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Article

Mix Design and Mechanical Properties of Fly Ash and GGBFS-Synthesized Alkali-Activated Concrete (AAC)

1
Department of Civil Engineering, Vignan’s Foundation for Science Technology & Research, Vadlamudi, Guntur 522213, India
2
Sree Chaitanya College of Engineering, Jawaharlal Nehru Technology University Hyderabad, Timmapur, Karimnagar 505527, India
*
Author to whom correspondence should be addressed.
Submission received: 2 March 2019 / Revised: 19 April 2019 / Accepted: 29 April 2019 / Published: 2 May 2019
(This article belongs to the Special Issue Durability and Sustainability of Concrete Mixtures)

Abstract

:
Cement is one of the construction materials widely used around the world in order to develop infrastructure and it is also one of the factors affecting economies. The production of cement consumes a lot of raw materials like limestone, which releases CO2 into the atmosphere and thus leads to global warming. Many investigations are underway in this area, essentially focusing on the eco-accommodating environment. In the research, an alternative material to cement binder is geopolymer binder, with the same efficiency. This paper presents scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis of factory byproducts (i.e., fly ash and ground granulated blast furnace slag (GGBFS)). The mix design process for the manufacture of alkali-activated geopolymer binders synthesized by fly ash and GGBFS is presented. The mechanical properties (compression, split tensile and flexural strength, bond strength) of geopolymer concrete at different mix proportions and at dissimilar curing conditions were also investigated. Geopolymer concrete synthesized with 30% fly ash and 70% GGBFS has better properties at 14 M of NaOH and cured in an oven for 24 h at 70 °C.

Graphical Abstract

1. Introduction

Worldwide cement production has grown incredibly in recent years. After fossil fuels and land-use change, it is the third biggest basis of anthropogenic emissions of CO2 (carbon dioxide) [1]. A future challenge to the construction industry is to use alternative materials to replace cement with industrial by-products [2]. In the year 1972, “Joseph Davidovits” discovered a new class of inorganic material: geopolymer binder/resin. One of the main reasons for the development of geopolymers is to utilize industrial wastes as well as to control the emission of greenhouse gases emitted by cement production. Inorganic materials-based geopolymer concrete are the same as conventional concrete but these inorganic materials should be rich in silica and alumina-like fly ash, silica fume, GGBFS (ground granulated blast furnace slag) with soluble solutions (sodium or potassium) [3,4].The main components of geopolymer concrete can be generally divided into two categories: alkaline liquids and the source materials. The alkaline activation on these industrial by-products will result in the configuration of geopolymer binders [3]. A full substitution of cement in the geopolymer concrete manufacturing with the byproduct materials reduces CO2 emissions into the atmosphere [5]. Geopolymer concrete typically shows evidence of outstanding compressive strength, restricted durability and low flexural quality, which may confine its utilization in auxiliary constructions [6]. There are so many factors affecting the mechanical and durable properties of geopolymer concrete. These are: fineness of fly ash and GGBFS, molarities of NaOH solution, and curing conditions (sunlight and oven) [5,6]. With an increase of molarities of NaOH solution, the mechanical properties are also increased. Generally up to 14 M NaOH solution is economic and it is suggested can improve the durability of geopolymer concrete [7]. Table 1 indicates the density, surface area and distribution of particle sizes of different materials like ordinary Portland cement (OPC), flyash, silica fume and GGBFS.
In this paper, the chemical composition of cementitious materials (fly ash and GGBFS) and mechanical properties like compressive, split tensile and flexural strengths of geopolymer concrete at dissimilar curing conditions are presented. Alkali-activated binders synthesized with fly ash and GGBFS and their mix proportions at dissimilar NaOH molarities are also explained. The available literature on fly ash GGBFS-synthesized geopolymer concrete was limited to sunlight or ambient or steam-curing conditions. The present study is performed to analyze the mechanical properties of fly ash and GGBFS synthesized geopolymer concrete by placing the specimens in an oven for 24 h and simultaneously curing under sunlight for 3, 7, 14 and 28 days.

Development of Geopolymers

The improvement and research of geopolymeric materials has been presented since 1930 and the distinctive research papers are accessible in this field; many researchers have investigated the development of geopolymers and Table 2 provides brief information about the authors, recent investigations on geopolymer concrete (GPC) and significance of work.

