Utilization of fly ash in concrete

Fly ash, a by-product of coal burning power plants, is produced in large quantities each year. It is commonly known that fly ash possesses pozzolanic behavior which can enhance the properties of concrete. Due to a lack of proper understanding on the formation of fly ash and its performance in concrete, the question of quality assurance has frequently been a major concern of engineers using fly ash in their construction projects. As a result, much fly ash is disposed of as waste material in landfills. Recent environmental concerns and a shortage of landfill space have rapidly escalated the disposal cost of fly ash and therefore, the need to seek better utilization of fly ash in concrete is then critical. The objective of this investigation is to study the effect of fly ash on the strength development of mortar and concrete and to develop models to predict its performance in these cementitious composites. The fly ash used was carefully selected and defined as to its origination, formation, physical and chemical compositions, and the storage condition. The original fly ash was fractionated into six particle size ranges, each having a relatively uniform particle size, with maximum sizes ranging from 5 to 300 microns. The rate of strength gain of these fly ash concretes was monitored from 1 to 180 days. The compressive strength for each series was correlated to the conditions of fly ash used to determine the major parameters affecting the performance of fly ash in mortar and concrete. The results from this study show that the particle size of fly ash has a significant effect on the strength development of concrete. The combustion condition in the boiler has some influence on the performance of fly ash in cementitious composites. Of particular importance is the finding that certain portions of fly ash when used as cement replacement can improve the strength of concrete beyond normal cement as early as 14 days. A correlation to predict the compressive strength of fly ash concrete is proposed and provides good agreement with experimental results both from this study as well as from other investigators

COHESION IN NARRATIVE ESSAY WRITING OF EFL SECONDARY STUDENTS IN THAILAND

Cohesion has been in the limelight of many linguists in terms of investigating how texts are related to each other. This study examines what cohesive devices are used in students’ narrative essays and which cohesive device is most frequently used in each type among three groups of students. Thirty participants, all of whom were grade 11 students at a public school in Bangkok, were divided into three groups: advanced, intermediate and beginner. The main instrument for data analysis was a sample of 30 finished student’s narrative essays in which cohesion was extracted. The findings revealed that four types of cohesion: reference, substitution, conjunction and lexical cohesion were found in students’ narrative essays, while elliptical cohesion was noticeably absent. The comparison of each sub-category among three target groups showed that 141 personal references ‘I’ was the most frequently used in the advanced group, followed by 113 additive conjunctions ‘and’ in the advanced group, 95 collocations in the advanced group and 18 nominal substitutions ‘one’ in the beginner group respectively. This study could provide useful suggestions for the EFL writing classroom for not only students to improve the use of cohesion in their writings but also for teachers to prepare a practical writing pedagogy for the EFL students

Influencia de la ceniza de bagazo de diferentes finuras en la reacción álcali-sílice del mortero

