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This paper examines the properties of sewage sludge ashes (SSAs) from the incineration of sewage sludge with added limestone for toxic gas treatment. It also evaluates the potential valorization of SSA in cement composites as supplementary cementitious materials (SCMs). The work involves a thorough characterization of four SSAs, including physical, chemical, and mineralogical properties. It also includes assessing the behavior of SSA in water solution through electrical conductivity measurements. The reactivity of ashes was evaluated using the R3 method and mechanical properties. The results revealed that all SSAs present comparable mineralogical and chemical properties, with varying proportions. Major elements such as Ca, Si, Fe, P, and S are predominant in the ashes, with traces of heavy metals. In an aqueous solution, a gradual formation of ettringite was detected only for two SSA. The heavy metal leachability was negligible, confirming that SSA is a non-hazardous waste. Finally, the reactivity and strength activity index assessments revealed a low and slow reactivity of SSA compared to metakaolin or slag. The SSA that favored ettringite formation in aqueous solution presented the lowest compressive strength at 28 days after incorporation in mortar. Despite originating from different incineration sites, these ashes fall under the same category of SCM reactivity. [ABSTRACT FROM AUTHOR]

The use of solid waste such as coal and biomass co-fired fly ashes and sewage sludge fly ash instead of clay and other non-renewable resources to produce lightweight aggregates (LWAs) is conducive to sustainable development. In this study, the effects of co-fired fly ashes, sewage sludge fly ash and quartz sand proportion, sintering temperature and sintering time on the physical properties and microstructure of LWAs are studied by single factor experiment. Experimental results show that the optimal experiment conditions are the raw material ratio of co-fired fly ashes: sewage sludge fly ash: quartz sand = 9: 1: 4, 2 wt% SiC as an expansion agent, and sintering at 1060 °C for 10 min. The LWAs obtained under the above conditions have a bulk density of 0.85 g/cm3, an apparent density of 1.84 g/cm3, a 1-h water absorption of 2.71 %, and a compressive strength of 8.68 MPa, which are in accordance with the GB/T17431.1–2010 standard. Besides, the heavy metal immobilization effect of the LWAs is satisfying, where the heavy metal leaching concentrations meet the standard of GB5085.3–2007. In conclusion, it is feasible to use the raw materials to prepare the LWAs under the above sintering conditions, and the prepared LWAs have high strength and low water absorption. [ABSTRACT FROM AUTHOR]

Sewage sludge ash (SSA), obtained by the incineration of sewage sludge, which is a byproduct of water treatment, could be used as a cement replacement material (CSR) to promote sustainability. SSA characteristics differ due to its different sources, compositions, and incineration methods. On the other hand, extensive investigations have highlighted the CSRs' ability to control alkali–silica reaction (ASR) as a destructive phenomenon, threatening durability. Hence, this study was conducted in order to study the ability of SSA with two finenesses, three replacement levels, and also its ternaries with trass or pumice, as natural pozzolans, to control ASR. The utilized SSA did not meet the requirements of a pozzolan at either finenesses. The results revealed that despite the fact that SSA generally reduced ASR expansion significantly, it only managed to control ASR at 50% replacement level. This was true for both finenesses. Furthermore, ternaries improved resistance against ASR expansion significantly, providing the ability to control ASR at lower replacement levels of SSA. The Si/Ca ratio was the key reason of SSA's ability to control ASR as it contained 1.5 and 2.5 times more SiO2 and Al2O3 than Portland cement respectively, and about one third of its CaO. Scanning electron microscopey (SEM), energy dispersive spectroscopy (EDS), and mapping confirmed that the relative amounts of Si, Al, and Ca in the SSA was crucial. [ABSTRACT FROM AUTHOR]

Copyright of Industrial Water Treatment is the property of CNOOC Tianjin Chemical Research & Design Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Industrial Water Treatment is the property of CNOOC Tianjin Chemical Research & Design Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study aimed to determine the level of immobilization and the mechanism of leaching of heavy metals (Cd, Cr, Cu, Pb and Zn) from self-hardening slurries (SHSs) based on ash from municipal sewage sludge incineration. To mimic the character of the SHS operation in the cut-off wall, the author's leaching method—a filtration leaching test based on the percolation test—was used. In addition, this paper briefly described the factors affecting the level of heavy metal release from cement composites, as well as the chemical mechanisms and physical processes responsible for this phenomenon. This study showed that SHSs immobilized heavy metals at high levels (≥98.18%), and the aqueous extracts from the samples had a high pH (≥12.9%). Statistically significant correlations were obtained between the concentration of some metals and pH (positive correlation for Cr and Zn), test duration (positive correlation for Cd) and the liquid-to-solid ratio (negative correlation for Cd and Cr). For some of the metals tested, it was possible to determine the release mechanisms: dissolution and wash-out for Cd and Pb, and dissolution for Cr and Zn. [ABSTRACT FROM AUTHOR]

This paper examines the properties of sewage sludge ashes (SSAs) from the incineration of sewage sludge with added limestone for toxic gas treatment. It also evaluates the potential valorization of SSA in cement composites as supplementary cementitious materials (SCMs). The work involves a thorough characterization of four SSAs, including physical, chemical, and mineralogical properties. It also includes assessing the behavior of SSA in water solution through electrical conductivity measurements. The reactivity of ashes was evaluated using the R3 method and mechanical properties. The results revealed that all SSAs present comparable mineralogical and chemical properties, with varying proportions. Major elements such as Ca, Si, Fe, P, and S are predominant in the ashes, with traces of heavy metals. In an aqueous solution, a gradual formation of ettringite was detected only for two SSA. The heavy metal leachability was negligible, confirming that SSA is a non-hazardous waste. Finally, the reactivity and strength activity index assessments revealed a low and slow reactivity of SSA compared to metakaolin or slag. The SSA that favored ettringite formation in aqueous solution presented the lowest compressive strength at 28 days after incorporation in mortar. Despite originating from different incineration sites, these ashes fall under the same category of SCM reactivity.

