Reduction of hazardous incinerated bio-medical waste ash and its environmental strain by utilizing in green concrete

Incinerated Bio-Medical Waste Ash (IBWA) is toxic waste material with broad potential (cancer, genetic risk, premature death, permanent disease) to in ﬂ ict severe health damage for the atmosphere and humans. This waste is disposed of as land ﬁ lls which contaminate the underground water and environment. The effective way of disposal of IBWA is by utilizing it as a building material which can reduce the hazardous toxic materials. The use of Geopolymer Concrete (GPC) combined with IBWA as a substitute for Ground Granulated Blast Furnace Slag (GGBS) has been researched for its ability to create a new type of Green Concrete. The physical and chemical properties were observed for the raw materials. IBWA was used at 0, 5, 10, 15, 20, 25, 30, 35, 40, 45 and 50% replacement by weight for GGBS. Mixing proportions were 1:2.21:3.48 respectively for GGBS, Manufacturing Sand (M-sand), and coarse aggregate. Fresh properties and Mechanical properties were examined on all specimens. The ﬁ ndings show an increase in the setting time and ﬂ ow of concrete and a decrease in density with improved utilization of IBWA. On the other hand, IBWA replacement for GGBS enhanced the mechanical properties. These results revealed that IBWA could be partially replaced as source material for Geopolymer Concrete. This research may contribute to the reduction of dangerous IBWA as a building material.


