Fresh, Mechanical, and Microstructural Properties Investigation on the Combined Effect of Biomedical Waste Incinerator Ash and Bagasse Ash for High-Strength Concrete

The combination effect of supplementary cementitious materials in the production of high-strength concrete production is an effective way to reduce the amount of cement required while contributing to environmental sustainability and cost. This study aims to assess the microstructural investigation on the combined effect of biomedical waste incinerator ash (BWIA) and bagasse ash (BA) as a partial replacement of cement in high-strength concrete production. The cement was partially replaced with BA (0%, 2.5%, 5%, and 7.5%) and BWIA (0%, 2.5%, 5%, and 7.5%). The mix design was done as per the ACI 211-4R-93 mix design standard. Slump, slump flowability, density, and compaction factor tests were conducted for freshly mixed concrete. Mechanical properties of the hardened concrete from four different mixes were also determined for the 7- and 28-day cured specimens. The microstructural properties of the hardened concrete for all mixes were also investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD) tests. Based on the experimental results, the compressive strength of high-strength concrete at every 2.5% BA and 2.5% BWIA replacement of cement in the concrete mix at 7days of curing was slightly decreased, while at 28 days of curing, the compressive strength of the control mix (51.8 MPa) decreased as compared to the mix codes’ compressive strength of the BWIA and BA5 and BWIA and BA10 mix codes, at 54.8 MPa and 52.5MPa, respectively. The SEM micrographs showed that the partial replacement of cement by the BWIA and BA leads to a decrease in the pore proportion in the enlarged interfacial transition zone (ITZ), reduced CH crystals, and a denser C–S–H gel as compared to the control specimen. The XRD pattern showed the existence of portlandite, ettringite, okenite, quartz, and calcite in the cement and aggregate phases. As a result, the usage of BWIA and BA has a significant impact on the properties of high-strength concrete in fresh, hardened, and microstructure high-strength concrete.


