Utilization of Different Grain Size of Municipal Solid Waste Bottom Ash in High-Performance Mortars

Abstract

Globalization is bringing increased industrialization and municipal solid waste (MSW). This is a major concern in heavily populated areas. In order to reduce MSW generation, incineration is commonly used, resulting in two types of ashes: bottom and fly ash. Bottom ash is gathered at the incineration bed and is larger in mass than fly ash. To test the qualities of high-performance mortar, MSW-BA in three sizes (fine, medium, and coarse) was replaced with sand at three replacement levels of 10%, 20%, and 30%. The high-performance mortar integrating MSW-BA was tested for hardened density, mechanical properties such as compressive and flexural strength, resistance to NaOH solution, and heavy metal leaching. The substitution level of MSW-BA increased the hardened density of the mortar mixes. The volume change and residual strength of the mortar mixes were measured following exposure to the NaOH solution. Fine-particle mortar mixes shrank whereas medium- and coarse-particle mortar mixes expanded. The largest loss in flexural and compressive strength was recorded when 20% of sand was replaced with a fine fraction of MSW-BA. Heavy metals including cadmium and copper were not leached from MSW-BA combinations of any size. The minuscule amounts of lead and zinc discovered were well below acceptable limits. The present study illustrates the MSW-BA can be utilized as a substitute for sand in the development of high-performance mortar.

1. Introduction

The incineration of municipal solid waste (MSW) is becoming more common worldwide. There is a generally recognized need to limit the amount of waste dumped in landfills, and this is especially true in highly industrialized and densely populated countries such as Japan and the United Kingdom, but it is also a worry for the entire world [1]. MSW includes solid and semi-solid waste generated in urban daily life and services. Due to rapid urban development, high-rise buildings, and increased consumption of residents, a large number of MSW, if inadequately managed, is the main source of environmental pollution (marine plastic accumulation, greenhouse gas emissions, phytotoxicity, etc.) [2], and the impact is significant. Currently, only 14% of MSW in the world is recycled and reused, and 70% of MSW is dumped and landfilled [3]. In terms of safety and the environment, it is very important to deal with challenging obstacles such as dumping and landfill of solid waste [4]. The total volume of MSW in China is predicted to increase from 31.3 million tons in 1980 to 480 million tons by 2030 [5]. Currently, many countries have different research and reuse techniques for MSW dump. The incineration of MSW has become a commonly acknowledged solution worldwide. Due to their complicated composition and potential threats to the environment and human body, the by-products of MSW incineration are reasonable. Recycling and safely reusing them are critical for long-term waste management. Building materials, cement, road construction curbs, soil supplements, (metal, energy) restoration, and geopolymers are all examples of MSW sustainable use approaches [6].

During the production of the MSW, two types of ashes are obtained. MSW incinerated bottom ash (MSW-BA) was collected at the bottom after the incineration and Municipal solid waste incinerated fly ash (MSW-FA) was collected during the burning process using various methods [6,7]. The MSW-BA makes up around 80% of the solid residue generated by MSW combustion and 30% of the overall incineration volume [8]. Glass and ceramics (15–30%), metals (2–50%), minerals (50–70%), and other unburned substances make up the majority of MSW [9,10]. MSW-BA is alkaline and contains hazardous chemical compounds like dioxins, as well as hard-to-leach metals including silicon (Si), iron (Fe), calcium (Ca), aluminum (Al), sodium (Na), potassium (K), and others [11]. Most MSW-FA is spherical and powdery, with light and tiny particles (5–20%). FA is classified as a dangerous substance in many nations. It has a high concentration of dioxins, heavy metals, and soluble salts, just like BA. FA, on the other hand, is more hazardous than BA because it contains heavy metals that are more water-soluble, such as lead (Pb), chromium (Cr), Cadmium (Cd), mercury (Hg), arsenic (As), and antimony (Sb), and regarded as a hazardous material [12].