INTRODUCTION
Over the last few decades, the amount of waste being generated has risen dramatically. Solid waste includes the heterogeneous mass of urban waste and homogenous deposition of mineral, industrial and agricultural waste. Waste created from biomedical processes is a significant concern for the living ecosystem and the human world (Mastorakis et al. 2011;Wang et al. 2020;You et al. 2020). Hospital waste or Bio-Medical Waste is a distinctive form of waste. According to the 1998 Indian rules on bio-medical wastes (management and handling), 'Bio-Medical Waste means any waste which is generated during the diagnosis, treatment or immunization of human beings or animals or in research activities pertaining to it or in the production of biological testing and including different categories'. It is more hazardous due to its toxic and infectious characteristics (Zile Singh et al. 2001;Lo et al. 2020;Wei et al. 2020). Dealing with waste has been a growing environmental concern in many developed countries (Azni & Katayon 2002).
Generally, India generates around 517 tonnes of hazardous waste every day. Several types of treatment and disposal processes have been implemented for hospital waste. However, to reduce the hazardous waste volume, incineration has been identified as the best option. However, it would produce an immense amount of waste as toxic ash containing significant quantities of heavy metals [mercury (Hg), Arsenic (As), Lead (Pb), Cadmium (Cd), Silver (Ag), Iron (Fe), Zinc (Zn)], which have the potential to contaminate soil and groundwater (Al-Mutairi et al. 2004;Chen et al. 2016;Gao et al. 2017;Tome et al. 2018;Loginova et al. 2019;Maldonado-Alameda et al. 2020;Zhuguo et al. 2021). About 0.82 lakh MTA (metric tonnes per annum) as ash in the world is caused by the incineration of 3.27 lakh MTA of harmful waste (CPCB 2018). A suitable waste disposal system must be used to dispose of toxic biological waste, and incineration is the appropriate way to minimize the amount of such hazardous waste. In the process of incineration, the bacteria are killed, lower the volume and weight of waste. But, being incinerated, this waste leaves behind biomedical ash (BMA), which raises the concentrations of hazardous metals, inorganic salts, and organic compounds in the atmosphere (Giro-Paloma et al. 2017;Yakubu et al. 2018;Phua et al. 2019;Kondo et al. 2020). Metals in BMA are not generally removed during incineration. These metals will cause groundwater contamination by leachate (Valavanidis et al. 2008;Agamuthu 2009;Ozturk et al. 2011;Anastasiadou et al. 2012;Jawaid & Kaushik 2012;Krishnamurthy & Chella purushothaman 2019). Our culture is gradually conscious of the appropriate ways to treat bio-medical waste, applied to the development of various engineering structures (Al-Rawas et al. 2004;Hou et al. 2020).
It has been researched and evaluated that many experiments have focused on establishing the feasible containment structures of Hospital Waste Ash (HWA) or Bio-Medical Waste Ash, or Incineration Ash in engineering applications. About 72 percent of plastic waste is reused in Denmark to create cycling tracks, parking areas, and other roads. 60% of the bottom ash is utilized to develop various types of roads in the Netherland. In Germany, 50% of the incinerated waste ash is used to create sub-layers on the streets and state roads with acoustic insulation panels (Reijnders 2005). Bio-medical waste ash can be used in agriculture due to the diversity of nutrients it provides but no organic carbon or nitrogen (Goswami 2007). Among them, materials based on cement were examined (Giaccio & Malhotra 1988;Mehta 1997;Schiessl & Hohberg 1997;Genazzini et al. 2000Genazzini et al. , 2003Genazzini et al. , 2005 to access the Incineration Ash or Hospital Waste Ash in concrete. Previous research (Genazzini et al. 2000(Genazzini et al. , 2003(Genazzini et al. , 2005 tested the Hospital Waste Ash with cement-based materials. (Al-Rawas et al. 2004) studied the use of Incineration Ash as a substitute for sand, cement and reported that cement containing 20% replacement of Incineration Ash had yielded high compressive strength than control concrete. Fine aggregate containing 40% Incineration Ash has exhibited high compressive strength than control concrete. Laboratory tests have shown that most scientists and engineers have used hospital waste ash (HWA) or bio-medical waste ash, or incineration ash for the concrete to replace cement.
The use of cement itself is a significant source of environmental pollution (Mehta 1999;Mehta & Burrows 2001). Like several other reports, plenty of research has been carried out to replace cement with Geopolymer Technology (Davidovits 1993(Davidovits , 2002Arbi et al. 2016;.
There is no concern about the incinerated bio-medical waste ash used as an aluminosilicate source material for GPC. Geopolymer concrete with Incinerated Bio-Medical Waste Ash will be green concrete. This research paper is intended to use the Incinerated Bio-Medical Waste Ash in Geopolymer Concrete as a partial substitute for Ground Granulated Blast Furnace Slag. In addition, this paper aims to establish a new binder for GPC synthesis. The successful utilization of IBWA would reduce the cost of the construction and reduce the environmental hazards. The research aims to examine a new form of GPC with GGBS as source material and IBWA as its partial substitute for GGBS. The influence of applying IBWA on microstructure, fresh properties, and mechanical properties was analyzed for up to 28 days.

MATERIALS AND METHODS
2.1. Materials 2.1.1. Ground granulated blast furnace slag (GGBS) In this analysis, the primary aluminosilicate source material used to manufacture GPC is GGBS, which was then processed and used to produce a polymer binder by GGBS. GGBS was collected from the Local steel Plant, Kappalur, Madurai. The physical and chemical characteristics are described in Tables 1 and 2, respectively. Energy Dispersive X-Ray Spectroscopy (EDX) is used to find the Chemical contents of GGBS, and Scanning Electron Microscope (SEM) is used to find the microstructure of GGBS, as shown in Figure 1(a) and 1(b).

Incinerated bio-medical waste ash (IBWA)
The IBWA is obtained from Ramky Energy and Environment Ltd Kariapatti, Virudhunagar in the present study. The physical and chemical characteristics are described in Tables 1 and 2, respectively. X-Ray Powder Diffraction  Uncorrected Proof (XRD) is used to find the chemical composition of IBWA, and SEM to find the microstructure of IBWA shown in Figure 1(c) and 1(d).

