Low Quality Fly Ash Research Articles

Enhancing alkali-activated materials with low quality fly ash: A novel mixing approach for robust construction materials

It is highly desirable to use industrial waste materials such as fly ash with high impurities as precursors to produce alkali-activated materials (AAMs) and create sustainable construction materials. A novel, simple and efficient mixing method is introduced in this study for producing robust AAMs from precursors with high impurities. The primary precursor utilized for AAM samples was low-quality fly ash with large particle sizes and high levels of impuri-ties such as unburned carbon and sulfur oxides. In the new mixing procedure, the initial step was to dissolve the precursor in sodium hydroxide solution, followed by introducing sodium silicate solution as the final step. To examine the microstructures and phase changes of the precursor, advanced analytical techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray fluorescence (XRF), and Raman spectroscopy (RS) were utilized. Using RS to monitor the dissolution phase was a novel and particularly beneficial technique discovered in this study, as it helped determine the ideal mixing time based on the results. The new mixing procedure has the potential to considerably enhance various properties of AAMs, including fresh and hardened properties, as well as the durability of AAMs.

Investigating the physical and chemical contribution of ground low-quality fly ash particles to cementitious composites

This work investigates grinding as a potential solution to improve the utilisation of low-quality fly ashes in concrete. Factors contributing to the performance of ground fly ash in cementitious composites were investigated. It was found that grinding significantly crushed large cenosphere particles and increased the specific gravity and surface area of fly ash, which led to a higher filler effect and improved the rate of cement hydration, contributing to strength development. The comparison of strength of quartz-blended pastes and fly ash-blended pastes showed that the pozzolanic reaction of fly ash marginally contributes to strength development. The major influence of ground particles was seen in the region near aggregates. Ground fly ash significantly increased the microhardness of the interfacial transition zone near aggregates. Since this zone has a direct influence on the failure of mortars and concrete, its improvement resulted in a comparable strength of fly ash-blended mortars to the reference ordinary Portland cement mortar.

The Ratio Optimization and Strength Mechanism of Composite Cementitious Material with Low-Quality Fly Ash.

To resolve the limited large-scale methods of disposal of low calcium fly ash with poor activity, based on the double excitation principle, clinker and desulfurized gypsum are used as alkali/salt activators to activate fly ash and slag, avoiding the inconvenience of strong alkali activating fly ash in industry. Firstly, the strength test of a filling body with multiple ratio composite cementing material is carried out, and the weight coefficient of each material to strength is analyzed by grey correlation degree. The composition of the hydration products, microstructure, and pore structure of the filling body was analyzed by X-ray diffractometer, scanning electron microscope, thermogravimetric test, and mercury compression test. The strength mechanism of the cemented body was confirmed. The results show that cemented backfill prepared by composite cementitious material, which contained high content and low-quality fly ash, can meet the strength requirements of subsequent backfill in a mine. The degree of composite cementitious material influence on 7 d strength is slag > desulfurized gypsum > fly ash > clinker; the degree of influence on 28 d strength is: fly ash > slag > desulfurized gypsum > clinker. The main hydration products of the composite cementable material with high content low-quality fly ash are C–S–H gel and ettringite, and the unreacted fly ash particles can still be seen at 28 d. As the curing age grows, the difference in the number of hydration products under different proportioning conditions has a weaker effect on the strength, while the influence of raw materials and product morphology on the pore structure determines the development trend of the strength. Therefore, the threshold pore size can be used to characterize the strength advantages and disadvantages reasonably.

Pathways to Commercialisation for Brown Coal Fly Ash-Based Geopolymer Concrete in Australia

Utilising geopolymer as a construction material has gained institutional and commercial interest over the past decade, due to its favourable emissions profile as an alternative to carbon-intensive Ordinary Portland Cement-based concrete, which currently accounts for around 7% of global carbon emissions. While significant research has been performed into the material properties of geopolymer, the commercialisation of the technology is still in its infancy, and several key barriers require rectification to facilitate more widespread adoption. This article analyses the current state of geopolymer commercialisation, paying particular attention to its commercial application in Australia, and it suggests key research areas, in particular relating to the utilisation of abundant and cheap low-quality fly ash sources such as brown coal-based fly ash, to promote its adoption and build on the momentum gained from the small scale in situ pours of geopolymer concrete. Our analysis indicated that in addition to the barriers relating to material properties, economic, social, and regulatory issues also require further inquiry. Our review also indicated that it is critical to update and improve economic analysis of geopolymer utilisation to forecast future costs of both geopolymer and concrete mixes, which are especially critical in determining any potential financial incentives for the construction industry. Moreover, it is essential to study the social attitudes affecting future geopolymer consumption and to update the regulatory standards governing geopolymer utilisation in Australia, such as the initial steps undertaken by the Low Carbon Living Cooperative Research Centre. Based on this review, it is suggested that solving these key issues would help proliferate geopolymer technology and further aid efforts to create a more environmentally sustainable construction industry.