The utilization of calcium carbide residue (CCR) to activate solid wastes can effectively promote sustainable development. This paper explores adding sodium carbonate (Na2CO3) to CCR activators to improve the early reactivity of alkali-activated materials (AAMs) made from sewage sludge ash (SSA). The research focuses on the effects of Na2CO3 on setting, hardening, mechanical strength, and environmental benefits. The findings indicate that Na2CO3 can shorten the paste' hardening time and significantly enhance the early mechanical properties. The introduction of Na2CO3 accelerates the consumption of CCR during the early phases and facilitates the formation of C-(N)-A-S-H gels. Meanwhile, it can significantly reduce the porosity and refine the pore structure. When the dosage reaches 8%, the total intruded pore volume of the sample decreases to 0.15 mL/g. This activation method reduces energy consumption, CO2 emissions, and costs by 69%, 50%, and over 90%, respectively, making it an efficient, eco-friendly approach to AAM production. [ABSTRACT FROM AUTHOR]

The routine dredging of waterways produces huge volumes of sediments. Handling contaminated dredged sediments poses significant and diverse challenges around the world. In recent years, novel and sustainable ex situ remediation technologies for contaminated sediments have been developed and applied. This review article focuses on cement-based binders in stabilizing contaminants through the stabilization/solidification (S/S) technique and the utilization of contaminated sediments as a resource. Through S/S techniques, heavy metals can be solidified and stabilized in dense and durable solid matrices, reducing their permeability and restricting their release into the environment. Industrial by-products like red mud (RM), soda residue (SR), pulverized fly ash (PFA), and alkaline granulated blast furnace slag (GGBS) can immobilize heavy metal ions such as lead, zinc, cadmium, copper, and chromium by precipitation. However, in a strong alkali environment, certain heavy metal ions might dissolve again. To address this, immobilization in low pH media can be achieved using materials like GGBS, metakaolin (MK), and incinerated sewage sludge ash (ISSA). Additionally, heavy metals can be also immobilized through the formation of silicate gels and ettringites during pozzolanic reactions by mechanisms such as adsorption, ion exchanges, and encapsulation. It is foreseeable that, in the future, the scientific community will increasingly turn towards multidisciplinary studies on novel materials, also after an evaluation of the effects on long-term heavy metal stabilization. [ABSTRACT FROM AUTHOR]

[Display omitted] • A broad variety of radionuclides and elements were determined in SSA, APC and DFB. • Mobility of wide spectrum of elements in studied waste was examined. • Relatively high activity of 226Ra in SSA and DFB samples was observed. • The content of majority of elements in samples decrease in samples: SSA > DFB > APC. • High mobility of metalloids and low mobility of metals in SSA and DFB was observed. The research was aimed at providing new knowledge in the field of chemical characteristics of solid waste generated in the process of combustion of sewage sludge in fluidized bed furnaces. The research material consisted of disposed fluidized beds (DFB), sewage sludge ash (SSA) and air pollution control residues (APC) from three Polish installations for the thermal treatment of sewage sludge. Natural radionuclides as well as anthropogenic isotope 137Cs were determined in the tested materials and the migration of a wide spectrum of trace elements to various waste fractions generated in the process of sewage sludge combustion was examined. It was observed that both radioisotopes and most of the trace elements determined accumulate in SSA and DFB, while the APC fraction contains a much smaller amount of them. The exceptions are mercury and selenium, whose volatile compounds migrate to the exhaust gas dedusting system and accumulate in the APC fraction (up to 40 mg/kg and 13 mg/kg, respectively). A potential threat from the 226Ra isotope in SSA is identified in the context of the management of this waste in the production of building materials because the typical activity of 226Ra in SSA collected from areas with very low Ra content in natural environment exceeds 1.5–6 times the activity of this isotope in conventional cement mixtures. When managing SSA and DFB, special attention should be paid to the content of metalloids such as As, B and Se, due to the high content of mobile forms of these elements in the mentioned materials. [ABSTRACT FROM AUTHOR]

The disposal of fly ash (FA) from coal power plants polluting the air, soil, and groundwater is a major environmental concern. Phytoremediation to rehabilitate fly ash dumpsites is a promising alternative but has practical concerns about the disposal of harvested biomass. This study investigated the effect of supplementing fly ash with fresh sewage sludge (FSS), aged sewage sludge, food waste, and compost (COM) to enhance the phytoremediation potential of Napier grass and its subsequent utilization for ethanol production. The highest removal of Mn (1196.12 g ha−1) and Ni (128.06 g ha−1) from FA could be obtained when Napier is grown in the presence of FSS and inorganic fertilizer (NPK). In addition, the highest bioethanol yield (19.31 g L−1) was obtained from Napier grown in fly ash with COM + NPK, thus providing additional economic benefits aside from the remediation process. Given the significant levels of heavy metals present in the pulp and bio-slurry after ethanol production, further research is required in this area to determine the best ways to utilize this waste such as converting it into biochar. Using energy crops as a phytoremediation agent for fly ash dumpsites has the potential to remediate heavy metal contamination and provide additional economic benefits. Napier grass was able to tolerate high concentrations of heavy metals and yield high biomass in fly ash in the presence of organic amendments. The harvested biomass was successfully converted into substrate for bioethanol production using heavy metal-tolerant yeast. This is the first report on the production of ethanol from the phytoremediation biomass of Napier grass. [ABSTRACT FROM AUTHOR]

Struvite crystallization can recover nitrogen and phosphorus simultaneously from various kinds of wastewaters as a slow-release fertilizer. However, the enhancement of the removal efficiency of NH4-N is challenging because the molar concentration of NH4-N is higher than that of PO4-P in many types of sewage including digested sludge filtrate. In this study, phosphorus eluate was recovered from sewage sludge incineration ash (SSA) and applied to the struvite crystallization process to increase the removal efficiency of NH4-N for the digested sludge filtrate. Under acidic conditions, a maximum of 98.4% of phosphorus was eluted from SSA; in alkaline conditions, a maximum of 51.2% was eluted; and in sequential elution conditions with (NaOH+H2SO4), a maximum of 98.0% was eluted. Jar tests were performed by injecting three types of eluates (H2SO4 1 N_elulate, NaOH 1 N_elulate, and (NaOH+H2SO4)_eluate), and PO4-P was stably removed (>86%) under all tested conditions. When the NaOH 1 N_eluate was injected, the NH4-N removal efficiency was highest at 84.4%, followed by 78.4% with the (NaOH+H2SO4)_eluate, and 58.7% with the H2SO4 1 N_eluate at the molar ratio of Mg:P:N of 1.5:1.5:1. In addition, the sequential jar tests were conducted by injecting both the NaOH 1 N_eluate and (NaOH+H2SO4)_eluate. In the pH range of 8.5–9.5, the PO4-P and NH4-N removal efficiencies reached 92.3–94.5% and 97.9–99.1%, respectively. X-ray diffraction analyses confirmed that the majority of the crystal phases were struvite forms. Therefore, the combined application of both the NaOH 1 N_eluate and (NaOH+H2SO4)_eluate was adequate to enhance not only the phosphorus recovery but also the removal efficiencies of PO4-P and NH4-N. SSA recovering PO4-P could be utilized as a new phosphorus source in the struvite crystallization process. [ABSTRACT FROM AUTHOR]

