Cymbopogon nardus Leaf Ash as an Alternative Material for Enhancing Concrete Strength

,


Introduction
Cement is a fundamental building material used in a wide range of construction projects, including buildings, bridges, and dams [1].Limestone accounts for 60%-65% of a typical composition of cement, and silica accounts for 17%-25% of its composition.Cement also contains alumina, iron, magnesium, sulfur, and sodium [2].Cement production is associated with the emission of CO 2 gases, making it environmentally threatening [3][4][5].Van den Heede and De Belie [6], Lee et al. [7], and Yang et al. [8] reported that the production of 1 kg of cement results in the emission of approximately 0.85 kg of carbon dioxide.
As a tropical nation, Indonesia shares a wide variety of natural resources, including an abundance of medicinal plant species.The leaves of one of these plants, Cymbopogon nardus, are renowned for being luxuriant and abundant.The leaves and roots of C. nardus are high in alkaloids, saponins, tannins, polyphenols, and flavonoids.Moreover, the foliage contains essential oils made up of various aromatic compounds [26].
C. nardus is a type of plant that produces essential oil [27,28].Citronella and geraniol are the primary components of C. nardus [29], and both have distinct fragrances [30].The cosmetics, perfume, soap, and pharmaceutical industries typically utilize essential oils [31].Additionally, essential oil can be used as an antifungal, antibacterial, and insect repellent [32][33][34].The citronella content of C. nardus ranges between 0.5% and 1.5%, with the remainder consisting of solid waste (raw material residues) and distillation water [35].Moreover, the processing of C. nardus into various products does not involve the disposal of its leaves, resulting in their dumping and disposal, resulting in bad smells, and environmental damage in the surrounding area [26].
When C. nardus leaf is burned and turned into C. nardus leaf ash (CNLA), it produces approximately 35.51% silica oxide, a component that is also found in cement [36].The silica content of C. nardus leaf ash and rice husk ash is nearly identical [37].Research suggests that rice husk ash can partially or completely replace cement in concrete [22,38,39].The substitution of rice husk ash into cement at levels of 5%-15% can enhance the strength of concrete (compressive strength, tensile strength, and flexural strength) [21,40].
This study investigates the effects of substituting CNLA in cement at substitution levels of 0%, 5%, 10%, and 15% by volume on concrete, as well as its effect on concrete strength (compressive and tensile strength) and workability value resulting from the incorporation of CNLA.In earlier times, C. nardus leaf was only utilized to produce fragrant oils; it was never incorporated into concrete.The silica content in CNLA has the potential to be used as a substitute for cement in concrete.Furthermore, this study also tries to minimize waste accumulation in the surrounding area of C. nardus leaves plantations, establish an optimal mix integrating CNLA, and maximize the workability, compressive strength, and tensile strength of concrete.
The CNLA utilized in this investigation originated in Aceh Tengah, Indonesia.This waste was incinerated at 500°C, sieved through a No. 200 sieve; and then substituted into cement at concentrations of 0%, 5%, 10%, and 15% using 15 cm × 30 cm cylindrical specimens.The main findings of this study include the testing of compressive and tensile strengths of concrete, which were analyzed using analysis of variance (ANOVA), and the determination of the optimal concrete strength values using Design Expert Application.In addition, XRD (X-ray diffraction), XRF (X-ray fluorescence), SEM (scanning electron microscopy), FTIR (Fourier transform infrared), and TGA-DTA (thermogravimetric analysis-differential thermal analysis) analyses were conducted to examine the different characteristics of CNLA.