This research aimed to study the effect of finenesses of bagasse ash (BGA) on the alkali-silica reaction of mortar. The BGA sample was ground to have particles retained on a sieve No. 325 of 33±1% and 5±1% by weight. Ground BGA samples were used separately to replace ordinary Portland cement (OPC) at rates of 10, 20, 30 and 40% by weight of binder to cast mortars. The compressive strengths and the alkali-silica reaction (ASR) of mortars were investigated. The results showed that a large particle size of BGA is not suitable for use in lowering ASR because it results in a low compressive strength and high expansion due to ASR. The mortars containing BGA with higher fineness exhibited higher compressive strength and lower expansion due to ASR than the mortars containing BGA with lower fineness. The results also suggested that the ground BGA retained on a sieve No. 325 of less than 5% by weight is suitable to be used as a good pozzolan which provides high compressive strength and reduces the expansion of mortar due to ASR even though it contains high LOI. The obtained results also encourage the utilization of ground BGA effectively which leads to reduce the disposal of bagasse ash.Esta investigación tiene como objetivo estudiar el efecto de la finura de la ceniza de bagazo (BGA) en la reacción álcali-sílice del mortero. La muestra de BGA fue molida para conseguir partículas retenidas en un tamiz No. 325 de 33 ±1% y 5±1% en peso. Las muestras de BGA molidas fueron utilizadas separadamente para reemplazar el cemento Portland en proporciones del 10, 20, 30 y 40% en peso en el mortero. Se estudiaron tanto las resistencias a compresión como la reacción álcali-sílice (RAS) de los morteros. Los resultados indicaron que la utilización de un tamaño mayor de las partículas de BGA no es recomendable para disminuir la RAS ya que conlleva a una disminución de las resistencias a compresión y a una alta expansión debido a la RAS. Los morteros que contenían BGA de una mayor finura exhibían mayor resistencia a compresión y una menor expansión, debido a la RAS, que los morteros que contenían BGA de menor finura. Al mismo tiempo los resultados sugieren que el BGA molido retenido en un tamiz No. 325 de menos de un 5% en peso es apropiado para ser usado como material puzolánico, ya que provee una gran resistencia y reduce la expansión del mortero producido por la RAS a pesar de contener una alta pérdida por calcinación. Los resultados obtenidos también recomiendan la utilización eficiente del BGA molido ya que conlleva una disminución de los desechos de las cenizas de bagazo

Influence of Palm Oil Fuel Ash and W/B Ratios on Compressive Strength, Water Permeability, and Chloride Resistance of Concrete

This research studies the effects of W/B ratios and palm oil fuel ash (POFA) on compressive strength, water permeability, and chloride resistance of concrete. POFA was ground until the particles retained on sieve number 325 were less than 5% by weight. POFA was used to partially replace OPC at rates of 15, 25, and 35% by weight of binder. The water to binder (W/B) ratios of concrete were 0.40 and 0.50. The compressive strength, water permeability, and chloride resistance of concrete were investigated up to 90 days. The results showed that POFA concrete with W/B ratio of 0.40 had the compressive strengths ranging from 45.8 to 55.9 MPa or 82–94% of OPC concrete at 90 days, while POFA concrete with W/B ratio of 0.50 had the compressive strengths of 33.9–41.9 MPa or 81–94% of OPC concrete. Furthermore, the compressive strength of concrete incorporation of ground POFA at 15% was the same as OPC concrete. The water permeability coefficient and the chloride ion penetration of POFA concrete were lower than OPC concrete when both types of concrete had the same compressive strengths. The findings also indicated that water permeability and chloride ion penetration of POFA concrete were significantly reduced compared to OPC concrete

Properties of concrete made from industrial wastes containing calcium carbide residue palm oil fuel ash rice husk-bark ash and recycled aggregates

