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Review

The Utilization of Recycled Sewage Sludge Ash as a Supplementary Cementitious Material in Mortar: A Review

by
Chaofeng Liang
1,
Xinqian Le
1,
Weijiong Fang
2,
Jianming Zhao
3,
Liuji Fang
1,* and
Shaodan Hou
1,*
1
School of Civil Engineering, Shaoxing University, Shaoxing 312010, China
2
Shaoxing City Investment Group Co., Ltd., Shaoxing 312000, China
3
Shaoxing City Investment Recycled Resources Co., Ltd., Shaoxing 312000, China
*
Authors to whom correspondence should be addressed.
Sustainability 2022, 14(8), 4432; https://doi.org/10.3390/su14084432
Submission received: 17 March 2022 / Revised: 31 March 2022 / Accepted: 1 April 2022 / Published: 8 April 2022
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Abstract

:
The output of sewage sludge has been increasing in recent years in China. Traditional treatment methods, such as incineration and landfilling, cannot meet the requirement of sustainability in various industries. As one of the efficient recycling methods for sewage sludge, previous studies have proven that sewage sludge ash (SSA) can be used as a supplementary cementitious material to partly replace cement in mortar or concrete. To understand the performance of SSA comprehensively, which contributes to its better utilization, this study reviews the basic properties of SSA and the effect of SSA on the performance of mortar. Firstly, the basic properties of SSA, such as chemical composition, heavy metal content, activity, and microstructure, are investigated. Then, the effects of SSA on the workability, setting time, and mechanical properties of mortar are reviewed. The results show that the particle size distribution of SSA is in the range of 2.5–250 μm. SSA contains active oxides such as SiO2, Al2O3, Fe2O3, and CaO, which are similar to fly ash, indicating that SSA has potential pozzolanic properties. The leaching concentration of SSA is much lower than the required values in the relevant specifications, leading to an allowable environment influence. The incorporation of SSA has a negative impact on the workability, setting time, water absorption, compressive strength, and flexural strength of the mortar. The 90-day compressive strength of the SSA mortar is 71.72–98.6% of the cement mortar, when the replacement ratio of SSA is in the range of 10–30%. However, performance can be improved by increasing the grinding time or adding an admixture. The drying shrinkage and capillary water absorption of SSA mortar are higher than those of normal mortar, which is mainly related to an increase of porosity. In conclusion, it is proven that SSA can be used to partly replace cement in mortar with appropriate properties. Source and production process have a great influence on the basic properties of SSA, leading to varied, even opposite, effects on the mechanical properties and durability of mortar. In the future, the selected raw materials and a standard preparation method should be proposed for promoting the application of SSA.

1. Introduction

Sewage sludge, an inevitable byproduct of the sewage treatment process of sewage treatment plants, is a complex heterogeneous mixture. Its composition and properties depend on the source of the sewage and the chemical substances added in the process of sewage purification and storage [1]. With the acceleration of urbanization and the improvement of people’s living standards, the number of sewage treatment plants in urban and rural areas in China increased from 1445 to 4326 during 2008–2020, according to the statistics of the Ministry of Housing and Urban-Rural Development of China [2]. At the same time, annual sewage discharge increased from 42.729 billion m3 to 64.76 billion m3 (as shown in Figure 1). These phenomena bring new challenges to the reduction, neutralization, and recycling of sewage sludge.
The traditional treatments for sewage sludge include landfilling and incineration [3,4], which can solve the problems of increasing sewage sludge but lead to an environmental burden. In terms of landfilling, the pH values of sewage sludge produced from most sewage treatment plants in China are within the range of 6–9 [4], which meets the pH limit of 5.5–8.5 in Chinese standard GB 4284–2018, “Agricultural Sludge Pollutant Control Standard”. However, the wastewater from a sewage treatment plant is acid- or alkali-producing industrial wastewater, which results in lower or higher pH values of sewage sludge compared to the limited pH values above. In addition, heavy metals, pathogens and parasite eggs in sewage sludge easily threaten human health through the food chain after landfilling. On the other hand, a shortage of land resources has become a serious problem around the world. The proportion of sanitary landfills in the UK changed from 27% in 1980 to 6% in 2005 [5]. France has banned landfilling as a sewage sludge treatment [3]. In China, only dewatered sludge can be confined to a landfill [6]. As for the incineration process, the water content of sewage sludge is reduced to 25–30% with incineration temperatures of 800–900℃ [7,8]. Incineration is a relatively mature technology for the harmless disposal of municipal sewage sludge, and organic matter is carbonized and bacterial and viral microorganisms are mostly killed during the incineration process [9]. However, it faces problems of significant CO2 emissions and high costs. In addition to disposal, sewage sludge can be used to produce sewage sludge derived biochar, due to its excellent adsorptive characteristics, contributing to the removal of various pollutants from industrial wastewater, such as phenolic compounds and pharmaceuticals [10,11]. However, the utilization of sewage sludge with this method is not common at present. Therefore, it is necessary to seek new resource utilization methods for sewage sludge.
On the other hand, concrete is the most widely used building material in the world. As the cementitious material in concrete, cement has been widely used in civil construction, national defense and water conservancy projects, which have made a great contribution to the development of the construction industry. However, CO2 emissions during the production and utilization of cement account for approximately 5–8% of the global total CO2 emissions [12]. According to the Research Report on the Analysis and Investment Prospect of China Cement Products Market in 2019–2025, China’s cement output in the first half of 2019 reached 1044.691 million tons, with a cumulative increase of 6.8%, which causes a prominent problem for the mining resource consumption and ecological destruction of cement enterprises. Within this context, supplementary cementitious materials (SCM), such as fly ash and granulated blast furnace slag, are studied and used to partly replace cement [13]. However, the traditional SCMs are facing the problem of a resource shortage in China, nowadays.
Previous studies [14,15,16,17,18] found that sewage sludge ash (SSA) from sewage sludge has certain activity, in that it can be applied in mortar to partly replace cement. SSA can be used as a filler or SCM to partly replace cement, which can resolve the problem of increasing number of sewage sludge. On the other hand, the production process of cement results in a large CO2 emission, which causes global warming. The utilization of SSA can reduce the demand for cement, contributing to sustainable production of mortar. In addition, the use of SSA has potential for immobilizing heavy metals in the matrix of hydrated phases, thereby reducing the emission of heavy metals to the environment [19]. The authors searched the literatures from 2008 to 2020 using the keywords “SSA”, “cementitious materials” and “mineral admixtures” in Web of Science. The result is shown in Figure 2, in which the red region represents the hot content. The values in Figure 2 represent the occurrence probability for different keywords in the literatures, and the higher the value is, the higher the occurrence probability is. It can be determined that the application of SSA in cement-based materials is the focus of the researchers’ attention. Smol et al. [20] studied the possible use of SSA in the construction industry from the aspect of a circular economy. They reviewed the potential application of SSA in cement, brick, ceramic and glass production. Swierczek et al. [21] reviewed the potential application of SSA in cement-based materials as a binder or aggregate. However, the effects of SSA on the properties of cement-based materials have no common regular due to the different sources and production process of SSA. There have been few literatures reviewing the comprehensive basic properties of SSA and its effect on the properties of mortar at the same time. Therefore, in this study, the basic characteristics of SSA after drying, incineration, grinding and other treatments are studied in details. Then, the influences of SSA as a SCM on the performance of mortar are investigated, aiming to provide reference for the resource utilization of SSA in mortar.

2. Basic Characteristics of SSA

2.1. Specific Gravity and Density

The specific gravity of SSA ranges from 2.33 to 3.51 [14,15,22], with an average of 2.76, which is lower than Portland cement (3.16) [22]. The density of SSA increases with the increase of incineration temperature and reaches its maximum at about 1000 °C. The grinding process can increase SSA density in a certain range. Nevertheless, the SSA density after incineration and grinding is still lower than that of Portland cement [16].

2.2. Particle Size Distribution

The particle size of SSA is mainly between silt (2.5–62.5 μm) and fine sand (62.5–250 μm) [8] (as shown in Figure 3), with a similar particle size distribution of cement and fly ash [15,16,17,18,23,24,25,26,27]. The particle size of cement is mainly concentrated between 10 and 70 μm, while SSA with an average diameter of about 26 μm has larger particles in the range of 70–100 μm [7]. The finer particles with good gradation can lead to the micro filling effect of SSA, which contributes to a denser microstructure.

2.3. Chemical Composition

The mineral compositions of SSA are quartz, hematite, magnetite, albite, anorthite, mullite, calcite, and feldspar [14,17,19,23,29,30,31,32]. In terms of oxides, the main contents in SSA are SiO2, Al2O3, Fe2O3, and CaO. In addition, SSA contains Na2O, MgO, P2O5, K2O, SO3, and P2O5 [16,18,33,34,35,36,37,38]. Compared the oxide composition (mass ratio) of SSA with fly ash and cement, it is found that the oxide composition of SSA is similar to that of fly ash. However, the proportion of oxides in SSA has great discreteness. The content of CaO in SSA is much lower than cement, which is the main reason for the low activity of SSA. However, SSA has more SiO2 and Al2O3 in content than cement (as shown in Figure 4). The amorphous SiO2 and Al2O3 in SSA can react with calcium hydroxide and form calcium silicate hydrate (C-S-H) and calcium aluminate hydrate (C-A-H), respectively, which can improve the strength of mortar. The incorporation of SSA increases the number of nucleation sites of C-S-H in mortar [39], which can fix the heavy metals in the hydration matrix [19,40]. In addition, the presence of Al2O3 contributes to the formation of calcium sulphoaluminate hydrate in cement-based materials, such as monosulfide calcium sulphoaluminate hydrate, which possesses obvious adsorption capacity of aboriginal chloride [41] and thus improves the chloride resistance of cement-based materials [8].
The content ternary diagrams of SiO2, Al2O3, and CaO for SSA are plotted in Figure 5 to further explore the feasibility of SSA as a SCM [14,16,18,29,33]. According to the reference, the latent hydraulic activity and pozzolanic activity can be evaluated by the contents of SiO2, Al2O3 and CaO [8]. Figure 5 shows the contents of SiO2, Al2O3, and CaO in traditional SCMs and cement. The results show that the average contents of SiO2, Al2O3 and CaO in SSA (with 10 samples) are 29.57%, 13.58% and 17.53%, in reference with the standard deviations of 11.47%, 2.43%, and 13.06%, respectively. The values of SSA samples are basically within the range of latent hydraulic activity and pozzolanic activity, such as fly ash, indicating the potential pozzolanic activity of SSA.