Aiming at the application of MSW in concrete, Mangialardi [13] conducted research on MSW-FA in 2001 and found that the MSW-FA, after preliminary washing, can meet the strength of concrete. The compaction pressure is 28 N/mm^2, and the sintering temperature is 1140 °C. MSW was treated with a sintering time of 60 min, producing the favorable sintered material in making concrete [13], followed by Sikalidis [14], who studied and demonstrated the feasibility and advantages of this method in 2002. Similarly, researchers investigated the casting techniques on Supplementary Cementitious Materials (SCM) with MSW-BA [15], with different kinds of cement (calcium aluminate cement, asphalt cement, Portland cement) [16,17] and geopolymer to prepare mortar with MSW [18]. When MSW bottom ash is used as aggregate in the cement composite, the aluminum-induced hydrolysis reactions can lead to hydrogen gas generation, which can induce porosity and have a detrimental effect on the cement composite [19]. The amphoteric properties of aluminum allow it to react with acidic and alkalis. In acidic solutions, the strong Al³⁺ ion is the dominant ion, which is then carried by the solution until it is sufficiently acidic to allow the solid hydroxide to form. At elevated pH, gibbsite dissolves in favor of aluminate ions; [Al(OH)]₄]⁻ and in a cement pore solution (pH 12.5–13.5), solid hydroxide is absent at equilibrium (Equation (1)). When bottom ash is exposed to a cement pore solution, the aluminum in the ash dissolves, creating hydrogen gas bubbles. This is a somewhat fast process that will mechanically interrupt the creation of a continuous network of CSH, particularly near the original aluminum grains, where voids may emerge during the setting process. If the aluminum is mostly in the form of Al(OH)₃ (gibbsite), exposure to alkaline conditions will speed up its breakdown without releasing hydrogen (Equation (2)). Müller and Rübner [19] discuss the mechanism and consequence of aluminum-induced hydrolysis when MSWI bottom ash aggregates are used in concrete, showing the nature of the porosity induced and the form of the reaction products alongside other detrimental reactions.

$$\begin{gathered} 2\mathrm{Al}+2{\mathrm{OH}}^{-}+6{\mathrm{H}}_2\mathrm{O}\to 2{\left[\mathrm{Al}{(\mathrm{OH})}_4\right]}^{-}+3{\mathrm{H}}_2\left(\mathrm{gas}\right) \\ \mathrm{Aluminum}+\mathrm{Hydroxide}+\mathrm{Water}\to \mathrm{Aluminate}\mathrm{ion}+\mathrm{Hydrogen}\mathrm{gas} \end{gathered}$$

(1)

$$\begin{gathered} \mathrm{Al}{(\mathrm{OH})}_3+{\mathrm{OH}}^{-}\to {\left[\mathrm{Al}{(\mathrm{OH})}_4\right]}^{-} \\ \mathrm{Aluminum}\mathrm{hydroxide}+\mathrm{Hydroxide}\to \mathrm{Aluminate}\mathrm{ion} \end{gathered}$$

(2)

Self-compacting cementitious materials (SCCM) do not require vibration and flow densely under autogenous gravity’s action with a uniform texture. The mortar’s rheology and dynamic stability are the two most critical factors [20]. Various researchers have utilized ash from MSW to understand the influence of various kinds of ash on different cementitious materials. Some researchers have looked into using various cementitious materials, including FA, to make Self-Compacting Concrete (SCC), and found that its physical and mechanical properties can meet the durability requirements [21]. Pawan Kumar et al. [22] investigated the effects of recycled concrete aggregate and coal bottom ash on SCC properties. Simões [23] and Simões [24] utilized MSW-BA into ternary mixes of SCCM as a cement substitute. Results showed that due to the presence of the calcite in the MSW-BA, the decline in the compressive strength was observed in the mixes. Taherlou et al. [21] utilized the MSW-BA and treated industrial wastewater. Results showed that the MSW-BA, along with treated industrial wastewater, reduces the fresh properties of the SCC [21]. However, there are a few of the selected studies shown in

Table 1. Selected previous study with MSW-BA as aggregates.

References	Focus of the Study
(Li et al., 2018) [25]	MSW-BA as coarse aggregate in autoclaved aerated concrete
(Zhang et al., 2020) [26]	Eco-admixture made from MSW
(Cristelo et al., 2020) [11]	MSW as precursor in alkaline cement
(Casanova et al., 2021) [27]	Alkali-activated MSW-BA as fine aggregates
(Long et al., 2021) [18]	Eco-friendly geopolymer mortar with MSW-FA and ferronickel slag as aggregates
(Shen et al., 2021) [28]	Utilization of MSW-BA aggregates in pervious concrete
(Taherlou et al., 2021) [21]	Investigation of MSW-BA as aggregates in self-compacting concrete
(Velusamy et al., 2022) [29]	Utilization of MSW inert replacement with fine aggregates
(Yaphary et al., 2022) [30]	Utilization of MSW-BA and GGBS along with concrete slurry waste as aggregates in mortar
(Mafalda Matos and Sousa-Coutinho, 2022) [31]	Feasibility of fine MSW-BA incinerated at (between 1000–1200 °C) as aggregate

