Utilization of textile effluent wastewater treatment plant sludge as brick material

In the present work, the feasibility of using sludge generated in wastewater treatment plants of textile industry as a partial replacement for clay in the conventional brick manufacturing process is examined. Physico-chemical properties of the sludge and clay were studied. The characteristics of bricks with replacement of sludge (0–50 %) with an increment of 3 % were determined. All the brick samples satisfied the requirements of Indian Standards norms in terms of weight loss on ignition. The bricks with sludge up to 15 % satisfied the prescribed norms for compressive strength and water absorption. Results also showed that the brick weight loss on ignition was mainly attributed to the organic matter content in the sludge being burnt off during the firing process. The characteristics of bricks such as efflorescence, density and weight loss on ignition for bricks with replacement of clayey soil with textile sludge up to 15 % also satisfied the requirements of the Indian Standard. Thus, textile sludge up to 15 % can be effectively added to make brick material.     

Influence of combustion temperature on the performance of sewage sludge ash as a supplementary cementitious material

The potential for using sewage sludge ash (SSA) as a supplementary cementitious material (SCM) has been investigated. Controlled combustion of sewage sludge collected in Croatia from two wastewater treatment plants produced SSA with different characteristics. These were used to substitute for cement in mortar samples. The chemical composition and physical properties of SSA depend on wastewater composition, the sludge treatment process and the combustion temperature. These factors influence the suitability of SSA to be used as a SCM. For three different combustion temperatures (800, 900 and 1000 °C), it was concluded that properties of fresh mortar were not affected while in the hardened state, the most favorable combustion temperature is 900 °C regarding mechanical properties. Regardless of combustion temperature, for all types of SSA used in mortars as cement replacement (up to 30%), the average decrease in both compressive and flexural strength values was less than 8% for every 10% of added SSA. The results presented indicate that using up to 20% replacement of cement by SSA produces mortars that meet the specific technical requirements analyzed in this work.     

Recycling of electrolytic manganese solid waste in autoclaved bricks preparation in China

China has played a dominant role in global electrolytic manganese metal (EMM) production, accounting for over 98 % of the total world capacity since 2008. However, with the rapid development of the EMM industry and depletion of mineral ores, electrolytic manganese solid waste (EMSW) is piling up, so more large-scale landfills are needed. The environmental problems generated by EMSW pose severe threats to soil and ground water, and have become the hot issues in society. The aim is to consume and recycle EMSW, and the primary route is to make autoclaved bricks. However, less attention has been given to the procedure and strength-forming mechanism of EMSW bricks, not to mention the production line of the brick. On the basis of physical and chemical property analysis, the pretreatment process of EMSW was indispensable to solidify/stabilize the heavy metals, such as Mn, Zn, Cd, Pb, etc.. This paper expatiated on the procedure of making EMSW autoclaved bricks, analyzed in detail the strength formed by different cementitious materials with cement properties, and introduced the practical engineering of EMSW autoclaved bricks. The results showed that the pretreatment process with quicklime was effective in solidifying/stabilizing the heavy metals. The compressive strength of EMSW bricks reached 10.05 MPa when quicklime 9 % (w/w) added. Cement may be an ideal cementitious material to create EMSW bricks of high strength in experiments and on the production line. Quicklime and cement used simultaneously produced a lower strength than that when adding cement alone because the gypsum from EMSW and an alkali could generate deleterious effects, e.g., expansion or burst. In the production line of EMSW bricks, an appropriate mix proportion to make high-quality autoclaved bricks was determined: EMSW 30–40 %, cement 10–20 %, and aggregates 40–60 %. The low content of heavy metals tested by toxicity leaching may deduce that the EMSW autoclaved bricks have low environmental risk. However, long-term environmental risk evaluation will be needed, requiring more tests and leaching modeling. Employing EMSW to make high-quality autoclaved bricks may be a promising waste-to-resource strategy.     

Incorporation of sewage sludge in clay brick and its characterization.

