages such as high strength, low drying shrinkage, etc. but large number of natural resources are consumed in production of OPC, the thermal and electrical energy was consumed more than 2.72 GJ/ton and 65 kWh/ton, respectively [5]. It is becoming a global threat to living organisms with increased use of OPC.

The present study describes the use of alternate materials to both OPC and fresh water in preparation of concrete. To counter the environmental challenges such as depletion of freshwater resources and larger CO₂ emissions in production of concrete with OPC, geopolymer concrete as an alternate is being studied by many researchers. The concept of geopolymers was first proposed by Davidovits in 1978[6]. They are made of sustainable materials resulting from the reaction of industrial by-products such as fly ash, blast furnace slag, metakaolin, palm oil fuel ash, rice husk ash, etc., with alkaline solutions made of alkali hydroxide solutions and soluble silicate solutions in the room or high temperature environment [7]. Aluminosilicate minerals were dissolved in solutions and then free SiO4 and AlO4 tetrahedral units were reacted by sharing oxygen atoms. The polymeric Si–O–Al–O bonds which are similar to amorphous feldspar were formed in geopolymerization [8]. Franca, et al. reviewed usage of high calcium and low calcium alkali activated materials and compared the mechanical properties and concluded that high calcium AAMs area exhibiting better performance [9].

Beibei Sun et al. discussed properties of flyash and GGBS based alkali activated mortar using alkali activator solution made of Sodium Hydroxide and Sodium Silicate solutions. The combination of raw materials can provide alkali activated mortar with more excellent comprehensive performance. The studies have shown that the alkali activator made of NaOH and Na₂SiO₃ could stimulate the strength of alkali activated mortar more effectively [10]. Poornima Natarajan et al., in their research explored the possibility of utilising high-volume fly-ash with GGBS as a replacement for cement as binder and observed properties of alkali-activated cement (AAFSC) at high temperatures. It is observed that thermal impact on strength and mass loss is greatly reduced in AAFSC as compared to OPC. [11]. SK Jhon et al. in his study, presented that the workability and setting time decreased evidently with usage of multi compound alkali activator made with sodium hydroxide and low modulus sodium silicate in flyash GGBS based alkali activated paste. The addition of GGBS to flyash based geopolymer mortar shown significant reduction in setting time and workability [12]. Bharat Bhushan Jindal in his review paper discussed the significance of mass ratio of sodium hydroxide to sodium silicate. He stated that the ratio of 2.5 is suitable in flyash based geopolymer concrete to achieve required strength. (Jindal, 2018).

Mallikarjun Rao et al. studied mechanical properties of flyash and GGBS based geopolymer paste and mortar. In his study he discussed that the molarity of sodium hydroxide in alkali activator solution is not affecting standard consistency significantly. He also concluded that combination of flyash and GGBS based geopolymer concrete can be a possible solution for outdoor air curing [14]. Abhishek et al. in their review mentioned about the molarity of NaOH and the ratio of Na₂SiO₃ to NaOH. They observed that the molarity impacts the setting time and flow properties of alkali activated paste due to changes in the viscosity as the dissolution of aluminosilicates in the alkaline solution proceeds [15]. T Chaitanya Srikrishna et al. described sodium hydroxide concentration is one of the influential parameters on mechanical strength and durability characteristics of slag based geopolymer concrete [16]. In another study, T Chaitanya Srikrishna et al. described the increase in sodium hydroxide concentration resulted in increase in the intensity of albite peaks. The low concentrations of sodium hydroxide which are less than 8M have significant effect on consistency, setting time and compressive strength of slag based geopolymer concrete [17]. Mallikarjun Rao G et al. discussed the change in compressive strength for oven cured and air cured GPC samples based on flyash and GGBS. The observations show the increase in compressive strength with increase in GGBS content in mix. He stated that the presence of higher contents of calcium in GGBS was the critical factor to attain strength of GPC which increase in GGBS which enhanced with C-A-S-H gel formation. [18].