2.4. Heavy Metal Content

The total content of heavy metals in SSA is shown in Table 1. The Länder-Arbeitsgemeinschaft Abfall (LAGA) limits and Swiss regulations are used to evaluate the content of heavy metals. The results show that the average contents of heavy metals in SSA are lower than LAGA limits. The average contents of Zn and Cu are higher than Swiss regulations and the average contents of Cr, Pb and Cd are slightly higher than Swiss regulations. The total content of heavy metals in SSA has a high coefficient of variation of 51.54–227.17%, indicating that the total content of heavy metals in different SSA samples varies greatly, which is related to the source, treatment, and storage conditions of sewage sludge and preparation process of SSA.
Furthermore, the heavy metal elements, including Ba, Zn, Cu, Cr, Pb, Hg, As, Cd, and Ni, are selected for statistic analysis of the leaching concentration (Table 2) to investigate the influence of SSA on the environment, according to the Toxicity Characteristic Leaching Procedure (TCLP) limit from the United States Environmental Protection Agency and Chinese standard GB 5085.3-2007 “Identification standards for hazardous wastes-Identification for extraction toxicity”. The results show that the leaching concentration of heavy metals in SSA has a high coefficient of variation (96.19–278.37%). However, the leaching concentrations of SSAs are all lower than the corresponding limits in TCLP and GB 5085.3-2007.
The statistic results in Table 1 and Table 2 show that the leaching concentration of heavy metals in SSA is far lower than the relevant specifications although the content of some heavy metals in SSA is relatively high (Zn, Cu, Cr, Pb, Cd), which illustrates the potential for the safe application of SSA.

2.5. Appearance Morphology and Microstructure

Highly dehydrated sewage sludge heated at 200 °C for six hours contains many smooth crystals, which are considered as siliceous particles (Figure 6a) [85]. SSA has porous structure and irregular shape with rough surface (Figure 6b,c) [86]. The particles of SSA will be smoother and smaller with reduced pores after grinding [15], as shown in Figure 6d–f. However, the extension of grinding time has a limited effect on the reduction of SSA particles. When the grinding time is 360 min, SSA particles are compacted and agglomerated in ball mill [14] as shown in Figure 6g–i.
In addition, Wang et al. [87] found that SSA, obtained by drying at 105 °C and grinding with organic matter for 4 min in a ball mill, is black-brown in color and cannot be directly used as an admixture [26]. The existence of organic matter increases the water requirement of SSA, affects the formation of structure when mixing SSA with cement, and then reduces the strength of mortar. With the increase of incineration temperature, the color of SSA gradually changed from dark brown to light yellow, and this is due to the fact that the organic matter and carbon-containing particles in SSA were gradually removed under high temperature.

2.6. Pozzolanic Activity

Generally speaking, SCMs can be classified into self-gel material and pozzolanic material [88]. The reaction of self-gel material is similar to cement, which can be hardened with water. The pozzolanic material is defined in American Society of Testing Materials (ASTM) C125 as “a silicon and aluminum material that has little coagulation value, but in the presence of water, it can undergo chemical reaction with calcium hydroxide at room temperature to form a compound with coagulation properties” [89,90]. The Bureau of Indian Standards 1344 [91] and ASTM C618-17a [90] have the requirement on the total content of SiO2, Al2O3 and Fe2O3 in the range of 50–70% for pozzolanic materials. By the summary of the chemical compositions for SSA, it is found that most SSA from different literatures meet the requirement.
It is found that the fine ground SSA can be used as pozzolanic material in mortar due to its pozzolanic activity similar to fly ash [92]. The strength activity index value of SSA was between 53.6% and 74.3% due to the existence of amorphous silicon oxide [93]. The activity characteristic of pozzolanic material relies on its ability to react with Ca(OH)2 and generate hydration products [94]. It is found that SSA can react with Ca(OH)2 to produce a large number of hydration products, which can be defined as a pozzolanic material, showing the utilization potential as a SCM in mortar [95].
Donatello et al. [96] found that grinding SSA can improve the pozzolanic activity based on different test methods, including the strength activity index and Frattini tests. Pan et al. [14] found that there is an increasement ratio of 5% for strength activity index value when the specific surface area of SSA increases per 100 m2/kg. Besides, the calcination temperature has a significant effect on the pozzolanic activity of SSA. Basto et al. [97] found that the optimal calcination temperature for sewage sludge is 600 °C, after which the SSA has a higher loss in conductivity up to 88.3%, indicating the higher pozzolanic activity. The higher the calcination temperature is, the lower the pozzolanic activity will be.

3. Effect of SSA on the Performance of Mortar

3.1. Workability

The replacement ratio of SSA is a major factor influencing the workability of mortar [15,84,98,99]. Figure 7 shows the relative fluidity of mortar with the SSA replacement rate of 0–30% from different literatures. The results show that the fluidity of mortar decreases with the increase of SSA content. For every 5% increase on average in SSA content, the fluidity of mortar decreases by 4.07%. This is due to the porous properties and irregular morphology of SSA [34]. The porous microstructure increases the water absorption, and the irregular morphology can rearrange SSA particles in mortar and form a large number of gaps [66]. Besides, the particle size distribution of SSA has a significant influence on the workability of mortar [87]. The grinding makes the surface of SSA particles smoother [14,25,81,100,101], reduces the interlocking and friction between particles, and then improves the workability of mortar [26,102]. When the water to binder ratio of mortar is constant, the fluidity of mortar with SSA can be adjusted by adding an appropriate amount of superplasticizer.

3.2. Setting Time

The setting time of mortar increases with the addition of SSA [84,98,104,105]. With the increase of SSA, the content of phosphate in mortar rises. Then, the phosphate reacts with Ca(OH)2 and generates the insoluble calcium phosphate on the surface of cement particles, hindering the hydration of cement [104,105]. The Al2O3 in SSA hinders the formation of C-S-H gel and delays the hydration of cement [66]. Furthermore, the grinding process for SSA leads to the adsorption of more calcium ions on its surface, which affects the accumulation and nucleation of calcium concentration in mortar, resulting in a prolonged setting time [14].

3.3. Water Absorption and Water Requirement

The water absorption and water demand of mortar increase when SSA is applied. Firstly, the adsorption of water molecules on the surface of SSA particles reduces the content of free water in mortar due to the porous microstructure and irregular shape of SSA [18]. Secondly, the rough surface of SSA leads to the large relative sliding resistance between particles, which reduces the fluidity of mortar. Besides, the density of SSA is smaller than that of cement. Therefore, when cement is replaced with SSA by mass, the volume of binders increases and then the water requirement of mortar further increases [8].