Fly ash generated from municipal waste incineration (MWI) contains various toxic substances, and it has to be properly treated before disposal or reuse. Water washing and thermal pyrolysis can improve the destruction efficiency of PCDD/Fs in fly ash generated from municipal solid waste incinerators. Since sulfur oxides and nitrogen compounds generated by the heating of the sewage sludge poison the catalytic active sites for PCDD/Fs formation on fly ash surface, co-pyrolysis of fly ash with sewage sludge effectively inhibits precursor formation and de novo synthesis reaction, resulting in the great reduction of PCDD/F formation. The results of the pyrolysis at 350 °C show that the PCDD/Fs removal efficiencies based on mass concentration are over 99%. The results at 350 °C of different reaction times show that the reaction time of 10 min is sufficient to reach the European End of Waste criteria (≤ 20 pg TEQ/g) when the ratio of fly ash/sewage sludge is controlled at 1:1. [ABSTRACT FROM AUTHOR]

Legumes have a high demand for phosphorus (P) due to energetically costly biological nitrogen fixation, but they also have effective physiological and morphological strategies for P mobilization. To evaluate the inter- and intraspecific P efficiency of small-grain legumes supplied with different P recycling fertilisers, eight accessions each of alfalfa (Medicago sativa L.) and red clover (Trifolium pratense L.) were cultivated in two pot experiments under greenhouse conditions until the flowering stage. To substantiate the results, some accessions were used in both experiments. Five treatments (no P, triple-superphosphate (TSP), sewage sludge ash (SSA), biowaste compost (compost), and struvite) were considered P sources. In addition to plant P uptake, the soil P pools were analysed in detail. Red clover showed higher yields and nutrient uptakes compared to alfalfa, but intraspecific effects were marginal. The addition of P resulted only partly in an increase in yield, despite the low P content in the soil. While struvite application clearly enhanced the P uptake of the plants in both experiments, SSA application had no effect compared to the control. The same treatment effect occurs with the bio-available soil P contents, which were on average 72.6 mg kg−1 after struvite and 44.3 mg kg−1 after SSA addition. Struvite as a P source was especially effective when applied to red clover. Our study aligns with previous field results and underscores the high potential of P mobilization of small-grain legumes without pronounced inter- or intraspecific differences. While struvite is suitable as a P fertiliser, the application of SSA to legumes is not recommended. [ABSTRACT FROM AUTHOR]

In the pursuit of environmentally and economically sustainable sewage sludge ash (SSA) management methods, researchers often employ laboratory-made SSA (L-SSA) as a substitute for industrial-made SSA (I-SSA) produced in fluidized bed furnaces. To check whether L-SSA is a material that imitates I-SSA well, the fractionation of metals whose presence is a significant problem during SSA management was performed. In addition, the grain distribution, specific surface area, and textural properties of the tested materials were examined. Differences in total Pb and Hg content and mobility of Cu, Ni, Mn, and Zn were observed between I-SSA and L-SSA. Larger particle sizes of L-SSA compared to I-SSA were confirmed, while comparable textural properties and specific surface area of both types of materials were maintained. Based on the results, it was concluded that L-SSA is chemically different compared to I-SSA, and that L-SSA should not be used as a reference in research focused on the design of SSA management methods. Moreover, fractionation of metals was performed in disposed fluidized beds (FBs), which are diverted to non-hazardous waste landfills without prior analysis. It has been proven that studied metals are present in FBs as abundantly as in SSA, while Cu, Mn, and Ni may show higher mobility than in I-SSA. [ABSTRACT FROM AUTHOR]

Recycling and reusing phosphorus in agriculture can reduce the consumption of natural phosphorus resources, which are continuing to shrink. Phosphorus fertilizers made from renewable raw materials (sewage sludge ash, animal bones, dried animal blood) and activated with phosphorus solubilizing microorganisms (Bacillus megaterium, Acidithiobacillus ferrooxidans) offer an alternative to conventional fertilizers. These products should meet consumer and environmental safety standards. In this paper, based on field experiments conducted in northeast Poland, the effects of waste-derived biofertilizers on selected parameters of wheat yield quality are discussed. The study focuses on the technological properties of the grain (hectoliter weight, hardness index, Zeleny index, starch, wet gluten, and protein content), the content of proteogenic amino acids, macro- and micronutrients, and selected toxic elements in the grain. The quality parameters of wheat grain were not affected by the tested biofertilizers applied in P doses up to 35.2 kg ha−1, nor by conventional fertilizers. [ABSTRACT FROM AUTHOR]

The sewage sludge ash (SSA) is characterized as a by-product used in the pavement industry to mitigate the environmental risks, enhance the landfill capacity and conserve the non-renewable resources. This research utilized SSA as a filler substitute in asphalt mastic, and its performance-based properties from low towards high temperatures were evaluated. For this goal, the physical and chemical properties of SSA and rock powder (used as base filler) were determined using BET surface area measurement, X-ray fluorescence, and scanning electron microscopy tests. The performance of base and SSA-modified asphalt mastics in four filler/bitumen weight ratios (0.6, 0.8, 1, and 1.2) was investigated using dynamic shear rheometer, multiple stress creep and recovery, linear amplitude sweep, and bending beam rheometer tests across a wide temperature range. The results indicate that SSA has a higher specific surface area, better bitumen absorption, and lower density compared to the base filler. Additionally, unlike the acidic nature of the base filler, SSA possesses strong basic properties, leading to a stronger chemical bond with bitumen and enhanced resistance to aging, particularly at high temperatures. Moreover, the lower density of SSA escalates the amount of filler per unit volume of the SSA-modified asphalt mastic, leading to the increased stiffness and elasticity. This trend improves resistance to permanent deformation and cracking at medium temperatures, although it has an adverse effect on performance of mastic at low temperatures. Moreover, due to the improved performance of SSA-modified asphalt mastic, this study can contribute to the sustainable development of the pavement industry.

