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Article

Evaluation of Aloe barbadensis Miller and Musa x paradisiaca as Internal Curing Agents in Concrete

by
Ramalingam Malathy
1,*,
Balakrishnan Selvam
2 and
Mayakrishnan Prabakaran
3,*
1
Department of Civil Engineering, Sona College of Technology, Salem 636005, Tamil Nadu, India
2
Department of Civil Engineering, EASA College of Engineering & Technology, Coimbatore 641105, Tamil Nadu, India
3
Department of Crop Science, College of Sanghuh Life Science, Konkuk University, Seoul 05029, Republic of Korea
*
Authors to whom correspondence should be addressed.
Sustainability 2023, 15(4), 3591; https://doi.org/10.3390/su15043591
Submission received: 30 December 2022 / Revised: 7 February 2023 / Accepted: 12 February 2023 / Published: 15 February 2023
(This article belongs to the Section Sustainable Materials)
Browse Figures
Versions Notes

Abstract

:
Curing is essential for enhancing the durability and strength of concrete. Researchers found that a lack of conventional curing in earlier days leads to a loss of economy over the years after construction finishes. Self-curing concrete is a contemporary type of concrete that holds water, prevents loss of moisture from the surface, and facilitates self-curing. The existing chemical admixture for self-curing, polyethylene glycol (PEG), is expensive. Hence, in this research, bio admixtures such as Aloe barbadensis miller and Musa x paradisiaca were tried as self-curing agents and compared with the performance of PEG. The functional groups of such bio admixtures match with those of PEG. The results show that the fresh and hardened properties of M30 concrete are better than the conventionally cured concrete and PEG added to concrete. The optimized percentages of admixtures are 0.25% for Aloe barbadensis miller, 1% for Musa x paradisiacal, and 0.5% for PEG, improving the compressive strength by 23.3%, 1.7%, and 4.5%, respectively. Similarly, split tensile and flexural strength have been enhanced up to 4.24 MPa and 15.05 MPa for Aloe barbadensis miller, and 3.82 MPa and 13.65 MPa for Musa x paradisiacal. The characterization studies’, such as XRD (X-ray diffraction), SEM (scanning electron microscope), and EDX (energy dispersion analysis), results show the early formation of hydrated products, such as CSH and CH, after 7 days of curing with an optimized mix. Of the two plant extracts, Aloe barbadensis miller performed better than Musa x paradisiacal and water-cured concrete.