where the MSW-BA is used as coarse or fine aggregate, but there is no study as per the authors’ knowledge that focuses on the utilization of MSW-BA with different grain size in high-performance concrete. However, no study focuses on the utilization of the different grain size of the MSW-BA in high-performance concrete.

The overall aim of the present study was to assess the grain size effect on the properties of high-performance cementitious composites. Based on the authors’ previous research [32,33,34], which is also based on the utilization of the specific grain size and also the different kinds and size of materials in the incinerated BA shows that some grain size contain more glass and some contains more burnt particles, which can have differential effect on the final product, authors choose three different grain sizes of the MSW-BA (fine sand (0.15–0.3 mm); medium sand (0.3–0.6 mm); coarse sand (0.6–4.75 mm)) were utilized in this study to produce high-performance mortar. The physicomechanical properties of MSW-BA high-performance mortar (MBHPM) were investigated along with the shrinkage performance of MBHPM. Additionally, to evaluate the environmental safety of the utilization of MSW-BA, leachate toxicity assessment was performed on the samples. The results prove that utilization of the MSW in high-performance mortars can have a positive impact on the environment.

2. Materials and Methods

2.1. Materials, Mix Design, and Specimen Casting

A standard 42.5 PO type cement conforming to Chinese Standard GB 175 [35] was used as binder in this study. Fine aggregates with water absorption of 0.1% and a fineness modulus of 2.36 were used in this study. MSW was acquired from an incinerator plant in Beijing. The MSW was washed with hot water and under a pH of 12 to reduce the mobilization of heavy metal. After washing and drying, the MSW was divided into three grain sizes (4.75–0.6 mm as coarse sand replacement, 0.6–0.3 mm as medium sand replacement, and 0.3–0.15 mm as fine sand replacement). The natural sand was replaced with three different sizes of MSW-BA in three different replacement ratios (10%, 20% and 30%). Figure 1 shows the grain size distribution of natural sand and MSW-BA. The chemical and physical properties of MSW and cement used in this study is presented in

Table 2. Chemical composition of MSW and cement.

Oxides	MSW (Different Grain Size)			Cement
	4.75–0.60 mm	0.60–0.30 mm	0.30–0.15 mm
	(%)
Al2O3	6.26	7.80	10.87	4.42
BaO	0.33	0.27	0.24	-
CaO	17.94	21.59	26.83	64.9
Cl	0.79	1.32	2.23	-
Cr2O3	0.11	0.12	0.09	-
CuO	0.05	0.06	0.11	-
Fe2O3	2.91	5.07	9.90	3
K2O	1.47	1.90	2.60	0.79
MgO	2.54	2.60	3.01	0.66
MnO	0.07	0.15	0.16	0.10
Na2O	8.83	6.93	4.71	0.08
P2O5	6.71	9.19	9.89	0.10
PbO	0.03	0.02	0.02	-
SiO2	50.56	40.96	26.03	19.9
SO3	0.63	1.03	1.8	2.67
SrO	0.17	0.14	0.09	-
TiO2	0.36	0.56	0.91	0.21
ZnO	0.15	0.23	0.41	-
ZrO2	0.05	0.04	0.02	-

and

Table 3. Physical properties of NFA, MSW, and cement.

Characteristics	NFA	MSW(4.75–0.6)	MSW(0.6–0.3)	MSW(0.3–0.15)
Bulk density (kg/m3)	1450	1008	903	780
Clay content (%)	2	-	-	-
Water absorption (%)	3.6	1.3	1.5	1.7
Ordinary Portland Cement
Soundness			1 mm
Specific Gravity			3.15
Normal Consistency			30%
Setting time
i. Initial			115 min
ii. Final			275 min

, respectively.

A high-rate poly-carboxylic acid–based super plasticizer (SP) was adopted to maintain the flow of the mix. Various dosages of SP were used to maintain the fluidity around 200 ± 20 mm, and the water-to-cement ratio was maintained at 0.33.