Rashad et al. described the performance of seawater in alkali activator solutions in slag paste. The results showed high flowability and compressive strength when seawater was used in alkali activator. The rates of enhancement of compressive strength at the early ages were higher than those at the later ages but the enhancement rate was decreased at the later ages [2]. In another study of Rashad et al. the effect of different ratios of untreated sea sand on the compressive strength and durability of fly ash based geopolymer mortars activated with sodium silicate. The results showed that the incorporation of sea sand into flyash based geopolymer mortars has a negative effect on the compressive strength as well as the percentage of water absorption [19]. Salman Siddique in his research paper discussed a detail study on performance of geopolymer using flyash as binder material and a comparison with different types of water is provided [20]. According to his study the presence of chloride in sea water contributed to increase in compressive strength, refine microstructure, and mineralogical characteristics. The XRD results showed that the use of sea water has negligible effects on the mineralogical phases of alkali-activated fly ash material. Moreover, the absence of any chloride and sulphate based crystalline minerals is evidence of the immobilization potential of the alkali activation process. The results provided new insights demonstrating that sea water can be effectively used to produce alkali activated fly ash material[20]. Seawater is abundantly available and easily accessible in coastal regions. If the usage of seawater replaces distilled water, in the preparation of alkaline solution for geopolymerization, the production cost and energy consumed in distillation process of water will be enormously reduced. The present study focuses on usage of seawater to replace distilled water in preparation of alkali activated binders and identify impact on consistency and strength aspects.

The present study is conducted on 11 different combinations of flyash and GGBS based alkali activated paste and alkali activated mortar. The combinations are decided such that the flyash is replaced with 10% increment of GGBS by weight. The combinations are denoted with flyash percentage and GGBS percentage for each sample. The combination F100G0 is 100% flyash and 0% GGBS, similarly the combination F60G40 is 60% flyash by weight and 40% GGBS by weight. The 11 combinations include F100G0 to F0G100 samples. These combinations are again differentiated into two sets where seawater is used in alkali activator solution in one set and distilled water is used in the other. The seawater-based alkali activator solution is denoted with SW-AS and distilled water-based alkali activator solution is denoted with DW-AS. The samples are differentiated by giving letter M as prefix to sea water-based alkali activator solutions and letter D as prefix to distilled water-based alkali activator solutions. The consistency, setting time, compressive strength and XRD tests are conducted on all the combinations and obtained results are discussed in following sections.

The alkali activated paste and mortar are prepared by using fly ash, ground granulated blast furnace slag (GGBS) and an alkali activator solution. The alkali activator solution is prepared using sodium hydroxide pallets and sodium silicate. A mixture of 8 molar sodium hydroxide and sodium silicate solution is used for the consistency and setting times tests. A mixture of 12 molar sodium hydroxide and sodium silicate solution is used for the mortar cubes of compressive strength tests. The combinations of different proportions of fly ash and GGBS are prepared at 10% variation in weight. As part of the present study seawater is used for preparation of 8 molar and 12 molar sodium hydroxide solutions. Natural Sea water is collected from Manginapudi Beach near Machilipatnam, Andhra Pradesh, India. The solution is then mixed with sodium silicate to obtain seawater based alkaline activator solution (SW-AS). All the samples prepared with seawater-based alkaline solutions are given a prefix with letter M. A control specimen for each of the sample is also prepared by using distilled water based alkaline activator solution (DW-AS) and are denoted with the prefix as letter D. River sand confirming to Zone II standards according to IS 383 (2016) [21]is used as fine aggregate. It is sieved in dry condition through 4.75 mm sieve to remove all the pebbles. The Specific gravity of sand is 2.65 and fineness modulus is 2.81.

2.1 Binder Materials

Fly ash (Class F) and GGBS are used as binders in this study. Fly ash was obtained from Dr. Narla Tata Rao Thermal Power plant, Kondapalli, India. GGBS is collected from JSW Cements, Nandyal, India. The specific gravity of fly Ash and GGBS is 2.1 and 2.7. XRF method of elemental analysis done for both fly ash and GGBS. Table 1 represents the elemental composition of binder materials fly ash and GGBS. The elements present in the binder material effects the formation of various minerals and their characteristics explained in detail in XRD analysis of present study.