[Display omitted] • Naphthalene is efficiently converted by red mud and sewage sludge ashes in long-term tests. • The support allows to prevent catalysts loss and metal sintering. • Reduced iron is more active than its oxidised form. • Alkali and Alkaline Earth Metals play an important role by hindering coke deposition. • Steam helps to limit coke deposition, while partially oxidising the iron sites. Catalytic tar cracking is a promising technique for hot syngas cleaning unit in gasification plants because it can preserve tars chemical energy, so increasing the syngas heating value. The cost associated with catalyst preparation is a key issue, together with its deactivation induced by coke deposition. Iron is a cheap and frequently used catalyst, which can also be found in some industrial wastes. The study aims to assess the catalytic efficiency for tar cracking of two waste-derived materials (red mud and sewage sludge) having high content of iron. The catalysts were supported on spheres of γ-Al 2 O 3 , and their efficiency was compared to that of a pure iron catalyst. The role of support was investigated by testing pure red mud, with and without the support. A series of long-term tests using naphthalene as tar model compound were carried out under different values of process temperatures (750 °C-800 °C) and steam concentrations (0 %-7.5 %). The waste derived catalysts showed lower hydrogen yields compared to pure iron catalyst, due to their lower content of iron. On the other hand, the conversion efficiencies of all the tested catalysts resulted rather similar, since the Alkali and Alkaline-Earth Metallic species present on the surface of waste-derived catalyst help in preventing coke deposition. The iron oxidation state appears to play an important role, with reduced iron more active than its oxidised form in the tar cracking reactions. This indicates the importance of tuning steam concentration to keep constant the reduced state of iron while limiting coke deposition. [ABSTRACT FROM AUTHOR]

The aim of this research is to evaluate the synergistic effect of the incorporation of spent diatomaceous earth (SDE) from beer filtration on the technological properties of alkaline-activated cements (AACs) based on sewage sludge ash (SSA). Pastes have been manufactured by mixing different amounts of precursor, SSA (30–70% by weight) and SDE (30–70% by weight). The cements were activated using a solution of sodium silicate (50% by weight) and sodium hydroxide (50% by weight NaOH with 8 M) as activator. A liquid/binder (l/b) ratio of 1.2 were used for cements with 30–40% by weight of SSA and 1.0 for binders with 50–70% by weight of SSA. The specimens were cured at room temperature for 7, 28 and 56 days. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for the microstructural characterization of the AACs. The mix proportion of the precursors or the CaO/SiO ratio exerts a substantial impact on the physical, mechanical, and thermal characteristics of the examined AACs. Binders containing 40% by weight SSA and 60% by weight SDE show optimal technological properties, reaching compressive strengths of 32.8 and 36.8 MPa at 28 and 56 days of curing, respectively. This may be due to the formation of different gel types according to SEM analysis: a compact gel phase characterized by a fibrous structure corresponding to the N-(A)-S-H gel surrounding flatter and more uniform zones corresponding to the calcium aluminosilicate gel, C-A-S-H, and a mixed amorphous N,C-A-S-H gel. The results indicated that is possible to produce more sustainable alternative binding materials from the recovery of two types of waste: one from the wastewater treatment, and the other originating from the filtration process in the brewing industry. [ABSTRACT FROM AUTHOR]

Industrial by-products are stored in large quantities in the open, leading to wasted resources and environmental pollution, and the natural environment is similarly faced with phosphate depletion and serious water and soil pollution. This study uses these by-products to produce a new sludge/biomass ash ceramsite that will be used to adsorb nitrogen and phosphorus from wastewater, and solidify heavy metals in the soil while releasing Olsen P. The sludge/biomass ash ceramsites are made using sewage sludge and biomass ash in a certain ratio calcined at high temperatures and modified for the adsorption of nitrogen and phosphorus from wastewater. Sludge/biomass ash ceramsites before and after phosphorus adsorption, biochar and biomass ash were compared to analyze their heavy metal adsorption capacity and potential as phosphate fertilizer. After phosphorus adsorption, the sludge/biomass ash ceramsites released effective phosphorus steadily and rapidly in the soil, with a greater initial release than biochar and biomass ash, and the ceramsites were in a granular form that could be easily recycled. Biochar and biomass residue, due to their surface functional groups, are better at solidifying heavy metals than sludge/biomass ash ceramsites. Biochar, biomass ash and sludge/biomass ash ceramsites significantly reduced the concentrations of Cd, Cu, Pb and Zn in the soil. Correlation analysis demonstrated that there was a synergistic relationship between the increase in soil Olsen P content and the change in pH, with the increase in soil Olsen P content and the increase in pH contributing to heavy metal solidification. [ABSTRACT FROM AUTHOR]

This paper highlights an innovative approach to address the environmental challenges associated with waste management and construction materials. The study presents a new technique for utilising treated sewage sludge in the production of eco-friendly geopolymer mortar. Sewage sludge is a byproduct generated from wastewater treatment plants that poses significant environmental issues due to its disposal problems. Geopolymer mortar, on the other hand, is a sustainable construction material that can be produced by activating industrial waste materials, such as fly ash, using alkaline activators. By integrating machine learning algorithms and data visualisation techniques, this study optimises the mix parameters of geopolymer mortar while simultaneously reducing the negative impact of sewage sludge disposal. The experimental results show that sewage sludge ash can replace fly ash and fine aggregate in 1:3 geopolymer mortar by up to 30% and 20%, respectively, without any toxic or heavy metal residues. The compressive and flexural strength of the sludge-based mortar were comparable to ordinary geopolymer mortar, while water absorption and drying shrinkage were similar to control specimens. This research offers a unique solution to promote sustainability in waste management and construction industry by utilising waste materials, including fly ash and treated sewage sludge, for geopolymer production. [ABSTRACT FROM AUTHOR]