Table 4. Mix design.

Mix	Cement	Natural Sand	Water Content	w/c
	(kg/m3)
Control	730.00	1321.00	240.90	0.33

shows the mix design adopted in this study and

Table 5. Mix proportions (volumetric percentages).

Grain Size	Mix	Cement	Natural Sand	MSW	SP
		(% vol.)			% of Cement
	Control	100%	100%	0%	0.15
0.3–0.15 mm	FS1	100%	90%	10%	0.21
	FS2	100%	80%	20%	0.21
	FS3	100%	70%	30%	0.22
0.6–0.3 mm	MS1	100%	90%	10%	0.16
	MS2	100%	80%	20%	0.17
	MS3	100%	70%	30%	0.17
0.6–4.75 mm	CS1	100%	90%	10%	0.17
	CS2	100%	80%	20%	0.18
	CS3	100%	70%	30%	0.19

shows the different mix ratios adopted in this study.

2.2. Testing Methods

The slump test methods and evaluation standards are strictly implemented following the Chinese national standard GB/T 2419 [36]. The density of hardened mortar was calculated using the following formula:

$$\rho =\frac{m}{v}$$

(3)

where m is the specimen mass after 28 days of standard curing, and v is the volume of the test block (40 mm × 40 mm × 160 mm).

The compressive and flexural strength tests were carried out following the Chinese Standard (GB/T 17671-1999) [37]. The compressive strength and flexural strength of prisms are tested using the following Equations (4) and (5), respectively:

$$R_c=\frac{F_c}{A}$$

(4)

$$R_f=\frac{1.5F_{f}L}{b^3}$$

(5)

$R_c$—compressive strength, in megapascals (MPa); $F_c$—maximum load at failure, in Newtons (N); A—pressure area, the unit is square millimeter (mm²); $R_f$—flexural strength, in megapascals (MPa); $F_f$—the load applied to the middle of the prism when it is broken, the unit is Newton (N); L—the distance between the supporting cylinders, in millimeters (mm); B—the side length of the square section of the prism, in millimeters (mm).

To see the influence of the MSW on the environment, the leaching toxicity was performed following Chinese standards GB 5085 [38], GB 5086 [39], and GB/T 15555 [40]. The determination of the heavy metals such as copper (Cu), zinc (Zn), lead (Pb), and cadmium (Cd) was checked and evaluated at 28 days of curing age. It should be noted that in order to avoid leaching during the curing period, the samples were not cured under submerged water conditions. The samples were cured at room temperature and RH of 80%.

Additionally, to determine the influence of acidic environment on MSW-BA mortar. The expansion behavior of mortars incorporating MSW-BA was measured according to GB/T 50733-2011 [41]; prismatic specimens measuring 25 mm × 25 mm × 285 mm were cast and demolded after 24 h. The curing prisms shall then be taken out one by one, one at a time, the surface shall be dried with a cloth, and the base length (Lo) of the specimen shall be immediately tested with a length gauge at an ambient temperature of (20 ± 2) °C. Each test piece is repeated at least twice, and the average of the two readings whose difference is within the precision of the instrument is taken as the length measurement value (accurate to 0.02 mm), each time the measurement direction of each piece should be the same. The reading should end within (15 ± 5) s from the time of removal of the specimen to completion of drying, and the specimen after reading should be covered with a wet towel. After measuring the reference length of all specimens, the specimens were placed in a curing cylinder with a concentration of 1 mol/L sodium hydroxide solution and ensured that the specimen was fully immersed. The solution temperature should be maintained at (80 ± 2) °C. Up to 28 days apart, expansion measurements were recorded at intervals of 1, 3, 7, 14, 21, and 28 days. Additionally, to observe the influence of the alkali–silica reaction (ASR) on the mortars, the specimens (40 mm × 40 mm × 160 mm) were immersed in hot water upon demolding. After 24 h in a hot water bath, the samples were immersed in a 1 mol/L NaOH solution. The expansion readings were taken up to 28 days after immersion.