Introduction
Concrete is the most widely used construction material in the world because it is a multipurpose material that can be used to construct a variety of structures such as buildings, roads, dams, bridges, and so on. It is a composite material composed of Portland cement, coarse aggregate, ne aggregate, water, air, and occasionally used admixture [1,2].
High-strength concrete is designed to greater compressive strength, exural strength, and greater splitting strength than normal concrete. To create high-strength concrete that must meet performance criteria standards, superior materials are employed. To produce high-strength concrete, special mixing, placement, and curing methods are required [3]. e assembly of concrete-making ingredients or materials generally requires high cost and high energy and hence is a source of environmental pollution. Green concrete is distinguished by the use of industrial byproducts, agricultural byproducts, or alternative materials to conserve biodiversity, save money and energy, and reduce environmental effects [4][5][6][7][8].
Cement manufacturing contributes about 5% to 8% of global man-made CO 2 emissions. About half of the emissions are caused by process emissions during the clinker manufacture, 40% by the combustion of fuels to heat the cement kiln, and 10% by power consumption and transportation [3,6,[9][10][11][12][13][14] As a result, reducing carbon dioxide (CO 2 ) emissions from cement production is a critical and urgent task for the cement industry. Energy efficiency through modern dry-process technology, the use of other fuels to replace coal and pet coke within the cement kiln heating process, the substitution of clinker with other mineral components in cement, and determining other cement replacing potential materials are the four main handles for CO 2 reduction. e partial substitution of cement mix ratio is often done by biomedical waste incinerator ash and bagasse ash in concrete production to stop hazardous effects on the environment [14][15][16]. Biomedical waste generation has risen significantly over the past decades, with an annual increase of 8%. Incineration has increased in importance as an alternative method of reducing the dimensions of biomedical waste, resulting in the production of ash as a reduced volume of waste. It has been utilized as a partial replacement for cement in concrete production and as a road subgrade material in various countries. Effective use of biomedical waste ash would not only reduce the cost of construction but also contribute significantly to the reduction of environmental risks [15,[17][18][19][20][21][22][23]. When used as a supplementary cementitious material in a cement mix, biomedical waste ash also acts as a pozzolanic material because it contains a high percentage of calcium oxide, CaO, SiO 2 , and Al 2 O 3 , 40.21%, 20.1%, and 11.13% of the main component of medical waste ash, respectively [22].
Ethiopia was constructing the eight primary medical waste incinerator centers as well as pharmaceutical and clinical waste disposal facilities, and the machines were installed in Adama, Mekele, Bahir Dar, Dessie, Jimma, Neqemte, Hawassa, and Dire Dawa. Waste is thermally decomposed in several chambers of the incinerator machine using an oxygen-deficient medium-temperature combustion process in an 800-900°C chamber. Incinerators in the postcombustion chamber use air heated to 900-1200°C to reduce smoke and odor. e incineration center, which was installed in Adama, has a capacity to burn one thousand kilograms of medical waste per hour, while the remainder burns five hundred kilograms of waste per hour. e machines have a working time of 20 hours [24]. According to the Ethiopian public health institution 2018 annual report, annual medical waste in Ethiopia is above 93,000 tons. Nowadays, it is obvious that the number of healthcare facilities, governmental and nongovernmental hospitals, health centers, and health stations in Ethiopia is growing, implying that the amount of healthcare pharmaceutical wastes generated by these institutions would eventually increase.
When used as a supplementary cementitious material to the cement mix, bagasse ash also acts as a pozzolanic material property because it has a high percentage of silica (SiO 2 ), which reacts with the cement mix to form calcium silicate-hydrate gel during the hydration process. is extra C-S-H improves the mechanical strength of cement mortar and concrete, as well as the bonding between cement paste and aggregates, or the microstructure of concrete [14,[25][26][27]. Annual sugarcane production in Ethiopia is approximately 350,000 tons, so the potential for sugarcane bagasse ash is approximately 84,000 tons. According to Ethiopia's growth transformation plan, 4.6 million tons of sugar would be produced annually, resulting from the assembly of more than 1.1 million tons of sugar cane bagasse ash as waste. is amount of waste is often beneficial when utilized for a variety of productive purposes. It is used as a supplementary cementitious material in the production of concrete [28]. Based on their results, those hard waste materials partially replaced with cement significantly improved the engineering and performance properties of concrete. In addition to these waste materials, there are also abundantly available solid waste materials generated by the sugarcane manufacturing industry and medical waste incineration centers that harm human beings and the environment as well; this is termed sugarcane bagasse ash and biomedical waste incineration ash. e experimental results on the rheological and mechanical strength characteristics of concrete recommend that up to 15% bagasse waste ash and 10% biomedical waste ash be used as a partial replacement for the weight of Portland cement in the mix to produce high-quality concrete. According to their findings, the hard waste components that were partially replaced with cement enhanced the technical and performance qualities of concrete significantly. In addition to these waste materials, there are abundantly available solid waste materials generated by the sugarcane manufacturing industry and medical waste incineration centers that have an adverse influence on humans and the environment; these are known as sugarcane bagasse ash and biomedical waste ash waste. erefore, the objective of this study is to conduct a microstructural investigation on the combined effect of biomedical waste incinerator ash and bagasse ash for high-strength concrete.

Materials.
e materials used in the present study are cement, water, fine and coarse aggregate, bagasse ash (BA), biomedical waste incinerator ash (BWIA), and high range water reducer (HRWR) admixture.

Cement.
Locally produced Dangote OPC 42.5 R cement was used and its quality was tested as per the ASTM C150/C150 M standard specification [29].