3.4. Compressive Strength

Many researchers found that the compressive strength of mortar with SSA is lower than that of cement mortar [19,25,66,84,87,106,107], which can be explained by the low reactivity of SSA [108,109], high porosity, and irregular shape [110]. The low reactivity of SSA is caused by the low content of CaO and amorphous silica [14]. In addition, SO3 and carbohydrates contained in SSA, which decompose when the temperature exceeds 390 °C [19], delay the hydration of cement [16], thereby affecting the formation of hydration products of mortar.
The increase of incineration temperature has a dual effect on the pozzolanic activity of SSA. On the one hand, the raise of temperature increases the content of amorphous SiO2 in SSA, which promotes the formation of C-S-H gel in mortar, resulting in a positive effect on the performance of mortar. On the other hand, the sintering bonding phenomenon appears with the raise of temperature [87], which has a negative effect on the performance of mortar. The grinding process can improve the pozzolanic activity of SSA to some extent [14,15,17,32,111]. The compressive strength of mortar prepared by SSA with fine particles is higher than that of mortar prepared by coarse SSA at the same curing age. when the replacement ratio is 20%, the 7-day and 28-day compressive strengths of recycled mortar increase by 1.4 MPa and 1.9 MPa for every 100 m2/kg increase in SSA, respectively [14].
The 90-day compressive strength of recycled mortar is 71.72–98.6% of the 90-d compressive strength of cement mortar when the replacement ratio of SSA is 10–30% [17,84], which is higher than that of SSA mortar at 28-day age (63.24–95.45% of cement mortar), reflecting the long-term pozzolanic activity of SSA. The porous structure and high-water absorption contribute to the enhancement of long-term compressive strength, which can be explained by the internal curing of porous structure.
The replacement ratio of SSA is an important factor affecting the compressive strength of mortar. The higher the replacement ratio is, the lower the compressive strength of mortar is [16,19,66,84,106,112]. This is due to the fact that the active Ca2+ and Si2+ is reduced with the increasing replacement of SSA, leading to the decrease in the total content of active binder [15,19,98]. When CaO is added in the form of lime or cement to mortar with a water to binder ratio of 0.5, the compressive strength of SSA mortar is similar to that of the control group [99,100]. The use of mineral additives such as metakaolin, nano-silica and multi-component cement [113,114] can also reduce the adverse effect of SSA on the compressive strength of mortar. For example, the use of nano-silica accelerates the hydration reaction of cement, promotes the nucleation and crystal growth of hydration products [66], and then improves the compressive strength of mortar. This also shows that CaO and the other oxides in SSA have an important impact on the compressive strength of mortar without the addition of other substances.
The compressive strength of mortar is related to the ratio of CaO/SiO2 and the ratio of SiO2/Al2O3. The increasing ratio of CaO/SiO2 is beneficial to the improvement of compressive strength of mortar, while the increasing ratio of SiO2/Al2O3 has an adverse effect on the compressive strength of mortar. Figure 8 shows the content of cement and SSA in mortar (by weight) and the 28-day compressive strength of mortar in different literatures. The main oxide content of SSA is summarized in Table 3. When SSA with low CaO content (1.93%) and high SiO2/Al2O3 ratio (3.95) is used, the recycled mortar has the lowest 28-day compressive strength [14]. When SSA with higher CaO content (23.8–32.9%) and higher CaO/SiO2 (1.39–2.03) is used, the compressive strength of mortar is higher [18,25]. However, when SSA with low CaO content (1.863%) and high SiO2/Al2O3 (2.61) is used, the 28-day compressive strength of mortar is the highest among the samples, which mainly attributes to the lowest replacement ratio of SSA (5%) [16]. In addition, the 28-day compressive strength of mortar ranks second of all samples when SSA with SiO2/Al2O3 of 3.35 is used at the replacement rate of 20%. This can be explained by the use of CEM II/B-M (V-LL) 42.5R cement, which is considered as an ideal material for preparing SSA mortar in reference [114]. The compound use of SSA and CEM II/B-M (V-LL) 42.5R cement can promote the bonding of mortar. In addition, a limited reduction for the compressive strength appears when the SiO2/Al2O3 ratio in SSA is similar to that of fly ash (about 2.4) [21,115,116,117].

3.5. Flexural Strength

The 28-day flexural strength of mortar containing SSA is generally lower than that of cement mortar. In consistence with the trend of compressive strength, the higher the replacement ratio is, the lower the flexural strength is, as shown in Figure 9 [15,19,99,114,118,119,120,121,122]. However, a few researchers found that the 28-day flexural strength of SSA mortar is higher than that of cement mortar at low replacement ratio, which results from the high-water absorption and filling effect of SSA. The effective water to cement ratio of the mortar is reduced due to the high-water absorption [92], and the cement dilution effect is offset [15]. However, a great reduction in flexural strength can be obtained when the replacement rate of SSA is higher than 30%, due to the low reactivity of SSA [19].
The addition of mineral admixtures, such as silica fume and metakaolin, can improve the flexural strength of mortar. The flexural strength of mortar mixed with 10% silica fume and 20% SSA was slightly higher than that of cement mortar. The optimum dosage is 10% metakaolin with the SSA replacement rate of 20%, in which case, the flexural strength is 28.32% higher than cement mortar [99]. The source and treatment process of SSA have an important influence on the flexural strength of mortar. For example, the 28-day flexural strength of mortar prepared by SSA calcined at 700 °C is higher than mortar prepared by SSA calcined at 600 °C when keeping the same source of SSA and the replacement ratio of 10% [118]. Avlík et al. [123] found that the pozzolanic activity of SSA was low due to the coarse particles (even though it has 41% amorphous substances).

3.6. Durability

Most studies show that the drying shrinkage of mortar is increased as the incorporation of SSA [15,19,124,125], as shown in Figure 10. This is related to the large porosity of mortar with SSA, which increases the loss of free water in the evaporation process [19,126,127,128]. The grinding process on SSA increases the drying shrinkage when the replacement ratio keeps the same [15]. The higher the calcined temperature is, the larger the drying shrinkage is. Liu et al. [124] found that the drying shrinkage of mortar with SSA at 900 °C was the largest when compared with mortar containing 30% SSA calcined at 500–900 °C. This phenomenon was related to the maximum porosity and average pore size of SSA mortar at 900 °C, which confirmed that the drying shrinkage of mortar was closely related to its porosity [129].
The incorporation of SSA can increase the capillary water absorption of mortar. The grinding process on SSA can enhance the capillary water absorption coefficient of mortar [130], which may be due to the higher specific surface area of SSA after grinding [14,131], resulting in the increase of the number of pores in mortar. The study by Krejcirikova et al. [132] indicated that the water permeability of mortar is enhanced as SSA is incorporated. Further, the water permeability of mortar is improved with the increase of SSA replacement ratio.
The freeze-thaw resistance of mortar is related to its pore structure. Water in the pores of mortar starts to freeze when temperature drops to a specific level, and then results in the volume expansion [133]. The expansion further damages the microstructure of mortar and induces the unfrozen water in the pores of the mortar to migrate outwards. Liu et al. [124] found that the average pore size is 4.9% for recycled mortar with 30% SSA, which is lower than that of cement mortar. The mass loss of recycled mortar with SSA after 100 freeze-thaw cycles was 2.5% lower than cement mortar. Similar results are obtained in references [103,134,135], showing that mortar with SSA has higher freeze-thaw resistance.
In addition, the carbonation of mortar with 20% SSA meet the requirement of the quality index of T-IV according to the Chinese code JGJ/T 193-2009 [136]. It can be determined that the application of SSA from different references has different influence on the performance of mortar, which is caused by their various sources and production process. Besides, there is little research on thermal performance of mortar with SSA at present, which should be studied in the future [137].

3.7. The Influence Mechanism of SSA on the Properties of Mortar

The influence mechanism of SSA on the properties of mortar can be summarized into two main points. On the one hand, the utilization of SSA has a dilutive effect on the cement paste, resulting in low content of active composition. Thus, the strength and durability is reduced due to the loose microstructure. On the other hand, the pozzolanic activity, filling effect, and self-curing effect of SSA have positive effect on the properties of mortar. Firstly, the pozzolanic activity of SSA contributes to the mechanical properties of mortar. SSA can react with the hydration products Ca(OH)2 and produce C-S-H gel. Besides, the finer SSA particles provides the nucleation site for cement, contributing to the hydration of cement and dense structure of mortar [39]. Secondly, SSA contributes to the strength of cement mortar through a variety of interactions, including reducing the effective water to cement ratio, releasing water required for cement hydration by porous structure, forming dicalcium phosphate crystals, as well as the irregular shape of SSA [15]. Thirdly, the finer particles of SSA after grinding have the filling effect in mortar. These reasons can be proven by the investigation on the microstructure of mortar with SSA, such as the SEM images and pore properties.
The microcracks and un-hydrated SSA particles trapped between the hydration products can be found in Figure 11a–c, which contributes to the reduction of mechanical properties and durability [85,95]. The smaller the SSA particle size is, the denser the mortar structure is [32], see Figure 11d–f. The incorporation of SSA can produce more ettringite and sulfate, which is negative to the mechanical properties of mortar. However, it is found that the addition of nano-Al2O3 and nano-SiO2 can fill in the pores between C-S-H and C-A-H gels to densify the microstructure and improve compressive strength (Figure 11g–i) [138].
In addition, Wang found the calcined temperature has great influence on the microstructure of mortar. The interfacial bonding effect of mortar doped with 700 °C SSA is better than that of mortar doped with SSA at other temperatures, but the compactness has limited change, which is related to the irregular morphology of SSA [87].
Porosity is an important parameter affecting the mechanical properties and durability of mortar. When mortar is exposed to humid environment, the pores in mortar provide channels for water, chloride ion penetration and carbonation. The strength is affected by the addition of mineral admixtures (such as fly ash, slag and limestone), which can be explained by the optimized pore size and pore structure [139,140,141,142,143,144,145]. Figure 12 shows the porosity of mortar containing SSA with the replacement ratio of 0–60%. It can be detrmined that the porosity of mortar increases by 0.2–14.53% with the increase of SSA content. On average, the porosity of mortar increases by 3.73% for every 20% increase of SSA, which leads to the decrease of mechanical properties and durability for mortar.

4. Conclusions

The SSA can be used in mortar to partly replace cement after a production process of drying, incineration and grinding, which can promote the resource utilization of sewage sludge and reduce the consumption of cement. This study investigated the basic properties of SSA and its effect on the properties of mortar. The results can be concluded as follows.
(1) The specific gravity of SSA is lower than cement. Most studies show that the particle size distribution of SSA is 2.5–250 μm. SSA contains active oxides such as SiO2, Al2O3, Fe2O3 and CaO, which are similar to the active oxides in fly ash, indicating that SSA has the potential to be used as a pozzolanic material.
(2) The leaching concentration is much lower than the required values in relevant specifications, leading to an allowable environment influence. The physical properties of SSA, such as density and particle size, are closely related to the source and production process. The proportion of oxides in SSA has a great discreteness.
(3) The addition of SSA has a negative impact on the workability, setting time, water absorption and compressive strength of most mortars, which is mainly related to the porous properties and irregular particle morphology of SSA. The performance of mortar can be improved by grinding and using admixtures, but the improvement effect is limited. The raise of incineration temperature can increase the content of amorphous SiO2, which has a positive effect on the pozzolanic reactivity of SSA.
(4) Most studies show that the addition of SSA can increase the porosity, drying shrinkage and capillary water absorption of mortar. Few studies show that the micro-aggregate filling effect of SSA can refine the pore size of mortar matrix and improve the freeze-thaw resistance of mortar. The microstructure and durability of SSA mortar can be improved by incorporating nano materials or selecting 700 °C SSA incineration temperature.
In conclusion, SSA can be used in mortar with a certain replacement ratio. However, due to the different sources and production process, the basic properties of SSA are different, leading to various or even opposite influences on the mechanical properties and durability. Therefore, the optimal replacement ratios of SSA in different literatures are various. In the future, the sources of SSA should be selected before its utilization to control its chemical properties. In addition, standards for the preparation methods, test methods and utilization of SSA should be proposed for its application promotion.