With the significant pace of industrialization, the emission of carbon dioxide (CO2) through cement manufacture, as well as from developed environments, will undoubtedly rise yearly. Biochar as a byproduct of biomass pyrolysis can be utilized in concrete to partially replace cement. Because of its ecological and economic benefits, such as carbon sinks or carbon capture, low thermal conductivity, chemical resistance, and low thermal properties, biochar has risen in popularity in recent years. On the other hand, the possibility of using sludge ash as a cement substitute in the process of making mortar has recently attracted increasing interest. The effectiveness and acceptability of using pine cones as a byproduct of biochar and sludge ash, a byproduct of wastewater treatment, to produce mortar in place of cement are being intensively explored. The integration of biochar and sludge ash into cementitious materials is a possible approach for pollution reduction by replacing Portland cement and reducing collection and disposal in landfills. In order to create high-performance mortar, this study experimentally explores the impacts of combining biochar at an optimal of 6% and sludge ash at optimal of 10%. It analyzes the rheological, mechanical, and durability attributes across curing times of 7 and 28 days in both wet and dry environments, while keeping a constant temperature of 20 °C. As a result, at 28 days, every blend was higher compared to baseline mixture at 7 days. Increases of 19.52% and 13.78%, as well as 24.76% and 21.68%, were seen in the mixtures with 5% and 10% sludge ash (SA) at 28 days compressive strength. With percentage increments for both 7 days and 28 days of 6.6% and 30.9% and 2.2% and 14.1%, the binary blend utilizing BC3SA10 and BC3SA5 significantly outperformed the reference mix. In mortar, the use of biochar could reduce capillary absorption. In addition, its inclusion fastens the rate of hydration of the cement and prevents shrinkage cracks in the mix. The current study concentrates on the significant features of biochar and sludge ash that have an impact on cementitious materials performance. The fresh as well as hardened properties of various concrete and mortar mixes after the replacement of cement with biochar and sludge ash components have been extensively reviewed based on the research results. In a nutshell, biochar and sludge ash materials are an excellent alternative for cement in construction. [ABSTRACT FROM AUTHOR]

The catalytic gasification of sewage sludge was explored using different catalyst particle sizes, bed temperatures, and gasifying agents. Activated carbon and sawdust biochar were used as catalysts in this study. The effects of the porosity of activated carbon on tar adsorption and cracking, and biochar containing alkali and alkaline earth metallic species (AAEMs), which can enhance gasification reactions, were investigated under different conditions. A catalyst bed temperature of 800 °C and particle size of 0.5–1.7 mm showed optimum conditions for increasing H 2 and CO content and decrease CO 2 fraction; however, a higher solid residue (∼38 wt%) was also observed due to the high ash content in sewage sludge. Furthermore, the introduction of steam had a positive effect on the H 2 increment, owing to the presence of inherent AAEMs in the biochar, promoting water gas shift and hydrocarbon steam reforming reactions. The results of this study provide effective measures for using activated carbon and affordable biochar to enhance H 2 production with a parametric effect on the catalyst bed. [Display omitted] • Sewage Sludge gasification was performed over activated carbon and biochar. • Effect of catalysts bed particle size and temperature was investigated. • Particle size of 0.5–1.7 mm and temperature of 800 °C was considered optimum for H 2. • Biochar showed significant water gas shift activity compared to activated carbon. • The presence of AAEMs in biochar can enhance H 2 generation. [ABSTRACT FROM AUTHOR]

• Produced added-value glass-ceramics without using chemical additives. • Predicted the crystallisation behaviour of the glass-ceramics. • Anorthite was formed and transformed into wollastonite in glass-ceramics. • The incorporation of waste glass densified and refined the pore structure. Disposal of waste glass and incinerated sewage sludge ash (ISSA) in landfills is a waste of resources and poses significant environmental risks. This work aims to recycle waste glass and ISSA together to form value-added glass-ceramics. The physical and mechanical properties, leaching behaviour, and microstructure of the glass-ceramics produced with different proportions of waste glass powder (WGP) and ISSA were investigated. Thermodynamic calculations were performed to predict the formation of crystalline phases and the phase transformation involved. The results showed the potential of WGP and ISSA as raw materials in glass-ceramics production. WGP effectively densified the microstructure of the glass-ceramics by forming a viscous phase. As WGP content increased, the total porosity of glass-ceramics decreased whereas the density increased, accompanied by the formed anorthite transforming into wollastonite. The incorporation of WGP densified and refined the pore structure of the glass-ceramics, thereby improving the mechanical properties and reducing the water absorption. The glass-ceramics produced with a 50:50 blend of WGP and ISSA exhibited the highest compressive strength of 43.7 MPa and the lowest water absorption of 0.3 %. All fabricated glass-ceramics exhibited innocuous heavy metal leaching. The co-sintering of ISSA and WGP can produce additive-free glass-ceramics, characterized by reduced energy consumption and notable heavy metal immobilization capacity. These materials hold promise for utilization in construction as building materials. [ABSTRACT FROM AUTHOR]

Copyright of New Building Materials / Xinxing Jianzhu Cailiao is the property of New Building Materials Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The treatment and disposal of sewage sludge ash (SSA) have emerged as crucial environmental concerns. This study delves into the profound impact of substituting SSA for sand in cement mortar, examining fresh and mechanical properties, drying shrinkage, and high-temperature resistance. Analyzing the SSA-modified mortar through X-ray diffraction (XRD) and scanning electron microscopy (SEM), the research reveals that the porous nature of sludge ash marginally influences the hydration rate and degree by adsorbing ions or encapsulating cement particles. While the SSA leaching solution has only a neglectable impact on the hydration rate. The workability is enhanced with the increase of the addition of excess water. Meanwhile, although the presence of excess water indirectly increases the w/c ratio of mortar, mortar with 5 % and 10 % SSA exhibit superior mechanical performance due to denser microstructure. Porous structures of SSA and more excess water in higher SSA content result in the rise of mortar drying shrinkage. When the sintering temperature reaches 800 °C, the high-temperature resistance of mortar with 20 % SSA is greater than that of the control group. The rough surface of SSA effectively fills cracks induced by elevated temperatures and improves the friction reaction, contributing to enhanced performance.

Copyright of Materiały Budowlane is the property of Wydawnictwo SIGMA-NOT and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Two-compartment electrodialytic extraction (2C-ED) is a one-step process for the simultaneous phosphorous extraction and separation of heavy metals from sewage sludge ash (SSA). The process is driven by an applied electric DC field, which can be supplied from renewable sources. The proof-of-concept of the method was conducted in small laboratory cells; however, upscaling to a continuous 2C-ED process, which additionally can treat SSA suspensions at a low liquid-to-solid (L:S) ratio, requires a new design. This paper presents such a new design. In principle, ED consists of two compartments separated by a cation exchange membrane. One compartment contains a suspension of SSA in water and the anode. A cathode is placed in the other compartment. Electrolysis at the anode acidifies the suspension causing the dissolution of phosphorous and heavy metals. The heavy metals are separated from the suspension by electromigration into the catholyte, whereas the dissolved phosphorous remains in the dispersion solution. In the new design, the SSA was suspended in a tube-shaped reactor with the cation exchange membrane covering the outside. The reactor was placed in a container with the catholyte. Periodically turning off the reactor kept SSA in suspension even at a low L:S ratio without corners and pockets where the SSA otherwise tends to settle. Five 2C-ED experiments were conducted with 1.5 to 3 kg SSA at varying currents and durations. Up to 89% P was extracted. The extracted P was concentrated in the dispersion solution of the SSA suspension, where the obtained P-related concentrations of heavy metals were far below the limiting values for spreading on agricultural land. The experiments underlined that treating the SSA in a suspension with a low L:S ratio is advantageous. A comparison to previous laboratory experiments in small cells treating 50 g SSA shows a significantly more efficient use of the applied current in the new reactor setup. Thus, the new reactor design for 2C-ED fulfilled the set criteria for the operation and did additionally result in a higher efficiency than the laboratory setups, i.e., the design can be the first step towards an upscaling. [ABSTRACT FROM AUTHOR]