Alkaline solution
A mix of sodium silicate solution (Na 2 SiO 3 ) and sodium hydroxide solution (NaOH) was the alkaline solution selected for analysis, as sodium solution is less expensive than potassium-based solutions.
To produce an alkaline solution, NaOH and Na 2 SiO 3 are first combined at ambient temperature. Polymerization will generally occur when the solution is mixed. Huge volumes of heat are emitted with polymerization. The alkaline solution is therefore recommended to prepare before 24 hours. The appearance of the NaOH is white in colour, and it is solid in nature. The density and molar mass of NaOH is 2.1 g/cc and 40 g/mol, respectively. The appearance of the Na 2 SiO 3 is white in colour, and it is opaque crystal in nature. The density and molar mass of Na 2 SiO 3 is 2.6 g/cc and 122.06 g/mol, respectively.

Manufactured sand (M-sand)
M-sand according to zone II included in this analysis and the subsequent studies has been carried out in compliance with IS: 2386-1968 part III as a fine aggregate. The specific gravity and fineness modulus of M-Sand is 2.61 and 2.76, respectively.

Coarse aggregate
In this current study, commonly accessible coarse aggregate with 10 mm maximum size has been used. The aggregates are washed away and allowed to dry on dry surfaces to extract debris and gravel. The specific gravity and fineness modulus of coarse aggregate is 2.64 and 7.03, respectively.  Uncorrected Proof (aluminosilicate). IBWA included all eleven blends from 0 to 50% of the total content of aluminosilicates. Aluminosilicate source material was replaced with IBWA at 0,5,10,15,20,25,30,35,40,45 and 50% as  IBWA5, IBWA10, IBWA15, IBWA20, IBWA25, IBWA30, IBWA35, IBWA40, IBWA45 and IBWA50. The alkaline solution used for this analysis is sodium hydroxide (NaOH) and sodium (Na 2 SiO 3 ) with a molarity of 13. The proportion of NaOH and Na 2 SiO 3 is fixed at 1:2.5. The solution/binder ratio of 0.61 by weight was maintained. Table 3 presents the mixed proportions of Geopolymer concrete with and without IBWA.

Preparation and casting of test specimens
According to Indian Standard BIS 10262:2009, the Geopolymer concrete mix proportion was specified for the required strength, with updated guidelines for the Geopolymer concrete mix design. The quantity of materials to make the concrete mix is measured. Dried ingredients (GGBS, IBWA, coarse aggregate, and fine aggregate) were mixed in a mixer. Then alkaline solution, which was prepared 24 hours earlier, was mixed to produce standardized Geopolymer concrete. The casting method was carried out directly after mixing and checking for fresh properties as per BIS: 1199-1959. The strength of concrete was measured in three ways. First was by casting a cube (150 mm Â 150 mm Â 150 mm) and testing a compressive strength. The second was casting a cylinder (100 mm Â 200 mm) and measuring split tensile strength. The third was casting a prism (100 mm Â 100 mm Â 500 mm) and evaluating the flexural strength. The samples were held for almost a day and subsequently maintained at a temperature of 27°+ 2°C. They have been separated from the molds and then preserved to the testing requirements for ambient curing.

Fresh properties
Geopolymer concrete flow capability was measured using an ASTM C230 flow table method. The flow table is a primary method for calculating the movement of cement pastes and cement hydraulics. The setting time of specimens examined on the Vicat apparatus was possible to evaluate and assess the final and initial setting time of the sample tested on the instrument (according to ASTM C191 standard).

Mechanical properties
In accordance with ASTM Test Standard C39, the compression strength test was conducted. For compressive strength testing, 66 cubes (150 mm Â 150 mm Â 150 mm) of size have been prepared. Tests were carried out on a one-week duration (7 days) on the first occasion and a four-week time (28 days) on the second occasion using a Universal Testing Machine (UTM) controlled with displacement. According to ASTM C496, splitting tensile experiments were performed, which are an indirect way of calculating the tensile strength. For this test, 100 mm Â 200 mm cylindrical samples have been used. Depending on ASTM C293, the flexural strength tests