Author Contributions

Conceptualization, C.L.; writing—original draft preparation, X.L.; methodology, W.F.; validation, L.F. and J.Z.; writing—review and editing, S.H. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by Science and Technology R&D Project of Ministry of Housing and Urban-Rural Development of China, grant number 2021-K-123.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Chen, H.; Yan, S.H.; Ye, Z.L.; Meng, H.J.; Zhu, Y.G. Utilization of urban sewage sludge: Chinese Perspectives. Environ. Sci. Pollut. Res. 2012, 19, 1454–1463. [Google Scholar] [CrossRef] [PubMed]
  2. Ministry of Housing and Urban-Rural Development of the People’s Republic of China. Available online: http://www.mohurd.gov.cn/ (accessed on 24 November 2021).
  3. Kacprzak, M.; Neczaj, E.; Fijałkowski, K.; Grobelak, A.; Grosser, A.; Worwag, M.; Rorat, A.; Brattebo, H.; Almås, Å.; Singh, B.R. Sewage sludge disposal strategies for sustainable development. Environ. Res. 2017, 156, 39–46. [Google Scholar] [CrossRef] [PubMed]
  4. Yang, T.; Xiao, Y.; Huang, H.; Lai, F.; Chang, Y.; Pan, Z.; Xiao, X. Assessment optimization of the contamination degree and ecological risk of heavy metals in sewage sludge. Environ. Sci. Technol. 2019, 42, 202–209. (In Chinese) [Google Scholar]
  5. Wang, N.; Li, Y. Disposal status analysis and resource utilization of residual sludge in dingdao. Environ. Sci. Manag. 2010, 35, 82–84. (In Chinese) [Google Scholar]
  6. Jointly Issued by the Development and Reform Commission and the Ministry of Housing and Construction. The Implementation Plan for Strength and Weakness of Municipal Sewage Treatment Facilities. Available online: https://huanbao.bjx.com.cn/news/20200731/1093761.shtml (accessed on 28 July 2020).
  7. Yusuf, R.O.; Noor, Z.Z.; Moh’, N.A.; Moh’d, F.; Moh’d, D.; Abba, A.H. Use of sewage sludge ash (SSA) in the production of cement and concrete—A review. Int. J. Glob. Environ. Issues 2012, 12, 214–228. [Google Scholar] [CrossRef]
  8. Lynn, C.J.; Dhir, R.K.; Ghataora, G.S.; West, R.P. Sewage sludge ash characteristics and potential for use in concrete. Constr. Build. Mater. 2015, 98, 767–779. [Google Scholar] [CrossRef] [Green Version]
  9. Liang, Y.; Xu, D.; Feng, P.; Hao, B.; Guo, Y.; Wang, S. Municipal sewage sludge incineration and its air pollution control. J. Clean. Prod. 2021, 295, 126456. [Google Scholar] [CrossRef]
  10. Mu’azu, N.D.; Jarrah, N.; Zubair, M.; Alagha, O. Removal of Phenolic Compounds from Water Using Sewage Sludge-Based Activated Carbon Adsorption: A Review. Int. J. Environ. Res. Public Health 2017, 14, 1094. [Google Scholar] [CrossRef] [Green Version]
  11. Ihsanullah, I.; Khan, M.T.; Zubair, M.; Bilal, M.; Sajid, M. Removal of pharmaceuticals from water using sewage sludge-derived biochar: A review. Chemosphere 2022, 289, 133196. [Google Scholar] [CrossRef]
  12. Scrivener, K.; John, V.M.; Gartner, E.M. Eco-efficient cements: Potential Economically Viable Solutions for a Low-CO2 Cement-based Materials Industry. Cem. Concr. Res. 2018, 114, 2–26. [Google Scholar] [CrossRef]
  13. Gabel, K.; Tillman, A.M. Simulating operational alternatives for future cement production. J. Clean. Prod. 2005, 13, 1246–1257. [Google Scholar] [CrossRef] [Green Version]
  14. Pan, S.C.; Tseng, D.H.; Lee, C.C.; Lee, C. Influence of the fineness of sewage sludge ash on the mortar properties. Cem. Concr. Res. 2003, 33, 1749–1754. [Google Scholar] [CrossRef]
  15. Chen, Z.; Poon, C.S. Comparative studies on the effects of sewage sludge ash and fly ash on cement hydration and properties of cement mortars. Constr. Build. Mater. 2017, 154, 791–803. [Google Scholar] [CrossRef]
  16. Zhang, Q. Study on Mechanical Properties and Heavy Metal Curing Capacity of Cement-Based Materials Mixed with Sludge. Master’s Thesis, Engineering, Harbin Institute of Technology, Harbin, China, 2017. (In Chinese). [Google Scholar]
  17. Chen, Z.; Poon, C.S. Comparing the use of sewage sludge ash and glass powder in cement mortars. Environ. Technol. 2017, 38, 1390–1398. [Google Scholar] [CrossRef] [PubMed]
  18. Monzó, J.; Payá, J.; Borrachero, M.V.; Córcoles, A. Use of sewage sludge ash (SSA)-cement admixtures in mortars. Cem. Concr. Res. 1996, 26, 1389–1398. [Google Scholar] [CrossRef]
  19. Li, J.S.; Guo, M.Z.; Xue, Q.; Poon, C.S. Recycling of incinerated sewage sludge ash and cathode ray tube funnel glass in cement mortars. J. Clean. Prod. 2017, 152, 142–149. [Google Scholar] [CrossRef]
  20. Smol, M.; Kulczycka, J.; Henclik, A. The possible use of sewage sludge ash (SSA) in the construction industry as a way towards a circular economy. J. Clean. Prod. 2015, 95, 45–54. [Google Scholar] [CrossRef]
  21. Świerczek, L.; Cieślik, B.M.; Konieczka, P. Challenges and opportunities related to the use of sewage sludge ash in cement-based building materials–A review. J. Clean. Prod. 2021, 287, 125054. [Google Scholar] [CrossRef]
  22. Tay, J.H.; Show, K.Y. Municipal wastewater sludge as cementitious and blended cement materials. Cem. Concr. Compos. 1994, 16, 39–48. [Google Scholar] [CrossRef]
  23. Chen, X.; Li, J.; Xue, Q.; Huang, X.; Liu, L.; Poon, C.S. Sludge biochar as a green additive in cement-based composites: Mechanical Properties and Hydration Kinetics. Constr. Build. Mater. 2020, 262, 120723. [Google Scholar] [CrossRef]
  24. Cong, X.; Lu, S.; Gao, Y.; Yao, Y.; Elchalakani, M.; Shi, X. Effects of microwave, thermomechanical and chemical treatments of sewage sludge ash on its early-age behavior as supplementary cementitious material. J. Clean. Prod. 2020, 258, 120647. [Google Scholar] [CrossRef]
  25. Kappel, A.; Ottosen, L.M.; Kirkelund, G.M. Colour, compressive strength and workability of mortars with an iron rich sewage sludge ash. Constr. Build. Mater. 2017, 157, 1199–1205. [Google Scholar] [CrossRef] [Green Version]
  26. Chen, M.; Blanc, D.; Gautier, M.; Mehu, J.; Gourdon, R. Environmental and technical assessments of the potential utilization of sewage sludge ashes (SSAs) as secondary raw materials in construction. Waste Manag. 2013, 33, 1268–1275. [Google Scholar] [CrossRef]
  27. Lynn, C.J.; Dhir, R.K.; Ghataora, G.S. Environmental impacts of sewage sludge ash in construction: Leaching Assessment. Resour. Conserv. Recycl. 2018, 136, 306–314. [Google Scholar] [CrossRef]
  28. Classification of Medium, Coarse and Fine Sand, National Standard Size. Available online: https://www.docin.com/p-2295143164.html (accessed on 12 January 2020).
  29. Valls, S.; Yagüe, A.; Vázquez, E.; Mariscal, C. Physical and mechanical properties of concrete with added dry sludge from a sewage treatment plant. Cem. Concr. Res. 2004, 34, 2203–2208. [Google Scholar] [CrossRef]
  30. Huang, C.H.; Wang, S.Y. Application of water treatment sludge in the manufacturing of lightweight aggregate. Constr. Build. Mater. 2013, 43, 174–183. [Google Scholar] [CrossRef]
  31. Zhou, Y.; Lu, J.; Li, J.; Cheeseman, C.; Poon, C.S. Effect of NaCl and MgCl2 on the hydration of lime-pozzolan blend by recycling sewage sludge ash. J. Clean. Prod. 2021, 313, 127759. [Google Scholar] [CrossRef]
  32. Lin, K.L.; Chang, W.C.; Lin, D.F.; Luo, H.L.; Tsai, M.C. Effects of nano-SiO2 and different ash particle sizes on sludge ash-cement mortar. J. Environ. Manag. 2008, 88, 708–714. [Google Scholar] [CrossRef]
  33. Li, X.G.; He, C.H.; Lv, Y.; Jian, S.W.; Liu, G.; Jiang, W.G.; Jiang, D.B. Utilization of municipal sewage sludge and waste glass powder in production of lightweight aggregates. Constr. Build. Mater. 2020, 256, 119413. [Google Scholar] [CrossRef]
  34. Monzó, J.; Payá, J.; Borrachero, M.V.; Girbés, I. Reuse of sewage sludge ashes (SSA) in cement mixtures: The Effect of SSA on the Workability of Cement Mortars. Waste Manag. 2003, 23, 373–381. [Google Scholar] [CrossRef]
  35. Pan, L. Application of fly ash in ceramic plate. Ceramics 2015, 41, 36–39. (In Chinese) [Google Scholar]