บทคัดย่อคอนกรีตนี้ถูกทำขึ้น โดยใช้วัสดุเหลือทิ้งอุตสาหกรรมทั้งในวัสดุประสานและมวลรวมกากแคลเซียมคาร์-ไบด์ (CCR) ผสมแยกกับเถ้าปาล์มน้ำมัน (PA) และเถ้าแกลบเปลือกไม้ (RA) นำมาใช้เป็นวัสดุประสานแทนที่ปูนซีเมนต์ในส่วนผสมคอนกรีต นอกจากนี้มวลรวมรีไซเคิลถูกนำมาใช้แทนที่มวลรวมธรรมชาติเพื่อที่หล่อตัวอย่างคอนกรีต (คอนกรีต CCR-PA และ CCR-RA) สมบัติของคอนกรีต ได้แก่ กำลังอัด การแทรกซึมของคลอไรด์ และการซึมของน้ำผ่านคอนกรีตได้รับการประเมินและเปรียบเทียบกับคอนกรีตควบคุม (คอนกรีต CON) ผลการวิจัยพบว่าวัสดุประสาน CCR-PA และ CCR-RA สามารถนำมาใช้เป็นสารยึดเกาะในคอนกรีตที่ใช้มวลรวมรีไซเคิล แม้ว่าวัสดุประสาน CCR-PA และ CCR-RA มีหรือไม่มีปูนซีเมนต์ การพัฒนากำลังอัดของคอนกรีต CCR-PA และ CCR-RA คล้ายกับคอนกรีต CON นอกจากนี้วัสดุประสาน CCR-PA และ CCR-RA สามารถปรับปรุงการแทรกซึมของคลอไรด์และการซึมของน้ำผ่านคอนกรีตได้อย่างมีประสิทธิภาพ ผลการวิจัยยังชี้ให้เห็นว่าคอนกรีต CCR-PA และ CCR-RA สามารถใช้เป็นคอนกรีตที่เป็นมิตรต่อสิ่งแวดล้อมชนิดใหม่ เพราะคอนกรีตเหล่านี้สามารถลดการปล่อยก๊าซคาร์บอนไดออกไซด์และลดปัญหาสิ่งแวดล้อมAbstractThis concrete was made by using several industrial wastes in both binder and aggregates. Calcium carbide residue (CCR) mixed separately with palm oil fuel ash (PA) and rice husk-bark ash (RA), and was used as a binder instead of Portland cement in the concrete mixture. Furthermore, recycled aggregates were fully replaced natural aggregates in order to cast concrete specimens (CCR-PA and CCR-RA concretes). Concrete properties namely compressive strength, chloride migration, and water permeability of CCR-PA and CCR-RA concretes were evaluated and compared with the conventional concrete (CON concrete). The results indicated that CCR-PA and CCR-RA binders could be used as a new cementitious material in recycled aggregate concrete, even though the CCR-PA and CCR-RA binders contained no Portland cement. The characteristic compressive strength of CCR-PA and CCR-RA concretes developed similar to CON concrete. Moreover, CCR-PA and CCR-RA binders in the mixtures were effectively improving the chloride migration and water permeability of recycled aggregate concretes. These results also suggested that CCR-PA and CCR-RA concretes can be used as a new environmental friendly concrete because of these concretes can reduce as much as CO2 emissions and environmental problems

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

Effect of Fly Ash on Chloride Penetration and Compressive Strength of Reclycled and Natural Aggregate Concrete under 5-year Exposure in Marine Environment