1. Introduction

In historical structures, lime and cement were the only individual construction materials. The manufactured material of cement has more binding properties than the naturally available lime stone powders used as building material [1,2]. Portland cement concrete, the most popular artificial composite material on Earth, was used to build civilizations a few decades ago. Due to its excellent mechanical properties, it is the most commonly used building material globally [3]. Given cost savings, environmental protection, and resource conservation, the inclusion of mineral additives in cement has continued to expand, as has the emergence of concrete research [4]. Concrete needs to have sufficient moisture content for the hydration of cement particles, which enhances the binding properties of other ingredients, which leads to obtaining the required strength and other properties [5]. Numerous advantages have been achieved with high-performance concrete (HPC), such as its light weight, superior strength, and longevity [6,7]. HPC requires more attention during material selection, casting, and curing. Concrete starts to gain strength via time extension after placing fresh concrete. Continuous curing influences volume stability, freeze and thaw resistivity, and delays drying shrinkage. Another name for conventional curing is external curing, which will be achieved after the selection of material, mixing, placing, compaction finishing, and after the final setting time of fresh concrete [8]. To achieve the desired characteristics, HPC cannot be satisfied with conventional curing. This restriction has induced interest in finding alternate curing methods and other concrete-strengthening forms. The idea of producing concrete without water curing was created to decrease the water evaporation in masonry and boost the water efficiency in concrete compared to that of the traditional method [9].
Aggregates are essential to concrete’s impact strength, thermal absorption, and elastic properties, along with its dimensional stability and volume stability. Riverside natural fine aggregate is banned in most of the states of India due to over-exploitation creating severe environmental burdens and problems in the groundwater table [10]. This involves highly expensive hydrates continuously in transportation and long-term creation of concern to the bridge piers. Alternatively, manufactured sand (M-sand) is a supply source of fine aggregates by grinding rocks obtained from crushers. The chemical characteristics and strength of manufactured sand (M-sand) are similar to those of river sand [11,12]. In the crushers, large quantities of dust, usually measuring less than 150 microns, are generated. Water-washed granular particles should satisfy IS: 383 (1970). To conserve natural resources, TNPCB licensed new manufacturing of sand (M-Sand) quarries in consecutive years. Compared to natural sand, M-sand is cheaper [13,14,15].
The long-term performance of concrete structures depends primarily upon adequate curing. Maintenance of satisfactory moisture content in concrete is called curing; after the final setting time of concrete, to develop the desired property, curing has to be performed. If curing is improperly carried out, there will be a water shortage, which will result in inadequate hydration, poor strength growth, and decreased durability [16]. Good curing is only sometimes possible due to many reasons such as artistry, the bottom of the roof, the exterior of commercial high-rise structures’ economy, and time of inevitable on-site construction of bridges and tunnels, etc. Curing enables cement to continuously hydrate, increasing concrete’s strength [9,17]. Researchers across the world are engaged in solving the use of maximum potable water in consultation work without sacrificing quality. Self-curing is a method to maintain water content in concrete to effectively hydrate the cement and decrease self-desiccation. The various compound materials can offer interior reservoirs such as shrinkage-reducing admixtures, lightweight aggregates and super absorbent polymers [18,19].
When preparing concrete, shrinkage-reducing admixture (SRA) of a soluble compound was added to reduce the evaporation of water when the concrete is exposed to freeze-drying [20,21]. Ingredients of self-curing are utilized to decrease water loss from concrete surfaces. The critical parts of shrinkage-reducing admixtures are ethylene glycol derivatives. When compared to the majority of ordinary admixtures, which are water-based solutions, these organic liquids are completely different [22]. The early and long-term drying shrinkage can be significantly decreased when such an additive is introduced to concrete during the batching stage. It means that cement hydration and the creation of polymer films are two processes that chemicals should contain. That soluble chemical must be in either the [-OH] or the [-O-] functional groups. Polymers in concrete have a C–O bond and an O–H bond. Ethers are suitable solvents because of their low reactivity [23].
Plant extractions are added as an admixture of bio-curing substance in fresh concrete. Ingredients can avoid early-age cracking to avoid temperature effects [22,24,25]. Recent researchers found that the direct use of the following extractions provides satisfactory results: Spinacia olaracea, Calotropis gigantea, water hyacinth, arrowroot extractions, Aloe vera, banana stem, etc. The appearance of surface tension leads to the retention of water in concrete molecules even at ambient temperature transfer [26,27,28]. Musa acuminate is cultivated in South Asia, and the Musa x balbisiana is an ancestor of the modern cultivated banana tree. Musa species are used as food plants by humans and some animals. The plant is ready to flower, and a tree stem grows up through the sheath and drops back toward the ground. In India, almost every part of a plant is used either for food or wrapping food [29,30].
The scientific name of the banana tree is Musa x paradisiaca (also called Banana Pseudo Stem), a hybrid between Musa acuminate and Musa balbisiana. Musa x paradisiaca is used for a variety of health benefits such as detoxification and digestion, treating kidney stones, managing cholesterol, healing acidity, and solving gastric problems, etc. The outer layer of the stem is a fibrous, green sheath that is inedible and tough to remove. The central core is sliced into small pieces and made into juice with the help of a jar mixer in the kitchen. The Musa x paradisiaca tree stem core cell fibre has a diameter of approximately 10 μm, fineness of 2400 Nm, and length-to-depth ratio of 450. Compared to ramie and bamboo fibre, the texture and spinnability of this fibre are significantly better. It is a robust fibre with a good capacity for absorbing moisture and a decreased strain density at the break. It quickly absorbs moisture and releases it. It was found that internal curing can increase the toughness of concrete [31,32,33].
The Aloe barbadensis miller (also called Aloe vera) plant leaf can be divided into two major parts: outer green skin and colourless inner gel [34]. The leaf contains 99% water inside the gel and 1% solid materials such as minerals, vitamins, enzymes, organic acids, phenolic compounds, and polysaccharides. The natural product Aloe barbadensis miller is widely utilized in the cosmetology industry. Despite a variety of indications for use, controlled trials are necessary to ascertain its true efficacy [35]. Aloe vera obtains its name from the Arabic for “shinning bitter substance”, while vera is the Latin word for “true”. Once the leaf has been peeled, you will see the natural Aloe barbadensis miller gel; using a spoon, scoop it into a blender until frothy and liquefied. Aloe barbadensis miller is antimicrobial in many pharmaceutical applications [36,37].
This research paper deals with the two abovementioned plant extracts, namely Aloe barbadensis miller and Musa x paradisiaca, as bio admixtures for self-curing and compared with the performance of a chemical admixture called PEG. The objective is to optimize the dosages of the admixtures as partial replacement of water from the slump test and compressive strength test of M30 grade concrete. Microstructural and spectral analyses of self-curing concrete with bio and chemical admixtures are to be obtained after 7, 14, and 28 days and compared with conventional water-cured concrete.

