Investigation on Properties of Pervious Concrete Containing Co-Sintering Lightweight Aggregate from Dredged Sediment and Rice Husks

Abstract

The utilization of dredged sediment (DS) as a transformative material in building applications presents an ideal consumption strategy. This study endeavors to create a novel ceramsite lightweight aggregate (LWA) through the co-sintering of DS and rice husks (RHs), further integrating this LWA into the construction of pervious concrete. Results revealed that the optimum production procedure for the DS-based LWA incorporated a 21% RH addition, a sintering temperature of 1100 °C, and a sintering duration of 21 min. Notably, the optimal ceramsite LWA, denoted as SDC-H, exhibited a cylinder compressive strength of 28.02 MPa and an adsorption efficiency for Pb²⁺ of 94.33%. Comprehensive analysis (encompassing bulk density, cylinder compressive strength, water absorption, and the leaching concentrations of heavy metals) confirmed that SDC-H impacted the specification threshold of high-strength light aggregate derived from solid waste (T/CSTM 00548-2022). Substituting 50% of SDC-H led to a diminution in the mechanical properties but an improvement in the dynamic adsorption capacity of the innovative pervious concrete, registering a mechanical strength of 26.25 MPa and a cumulative adsorption capacity for Pb²⁺ of 285 mg/g. These performances of pervious concrete containing 50% SDC-H might correlate with the evolution of an interconnected and open-pore structure.

1. Introduction

Sediment accumulation in reservoirs, lakes, and rivers occurs over extended periods, becoming a crucial component of aquatic ecosystems [1]. As human activity intensifies, considerable amounts of pollutants, such as nutrient salt, toxic chemical, toxic strain, and heavy metal, access natural water and finally accumulate in sediment [2]. Consequently, sediments act as both sources and sinks for pollutants in natural water [3]. Ecological restoration of aquatic environments necessitates dredging [4], which generates substantial quantities of dredged sediment (DS) [5]. Given the high pollutant content in DS, its treatment or disposal requires stringent measures to avoid secondary pollution [6]. Traditional DS management strategies, such as solidification/stabilization, landfilling, and marine dumping [7], overlook the resource potential of DS, particularly its clay mineral content, treating it merely as solid waste [8]. Taking marine dumping as an example, over 324 million m³ DS will be disposed as solid waste using this method per year, according to the 2022 Bulletin of Marine Ecology and Environment Status of China [9]. Transforming DS into building materials, such as cement, bricks, and lightweight aggregates, offers a sustainable solution that underscores eco-friendliness, resource recycling, and cost-effectiveness [10]. The conversion of DS into sintering ceramsite is particularly promising, which could be explained as the decomposition of organic pollutants and the eradication of pathogenic microorganisms under high-temperature sintering conditions, coupled with the immobilization of heavy metals within DS [11], and the obtained product has numerous advantages including low density, high strength, strong corrosion resistance, excellent thermal insulation, etc., which make it widely using in the construction industry, water treatment, sound absorption field, and so on [12].

Considering the demand on the consumption side, ceramsite should be used as a lightweight aggregate (LWA) and substituted for aggregate in the concrete field [13]. Furthermore, constructing a building with ceramsite LWA can reduce the weight, improve the seismic resistance of the building, increase the safety and durability of the structure, and raise the contaminant purifying capacity [14]. Considering the chemical composition of DS (such as Al₂O₃, SiO₂, Fe₂O₃, CaO, MgO, Na₂O, and K₂O), several studies [15,16,17] have successfully transformed DS into ceramsite LWA using the sintering method. Although the feasibility of transforming from DS into ceramsite LWA had been confirmed, the performance characteristics of pure DS-based ceramsite are limited, such as inadequate strength or porosity [18]. Some researchers tried to use low-cost additives (e.g., agricultural wastes) to enhance the performance characteristics of DS or similar sludge-based ceramsite LWA. For example, Wei et al. [19] reported that oyster shell was conducive to the density decrease in ceramsite from steel fly ash and harbor sediment. Zhao et al. [20] introduced blue-green algae to modify the engineering characteristics of ceramsite LWA from sediment. Chen et al. [21] found that co-combustion ash of sewage sludge and rice husk (RH) was suitable for the preparation of ceramsite for the purpose of Pb²⁺ removal. RH, as a kind of typical biomass, has numerous advantages, including large quantity, wide range, low price, and being rich amorphous SiO₂ (providing excellent adsorption potential) [22]; it has been successfully applied to develop a novel ceramsite in our previous study [23]. Although the feasibility of co-sintering DS and RH to synthesize ceramsite had been confirmed, the consumption pathway to this kind of ceramsite is confining. Considering the huge yields of DS and RH [24,25], the transformation from these two solid wastes into architectural LWA might be more promising.