งานวิจัยนี้ศึกษาผลของเถ้าถ่านหินต่อสัมประสิทธิ์การแทรกซึมของคลอไรด์ และกำลังอัดของคอนกรีตที่ใช้มวลรวมจากเศษคอนกรีต และมวลรวมจากธรรมชาติภายใต้สภาวะแวดล้อมทะเลเป็นเวลา 5 ปี โดยใช้เถ้าถ่านหินจากแม่เมาะแทนที่ปูนซีเมนต์ปอร์ตแลนด์ประเภทที่ 1 ในคอนกรีตที่ใช้มวลรวมจากเศษคอนกรีตและมวลรวมจากธรรมชาติในอัตราส่วนร้อยละ 0, 15, 25, 35 และ 50 โดยน้ำหนักวัสดุประสาน และใช้อัตราส่วนน้ำต่อวัสดุประสาน (W/B) เท่ากับ 0.40 และ 0.45 สำหรับมวลรวมจากเศษคอนกรีต และ 0.45 สำหรับมวลรวมจากธรรมชาติ หล่อตัวอย่างคอนกรีตทรงลูกบาศก์ขนาด 200×200×200 มม.3 สำหรับทดสอบการแทรกซึมคลอไรด์และกำลังอัดของคอนกรีต หลังจากบ่มคอนกรีตในน้ำเป็นเวลา28 วัน นำตัวอย่างทดสอบไปแช่ในสิ่งแวดล้อมทะเลบริเวณชายฝั่งในสภาวะเปียกสลับแห้ง โดยเก็บตัวอย่างทดสอบการแทรกซึมของคลอไรด์ทั้งหมด และกำลังอัดของคอนกรีตที่อายุแช่น้ำทะเล 5 ปี ผลการศึกษาพบว่า คอนกรีตที่ใช้มวลรวมจากเศษคอนกรีตทุกส่วนผสม มีการสูญเสียกำลังอัดหลังแช่น้ำทะเลเป็นเวลา 5 ปี ส่วนกลุ่มที่ใช้มวลรวมจากธรรมชาติที่ผสมเถ้าถ่านหินทุกส่วนผสม มีกำลังอัดหลังแช่น้ำทะเลที่อายุ 5 ปี เพิ่มขึ้นจากอายุบ่ม 28 วัน การใช้เถ้าถ่านหินแทนที่ปูนซีเมนต์ปอร์ตแลนด์ประเภทที่ 1 ในปริมาณที่สูงขึ้น ส่งผลต่อการลดสัมประสิทธิ์การแทรกซึมของคลอไรด์ในคอนกรีตลงได้อย่างชัดเจนซึ่งให้ผลไปในทิศทางเดียวกันทั้งกลุ่มที่ใช้มวลรวมจากธรรมชาติและมวลรวมจากเศษคอนกรีต โดยพบว่า คอนกรีตที่ใช้มวลรวมจากเศษคอนกรีตที่ผสมเถ้าถ่านหินอย่างน้อยร้อยละ 15 โดยน้ำหนักวัสดุประสาน ให้สัมประสิทธิ์การแทรกซึมของคลอไรด์ต่ำกว่าคอนกรีตธรรมดาที่ใช้มวลรวมจากธรรมชาติ ซึ่งมีอัตราส่วนน้ำต่อวัสดุประสานเท่ากับ 0.45This research studied the effect of fly ash on chloride diffusion coefficient and compressive strength of both recycled and natural aggregate concretes exposed to marine environment for 5 years. Mae-Moh fly ash was used to replace Portland cement at the percentages of 0, 15, 25, 35, and 50 by the weight of binder with various water to binder (W/B) ratios of 0.40 and 0.45 in recycled aggregate mixtures and a W/B ratio of 0.45 in natural aggregate mixtures. Concrete cube specimens of 200×200×200 mm3 were cast and cured in fresh water for 28 days and then were placed in a tidal zone of marine environment. The compressive strengths of the concrete exposed to marine environment for 5 years as well as the total chloride diffusion coefficients of the specimens were determined. The Results revealed that the compressive strengths of recycled aggregate concretes decreased after being exposed in marine environment for 5 years, whereas those of natural aggregate concretes and fly ash increased after 28 days of curing. Evidently, higher in fly ash contents would lower chloride diffusion coefficients of both recycled and natural aggregate concretes. Furthermore, use of fly ash as low as 15% replacement by weight in recycled aggregated concretes could provide lower chloride diffusion coefficient compared to Portland cement containing natural aggregate concrete with W/B of 0.45

Effect of high volume of fly ash from 5 sources on compressive strength and acid resistance of concrete

The purpose of this research was to examine the effect of high volume of fly ash from various sources on compressive strength and acid resistance of concrete. Fly ashes from 5 sources were collected and classified by an air classifier into 3 groups of different degree of fineness; low, medium, and high fineness. Portland cement type I was replaced by fly ash at the rate of 50% by weight of cementitious materials (Portland cement type I and fly ash) to cast concrete cylinders of 10 cm in diameter and 20 cm in height. After fly ash concreteswere cured in water for 28 days, they were tested to determine the compressive strength. In addition, the specimens were immersed in 3% of sulfuric acid solution and the weight losses of concretes were measured from 3 to 90 days. It was found that the compressive strengths of fly ash concretes were more than 77% of the control concrete when the high fineness fly ashes were used. Each source of the fly ash had different effect on the compressive strength as well as on the sulfuric acid resistance of concrete. The compressive strength of fly ash concrete was improved with the use of high fineness fly ash; however, the sulfuric acid resistance of the concrete tended to decrease as the fineness of fly ash increased