Fine
Aggregate. River sand was used as a fine aggregate purchased from a locally available market. It was carefully washed with water to remove the silt and debris in it. 2 Advances in Materials Science and Engineering Physical laboratory tests were conducted according to the ASTM standard specification. e term fine aggregate is used for particles smaller than 4.75 mm sieve size [30]. e percentage of passing was found between the lower and upper limits of the ASTM C 33-08 standard specification. e particle size distribution of the fine aggregate is shown in Figure 1(b). e physical properties of the fine aggregate material used in the present study are summarized in Table 1.

Coarse Aggregate.
It was purchased from the YEN-COMADE Construction PLC crusher plant found in Goro, Addis Ababa, Ethiopia. e shape, size, and quality of coarse aggregate are important factors in the production of highstrength concrete. e material's physical properties were tested according to the ASTM standard specification. According to [30], the term coarse aggregate is used to describe particles larger than the 4.75 mm sieve size. e coarse aggregate particle size distribution of coarse aggregate is shown in Figure 1(a) and the percentages of passing were found between the lower and upper limit of the ASTM C 33-08 standard specification. e physical properties of the coarse aggregate material used in the present study are summarized in Table 2.

Biomedical Waste Incinerator Ash (BWIA).
It was obtained from Adama Medical Waste Incineration Center, Adama, Ethiopia. e BWIA was obtained from the burning of biomedical waste from various medical institutes such as hospital health centers, health stations, and pharmaceuticals waste, which is burnt in incineration center by using high temperature of 800-1200°C. e physical properties of the BWIA material used in the present study are summarized in Table 3. A sample finer than 150 µm sieve was used and its chemical compositions were determined in the Ethiopian geological survey complete silicate laboratory. e results are summarized in Table 3. e total sum of (SiO 2 + Al 2 O 3 + Fe 2 O 3 ) is equal to 52.08%. e calcium oxide, CaO, is 29.86%, and the iron oxide Fe 2 O 3 content is 1.08%. As a result, according to ASTM C 618-08a, this ash is classified as a class C pozzolan. Figure 2 illustrates the Adama Medical Waste Incineration Center and BWIA samples finer than 150 µm.

Bagasse Ash (BA).
e bagasse ash used in the study was obtained from the Wonji Sugar Factory, Wonji, Oromia Regional State, Ethiopia.
e BA was obtained after the removal of sugar juice from sugar cane bagasse and then transferred to a certain chamber to be burnt by a very high temperature of 600-900 C; thus the ash is produced. e physical properties of the BA material used in the present study are summarized in Table 3. Its chemical compositions were determined in the Ethiopian geological survey complete silicate laboratory, and the results are summarized in Table 4. e total quantity of (SiO 2 + Al 2 O 3 + Fe 2 O 3 ) is 82.28%, which is more than the minimum ASTM C 618-08a standard for class F, which is 70%. Calcium oxide, CaO, has a value of 1.44%, and iron oxide, Fe 2 O 3 , has a value of 4.32%. As a result, this ash is categorized as a class F pozzolan by ASTM C 618-08a. Figure 3 illustrates the open storage of bagasse ash at the Wonji Sugarcane Factory and BA samples finer than 150 µm.
2.1.6. Water. Potable water from the laboratory, free from organic substances, was used for mixing and curing prepared samples.

Water-Reducing Admixtures.
Water-reducing admixtures are important to reduce the quantity of mixing water to produce high-strength concrete with a definite slump, decrease water to cement ratio, and reduce the amount of cement. Typical water reducers condense the water content by almost 5% to 15%. Locally produced waterreducing admixtures were used for this present study.

Sampling.
Sampling is that a comparatively small number of units if selected in a manner that sincerely represents the study sample, can provide with a sufficiently high degree of probability a fairly true reflection of the sampling population that is being studied [31,32]. Purposive sampling, which is a random sample method, was used in this study. In this study, BA, BWIA, and other ingredients samples are sampled based on purpose-sampling techniques.