Pervious concrete was widely used in the construction of Sponge City to manage and purify the runoff water [26,27,28]. Conventional pervious concrete has multiple merits including high acoustic resistance, low thermal conductivity, and quick dewatering capacity [29]. Due to high porosity characters, pervious concrete has a certain purification capacity relative to runoff water [28]. In order to further improve the purifying capacity of pervious concrete relative to runoff water, some studies tried to modify and functionalize pervious concrete, including improving cementing material, surface modification, and the replacement of aggregates [30]. For example, Ahmadi et al. [31] found that the introduction of activated carbon and mineral zeolite in cementing material contributed to the improvement of removal ability to heavy metals for pervious concrete. Zhang et al. [32] coated the pervious concrete with nano-TiO₂ to increase its purifying capacity relative to COD, phosphorus, and nitrogen. Quan et al. [33] developed a novel pervious concrete by replacing gravel with alkali-activated aggregate, which showed a high phosphorus adsorption capacity. Aggregate in pervious concrete played a more important role on pollutant removal, especially for heavy metals [34]. On the other hand, Pb²⁺ can be considered as one of the major sources of pollution in runoff water [35], which might pose a threat to living species and biological systems [36]. Based on our previous research [23], we identified the ability of ceramsite lightweight aggregate (LWA) produced via co-sintering of dredged sediment (DS) and rice husks (RHs) to adsorb Pb²⁺. Consequently, implementing this novel ceramsite LWA in the construction of pervious concrete presents an optimal solution to manage Pb²⁺ in runoff water. This approach not only leverages the potential of DS but also caters to the demand for high-quality LWA in pervious concrete. However, to the best of our knowledge, no studies have reported on the feasibility of using ceramsite LWA produced through co-sintering of DS and RH in novel pervious concrete, especially considering its Pb²⁺ removal capacity.

In this study, (1) the co-sintering routing of ceramsite LWA from DS and RH mixture was optimized via the response surface methodology (RSM) method, (2) the basic and environmental performances of the optimal LWA were characterized, and (3) the mechanical property and dynamic adsorption of pervious concrete preparations from co-sintering LWA of DS and RH were evaluated.

2. Materials and Methods

2.1. Material

Dredged sediment (DS) and rice husks (RHs) were sourced from Wuhan, Hubei, China and subsequently dried prior to utilization. DS was dried at 105 °C for 72 h, while RH was dried at 105 °C for 24 h. All dried raw materials were ground in a ball mill (XQM-4 L) and then passed through a 200-mesh sieve.

Table 1. Typical characteristics of raw materials (wt.%).