This review provides an overview of methods to extract valuable resources from the ash fractions of sewage sludge, municipal solid waste, and wood biomass combustion. The resources addressed here include critical raw materials, such as phosphorus, base and precious metals, and rare earth elements for which it is increasingly important to tap into secondary sources in addition to the mining of primary raw materials. The extraction technologies prioritized in this review are based on recycled acids or excess renewable energy to achieve an optimum environmental profile for the extracted resources and provide benefits in the form of local industrial symbioses. The extraction methods cover all scarce and valuable chemical elements contained in the ashes above certain concentration limits. Another important part of this review is defining potential applications for the mineral residues remaining after extraction. Therefore, the aim of this review is to combine the knowledge of resource extraction technology from ashes with possible applications of mineral residues in construction and related sectors to fully close material cycle loops. [ABSTRACT FROM AUTHOR]

Two sewage sludge ash (SSA) samples were analyzed using X-ray fluorescence spectrometry and X-ray diffractometry, and a chemical mass balance method was employed to estimate the contribution of soil-derived components. Plagioclase in the SSA samples, which originates only from soil, was used as a fingerprint for the crystalline phase to determine the relative contribution of soil components in each sample. Specifically, an average of 18% of total mass was found to be plagioclase in soil samples collected at 35 sites in the drainage collection district, and this value was used to estimate the contributions of other SSA soil components. The contributions of the soil to SSA A and B were approximately 50 and 80 mass%, respectively. The crystalline phases of the two SSAs were found to consist of different components such as phosphate crystalline phases. These results suggest that the coagulant composition may influence SSA content, including the soil-derived components. [ABSTRACT FROM AUTHOR]

In the pursuit of environmentally and economically sustainable sewage sludge ash (SSA) management methods, researchers often employ laboratory-made SSA (L-SSA) as a substitute for industrial-made SSA (I-SSA) produced in fluidized bed furnaces. To check whether L-SSA is a material that imitates I-SSA well, the fractionation of metals whose presence is a significant problem during SSA management was performed. In addition, the grain distribution, specific surface area, and textural properties of the tested materials were examined. Differences in total Pb and Hg content and mobility of Cu, Ni, Mn, and Zn were observed between I-SSA and L-SSA. Larger particle sizes of L-SSA compared to I-SSA were confirmed, while comparable textural properties and specific surface area of both types of materials were maintained. Based on the results, it was concluded that L-SSA is chemically different compared to I-SSA, and that L-SSA should not be used as a reference in research focused on the design of SSA management methods. Moreover, fractionation of metals was performed in disposed fluidized beds (FBs), which are diverted to non-hazardous waste landfills without prior analysis. It has been proven that studied metals are present in FBs as abundantly as in SSA, while Cu, Mn, and Ni may show higher mobility than in I-SSA.

The quantity of carbon dioxide gas released during the manufacturing and acquisition of raw ingredients determines the sustainability of concrete. Industrial garbage dumping is a critical difficulty that humanity is experiencing because of globalization and the increasing population. Through the efficient use of industrial by products, efforts are being undertaken to lower carbon discharges in the concreting process. It has been recommended by sustainable development goals and standards to use byproducts that have lower embodied energy and carbon emissions. Ash from sewage sludge demonstrates its suitability for use in concrete. However, a compressive assessment is needed to determine the past, present, and future research aspects of using sewage sludge ash (SSA) as a construction material. Therefore, this research is carried out on using SSA as a construction material. All the essential properties such as the physical and chemical properties of SSA, its effect on durability properties, and morphology structure study are the main aspect of this review (Part II). The analysis also highlights the research gap for upcoming exploration which further improved its performance.

Abstract The lack of adequate space for sewage sludge disposal has become a significant challenge in many countries. Landfilling and using sewage sludge as fertilizer in agricultural lands are the main methods for disposal. However, these methods can result in soil and groundwater contamination as well as heavy metal and microbial pollution in soil. An alternative disposal method is using sewage sludge ash (SSA) in concrete production. If the sludge ash is reactive, it can replace a portion of cement in concrete; otherwise, it can be used as a filler. In the present study, X-ray fluorescence (XRF) experiments were conducted to determine the elemental composition of sewage sludge. Then, the sewage sludge was incinerated, and XRF and X-ray diffraction (XRD) tests were performed on the resulting sewage sludge ash. The ash was utilized in different proportions in the mortar and concrete specimens, and compressive strength tests were conducted on the resulting specimens. The results indicate that using 20% SSA instead of cement resulted in a 25% reduction in compressive strength in concrete specimens. However, the combination of 10% silica fume and 10% SSA was the optimal combination to compensate for the reduction in compressive strength caused using SSA.