Properties and Mechanism of Hydration of Fly Ash Belite Cement Prepared from Low-Quality Fly Ash

Fly ash belite cement (FABC) is predominantly composed of α′L-C2S and C12A7. It is prepared from low-grade fly ashes by hydrothermal synthesis and low-temperature calcination methods. The formation, evolution process, and microstructure of FABC hydration productions were studied in this work, and the ultimate aim is to give a theoretical foundation and technological support for the application of the new cementitious material made of low-quality fly ash. The results showed that the optimal amount of gypsum was about 7% of cement by weight. The 3-day and 28-day compressive strength of cement pastes with 7% gypsum was 13.6 and 60.2 MPa, respectively. Meanwhile, the 28-day flexural and compressive strengths of mortars with 7% gypsum were 4.6 and 25.9 MPa, respectively. The early hydration heat release rate of this low-temperature calcined cement was higher compared with that of high-temperature calcined cement as Portland cement. FABC hydration pastes contained mostly C-S-H, ettringite (AFt), unreacted mullite, and quartz. It was significantly different from Portland cement in that no calcium hydroxide [Ca(OH)2] was observed in the hydration products of different ages because all Ca(OH)2 formed in the hydration reaction could react completely to generate AFt. The ratio of harmful pores (d ≥ 50 nm) reached 55.04% after 3-day hydration. However, it decreased to 6.71%, which was lower than that of Portland cement pastes (35.72%) after 28-day hydration. In the later hydration period from 3 to 28 days, the strength developed rapidly, and a compact microstructure appeared in the hardened paste due to the presence of pores less than 20 nm in diameter.

Compressed and stabilized soil blocks with fly ash-based alkali-activated cements

In this study, blocks were manufactured from clay soil and alkali-activated binders. The soils used were classified as A-4 and A7-5 according to ASTM D3282. The binder was produced from fly ash with a high content of unburned material (carbon). Blast furnace slag and lime were used as calcium sources. The physical–mechanical results of the blocks showed that the texture of the soil is a very important parameter for manufacturing this type of compacted soil masonry element, because the soil with the highest sand content (soil A-4) showed a higher dry density, indicating that this property corresponded to a lower percentage of permeable pores, a lower water absorption and an average compressive strength of 17 MPa at an age of 28 days. A life cycle analysis of the blocks was carried out and the results compared to that of the concrete paving blocks and fired clay blocks, which showed that the Global Warming Potential (GWP) can be reduced from 38 to 75%. Of the materials used to prepare the activated blocks, lime and silicate generate the greatest impact. In general, the results show the technical feasibility of manufacturing alternative blocks to traditional pavers with alkaline activation processes by using natural soils as the basic raw material and a low-quality fly ash as precursor.

Performance of FA-based geopolymer concretes exposed to acetic and sulfuric acids