Materials and Methods
2.1.Materials.The cement used was PCC (Portland composite cement); the fine aggregate was composed of river sand with a diameter of 4.75 mm (fine sand) and 9.50 mm (coarse sand); and the coarse aggregate has a diameter of not more than 25 mm.Fine and coarse aggregates were extracted from the Krueng Aceh River in Jantho City, Aceh Besar District, Aceh Province.The water used in this research was clean and did not contain mud or oil.The CNLA used originates from the ashes of C. nardus leaves burned on plantation land in Takengon, Central Aceh Regency, Aceh Province.The ashes from burning C. nardus leaves, which have turned into coarse particles, are collected, and then transported to the laboratory, where they are soaked in water for 24 hr to remove the dirt.Then, the ashes were heated at 105°C for 24 hr [41].The dried coarse granules are burned manually using a combustion chamber at a temperature of 500°C, like how rice husks have been used in the past [42].A dual-laser-equipped automatic temperature measurement instrument measures the temperature.As shown in Figure 1, the measuring instrument was positioned near the outer surface of the drum until the temperature reads 500°C.The coarse grains have a burning duration of 90 min.The CNLA was then sieved with a No. 200 sieve.The results of

2
Advances in Civil Engineering the sieve were added to the cement in the following proportions: 0%, 5%, 10%, and 15%. Figure 2 illustrates the results of converting C. nardus leaf waste into CNLA.