2. Materials and Methods

2.1. Materials

OPC 53 grade cement, as per IS:12269 (1987), was used throughout this experiment. Well-graded fine aggregate passing through 4.75 mm and coarse aggregate of 20 mm, and downsize blue metals confirm the IS:383 (2016) standards.
Internal curing agents such as bio admixtures, namely Aloe barbadensis miller gel and Musa x paradisiaca stem extract, were taken for experimental work and compared with the performance of the chemical admixture polyethene glycol (PEG-4000). PEG is sometimes referred to as poly-oxy-ethylene (POE) or polyethylene oxide (PEO). The general formula, H-[OCH2CH2]n-OH, has a low molecular weight condensation polymer of ethylene oxide, where n is the usual range between 4 and 180 (approximately) for the average number of repeated oxyethylene groups. Its pH is 5.0–7.0 and its density is 1.12 g/cm3 [38,39,40]. The characteristics of the raw materials employed in this research are shown in Table 1 below.

2.2. Spectra Analysis of Admixtures

A GC-MS analysis was performed to identify the complex mixtures and for determination of the organic compounds present in admixtures. In this analysis availability of hydroxyl groups (-OH) present in bio admixtures, the Aloe barbadensis miller, Musa x paradisiaca, and chemical admixture polyethylene glycol show a water-holding capacity in concrete. Molecular hydrogen bonding and van der Waals interactions between nearby molecules contribute to the crystalline structure of sample admixtures. Functional groups such as hydroxyl, ethyl, and methyl groups are necessary to enhance the bonding property of a cement particle [41,42]. Table 2 shows functional compound names and formulas of chemical and bio admixtures and their roles in concrete.
Table 2 describes the functional group of admixtures and their role in concrete.

2.3. Mix Design

Concrete is a heterogeneous material, whereas concrete mix design creates the foundation for sound infrastructure. It involves various code provisions to create an economical design. High-performance concrete strength requirements are to be satisfied at least with the M30 grade of concrete. The selection of suitable ingredients for concrete composition and the determination of their relative proportions were carried out to produce concrete of the required strength and durability. The following material quantities are arrived at based on the principal codes of IS: 456 (2000) and IS: 10262 (2009) and the mix proportioning shown in Table 3. The material proportions were taken according to mass. During mixing, 10% of the total weight was added as a backup for materials that would loosen up. A chemical admixture PEG and bio admixtures of Aloe barbadensis miller gel and Musa x paradisiaca tree stem extract enhanced the hydration property.
Assumed target mean compressive strength=38.25 MPa
Maximum size of aggregates=20 mm
Water–cement ratio=0.45

2.3.1. Fresh Concrete Properties

Based on the fundamental properties of concrete materials, the mix proportion was calculated by adopting IS: 10262 (2009). Slump cone tests were performed to study the workability of each mix in the laboratory as per IS: 456 (2000). The following percentage of admixtures were tried in M30-grade concrete specimens, such as 0.25%, 0.5%, 0.75%, 1.0%, 2.0%, and 5.0% according to the weight of cement. While mixing, the liquid bio admixture is partially replaced for total water content to maintain the same w/c.

2.3.2. Hardened Concrete Properties

The internally cured concrete specimens were left at room temperature to self-cure. Samples were prepared to perform compressive strength tests (150 mm cube), split tensile tests (150 mm dia and 300 mm height cylinder), and flexural strength tests (100 mm × 100 mm × 500 mm prism) at 7, 14, and 28 days of curing. After the specified duration of concrete curing, specimens are taken to test under a compression testing machine (CTM) of 200 T using various testing procedures such as flexural, compressive, tensile strength, and weight loss tests as per IS:516 (1959). The performance of concrete varies based on several reasons, such as water as binder ratio, type of cement and aggregates, admixtures, environmental exposure, etc. [43]. The casting of all specimens took place at the average ambient temperature of 27 °C. The larger weight of a standard cube means a higher density of the concrete. Concrete weight depends primarily on its cement content and secondly, on the variation of quarrying aggregate [43,44]. Since cement has the largest specific gravity among other ingredients. higher cement content produces a larger density and maximum compressive strength. Each cube is weighed after 28 days of conventional and air-curing under shade before being taken to a mechanical strength test. Individual specimens of cube, cylinder, and prisms of each dosage in the admixture do not vary more than 15% according to the weight of concrete in comparison with all other specimens.