3. Results and Discussion

3.1. Hardened Density

The hardened density of the specimens was checked on the 28 days cured samples. The samples were dried and tested for the different mixes. The results of the hardened density of each mix are shown in Figure 2. It can be seen that with each size fraction, there has been variation in the increase and decrease in the mortar density. With the inclusion of the fine fraction of MSW-BA, there was an increase in mortar density with an increase in the replacement percentage. However, in the case of the medium fraction and coarse fraction, a different trend was observed. In the case of fine fractions, the highest density was observed in FS3 (15.0%). Whereas, in the case of the medium and coarse fraction, the highest density was observed in MS1 (16.7%) and CS1 (16.5%). This can be attributed to the tradeoff between the density, induced porosity, and the reaction of MSW with cement. The results of the control mix illustrate the lowest density among all the proportions.

3.2. Mechanical Properties

The compressive strength (Figure 3) and flexural strength (Figure 4) tests were carried out following the Chinese Standard (GB/T 17671-1999) [37], and the test blocks were tested for 14 days and 28 days after standard curing. Perform the bending strength test first and then the compressive strength test. From Figure 3, it can be seen that with the increase in the replacement rate of natural sand and the increase in the grain size, there is an increase and then a decrease in the compressive strength of mortar. Among fine fractions, an increase in the compressive strength of 89.35% and 86.02% was observed at 20% compared to control concrete at 14 and 28 days. However, with an increase in the grain size and the increase in the replacement percentage, a reduction of strength was observed, but regardless, it is higher than the control mix. Surprisingly, all the mixes showed remarkable performance at all replacement percentages. It should be noticed that with the increase in the size and the percentage, the compressive strength decreases, which can be attributed to the larger grain size that could not create a dense microstructure.

Similarly, the same increasing and then decreasing trend were observed in the flexural strength. The highest strength was observed in the mix with fine fractions. Compared with the control mix, the highest flexural strength was observed with 20% MSW-BA, which was 50% and 35.92% at 14 days and 28 days, respectively. At 28 days of curing age, while comparing the mix at each size fraction, the highest flexural strength was observed in FS2, MS2, and CS3. In the case of the fine and medium fraction, the 20% MSW-BA; coarse fraction at 30% MSW-BA provided the optimum results attributed to the tradeoff between the pozzolanic of MSW-BA grain size of MSW-BA used.

This suggests that the addition of the finer fraction is associated with improving the mechanical properties. This can be attributed to the two main reasons; (i) finer particles may contain a higher amount of pozzolanic material responsible for increasing the hydration compounds of the BA associates an improvement of dry-cast concrete during the early and late stages of curing. This recorded benefit may be attributed to two main reasons. First, BA seemingly contained components that lent cementitious and pozzolanic-like reactivity, thus promoting increased C-S-H generation and strength. Another can be to the finer particles’ filler effect, which leads to the higher compaction in the mortar mixes, hence providing a dense matrix leading to greater compressive strength.

3.3. Exposure to Sodium Hydroxide (NaOH) Solution

3.3.1. Expansion in Sodium Hydroxide (NaOH) Solution

The expansion of the prismatic bars is shown in Figure 5. A reduction in the length is observed in the drying shrinkage of the mix. The different variations can be attributed to the combined effect of the grain size, replacement ratio, and the internal curing of the materials. As the grain size and the percentage of the MSW-BA were increased, a shift from the shrinkage to expansion was detectable. The highest length change was observed in the mix with a 30% coarse size fraction of the MSW-BA.

3.3.2. Hardened Properties of Sodium Hydroxide (NaOH)-Exposed Samples

Figure 6 and Figure 7 illustrate the mechanical characteristics of mortars subjected to 1 mol/L NaOH. When mortars are exposed to NaOH for 28 days following a usual curing period of 28 days, the compressive and flexural strengths are reduced. The values in red show the decline in compressive and flexural strength compared to the 28 days of strength without exposure. Acidic environments erode calcium salts and structures within OPC, causing the mechanical qualities to deteriorate.

It was found that the compressive and flexural strength of the text block under the curing of the alkaline solution was lower than that of the standard solution. Among them, FS2 is the most obvious, and its flexural strength is 4.78 MPa, which is 38.48% lower than that of the mortar test block under aqueous solution curing; its compressive strength is 30.28 MPa, which is 45.72% lower. CS1 has the least influence on the compressive strength, with a decrease of 5.79%; in the flexural strength, the least influence is FS3, with a decrease of 0.82%. It can be seen that the alkaline solution will affect the chemical bonds in the test block, resulting in a decrease in its mechanical properties.