The study aims to increase the efficiency of mortar mixes and improve their necessary qualities such as strength, density, and durability by using wastepaper as a cement substitute in the form of wastepaper sludge ash (WPSA). Mortars with 20, 25, and 30% cement replacement were tested. Due to less use of cement and greater usage of WPSA, CO2 and SO2 emissions can be reduced. The chemical properties of WPSA were compared to those of Ordinary Portland Cement (OPC). Testing showed that WPSA had similar cementitious properties. Results demonstrate the potential applications of this mortar in a variety of settings where increased toughness and equivalent characteristics are needed while still preserving the environment. [ABSTRACT FROM AUTHOR]

The restrictions on carbon dioxide emissions introduced by the European Union encourage experimental work on new-generation materials containing smaller amounts of clinker. At present, silica fly ashes from the combustion of hard coal are widely used in the technology of cement and concrete in Europe and Poland. This research aims to assess the physical and chemical properties of fly ashes from the thermal treatment of sewage sludge for use in concrete technology in relation to applicable standards and determine their impact on the natural environment. The established concentrations of heavy metals are below the maximum values required when discharging sewage into the ground or waters and also meet the necessary leaching limits when inert waste is allowed to be landfilled and on substances particularly harmful to the aquatic environment. On this basis, it was found that the migration of heavy metals from concrete with the addition of ashes to the water environment is insignificant and should not be a major problem. In addition, the tests showed that the activity index did not exceed the limit value. [ABSTRACT FROM AUTHOR]

Efficient utilization of natural resources and possible valorization of solid waste materials such as sewage sludge into secondary materials via thermal conversion and simultaneously recovering energy is vital for sustainable development. The continuous increase in metropolises leads to an enormous production of wet sewage sludge, which creates major environmental and technical issues. In this paper, the samples of sewage sludge from Astana's waste water treatment plant are analyzed for their thermochemical properties, followed by thermogravimetric and kinetic analysis using the Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose methods. Overall, the calorific value of sewage sludge sample was 18.87 MJ/kg and was comparable to that of the bituminous coal samples. The activation energy varied from 140 to 410 kJ/mol with changing conversion from 0.1 to 0.7. Further, mono-combustion and co-combustion experiments of the sewage sludge with high ash bituminous coal were conducted using the laboratory scale bubbling fluidized bed rig, respectively. The difference in NOx emissions between mono-combustion of sewage sludge and co-combustion with coal were at around 150 ppm, while this value for SO2 was similar in average, but fluctuates between 150 and 350 ppm. Overall, the findings of this study will be useful in developing a co-combustion technology for a sustainable disposal of municipal sewage sludge. [ABSTRACT FROM AUTHOR]

The amount of sewage sludge from wastewater treatment plants is continuously increasing and becoming a serious issue for environment. Therefore, the valorisation of sewage sludge in sectors such as the construction field where there is high demand for naturel resources would be great for the environment. The present work reports the possibility of using sewage sludge ash as substitute for part of cement in mortars. The cement was mixed at various percentages of sewage sludge ash: 0% (as control mortar), 10%, 20% and 30% of the cement's weight. Several properties have been tested at various curing ages (2, 7 and 28 days) and compared with control samples: mechanical properties including flexural and compressive strengths, and physical properties namely the dry bulk density, the water absorption and the apparent porosity. The obtained results have revealed that both physical and mechanical properties of mortar was influenced by the ratio of sewage sludge ash which can be used as a substitute of part of the cement in mortar. Flexural and compressive strengths increased over time for all the samples of mortar. The substitution can be as high as 30% while maintaining a compressive strength within the standard requirements at 28 days. Also the use of up to 30% of the weight of cement in sewage sludge ash provides lower dry bulk densities, higher both water absorption and higher apparent porosity than control mortars. [ABSTRACT FROM AUTHOR]

Various nutrient recycling technologies are currently under development in order to alleviate the dependency of non-renewable raw material for the production of mineral phosphorus fertilizers commonly used in agriculture. The resulting products, such as struvites and ashes, need to be assessed for their application as so-called recycling-derived fertilizers (RDFs) in the agricultural sector prior to commercialization. Here, we conducted a short-term (54 days) trial to investigate the impact of different phosphorus fertilizers on plant growth and the soil P cycling microbiota. Lolium perenne was grown with application of superphosphate (SP) as inorganic fertilizer, two ashes (poultry litter ash (PLA) and sewage sludge ash (SSA)), and two struvites (municipal wastewater struvite (MWS) and commercial CrystalGreen® (CGS)) applied at 20 and 60 kg P ha−1 in four replicates. A P-free control (SP0) was also included in the trial. Struvite application increased plant dry weights, and available P acid phosphatase activity was significantly improved for struvites at the high P application rate. The ash RDFs showed a liming effect at 60 kg P ha−1, and PLA60 negatively affected acid phosphatase activity, while PLA20 had significantly lower phoD copy numbers. P mobilization from phosphonates and phytates was not affected. TCP solubilization was negatively affected by mineral SP fertilizer application at both P concentrations. The bacterial (16S and phoD) communities were only marginally affected by the tested P fertilizers. Overall, struvites appeared to be a suitable substitute for superphosphate fertilization for Irish L. perenne pastures. [ABSTRACT FROM AUTHOR]

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The rapid, high increase in production costs and prices of mineral fertilizers leads to a reduction in their use by farmers, while fertilizer manufacturers consider the use of alternative raw materials and reducing the energy consumption of fertilizer production processes. Given these circumstances, special attention is warranted for suspension fertilizers. The manufacturing of suspension fertilizers is simplified and less energy intensive in comparison with solid fertilizers. This is achieved by omitting certain production stages such as granulation, drying, sifting, which usually contribute to more than half of the production costs. This paper presents the production procedure of suspension fertilizers tailored for cabbage cultivation, utilizing alternative raw materials such as sewage sludge ash and poultry litter ash. The final products are thoroughly characterized. The obtained fertilizers were rich in main nutrients (ranging from 23.38% to 30.60% NPK) as along with secondary nutrients and micronutrients. Moreover, they adhere to the stipulated standards concerning heavy metal content as outlined in the European Fertilizer Regulation. A distribution analysis has showed that suspension fertilizers contain nutrients in both liquid and solid phases. This arrangement facilitates their easy availability for plants and subsequent release upon dissolution in soil conditions. To assess process consistency, the production of the most promising fertilizer was upscaled. A preliminary technological and economic analysis was also conducted. The method of producing suspension fertilizers using alternative raw materials is a simple waste management solution offering nutrient recycling with the principles of circular economy. This approach not only encourages nutrient recycling but also curtails reliance on imported raw materials. [ABSTRACT FROM AUTHOR]