Physical Properties Analysis.
The purpose of examining the physical properties of aggregate is to determine if the aggregate used in concrete mixtures satisfies the required standards.The physical properties of aggregates are examined using procedures from ASTM, including bulk density analysis (ASTM C 29/C 29M-97) [43], absorption (ASTM C 127-01) [44], specific gravity, and sieve analysis (ASTM C136-01) [45].This investigation examines the physical properties of both fine aggregate (fine sand and coarse sand) and coarse aggregate when examining the physical properties of aggregate.Before examining the physical properties of aggregate, it was washed and sieved through sieves measuring 4.75 mm (fine sand), 9.50 mm (coarse sand), and 25 mm (coarse aggregate).The sorted fine aggregate and coarse aggregate were placed in an oven at 105°C for 24 hr to determine the bulk density of aggregate.Then, each aggregate was layered and compacted 25 times in the container.In the same way, this experiment was repeated until the third layer was filled.The aggregate-containing container was weighed, the weight was recorded, and the dimensions of container were measured.The bulk density of fine aggregate and coarse aggregate was derived from these measurements.Similar to the previous stage, the aggregate was washed and placed in an oven at 105°C for 24 hr to determine the sieve analysis of aggregate.To verify the arrangement of coarse aggregate sieves, a sieve arrangement with the largest dimension measuring 25 mm and the smallest measuring 0.150 mm was prepared.Later, 2,000 g of coarse aggregate were placed into the sieve arrangement, filter it, and then record the weight of each sieve.The procedure for acquiring the grain arrangement for fine sand and coarse sand was identical to that for coarse aggregate.The sieve arrangement for fine sand has a maximum size of 4.75 mm and a minimum size of 0.150 mm, with 500 g of aggregate included.
Meanwhile, the sieve arrangement for coarse sand with the largest size is 9.50 mm and the smallest size is 0.150 mm, with the amount of aggregate included being 1,000 g.
The aggregate was washed, sifted, and immersed in water for 24 hr to determine its specific gravity.Following that, the specific gravity of the fine aggregate was determined by observing the SSD (surface saturated dry) condition of the aggregate.For the SSD experiment, a cone-shaped container was utilized.The aggregate was layered and compacted 25 times within the cone.Then, the cone was lifted to observe the resulting decline.If the decrease is partial, the aggregate is in an SSD state, and its specific gravity can be determined using a measuring cup in the subsequent experiment.Conversely, the coarse aggregate SSD is visible visually, as the color of aggregate transforms to a white color; if the color is identical, then continue by measuring the specific gravity with a basket.
2.3.Characteristic Analysis.This investigation involved XRD, XRF, SEM, FTIR, and TGA-DTA testing to determine the characteristics of CNLA.The tests being performed seek to determine the mineral composition and structure of CNLA.XRD testing is used to analyze the composition of compounds in materials and to characterize crystals [46].It can also be used to determine the categories of elements and compounds present in materials.This examination is conducted by inserting the sample into the XRD instrument.Then, attach the instrument to the computer and set the angle to 2Ɵ to generate a graph of the sample's chemical compound composition.XRF testing is one of the tests used by the researchers to analyze the qualitative and quantitative chemical elements present in a substance.The sample is inserted into an XRF device and connected to a computer for this examination.Next, the computer program is run and automatically analyzed, resulting in a detailed percentage of the sample's chemical element content.
The SEM is a type of electron microscope that can produce high-resolution images of a sample's surface.Due to the substitution of electrons for light waves, SEM images have qualitative characteristics in two dimensions and are useful for determining the surface structure of samples [47].This SEM observation was performed by placing the sample on the SEM instrument and adjusting the instrument's magnification to 500 times.The results of magnification were observed, along with the surface topography of the sample.The FTIR measurement identifies the chemical composition of a substance [48].This examination can detect chemicals in the form of compounds, atoms, or polymers.This test is conducted by focusing light on the sample, and the results are a graph of the functional groups of the solid material.The graph results are then analyzed to determine the sample's chemical characteristics.The TGA-DTA test is used to analyze the temperature-dependent behavior of a substance [49].The purpose of this experiment is to determine the correlation between chemical reactions and temperature.This test is conducted by heating the sample at a specific location, temperature, and time until the sample's mass decreases.Therefore, this test will determine the sample's weight before and after heating it to a specific temperature.
2.4.Concrete Mix Design.Concrete mix design was calculated using the ACI 211.1-91 method [50] with a maximum aggregate diameter of 25.00 mm and a slump of 75-100 mm.The composition of the concrete was determined based on its mass in kilograms per cubic meter.In this study, CNLA was substituted for cement at concentrations of 0%, 5%, 10%, and 15%, with a diameter of 0.075 mm or passing sieve size 200.
According to previous research, the quantity of waste substituted into cement ranged from 0% to 15% [51].In addition, the research on C. nardus has never been conducted before; therefore, the concrete quality aimed for this study is the minimum structural concrete quality required by SNI (Indonesian National Standards), which is 17.0 MPa [52].
2.5.Specimen Design and Slump Test.The cylindrical specimen used in this study had dimensions of 150 by 300 mm.Twenty specimens were utilized for compressive strength testing, while the remaining twenty specimens were utilized for testing concrete fracturing tensile strength.Table 1 displays the planned specimens for this study.
Fine sand that has passed sieve No. 4 (4.75-mmdiameter), coarse sand that has passed a 3/8′′ sieve (9.50-mm diameter), and coarse aggregate that has passed a 1′′ sieve (25.00-mm diameter) were weighed according to the concrete mix design results in units of kg/m 3 .Moreover, a mixer machine with an 80-liter capacity was used to prepare the concrete.Accordingly, casting was carried out for every five specimens for each variation in the percentage of CNLA.Furthermore, eight times as many castings were conducted.All concrete mixing ingredients, including water, cement, coarse aggregate, coarse sand, and fine sand, are sequentially added to the mixer and stirred until the mixture was thoroughly blended.Due to the use of external materials, specifically CNLA, not all of water was used.This was done to ensure that the slump value  Note.NC, normal concrete for specimen number 1-5; CNLA-5%, 5% of Cymbopogon nardus leaf ash in cement for specimen number 1-5; CNLA-10%, 10% of Cymbopogon nardus leaf ash in cement for specimen number 1-5; CNLA-15%, 15% of Cymbopogon nardus Leaf Ash in cement for specimen number 1-5.