This study reports the use of sewage sludge generated from sewage treatment plant (STP) as raw material in a clay brick-making process. The physico-chemical and mineralogical characterization of the sewage sludge and clay were carried out in order to identify the major technological constraints and to define the sludge pretreatment requirements if necessary. Moreover, the effects on processing conditions and/or on changes of typical final characteristics are also evaluated. Bricks were produced with sewage sludge additions ranging from 10 to 40% by dry weight. The texture and finishing of the surface of sludge-amended clay bricks were rather poor. As for the physical and chemical properties, bricks with a sludge content of up to 40 wt.% were capable of meeting the relevant technical standards. However, bricks with more than 30 wt.% sludge addition are not recommended for use since they are brittle and easily broken even when handled gently. A tendency for a general degradation of brick properties with sludge additions was observed due to its refractory nature. Therefore, sludge bricks of this nature are only suitable for use as common bricks, which are normally not exposed to view, because of poor surface finishing.     

Wasteless combined aggregate-coal-fired steam-generator/melting-converter

A method of reprocessing coal sludge and ash into granulate for the building industry in a combined wasteless aggregate-steam-generator/melting-converter was developed and tested. The method involves melting sludge and ash from coal-fired steam-generators of power plants in a melting-converter installed under the steam-generator, with direct sludge drain from the steam generator combustion chamber. The direct drain of sludge into converter allows burnup of coal with high ash levels in the steam-generator without an additional source of ignition (natural gas, heating oil, etc.). Specific to the melting process is the use of a gas-air mixture with direct combustion inside a melt. This feature provides melt bubbling and helps to achieve maximum heat transfer from combustion products to the melt, to improve mixing, to increase rate of chemical reactions and to improve the conditions for burning the carbon residue from the sludge and ash. The "gross" thermal efficiency of the combined aggregate is about 93% and the converter capacity is about 18 t of melt in 100 min. The experimental data for different aspects of the proposed method are presented. The effective ash/charging materials feeding system is also discussed. The reprocessed coal ash and sludge in the form of granules can be used as fillers for concrete and as additives in the production of cement, bricks and other building materials.     

Effect of addition of pond ash and fly ash on properties of ash-clay burnt bricks.

Two industrial solid waste products generated by Indian coal-fired power plants, namely pond ash and fly ash, were used in combination with local clay to develop building bricks. The clay were mixed with the two different ashes in the range 10 to 90 wt.%, hydraulically pressed and fired at 1000 degrees C. The fired products were characterized for various quality properties required for building bricks. The properties of the optimal compositions were compared with conventional red clay bricks including the developed microstructures and the comparative study generally showed that te ash-clay bricks were of superior quality to the conventional products.     

Effects of using arsenic–iron sludge wastes in brick making

The arsenic–iron sludge generated in most of the treatment systems around the world is discharged into the nearest watercourse, which leads to accumulative rise of arsenic and iron concentrations in water. In this study, attempts were made to use the arsenic–iron sludge in making bricks and to analyze the corresponding effects on brick properties. The water treatment plant sludge is extremely close to brick clay in chemical composition. So, the sludge could be a potential substitute for brick clay. This study involved the addition of sludge with ratios 3%, 6%, 9% and 12% of the total weight of sludge–clay mixture. The physical and chemical properties of the produced bricks were then determined and evaluated and compared to control brick made entirely from clay. Results of different tests indicated that the sludge proportion and firing temperature were the two key factors in determining the quality of bricks. The compressive strength of 3%, 6%, 9% and 12% sludge containing brick samples were found to be 14.1 MPa, 15.1 MPa, 9.4 MPa and 7.1 MPa, respectively. These results indicate that the compressive strength of prepared bricks initially increased and then decreased with the increase of sludge proportion. Leaching characteristics of burnt bricks were determined with the variation of pH at a constant temperature. The optimum amount of sludge that could be mixed with clay to produce good bonding of clay–sludge bricks was found to be 6% (safely maximum) by weight.     

Foamed lightweight materials made from mixed scrap metal waste powder and sewage sludge ash.