  36. Zhu, B.; Dai, R.; Hu, C.Y. Experimental study of application of fiy ash polypropylene fiber and other materials in sludge solidification. Fly Ash. 2016, 28, 5–7. (In Chinese) [Google Scholar]
  37. Zhang, Y.; Wang, Z.; Wang, Z.Y.; Sun, H.Q.; Wang, L.L.; Wen, C.M.; Zhang, Y.T.; Tang, Z.D. Effect of denitrification in thermal power plant on properties of fiy ash. Non-Met. Mines. 2015, 38, 9–12. (In Chinese) [Google Scholar]
  38. Li, C.C.; Xu, Z.R.; Chen, T.D. Effect of fly ash on thaumasite form of sulfate attack. J. Build. Mater. 2014, 17, 685–689. [Google Scholar]
  39. Scrivener, K.L.; Juilland, P.; Monteiro, P.J.M. Advances in understanding hydration of Portland cement. Cem. Concr. Res. 2015, 78, 38–56. [Google Scholar] [CrossRef]
  40. Kazberuk, M.K. Application of SSA as partial replacement of aggregate in concrete. Pol. J. Environ. Stud. 2011, 20, 365–370. [Google Scholar]
  41. Balonis, M. Thermodynamic modelling of temperature effects on the mineralogy of Portland cement systems containing chloride. Cem. Concr. Res. 2019, 120, 66–76. [Google Scholar] [CrossRef]
  42. Cheng, M.; Wu, L.; Huang, Y.; Luo, Y.; Christie, P. Total concentrations of heavy metals and occurrence of antibiotics in sewage sludges from cities throughout China. J. Soils Sediments 2014, 14, 1123–1135. [Google Scholar] [CrossRef]
  43. Tella, M.; Doelsch, E.; Letourmy, P.; Chataing, S.; Cuoq, F.; Bravin, M.N.; Saint Macary, H. Investigation of potentially toxic heavy metals in different organic wastes used to fertilize market garden crops. Waste Manag. 2013, 33, 184–192. [Google Scholar] [CrossRef]
  44. Ščančar, J.; Milačič, R.; Stražar, M.; Burica, O. Total metal concentrations and partitioning of Cd, Cr, Cu, Fe, Ni and Zn in sewage sludge. Sci. Total Environ. 2000, 250, 9–19. [Google Scholar] [CrossRef]
  45. Cyprowski, M.; Krajewski, J.A. Harmful agents in municipal wastewater treatment plants. Med. Pr. 2003, 54, 73–80. [Google Scholar] [PubMed]
  46. Mulchandani, A.; Westerhoff, P. Recovery opportunities for metals and energy from sewage sludges. Bioresour. Technol. 2016, 215, 215–226. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  47. Kendir, E.; Kentel, E.; Sanin, F.D. Evaluation of heavy metals and associated health risks in a metropolitan wastewater treatment plant’s sludge for its land application. Hum. Ecol. Risk Assess. 2019, 21, 1631–1643. [Google Scholar] [CrossRef]
  48. Lu, Q.; He, Z.L.; Stoffella, P.J. Land application of biosolids in the USA: A Review. Appl. Environ. Soil Sci. 2012, 2012, 1–11. [Google Scholar] [CrossRef] [Green Version]
  49. Antunes, E.; Schumann, J.; Brodie, G.; Jacob, M.V.; Schneider, P.A. Biochar produced from biosolids using a single-mode microwave: Characterisation and its potential for phosphorus removal. J. Environ. Manag. 2017, 196, 119–126. [Google Scholar] [CrossRef]
  50. Coutand, M.; Cyr, M.; Clastres, P. Use of sewage sludge ash as mineral admixture in mortars. Constr. Mater. 2006, 159, 153–162. [Google Scholar] [CrossRef]
  51. Franz, M. Phosphate fertilizer from sewage sludge ash (SSA). Waste Manag. 2008, 28, 1809–1818. [Google Scholar] [CrossRef]
  52. Chiou, I.J.; Wang, K.S.; Chen, C.H.; Lin, Y.T. Lightweight aggregate made from sewage sludge and incinerated ash. Waste Manag. 2006, 26, 1453–1461. [Google Scholar] [CrossRef]
  53. Morais, L.C.; Dweck, J.; Goncalves, E.M.; Buchler, P.M. An experimental study of sewage sludge incineration. Environ. Technol. 2005, 27, 1047–1051. [Google Scholar] [CrossRef]
  54. Adam, C.; Peplinski, B.; Michaelis, M.; Kley, G.; Simon, F.G. Thermochemical treatment of sewage sludge ashes for phosphorus recovery. Waste Manag. 2009, 29, 1122–1128. [Google Scholar] [CrossRef]
  55. Lin, K.L.; Lin, C.Y. Hydration properties of eco-cement pastes from waste sludge ash clinkers. J. Air Waste Manag. Assoc. 2004, 54, 1534–1542. [Google Scholar] [CrossRef] [PubMed]
  56. Lin, K.L.; Lin, C.Y. Hydration characteristics of waste sludge ash utilized as raw cement material. Cem. Concr. Res. 2005, 35, 1999–2007. [Google Scholar] [CrossRef]
  57. Lin, K.L.; Chiang, K.Y.; Lin, D.F. Effect of heating temperature on the sintering characteristics of sewage sludge ash. J. Hazard. Mater. 2006, 128, 175–181. [Google Scholar] [CrossRef] [PubMed]
  58. Lin, K.L.; Huang, W.J.; Chen, K.C.; Chow, J.D.; Chen, H.J. Behaviour of heavy metals immobilized by co-melting treatment of sewage sludge ash and municipal solid waste incinerator fly ash. Waste Manag. Res. 2009, 27, 660–667. [Google Scholar] [CrossRef]
  59. Saikia, N.; Kato, S.; Kojima, T. Compositions and leaching behaviours of combustion residues. Fuel 2006, 85, 264–271. [Google Scholar] [CrossRef]
  60. Zhang, Z.; Zhang, L.; Yin, Y.; Liang, X.; Li, A. The recycling of incinerated sewage sludge ash as a raw material for CaO–Al2O3–SiO2–P2O5 glass ceramic production. Environ. Technol. 2015, 36, 1098–1103. [Google Scholar] [CrossRef]
  61. Fraissler, G.; Joller, M.; Mattenberger, H.; Brunner, T.; Obernberger, I. Thermodynamic equilibrium calculations concerning the removal of heavy metals from sewage sludge ash by chlorination. Chem. Eng. Process 2009, 48, 152–164. [Google Scholar] [CrossRef]
  62. Mattenberger, H.; Fraissler, G.; Brunner, T.; Herk, P.; Hermann, L.; Obernberger, I. Sewage sludge ash to phosphorus fertiliser: Variables Influencing Heavy Metal Removal During Thermochemical Treatment. Waste Manag. 2008, 28, 2709–2722. [Google Scholar] [CrossRef]
  63. Vogel, C.; Exner, R.M.; Adam, C. Heavy metal removal from sewage sludge ash by thermochemical treatment with polyvinylchloride. Environ. Sci. Technol. 2013, 47, 563–567. [Google Scholar] [CrossRef]
  64. Vogel, C.; Adam, C.; Kappen, P.; Schiller, T.; Lipiec, E.; McNaughton, D. Chemical state of chromium in sewage sludge ash based phosphorus fertilisers. Chemosphere 2014, 103, 250–255. [Google Scholar] [CrossRef]
  65. Erich Schmitt. Merkblatt Entsorgung von Abfällen aus Verbrennungsanlagen für Siedlungsabfälle; Beschlossen durch die Länder-Arbeitsgemeinschaft Abfall (LAGA): Berlin, Germany, 1994. [Google Scholar]
  66. Lin, D.F.; Lin, K.L.; Luo, H.L.; Cai, M.Q. Improvements of nano-SiO2 on sludge/fly ash mortar. Waste Manag. 2008, 28, 1081–1087. [Google Scholar] [CrossRef] [PubMed]
  67. Chang, Z.; Long, G.; Zhou, J.L.; Ma, C. Valorization of sewage sludge in the fabrication of construction and building materials: A Review. Resour. Conserv. Recycl. 2020, 154, 104606. [Google Scholar] [CrossRef]
  68. Bhatty, J.I.; Malisci, A.; Iwasaki, I.; Reid, K.J. Sludge ash pellets as coarse aggregate in concrete. J. Cem. Concr. Aggreg. 1992, 14, 55–61. [Google Scholar] [CrossRef]
  69. Chen, L.; Lin, D.F. Applications of sewage sludge ash and nano-SiO2 to manufacture tile as construction material. Constr. Build. Mater. 2009, 23, 3312–3320. [Google Scholar] [CrossRef]
  70. Chen, C.H.; Chiou, I.J.; Wang, K.S. Sintering effect on cement bonded sewage sludge ash. Cem. Concr. Res. 2006, 28, 26–32. [Google Scholar] [CrossRef]
  71. Chen, Z.; Li, J.S.; Poon, C.S. Combined use of sewage sludge ash and recycled glasewage sludge cullet for the production of concrete blocks. J. Clean. Prod. 2018, 171, 1447–1459. [Google Scholar] [CrossRef]
  72. Huang, Y.C.; Li, K.C. Effect of reducing conditions on sludge melting process. Chemosphere 2003, 50, 1063–1068. [Google Scholar] [CrossRef]
  73. Khanbilvardi, R.; Afshari, S. Sludge ash as fine aggregate for concrete mix. J. Environ. Eng. 1995, 121, 633–638. [Google Scholar] [CrossRef]
  74. Latosinska, J. The evaluation of the impact of sewage sludge ash modification on leaching of heavy metals. Adv. Civ. Environ. Eng. 2014, 1, 27–42. [Google Scholar]
  75. Li, J.S.; Xue, Q.; Fang, L.; Poon, C.S. Characteristics and metal leachability of incinerated sewage sludge ash and air pollution control residues from Honk Kong evaluated by different methods. Waste Manag 2017, 64, 161–170. [Google Scholar] [CrossRef]
  76. Li, J.S.; Tsang, D.C.W.; Wang, Q.M.; Fang, L.; Xue, Q.; Poon, C.S. Fate of metals before and after chemical extraction of incinerated sewage sludge ash. Chemosphere 2017, 186, 350–359. [Google Scholar] [CrossRef] [PubMed]
