An application of blended fly ash and residual rice husk ash for producing green building bricks

The present study investigates the possibility of using a blended class-F fly ash (FA) and residual rice husk ash (RHA) in the production of green building bricks through the application of densified mixture design algorithm (DMDA) in order to provide a new use for solid waste materials. This study uses unground rice husk ash (URHA) as a partial fine aggregate substitution (10–40%) in the studied cementitious mixtures. Solid bricks of 220 × 105 × 60 mm in size were prepared under forming pressure of 25–35 MPa, a curing temperature of 90 °C, and a relative humidity of 50%, for tests that assessed: compressive strength, flexural strength, bulk density, void volume, and water absorption. The test results showed that all brick samples demonstrated excellent properties. Compressive strength and flexural strength ranged, respectively, between 20.2–33 MPa and 5.4–6.9 MPa. Additionally, up to 30% of URHA content, the values of water absorption and void volume ranged, respectively, between 8.8–15.7% and 1.5–2.1%. All of these values not only conformed well to the requirements of the Vietnamese codes but also demonstrated great potential for using a blended FA–RHA in producing green building bricks.     

Potential application of coal-fuel oil ash for the manufacture of building materials

In this paper coal-fuel oil ash has been characterized in terms of leaching behaviour and reactivity against lime and gypsum in hydratory systems for the manufacture of building materials. Its behaviour was also compared to that of coal ash. Metal release was measured in a dynamic leaching test with duration up to 16 days. The results have shown that coal-fuel oil ash behaves very similarly to coal ash. The reactivity of coal-fuel oil ash against lime and gypsum was measured in mixtures containing only lime and in mixtures containing both lime and gypsum. These systems were hydrated at 25 and 40 degrees C under 100% R.H. The results have shown that the main hydration products are the same as those that are usually formed in similar coal ash-based systems. That is, calcium silicate hydrate in coal-fuel oil ash/lime systems and calcium silicate hydrate plus calcium trisulphoaluminate hydrate in coal-fuel oil ash/lime/gypsum systems. From the quantitative point of view, hydration runs showed that the amounts of both chemically combined water and reacted lime measured in the case under investigation are very similar to those found in similar coal ash-based systems. Finally, the measurement of unconfined compressive strength proved that the systems have potentiality for the manufacture of pre-formed building blocks.     

Valorization of olive mill wastewater by its incorporation in building bricks

This investigation deals with the possibility of incorporating the effluent resulting from olive oil extraction activity, known as olive oil mill wastewater (OMW), in the brick-making process. It was undertaken at an important Tunisian brickworks company. In this study, the OMW was mixed with clays following the same brick-making procedure used at the collaborative brickworks in Tunisia. The samples containing OMW were found to be comparable in forming/extrusion performance to a control product that used fresh water. The experimental products produced were tested for their comparative physical properties (volume shrinkage, water absorption, tensile strength of bricks, after firing at 920 degrees C and paste plasticity) in the unfired and fired states against a control representing the commercial product in the same factory. The results showed a significant increase in the volume shrinkage (10%) and the water absorption (12%), while the tensile strength remained constant. The maximum plasticity index value was found when incorporating 23% of OMW. This rate either maintained the physical and mechanical properties of bricks or improved them. The incorporation of OMW in bricks can represent a promising way to valorize this effluent, to rid the environment of a highly polluting wastewater and to save huge and precious amounts of water in a country where water shortage is a serious problem. This newly-prepared material has a double positive impact: it protects the environment and allows water economy.     

Utilization of olive mill sludge in manufacture of lignocellulosic/polypropylene composite

This study evaluated some physical and mechanical properties of injection-moulded polypropylene (PP) composites reinforced with various mixtures of the wood flour (WF) and the olive mill sludge (OMS). Water resistance of the composites improved by the increasing OMS flour content. However, the flexural properties of the composites decreased with increasing OMS flour content. The addition of a coupling agent improved the compatibility between the lignocellulosic material and PP through esterification and thus reduced the water absorption and improved the stability and mechanical properties. The findings obtained in the study showed that the OMS was capable of serving as new reinforcing filler in the manufacturing of thermoplastic polymer composites.     