2. Material and Properties

Fly ash particles are spherical in shape, obtained from a mid-burning of powdered coal. The chemical composition of fly ash contains silica, alumina and minor measured oxides viz: Fe, Na, Ca, Mg and K. The synthetic constituents in class F fly ash are silica and alumina, both accounts for over 90% of chemical compounds present in fly ash, which was obtained by XRF (X-ray fluorescence) analysis [7,25,26]. The flyash was obtained by National Thermal Power Corporation, Vijayawada, Andhra Pradesh, India and its specific gravity value is mentioned in Table 3. GGBFS was acquired from JSW cements, Vijayawada, A.P. and India. Figure 1a,b depict the X-ray diffraction (XRD) analysis of fly ash and GGBFS samples, respectively.
Scanning electron microscope (SEM) analysis was conducted on fly ash and GGBFS samples to determine the particle size distribution. Figure 2a,b show the microscopic images of fly ash and GGBFS, respectively. The SEM images of fly ash particles depict the shape as spherical and size ranging from 14 to 23 µm, while the shape of GGBFS particles tetrahedron and size of particles range from 2 to 6 µm. Geopolymers are generally formed by the synthesis of fly ash by alkali activators [27].
Alkali-activation of alumino-silicate materials like GGBFS and fly ash is a complex process. In the present paper, fly ash was synthesized by alkaline solutions viz, sodium silicate and sodium hydroxide. The alkaline solution was prepared by mixing of NaOH pellets with water (depending on molarities) for 8 to 10 min and then mixed with sodium silicate solution. The NaOH and Na2SiO3 ratio was maintained constant at 2.5. Locally available river sand containing zone-II as per IS 383-2016, specific gravity was 2.48 (Table 3), fineness modulus was 2.20. Coarse aggregates of maximum size 20 mm were used and the fineness modulus and specific gravity were 6.97 and 2.71 respectively. Consumable water with pH value 7.11 as utilized for the geopolymer concrete preparation. In the mix of geopolymer concrete, super plasticizer was used to improve the workability of concrete by adding at different percentages. In the present work, sulphonated naphthalene based super plasticizer was used to increase the workability of GPC.

3. Mix Proportions

Standards

According to Davidovits [12], the ranges of material ratios for geopolymer concrete mixes are indicated in Table 4. The alkaline liquid to binder ratio was suggested as 0.3–0.45, and sodium silicate to sodium hydroxide solution as 2.0–2.5. Total content of aggregate in the mass of geopolymer concrete is 65–85%, and the content of fine aggregate in total aggregate volume is chosen as 30%. The range of super plasticizer is taken as 1.5–4% by mass of binder content. The extra water content if needed can be added in the range of 0.02–0.06% by mass of cementitious material.
The different materials used in the geopolymer concrete mix design are fly ash, GGBFS, sodium silicate, sodium hydroxide, fine aggregates, coarse aggregates, water and super plasticizer. The mix proportions of all these materials are carried with the base of unit weight of plain concrete (2400 kg/m3). The proportions of coarse and fine aggregates used were 70% and 30% respectively. The ratio of alkaline liquid to cementitious materials was taken as 0.35 and ratio of sodium silicate and sodium hydroxide was 2.5. Super plasticizer of 4% was used to improve the workability of fresh geopolymer concrete. The mix design of different materials is presented in Table 5 for 6 M NaOH. In a similar way, the design mixes were prepared for 8 M, 10 M, 12 M and 14 M.
The quantity and percentages of different materials for the geopolymer concrete mix is listed in Table 5 but to prepare the unit weight different materials for 1000 kg, corrections are required for coarse and fine aggregates because the absolute weight becomes 1038.82 kg. The corrections are done for unit weight of fine and coarse aggregates; we take coarse aggregate in total mass of aggregate as 1176 kg/m3 but after correction it was 1102.36 kg/m3. Fine aggregate in total mass of aggregate was 504 kg/m3, and after correction it was 475.12 kg/m3. These values are tabulated in Table 6.
The quantity of materials was prepared with the help of unit weight of those materials (corrected values are used for fine and coarse aggregates). The material quantities were prepared for 25 cubes, 12 cylinders and 4 prisms in each mix. Depending on these quantities of materials, specimens were prepared for testing purposes. All the mix design values were prepared in a Microsoft Office Excel worksheet, and these values are shown in Table 7. By doing these values in the worksheet, it will help to prepare the quantities for different molarities of NaOH, different percentages of cementitious materials (fly ash and GGBFS ratios).
Material quantity = Unit weight × Dimensions of mould × No of moulds

