Reducing Heavy Metal Element from Coal Bottom Ash by Using Citric Acid Leaching Treatment

Coal ash is the residue that is produced during coal combustion for instance fly ash, bottom ash or boiler slag which was primarily produced from the combustion of coal. With growth in coal burning power station, huge amount of coal bottom ash (CBA) considered as hazardous material which are normally disposed in an on-site disposal system without any commercialization purpose. Previous researchers have studied the extraction of silica from agricultural wastes such as palm ash and rice husk ash (RHA) and CBA by using leaching treatment method. In this study, the weaker acid, citric acid solution was used to replace the strong acid in leaching treatment process. Result showed that the heavy metal content such as Copper (Cu), Zinc (Zn) and Lead (Pb) can be decrease. Meanwhile the silica can be extracted up to 44% from coal bottom ash using citric acid leaching treatment under the optimum reaction time of 60 minutes with solution temperature of 60°C and concentration of citric acid more than 2%

Impact of Portland Cement Content on Alkali Activated Bottom Ash

This study explores the behavior of blended mortars of low reactive bottom ashes (BA) and ordinary Portland cement (OPC) in an alkaline solution. Mortar mixtures incorporating OPC with different replacement levels (0% to 30% mass) were studied. Isothermal conduction calorimetric analysis was studied and 28-and 60-day mechanical strength values were found. SEM images was used to identifies porosity structures at 28-day. Water absorption was also investigated. The results revealed different behaviors to low (OPC 2.5 and OPC 5) and moderated (OPC 10 and OPC 30) OPC content. Increase in percentage of Portland accelerated hydration kinetics. There is a second peak formation for moderated OPC content, associated with C-A-S-H gel formation. The partial replacement of bottom ash by OPC tend to reduce the absorption. There is a slower initial water absorption to low OPC content. This behavior is due the higher unreacted BA content, that works as a filler. Otherwise, the increase of water absorption for OPC content is due to the coexistence of Portland cement hydrates and alkali activated reactions

Análisis de propiedades del transporte de humedad en bloques de hormigón

The moisture absorption properties in the concrete blocks have a significant influence on the performance of the penetration of rainwater. Knowledge of these properties is necessary to have technical information that allows the construction of walls with long life. In this paper we conducted a comparative analysis of two structural concrete blocks in relation to their physical properties and moisture transport: open porosity, specific mass and the initial rate of absorption (IRA), the total absorption and uptake versus time, obtaining the sorptivity as code for measuring the absorption accurate and reliable. The results obtained show that the sorptivity in the case of concrete block D2 is not applicable and presents the absorption average curve versus time as a characterization parameter with great potential, once can be observed the behavior of the blocks from the initial time to saturation, showing the characteristics between the different block types analyzed.Las propiedades de absorción de humedad de los bloques de hormigón tienen influencias significativas en el comportamiento a la penetración de agua de lluvia. El conocimiento de estas propiedades es necesario para poder contar con información técnica que permita la construcción de paredes con vida útil prolongada. En el presente articulo se realizó un análisis comparativo de dos bloques de hormigón estructurales en relación a sus propiedades físicas y de transporte de humedad: porosidad abierta, masa especifica así como la tasa inicial de absorción (IRA), absorción total y la absorción en función del tiempo, con la obtención de la sorptividad como código de medición preciso y confiable. Los resultados mostraron que la sorptividad no es aplicable en el caso de los bloques de hormigón D2 y se presenta la curva media de absorción en función del tiempo como un nuevo parámetro de caracterización que permite analizar el comportamiento y las peculiaridades de los bloques desde el instante inicial hasta la saturación

Study of a cement with low environmental impact from sulfoaluminate clinker and phosphogypsum