Advances in Civil Engineering
corresponds to what was anticipated.Therefore, at the beginning of the casting procedure, the water content was maintained between 3% and 5%, which will later be used to adjust the slump value to the target level.If, after mixing and testing for the slump, it was determined that the slump value has not decreased, the remaining water was added again.However, if the decline value decreases as expected, the remaining water does not need to be used again.The concrete mixture was then poured into the specimen mold following ASTM specifications.After 1 day, the mold was removed from the specimen, and it was immersed in an immersion chamber for 28 days.
The slump test was conducted by pouring a concrete mixture into a cone-shaped container, which was then compacted 25 times in three layers.Then, the decrease that occurs upon lifting was observed and determine its scale.Next, the scale of the decline was determined to be consistent with expectations.If not, water must be added or subtracted, as explained previously.
2.6.Bulk Density Experiment.Bulk density testing was conducted in two stages: the first stage consists of compressive strength testing, and the second stage consists of tensile strength testing.Before testing compressive strength and tensile strength, the bulk density was measured, which includes four variations: bulk density for normal concrete, bulk density for 5% substitute concrete, bulk density for 10% substitute concrete, and bulk density for 15% substitute concrete.Accordingly, the bulk density test was conducted when the test object is 28-day old.After 28 days of soaking, cylindrical test objects were removed from the soaking chamber and left to dry for 12 hr.The test object was weighed three times, and its horizontal (diameter) and vertical (height) dimensions were measured.After calculating the average value, the diameter and height of the cylinder were determined.The volume of the cylinder was determined by its diameter and height.The concrete bulk density was determined by comparing the test object's mass to its volume, in kg/m 3 .Using the design expert application, bulk density data were analyzed with ANOVA.ANOVA will provide a p-value that indicates whether the substitution of CNLA in cement is statistically significant.If the p-value is less than 0.05, CNLA contributes significantly to the volume weight of concrete.If p >0:05, then the substitution of CNLA for cement has no significant effect on the bulk density of concrete.In addition, a graph was generated between the bulk density of concrete, the substitution percentage of CNLA, and its slump value.

Compressive Strength Experiment.
The testing of compressive strength was conducted under ASTM C39/C39M-03 [53].The specimen for the compressive strength test was a cylinder with a 150-mm diameter and a 300-mm height.The specimen was evaluated for its compressive strength when it was 28-day old.Specimens that had been submerged for 28 days were removed and allowed to dry for 12 hr in the chamber.Before testing the strength, the specimen was weighed; and its dimensions were measured to determine the bulk density of the concrete.Furthermore, the specimen's compressive strength was evaluated.The specimen was positioned in the direction of the load and placed on the testing machine.The engine was started, and the load was gradually increased.On the reading dial, it was evident that two dials were simultaneously ascending, followed by another dial descending.When one of the dials was lowered, the reading for the utmost load was recorded.Next, the concrete's compressive strength was determined through the incorporation of data.In concrete bulk density testing, data on compressive strength were analyzed with ANOVA through the design expert application, as was the case with data on compressive strength.
2.8.Split Tensile Strength Experiment.The split tensile strength of concrete was determined according to ASTM C496/496M-11 [54].The specimen was the same as that used for compressive strength testing: a cylinder with a 150-mm diameter and 300-mm height.Testing the tensile strength of concrete uses the same procedure as testing the compressive strength of the concrete.The primary distinction was in the orientation of loading, where the specimen was positioned parallel to the load.The machine was turned on, with the load being increased steadily until it reaches its maximum capacity, testing the compressive strength of concrete.Afterward, data processing were performed to derive the concrete's split tensile strength.As with the compressive strength test, the results of the concrete tensile strength test were analyzed using ANOVA within the design expert application.The examination of the aggregate's physical properties was conducted in the laboratory, and the results are presented in Table 2.