Sustainable utilization of pre-treated and nano fly ash powder for the development of durable geopolymer mortars

Developments in geopolymer construction are gaining more interest nowadays due to the elimination of cement and the consequent effects such as carbon dioxide emission, greenhouse effect, etc. Although the use of fly ash as a binder in the geopolymer system acts as a key solution for the major hazardous effects like land dumping, soil contamination, groundwater pollution, and respiratory diseases, the slow reactivity of the fly ash resulted in the considerable reduction in the strength. In this paper, a novel pretreatment method was employed on the fly ash binder in terms of thermal and mechanical means. Also, a cost-effective nano fly ash powder was synthesized and used as filler material on the geopolymer system. The efficiency of the fabricated geopolymer mortar was assessed by examining the workability, compressive strength, and resistance against chloride ion penetration. The geopolymer mortars with pre-treated fly ash exhibited a highly workable mix of 130% improved flow rate without adding any superplasticizer. Further, the addition of 1% nano fly ash, exhibited the highest compressive strength of 71.22 MPa, confirmed almost nil chloride ion permeability, and sustained 90% residual strength after immersing in the brine solution for 60 days which explored the development of sustainable and cost-effective geopolymer construction in the marine environment.     

Simultaneous uptake of ammonium and phosphate ions by compounds prepared from paper sludge ash

Al-containing CaO-SiO(2)-H(2)O phases were prepared by hydrothermal treatment of mixtures of paper sludge ash (PSA) with various silica and calcia sources and their properties were determined with particular reference to the simultaneous uptake of ammonium and phosphate ions, which are implicated in the eutrophication of lakes and ponds. After examination of various silica and calcia sources, Ca(OH)(2) and SiO(2) sol were selected as the most appropriate starting materials. Dry milling was found to be superior to wet milling in avoiding contamination from the milling media during mixing. Nine samples with three different Ca/Si ratios and Al(2)O(3) contents were prepared with various mass ratios of Ca(OH)(2), PSA and SiO(2). The chemical compositions of the hydrothermal products of these mixtures moved towards the tieline of CaSiO(3)-PSA, with respect to the starting compositions. The major phase formed in all samples was poorly crystalline C-S-H(I), with hydroxysodalite also formed in the Al-containing mixtures. All the products showed a capacity for the simultaneous uptake of ammonium and phosphate ions. The saturated sorption capacities calculated from the Langmuir equation ranged from 0.9 to 2.4mmol/g for the ammonium ion and from 3.3 to 5.2mmol/g for the phosphate ion. Since the sorption capacities for both ions increased with increasing Ca contents of the product, substitution of Ca(2+) for NH(4)(+) and the formation of calcium phosphate phases such as apatite and brushite by precipitation are thought to be the main sorption mechanisms.     

Beneficiation of pulp and paper mill sludge: production and characterisation of functionalised crystalline nanocellulose

The beneficiation of sludge from pulp and paper mills to produce high-value products such as crystalline nanocellulose will alleviate the challenges associated with conventional methods of sludge disposal, such as landfilling and incineration. In addition, the use of sludge will reduce the consumption of fresh raw materials in the synthesis of nanocellulose which is usually produced from high-purity cellulose pulps. In this study, fibres were cleaned and separated from sludge and then converted to crystalline nanocellulose using ammonium persulphate under optimised oxidative conditions. To extend potential applications of the crystalline nanocellulose produced, the crystalline nanocellulose was functionalised with zinc oxide, silver and hydroxyapatite to prepare crystalline nanocellulose-zinc oxide, crystalline nanocellulose-silver and crystalline nanocellulose-hydroxyapatite nano- and micro-composites powders using the sol–gel process. Transmission electron microscopy, field-emission scanning electron microscopy, X-ray diffraction and thermo-gravimetric analysis were used to investigate the properties of crystalline nanocellulose and functionalised crystalline nanocellulose. The transmission electron microscope and field-emission scanning electron microscope coupled with energy-dispersive X-ray spectroscopy confirmed the synthesis of crystalline nanocellulose, and inorganic nanoparticles. Functionalised samples (crystalline nanocellulose-zinc oxide, crystalline nanocellulose-silver and crystalline nanocellulose-hydroxyapatite) showed better thermal stability than pure crystalline nanocellulose. This implies that the modified inorganic crystalline nanocellulose composites could be used in applications where thermal stability is desirable. The cost of production is economically viable as the raw material cost is cheaper compared to the use of wood pulp.     

Radiological significance of building bricks in Pakistan

Baked clay bricks samples were collected from both urban and rural areas of the North West Frontier Province of Pakistan and natural radioactivity due to 40K, 226Ra and 232Th has been measured in these samples. The specific absorbed dose rates due to natural radioactivity emanating from the walls, floors and ceilings of the typical model rooms made of these building bricks have been calculated applying the mesh size adaptive volume integral methodology. The occupancy factor, representing the weighted average of all the population in the country, was taken to be 0.3 in this study. The values of estimated annual effective dose rates for whole body were found to be 0.38 and 0.35 mSv.y(-1) for the two types of model rooms. These values are smaller than those predicted by UNSCEAR for normal background areas. Thus the building bricks analysed in this study do not pose any significant health problem to the population.     