The durability of Portland cement concrete, regardless of its composition, in presence of low-pH solutions is limited due to the dissolution and decomposition of the mineral phases of the hardened cement. For example, sewage systems are critical to public health however concrete sewer pipes deteriorate very quickly due to acid attack. This problem, in addition to affecting the service life of the pipes, increase the costs of maintenance and can be cause of environmental impacts. The use of alkali-activated or hybrid concretes can be considered a viable option from the basis of their chemical resistance. This study describes the acidic attack behaviour of alkali-activated concretes, based on a low-quality fly ash (FA), using as sources of calcium granulated blast furnace slag (GBFS) and Portland cement (OPC), which were incorporated in a 20% by weight proportion. A mixture of sodium silicate and sodium hydroxide was used as the activating solution. The specimens were exposed to solutions of sulfuric acid (H2SO4) and acetic acid (CH3-COOH) at concentration 1 M for 360d. As a reference material, conventional concrete was prepared using general-purpose Portland cement. The effect on the compressive strength and mass loss of each mixture was evaluated. The progress of the degradation by acid action was evaluated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) techniques. The results indicate that alkali-activated concretes show better performance compared with that of OPC concretes with residual strengths at 360 d of exposure between 10 and 20 MPa. In contrast, OPC concrete shows resistance losses of up to 98%. The superior behaviour of alkali-activated concretes is corroborated by the reported lower mass loss (i.e., a maximum of 6%), while that of OPC concrete was up to 19%. In general, gypsum formation is evident in all specimens exposed to H2SO4. In the case of exposure to CH3-COOH, the disappearance of some crystalline products is observed for the alkali-activated concretes. Additionally, it is appreciated the formation of a new crystalline phase, nahcolite. Based in the results, it is possible conclude that this type of alkali-activated binders, (binary and hybrid) based in this type of fly ash, may be used for developing acid-resistant concretes.

Study on Reduction Unburned Carbon Contents in Low Quality Fly Ash from Vietnam

According to Vietnam government establishes additional thermal power plant, processing the coal ash from power plant is urgent issue. This study targeted reducing unburned carbon contents in low quality fly ash to below 6% that according to international standards. As a result, the unburned carbon contents of low quality fly ash was high and irregular as 5.3~23.6%, and it was possible to reduce unburned cabon contents to under 6%, in case of unburned carbon contents below 9.8% ashes using air classification, in case of unburned carbon contents below 23.6% ashes using combined process composed of air classification and electrostatic separation.

Characteristics of geopolymer hybrid concrete in peat water

Geopolymer hybrid is a combination of geopolymer and Ordinary Portland Cement (OPC) or other binders to produce an alternative binder. This type of binder could be used to transform low-quality fly ash into multi-purpose concrete. Ordinary Portland Cement (OPC) concrete subjected to an acidic organic environment such as peatland, is more prone to deterioration in long-term than concrete using the supplementary cementitious material. In this research, the geopolymer was made by activating low-quality fly ash (contains more than 5% carbon) with the alkaline activator. The inclusion of OPC and Portland Cement Composite (PCC) as a fly ash replacement material is intended to promote curing at ambient temperature and immobilization of heavy metals in fly ash. The specimens were cast and cured at ambient temperature up to 28 days. OPC was used as a control mix. Subsequently, the concrete was immersed in fresh peat water in the laboratory up to 28 days. Characteristics of the geopolymer hybrid such as compressive strength, porosity, and leaching were determined. Microstructure analysis, such as SEM-EDX and FTIR, were conducted. Results show that the geopolymer hybrid has a good strength development at early days. At 28 days, there was a reduction of strength and increase of porosity, probably due to the attack of calcium from the OPC concrete. There was a transformation of aluminosilicate gel into C/N-A-S-H that is advantageous for the strength development at the early days. However, a weaker material has formed in the long term that cannot resist further acid attack. It can be concluded that the geopolymer hybrid is a promising binder, but it is essential to design the material appropriately to have better strength, durability and environmental properties in the long term.

Assessing the Durability of Concrete with the Addition of Low Quality Fly Ash

The life span of a structure is basically determined by its durability. Over the course of time, concrete carbonation and corrosion of steel reinforcement lead to weakness in concrete’s structural elements andhence reduce its useful life. The addition of fibers in concrete can act as barrier and delays the activation of these processes. In this study, low quality fly ash was added to concrete to check its effect on the durabilityof concrete. It was found that the addition of low quality fly ash with an activator does have a positive impact on carbonation and reinforcement of corrosion resistance.