Results and Discussion
According to Table 2, the bulk density of fine sand, coarse sand, and coarse aggregate are 1,697, 1,848, and 1,736 kg/l, respectively.Previous researchers have suggested that a suitable bulk density of aggregate is greater than 1,400 kg/l [55].The value obtained was still within the specified limits.The specific gravities of fine sand, coarse sand, and coarse aggregate were 2.755, 2.744, and 2.834, respectively.According to a previous research by Orchard et al. [56], an acceptable aggregate's specific gravity should be greater than 2.600.The specific gravity value obtained was consistent with this finding.The obtained total absorption value was 2% lower.According to the previous research, a reasonable absorption value for aggregates occurs between 0% and 2% [55].The FM values obtained for fine sand, coarse sand, and coarse aggregate were 2.34, 2.92, and 6.83, respectively.According to the previous research, a suitable FM for fine sand is between 1.50 and 3.80, for coarse sand between 2.90 and 3.20, and coarse aggregate between 5.5 and 8.0 [57].The results of analyzing the aggregate's physical properties indicate that the aggregate in this investigation can be used as material in the production of concrete.

Characteristic Test Result.
The purpose of XRD examination is to determine the crystal structure, phase, degree of Advances in Civil Engineering crystallinity, lattice parameters, and the types of elements and compounds present in a material.Figure 3 displays the results of XRD measurements on CNLA.
The purpose of XRF analysis was to determine the chemical elements present in a solid or liquid sample.Based on XRF testing, the chemical element analysis of CNLA obtained the results presented in Table 3.According to Table 3, approximately 32% of CNLA was composed of the element Si, or silica.In addition, around 11% of CNLA was composed of calcium.The two predominant components of CNLA share characteristics with cement.According to the previous researchers, the primary components of cement are silica and calcium [59].
SEM examination was utilized to examine the material's microscopic structure and surface.Figure 4 shows the SEM test results of CNLA incinerated at 500°C, which have been magnified 1,000 times, 2,000 times, and 3,000 times.The morphological characteristics of the CNLA sample are evident from Figure 4(a): It consists of rectangular particles displaying a rough surface.The particles exhibit a range of lengths, with an average diameter of 10 µm.Certain particles contain very fine gaps.The particle spacing is nearby, with only minor voids present in a fraction of the particles.
According to the data presented in Figure 4(b), CNLA displays a morphological characteristic of long, irregular particles measuring an average of 10 µm in diameter with openedge separations.The surface is uneven in texture and 6 Advances in Civil Engineering partially smooth.There are major gaps between the particles, and their separation is not particularly close.The morphological characteristics of CNLA are evident in Figure 4(c), which depicts the presence of thin sheets and lengthy particles featuring smooth surfaces.The mean size at a magnification of 3,000 times is 5 µm.Compacted masses are observed at the top of the sheet.The only area where a minor gap forms is in the center.
Functional groups in solid and liquid samples can be determined using FTIR analysis.Figure 5 depicts the results of the FTIR examination.On the basis of this image, it was evident that CNLA incinerated at 500°C forms several compound bonds, namely C─H, O─H, and C─H.C─H functional group was formed at an absorption of 2,877.79cm −1 with alkane compounds; the O─H functional group was formed at an absorption of 2,524.82cm −1 with alcohol and phenol (H bond) compounds; and the C─H functional group was formed at an absorption of 794.67 cm −1 with alkene compounds.CaO was detected in the highest absorption band, namely 2,877.79cm −1 , which corresponds to the C─H functional group peak (Figure 5).The FTIR measurement results were consistent with the previous research [60].
The TGA-DTA test was conducted to determine the sample's weight loss and heat emission after being heated to a specific temperature.Figure 6 displays the TGA-DTA test results for CNLA.The TGA curve in Figure 6(a) indicates that the weight of CNLA decreases by 14.45% during heating from room temperature to 600°C.The loss of weight in CNLA was the result of water evaporation.Moreover, Figure 6(b) depicts a DTA curve with a heat discharge of −596.91 cal/g.

Concrete-Mix Design Results
. The concrete arrangement was planned according to the ACI rules, which were based on weight in kg/m 3 units.