4. Geopolymer Binders Synthesized by Fly Ash and Ground Granulated Blast Furnace Slag (GGBFS)

Flyash and GGBFS synthesized geopolymer mortar is prepared similar to Portland cement mortar by replacing the cement with fly ash and GGBFS and water with alkaline activator solution. The word “Geopolymer” portrays a group of mineral fasteners that have a polymeric silicon-oxygen-aluminum system structure, like that found in zeolites, however without the crystal structure [28]. The geopolymerization procedure includes a significantly rapid response in the very basic form on Si-Al minerals with the intention of outcome a three-dimensional polymeric chain and ring structure comprising of Si-O-Al-O bonds. Geopolymers are regularly combined by blending industrial byproducts containing alumino-silicate and the basic arrangements. Source materials utilized are kaolinite, clays, zeolite, flyash, silica fume, slag, POFA (palm oil fuel ash), rice-husk powder, red mud and some other [29]. The majority of widely recognized antacid fluid utilized in geopolymerization is a blend of NaOH/KOH and Na2SiO3. At the point when any of the above source materials for instance fly ash (FA) in strong frame are blended by means of antacid arrangements of suitable fixation and Na2SiO3, geopolymers are shaped amid the polymerization response of fly ash [30]. Dissimilar molarities of NaOH solution (Figure 3a), fly ash percentage (Figure 3b) and GGBFS percentages (Figure 3c) for different geopolymer concrete mixes are shown in Figure 3.
The execution, including quality and strength of geopolymer concrete, are fundamentally impacted by synthesis of material mix, substance composite of a binder, salt activator, water substance, and relieving condition. The fixation and measurements of soluble base activator influence the rate of polymerization and decide the last quality of solidified geopolymer. Also, the activator molarity arrangement would influence the water content too. Hydroxyl particles (water) in activator arrangement add for the freedom of Si and Al from the geopolymer cover. All in all, geopolymerization increment with restoring time and relieving temperature (up to 90 °C) [31]. The higher modulus of elasticity is accomplished utilizing warm restoration because of a higher level of geopolymerization [32]. Amid the restoring procedure, the geopolymer solid encounters the geopolymerization procedure [33]. The type of alkaline solution plays a major role in the process of polymerization. Reactions occur at a high rate when the alkaline solution contains soluble silicate, either sodium/potassium silicate, compared to the use of only alkaline hydroxides [34].

5. Engineering Properties of Geopolymer Concrete

Higher NaOH concentrations or molarities is more powerful in dissolving fly ash particles and can result in a superior geopolymerization flyash particle. This is not only in geopolymerization but also affects the mechanical properties of geopolymer concrete. The engineering properties were calculated at different curing temperatures, dissimilar concentrations of NaOH solution and at different material (fly ash and GGBFS) proportions. All the tests were carried in different equipment like the compressive testing machine and Flexural testing machine after, the completion of curing time of 24 h in an oven at 70 °C and sunlight curing for 3, 7, 14 and 28 days, respectively the entire testing was carried according to IS 516:2013. The testing of geopolymer concrete specimens (cube, cylinder and prisms) is shown in Figure 4.

5.1. Compressive Strength

To determine the compressive strength of geopolymer concrete, 150 × 150 × 150 mm cubical moulds were used and the specimens were placed for one day (24 h) in oven at a constant temperature of 70 °C, simultaneously the specimens were further cured at sunlight for 3, 7, 14 and 28 days respectively. The effect of dissimilar molarities of NaOH solutions and different cementitious material proportions on compressive strength of GPC is shown in Figure 5.
Compressive   Strength = Maximum   failure   load   ( N ) Area   of   the   specimen   ( mm 2 )
The results depict the influence of molarity of NaOH on improving the strength of concrete. It can be obtained that the increase in molarity from 6 to 14, improved strength by 35% (average) irrespective of curing condition. It can also be also noticed that the age of curing significantly affects the strength characteristics of GPC. Out of all mixes, M5 i.e., GPC with 14 M NaOH performed better, and this was oven cured for 24 h at 70 °C followed by sunlight cured for 28 days. The results necessitate the requirement of age of curing in improving compressive strength of GPC.