Table 1

Elemental Composition of Fly ash and GGBS
Element	Fly ash (%)	GGBS (%)
Si	57.6	25.7
Al	21.4	12.7
Fe	11.0	1.24
Ti	3.41	1.21
K	2.83	0.559
Ca	1.89	49.3
S	0.214	1.14
Mg	0.182	5.65

2.2 Alkaline Activating Solution

Two types of alkaline activator solution are used in the present study. The study is to identify the usage and performance of sea water in comparison with conventional methods of preparation of alkaline activator solution. To enable the use of seawater different molarities of sodium hydroxide solution are prepared using seawater as solvent. It is then mixed with sodium silicate solution in required proportion to obtain alkaline activator solution. This solution is used in preparation of alkaline activator paste and alkaline activator mortar cubes as per proposed mix proportions.

The sodium hydroxide pallets of 98% purity are obtained from SD Fine Chem Limited, Mumbai, India. The sodium hydroxide solution of 8 Molar and 12 Molar are prepared with both seawater and distilled water for the present study. Sodium silicate solution is obtained from Loba Chemie., Mumbai, India. The sodium silicate solution contains 27.98% of SiO₂, 8.11% of Na₂O and 63.91% of water. The mass ratio of SiO2 to Na2O of the sodium silicate solution is 3.45. The seawater used for the preparation of sodium hydroxide solution has pH of 7.49. ICP-OES Analysis for seawater is conducted on 1 litre of sample. The elements present in the seawater sample obtained using ICP-OES Analysis as per IS 3025 (Parts) are listed in Table 2.

Table 2

Elemental Analysis of Seawater
S. No	Test parameter	Value (ppm)
1	Chlorides as Cl	13400
2	Sodium as Na	5503.4
3	Sulphate as SO₄	1569.3
4	Magnesium as Mg	800.7
5	Potassium as K	342.2
6	Bromide	58.4
7	Calcium as Ca	50.74
8	Phosphorus as PO₄	4.97
9	Nitrite	4.57
10	Fluoride	1.2
11	Aluminium as Al	1.174
12	Nitrate	0.32
13	Barium as B	0.049

The distilled water used for preparation of sodium hydroxide solution is obtained from local manufacturers in Andhra Pradesh, India. The solutions are prepared and stored at room temperature and retained for 24 hrs before its use.

2.3 Alkali Activated Paste

Alkali activated paste is prepared to conduct consistency and setting time tests. The fly ash and GGBS at required proportions for each combination are mixed in dry condition and later the alkaline activator solution is added. The mixture is activated by adding the alkaline activator solution and is mixed for about 3 minutes to ensure homogeneity. 8 Molar sodium hydroxide solution is used in the alkaline activator for the preparation of paste. The different combinations of fly ash and GGBS binder proportions with both SW-AS and DW-AS are prepared for tests and results are compared.

2.4 Alkali activated Mortar

The alkali activated mortar is prepared to cast cube specimens of 7.06 cm. The mortar mix is prepared with different proportions of fly ash and GGBS as binder material. River sand is used as fine aggregate. The activator solution made of both sea water and distilled water are used separately for preparation of alkali activated mortar mix. The alkali activator used in the mortar mix is prepared with 12 molar sodium hydroxide solution and sodium silicate solution. The ration of binder to fine aggregate is taken as 1:1 by weight. The alkali activator solution to binder ratio is taken as 0.45. The mix proportions of required materials for preparation of one 7.06cm cube specimen of all combinations by weight are presented in Table 3.

Table 3

Mortar mix proportions for all combinations of Fly ash and GGBS
Mix Type (FA%+GGBS%)	Fly Ash (gm)	GGBS (gm)	Total Binder (gm)	Fine Aggregate (gm)	Alkaline Solution (gm)	NaOH (gm)	Na₂Sio₃ (gm)
F100G0	316	0	316	316	142	41	101
F90G10	284.4	31.6	316	316	142	41	101
F80G20	252.8	63.2	316	316	142	41	101
F70G30	221.2	94.8	316	316	142	41	101
F60G40	189.6	126.4	316	316	142	41	101
F50G50	158	158	316	316	142	41	101
F40G60	126.4	189.6	316	316	142	41	101
F30G70	94.8	221.2	316	316	142	41	101
F20G80	63.2	252.8	316	316	142	41	101
F10G90	31.6	284.4	316	316	142	41	101
F0G100	0	316	316	316	142	41	101

Fine aggregate, fly ash and GGBS are dry mixed before adding alkaline solution for 3 mins. The alkali activated materials, sand and alkaline solution are mixed for another 10 min in mortar mixer to ensure homogeneity. Conventional table vibrator is used for compaction of the mortar in cube molds. The specimens are demolded after 24 hours and cured at room temperature.