Properties and Microstructure of Roller Compacted Concrete With High Volume Low Quality Fly Ash

The properties of roller compacted concrete (RCC) with high dosage low quality fly ash are investigated, including strength, elastic modulus, ultimate tensile strain, drying shrinkage, autogenous deformation and durability, meanwhile the microstructure of the same paste containing low quality fly ash and ground low quality fly ash are studied, too. The properties of RCC containing 60% or more ground fly ash meet the design requirement. The microstructure is also tested by using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry-differential thermal analysis (TG-DTA) and Mercury Intrusion Porosimetry (MIP). The results indicate that ground fly ash plays the role of active component besides the physical filling effect at early age, while after 90 days, the surface of the glass beads is erroded and a lot of calcium silicate hydrate and calcium hydroxide staggered as storied dense structure. Low quality fly ash can accelerate the formation of hydration products, resulting in higher degree of cement hydration and denser microstructure, while the hydration heat in total is reduced. At the age of 90 days, fly ash has significant chemical activity and the properties of RCC will be improved at the later stage.DOI: http://dx.doi.org/10.5755/j01.ms.23.3.16318

Influence of Inertia and Low Active Mineral Admixture on Strength and Microstructure of Cement-Based Materials

Cement-based materials were investigated by comparing the strength and microstructure of pastes and mortar containing limestone powder or low quality fly ash. The compressive strength of the mortar at 28 and 90 d was examined whose microstructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis, and differential thermal analysis (TG-DTA). The results indicated that the strength of mortar decreased with increasing mineral admixtures. The limestone powder mainly acted as inert filler and hardly took part in the chemical reaction. Low quality fly ash may accelerate the formation of hydration products in samples with more chemically bonded water. This further resulted in a higher degree of cement hydration and denser microstructure, while the overall heat of hydration was reduced. At the early stage of hydration, low quality fly ash can be considered as an inert material whereas its reactivity at the later stage became high, especially for ground low quality fly ash.

Sintered Artificial Aggregate with New Correction Raw Materials

Combustion of coal creates a high amount of by-products in heat power plants. The largest share occupies fly ash as solid mineral residuals. Global pressure grows currently for the use of energy by-products. Utilization as a raw material for production of artificial sintered aggregate is one of the ways to make optimal use of even low-quality fly ash. Environmental and economic reasons lead currently to trying to upgrade the technology, which will fully use of the principle of self-sintering process based on content of combustible substances.The amount of combustible substances is today increasing by coal as a primary and finite resource. There is also best way for utilization of industrial wastes that contain a suitable share of combustible substances for ensure the smooth running of sintering.The paper deals with laboratory verification of selected industrial wastes as a correction component in the sintered aggregate production technology. As an alternative raw materials were selected coal tailings, sludge from paper industry, sludge from waste water treatment plant and fly ash from municipal waste incineration plant. The aim of the study was to investigate the effect of corrective components to the quality of the resulting sintered aggregates.

Preparation and characterization of a hybrid alkaline binder based on a fly ash with no commercial value

Alkali-activated Portland fly ash cement (FA/OPC) and alkali activated blast furnace slag-fly ash cement (FA/GBFS) were prepared using 70% of a low quality fly ash (FA). The low quality is associated with a high content of unburned material (loss of ignition of 14.6%). The hybrid cements were activated by the alkaline solution in order to obtain an overall SiO2/Al2O3 molar ratio of 5.0 and 6.0 and unique overall Na2O/SiO2 molar ratio of 0.21. The microstructural characterization of the blended pastes generated in the systems showed the coexistence of amorphous gels C-A-S-H and N-A-S-H gels in the hybrid systems. The addition of OPC or GBFS increases the compressive strength (at 28 days of curing) up to 127% compared with the geopolymer systems based only on FA used in this study. The content of silicates soluble also plays an important role in the reaction products and higher SiO2/Al2O3 lead to obtain higher mechanical performance and denser structure. The results obtained show that these hybrid cements are an effective way for valorization the waste used in this study for the production of high strength and low-carbon footprint cement-type material.

Hydration mechanism of low quality fly ash in cement-based materials

The hydration mechanism of low quality fly ash in cement-based materials was investigated. The hydration heat of the composite cementitious materials was determined by isothermal calorimetry, and the hydration products, quantity, pore structure and morphology were measured by X-ray diffraction (XRD), thermalgravity-differential thermal analysis (TG-DTA), mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM), respectively. The results indicate that grinding could not only improve the physical properties of the low quality fly ash on particle effect, but also improve hydration properties of the cementitious system from various aspects compared with raw low quality fly ash (RLFA). At the early stage of hydration, the low quanlity fly ash acts as almost inert material; but then at the later stage, high chemical activity, especially for ground low quality fly ash (GLFA), could be observed. It can accelerate the formation of hydration products containing more chemical bonded water, resulting in higher degree of cement hydration, thus denser microstructure and more reasonable pore size distribution, but the hydration heat in total is reduced. It can also delay the induction period, but the accelerating period is shortened and there is little influence on the second exothermic peak.