5.2. Split Tensile Strength

To calculate the split tensile strength of geopolymer concrete, cylindrical moulds (150 × 300 mm) are used and the specimens have one day of oven curing at a constant temperature of 70 °C then sunlight cured for 3, 7, 14 and 28 days respectively. The split tensile strength of geopolymer concrete at these curing conditions is mentioned in the Figure 6. The geopolymer concrete mix consists of different molarities of NaOH (6, 8, 10, 12 and 14), out of all these proportions the 14 M mix (M5) achieved higher tensile strength values. The Equation (2) is used to calculate the split tensile strength of concrete.
Split   Tensile   Strength   ( MPa ) = 2 P π DL
where D and L are diameter and length of cylinder specimen.

5.3. Flexural Strength

The flexural strength of geopolymer concrete by the use of simple beam/prisms with third point loading, this procedure is commonly referred to as modulus of rupture. To determine the flexural strength of geopolymer concrete, prism moulds (100 × 100 × 500 mm) were used and the specimens underwent one day oven curing at a constant temperature of 70 °C simultaneously sunlight curing for 14 and 28 days respectively. The flexural strength of geopolymer concrete at these curing conditions is mentioned in Figure 7. The geopolymer concrete mix consists of different molarities of NaOH (6, 8, 10, 12 and 14 M), and out of all these proportions the 14 M mix (M5) was gained higher flexural strength values at 24 h in the oven (70 °C) + 28 days sunlight curing. In total, 4 beam specimens were prepared in each mix and cured for 24 h in an oven plus 3, 7, 14 and 28 days in sunlight.

6. Conclusions

The present research paper explains the mechanical characteristics of fly ash and GGBFS-synthesized geopolymer concrete with dissimilar molarities of NaOH. The conclusions obtained from the study are:
  • The GPC specimens were cast with inorganic materials (fly ash and GGBFS) and cured at a constant temperature of 70 °C for one day then further cured at sunlight for 3, 7, 14 and 28 days. In these curing conditions, the compressive strength of GPC was higher at 70 °C oven curing for 24 h as well as 28 days of sunlight curing, that is 34.15 MPa (for mix M5).
  • The maximum split tensile strength was 3.87 MPa obtained at 14 M of NaOH solution and at 70 °C oven curing for 24 h as well as 28 days of sunlight curing. Similarly, the maximum flexural strength value is 11.02 (for mix M5) at the curing of 70 °C in the oven and 28 days of sunlight.
  • The increase of molarity of NaOH solution from 8–14 M, the compressive strength, splitting tensile strength and flexural strength of GPC were increased by 33%, 26% and 42.5% respectively.
  • Oven curing at higher temperatures was not undertaken according to previous research, and it is better to consider some fiber reinforcement in the geopolymer mix for future studies to improve additional properties; the scope is there for durability analysis at different environmental conditions.
  • Geopolymer concrete one of the eco-friendly alternatives to ordinary Portland cement concrete because it utilizes less raw material. For this reason, geopolymer concrete is a strong material that provides sustainable development for infrastructural needs.

Author Contributions

Conceptualization, R.R.B. and S.R.C.M.; Methodology, R.R.B. and S.R.C.M.; Validation, R.R.B. and R.N.; Formal Analysis, R.R.B.; Investigation, R.R.B.; Resources, C.S.R.I.; Writing-Original Draft Preparation, R.R.B.; Writing-Review and Editing, C.S.R.I.; Supervision, S.R.C.M. and R.N.

Funding

This research received no external funding.