Advances in Civil Engineering
the bulk density of concrete produced for a design compressive strength of 17.0 MPa is 2,380 kg/m 3 [61].In addition, the obtained bulk density of concrete value is close to the average bulk density of concrete value, which is 2,400 kg/m 3 [62].

Slump Test Result.
The intended slump in this study was 75-100 mm, following ACI regulations.Using a concrete mixing machine, five specimens were mixed for each mixture of concrete-forming materials.Thus, eight trials of the collapse test were conducted, with each trial containing five specimens.Each experiment provides a slump value or reduction in the concrete mixture.The decline value was examined to determine whether it was decreased as anticipated.Adding or subtracting water was necessary if tests do not meet the plan.For more details, it can be seen in Table 5.
According to Table 5, the slump values obtained for the compressive strength and tensile strength specimens follow the same pattern: the greater the quantity of CNLA substituted in the cement, the harder the concrete mixture was to mix.Other studies by Attah et al. [63][64][65][66] have come to similar conclusions.To achieve the planned slump, the quantities of cement and water must be increased, as shown in Table 5.The addition of cement and water was essential because the slump test did not decrease, necessitating multiple trials to achieve the desired slump of 75-100 mm.The addition of cement and water (workability) in this study was because excessive absorption occurs and Ca(OH)