Under the curing of strong alkaline solution, substances without gelling ability, such as aluminum hydroxide, generate easily soluble sodium aluminate and ammonia, thus increasing the porosity inside the cement mortar, thus causing the alkaline erosion solution medium to enter its interior. Hydration in a cement pore solution creates an alkaline reserve that is naturally buffered by the cement’s portlandite (calcium hydroxide) and CSH (calcium silicate hydrate) gels. When bottom ash is placed in an alkaline solution, one process dominates all others in evaluating its suitability for use in concrete, and that is the hydrolysis reaction associated with metallic aluminum (and similarly, though much less commonly, with zinc) [42].

3.4. Toxicity Characteristic Leaching Procedure Analysis

To assess the leaching of the heavy chemical in mortars, a toxicity characteristic leaching procedure (TCLP) was performed. The experiment uses a direct inhalation flame atomic absorption method to determine the content of copper, zinc, lead, and cadmium in the solid waste leachate. The concentration of the heavy metals is shown in

Table 6. Leaching concentration of heavy metals under different substitution rates.

	MSW	FS1	FS2	FS3	MS1	MS2	MS3	CS1	CS2	CS3	Limitation
Cu	584.6	ND	ND	ND	ND	0.001	ND	ND	ND	ND	50
Zn	150	0.007	0.012	0.012	0.015	0.015	0.020	0.020	0.021	0.023	50
Pb	107.1	0.048	0.048	0.048	ND	ND	ND	ND	ND	ND	3
Cd	1.5	ND	ND	ND	ND	ND	ND	ND	ND	ND	1

NOTE: Limitations as per Chinese Standard GB 5085.3-2007, ND: none detected.

.

The study found that FS does not contain Cu and Cd metals, and the Zn concentration increases with the increase of the substitution rate. When the substitution rate reaches 30%, the maximum concentration reaches 0.015 µg/mL; the Pb concentration remains unchanged at 0.048 µg/mL. No Cu, Pb, and Cd metals are found in MS. Similar to FS, Zn concentration increases with the increase of the substitution rate. When the substitution rate reaches 30%, the maximum concentration reaches 0.020 µg/mL. Experimental research analysis shows that the Cu concentration content is inversely proportional to the particle size, and its concentration increases with the decrease of the particle size. The maximum occurs when the particle size is less than 0.15, and its concentration is 5.849 µg/mL. Zn, Pb, and Cd metals are almost undetected when the particle size is 4.75–0.15. When the particle size is less than 0.15, the Zn concentration is 0.015 µg/mL, and the Pb concentration is 0.107 µg/mL.

4. Conclusions

The nine mixes were cast with three different grain sizes of MSW-BA and compared with the control mix. The international standards of methodology were adopted to assess the properties of the mortar. The tests conducted on the high-performance mortar include density, compressive strength, flexural strength, resistance to sodium hydroxide solution, and leaching characteristics. Following are the findings obtained from the current study.

The density of the mixes enhanced with inclusion of MSW-BA as replacement to the natural sand was measured. The maximum increase in the density for the high-performance mortar was noticed for the medium size grain, i.e., mix MS1 followed by coarse-fraction mix CS1 and fine-fraction mix FS3. Significant enhancement in the compressive strength of the mortar was exhibited for fine-grain-size MSW-BA followed by medium fraction and coarse fraction at both curing period. However, the difference in the flexural strength of the mixes between fine size and medium size of MSW-BA was smaller, whereas mixes incorporating coarse size of MSW-BA exhibited significantly greater strength difference at both 14 and 28 days. Moreover, prismatic bars subjected to the NaOH solution were found to have maximum expansion for the 30% substitution of coarse-fraction MSW-BA. The fine-size MSW-BA exhibited shrinkage in the mortar mixes, but with increase in the exposure period of NaOH solution, shrinkage reduced and shifted to negligible expansion. The mechanical characteristics in terms of compressive strength and flexural strength of mortar declined when kept in the NaOH solution. The leaching characteristics of the mortar mixes illustrate only tiny traces of lead but less than permissible limits.

The use of MSW-BA with natural sand is the focus of this research, which limits the further investigation of behavior of high-performance mortar under extreme conditions. Researchers must, however, analyze and forecast the behavior of MSW-BA and recycled sand based on the urgency of environmental policies. Furthermore, future environmental effect indicators such as the embodied CO₂ emission index, embodied energy consumption index, and embodied resource spending index should be assessed.