		DS	RH
Proximate analysis	Ash	88.21	14.17
	Volatile Matter	7.91	71.41
	Fixed carbon	3.88	14.42
Ultimate analysis	C	3.04	41.68
	H	1.31	5.76
	O	5.68	37.68
	N	1.76	0.71
Ash analysis	Al2O3	17.33	1.32
	SiO2	60.78	86.94
	Fe2O3	3.02	2.24
	Na2O	4.71	0.12
	K2O	2.31	3.62
	CaO	5.02	1.55
	P2O5	0.78	0.28
	MgO	1.22	0.93
Trace element leaching analysis	Cd	0.21	N.d.
	Cd	0.58	0.044
	Cr	0.52	0.005
	Cu	1.01	0.044
	Zn	1.44	1.074

summarizes the proximate, ultimate, ash, and trace element leaching analysis of DS and RH. DS could be regarded as low organic matter and high ash content, and its main ash compositions were SiO₂ (63.78%) and Al₂O₃ (17.33%). The abundant SiO₂ and Al₂O₃ in DS could create sturdy, skeleton-structure ceramics [37]. Moreover, the sum content of (K₂O + Na₂O + CaO + MgO) in DS reached 11.26%, which had an excellent fluxing role. According to the integrated wastewater discharge standard (GB 3838-2002) [38] and the leaching concentrations of Cu and Cd from DS, DS was considered a high environmental risk, while the environmental risk of RH was negligible.

2.2. RSM Design

According to the Riley triangle theory [39], DS mixtures with 0–40% RH (internal reference method) fall into the sintering range of ceramic, where SiO₂, Al₂O₃, and (CaO + MgO + Fe₂O₃ + Na₂O + K₂O) are located at 53–79%, 10–25%, and 13–26%, respectively. To determine the sintering temperature and time, pure DS was sintered into ceramsite serials under different sintering temperatures (1000 °C, 1050 °C, 1100 °C, 1150 °C, and 1200 °C) and time (5 min, 10 min, 20 min, 30 min, and 40 min). The morphologies of the resulting DS-based lightweight aggregate (LWA) series are depicted in Figure 1. As demonstrated in the figure, sintering at low temperatures (<1050 °C) and for brief periods (<10 min) resulted in defective ceramics, while excessively high temperatures (>1150 °C) and prolonged durations (>30 min) led to overburning.

The detailed preparation process of LWA is shown in Figure S2. The experimental design was conducted using Design Expert 8.0.6.1. A three-factor, three-level Box–Behnken model was selected to optimize the process parameters, including RH dose (%), sintering temperature (°C), and sintering time (min). All variables (X₁, X_2, and X₃) contained three levels (−1, 0, +1) and are presented in Table S1. In order to obtain a novel LWA with superhigh mechanical strength and removal capacity relative to pollutants, the cylinder compressive strength (Y₁) and Pb²⁺ adsorption capacity (Y₂) were selected as responses. The detailed cylinder compressive strength was obtained as follow: serial LWA with a diameter of 5–8 mm was placed in a cylinder (5 L) and pressed with 300–500 N/s loads. The pressure was recorded when the punch was pressed to a depth of 20 mm, and then the cylinder compressive strength was calculated based on Equation (1):

$$\mathrm{Cylinder} \mathrm{compressive} \mathrm{strength}={\displaystyle \frac{{\mathrm{p}}_1+{\mathrm{p}}_2}{\mathrm{F}}}$$

(1)

where P₁ and P₂ are the pressure value (N) at 20 mm pressing depth and stamping mass (N); F is the pressure bearing area (10,000 mm²).

The detailed adsorption process was set as follow: the ceramsite LWA dosage was 2 g/L, the initial concentration of Pb²⁺ was 20 mg/L, the equilibrium time was 1440 min, and the temperature was 298 K. All solutions were filtered with a 0.22 μm filter and analyzed by inductively coupled plasma atomic emission spectrometry (ICP-AES) (Optima 4300DV, USA). The Pb²⁺ adsorption capacity was calculated using Equation (2):

$$\mathrm{Adsorption} \mathrm{efficiency} (\%)={\displaystyle \frac{\left({\mathrm{C}}_{\mathrm{e}} - {\mathrm{C}}_0\right)}{{\mathrm{C}}_0}}$$

(2)

where C_e and C₀ are the equilibrium and initial concentrations of Pb²⁺ (mg/L).