Fresh properties
Two different tests were performed on fresh concrete, one regarding flow and the other is setting time. Figure 2(a) and 2(b) display the flow and setting time of various mixes of GPC. With an increasing percentage of IBWA replacing GGBS, the concrete flow increased due to varying chemical reactions and physical properties. Increasing IBWA content also decreased calcium content. In addition, the amount of silicate and aluminium was increased. Increased silicate content helped improve the concrete flow efficiency. In addition, the GGBS content has been reduced by increasing IBWA volume, which increases the flowability of the mixture. The particle size fineness of IBWA has also led to the improved workability of the concrete (90% less than 45 microns). Similar patterns have also been identified previously (Sofi et al. 2007), where particle size is the main variable and impacts mortar dissolution and flow. Also, the combination of the IBWA and GGBS slowed down the setting time and improved workability. Figure 2(a) describes these improvements, verified by (Al-Majidi et al. 2016). The relation between the flow (y) and Percentage of IBWA in GPC (x) for fresh concrete is obtained as y ¼ 0.0448x 2 À 0.0771x þ 12.731. R 2 value close to 1 and shows that there is a good correlation of results. Based on previous results, there was a decrease in calcium content in the mortar, which led to an increase in the setting time (Sofi et al. 2007;Phoongernkham et al. 2015;Lee et al. 2016). In addition, improved IBWA levels Uncorrected Proof also improved SiO 2 and Al 2 O 3 levels, increasing setting time (Chindaprasirt et al. 2012). The setting rate was significantly enhanced due to the minor disparity between the initial setting time and the final setting time. As the GGBS content was reduced in the concrete, the discrepancy between initial and final setting time improved. The finding is that with the more significant amount of GGBS in the mortar, the setting rate is faster (Sugama et al. 2005;Kumar et al. 2010) is also confirmed by this result. It is therefore known that GGBS is highly successful in decelerating the setting period of GPC under atmospheric conditions as part of the binary blended binder. Figure 2(b) indicates the impact on GPC setting time of IBWA substituted GGBS.

Effect of IBWA on GPC density
With an increasing percentage of IBWA replacements, GPC density was found to decrease. The GPC density was derived from the specific gravity and the size of the particles of IBWA. Thus, increasing Al 2 O 3 and SiO 2 content contributed to the production of Sodium Aluminosilicate Hydrate (NASH) gel and Calcium Silicate Hydrate (CSH) gel, respectively. The formation of NASH and CSH gels improved the GPC microstructure, as seen earlier (Deb et al. 2014). Figure 2(c) indicates the effect on the GPC density of the GGBS substituted by IBWA. The relation between the Density (y) and Percentage of IBWA in GPC (x) for fresh concrete is obtained as y ¼ À 4E À05 x 2 À 1.7775x þ 2441.9. The R 2 value is one and shows that there is a good correlation between results.