  77. Lin, K.L. Mineralogy and microstructure of sintered sewage sludge ash as lightweight aggregates. J. Ind. Eng. Chem. 2006, 12, 425–429. [Google Scholar]
  78. Lin, D.F.; Weng, C.H. Use of sewage sludge ash as brick material. J. Environ. Eng. 2001, 127, 922–927. [Google Scholar] [CrossRef]
  79. Lin, D.F.; Luo, H.L.; Sheen, Y.N. Glazed tiles manufactured from incinerated sludge ash and clay. J. Air Waste Manag. Assoc. 2005, 55, 163–172. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  80. Lin, D.F.; Luo, H.L.; Halao, D.H.; Yang, C.C. The effects of sludge ash on the strength of soft subgrade soil. J. Chin. Inst. Environ. Eng. 2005, 15, 1–10. [Google Scholar]
  81. Tsai, C.C.; Wang, K.S.; Chiou, I.J. Effect of SiO2–Al2O3–flux ratio change on the bloating characteristics of lightweight aggregate material produced from recycled sewage sludge. J. Hazard. Mater. 2006, 134, 87–93. [Google Scholar] [CrossRef]
  82. Wang, X.; Yuan, W.; Yuan, H. Cement-based solidification of incinerated sewage sludge ash by the addition of a novel solidifying aid. Int. J. Waste Resour. 2015, 5, 1–5. [Google Scholar] [CrossRef]
  83. Weng, C.H. Removal of Nickel(II) from dilute aqueous solution by sludge-ash. J. Environ. Eng. 2002, 128, 716–722. [Google Scholar] [CrossRef]
  84. Chang, F.C.; Lin, J.D.; Tsai, C.C.; Wang, K.S. Study on cement mortar and concrete made with sewage sludge ash. Water Sci. Technol. 2010, 62, 1689–1693. [Google Scholar] [CrossRef]
  85. Hsu, C.W.; Chen, C.T. Strength development of cement pastes with alkali-activated dehydrated sewage sludge. Constr. Build. Mater. 2020, 255, 119243. [Google Scholar] [CrossRef]
  86. Zhou, Y.; Li, J.; Lu, J.; Lu, J.; Cheeseman, C.; Poon, C.S. Recycling incinerated sewage sludge ash (ISSA) as a cementitious binder by lime activation. J. Clean. Prod. 2020, 244, 118856. [Google Scholar] [CrossRef]
  87. Wang, S. The Effect of Sludge Ash Treated at Different Calcination Temperatures on the Performance of Cement Mortar. Full-time. Master’s Thesis, Engineerring, Harbin Institute of Technology, Harbin, China, 2015. (In Chinese). [Google Scholar]
  88. De Carvalho Gomes, S.; Zhou, J.L.; Li, W.; Long, G. Progress in manufacture and properties of construction materials incorporating water treatment sludge: A Review. Resour. Conserv. Recycl. 2019, 145, 148–159. [Google Scholar] [CrossRef]
  89. Donatello, S.; Tyrer, M.; Cheeseman, C.R. Comparison of test methods to assess pozzolanic activity. Cem. Concr. Res. 2010, 32, 121–127. [Google Scholar] [CrossRef] [Green Version]
  90. ASTM C618-17a. Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete. ASTM Int’L: West Conshohocken, PA, USA, 2017.
  91. IS 1344. Specification for Calcined Clay Pozzolana. Bureau of Indian Standards (BIS): New Delhi, India, 1981.
  92. Pan, S. Use of sewage sludge ash as fine aggregate and pozzolan in portland cement mortar. J. Solid Waste Technol. Manag. 2002, 28, 121–130. [Google Scholar]
  93. Pan, S.C.; Tseng, D.H. Sewage sludge ash characteristics and its potential applications. Water Sci. Technol. 2001, 44, 261–267. [Google Scholar] [CrossRef]
  94. Quarcioni, V.A.; Chotoli, F.F.; Coelho, A.C.V.; Cincotto, M.A. Indirect and direct Chapelle’s methods for the determination of lime consumption in pozzolani materials. IBRACON Struct. Mater. J. 2015, 8, 1–7. [Google Scholar]
  95. Ahmad, T.; Ahmad, K.; Alam, M. Investigating calcined filter backwash solids as supplementary cementitious material for recycling in construction practices. Constr. Build. Mater. 2018, 175, 664–671. [Google Scholar] [CrossRef]
  96. Donatello, S.; Tong, D.; Cheeseman, C.R. Production of technical grade phosphoric acid from incinerator sewage sludge ash (ISSA). Waste Manag. 2010, 30, 1634–1642. [Google Scholar] [CrossRef] [Green Version]
  97. Basto, P.A.; Junior, H.S.; Neto, A.A.M. Characterization and pozzolanic properties of sewage sludge ashes (SSA) by electrical conductivity. Cem. Concr. Compos. 2019, 104, 103410. [Google Scholar] [CrossRef]
  98. Naamane, S.; Rais, Z.; Taleb, M. The effectiveness of the incineration of sewage sludge on the evolution of physicochemical and mechanical properties of Portland cement. Constr. Build. Mater. 2016, 112, 783–789. [Google Scholar] [CrossRef]
  99. Vouk, D.; Serdar, M.; Vučinić, A.A. Use of incinerated sewage sludge ash in cement mortars: Case Sudy in Croatia. Tech. Gaz. 2017, 24, 43–51. [Google Scholar]
  100. Monzo, J.; Paya, J.; Borrachero, M.V.; Bellver, A.; Peris-Mora, E. Study of cement-based mortars containing Spanish ground sewage sludge ash. Waste Mater. Constr. 1997, 38, 349–354. [Google Scholar]
  101. Rutkowska, G.; Wichowski, P.; Fronczyk, J.; Franus, M.; Chalecki, M. Use of fly ashes from municipal sewage sludge combustion in production of ash concretes. Constr. Build. Mater. 2018, 188, 874–883. [Google Scholar] [CrossRef]
  102. Chakraborty, S.; Jo, B.W.; Jo, J.H.; Baloch, Z. Effectiveness of sewage sludge ash combined with waste pozzolanic minerals in developing sustainable construction material: An Alternative Approach for Waste Management. J. Clean. Prod. 2017, 153, 253–263. [Google Scholar] [CrossRef]
  103. Pinarli, V. Sustainable waste management—Studies on the use of sewage sludge ash in construction industry as concrete material. In Sustainable Construction: Use Incinerator Ash; Thomas Telford Publishing: London, UK, 2000; pp. 415–425. [Google Scholar]
  104. Mejdi, M.; Saillio, M.; Chaussadent, T.; Divet, L.; Tagnit-Hamou, A. Hydration mechanisms of sewage sludge ashes used as cement replacement. Cem. Concr. Res. 2020, 135, 106115. [Google Scholar] [CrossRef]
  105. Piasta, W.; Lukawska, M. The effect of sewage sludge ash on properties of cement composites. Procedia Eng. 2016, 161, 1018–1024. [Google Scholar] [CrossRef] [Green Version]
  106. Rahman, M.M.; Khan, M.M.R.; Uddin, M.T.; Islam, M.A. Textile Effluent Treatment Plant Sludge: Characterization and Utilization in Building Materials. Arab. J. Sci. Eng. 2017, 42, 1435–1442. [Google Scholar] [CrossRef]
  107. Pan, S.C.; Lin, C.C.; Tseng, D.H. Reusing sewage sludge ash as adsorbent for copper removal from wastewater. Resour. Conserv. Recycl. 2003, 39, 79–90. [Google Scholar] [CrossRef]
  108. Monzó, J.; Paya, M.V.; Borrachero, E.P.M. Mechanical behavior of mortar containing sewage sludge ash (SSA) and Portland cements with different tricalcium aluminate content. Cem. Concr. Res. 1999, 29, 87–94. [Google Scholar] [CrossRef]
  109. Federico, L.M.; Chidiac, S.E. Waste glasewage sludge as a supplementary cementitious material in concrete—Critical review of treatment methods. Cem. Concr. Compos. 2009, 31, 606–610. [Google Scholar] [CrossRef]
  110. Wang, K.S.; Chiou, I.J.; Chen, C.H.; Wang, D. Lightweight properties and pore structure of foamed material made from sewage sludge ash. Constr. Build. Mater. 2005, 19, 627–633. [Google Scholar] [CrossRef]
  111. Donatello, S.; Freeman-Pask, A.; Tyrer, M.; Cheeseman, C.R. Effect of milling and acid washing on the pozzolanic activity of incinerator sewage sludge ash. Cem. Concr. Res. 2010, 32, 54–61. [Google Scholar] [CrossRef]
  112. Pinarli, V.; Kaymal, G. An innovative sludge disposal option—Reuse of sludge ash by incorporation in construction materials. Environ. Technol. 1994, 15, 843–852. [Google Scholar] [CrossRef]
  113. Baeza-Brotons, F.; Garcés, P.; Payá, J.; Saval, J.M. Portland cement systems with addition of sewage sludge ash. Application in concretes for the manufacture of blocks. J. Clean. Prod. 2014, 82, 112–124. [Google Scholar] [CrossRef] [Green Version]
  114. Garcés, P.; Pérez Carrión, M.; García-Alcocel, E.; Payá, J.; Monzó, J.; Borrachero, M.V. Mechanical and physical properties of cement blended with sewage sludge ash. Waste Manag. 2008, 28, 2495–2502. [Google Scholar] [CrossRef]