Three parallel groups were set for each experiment, and the average values was taken as the testing data. All measurement deviations were controlled within 5%. Testing data were calculated by the analysis of variance (ANOVA) and regression analysis, and the quadratic equation is as shown in Equation (3):

$${\mathrm{Y}}_{\mathrm{i}}={\mathsf{\beta }}_0+\sum {\mathsf{\beta }}_{\mathrm{i}}{\mathrm{X}}_{\mathrm{i}}+\sum {\mathsf{\beta }}_{\mathrm{ii}}{{\mathrm{X}}_{\mathrm{i}}}^2+\sum \sum {\mathsf{\beta }}_{\mathrm{ij}}{\mathrm{X}}_{\mathrm{i}}{\mathrm{X}}_{\mathrm{j}}$$

(3)

where Y_i (i = 1 and 2) is the predicted response; X_i and X_j (i = 1, 2, 3 and j = 1, 2, 3) are the coded values of independent variables; and β₀, β_i, β_ii, and β_ij (i = 1, 2, 3 and j = 1, 2, 3) are the ijth model regression coefficient parameters.

2.3. Characterization of LWA

Typical properties of optimal LWA, including bulk density, apparent density, cylinder compressive strength, and water absorption, were evaluated based on light aggregate with high strength prepared from solid waste (T/CSTM 00548-2022) [40]. Water absorption was measured by immersing a certain amount of LWA in tap water, taking it out after 24 h, and calculating mass difference. Moreover, the leaching concentrations of HMs from optimal LWA product via the TCLP method were tested by ICP-AES and the corresponding leaching behavior was evaluated based on light aggregate with high strength prepared from solid waste (T/CSTM 00548-2022).

2.4. Preparation of Pervious Concrete

Ordinary Portland cement (P.O 42.5) was purchased from Huaxin Cement Co., Ltd., Wuhan, Hubei, China. Natural basalt (blank group) and optimal ceramic LWA with a particle size distribution ranging from 5 to 10 mm were used as the aggregate. White powdered polycarboxylic acid was utilized as the water reducing agent. The pervious concrete samples were prepared from blank/optimal ceramic LWA and cement with a 0.30 water/solid mass fraction. The mixtures were homogeneously mixed and injected into a steel mold (40 mm × 40 mm × 40 mm). Subsequently, the mixtures were cured for 1 d under room temperature, and then demountable samples were cured at (20 ± 1 °C) for 27 d at 95% humidity. The proportions of ceramic LWA replacing basalt in pervious concrete samples were 0%, 25%, 50%, 75%, and 100%, whose proportion and morphology are presented in Table S2 and Figure 2.

2.5. Characteristics of Pervious Concrete

2.5.1. Compressive Strength of Pervious Concrete

The mechanical strength of pervious concrete after 28 d curing was tested based on the standard for testing concrete physical and mechanical properties (GB/T50081-2019) [41]. The compressive strength of pervious concrete was calculated by Equation (4):

$${\mathrm{f}}_{\mathrm{c}}={\displaystyle \frac{\mathrm{F}}{\mathrm{A}}}$$

(4)

where f_c is the compressive strength, MPa; F is the ultimate load of concrete, N; and A is the compression surface area, mm².

2.5.2. Dynamic Adsorption of Pervious Concrete

A dynamic adsorption system (Figure S3) was designed to simulate a rainfall environment for studying the Pb²⁺ removal efficiency of pervious concrete from overland runoff. The dynamic adsorption process is as follows: (1) Four-sided sealed pervious concrete (except top and bottom) was put into the device. (2) The simulated rainfall (Pb²⁺ concentration = 30 mg/L) passed through the pervious concrete at a flow rate of 1 mL/min. When all solutions passed through the specimen, solutions were collected at different time nodes (60 min–1020 min). (3) Solutions filtering through a 0.45 mm membrane filter were tested by using ICP-AES. The removal rate and cumulative adsorption capacity (Q_T) were calculated using Equations (5) and (6):

$$\mathrm{Removal} \mathrm{rate}=\left({\mathrm{C}}_0 - {\mathrm{C}}_{\mathrm{T}}\right)/{\mathrm{C}}_0;$$