Development and investigation of cellular light weight bio-briquette ash bricks

The present paper deals with the development of cellular light weight bricks using bio-briquette ash. The necessary physical and chemical tests were conducted on a bio-briquette ash sample to investigate its suitability for the development of bricks. Physico-mechanical, durability and thermal conductivity tests were conducted on cellular light weight bio-briquette ash bricks that fulfilled the requirements of Indian standard. The test results of cellular light weight bio-briquette ash bricks were compared with commercially available fly ash bricks. With reference to fly ash bricks, the cellular light weight bio-briquette ash bricks were found 43 % light in weight, having 13 % higher compressive strength and resulted in 66 % lesser thermal conductivity. A small scale model room (1 m × 1 m × 1 m) made up of fly ash bricks was designed. A similar built form for the cellular light weight bio-briquette ash bricks was also modelled. Both the models were analysed for indoor temperature control and cost. When compared with fly ash model room, cellular light weight bio-briquette ash brick model resulted in a 6 % better indoor temperature control and 29 % cost savings. Thus, the developed cellular light weight bio-briquette ash bricks were found suitable as an alternate construction material for non-load bearing walls.     

Synthesis and characterization of catalysts produced from paper mill sludge. I. Determination Of NOx removal capability

Characteristics and catalytic properties of a series of carbon-based catalysts (CBCs) produced from paper mill sludge were evaluated. The major processes involved in the production of the catalysts were chemical activation, impregnation, pyrolysis, and post pyrolysis rinsing. The porous structure, catalytic activity and thermostability of the catalysts were tailored during the production stage by introducing hetero-atoms (zinc chloride, and ferric nitrate) in the carbon structure. Characterization of the produced CBCs included determination of the surface area, pore size, and pore size distribution (PSD) from standard N₂-adsorption isotherm data. The extent of graphitization and the presence of metal crystals were identified from X-ray diffraction (XRD). The limit of the catalyst gasification was estimated from thermogravimetric analysis (TGA) conducted in an oxidized environment. The NO_x reduction capability of the produced catalysts was evaluated in the presence of carbon monoxide using a fixed bed reactor. The reaction temperature ranged from 300 to 500°C. It was shown that paper mill sludge is an excellent precursor for the production of CBCs with NO_x removal capability of 66–94%. The catalytic capability of the produced CBCs varied according to the method of production, catalyst surface properties (surface area, pore structure, PSD), metal composition and reaction temperature. The highest NO_x removal capacity was observed for the catalytic reactions carried out at 400°C. The mesoporous catalyst produced with a Zn:Fe molar ratio of 1:0.5 exhibited the maximum NO_x removal catalytic activity of 94%.     

Disposal of domestic sludge and sludge ash on volcanic soils

Column leaching experiments were conducted to test the ability of Chilean volcanic soils in retaining the mineral constituents and metals in sewage sludge and sludge ash that were incorporated into the soils. Small or negligible amounts of the total content of Pb, Fe, Cr, Mn, Cd, and Zn (0 to <2%), and more significant amounts of mineral constituents such as Na (7-9%), Ca (7-13%), PO4 (4-10%), and SO4 (39-46%) in the sludge and sludge ash were readily soluble. When they were incorporated on the surface layer of the soils and leached with 12 pore volumes of water over a 3 month period of time, less than 0.1% of the total amount of heavy metals and PO4 in the sludge and sludge ash were collected in the drainage water. Cation exchange selectivity, specific anion adsorption and solubility are the processes that cause the reduction of leaching. The volcanic soils were capable of retaining the mineral constituents, P, and metals in applied sewage sludge and sludge ash and gradually released them as nutrients for plant growth.     

Study on the characteristics of building bricks produced from reservoir sediment

This research investigates the feasibility of building bricks produced from reservoir sediment sintering using various sintering temperatures and clay additions. The experimental results indicate that sintered specimen densification occurred at sintering temperatures of 1050-1100 degrees C. Increasing the sintering temperature decreases the water absorption and increases the shrinkage, density and compressive strength of sintered specimens. The experiments were conducted at a temperature ranged from 1050 to 1150 degrees C with clay addition contents varying from 0% to 20%. All sintered specimens made from reservoir sediment were in compliance with Taiwan building bricks criteria. This means that raw materials for producing building bricks can be replaced with reservoir sediment. The metals concentrations of the leachate from the toxicity characteristics leaching procedure (TCLP) test are all complying with the current regulatory limits. These results confirm the feasibility of using reservoir sediment to produce sintered construction brick.     

Utilization of mixed pond ash in integrated steel plant for manufacturing superior quality bricks

Fly ash (FA) poses serious problems to the industries. Integrated steel plants generate huge quantity of FA from their captive power plants and other furnaces. This ash is generally disposed off in the ash ponds along with other sludges and residues of steel making operations. This changes the constitution of FA and makes the brick manufacturing difficult. This paper has attempted to devise the ways for the use of this mixed ash for manufacturing mixed ash clay bricks successfully. The bricks thus made are superior in structural and aesthetic qualities and portents huge saving in the manufacturing costs with better consumer response.     