2.4. Microstructure Studies

2.4.1. SEM/EDX

Evaluation of surface fractures, defects, pollutants, or corrosion can be performed using SEM (scanning electron microscope) images. An analysis of the mechanical strength of specimens was carried out after different curing conditions. Concrete specimens with conventional curing and specimens with internal curing admixtures after 28 days were dried and powdered into a particle size of 1 mm. Powdered concrete samples are kept under field emission scanning electron microscope Thermo Fisher FEI QUANTA 250 FEG to study the morphological characteristics of concrete. This equipment operates in high-vacuum conditions with a high resolution of 1.2 nm. SEM image helps to visualize the microstructure of the hydrated cement particles. An elemental analysis and chemical composition analysis method connected to an electron microscope is called energy dispersive X-ray (EDX). The surface is exposed to a focused X-ray beam or a high-intensity beam of charged particles to promote X-ray emission. A certain ingredient will be more prevalent at that place or region of interest if it is present there in greater quantity [45,46].

2.4.2. Thermogravimetric Analysis (TGA)

As a consequence of the thermogravimetric study, it was discovered that the temperature caused mass loss and component disintegration. The TGA revealed that there are numerous weight losses. The thermogravimetric analysis (TGA) model SDT Q600 measures the weight of a sample when it is heated in a furnace. The sample pan (made up of aluminium) is supported by precision balance. In a furnace, the sample mass is monitored while it is gradually heated during the experiment [47].

2.4.3. X-ray Powder Diffraction (XRD)

A quick analytical method called X-ray powder diffraction, or XRD, can reveal details about the dimensions of unit cells while being employed primarily to determine a crystalline material’s phase. Bruker D8 Advance was used to find the results. At room temperature, samples are scanned on a continuous mode from 100 to 900 with a scanning rate of 2 deg/min. XRD studies graph indicates the intensity versus diffraction, with 2θ for non-leaching samples [44,47].

3. Results and Discussions

3.1. Fresh Concrete Properties

The design mix was arrived at based on the properties of the ingredients. After the dry mix of ingredients, admixtures are thoroughly stirred with water before the concrete preparation addition. The increase in the water–cement ratio greatly improves workability on fresh concrete but affects its durability [48]. Hence, the admixtures are incorporated in liquid form as a partial replacement for water from 0 to 1% with an increment of 0.25%, 25 and 5%. The corresponding slump values are recorded for bio and chemical admixtures and plotted in Figure 1 and it shows that 5% of Aloe barbadensis miller admixture gives a maximum slump value of 132 mm. However, Musa x paradisiaca stem core extract and PEG admixtures of 5% addition of sample give 114 mm and 100 mm, respectively. In addition for Musa x paradisiaca tree stem core extract (120 mm) and PEG (118 mm), the maximum slumps are found at the lowest percentage of 0.25% admixture. Concrete specimens with 2% and 5% PEG results showed the final settling time of concrete around 36–72 h. From Figure 1, it was observed that 0.25% of all three admixtures as partial replacement of water provides better workability. By increasing the dosage, the slump value is reduced due to the presence of some solid content in the admixtures, but satisfies the requirement as per IS 456 (2000). Hence, the optimum dosage of admixtures needs to be determined from compressive strength results.