(5)

$${\mathrm{Q}}_{\mathrm{T}}=\left({\mathrm{C}}_0 - {\mathrm{C}}_{\mathrm{T}}\right)\times \mathrm{V}$$

(6)

where C_T represents the concentration of Pb²⁺ at T moment, mg/L; C_T represents the initial concentration of Pb²⁺ (C_T = 30 mg/L); and V represents the total volume of the simulated solution (V = 15 L).

3. Results and Discussion

3.1. RSM Analysis

The three-dimensional (3D) response surface illustrating the impact of process parameters on the cylinder compressive strength and adsorption capacity for Pb²⁺ is depicted in Figure 3. Figure 3a–c reveals that the cylinder compressive strength of ceramic LWA increased at first and then decreased with RH dose/sintering temperature/sintering time increasing. These observations suggest the following: (1) For RH dose, RH ash consisted of amorphous SiO₂ [42] and certain amorphous (active) SiO₂ could participate in the construction of the skeleton structure of LWA, which promoted the strength growth of ceramic LWA. When the RH dose exceeded the limiting value, excessive organic content from RH caused the instability of ceramsite LWA. (2) For sintering temperature/time, the liquid phase was a function of sintering temperature/time [43] and overmuch or excessively low liquid-phase content was not conducive to the stability of the skeleton structure of ceramsite LWA. Similar to cylinder compressive strength, the Pb²⁺ adsorption capacity of ceramsite LWA also increased at first and then decreased with RH dose/sintering temperature/sintering time increasing (Figure 3d–f). This trend could be attributed to the following: (1) RH was a potential raw material (within a certain range) used to synthesize ceramsite LWA due to its active/amorphous SiO₂ component [44], but superabundant organic matter from the excess RH dose facilitated the formation of open pores, which are harmful to adsorption [45]. (2) The pore structure of ceramsite LWA was also a function of sintering temperature/time. Thus, sufficient sintering temperature and time were the preconditions of the formation of well-constructed pore structure for adsorption [12], while exorbitant sintering temperature and time caused the formation of excess liquid phase, which would block the mesopores (adsorption sites) [46].

ANOVA and regression analysis are used to optimize the preparation technology to obtain an optimized ceramsite LWA with maximal cylinder compressive strength and Pb²⁺ adsorption capacity, as shown in Tables S3 and S4, respectively. The values of “Prob > F” for the two models were less than 0.001 and their coefficients of R² (0.9988 and 0.9892) were close to 1.0, indicating that the obtained models were reliable. The regression model equations for cylinder compressive strength and Pb²⁺ adsorption capacity are presented as follows.

$${\mathrm{Y}}_1=27.41-1.72{\mathrm{X}}_1+2.4{\mathrm{X}}_2+2.2{\mathrm{X}}_3-0.35{\mathrm{X}}_1{\mathrm{X}}_2+0.67{\mathrm{X}}_1{\mathrm{X}}_3-0.06{\mathrm{X}}_2{\mathrm{X}}_3-6.16{{\mathrm{X}}_1}^2-6.42{{\mathrm{X}}_2}^2-3.28{{\mathrm{X}}_3}^2$$

(7)

$${\mathrm{Y}}_2=94.12+8.60{\mathrm{X}}_1-7.76{\mathrm{X}}_2-0.49{\mathrm{X}}_3-1.03{\mathrm{X}}_1{\mathrm{X}}_2+4.60{\mathrm{X}}_1{\mathrm{X}}_3-7.23{\mathrm{X}}_2{\mathrm{X}}_3-17.69{{\mathrm{X}}_1}^2-23.84{{\mathrm{X}}_2}^2-21.50{{\mathrm{X}}_3}^2$$

(8)

To obtain a ceramsite LWA with maximal cylinder compressive strength, 17% RH + 83% DS mixture was sintered at 1109 °C for 23 min, whose predicted cylinder compressive strength was 28.10 MPa. To obtain a ceramsite LWA with maximal Pb²⁺ adsorption capacity, a mixture of 25% RH + 75% DS was sintered at 1092 °C for 23 min, whose predicted Pb²⁺ adsorption capacity was as high as 95.27%.