A comparison of hydration properties of cement–low quality fly ash binder and cement–limestone powder binder

The hydration properties of the binder containing low quality fly ash or limestone powder were compared in this study. Isothermal calorimetry was performed to measure the hydration heat of the binders during the first 3 days. Mercury intrusion porosimetry, scanning electron microscope, and thermogravimetry–differential thermal analysis were all used to determine the pore structure and hydration products of paste. The compressive strength of the pastes of age 3, 7, 28, and 90 days was also tested. The results indicate that the ground low quality fly ash can improve the mechanical properties of composite cementitious material and ameliorate the hydration properties and microstructure compared with the inert admixture limestone powder. The chemical activity of low quality fly ash presents gradually and appears high pozzolanic effect at later period, and it can accelerate the generation of hydration products containing more chemically bonded water. This leads to the higher rate of strength growth and cement hydration degree, the more compact microstructure and reasonable pore size distribution. Additionally, low quality fly ash delays the induction period, but shortens the acceleration period, therefore there is no significant influence on the second exothermic peak occurrence time.

Study on Producing Sand-Lime Bricks with Iron Ore Tailings and Phosphogypsum and other Solid Wastes

The paper studied preparing sand-lime bricks by pressure shaping and nature curing, discussed the stimulation effect of compound activators composed of phosphogypsum and lime. The result shows that: when the proportions of raw materials are as follows: 10~15% weight content is iron ore tailings, 3% is phosphogypsum, 5% lime, 5% cement, 40~45% low quality fly ash, and 22~37% chips, the strength of sand-lime bricks produced gets its highest. XRD and SEM are used to characterize its mineral composition and microstructure. The paper also discussed the relationship between structure and performance inside the bricks, and its hydration mechanism.

Application of Ultrafine Fly Ash in Commercial Concrete

Application of ultrafine fly ash grinded by low quality fly ash in commercial concrete was studied, and the studied content included fineness test, mortar strength, concrete strength, admixtures adaptability, impermeability and dry shrinkage. Results show that ultrafine fly ash grinded by low quality fly ash had a very good activity and admixtures adaptability, can greatly improve the strength and impermeability of concrete, and reduce dry shrinkage, and has good applicability in commercial concrete.