The porous properties and pozzolanic effects of sewage sludge ash (SSA) make it possible to produce lightweight materials. This study explored the effects of different metallic foaming agents, made from waste aluminium products, on the foaming behaviours and engineering characteristics, as well as the microstructure of sewage sludge ash foamed lightweight materials. The results indicated that aluminium powder and mixed scrap metal waste powder possessed similar chemical compositions. After proper pre-treatment, waste aluminium products proved to be ideal substitutes for metallic foaming agents. Increasing the amount of mixed scrap metal waste by 10-15% compared with aluminium powder would produce a similar foaming ratio and compressive strength. The reaction of the metallic foaming agents mainly produced pores larger than 10 microm, different from the hydration reaction of cement that produced pores smaller than 1 microm mostly. To meet the requirements of the lightweight materials characteristics and the compressive strength, the amount of SSA could be up to 60-80% of the total solids. An adequate amount of aluminium powder is 0.5-0.9% of the total solids. Increasing the fineness of the mixed scrap metal waste powder could effectively reduce the amount required and improve the foaming ratio.     

Synthesis and characterization of drinking water treatment plant sludge-incorporated Portland cement

Kinetic analysis of thermally activated phase transformations in drinking water treatment plant (DWTP) sludge suggests its applicability in the materials of construction. The suggested prediction has already been verified on the sludge-based bricks. The present study deals with incorporating the same sludge in the raw meal for the synthesis of Portland cement clinkers. For this purpose, two raw meals are prepared with varying sludge loadings. The sludge effect on reactivity of the crude mixture is evaluated on the basis of the free lime content sintered at various elevated temperatures. The results of chemical and mineralogical and scanning electron microscopic analyses reveal fine mineralogical contents of Portland clinkers calcined at 1450 and 1500 °C. Moreover, the cements prepared from these clinkers by the introduction of certain proportions of gypsum, depict significant durability. The obtained results elucidate that the studied DWTP sludge-incorporated Portland cement shows considerable potential to be commercialized.     

Recovery of municipal waste incineration bottom ash and water treatment sludge to water permeable pavement materials

Water treatment plant sludge and municipal solid waste incinerator bottom ash are non-hazardous residues, and they can be reprocessed to produce useful materials for city public works. In this study, an effort was endeavored to investigate the properties of water permeable bricks made of water treatment sludge and bottom ash without involving an artificial aggregate step. The water treatment plant sludge was dried and ground, and the bottom ash was subjected to magnetic separation to remove ferrous metals. Both sludge and bottom ash were ground and sieved to a size of <2mm. Different contents of water treatment sludge (70-95% by weight) were mixed with bottom ash and the blocks were molded under a pressure of 110 kg/cm2. Thereafter, the molded blocks were sintered at temperatures of 900-1200 degrees C for 60-360 min. The compressive strength, permeability and water absorption rate of the sintered brick were examined and compared to relevant standards. The amount of bottom ash added in the mixture with water treatment sludge affects both the compressive strength and the permeability of the sintered bricks. The two effects are antonymous as higher bottom ash content will develop a beehive configuration and have more voids in the brick. It is concluded that a 20% weight content of bottom ash under a sintering condition of 1150 degrees C for 360 min can generate a brick with a compressive strength of 256 kg/cm2, a water absorption ratio of 2.78% and a permeability of 0.016 cm/s.     

Use of rubble from building demolition in mortars

Because of increasing waste production and public concerns about the environment, it is desirable to recycle materials from building demolition. If suitably selected, ground, cleaned and sieved in appropriate industrial crushing plants, these materials can be profitably used in concrete. Nevertheless, the presence of masonry instead of concrete rubble is particularly detrimental to the mechanical performance and durability of recycled-aggregate concrete and the same negative effect is detectable when natural sand is replaced by fine recycled aggregate fraction. An alternative use of both masonry rubble and fine recycled material fraction could be in mortars. These could contain either recycled instead of natural sand or powder obtained by bricks crushing as partial cement substitution. In particular, attention is focused on the modification that takes place when either polypropylene or stainless steel fibers are added to these mortars. Polypropylene fibers are added in order to reduce shrinkage of mortars, stainless steel fibers for improving their flexural strength. The combined use of polypropylene fibers and fine recycled material from building demolition could allow the preparation of mortars showing good performance, in particular when coupled with bricks. Furthermore, the combined use of stainless steel fibers and mortars containing brick powder seems to be an effective way to guarantee a high flexural strength.     