There are 11 proportions of fly ash and GGBS with 10% replacement of fly ash by GGBS in each combination. These 11 combinations are prepared in two sets consisting of SW-AS based samples denoted with prefix of letter M and DW-AS based samples denoted with prefix of letter D. The alkali activated paste is prepared for conducting standard consistency test, initial and final setting time tests. The alkali activated mortar is prepared for conducting compressive strength test and microstructure analysis is also performed on samples collected from compressive strength test. The experimental activities carried out for the study are detailed below.

3.1 Standard consistency and setting time tests

The standard consistency, initial setting time and final setting time tests are performed as per IS: 4031 (Part IV) (Bureau of Indian Standards, 1988) and IS: 4031 (Part V) (Bureau of Indian Standards, 1988). Seawater and distilled water-based alkali activator solutions are used for preparation of alkali activated paste with flyash and GGBS.

3.2 Compressive strength test

The alkali activated mortar cubes of 70.6mm x 70.6mm x 70.6mm were cast for 11 combinations of flyash and GGBS with both SW-AS and DW-AS. A set of 3 cubes for each combination of flyash and GGBS were cast. The demoulded cubes are kept in ambient air curing until the specific test age is reached. The cubes are tested at 3-day, 7 day and 28 days of curing age. Test is conducted on 1500KN capacity compressive testing machine. The average of compressive strength of 3 cubes is computed. The observations are discussed in detail in results section.

3.3 XRD Analysis

The cube with highest compressive strength is selected from set of 3 test specimen in each combination for XRD testing. Small pieces of fractured mortar cube sample after compressive test at 28 days age are collected. These small fragments are dipped in Isopropyl Alcohol for 2 to 3 hours to stop hydration process. The fragments are then transferred to hot air oven with temperature set to 40 degrees centigrade and oven dried for a duration of 4 to 5 hours. The oven dried fragments are finely ground to fine powder using agate motor. The powder samples are tested to determine to mineralogical composition of SW-AS and DW-AS based alkali activated mortar samples. The XRD test was performed on PANalytical EMPYREAN diffractometer using Cu - Kα (λ = 1.5405 Ǻ) radiation. The obtained peaks are search matched with peaks of nearest mineral structure and the phase identification of each sample is presented and discussed in results section. The differentiation of phase identification of each combination with SW-AS and DW-AS are shown.

4.1 Standard consistency test

The standard consistency values of alkali activated paste made of SW-AS and DW-AS are presented in Table 4. It is observed from the results that the alkali activated paste made of SW-AS requires less alkaline activator solution for standard consistency than alkali activated paste made with DW-AS. The alkali activated paste with 100% fly ash requires less alkaline activator for standard consistency than alkali activated paste with 100% GGBS for both SW-AS and DW-AS. The standard consistency trend is observed as increasing with increment of GGBS content in binder mix. A variation of 0–4% is observed in standard consistencies of DW-AS and SW-AS alkali activated paste for each combination. The usage of sea water has very little effect on consistency result when compared with conventional method of alkali activator using distilled water. This difference may be attributed due to minor alterations of chemical reactions by the minerals present in seawater during geopolymerization process.

Table 4

Standard Consistency Values for alkali activated paste (8M NaOH)
Mix Type (FA%+GGBS%)	Paste made with SW-AS	Paste made with DW-AS
F100G0	30%	30%
F90G10	31%	31%
F80G20	35%	39%
F70G30	36%	39%
F60G40	38%	39%
F50G50	38%	39%
F40G60	38%	40%
F30G70	39%	40%
F20G80	41%	41%
F10G90	41%	42%
F0G100	42%	42%