Mix Design.
In the present study, the C-50 grade of concrete was designed according to ACI 211-4R-93. Four mixtures of concrete mixes were prepared with a watercement ratio of 0.34. With cement, the mix ration was partially replaced with bagasse ash (0%, 2.5%, 5%, and 7.5%) and biomedical waste incinerator ash (0%, 2.5%, 5%, and 7.5%). e mix proportion designed for high-strength concrete mix is shown in Table 5.

Fresh and Hardened Concrete Tests.
e properties of both fresh and hardened concrete are determined as per the ASTM standard specifications. e study was carried out in the construction materials laboratory of Addis Ababa Science and Technology University, Addis Ababa, Ethiopia. e workability of fresh concrete is examined through a slump, slump flowability, compaction factor, and the density of fresh concrete. e details of fresh concrete tests are shown below (Figure 4  (1) Slump test is the most common test for determining the consistency of freshly mixed concrete. e fresh concrete mix slump test process, apparatus, and detailed measured values were determined by ASTM C-143 standard procedures [33]. Figure 4(a) showed the slump test. (2) e flowability test of freshly mixed concrete was performed in accordance with ASTM C-1611 requirements, but without using a J-Ring [34]. e Advances in Materials Science and Engineering following equation has been used to calculate slump ow ( owability): Figure 4(b) displayed the owability test of freshly mixed concrete.
where d1 is the largest diameter of the resulting circular ow of concrete (cm); d2 is a second diameter of the circular ow approximately perpendicular to the rst measured diameter (d1) (cm).     Figure 4(c) showed the compaction factor test of freshly mixed concrete.
where W1 is the weight of unfilled cylinder (Kg), W2 is the weight of partially compacted concrete (Kg), and W3 is the weight of completely compacted concrete (Kg). (4) e density of fresh concrete was determined as per the ASTM C-1688 standard specification [35]. e    Advances in Materials Science and Engineering density of freshly mixed concrete with and without cement replacement by BA and BWIA was calculated using the following equation: The density of fresh concrete where W1 is the weight of unfilled cylinder (Kg) and W2 is the weight of completely compacted concrete (Kg). (5) ree basic tests were conducted for hardened highstrength properties. e details of each test are explained as follows. (6) e compressive strength was tested on concrete size cubes of 15 * 15 * 15 cm after 7 and 28 days of curing; it was performed according to [36] standard.
where CS is compressive strength (N/mm 2 ), F is failure load (KN), and A is cross-sectional area (mm 2 ). (7) e split tensile strength was tested in cylindrical samples with dimensions ∅ 15 * 30 cm after curing a total of 7 and 28 days. Figure 5(b) shows split tensile strength test. is test procedure, apparatus, and detailed calculated values were determined according to ASTM C-496 standard methods [37]. e split tensile strength test result was calculated by the following equation:  Advances in Materials Science and Engineering where T is splitting tensile strength (MPa), P is maximum applied load (KN), L is length (mm), and D is diameter (mm). (8) e flexural strength was tested with the size 10 * 10 * 50 cm after 28 days of curing. e flexural strength test specimens were prepared and cured according to the ASTM C-78 standard [38]. e result of the flexural strength test was calculated by the following equation. Figure 5(c) showed the flexural strength test.
where R is modulus of rupture (MPa), P is maximum applied load (KN), L is span length, mm, b is average width of a specimen (mm), and d is average depth of specimen (mm).

Microstructure Test.
Microstructure examinations of the high-strength concrete were performed on the 28-day cured failed compressive strength specimens for the control (without BA and BWIA), BA and BWIA 5%, BA and BWIA 10%, and BA and BWIA 15% mix code. e cube samples are crushed and the hardened cement paste is collected from the innermost core of the concrete cube samples. e collected samples were then sieved through a 150 µm sieve size. After the preparation of the samples, the test was conducted for scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. e study was carried out in the microbiology and material engineering laboratories of Adama Science and Technology University, Adama, Ethiopia. e range of scale utilized in SEM analysis was 20 µm with a resolution of x 1000 and 500 µm with an x 500 magnification rate. e microstructural analysis of four cement paste powder samples is pictured by the JCM-6000 Plus Bench Top SEM JEOL machine, the machine shown below in Figure 6(a). e mineralogical composition of hydrate concrete powder was investigated by X-ray diffraction (XRD) using a machine produced by Shimadzu Corporation (Japan), model XRD-7000, as shown in Figure 6