3.2. Process Optimization and Characterization of LWA

The predicted cylinder compressive strength and Pb²⁺ adsorption capacity values and the quadratic optimized technological parameters were obtained via Design-Expert software and are shown in

Table 2. Prediction value and optimized condition for the preparation of ceramite LWA.

Items		Optimized Direction	Parameters		Predicted Value
			Min	Max	Optimum
Level	X1 (%)	Set value	0	50	21
	X2 (°C)	Set value	1050	1150	1100
	X3 (min)	Set value	10	30	21
Response values	Y1 (MPa)	Max	11.19	40	27.57
	Y2 (%)	Max	31.06	100	94.00

. The optimal ceramsite LWA (SDC-H) was the sintered product of 21%RH + 79%DS mixture at 1100 °C for 21 min and its measured cylinder compressive strength and Pb²⁺ adsorption capacity were 28.02 MPa and 94.33%, which had 1.63% and 0.35% deviation compared to predictive values, respectively.

Table 3. Characterization of SDC-H ceramsite LWA.

Indexes	SDC-H	Limit Value a
Bulk density (kg/m3)	1182	≤1200
Cylinder compressive strength (MPa)	27.63	≥12.5
Water absorption (%)	7.6	≤10
Softening coefficient	0.87	≥0.8
Sturdiness (%)	3.15	≤8
Pb (mg/L)	N.d.	<0.3
Cd (mg/L)	N.d.	<0.03
Cr (mg/L)	0.027	<0.2
Cu (mg/L)	0.094	<1.0
Zn (mg/L)	0.022	<1.0

^a Light aggregate with high strength prepared from solid waste, T/CSTM 00548-2022, China.

summarizes the basic performances of SDC-H. The key parameters of SDC-H, including bulk density, cylinder compressive strength, and water absorption, emerged as a superior level, whose values reached 1182 kg/m³, 27.63 MPa, and 7.6%, respectively. All key parameters of SDC-H met the specification threshold of light aggregate with high strength prepared from solid waste (T/CSTM 00548-2022). Moreover, the softening coefficient and sturdiness of SDC-H also met the specification threshold. Leaching concentrations of HMs from SDC-H were almost negligible compared to the leaching behavior of raw materials and the specification threshold (Table 1 and Table 3), indicating that high-temperature (1100 °C) sintering ceramsite encapsulated HMs in the crystal structure or vitrification of ceramsite LWA [47]. Namely, SDC-H was eco-friendly based on its HMs leaching behavior. Overall, the basic performances of the optimal ceramsite (SDC-H) were in conformity with the specification and could be used as aggregate to prepare pervious concrete.

3.3. Performances of Pervious Concrete

3.3.1. Mechanical Property of Pervious Concrete

Figure 4 shows the mechanical properties of pervious concrete serials with different SDC-H doses. The compressive strength of pervious concrete without SDC-H reached as high as 34.23 MPa. With SDC-H replacement, the compressive strength of pervious concrete reduced obviously. This decline could be attributed to the inherent characteristics of SDC-H, which exhibited significantly higher porosity and lower strength compared to basalt aggregate [48]. Under 25–50% replacement rates of SDC-H, the attenuation rates of compressive strength of pervious concrete were relatively flat, whose values were 13.12% and 11.74%, respectively. Specifically, the compressive strength of pervious concrete with a 50% replacement rate of SDC-H (labeled as Ce-50) dropped to 26.25 MPa. When the replacement rate exceeded 50%, a sharp drop in pervious concrete could be observed, whose falling ranges exceeded 20%. This significant reduction in compressive strength beyond a 50% substitution rate may be closely linked to alterations in the pore structure of the pervious concrete, particularly in Ce-50, indicating a critical limit to the proportion of SDC-H exists.