Acknowledgments

The authors thank the centre of excellence for permitting them to do XRF, XRD and SEM analysis for materials and also express gratitude to Vignan’s Foundation for Science, Technology and Research (Deemed to be University), Guntur, A.P., and India for extending support and lab facilities during the research work.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. (a) X-ray diffraction (XRD) of flyash inorganic sample, (b) XRD of ground granulated blast furnace slag (GGBFS).
Figure 1. (a) X-ray diffraction (XRD) of flyash inorganic sample, (b) XRD of ground granulated blast furnace slag (GGBFS).
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Figure 2. (a) Scanning electron microscope (SEM) image of fly ash at 50 µm, (b) SEM image of GGBFS at 20 µm.
Figure 2. (a) Scanning electron microscope (SEM) image of fly ash at 50 µm, (b) SEM image of GGBFS at 20 µm.
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Figure 3. Dissimilar molarities of NaOH solution (a), fly ash percentage (b), and GGBFS percentages (c) for different geopolymer concrete mix.
Figure 3. Dissimilar molarities of NaOH solution (a), fly ash percentage (b), and GGBFS percentages (c) for different geopolymer concrete mix.
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Figure 4. (a) Geopolymer concrete cylindrical specimens casting, (b) casting of cube specimens, (c) cube and cylindrical specimens, (d) cylindrical specimens for oven curing, (e) testing of cube for compressive strength, (f) Failure of specimens after testing.
Figure 4. (a) Geopolymer concrete cylindrical specimens casting, (b) casting of cube specimens, (c) cube and cylindrical specimens, (d) cylindrical specimens for oven curing, (e) testing of cube for compressive strength, (f) Failure of specimens after testing.
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Figure 5. Compressive strength of geopolymer concrete at different mix proportions.
Figure 5. Compressive strength of geopolymer concrete at different mix proportions.
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Figure 6. Split tensile strength of geopolymer concrete at different mix proportions.
Figure 6. Split tensile strength of geopolymer concrete at different mix proportions.
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Figure 7. Flexural strength of geopolymer concrete at different mix proportions.
Figure 7. Flexural strength of geopolymer concrete at different mix proportions.
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Table 1. Particle size distribution, Specific surface area and density data of cement and industrial byproducts [8].
Table 1. Particle size distribution, Specific surface area and density data of cement and industrial byproducts [8].
Cement and Industrial ByproductsDensity (g/cm3)Specific Surface Area (m2/g)Particle Size Distribution (mm)
OPC (type I) (I33)3.120.851.1–50
Class F flyash (G 05)2.450.72.0–40
Granulated blast-furnace slag (G42)2.90.750.70–40
Silica fume (G-15)2.0518.020.1–5.0
Table 2. Development of geopolymers and their significance.
Table 2. Development of geopolymers and their significance.
AuthorYearSignificance
Davidovits [9]1972Discovery of Geopolymers
Davidovits [10]1989Geopolymeric new materials
Davidovits [11]1994Geopolymer cements
Davidovits [12]2002Successes and Failures in Geopolymer Applications
P. Duxson et al. [13]2006Current state of the art
Peter Duxson et al. [14]2007Geopolymer technology in the development of green concrete
Komljenovi M et al. [15]2010Microstructural properties
Kong DLY and Sanjayan JG [16]2010Structural composites for high temperatures
PetrSazama et al. [17]2011Geopolymer based catalysts
Jannie S.J. van Deventer et al. [18]2011Geopolymer cement
Davidovits [19]2013Foundry Resins (Nano-poly (Silaxilanol))
Zuhua Zhang et al. [20]2014Geopolymer foam concrete
Yun Yong Kim et al. [21]2014Durability Performance
Sara Dashti [22]2015Use of Lake Michigan Dredged Materials
Dr. Konstantin Sobolev et al. [23]2015Optimized Concrete Pavement
Naskar and Chakraborty [24]2016Nano materials in geopolymer concrete
Table 3. Specific gravity and density of different materials.
Table 3. Specific gravity and density of different materials.
MaterialsSpecific Gravity
Coarse aggregate2.71
Fine Aggregate2.48
Fly ash2.1
Ground Granulated Blast Furnace Slag2.22
Density of Sodium Silicates 1.53