4.2 Initial and final setting time

Initial and final setting time tests are conducted after obtaining standard consistency results. As part of standard procedure for initial and final setting time test 0.85 times the percentage of standard consistency is taken, and the results are determined. The readings for initial and final setting time of different combinations of binder materials made of SW-AS and DW-AS are presented in Table 5. The setting time of binder with higher GGBS content is observed as faster for both SW-AS and DW-AS samples. The difference in initial setting time and final setting time is observed as 5 minutes to 40 minutes for SW-AS alkali activated paste and 5 minutes to 30 minutes for DW-AS alkali activated paste. The conventional flyash based alkali activated materials needed oven drying is required to reduce setting time. Similarly, the increase in GGBS has very low setting times and it can be countered by using super plasticizers to increase setting time of GGBS based alkali activated materials. Hence the combination of flyash and GGBS can be used to suit the requirement as per setting time. The present study shows setting times have no significant variation when sea water is used when compared to conventional distilled water-based alkali activator solution.

Table 5

Initial and Final setting time of alkali activated paste (8M NaOH)
Mix Type (FA%+GGBS%)	Initial setting time (Minutes)		Final setting time (Minutes)
Mix Type (FA%+GGBS%)	SW-AS	DW-AS	SW-AS	DW-AS
F100G0	240	290	285	300
F90G10	40	50	50	80
F80G20	25	25	40	40
F70G30	20	20	25	30
F60G40	15	20	20	25
F50G50	10	15	20	20
F40G60	10	10	15	15
F30G70	15	15	20	20
F20G80	15	15	20	20
F10G90	10	15	15	20
F0G100	10	10	15	15

4.3 Compressive strength

The compressive strengths at 3-Day, 7-Day and 28-Day ambient curing were recorded for 11 combinations of Fly ash and GGBS based alkali activated mortar made with SW-AS and DW-AS. It is observed that the compressive strength of Mortars increased with increase in GGBS Percentage, and the higher strength achieved at 100% replacement of GGBS in both cases. The 3-Day compressive strengths are observed in the range of 4 MPa to 60 MPa for SW-AS based alkali activated mortar cubes of binder combinations with F100 to F0G100 at 10% increment of GGBS by weight. The 3-Day compressive strengths are observed in the range of 5 MPa to 64 MPa for DW-AS based alkali activated mortar cubes of binder combinations from F100G0 to F0G100. The 3-Day strength is observed higher in DW-AS based alkali activated mortar compared with SW-AS based alkali activated mortar. The 7-Day compressive strengths are observed in the range of 6 MPa to 78 MPa for SW-AS and 7 MPa to 76 MPa for DW-AS based alkali activated mortar cubes of binder combinations from F100G0 to F0G100. The 7 Day strength is observed higher in SW-AS based alkali activated mortar compared with DW-AS based alkali activated mortar for 100% replacement of fly ash. The 28-Day compressive strengths are observed in the range of 21 MPa to 96 MPa for both SW-AS and DW-AS based alkali activated mortar cubes of binder combinations from F100G0 to F0G100. The 28 Day strength is observed equal in few combinations and lower in SW-AS based alkali activated mortar cubes. The compressive strength for mortar cubes made with SW-AS are presented in Table 6 and the compressive strength for mortar cubes made with DW-AS are presented in Table 7.

Table 6

Compressive Strength of Mortar Cubes with SW-AS (MPa) (12M NaOH)
Mix Type (FA%+GGBS%)	3 Day	7 Day	28 Day
F100G0	4	6	21
F90G10	20	28	34
F80G20	24	33	37
F70G30	24	42	45
F60G40	38	48	49
F50G50	42	56	57
F40G60	50	59	71
F30G70	54	60	71
F20G80	56	64	78
F10G90	56	70	85
F0G100	60	78	96

Table 7

Compressive Strength of Mortar Cubes with DW-AS (MPa) (12M NaOH)
Mix Type (FA%+GGBS%)	3 Day	7 Day	28 Day
F100G0	5	7	21
F90G10	22	32	38
F80G20	24	37	41
F70G30	26	40	47
F60G40	36	42	49
F50G50	40	44	52
F40G60	46	56	71
F30G70	56	62	79
F20G80	58	65	82
F10G90	60	68	88
F0G100	64	76	96