Figure 5 presents a three-dimensional diagram of the pore distribution of Ce-50 by Micro-CT. The figure vividly captures a network of interconnected and open pores that are prevalent throughout the Ce-50 sample. The presence of such a significant number of open and interconnected pores inherently weakened the structural integrity of the Ce-50 sample, making it more susceptible to mechanical failure under load. Previous research [49,50] has underscored the impact of artificial aggregate replacement on the pore structure of pervious concrete and, by extension, its mechanical properties.

3.3.2. Removal Capacity to Pb of Pervious Concrete

Figure 6 provides a detailed overview of the performance of different pervious concrete samples—labeled as Ce-0, Ce-25, Ce-50, Ce-75, and Ce-100—in terms of the Pb²⁺ removal rates and Q_T of pervious concrete over time. As shown in the figure, the Pb²⁺ removal rates of serial pervious concretes gradually increased and then reached a stable equilibrium with prolonged adsorption time. Note that Ce-0 without SDC-H substitution had a limited Pb²⁺ removal rate, whose maximal removal rate and equilibrium time were about 20% and 420 min. The relatively low removal rate and quick equilibrium time of Ce-0 might be related to the dense structure of basalt and limited Pb²⁺ removal ability itself. With ceramite LWA substitution, the maximal Pb²⁺ removal rate of pervious concrete gradually increased and its corresponding equilibrium time was delayed. The maximal Pb²⁺ removal rate occurred during the adsorption process of the Ce-100 sample, whose removal rate value was as high as 85.97%. Namely, the application of artificial aggregate (SDC-H) with excellent Pb²⁺ adsorption capacity in pervious concrete could improve its Pb²⁺ adsorption capacity sharply. Considering the Q_T of pervious concrete serials (Figure 6), Q_T values increased with the replacement rate of ceramite LWA, but the growth rates of Q_T gradually became slow, from 104.65% to 17.12%. Focusing on the adsorption initial stage, the continuing increase in the replacement rate of SDC-H (>50%) had little effect on the adsorption behavior of pervious concrete serials. Namely, Ce-50 was seen as the optimal solution considering its removal efficiency (Q_T = 285 mg/g). The occurrence of extremum could be explained as the interception and adsorption of the interconnected and open pore structure inside the concrete itself and its ceramite LWA [51]. Per Section 3.3.1, Ce-50 could be further confirmed as the ideal pervious concrete, which had excellent mechanical strength and Pb²⁺ purification capacity, simultaneously.

4. Conclusions

A novel ceramsite LWA (SDC-H) for the construction of a new kind of pervious concrete was synthesized by co-sintering 79% DS and 21% RH at 1100 °C for 21 min. All key parameters of SDC-H, including bulk density, cylinder compressive strength and water absorption, and leaching concentrations of heavy metals, met the specification threshold of light aggregate with high strength prepared from solid waste (T/CSTM 00548–2022). Among the cylinder compressive strength and Pb²⁺ adsorption capacity were 28.02 MPa and 94.33%, respectively. A novel pervious concrete (Ce-50) containing a 50% SDC-H substitution rate for natural aggregate was obtained, which had a certain mechanical strength (26.25 MPa) and outstanding cumulative Pb²⁺ adsorption capacity (285 mg/g). Note that the replacement SDC-H in the pervious concrete deteriorated its compressive strength but improve its dynamic adsorption capacity observably. Under the 50% SDC-H substitution rate condition, a reasonable pore structure formed in the optimal novel pervious concrete, which had abundant interconnected and open pores and gave it excellent performances. However, the continued effectiveness and durability of the novel pervious concrete under environmental changes should be taken into consideration before practical implementation.