Sodium Hydroxide1
Water 1
Super Plasticizer2.12
Table 4. Standards of materials used in geopolymer concrete mixes.
Table 4. Standards of materials used in geopolymer concrete mixes.
MaterialsRange
Alkaline liquids/Binder 0.3–0.45
Sodium silicate/sodium hydroxide2.0–2.5
Water/Binder0.16–0.24
Total aggregate in mass of concrete65–85%
Fine aggregate content in total aggregate30%
Added water content0.02%–0.06% of mass of cementitious material
Super Plasticizers1.5%–4% of mass of cementitious material
Table 5. Mix design of different materials per cubic meter (6 M NaOH).
Table 5. Mix design of different materials per cubic meter (6 M NaOH).
Materials usedQuantity
Unit weight of concrete2400 kg/m3
Percentage of aggregate in total mass of concrete70%
Aggregate content in total mass of concrete1680 kg/m3
Percentage of fine aggregate in total mass of aggregate30%
Fine aggregate in total mass of aggregate504 kg/m3
Coarse aggregate in total mass of aggregate1176 kg/m3
Cementitious materials used
Ratio of alkaline liquid to cementitious material0.35
Mass of Cementitious material and alkaline liquid720 kg/m3
Mass of Cementitious material 533 kg/m3
Mass of alkaline liquid187 kg/m3
Fly ash (30%)159.9 kg/m3
GGBFS (70%)373.1 kg/m3
Alkaline liquids required
Ratio of sodium silicate and sodium hydroxide 2.5
Mass of sodium hydroxide53 kg/m3
Mass of sodium silicates134 kg/m3
Water required in Sodium silicate
Na2O15.30%
SiO233.69%
H2O51.01%
Water content in sodium silicate69 kg
solids content in sodium silicate65 kg
Water required in sodium hydroxide
Molarity ratio6
Mass of NaOH solids240 gm
NaOH24%
H2O76%
Solid content in sodium hydroxide13 kg
Water content in sodium hydroxide40 kg
Total water content 109 kg
Total solid content611 kg
Water to cementitious material ratio 0.178
Super plasticizer requirement
Super plasticizer4%
Mass of super plasticizers24.44 kg/m3
Percentage of extra water content1%
Extra water content5.33 kg/m3
Table 6. Absolute unit weights and corrected unit weight of the materials.
Table 6. Absolute unit weights and corrected unit weight of the materials.
MaterialAbsolute Weight of MaterialMaterialAbsolute Weight of Material
Coarse Aggregate (CA)433.94 kgStandard weight1000 kg
Fine Aggregate (FA)203.22 kgDifference 38.82
Fly ash76.14 kgCoarse Aggregate Difference27.17
GGBFS168.06 kgFine Aggregate Difference11.64
Sodium Silicates87.58 kgCoarse Aggregate corrected406.77
Sodium Hydroxide53 kgFine Aggregate corrected191.58
Water 5.33 kgUnit weight corrected CA1102.36 kg/m3
Super Plasticizers11.52 kgUnit weight corrected FA475.12 kg/m3
Absolute Weight1038.82 kgWater to cementitious material ratio0.178
Table 7. Mix proportions weight of all materials for 25 cubes, 12 cylinders and 4 prisms.
Table 7. Mix proportions weight of all materials for 25 cubes, 12 cylinders and 4 prisms.
Materials (kg)M1 (6M NaOH, 30% GGBS & 70%FA)M2 (8M NaOH, 40% GGBS & 60%FA)M3 (10M NaOH, 50% GGBS & 50%FA)M4 (12M NaOH, 60% GGBS & 40%FA)M5 (14M NaOH, 70% GGBS & 30%FA)
Coarse aggregate132.26132.26132.26132.26132.26
Fine aggregate57.0157.0157.0157.0157.01
Flyash44.8738.4632.0525.6419.23
GGBFS19.2325.6432.0538.4644.87
Mass of sodium silicate7.817.817.817.817.81
Total water content in sodium silicate8.298.298.298.298.29
Total sodium silicate16.1116.1116.1116.1116.11
Mass of sodium hydroxide 1.562.042.643.123.6
Total water content in sodium hydroxide4.814.333.723.242.76

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Bellum, R.R.; Nerella, R.; Madduru, S.R.C.; Indukuri, C.S.R. Mix Design and Mechanical Properties of Fly Ash and GGBFS-Synthesized Alkali-Activated Concrete (AAC). Infrastructures 2019, 4, 20. https://0-doi-org.brum.beds.ac.uk/10.3390/infrastructures4020020

AMA Style

Bellum RR, Nerella R, Madduru SRC, Indukuri CSR. Mix Design and Mechanical Properties of Fly Ash and GGBFS-Synthesized Alkali-Activated Concrete (AAC). Infrastructures. 2019; 4(2):20. https://0-doi-org.brum.beds.ac.uk/10.3390/infrastructures4020020

Chicago/Turabian Style

Bellum, Ramamohana Reddy, Ruben Nerella, Sri Rama Chand Madduru, and Chandra Sekhar Reddy Indukuri. 2019. "Mix Design and Mechanical Properties of Fly Ash and GGBFS-Synthesized Alkali-Activated Concrete (AAC)" Infrastructures 4, no. 2: 20. https://0-doi-org.brum.beds.ac.uk/10.3390/infrastructures4020020

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