Effect of BA and BWIA on Fresh Concrete Properties.
e qualities of fresh concrete are important. Consistency and workability of fresh concrete are significant requirements for the proportion of concrete mixes as well as important features that impact the placing of fresh concrete onsite and the subsequent performance of hardened concrete [39]. Various tests are conducted to analyze the properties of freshly mixed concrete, such as the slump test, slump flowability, compaction factor, and density of freshly mixed concrete. e results of each test are presented and discussed below.
A slump test method was used to determine the workability of freshly mixed high-strength concrete. is concrete mixture should be workable. It should be simple to place, compact, and complete. As shown in Figure 7(a), the slump of freshly mixed high-strength concrete with and without replacement of the cement mix ratio by bagasse ash and biomedical waste incinerator ash results in varying slumps of 120 to 97 mm. Values of 120-97 mm are considered high slumps. According to Harsimranpreet Kaur et al. [23], increasing the replacement amount of biomedical waste incinerator ash in the cement mix ratio decreases the slump of freshly mixed concrete. Similarly, in the present study, the replacement percentage of bagasse ash and

Advances in Materials Science and Engineering
biomedical waste incinerator ash increased as the slump declined. is was accomplished due to the holey nature and uneven shape of BWIA and BA particles. e slump test was not appropriate for the analysis of the uidity of the high-strength concrete. e slump owability test is also an actual indicator of extreme bleeding and segregation of concrete mix. As can be inferred from Figure 7(b), the owability test result of freshly mixed concrete is shown. All four mixes were satis ed with the high-strength concrete owability range between 50 cm and 65 cm [40]. e last mix owability is 52.9 cm, thus satisfying the range of owability of high-strength concrete, but compared to the control mix, it is 8.9 cm less because the percentage of replacement is 7.5% BA and 7.5% BWIA, which is higher than the rst two mixes. e percentage of replacement of bagasse ash and biomedical waste incinerator ash increases the owability of concrete decrease. Figure 7(c) shows the compaction factor test result of freshly mixed concrete. is is the most appropriate test for concrete that has a low water-cement ratio (high-strength concrete). e concrete compaction factor ranges between 0.78 and 0.95, where the test results vary between 0.90 and 0.94. Mix numbers 1, 3, and 4 are medium workability, and mix number 2's compaction factor is 0.94. e compaction factor of the control mix is lower than that of the mix in which the ordinary portland cement partially replaced with  e value indicates that the workability is higher compared to the control mix, increasing the quantity of cement and reducing the percentage of replacement of bagasse ash and biomedical waste incinerator ash to increase the compacting factor value. e combined effect of bagasse ash and biomedical waste incinerator ash replacement on freshly mixed concrete density is shown in Figure 7(d). At every percentage replacement of cement with bagasse ash and biomedical waste incinerator ash mix, density is decreased as compared to the control mix density because the specific gravity of cement (3.20) is higher than the specific gravity of BA and BWIA (2.18 and 2.54, respectively) as shown in Table 3. Similarly, according to Jugal V. Tailor et al. [15], there is an increase in the replacement quantity of biomedical waste ash in the cement mix ratio while the density of concrete decreases.