  115. Jang, J.G.; Lee, H.K. Effect of fly ash characteristics on delayed high-strength development of geopolymers. Constr. Build. Mater. 2016, 102, 260–269. [Google Scholar] [CrossRef]
  116. Richardson, I.G.; Girão, A.V.; Taylor, R.; Jia, S. Hydration of water- and alkali activated white Portland cement pastes and blends with low-calcium pulverized fuel ash. Cem. Concr. Res. 2016, 83, 1–18. [Google Scholar] [CrossRef] [Green Version]
  117. Suksiripattanapong, C.; Horpibulsuk, S.; Boongrasan, S.; Udomchai, A.; Chinkulkijniwat, A.; Arulrajah, A. Unit weight, strength and microstructure of a water treatment sludge-fly ash lightweight cellular geopolymer. Constr. Build. Mater. 2015, 94, 807–816. [Google Scholar] [CrossRef]
  118. Da Cunha Oliveira, J.V.; Chagas, L.S.V.B.; de Andrade Meira, F.F.D.; Carneiro, A.M.P.; de Melo Neto, A.A. Study of the Potential of Adhesion to the Substrate of Masonry and Tensile in the Flexion in Mortars of Coating with Gray of the Sewage Sludge. Mater. Sci. Forum. 2020, 1012, 256–261. [Google Scholar] [CrossRef]
  119. Pinarli, V.; Emre, N.K. Constructive sludge management—Reutilization of municipal sewage sludge in Portland cement mortars. Environ. Technol. 1994, 15, 833–841. [Google Scholar] [CrossRef]
  120. Nakic, D.; Vouk, D.; Serdar, M.; Cheeseman, C.R. Use of MID-MIX® treated sewage sludge in cement mortars and concrete. Eur. J.Environ. Civ. Eng. 2018, 24, 1–16. [Google Scholar] [CrossRef]
  121. Cyr, M.; Coutand, M.; Clastres, P. Technological and environmental behavior of sewage sludge ash (SSA) in cement-based materials. Cem. Concr. Res. 2007, 37, 1278–1289. [Google Scholar] [CrossRef]
  122. Vouk, D.; Nakic, D.; Stirmer, N.; Cheeseman, C. Influence of combustion temperature on the performance of sewage sludge ash as a supplementary cementitious material. J. Mater. Cycles Waste Manag. 2018, 20, 1458–1467. [Google Scholar] [CrossRef]
  123. Pavlík, Z.; Fořt, J.; Záleská, M.; Pavlíková, M.; Trník, A.; Igor, M.; Keppert, M.; Koutsoukos, P.G.; Černýa, R. Energy-efficient thermal treatment of sewage sludge for its application in blended cements. J. Clean. Prod. 2016, 112, 409–419. [Google Scholar] [CrossRef]
  124. Liu, M.; Zhao, Y.; Yu, Z. Effects of sewage sludge ash produced at different calcining temperatures on pore structure and durability of cement mortars. J. Mater. Cycles Waste Manag. 2021, 23, 755–763. [Google Scholar] [CrossRef]
  125. Sasaoka, N.; Yokoi, K.; Yamahaka, T. Basic study of concrete made using ash derived from the incinerating sewage sludge. Int. J. Mod. Phys. B 2006, 20, 3716–3721. [Google Scholar] [CrossRef]
  126. Pittman, D.W.; Ragan, S.A. Drying shrinkage of roller-compacted concrete for pavement applications. ACI Mater. J. 1998, 95, 19–26. [Google Scholar]
  127. Farzadnia, N.; Noorvand, H.; Yasin, A.M.; Aziz, F.N.A. The efect of nano silica on short term drying shrinkage of POFA cement mortars. Constr. Build. Mater. 2015, 95, 636–646. [Google Scholar] [CrossRef]
  128. Zhang, W.; Zakaria, M.; Hama, Y. Influence of aggregate materials characteristics on the drying shrinkage properties of mortar and concrete. Constr. Build. Mater. 2013, 49, 500–510. [Google Scholar] [CrossRef] [Green Version]
  129. Uygunoglu, T.; Topçu, I.B. The role of scrap rubber particles on the drying shrinkage and mechanical properties of self-consolidating mortars. Constr. Build. Mater. 2010, 24, 1141–1150. [Google Scholar] [CrossRef]
  130. Krejcirikova, B.; Ottosen, L.M.; Kirkelund, G.M.; Rode, C.; Peuhkuri, R. Characterization of sewage sludge ash and its effect on moisture physics of mortar. J. Build. Eng. 2019, 21, 396–403. [Google Scholar] [CrossRef]
  131. Hu, J.; Ge, Z.; Wang, K. Influence of cement fineness and water-to-cement ratio on mortar early-age heat of hydration and set times. Constr. Build. Mater. 2014, 50, 657–663. [Google Scholar] [CrossRef]
  132. Krejcirikova, B.; Rode, C.; Peuhkuri, R. Determination of hygrothermal properties of cementitious mortar: The Effect of Partial Replacement of Cement by Incinerated Sewage Sludge Ash. J. Build. Phys. 2019, 42, 771–787. [Google Scholar] [CrossRef]
  133. Powers, T.C. A working hypothesis for further studied of frost resistance of concrete. J. Am. Concr. Inst. 1945, 41, 245–272. [Google Scholar]
  134. Salihoglu, G.; Mardani-Aghabaglou, A. Characterization of sewage sludge incineration ashes from multi-cyclones and baghouse dust filters as possible cement substitutes. Environ. Sci. Pollut. Res. 2020, 28, 645–663. [Google Scholar] [CrossRef]
  135. Rutkowska, G.; Chalecki, M.; Żółtowski, M. Fly ash from thermal conversion of sludge as a cement substitute in concrete manufacturing. Sustainability 2021, 13, 4182. [Google Scholar] [CrossRef]
  136. Chen, Y. Effect of Activated Water Treatment Sludge on Carbonation of Mortar. Key Eng. Mater. 2013, 539, 120–123. [Google Scholar] [CrossRef]
  137. Nasir, M.; Aziz, M.A.; Zubair, M.; Manzar, M.S.; Ashraf, N.; Mu’azu, N.D.; Al-Harthi, M. Recent review on synthesis, evaluation, and SWOT analysis of nanostructured cellulose in construction applications. J. Build. Eng. 2022, 46, 103747. [Google Scholar] [CrossRef]
  138. Luo, H.L.; Lin, D.F.; Shieh, S.I.; You, Y.F. Micro-observations of different types of nano-Al2O3 on the hydration of cement paste with sludge ash replacement. Environ. Technol. 2014, 36, 2967–2976. [Google Scholar] [CrossRef]
  139. Feldman, R.F. Significance of porosity measurements on blended cement performance. In Fly Ash Silica Fume, Slag and Other Mineral By-Products in Concrete; Special Publication: Farmington, CT, USA, 1983; Volume 79, pp. 415–434. [Google Scholar]
  140. Manmohan, D.; Mehta, P.K. Influence of pozzolana, slag and chemical admixtures on pore size distribution and permeability of hardened cement pastes. ASTM Cem. Concr. Aggreg. 1981, 3, 63–67. [Google Scholar]
  141. Feldman, R.F. Durability of blended cements to high concentration of chloride solutions. In Proceedings of the 5th International Symp. On Concrete Technology, Building Energy Efficiency, Shenyang, China, 21 March 1981; pp. 262–288. [Google Scholar]
  142. Hu, X.; Shi, C.; Shi, Z.; Zhang, L. Compressive strength, pore structure and chloride transport properties of alkali-activated slag/fly ash mortars. Cem. Concr. Compos. 2019, 104, 103392. [Google Scholar] [CrossRef]
  143. Pandey, S.; Sharma, R. The influence of mineral additives on the strength and porosity of OPC mortar. Cem. Concr. Res. 2000, 30, 19–23. [Google Scholar] [CrossRef]
  144. Zelić, J.; Krstulović, R.; Tkalčec, E.; Krolo, P. The properties of Portland cement-limestone-silica fume mortars. Cem. Concr. Res. 2000, 30, 145–152. [Google Scholar] [CrossRef]
  145. Menéndez, G.; Bonavetti, V.; Irassar, E. Strength development of ternary blended cement with limestone filler and blast-furnace slag. Cem. Concr. Compos. 2003, 25, 61–67. [Google Scholar] [CrossRef]
  146. Alcocel, E.G.; Garcés, P.; Martínez, J.J.; Payá, J.; Andión, L.G. Effect of sewage sludge ash (SSA) on the mechanical performance and corrosion levels of reinforced Portland cement mortars. Mater. Constr. 2006, 56, 31–43. [Google Scholar]
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Figure 1. Number of sewage treatment plants and annual sewage discharge from 2008 to 2020 [2].
Figure 1. Number of sewage treatment plants and annual sewage discharge from 2008 to 2020 [2].
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Figure 2. Visual analysis of the literature on SSA.
Figure 2. Visual analysis of the literature on SSA.
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Figure 3. Particle size distribution of SSA [15,16,17,18,23,24,25,26,27,28].
Figure 3. Particle size distribution of SSA [15,16,17,18,23,24,25,26,27,28].
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Figure 4. Comparison of chemical composition for SSA, fly ash, and cement [17,23,33,34,35,36,37,38].
Figure 4. Comparison of chemical composition for SSA, fly ash, and cement [17,23,33,34,35,36,37,38].