Effects of recycled glass substitution on the physical and mechanical properties of clay bricks

In this study, wasted glasses from structural glass walls up to 45 wt.% were added into clay mixtures in brick manufacturing process. Physical and mechanical properties of clay bricks were investigated as functions of the wasted glass content and the firing temperature. The results indicated that with proper amount of wasted glasses and firing temperature, clay bricks with suitable physical and mechanical properties could be obtained. The compressive strength as high as 26–41 MPa and water absorption as low as 2–3% were achieved for bricks containing 15–30 wt.% of glass content and fired at 1100 °C. When the glass waste content was 45 wt.%, apparent porosity and water absorption was rapidly increased.     

Reusability of sewage sludge in clay bricks

Bricks produced from sewage sludge in different compositions were investigated. Results of the tests indicated that the sludge proportion is a key factor in determining the brick quality. Increasing the sludge content results in a decrease in brick shrinkage, bulk density, and compressive strength. Brick weight loss on ignition was mainly due to the contribution of the contained organic matter from the sludge being burnt off during the firing process, as well as inorganic substances found in both clay and sludge. The physical, mechanical, and chemical properties of the bricks that were supplemented with various proportions of dried sludge from 10 to 40wt% and generally complied with the General Specification for Brick as per the Malaysian Standard MS 7.6:1972, which dictates the requirements for clay bricks used in walling in general. A standard leaching test method also showed that the leaching of metals from the bricks is very low.     

Environmental effects of using clay bricks produced with sewage sludge: leachability and toxicity studies

Use of sewage sludge from wastewater treatment plants as a raw material for making clay bricks has been analyzed to be an option to dumping sludges into landfills. This alternative has been shown feasible and interesting due to the high rate of use of ceramic materials in the building sector. However, it meets with some environmental issues and some prejudices on the part of users. This work shows some leachability and toxicity tests (outgassing and offgassing) which demonstrate the environmental compatibility of these ceramic products to be used as building materials and even in deconstruction of the building once its useful life is ended.     

Use of gold mill tailings in making bricks: a feasibility study.

Mill tailings dumps at Kolar Gold Fields, Karnataka, are creating environmental problems. One of the solutions to these problems is to use the mill tailings for some useful purpose. This study examined the possibility of making bricks from the mill tailings with some additives in laboratory experiments. Samples of the mill tailings and the additives were analysed for particle size distribution, Atterberg limits and specific gravity. The plasticity index of the mill tailings being zero, they could not be used directly for making bricks. Therefore some additives that had plasticity or binding properties were mixed with the mill tailings. Ordinary Portland cement, black cotton soils and red soils were selected as additives. Each of the additives was mixed separately with the mill tailings in different proportions by weight and a large number of bricks were prepared using metallic moulds. The bricks were termed as cement-tailings bricks or soil-tailings bricks, depending on the additives used. The cement-tailings bricks were cured for different periods and their corresponding compressive strengths were determined. The bricks with 20% of cement and 14 days of curing were found to be suitable. The soil-tailings bricks were sun-dried and then fired in a furnace at different temperatures. The quality of bricks was assessed in terms of linear shrinkage, water absorption and compressive strength. The cost analysis revealed that cement-tailings bricks would be uneconomical whereas the soil-tailings bricks would be very economical.     

Solidification and recycling of incinerator bottom ash through the addition of colloidal silica (SiO2) solution

The possibility of using incinerator bottom ash as a substitute for natural aggregates was investigated. Rough, porous surface of bottom ash, which diminishes the strength of solidified products, was improved by colloidal silica solution. As a result, a significant increase of mechanical strength was accomplished by a slight amount of silica (<1 wt% to total). Moreover, pozzolanic reaction was induced in initial cement hydration due to the nano-particle size of about 20 nm in colloidal silica solution. Cylindrical specimens and bricks were prepared from bottom ash added to a colloidal silica (SiO2) solution and cement, and then their compressive strengths were evaluated. Cylindrical specimens showed an increase of approximately 60% in compressive strength when colloidal solution containing 4 wt% silica particles was sprayed onto the bottom ash. The strength of bricks containing colloidal silica was in excess of 20 MPa, which meets the requirement of construction materials. Results of leaching tests based on Toxicity Characteristic Leaching Procedure (TCLP) proved that the solidified bottom ash possessed good chemical stability.     