Effect of BA and BWIA on Hardened Concrete Properties.
e effect of a partial replacement bagasse ash and biomedical waste incinerator ash to cement mix ratio on hardened concrete properties is investigated and shown in Figure 8 e compressive strength tests were performed at 7 and 28 days of curing for the control mix and each percentage of replacement mix. High-strength concrete compressive strength without and with replacement of cement by bagasse ash and biomedical waste incinerator ash is shown in Figure 8(a). At 7 days of curing, the compressive strength of the control mix was higher than the mix with the replacement of BA and BWIA for all percentages. Without the replacement of cement by BA and BWIA there is a better early compressive strength due to the high fineness of cement and the fact that pozzolanic materials hydrate slowly. At 28 days of curing, the compressive strength of the control mix decreases compared to the BWIA and BA5 and BWIA and BA10 mix code compressive strength, which have been observed to be 55 MPa and 53 MPa; because of the fineness and chemical composition of ordinary Portland cement, the hydration processes are faster at an early age. After 7 days, the hydration processes become much slower, and the hydration processes of bagasse ash and biomedical waste incinerator ash increase. According to Pritish Gupta Quedou et al. [14,18,39,41] the compressive strength increases with curing time but decreases as the proportion of pozzolanic materials replacement increases. erefore, the compressive strength of the study decreases as the replacement of BA and BWIA increases. e split tensile strength test after 7 and 28 days of curing is shown in Figure 8(b). At 7 days of cured split tensile strength, the result varies from 2.15 MPa to 3.73 MPa and after 28 days of curing, the variation is between 3.08 MPa and 4.49 MPa. e split tensile strength decreases in the early days of curing with BA and BWIA. is was attributed to the high porosity and lower finesses of BA and BWIA. At 28 days of cure age, the replacement of cement with 2.5% BA and 2.5% of BWIA showed the highest split tensile strength compared to the control mix. According to ACI Committee 363R-10, the splitting tensile strength is almost 5% to 10% of the compressive strength of concrete and 70% of the flexural tensile strength after 28 days of curing [42]. e split tensile results of all concrete mixes at 7 days and 28 days of curing were compatible with 5% to 10% of the compressive strength of concrete and 70% of the flexural tensile strength at 28 days of curing. According to Bashir Ahmed Memon et al. [16,17], increasing the replacement quantity of biomedical waste ash in the cement mix ratio decreases the split tensile strength. Similarly, in this study, 10% and 15% of replacement of BA and BWIA are directly proportional to decreased splitting tensile strength.
e XRD diffraction patterns of four hydrated concrete powder samples are shown in Figure 9(a)-9(d). X-ray diffraction patterns are formed by a goniometer which is rotated through 10 to 60 degrees of 2theta angles on the samples, with part of the XRD diffraction pattern of hydrated concrete samples. e letter symbols on the figures represent the names of minerals and peak intensities of concrete powder diffraction. e Y-axis represented X-ray intensity; the X-axis diffraction angle was 2theta degrees. e reference database used in this study was COD-Inorg 2021.06.14.
e following X-ray diffraction pattern crystalline phases are covered in this study as portlandite (Ca (OH) 2 ), ettringite (A l2 Ca 6 H 64 O 50 S 3 ), calcite (CaCO 3 ), quartz (SiO 2 ), and okenite (Ca 5 H 23 O 32 Si 9 ), which is similar to the family of C-S-H commonly found in the hardened concrete paste. In all samples, a small amount of calcite is found.
Portlandite is the mineral name for calcium hydroxide [45]. e amount of calcium hydroxide is present in the control mix and blended cement mix with BA (0%, 2.5%, 5%, and 7.5%) and BWIA (0%, 2.5%, 5%, and 7.5%) specimens, which represent an indication of the degree of hydration. e mineral name for this calcium sulfoaluminate is ettringite, which is often found in Portland cement concrete. Supplementary cementitious materials and admixtures also contain sulfate and aluminate. Within the first few hours after mixing with water, gypsum and other sulfate compounds in the cement react with calcium aluminate to create ettringite. e mechanism that controls stiffening is the development of ettringite in fresh concrete, which increases Advances in Materials Science and Engineering strength development, increases durability with lled holes or cracks, and limits drying shrinkage [46]. Silicon oxide is known as quartz (SiO 2 ). It is the most important part of the sand. It is responsible for the creation of calcium silicates such as dicalcium silicate (C 2 S) and tricalcium silicate (C 3 S), which are the building blocks of concrete strength. Because of the higher hydration rate, the control mix contains more calcite (CaCO 3 ), has better workability, and has higher compressive strength at an earlier stage of curing than the blended cement mix. However, at 28 days of curing, the compression strength of the control mix decreases due to the higher amount of calcite (CaCO 3 ) and the decreased rate of hydration after 7 days of curing. Similarly, according to Maisarah Ali et al. [47], the present percentage of calcite (CaCO 3 ) increases the workability and early age compressive strength, but increasing the curing age of the concrete decreases compressive strength. Okenite is a hydrated calcium silicate hydroxide. It is an unusual mineral [48]. It frequently forms "cotton ball" collections, where the crystals are so thin that they look like tiny bers. e collections are composed of straight, radiating, thread-thin crystals. ese clusters can make for very attractive specimens and often accompany  many ne and rare minerals such as apophyllite, gyro lite, and many of the zeolites. e mineralogical composition of the XRD di raction analysis di raction pattern graphics of the control mix (BA and BWIA 0) is shown in Figure 9  pattern graphics of the 2.5% BA and 2.5% BWIA mix shows the mineralogical composition of the di raction pattern graphics in Figure 9(b). e highest peak values of quartz at (2θ 27.5°), portlandite (2θ 17.8°and 34.4°), and calcite at (2θ 29.7°) have majority peaks, which is formed quickly due to the reaction of calcium hydroxide with the surrounding air carbon dioxide (Ca (OH) 2 + CO 2 ↔ CaCO 3 + H 2 O). Figure 9(c) shows the XRD di raction pattern graphics for a sample containing a 5% BA and 5% BWIA mix (BA and BWIA 10). e predominance of quartz peak values has been observed around 2theta degrees of 27.5°, while portlandite peak values have been observed around 2theta degrees of 18°. e XRD di raction pattern graphics of the 7.5% BA and 7.5% BWIA mixes with partial replacement of the cement mix ratio samples are shown in Figure 9(d). e dominant peaks of quartz are 2theta degrees of 27.5°, portlandite is 18°a nd 30°, and ettringite is 26°and 34.7°.