Compressive strength
The impact of different substitution percentages of GGBS and IBWA on the compressive strength of various Geopolymer mixes after 7 and 28 days of preparation are shown in Figure 3(d). The compressive strength for 7 and 28 days is 27 MPa and 33.2 Mpa, respectively, for the Geopolymer concrete mix without IBWA. When tested in the lab, it was noticed that the Geopolymer concrete mix IBWA30 had a marginally higher compressive strength than the other blends and that the strength begins to decline as the IBWA content rises from 35 to 50 percent (see Figure 3(d)). GGBS is primarily responsible for early age intensity (Duxon et al. 2007;Deb et al. 2014), whereas Incinerated Bio-Medical Waste Ash (IBWA) is responsible for enhanced strength at a later age; thus, a higher rise in compressive strength at 28 days has been noted. More precisely, it is shown that the compressive strength at 28 days 43.3 MPa (30.42%) of age is greater than the compressive strength at the 7 days 32.5 MPa (20.37%) of age for the IBWA30 mix. The majority of the compressive strength achieved has been contributed by IBWA. GPC mixtures substituted by 30 percent of IBWA with GGBS have indicated an increased compressive strength due to the micro-filler effect (Suresh Kumar et al. 2020). The trend of strength attainment of 100 percent GGBS (IBWA0) mixture is similar to 55 percent GGBS and 45 percent IBWA (IBWA45) mix. The rise in IBWA content above 30% reduces the strength of the Geopolymer mixtures. As a consequence of the curing period has reduced, there is an improvement in the geopolymerization process. In Geopolymer concrete, Geopolymerisation process takes place in the early age itself and there is no later age strength attainment. Figure 3(a)-3(c) shows that when IBWA 30% is incorporated in GPC, it produces more CSH and calcium aluminosilicate hydrate (CASH) gels during the hydration process. The spherical shape with white colour in the SEM image is CSH gels. Due to the formation of CASH and CSH, the strength improvement is significant in the IBWA30 mix.
Many GPCs are currently generated with growing concentrations of Al 2 O 3 and SiO 2 , which improve the phase of geopolymerization and the amount of GPC [sodium aluminosilicate hydrate (NASH), calcium aluminosilicate hydrate (CASH), and calcium silicate hydrate (CSH)] gel. These also contributed to an improvement in the strength of the GPC (Dombrowski et al. 2007;Husein et al. 2016;Chithambar Ganesh & Muthukannan 2019a;Arunkumar et al. 2020Arunkumar et al. , 2021. CSH and CASH are produced in the hydration process of Portland cement. At the same time, NASH is a geopolymeric gel, and it improves the early age strength of the ambient geopolymer concrete (Lee & van Deventer 2002;Yip & van Deventer 2003;Yip et al. 2005;Temuujin et al. 2009;Diaz et al. 2010;Guo et al. 2010;Rattanasak et al. 2011;Chindaprasirt et al. 2012). Beyond 30% replacement of IBWA in GPC strength tends to decrease owing to the tremendous level of calcium (only a minimal amount of adequate CSH gel can develop).
The regression study was conducted for 7 and 28 days of GPC compressive pressure under ambient conditions. The relation between the compressive intensity (y) and the percentage of IBWA (x) for 7 and 28 days under ambient curing is obtained by y ¼ À0.0533x 3 þ 0.7141x 2 À 2.0099x þ 27.347 and y ¼ À0.0177x 3 À 0.003x 2 þ 2.3359x þ 31.012 as shown in Figure 3(c). R 2 values for 7 and 28 days are 0.81 and 0.91. Compared to 7 days, the 28-day regression study has a good correlation of results.

Splitting tensile strength
A total of 66 cylindrical samples were prepared. For the Geopolymer concrete mix (IBWA0) consisting only of GGBS as a binder and processed using 13 M NaOH solution, the split tensile strength was 3.7 MPa after 28 days (see Figure 4). For the IBWA0 mix test was conducted, the findings were consistent that the mix performed the same pattern as the compressive strength and turned out to be the weakest specimen of all (see Figure 4). This is occurring because of the high calcium content of the binder material, which might not be sufficient to support the split tensile strength (Singh et al. 2015). The IBWA30 mix reveals a 4.08 MPa (23.63 percent) improvement in strength over the IBWA0 mix. On subsequent replacement of GGBS with IBWA, there is an increase in strength from 6.96% to 23.63% for mix IBWA5 to IBWA50.
This growing pattern specifically reveals the maximum increase in strength for the 30% of IBWA substituted for GGBS. When the volume of IBWA was increased, the amount of silica and alumina was also increased in the matrix. The high level of the calcium content in the binder adversely affects the later age strength and increases the setting time. Also, it indicates a lower rate of polymer forming in the mixture at later age (Alonso & Palomo 2001;Komljenovićet al. 2010;Rashidian-Dezfouli et al. 2018). The tensile strength tests showed clearly the possibility of using IBWA in GPC as new alternative source material. Few sources have reported similar patterns (Phoongernkham et al. 2015). Figure 4 reveals that the split tensile strength of GPC improved after replacing IBWA.
The Regression analysis has been performed for the 7 and 28 days split tensile strength of GPC under ambient cured condition. The relation between the split tensile strength (y) and percentage of IBWA (x) for 7 and 28 days under ambient curing is obtained y ¼ À0.0044x 3 þ 0.0595x 2 À 0.1684x þ 2.8242 and y ¼ À0.0013x 3 À 0.0007x 2 þ 0.1834x þ 3.1256 respectively as shown in Figure 4. R 2 Values for 7 and 28 days are 0.81 and 0.91 respectively. Compare to 7 days, 28 days regression analysis has good correlation in results.