4.4 XRD Analysis

The samples for XRD testing are prepared as discussed in previous sections. XRD analysis was employed to differentiate phases formed by using SW-AS and DW-AS as alkaline activators in mortar mix of each combination. X-Ray diffraction analysis provides information about different minerals present in the powder sample. It provides atomic level characteristics in the form of a diffraction pattern. Due to unique atomic arrangement of different materials XRD phases can be used to identify various materials present in the sample. The XRD data is collected and compared with the standard crystallographic database of International Center for Diffraction Data (ICDD). The preliminary analysis shown presence of Calcite, Calcium Oxide, Gehlenite, Hematite, Hemi Carbo Aluminate, Hydrogarnet, Hydrotalcite, Magnetite, Mullite, Quartz, Rutile and Thermonatrite in alkali activated mortar samples of both SW-AS and DW-AS. Few traces of some unidentified peaks may also be present in the sample which pose negligible effect in mineral structure of alkali activated mortar. The comparative analysis of materials in F100G0, F50G50 and F0G100 is shown in Fig. 1(a) for SW-AS and Fig. 1(b) for DW-AS. The short forms of minerals are used in pictorial representation can be expanded as Mullite (Mu), Quartz (Qz), Rutile (Ru), Hemi Carbo Aluminate (HCAl), Hematite (Hem), Thermonatrite (Th), Calcite (Cal), Gehlenite, Hydrotalcite and Magnetite.

From Table 1 and Table 2 the chemical composition of Flyash, GGBS and Seawater can be observed. Silica content in flyash is higher at 57.6% and moderate in GGBS at 25.7%. Hence mineral compounds formed with silica are observed more prominent in collected samples. Since flyash and GGBS are naturally aluminum and silica rich materials the formation Mullite and Gehlenite are observed more prominently in all tested samples. Traces of Titanium and Iron in binders lead to formation of Rutile, Hematite and Magnetite. Calcium content of GGBS lead to major formation of Hydro Carbo Aluminate and Calcite. These materials indicate that carbonation occurred during curing process. Formation of Thermonatrite may also be attributed to the carbonation. Hydrotalcite is observed in most of the SW-AS samples. This might be due to the leeching of magnesium ions from sea water. The comparative analysis from XRD data for all 11 combinations made with SW-AS and DW-AS are shown in Fig. 2 to Fig. 12.

The difference in standard consistency values of alkali activated paste made of DW-AS for different combinations when compared to SW-AS based samples is within the range of 0–4% which is nominal. Hence, the sea water-based alkali activator solution is required in lesser quantity when compared to conventional distilled water-based alkali activator solution.
The setting time result indicated that there is insignificant variation in usage of seawater for preparation of alkali activator solution. However, the combination of fly ash and GGBS impacts both consistency and setting time of the alkali activated paste.
The compressive strength for SW-AS based alkali activated mortar cubes is near to DW-AS based alkali activated mortar cubes. The compressive strength variation is in the range of (-)10–0% is observed for SW-AS when compared with DW-AS based samples of all combinations.
XRD analysis shows that the effect of sea water usage has little effect in mineralogical composition of alkali activated mortar samples when compared with cube samples made with conventional distilled water-based alkali activator solution.
This study shows that mechanical properties has very little impact on using sea water as replacement for distilled water in preparation of alkaline activator solution.

Acknowledgments

The author would like to thank Department of Science and Technology (DST), Govt. of India, for the award of DST-FIST Level-1 (SR/FST/PS-1/2018/35) scheme to Department of Physics, KLEF for providing their facility to carryout XRD tests.

The author would also like to acknowledge D. Harinarayana, CEO of NISHKA Research Pvt, Ltd., Hyderabad for providing XRF and ICP-OES testing services.

Conflict of Interest - On behalf of all authors, the corresponding author states that there is no conflict of interest.

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No competing interests reported.

A study of Fly-Ash and Slag Based Alkali Activated Binder Using Sea Water Based Alkaline Activator

Status:

Version 1

Abstract

Figures

1. Introduction

2. Materials

2.1 Binder Materials

2.2 Alkaline Activating Solution

2.3 Alkali Activated Paste

2.4 Alkali activated Mortar

3. Experimental Program

3.1 Standard consistency and setting time tests

3.2 Compressive strength test

3.3 XRD Analysis

4. Experimental Results

4.1 Standard consistency test

4.2 Initial and final setting time

4.3 Compressive strength

4.4 XRD Analysis

5. Conclusions

Declarations

References

Additional Declarations

Status:

Version 1