Special Issue on Materials Innovations for Sustainable Infrastructure

DOI: 10.1061/(ASCE)MT.1943-5533.0000840Nowadays, the concept of sustainability has gained widespreadacceptanceandawarenessinthetransportationinfrastructureindus-try (Huang and Liu 2011; Mehta 2009). Numerous innovations inpaving materials and construction techniques have been adopted tomeet the challenge of sustainable development (Huang et al. 2012;Miller and Bahia 2009; Aitcin 2007; Van Dam et al. 2011).This special issue contains 16 technical papers in this area, whichcan be divided into the following four categories: (1) recycledmaterials, (2) sustainable materials accommodating climaticchange, (3) pavements for longer service life, and (4) low-energy-consumption materials.Recycled MaterialsRecycling of solid waste materials into paving materials reducesnot only environmental issues associated with waste disposal butalso the demand for virgin asphalt cement or Portland cementbinder, and coarse and fine aggregates, leading to potential costsavings. This is especially important when faced with the ever-growing world population and increasingly dwindling naturalresources. Recycled asphalt pavement (RAP), recycled asphaltshingles (RAS), crumb rubber, and steel slag have been widelyaccepted by state highway agencies and recycled into asphalt pave-ments (Schroeder 1994; Shelburne and DeGroot 1998; Huanget al. 2002, 2005a, 2007, 2010a, b, 2011; Xiao et al. 2007, 2009;Shu et al. 2008, 2012; Zhao et al. 2012, 2013). In addition to thefour types of supplementary cementitious materials (SCMs)—flyash,slag,silicafume,andnaturalpozzolans—manyothermaterialssuch as recycled concrete aggregate (RCA), cement kiln dust(CKD), foundry sand, waste glass, bottom ash, crumb rubber,plastics, ceramics, and even RAP have been recycled into Portlandcement concrete (PCC) materials (Ansari et al. 2000; Naik 2002;Huang et al. 2004, 2005b, 2006b, 2009b, 2013; Li et al.2004a, b). Like SCMs contributing to the properties of hardenedPCC through hydraulic and/or pozzolanic reactions, RAP andRAS can also improve the binding properties of asphalt pavingmaterials through the aged asphalt binder in them, which makesthem more technically and economically beneficial.Thisspecialissuepresentssixtechnicalpapersregardingtheuseof recycled materials such as RAP, RCA, waste phosphorous slag,sludge, low-quality fly ash, and waste ceramic aggregate. Lin et al.investigated the effects of rejuvenator sealer material on aged as-phalt binder through laboratory testing. Their test results show thatrejuvenator can serve as a softening agent, reducing viscosity andcomplex modulus of aged asphalt binder. Chemical analysis indi-cates that addition of rejuvenator can slightly change the fractionsof aged asphalt binder and thus balance its asphaltene-malteneratio. Because rejuvenator is not very common in the recyclingof RAP in asphalt mixtures, this study may shed new light on com-bining rejuvenator with RAP and serve as a booster to incorporatemore RAP in asphalt paving materials.Self-healing is an intrinsic property of asphalt binder and maypotentially be beneficial in improving the properties of recycledasphalt mixtures. Qiu et al. developed three new test methods tosimulatetheself-healingprocessofasphaltbinder,mastic,andmix-ture in the laboratory and investigate the self-heading mechanism.Intheirstudy,theself-healingprocesswastobehypothesizedtothereverse process of cracking, consisting of two phases—crackclosure and strength gain. They also found that the self-healingcapability of asphalt materials is significantly affected by twofactors—temperature and healing time.Qian et al. and Feng et al. both used waste industrial by-productin asphalt mixtures. Qian et al. incorporated phosphorus slag asmineral filler in hot-mix asphalt (HMA) and used multiple charac-terization techniques to assess the feasibility of recycling thisindustrial waste into HMA mixtures. Their test results indicate thatphosphorus slag filler significantly increases the resistance ofHMAs to rutting and moisture damage. Feng et al. attempted torecycle ceramic waste aggregate (CWA) into wearing layer of as-phalt pavement. Their concern is on the thermal effect and the mix-ture performance attributed to adding CWA. Their finite elementmethod (FEM) simulation results show that CWA can reducethe thermal conductivity of asphalt mixtures and subsequently re-duce the temperature gradient of pavement. Basing on the perfor-mance test results, they recommended that less than 40% CWA beadded into asphalt mixtures to replace natural coarse aggregates.Qiao and Chen introduced an innovative chemical admixturecalled mesoporous inorganic polymer (MIP) to improve themechanical properties and early-age shrinkage resistance of re-cycled aggregate concrete (RAC). The properties of RAC are usu-ally compromised because of the addition of RCA, such asincreased shrinkage and creep, reduced strength and modulus,and poor durability. To overcome these inferior properties, a prom-ising chemical admixture, an atomic polymer technology (APT) inthe form of MIP, was added and successfully enhanced themechanical and early-age shrinkage performance of RAC. Com-bined with this technology, more RAC can potentially be madeto promote sustainability in the PCC industry.Yang et al. used river sludge, low-quality fly ash, and glasspowder to produce high-strength ceramsite. They looked into dif-ferent recipes and different fabrication conditions and successfullyproducedhigh-strengthceramsitethatmeetsChinastandards.Their

High-Strength Ceramsite Made with Sludge and Low-Quality Fly Ash

AbstractSludge utilization has become the focus of sludge disposal, and this paper presents a study of using sludge, low-quality fly ash, and other raw materials from the Shanghai region to make high-strength ceramsite. The proportions of the mix and the firing conditions suitable to roast the calcined high-strength sludge ceramsite are discussed. The results show that pure sludge materials alone are not suitable for making high-strength ceramsite. High-strength sludge ceramsite was made with a silt–fly ash–waste glass powder of 60∶35∶5 under a firing system with a preheating temperature of 600°C, a warm-up time of 20 min, a calcination temperature of 1,150°C, and a roasting time of 15 min. The high-strength sludge ceramsite provided particle strength of 7.1 MPa, apparent density of 1,580 kg/m3, and water absorption of 8.2%. All properties were better than the requirements in the national standards. In addition, the high-strength sludge ceramsite provides important environmental and social benefits due t...