A possibilidade de utilizar resíduos industriais como matéria-prima de produtos para a construção civil vem a cada ano ganhando mais importância no aspecto ambiental e tem também criado novos desafios tecnológicos. Além de evitar a degradação das áreas onde os resíduos normalmente são depositados, a valorização dos subprodutos tem por efeito a redução do consumo de matérias-primas virgens. Este artigo descreve um estudo no qual o fosfogesso, gerado pelas indústrias de produção de ácido fosfórico, foi empregado na formulação de um cimento em substituição total à gipsita. Buscou-se formular um cimento com baixo impacto ambiental (BIA) composto de mínimas quantidades de clínquer e máximas de fosfogesso. O clínquer empregado foi o sulfoaluminoso, caracterizado por necessitar de maiores quantidades de sulfato de cálcio em relação ao cimento Portland. Seis composições foram estudadas, cujas quantidades de fosfogesso e clínquer variaram entre 70-95% e 5-30%, respectivamente. A performance do BIA foi avaliada quanto à resistência mecânica e ensaios de durabilidade em argamassa padrão (NF EN 196-1). As interações entre fosfogesso e clínquer foram investigadas através da difração aos raios X (DRX) e análise térmica diferencial (DTA). Na análise da argamassa padrão, com a proporção de 1:3 (cimento:areia), a formulação composta por 30% de clínquer e 70% de fosfogesso apresentou resistência mecânica superior a 20 MPa aos 28 dias.The possibility of using industrial residues as raw materials for construction products has increased its importance for the environment and has also created new technological challenges. This article describes a study in which phosphogypsum, a by product of the phosphoric acid manufacturing industry, has been used for producing cement as a replacement for gypsum. The aim was to develop a cement with low environmental impact, with minimal consumption of clinker and maximum use of phosphogypsum (calcium sulfate). The sulfoaluminate clinker was used, which requires larger quantities of calcium sulfate in relation to Portland cement. Six combinations of phosphogypsum and clinker were tested, ranging between 70%-95% and 30%-5%, respectively. The performance of the low environmental impact was assessed, in terms of mechanical resistance, and durability tests for the standard mortar. (NF EN 196-1). The interactions between phosphogypsum and clinker were investigated by using XRD and DTA techniques. In the analysis of the standard mortar, with a proportion of 1:3 (cement: sand), the proportion of 70% phosphogypsum and 30% clinker resulted in a compressive strength higher than 20 MPa after 28 days

A Review: The Effect of Grinded Coal Bottom Ash on Concrete

This paper offers a review on the use of grinded coal bottom ash (CBA) on the concrete properties as demonstrated by strength test and microstructure test. Amount of CBA from power plant station was disposed in landfill because of the particle shape had a rough particles. By finding an alternative way to gain its surface area by grinding and used as replacement material as cement replacement may give a good side feedback on the strength and morphology of concrete. Most of the prior works studied on the grinded fly ash and grinded rice husk ash. The study on the influence of grinded CBA on the properties of concrete still limited and need more attention Therefore, the review on the effect of grinded CBA on the strength and microstructure of concrete are discussed

Management and valorisation of wastes through use in producing alkali-activated cement materials

There is a growing global interest in maximising the re-use and recycling of waste, to minimise the environmental impacts associated with waste treatment and disposal. Use of high-volume wastes in the production of blended or novel cements (including alkali-activated cements) is well known as a key pathway by which these wastes can be re-used. This paper presents a critical overview of the urban, agricultural, mining and industrial wastes that have been identified as potential precursors for the production of alkali-activated cement materials, or that can be effectively stabilised/solidified via alkali activation, to assure their safe disposal. The central aim of this review is to elucidate the potential advantages and pitfalls associated with the application of alkali-activation technology to a wide variety of wastes that have been claimed to be suitable for the production of construction materials. A brief overview of the generation and characteristics of each waste is reported, accompanied by identification of opportunities for the use of alkali-activation technology for their valorisation and/or management

Production of Synthetic Phosphoanhydrite and Its Use as a Binder in Self-Leveling Underlayments (SLU)

An experimental study was conducted to investigate the potential use of phosphogypsum (PG) to produce self-leveling underlayments. The study was designed in two stages. Initially a phosphoanhydrite (PA) was produced by heating phosphogypsum at temperatures of 350 °C, 450 °C, 550 °C, and 650 °C. Two periods of heating were applied (2 and 4 h). The formation of anhydrite was determined by thermogravimetric analysis (DTA-TG) and confirmed by X-ray diffraction (XRD). The results show that anhydrite II was obtained at temperatures above 450 °C, and at higher calcination temperatures the PA solubility was lower. In the second stage of this research, the PA was used in self-leveling underlayments as the main binder in the ternary system comprised of calcium sulfate, calcium aluminate cement, and Portland cement. Self-leveling mortar screeds produced using PA (550 °C/4 h) and PA (650 °C/4 h) showed the best performance in terms of mechanical strength and no degradation was observed after immersion and immersion-drying tests. The formation of ettringite, identified by scanning electron microscopy (SEM), may have contributed to these results. Morphological changes were studied using the scanning electron microscopy (SEM) technique