SEM Analysis.
Concrete has a highly complex and heterogeneous microstructure, which consists of three components such as cement paste, the interfacial transition zone between the cement pastes and aggregates, and the pore's structure. To develop these three components to improve the mechanical strength and durability of highstrength concrete [49], SEM images illustrate the microstructure and surface morphology of C-S-H gel, calcium hydroxide (CH), pores, and ettringite in concrete. e e ect of BWIA and BA on the workability, mechanical, and durability properties of concrete can be described by microstructure. When BWIA and BA were partially replaced to cement mix ratio to concrete the size of crystal and pores is smaller, and the bonding between the crystals becomes tighter, which makes the microstructure denser. Figures 10 and 11 show SEM images of the control mix (BA and BWIA 0), 2.5% BA and 2.5% BWIA mix (BA and BWIA 5), 5% BA and 5% BWIA mix (BA and BWIA 10), and 7.5% BA and 7.5% BWIA mix (BA and BWIA 15) cured for 28 days at 20 µm with a resolution of x1000 magni cation rate and 50 µm with an x500 magni cation rate. Figures 10(a) and 11(a) show SEM images of the control mix microstructure without partial replacement of BA and BWIA. After 28 days of curing, it is shown that several outstanding blacks are pore structures that are distributed within the control mix samples. It is more permeable when compared to BA and BWIA5, BA and BWIA10, and BA and BWIA15 mix code SEM images. e porosity of concrete has a signi cant impact on its strength. e pore structure and the structure's limited durability have both contributed to increased permeability. e micromorphology of the SEM images was presented in Figures 10(b) and 11(b), using a 2.5% BA and 2.5% of BWIA (BA and BWIA 5) combined e ect. SEM pictures of this mix do not show visible pores, indicating a denser microstructure than SEM images of the control mix. It indicates that the in uence of the pozzolanic reaction changes the pore structure with the decrease in the grain size. e replacement of cement with up to 2.5% of BA and 2.5% of BWIA increases the strength and durability and decreases the permeability of concrete. e bright particles indicate a nonhydrated cement or whiter C-S-H gels around the aggregates. e BA and BWIA in the mix remain unreacted due to the lack of hydration of grain particles in the mix at the age of 28 days, which also needs more curing time to complete the hydration process. ere is less pore structure compared to the control mix SEM images and the BA and BWIA 15 mix SEM images; therefore, better compressive strength is achieved compared to the control mix compressive strength. e main phases in the microstructure of the hydrated cement mix paste can be seen as hexagonal and cube calcium hydroxide (CH) structures. According to Paul E. Stutzman et al. [50], SEM images show the hexagonal shapes of calcium hydroxide, needle-like is ettringite, and sheet-like is calcium silicate-hydrate. From the SEM image, the microstructure of high-strength concrete is more homogeneous than that of the SEM image of the control mix due to the chemical and physical contributions of BA and BWIA.
In Figures 10(d) and 11(d) shown, the micromorphology of the SEM images was presented with 7.5% BA and 7.5% of BWIA mix (BA and BWIA 15). e darker areas represent pores. Compared to control mix micromorphology, BA and BWIA 15 SEM images have fewer pores. e bright particles indicate that the aggregates are surrounded by a nonhydrated cement or a whiter C-S-H gel. When increasing the partial replacement of cement by BA and BWIA mix curing periods to 28 days, the hydration of cement is not completed. e increased curing periods of 28 days to 56 days and 90 days increase the hydration rate, leading to better mechanical properties for high-strength concrete and the microstructure.