Test Results for Bulk Density and Compressive Strength of
Concrete.The analysis of the test results for the bulk density and compressive strength of concrete was conducted using ANOVA.The parameters considered in the analysis were variations in the substitution of CNLA in cement and the slump value.Table 6 displays the design parameters and corresponding responses utilized in the analysis of test data related to the bulk density and compressive strength of concrete.The results for evaluating the bulk density and compressive strength of concrete were analyzed through the design expert application using ANOVA based on the design parameters and responses shown in Table 6.
Table 7 shows the model summary statistics and the ANOVA for the bulk density response, respectively.The results of measuring the bulk density of concrete are highly significant (p <0:05), as shown in the table.This indicates that substituting CNLA for cement has a significant impact on the bulk density of concrete.The F-value for the results of the statistical analysis of bulk density was found to be 25,256.00.This indicates that the obtained model is significant, with a 0.44% error rate.The Predicted R 2 of 0.9982 is in reasonable agreement with the adjusted R 2 of 0.9999; i.e., the difference is less than 0.2.
The results of the concrete compressive strength test were also analyzed using ANOVA and the design expert application.Table 8 shows the model summary statistics and the ANOVA for the compressive strength response, respectively.The results of measuring the compressive strength of concrete are significant (p <0:05), as shown in the table.This indicates that the substitution of CNLA for cement has a significant impact on the increase in concrete Advances in Civil Engineering compressive strength.According to the statistical analysis of compressive strength, the F-value was determined to be 208.36.This indicates that the model obtained has a significant error rate of 4.89%.The predicted R 2 of 0.7766 is not as close to the adjusted R 2 of 0.9928 as one might normally expect; i.e., the difference is more than 0.2.Using a linear graphic model and the results of laboratory tests on the bulk density and compressive strength of concrete, a graph of the bulk density and compressive strength of concrete can be made using the parameters CNLA substitution and slump value.The results of the concrete bulk density and compressive strength experiments are shown in Figure 7. Based on Figure 7(a), the minimum bulk density of concrete is approximately 2,455.51 kg/m 3 , and the maximum is approximately 2,462.09kg/m 3 .When CNLA is added to cement, the bulk density of the concrete decreases.Attah et al. stated similarly that the bulk density of concrete decreases proportionally with the amount of oyster shell ash substituted for cement [68].Figure 7(b) shows that the minimum compressive strength of concrete is approximately 17.88 MPa and the maximum is approximately 22.58 MPa.By substituting 10% CNLA for cement, the compressive strength of concrete can be increased.This is because the cement hydration process can react with the existing CaO and SiO 2 and distributing them equitably in the correct proportions.The compressive strength of concrete decreases by 5% when CNLA is substituted.This is because the CaO in CNLA does not react effectively with the CaO in cement.A 15% substitution of CNLA resulted in a decrease in the compressive strength of the concrete.Due to the excessive SiO 2 content, the CaO content in cement can no longer react with silica (saturation occurs).The results of this study are consistent with prior research that suggested variations in the compressive strength of concrete could result from the addition of periwinkle to cement at concentrations of 0%, 5%, 10%, and 15%, with the corresponding values being 17.6, 17.0, 19.1, and 16.8 MPa [69].Additional research findings indicate that varying percentages (0%, 4%, 6%, and 8%) of clam shell ash substituted for cement can induce variations in the compressive strength of concrete.Specifically, the following compressive strength values were obtained: 45.0, 38.6,47.8,and 32.6 MPa [70].This study's compressive strength test results are comparable to those found in Bai et al.'s [71] research, which found that the substitution of nano silica in cement at concentrations of 0%, 0.6%, 0.9%, and 1.2% resulted in varying compressive strengths.The compressive strength of concrete decreases when nano silica is substituted into cement by 0.6%, but increases when substituted at 0.9%, and subsequently, the compressive strength decreases when substituted by 1.2%.However, the obtained compressive strength was consistent with predictions [71].
Based on the results of testing the bulk density and compressive strength of concrete, the design expert application was optimized to achieve maximum concrete compressive strength.Based on the optimization results, 100 concrete compressive strength maximization solutions were generated.Table 9 is one of 100 solutions produced based on variations in the percentage of CNLA (0%-15%) and slump   10, the bulk density test results were analyzed using ANOVA via the design expert application.Table 11 shows the model summary statistics and the ANOVA for the bulk density response, respectively.
The results of measuring the bulk density of concrete are statistically significant (p <0:05), as shown in the table.This significant result demonstrates the same trend as the bulk density measurement in Table 7, namely that it has an important influence on the concrete bulk density.The F-value for the results of the statistical analysis of bulk density was 4.88 × 10 7 .This indicates that the obtained model is accurate, with an error rate of 0.01%.The predicted R 2 of 1.0000 is in reasonable agreement with the adjusted R 2 of 1.0000; i.e., the difference is less than 0.2.
The results of the concrete tensile strength test were also analyzed using ANOVA via the design expert application.Table 12 shows the model summary statistics and the ANOVA for the tensile strength response, respectively.
The table displays that the results of measuring the tensile strength of concrete are statistically significant (p <0:05).This indicates that the substitution of CNLA for cement significantly increases the tensile strength of concrete.The F-value for the results of the statistical analysis of tensile strength was found to be 1,462.50.This indicates that the obtained model is significant, with a 1.85% error rate.The predicted R 2 of 0.9945 is in reasonable agreement with the adjusted R 2 of 0.9990; i.e., the difference is less than 0.2.
Based on the results of laboratory testing of the bulk density and tensile strength of concrete, a graph of the bulk density and tensile strength of concrete can be created by integrating the parameters CNLA substitution and slump value with a linear graphic model, as illustrated in Figure 8.Based on Figure 8(a), the minimum bulk density of concrete is approximately 2,441.84 kg/m 3 , and the maximum is approximately 2,494.30kg/m 3 .More CNLA reduces the bulk density of concrete.The results of this bulk density test follow the same pattern as the previous bulk density test.Figure 8(b) shows that the minimum tensile strength of concrete is approximately 2.43 MPa and the maximum is approximately Advances in Civil Engineering 3.18 MPa.By substituting 15% CNLA for cement, the tensile strength of concrete can be increased.This is because the cement hydration process can react with the existing CaO and SiO 2 and distribute them equitably in the correct proportions.[13] stated that by converting oyster shell waste into oyster shell ash and substituting 15% of the ash into cement, the tensile strength of concrete could be significantly increased.Other researchers have also reported that substituting 5%-15% rice husk ash for cement can improve the tensile strength of concrete [21,40].In contrast to the trend observed in the compressive strength of concrete, which increases with a 10% CNLA substitution, the tensile strength of concrete experiences an increase at a 15% CNLA substitution.This is because the CNLA sample consists of irregularly shaped, oval, and rectangular particulates with a rough surface.CNLA has a morphological structure comparable to that of fiber.While the incorporation of fiber into concrete can generally enhance its tensile strength, it does not guarantee a substantial improvement in its compressive strength [55].Consequently, as the tensile load increases, the CNLA morphology can start deforming.As the number of CNLA substitutions in cement increases, so does the number of fiber-like particles; consequently, the tensile strength rises.
Based on the results of testing the bulk density and tensile strength of the concrete, the design expert application was used to optimize the concrete to achieve the highest possible tensile strength.Based on the optimization results, 100 solutions were obtained to generate the maximum tensile strength of concrete.Table 13 is one of one hundred solutions generated based on variations in the percentage of CNLA (0%-15%) and slump value (75-100 mm), with an ideal desirability value of 1.0.The maximum tensile strength of concrete, according to Table 13, is 3.252 MPa.This indicates that the optimum tensile strength of concrete can be attained if CNLA is added to cement at a ratio of 13.33% and the slump value is 94 mm.