3.2. Strength Properties of Concrete

Figure 2a shows the compressive strength of concrete specimen added Aloe barbadensis miller, Musa x paradisiaca tree stem core extract, and PEG. The result in comparison to conventional concrete [35.11 N/mm2] is higher than or equal to that of bio admixtures and chemical admixtures. Aloe barbadensis miller-based concrete of 0.25% admixture shows 23% higher compressive strength than conventional concrete. Musa x paradisiaca tree stems core of 1.7% and chemical admixture PEG 4.5%, on the other hand, improved compressive strength tested for 1% and 0.5% admixtures, respectively.
The split tensile strength test results of concrete specimens are shown in Figure 2b. Admixtures of 0.75% Aloe barbadensis miller-based concrete specimen provide 4% increased split tensile strength. In other cases, 0.25% Musa x paradisiaca tree stem core and 0.5% PEG-based concrete specimens give 6% and 2.5% decreased split tensile strength. Figure 2c displays the effect of 28 days of flexural strength on the concrete prism with different percentages of admixtures. While Aloe barbadensis miller showed a 11.6% increase in strength with 0.75% admixture, it only increased by 2.5% in Musa x paradisiaca tree stem core with 0.25% admixture. On the other hand, PEG shows a 1.7% reduction in flexural strength with the addition of 0.5% admixture concrete compared to conventional concrete. The enhanced strength of the bio admixture-cured concrete over the conventionally cured concrete is due to the homogeneous mixture results in the complete hydration of cement particles during the hydration process, in which admixtures release their hydroxyl or ether constituents. The property of achieving strength through air-curing results in the high performance of bio admixtures. As mentioned in the microscopic analysis, internally stored water facilitates the hydration of cement whenever it is required [45,49].

3.3. Optimum Dosage of Admixtures

The optimum dosage of bio admixtures and chemical admixtures was determined from workability measurements and compressive strength studies. According to IS:456 (2000), the slump value of the concrete used in ordinary reinforced cement concrete (RCC) work is 50–100 mm. From Figure 1, it was observed that the incorporation of bio admixtures in liquid form by maintaining the same water–cement ratio fulfils the requirement for minimum slump value of different concrete mixes. The higher compressive strength indicates that the admixtures are optimal. The admixtures of Aloe barbadensis miller 0.25%, Musa x paradisiaca tree stem core 1.0%, and polyethylene glycol 0.5% produced the maximum compressive strength. Figure 2a represents the results of compressive strength on different admixtures; the percentage of admixtures mentioned above is optimal. It was found that concrete prepared with bio admixtures increased its strength more rapidly than conventional concrete. Hence from Figure 2 and Figure 3, the optimum dosage of Aloe barbadensis miller is 0.25%, Musa x paradisiaca is 1% and PEG is 0.5% to attain the required workability and strength.

3.4. Microstructure Studies

3.4.1. SEM/EDX

Microstructure studies such as SEM and EDX were performed on the concrete samples collected after 7, 14, and 28 days of curing. SEM images of concrete powder samples collected after 7 days of conventional curing, as well as internal curing with admixtures, is shown in Figure 4a–d, respectively. Figure 4d shows that water-immersed curing converts cement particles into CH and CSH after hydration and few places show the crystalline structure of ettringite. Figure 4c PEG-based concrete microstructure shows ettringite in the greatest quantity, whereas Figure 4b Musa x paradisiaca tree stem core extract-based cement concrete microstructure shows a smaller amount of ettringite, Figure 4a also shows continued hydration with less formation of CSH, ettringite exists. The microstructure study of Figure 5 represents 14 days results in better hydration performance of cement particles as compared to Figure 4. As shown in Figure 6 the formation of calcium hydroxide (CH) represents hydration initiation, however, the process still has to continue for the maximum duration. The curing of concrete microstructure takes 28 days, representing a transformation of the cement molecule into calcium silicate hydrate (CSH). Moisture is retained inside concrete specimens by a uniform blend of admixture. This prevents the evaporation of moisture and helps to cure to occur as soon as necessary after the required curing period [45,50].