Zeolite synthesis from paper sludge ash at low temperature (90 degrees C) with addition of diatomite

Paper sludge ash was partially converted into zeolites by reaction with 3M NaOH solution at 90 degrees C for 24 h. The paper sludge ash had a low abundance of Si and significant Ca content, due to the presence of calcite that was used as a paper filler. Diatomite was added to the NaOH solution to increase its Si content in order to synthesize zeolites with high cation exchange capacity. Diatomite residue was filtered from solution before addition of ash. The original ash without addition of diatomite yielded hydroxysodalite with a cation exchange capacity ca. 50 cmol/kg. Addition of Si to the solution yielded Na-P1 (zeolite-P) with a higher cation exchange capacity (ca. 130 cmol/kg). The observed concentrations of Si and Al in the solution during the reaction explain the crystallization of these two phases. The reaction products were tested for their capacity for PO(4)(3-) removal from solution as a function of Ca(2+) content, suggesting the formation of an insoluble Ca-phosphate salt. The product with Na-P1 exhibits the ability to remove NH(4)(+) as well as PO(4)(3-) from solution in concentrations sufficient for application in water purification. Both NH(4)(+) and PO(4)(3-) removal showed little variation with pH between 5 and 9. Alternative processing methods of zeolite synthesis, including the addition of ash to an unfiltered Si-NaOH solution and addition of a dry ash/diatomite mixture to NaOH solution, were tested. The third process yielded materials with lower cation exchange capacity due to formation of hydroxysodalite. The second process results in a product with relatively high cation exchange capacity, and reduces the number of processing steps necessary for zeolite synthesis.     

Environmental quality of primary paper sludge

The reuse and recycling of waste paper sludge is increasing rapidly as far as the economical and positive environmental benefits are realised. In this study, primary sludge coming from a large production plant, located in the centre of Italy, was collected and the environmental quality of the sludge was assessed through geotechnical, physical and chemical analysis and leaching tests, as required by the Italian regulation on solid waste recovery. The results suggest that primary sludge from paper industry do not represent a major threat for the environment in regard to the heavy metal content. The use of this sludge for in situ applications appears an interesting avenue for an integrated management of waste from the paper industry.     

Test methods for determining the properties of fly ash and of fly ash for use in building materials

The texts presented hereunder are drafts which are submitted for comment, particularly relating to the reference material in section 7.2.2 and 7.4.1. The final recommendations will be drawn up by the committee with respect to the possible comments that should be sent to the Chairman of the committee: Professor Dr.-Ing. K. Wesche, Institute of Building Research, Aachen University of Technology, Schinkelstr. 3, D-5100 Aachen, Germany, before December 31, 1989.     

Sintered coal ash/flux materials for building materials

An Illinois coal ash, which has metals and a large amount of iron, is considered to be an especially difficult waster for disposal. In the process described in this paper, the high iron and metal content is used to create a building material with special properties. The metals are sequestered. The metals allow a process that creates valueadded products, building materials. The products are inexpensively prepared colored, strong, lightweight insulative structural panels. By either sintering in an oven at 725°C or by adding a flux and sintering at 525°C, panels are produced which will not leach metals from the ash. The use of an acid with the fly ash as a flux was investigated in comparison with fly ash control samples. The effects of sintering samples at different temperatures and with or without vacuum were also observed. Properties of the samples, including values for strength, water absorption, insulation, and color, are presented from this study.

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Résumé Une cendre de charbon de l'Illinois, qui a des métaux et une grande quantité de fer, est considérée comme un déchet particulièrement difficile à éliminer. Dans le processus décrit par cette étude, la teneur élevée en fer et en métal est utilisée pour créer un matériau de construction avec des propriétés spéciales. Les métaux sont isolés. Les métaux permettent un processus qui crée de la valeur ajoutée. Les produits sont des panneaux structuraux isolés, colorés, forts et légers qui sont préparés à peu de frais. On produit des panneaux qui ne lixivieront pas les métaux de la cendre par une concrétion dans un four à 725 degrés Celsius, ou bien par une concrétion à 525 degrés Celsius, en ajoutant un flux. L'utilisation d'un acide avec la cendre en l'air comme flux a été étudiée en comparaison avec des échantillons témoins de cendres flottantes dans l'air. On a également observé les effets de concrétionnement des échantillons à différentes températures avec ou sans vide. Les propriétés des échantillons, y compris les indices pour la solidité, l'absorption de l'eau, l'isolation, et la couleur, sont présentées dans cette étude.