CO2 emission limits introduced by the European Union are encouraging works on new-generation materials with reduced clinker content. Currently, fumed silica from hard coal combustion is used in cement and concrete technology in Europe and Poland. Its wide application depends mainly on its chemical and phase composition, especially the reactivity of pozzolanic acids and its high fineness similar to cement Many authors studied the influence of fly ashes from hard coal combustion, in accordance with PN-EN 450-1 and 450-2, on the properties of concrete, including the course of the carbonation process. There are no studies in the literature involving ashes from sewage sludge. The objective of the research is to assess the course of carbonation of concrete produced on the basis of fly ash from the thermal transformation of sewage sludge over time and to describe this phenomenon in a mathematical form. An additional objective was to analyze the physicochemical composition of sludge ash in accordance with the requirements of EN 450-1, ASTM-C618-03. In addition, this study also demonstrated the possibility of producing fly ash-modified standard concrete through the thermal treatment of sewage sludge. The average compressive strengths of Krakow gray concrete after curing for 28, 56, 90, and 365 days were 50.1 MPa, 50.6 MPa, 50.8 MPa, and 61.9 MPa, respectively. On the one hand, the additives introduced in the concrete mixture accelerate the carbonation process by shifting the carbonation front deep into the concrete and, on the other hand, create a denser microstructure In all cases, the largest increase in carbonation depth was observed up to the 56th day of the study, while the smallest increase was observed between 90 and 180 days. The diffusivity decreases and the rate of carbonation is reduced. The determined regression coefficients of hyperbolic models indicate the proper adjustment of the adopted hyperbolic model to the results of laboratory tests under accelerated carbonation conditions (R = 0.85–0.99), regardless of the content of fly ash from sewage sludge in ordinary concrete samples. [ABSTRACT FROM AUTHOR]

The lack of adequate space for sewage sludge disposal has become a significant challenge in many countries. Landfilling and using sewage sludge as fertilizer in agricultural lands are the main methods for disposal. However, these methods can result in soil and groundwater contamination as well as heavy metal and microbial pollution in soil. An alternative disposal method is using sewage sludge ash (SSA) in concrete production. If the sludge ash is reactive, it can replace a portion of cement in concrete; otherwise, it can be used as a filler. In the present study, X-ray fluorescence (XRF) experiments were conducted to determine the elemental composition of sewage sludge. Then, the sewage sludge was incinerated, and XRF and X-ray diffraction (XRD) tests were performed on the resulting sewage sludge ash. The ash was utilized in different proportions in the mortar and concrete specimens, and compressive strength tests were conducted on the resulting specimens. The results indicate that using 20% SSA instead of cement resulted in a 25% reduction in compressive strength in concrete specimens. However, the combination of 10% silica fume and 10% SSA was the optimal combination to compensate for the reduction in compressive strength caused using SSA. [ABSTRACT FROM AUTHOR]

Growing concern over mineral resources supply forces us to search for alternative sources of Phosphorus. The possibility to recover phosphorus from incinerated sewage sludge ashes appears to be an important aspect in anthropogenic phosphorus cycle and sustainable economy. To make phosphorus recovery efficient it is important to learn the chemical and mineral composition of ash and phosphorus speciation. The phosphorus content in the ash was over 7%, what corresponds to medium rich phosphorus ores. The main phosphorus rich mineral phases were phosphate minerals. The most widespread was tri-calcium phosphate Whitlockite with various Fe, Mg and Ca proportions. In minority Fe–PO4 and Mg–PO4 were detected. Whitlockite commonly overgrown with hematite, influences negatively mineral solubility and thus recovery potential and indicates low bioavailability of phosphorus. Considerable amount of phosphorus was found in the low crystalline matrix where phosphorus content was around 10 wt% however low crystallinity and dispersed phosphorus also does not strengthen the potential to recover this element. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new environment-friendly reagent was used as a phosphorus extractant. • Using waste eggshells as an external calcium source, achieved dual utilization of waste. • Up to 96.05% phosphorus recovery was recorded with optimal conditions. • The O–H, C–H and C=O contributed mainly to the release of phosphorus. Phosphorus (P) is an integral mineral nutrient for the growth of plants and animals. As the increasing population worldwide, the demand for P resources keeps increasing. Therefore, it is necessary to recover P from secondary resources. Unlike conventional P recovery processes, this work focused on the recovery of P from incinerated sewage sludge ash (ISSA) using electrodialysis as the main technology coupled with plant extractants. In this study, Amaranthus and hydrolyzed polymaleic anhydride (HPMA) were used as P extractants, investigating the effects of HPMA concentration and pH of the compound agent on the migration of P and heavy metals from ISSA. The results showed that the concentration of HPMA and pH of the compound agent had a significant influence on the mobility of P and heavy metals. Meanwhile, the impacts of eggshell additions and voltage on the recovery efficiency of P was also studied by using waste eggshells as calcium sources. We found that when eggshells were added at 10 g/L and the voltage was 10 V, the recovery efficiency of P reached 96.05%. Moreover, XRD patterns revealed that the mineral phase of recovered P-containing products was predominantly hydroxyapatite, which had good environmental benefits. Generally, the favorable results have been achieved in the recovery efficiency of P and has practical implications for P recovery from ISSA. [ABSTRACT FROM AUTHOR]

The activity of sewage sludge ash (SSA) is not high; ground granulated blast slag (GGBS) has a high calcium oxide content that can accelerate polymerization rates and exhibit better mechanical performance. In order to improve the engineering application of SSA–GGBS geopolymer, it is necessary to conduct a comprehensive evaluation of its performance and benefits. In this study, the fresh properties, mechanical performance and benefits of geopolymer mortar with different SSA/GGBS, modulus and Na2O contents were studied. Taking the economic and environmental benefits, working performance and mechanical performance of mortar as evaluation indexes, the entropy weight TOPSIS (Technique for Order Performance by Similarity to Ideal Solution) comprehensive evaluation method is used to evaluate the geopolymer mortar with different proportions. The results show that as SSA/GGBS increases, the workability of mortar decreases, the setting time first increases and then decreases, and the compressive strength and flexural strength decrease. By appropriately increasing the modulus, the workability of the mortar decreases and more silicates are introduced, resulting in increased strength in the later stage. By appropriately increasing the Na2O content, the volcanic ash activity of SSA and GGBS is better stimulated, the polymerization reaction is accelerated, and the early strength increases. The highest I c (integrated cost index, C t f c 28 ) of geopolymer mortar is 33.95 CNY/m3/MPa, and the lowest is 16.21 CNY/m3/MPa, which is at least 41.57% higher than that of ordinary Portland cement (OPC). The minimum I e (embodied CO2 index, E c f c 28 ) is 6.24 kg/m3/MPa, rising up to 14.15 kg/m3/MPa, which is at least 21.39% lower than that of OPC. The optimal mix ratio is a water–cement ratio of 0.4, a cement–sand ratio of 1.0, SSA/GGBS of 2/8, a modulus content of 1.4, and an Na2O content of 10%. [ABSTRACT FROM AUTHOR]