3.4.2. XRD

Figure 7 represents the results of energy dispersive X-ray (EDX) spectrophotometry at 7 days. EDX provides the list of elements present in the concrete powder as follows: oxygen (O), silica (Si), calcium (Ca), aluminium (Al), sodium (Na), potassium (K), manganese (Mg), nitrogen (N), etc. Moisture levels in early-age concrete are the highest, followed by those of silica and calcium in lesser quantities. During hydration, cement reacts with water from capillary pore spaces to precipitate hydration products. During the curing process, it is possible for the system to self-desiccate if it has no access to shallow water. This can be viewed int the consecutive Figure 8 and Figure 9. Figure 8 shows that the presence of oxygen is less in weight, as well as an increase in silica and calcium content. At 28 days, the compressive strength of Figure 9 shows the presence of a high quantity of calcium and silicate. Since the system’s relative humidity (RH) reduces as the reaction continues, self-desiccation occurs. In the energy dispersive X-ray analysis, increasing time duration and decreasing oxygen content in concrete particles increases strength. Moreover, it shows the formation of C-S and CSH.
Figure 10A illustrates the predominant hydration process of samples that started and form CSH gel. The diffraction angle 2θ with sharp peaks indicates the presence of ether and hydroxyl groups. A height of 2θ = 29.46 accelerates the presence of tricalcium silicate into calcium aluminium silicate hydrogen. A few places of the sample in the micro level indicate the incomplete hydration process through the availability of ettringite—sample specimen core area of particles took a longer time to react with H2O. The findings from XRD supported by the SEM analysis for the sample appear to be flakes and layer-like materials. Self-curing of specimen expels few peaks over hydration of cement components. Peaks at 2θ = 200–300 observed in Figure 10B show the formation of CH and CSH in relatively all parts of the concrete specimen. C2S and C3S react with water molecules to enhance the hardened concrete properties. The diffract grams in Figure 10C confirm the calcite presence at 2θ = 290–300, which is attributed to the diffusion of atmospheric oxide gas and internal water holding resolves the hardened concrete specimen. Formation of Ca(OH)2 shows the improved hardened concrete strength via internal water reaction with all parts of cement. In Figure 10D, XRD represents the sample of chemical admixture in the self-curing process. Holding moisture around cement particles in concrete mixing plays a significant role in supporting the hydration process. Plot XRD indicates that the hydration process of concrete was completed, and the complex compound CSH and CH was formed [47,51].

3.4.3. Thermogravimetric Analysis/Differential Thermal Analysis

Using TA instruments, CSH and CH were investigated using thermogravimetric analysis (TGA) in concrete specimens treated with concrete-curing admixtures. At the end of the 28 days, hardened concrete samples were crushed into powder and then sieved through a 75 µm sieve. A pure nitrogen-based atmosphere was used to heat mixture-based concrete specimens up to 900 °C at a heating rate of 20 °C/min. The hydrated cement lost weight until the 200 °C bandwidth, representing the water loss from the CSH layer. Decomposing CH reduces weight loss from 400 °C to 500 °C. Thermal degradation occurred between the temperature ranges of 600 °C and 800 °C when de-carbonizing calcium carbonate (CaCO3). At some stage in the hydration system, CH continuously formed for an extraordinary while. The thermogravimetric analysis (TGA) graph shows that in Figure 11, Aloe barbadensis miller-based concrete shows good resistance to heat of 0.72% (350 °C to 550 °C) with increased exposure compared to conventional concrete. At the same time, Musa x paradisiaca and PEG-based samples have decreased the weight loss maximum of 1% from 400 to 650 °C after 28 days. The differential thermal analysis (DTA) curve for hydrated cement particles observed continuous weight loss in the range of 80 °C–250 °C. The DTA curve allows us to identify different decomposition processes as observed in Figure 12. Additionally, weight loss associated with the combined water of calcium silicate hydrates (peak-a), ettringite (peak-b) calcium aluminate hydrates (C4AH13) and calcium aluminium hydrates (C2ASH8) (peak-c) are identified. The weight loss of temperature ranges 520–600 Temp (peak-d) is related to the dehydroxylation of portlandite. Moisture engaged via cement particles completes the hydration progress, which directly impacts the strength properties of concrete [52,53].

3.5. Mechanism

Enhancing cement hydration is the primary goal of curing concrete to achieve the appropriate strength [47,48]. In conventionally fixed concrete, the process involves supplying water from outside to reach the interior parts of the concrete specimen to make up for the mixed water that evaporates. However, based on the curing techniques, complete hydration may only happen on some cement particles because sufficient water may not be available for hydration. Due to the formation of a gel shield on the surface of water molecules in concrete, when adding a bio additive of unmodified Aloe barbadensis miller gel extract during the mixing of concrete, it can store water. When mixing, the liquid from the Musa x paradisiaca tree stem core holds the combined water and provides water for hydrating the cement. Due to the fact of both types of natural plants contain ether [-O-] or hydroxyl [-OH-] functional groups [53]. Concrete is internally cured more effectively with these natural bio admixtures because of their ability to store water. Figure 13 illustrates the mechanism of bio-curing agents holding water to facilitate the internal curing of concrete.