Improvements of nano-SiO2 on sludge/fly ash mortar

Sewage sludge ash has been widely applied to cementitious materials. In this study, in order to determine effects of nano-SiO(2) additives on properties of sludge/fly ash mortar, different amounts of nano-SiO(2) were added to sludge/fly ash mortar specimens to investigate their physical properties and micro-structures. A water-binding ratio of 0.7 was assigned to the mix. Substitution amounts of 0%, 10%, 20%, and 30% of sludge/fly ash (1:1 ratio) were proposed. Moreover, 0%, 1%, 2%, and 3% of nano-SiO(2) was added to the mix. Tests, including SEM and compressive strength, were carried out on mortar specimens cured at 3, 7, and 28 days. Results showed that sludge/fly ash can make the crystals of cement hydration product finer. Moreover, crystals increased after nano-SiO(2) was added. Hence, nano-SiO(2) can improve the effects of sludge/fly ash on the hydration of mortar. Further, due to the low pozzolanic reaction active index of sludge ash, early compressive strengths of sludge/fly ash mortar were decreased. Yet, nano-SiO(2) could help produce hydration crystals, which implies that the addition of nano-SiO(2) to mortar can improve the influence of sludge/fly ash on the development of the early strength of the mortar.     

Hydration and leaching characteristics of cement pastes made from electroplating sludge

The purpose of this study was to investigate the hydration and leaching characteristics of the pastes of belite-rich cements made from electroplating sludge. The compressive strength of the pastes cured for 1, 3, 7, 28, and 90 days was determined, and the condensation of silicate anions in hydrates was examined with the ²⁹Si nuclear magnetic resonance (NMR) technology. The leachabilities of the electroplating sludge and the hardened pastes were studied with the multiple toxicity characteristic leaching procedure (MTCLP) and the tank leaching test (NEN 7345), respectively. The results showed that the electroplating sludge continued to leach heavy metals, including nickel, copper, and zinc, and posed a serious threat to the environment. The belite-rich cement made from the electroplating sludge was abundant in hydraulic β-dicalcium silicate, and it performed well with regard to compressive-strength development when properly blended with ordinary Portland cements. The blended cement containing up to 40% the belite-rich cement can still satisfy the compressive-strength requirements of ASTM standards, and the pastes cured for 90 days had comparable compressive strength to an ordinary Portland cement paste. It was also found that the later hydration reaction of the blended cements was relatively more active, and high fractions of belite-rich cement increased the chain length of silicate hydrates. In addition, by converting the sludge into belite-rich cements, the heavy metals became stable in the hardened cement pastes. This study thus indicates a viable alternative approach to dealing with heavy metal bearing wastes, and the resulting products show good compressive strength and heavy-metal stability.     

海盐工业废渣的综合利用

采用一定的工艺方法,提纯海盐工业废渣中的二水硫酸钙,并制取建筑石膏,用以代替天然石膏生产轻质墙体材料（石膏空心条板）以及水泥添加剂等系列石膏建材制品,经测试,这些石膏建材产品的技术性能指标均达到国家规定的相关标准。     

New technology and application of brick making with coal fly ash

China has ranked first in the coal fly ash emission in the world. The multipurpose use of the fly ash from power plant waste is always an important topic for the Chinese environmental protection, which has drawn the concern of the government, scientific research departments, manufacturing enterprises and industry experts. This paper introduces an experimental research on how to recycle fly ash effectively, a kind of new technology of making bricks by which fly ash content could be amounted to 50–80 %. The article introduces raw materials of fly ash brick, production process and key control points. It introduces how to change the technical parameters of the existing brick-making mechanical device, optimize the parameters combination and improve the device performance. High-content fly ash bricks are manufactured, which selects wet fly ash from power plants, adding aggregate with reasonable ratio and additives with reasonable dosage, and do the experimental research on manufactured products for properties, production technology and selection about technology parameters of production equipment. All indexes of strength grade, freezing-thawing resisting, and other standards of the studied bricks reached the national standards for building materials industry.