Flexural strength
A 28-day flexural strength of 4.98 Mpa was estimated without IBWA Geopolymer Mix (IBWA0), which consists of the only GGBS in the form of a binder and was triggered using 13 M NaOH (see Figure 5). When evaluated on the various mixes, it was observed that the IBWA0 mix follows the same trend as observed for compressive and split tensile strength and is the lowest of all the combinations (see Figure 5). By combining IBWA30 with IBWA0, the strength of IBWA30 is (8.227 MPa) 65.2% greater than IBWA0's strength. A strength increase of 16.3% to 65.2% at 28 days was observed when IBWA was replaced with GGBS in mix IBWA 5 to IBWA50.
The result reveals that the maximum increase in strength has occurred for the 30% of the IBWA, which has been substituted for GGBS. In addition to the CSH gel (Chithambar Ganesh & Muthukannan 2019b; Uncorrected Proof , geopolymerisation led to the dissolution of SiO 2 and Al 2 O 3 and the development of NASH and CASH gel. This illustrates that GPC is more resistant to the 100% GGBS sample, dependent mainly on the calcium silicate hydrates (CSH). The flexural strength of GPC prisms is displayed in Figure 5.
The Regression analysis has been performed for the 7 and 28 days Flexural strength of GPC under ambient cured condition. The relation between the flexural strength (y) and percentage of IBWA (x) for 7 and 28 days under ambient curing is obtained y ¼ À0.0127x 3 þ 0.1534x 2 À 0.2507x þ 4.0105 and y ¼ À0.0088x 3 þ 0.0591x 2 þ 0.4356x þ 4.5246 respectively as shown in Figure 5. R 2 Values for 7 and 28 days are 0.83 and 0.89 respectively. Compare to 7 days, 28 days regression analysis has good correlation in results.

CONCLUSION
The result of using IBWA to substitute GGBS partially in GPC was studied. At ambient temperature, the GPC performance test was conducted. The following results are drawn based on the findings: 1. IBWA substituted GGBS enhanced GPC's workability by improving the setting time and reducing the density by raising the volume of aluminium and silicate. 2. From SEM-EDS study, the IBWA incorporated with 30% in GPC have a good geopolymerisation and forms CSH, CASH gels. Due to formation of these gels the strength increases. Beyond 30% replacement of IBWA in GPC, the strength reduces due to high calcium content in binder and less geopolymerisation. 3. Compared to the samples of 100% GGBS, 30% of IBWA replacement improved 23.01% in compressive strength. The main reason for this is the micro-filler effect and formation of CSH and CASH gels. 4. The Split tensile strength was 18.26% higher compared by 30% substitution to IBWA relative to the 100% GGBS samples. 5. 30% replacement of IBWA improved Flexural strength by 55.81% compared to 100% GGBS samples. This is due the good geopolymerisation process and formation of CSH and CASH gels to become a pore structure.
This research work opens up plenty of possibilities for utilizing harmful toxic Incinerated Bio-Medical Waste Ash (IBWA) as an aluminosilicate raw material to develop geopolymer concrete, thereby addressing the environmental and disposal problems of IBWA. It can been used as a building material in the construction field for various applications.

ACKNOWLEDGEMENT
The authors would like to thank the Kalasalingam Academy of Research and Education for providing Equipment for testing and conducting research.

FUTURE STUDY
Durability studies over a long period should be conducted to support the materialization of IBWA in the production of green concrete.

DATA AVAILABILITY STATEMENT
All relevant data are included in the paper or its Supplementary Information.