4. Conclusions

In this research, two plant extracts, namely Aloe barbadensis miller and Musa x paradisiaca, have been tried as self-curing agents and their performance in M30-grade concrete has been compared with the performance of PEG and water-cured concrete. From the experimental results, the optimum compressive strength was obtained as 1.0% Musa x paradisiaca stem extraction (35.7 N/mm2), 0.25% Aloe barbadensis miller extract (43.3 N/mm2), and 0.50% Polyethylene glycol (36.7 N/mm2) according to the weight of cement. Of the two plant extracts, Aloe barbadensis miller (23.36%) performs better than conventionally cured concrete samples. The performance of two bio admixtures is significant compared to PEG without compromising the workability and strength of conventionally cured concrete. Since the water–cement ratio is maintained with the incorporation of bio admixtures, the durability properties of concrete will not be affected. Development of these bio admixtures is a boon for concrete construction, which is a green solution for water and labour scarcity. Studies on the durability and structural behaviour of precast concrete elements need to be conducted in the future for further recommendations.

Author Contributions

R.M.: software, investigation, formal analysis, resources, writing—original draft, visualization; B.S.: software, methodology, resources, data curation, writing—original draft, M.P.: investigation, resources, data curation, writing—original draft, writing—review and editing, supervision, project administration, funding acquisition. 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

Not applicable.

Conflicts of Interest

The authors declare no conflict of interest.

Abbreviations

UV-VisibleUltra Violet visible
FT-IRFourier-Transform Infrared Spectroscopy
GC-MSGas Chromatography-Mass Spectrometry
SEMScanning Electron Microscope
EDXEnergy Dispersive X-ray
XRDX-ray Diffraction
TGAThermogravimetric Analysis
DTADifferential Thermal Analysis
PEGPolyethylene Glycol
TNPCBTamilnadu Pollution Control Board
FAFine Aggregate
CACoarse Aggregate
RCCOrdinary Reinforced Cement Concrete
CHCalcium Hydroxide
CSCalcium Silicate
CSHCalcium Silicate Hydroxide
RHRelative Humidity