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Figure 5. Triplex diagram of the SiO2, Al2O3, and CaO content for SSA [14,16,18,29,33].
Figure 5. Triplex diagram of the SiO2, Al2O3, and CaO content for SSA [14,16,18,29,33].
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Figure 6. Appearance and microscopic morphology of the SSA [14,15,17,85,86]. Reprinted with permission from Ref. [14]. Copyright 2003 Elsevier Ltd. Reprinted with permission from Ref. [15]. Copyright 2017 Elsevier Ltd. Reprinted with permission from Ref. [17]. Copyright 2017 Taylor & Francis. Reprinted with permission from Ref. [85]. Copyright 2020 Elsevier Ltd. Reprinted with permission from Ref. [86]. Copyright 2019 Elsevier Ltd.
Figure 6. Appearance and microscopic morphology of the SSA [14,15,17,85,86]. Reprinted with permission from Ref. [14]. Copyright 2003 Elsevier Ltd. Reprinted with permission from Ref. [15]. Copyright 2017 Elsevier Ltd. Reprinted with permission from Ref. [17]. Copyright 2017 Taylor & Francis. Reprinted with permission from Ref. [85]. Copyright 2020 Elsevier Ltd. Reprinted with permission from Ref. [86]. Copyright 2019 Elsevier Ltd.
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Figure 7. Effect of SSA on the relative fluidity for mortar [15,18,19,25,84,99,103].
Figure 7. Effect of SSA on the relative fluidity for mortar [15,18,19,25,84,99,103].
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Figure 8. The binders’ content and the corresponding 28d compressive strength of mortars [14,15,16,17,18,19,25,66,112].
Figure 8. The binders’ content and the corresponding 28d compressive strength of mortars [14,15,16,17,18,19,25,66,112].
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Figure 9. Effect of SSA incorporation on flexural strength of mortar [15,19,99,114,118,119,120,121,122]. Note: The points represent the increase or decrease ratio of 28d flexural strength of different SSA mortar compared with that of cement mortar. The different replacement ratio of SSA, different SCMs and different calcined temperature of SSA mortar are also shown next to the point, which are shown as the terms of “a + b(c)”, where “a’’ represents the replacement ratio of SSA (unit: %), “b’’ represents the replacement ratio and type of SCM, “c” represents the calcined temperature (unit: × 100 °C). For example, 20+10Metakaolin from reference [99] means 20% replacement ratio of SSA and 10% replacement ratio of Metakaolin. If there is no other SCM and calcined temperature, only the replacement ratio will be shown, such as “10” in reference [19], which represents the replacement ratio of SSA is 10%.
Figure 9. Effect of SSA incorporation on flexural strength of mortar [15,19,99,114,118,119,120,121,122]. Note: The points represent the increase or decrease ratio of 28d flexural strength of different SSA mortar compared with that of cement mortar. The different replacement ratio of SSA, different SCMs and different calcined temperature of SSA mortar are also shown next to the point, which are shown as the terms of “a + b(c)”, where “a’’ represents the replacement ratio of SSA (unit: %), “b’’ represents the replacement ratio and type of SCM, “c” represents the calcined temperature (unit: × 100 °C). For example, 20+10Metakaolin from reference [99] means 20% replacement ratio of SSA and 10% replacement ratio of Metakaolin. If there is no other SCM and calcined temperature, only the replacement ratio will be shown, such as “10” in reference [19], which represents the replacement ratio of SSA is 10%.
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Figure 10. Effect of SSA incorporation on relative drying shrinkage of mortar. (a) Effect of SSA calcined temperature [124]. (b) Effect of SSA replacement ratio [15,19].
Figure 10. Effect of SSA incorporation on relative drying shrinkage of mortar. (a) Effect of SSA calcined temperature [124]. (b) Effect of SSA replacement ratio [15,19].
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Figure 11. Microstructure of pastes and mortars mixed with SSA [33,85,95,138]. Reprinted with permission from Ref. [32]. Copyright 2008 Elsevier Ltd. Reprinted with permission from Ref. [85]. Copyright 2020 Elsevier Ltd. Reprinted with permission from Ref. [95]. Copyright 2018 Elsevier Ltd. Reprinted with permission from Ref. [138]. Copyright 2015 Taylor & Francis.
Figure 11. Microstructure of pastes and mortars mixed with SSA [33,85,95,138]. Reprinted with permission from Ref. [32]. Copyright 2008 Elsevier Ltd. Reprinted with permission from Ref. [85]. Copyright 2020 Elsevier Ltd. Reprinted with permission from Ref. [95]. Copyright 2018 Elsevier Ltd. Reprinted with permission from Ref. [138]. Copyright 2015 Taylor & Francis.
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Figure 12. Effect of the cement substitution rate of SSA on the mortars porosity [106,124,146].
Figure 12. Effect of the cement substitution rate of SSA on the mortars porosity [106,124,146].
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Table
Table 1. Total heavy metal content of SSA samples (mg/kg) [14,16,17,27,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65].
Table 1. Total heavy metal content of SSA samples (mg/kg) [14,16,17,27,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65].
ElementsSample NumberRangeAverage ValueStandard DeviationsCoefficient of VariationLAGA LimitsSwiss Regulation Limits
Ba5245–16631159.20597.4051.54--
Zn5819.08–71031724.961384.8180.2810,000500
Cu5433.32–8325841.381327.20157.747000250
Cr571.2–2636302.46466.88154.362000250
Pb580.28–4254284.88559.27196.326000250
Hg300.05–111.452.49171.85--
As310.27–27035.5760.58170.30-40
Cd500.1–1308.6319.60227.17205
Ni494–720137.44180.78131.54500250
Sb173.9–18341.4248.19116.35--
Se160.5–576.4913.60209.62--
Table
Table 2. Heavy metal leaching concentrations of SSA samples(mg/L) [17,27,29,32,52,58,60,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84].
Table 2. Heavy metal leaching concentrations of SSA samples(mg/L) [17,27,29,32,52,58,60,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84].
ElementsSample NumberRangeAverage ValueStandard DeviationsCoefficient of VariationTCLP Limits (Us EPA)GB 5085.3-2007 Limits
Ba90.004–0.750.2210.28125.66100100
Zn220.019–17.665.645.5197.6625100
Cu240.008–11.94.0283.8796.1915100
Cr240.009–15.21.5234.24278.37515
Pb270.012–2.430.2620.46176.8655
Hg50.0002–0.20.0410.09216.960.2-
As120.01–0.770.2650.2698.155-
Cd250.009–1.050.1450.29197.0911
Ni140.033–6.520.9861.73175.40255
Table
Table 3. Main oxide content within the SSA of the sample (%) [14,15,16,17,18,19,25,66,112].
Table 3. Main oxide content within the SSA of the sample (%) [14,15,16,17,18,19,25,66,112].
References SiO2Al2O3Fe2O3CaOCaO/SiO2SiO2/Al2O3
[14]50.612.87.211.930.043.95
[15]28.312.518.610.60.372.26
[16]37.89514.50322.6461.8630.052.61
[17]27.7812.218.2310.420.382.28
[17]27.9112.2618.3210.470.382.28
[18]20.814.97.431.31.501.40
[18]30.111.97.125.90.862.53
[18]16.214.78.232.92.031.10
[19]27.2414.4427.356.340.231.89
[25]17.15.115.723.81.393.35
[66]64.623.11.318.60.132.80
[112]28.87.83.921.90.763.69
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Liang, C.; Le, X.; Fang, W.; Zhao, J.; Fang, L.; Hou, S. The Utilization of Recycled Sewage Sludge Ash as a Supplementary Cementitious Material in Mortar: A Review. Sustainability 2022, 14, 4432. https://doi.org/10.3390/su14084432

AMA Style

Liang C, Le X, Fang W, Zhao J, Fang L, Hou S. The Utilization of Recycled Sewage Sludge Ash as a Supplementary Cementitious Material in Mortar: A Review. Sustainability. 2022; 14(8):4432. https://doi.org/10.3390/su14084432

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Liang, Chaofeng, Xinqian Le, Weijiong Fang, Jianming Zhao, Liuji Fang, and Shaodan Hou. 2022. "The Utilization of Recycled Sewage Sludge Ash as a Supplementary Cementitious Material in Mortar: A Review" Sustainability 14, no. 8: 4432. https://doi.org/10.3390/su14084432

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