Conclusion
e following conclusions were drawn from the experimental results of biomedical waste incinerator ash and bagasse ash properties, e ects on fresh and hardened high-strength concrete properties, and microstructure of concrete.
(1) e replacement percentage of BWIA and BA increases the slump, owability, and compaction factor, and density of fresh concrete decreases. (2) At an early age of curing, the replacement percentage of BWIA and BA increases compressive strength, and split tensile strength decreases. At 28 days of curing, up to 10% replacement of the BA and BWIA can improve the mechanical properties of highstrength concrete. (3) According to SEM images, a partial replacement of the cement mix ratio by bagasse ash and biomedical waste incinerator ash results in a denser C-S-H gel with fewer pores than the control mix. Furthermore, improved interlocking between aggregate and cement paste leads to improved mechanical properties in high-strength concrete. Partial replacement of the cement mix ratio by BA and BWIA results in a decrease in the pore proportion in the enlarged ITZ, reduced CH crystals, and a denser C-S-H gel when compared to control mix concrete. XRD could be used to identify the mineralogical components of the hydrated cement paste powder. e XRD data revealed the presence of hydration products like portlandite, ettringite, quartz, calcite, and okenite (hydrated C-S-H), as well as other mineral compounds that would hydrate over time.
Lastly, biomedical waste incinerator ash and bagasse ash are waste products materials from medical waste incinerator centers and the sugarcane industry. eir use as a partial replacement for cement reduces the levels of CO 2 emissions by the cement production process, and their use resolves the disposal problems associated with them in medical waste incinerator centers and sugarcane factories [51][52][53][54].  Figure 11: SEM images x500 magni cation rates of (a) control mix, (b) 2.5% BA and 2.5% of the BWIA mix (BA&BWIA 5), (c) 5% BA and 5% of the BWIA mix (BA&BWIA 10), and (d) 7.5% BA and 7.5% of the BWIA mix (BA&BWIA 15).