Conclusion
The findings of the study demonstrate that the substitution of CNLA to cement at varying concentrations of 0%, 5%, 10%, and 15% resulted in compressive strengths of 21.56, 21.12, 22.58, and 17.88 MPa.Moreover, the split tensile strength test showed findings of 2.43, 2.72, 2.87, and 3.18 MPa, respectively.
The results of the research indicate that increasing the use of CNLA in cement by 10% can increase the compressive and tensile strength of concrete.However, if CNLA is substituted over 10%, workability decreases, and it becomes difficult to achieve the target concrete strength.Furthermore, the utilization of CNLA as a replacement for cement has the potential to reduce agricultural waste, hence providing  environmental advantages.This is because CNLA is readily available and contains similar chemical components to cement, namely SiO 2 and CaO.

FIGURE 1 :
FIGURE 1: Utilizing a temperature measurement device to burn Cymbopogon nardus leaves.

B 0 ðbÞFIGURE 7 :
FIGURE 7: Test results for bulk density and compressive strength of concrete.(a) Bulk density testing.(b) Compressive strength testing.

FIGURE 8 :
FIGURE 8: Test results for bulk density and tensile strength of concrete.(a) Bulk density testing.(b) Tensile strength testing.

TABLE 2 :
Physical properties of aggregate result.
FIGURE 3: XRD test results for CNLA burned at 500°C.TABLE 3: XRF test results of CNLA (with mass of 225 mg/cm 2 ) burned at 500°C.
Table 4 displays the concrete-mixture design results.The proposed compressive strength of the concrete in this study was 17.00 MPa.Based on the planned compressive strength, the ACI Table provides a w/c (water cement ratio) of 0.62.Table 4 indicates that the bulk density of concrete is 2,380 kg/m 3 .According to previous research, SEM test results for CNLA burned at 500°C.(a) 1,000 times magnification, (b) 2,000 times magnification, and (c) 3,000 times magnification.

TABLE 4 :
2was Results of concrete mix design with w/c of 0.62.

TABLE 6 :
Experimental design for bulk density and compressive strength testing.

TABLE 7 :
Model summary statistics and ANOVA for bulk density response.

TABLE 8 :
Analysis of compressive strength test results using ANOVA.

TABLE 9 :
Optimization of concrete compressive strength.

TABLE 10 :
Experimental design for bulk density and tensile strength testing.

TABLE 11 :
Analysis of bulk density test results using ANOVA.

TABLE 12 :
Analysis of tensile strength test results using ANOVA.

TABLE 13 :
Optimization of concrete tensile strength.