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Figure 1. Slump values of concrete with admixtures at various dosages.
Figure 1. Slump values of concrete with admixtures at various dosages.
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Figure 2. (a). 28 days compressive strength of concrete cube. (b). 28 days split tensile strength of concrete cylinder. (c). 28 days flexural strength of concrete prism.
Figure 2. (a). 28 days compressive strength of concrete cube. (b). 28 days split tensile strength of concrete cylinder. (c). 28 days flexural strength of concrete prism.
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Figure 3. Optimization of dosage of admixtures w.r to compressive strength. (A) Aloe barbadensis miller stem, (B) Musa x paradisiaca pseudo stem, (C) polyethylene glycol.
Figure 3. Optimization of dosage of admixtures w.r to compressive strength. (A) Aloe barbadensis miller stem, (B) Musa x paradisiaca pseudo stem, (C) polyethylene glycol.
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Figure 4. SEM images 7 days. (a) Aloe barbadensis miller, (b) Musa x paradisiaca tree stem, (c) PEG, and (d) conventional.
Figure 4. SEM images 7 days. (a) Aloe barbadensis miller, (b) Musa x paradisiaca tree stem, (c) PEG, and (d) conventional.
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Figure 5. SEM images 14 days. (a) Aloe barbadensis miller, (b) Musa x paradisiaca tree stem, (c) PEG, and (d) conventional.
Figure 5. SEM images 14 days. (a) Aloe barbadensis miller, (b) Musa x paradisiaca tree stem, (c) PEG, and (d) conventional.
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Figure 6. SEM images 28 days. (a) Aloe barbadensis miller, (b) Musa x paradisiaca tree stem, (c) PEG, and (d) conventional.
Figure 6. SEM images 28 days. (a) Aloe barbadensis miller, (b) Musa x paradisiaca tree stem, (c) PEG, and (d) conventional.
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Figure 7. (a). EDX results of 7 days Aloe barbadensis miller. (b). EDX results of 7 days Musa x paradisiaca tree stem. (c). EDX results of 7 days PEG. (d). EDX results of 7 days conventional.
Figure 7. (a). EDX results of 7 days Aloe barbadensis miller. (b). EDX results of 7 days Musa x paradisiaca tree stem. (c). EDX results of 7 days PEG. (d). EDX results of 7 days conventional.
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Figure 8. (a). EDX results of 14 days Aloe barbadensis miller. (b). EDX results of 14 days Musa x paradisiaca tree stem. (c). EDX results of 14 days PEG. (d). EDX results of 14 days conventional.
Figure 8. (a). EDX results of 14 days Aloe barbadensis miller. (b). EDX results of 14 days Musa x paradisiaca tree stem. (c). EDX results of 14 days PEG. (d). EDX results of 14 days conventional.
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Figure 9. (a). EDX results of 28 days Aloe barbadensis miller. (b). EDX results of 28 days Musa x paradisiaca tree stem. (c). EDX results of 28 days PEG. (d). EDX results of 28 days conventional.
Figure 9. (a). EDX results of 28 days Aloe barbadensis miller. (b). EDX results of 28 days Musa x paradisiaca tree stem. (c). EDX results of 28 days PEG. (d). EDX results of 28 days conventional.
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Figure 10. (A). XRD patterns of concrete with water curing. (B). XRD patterns of concrete with Aloe Barbadensis miller. (C). XRD patterns of concrete with Musa x paradisiaca. (D). XRD patterns of concrete with PEG.
Figure 10. (A). XRD patterns of concrete with water curing. (B). XRD patterns of concrete with Aloe Barbadensis miller. (C). XRD patterns of concrete with Musa x paradisiaca. (D). XRD patterns of concrete with PEG.
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Figure 11. Thermogravimetric analysis of 28 days concrete samples.
Figure 11. Thermogravimetric analysis of 28 days concrete samples.
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Figure 12. (A). Differential thermal analysis of 28 days conventional concrete sample. (B). Differential thermal analysis of 28 days Aloe Barbadensis miller concrete sample. (C). Differential thermal analysis of 28 days Musa x paradisiaca concrete sample. (D). Differential thermal analysis of 28 days polyethylene glycol concrete sample.
Figure 12. (A). Differential thermal analysis of 28 days conventional concrete sample. (B). Differential thermal analysis of 28 days Aloe Barbadensis miller concrete sample. (C). Differential thermal analysis of 28 days Musa x paradisiaca concrete sample. (D). Differential thermal analysis of 28 days polyethylene glycol concrete sample.
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Figure 13. Mechanism of internal curing with bio admixtures.
Figure 13. Mechanism of internal curing with bio admixtures.
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Table
Table 1. Characteristics of cement, aggregate, and admixtures.
Table 1. Characteristics of cement, aggregate, and admixtures.
S. No.Material PropertiesRemarks
1.Specific gravity of cement3.10
2.Specific gravity of FA and CA2.57 and 2.72
3.Fineness modulus of FA and CA2.70 and 6.4
4.Impact value of coarse aggregate17%
5.pH of water7.0
6.pH of Musa x paradisiaca tree stem6.5
7.pH of Aloe barbadensis miller5.5
8.Bulk density of FA and CA1450 and 1750 kg/m3
Table
Table 2. Functional group of bio and chemical admixtures.
Table 2. Functional group of bio and chemical admixtures.
Name of the AdmixtureFunctional GroupRole
Aloe barbadensis MillerSustainability 15 03591 i001The presence of Hydroxyl ether in plants holds water initially and releases whenever needed for hydration of cement in concrete.
Musa x paradisiacaSustainability 15 03591 i002
Polyethylene GlycolSustainability 15 03591 i003The presence of the polyether group reduces self-desiccation and works through the retention of water molecules around the particle layer of concrete ingredients. Hence, continuous hydration of concrete is enabled.
Table
Table 3. Mix proportioning of M30 grade concrete.
Table 3. Mix proportioning of M30 grade concrete.
CementFine AggregateCoarse AggregateWater
420 kg640 kg1155 kg190 L
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Malathy, R.; Selvam, B.; Prabakaran, M. Evaluation of Aloe barbadensis Miller and Musa x paradisiaca as Internal Curing Agents in Concrete. Sustainability 2023, 15, 3591. https://doi.org/10.3390/su15043591

AMA Style

Malathy R, Selvam B, Prabakaran M. Evaluation of Aloe barbadensis Miller and Musa x paradisiaca as Internal Curing Agents in Concrete. Sustainability. 2023; 15(4):3591. https://doi.org/10.3390/su15043591

Chicago/Turabian Style

Malathy, Ramalingam, Balakrishnan Selvam, and Mayakrishnan Prabakaran. 2023. "Evaluation of Aloe barbadensis Miller and Musa x paradisiaca as Internal Curing Agents in Concrete" Sustainability 15, no. 4: 3591. https://doi.org/10.3390/su15043591

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