Using a fly ash pozzolan consumes calcium hydroxide ch. It is estimated that only about 20 to 30% of the globally generated fly ash is employed and utilized in building materials mainly as an additive in cement, concrete, and structural filling as well as in small scale production of zeolite. Heavy use areas other uses approaches to using fly ash. The properties of fly ash can greatly affect the properties for both fresh concrete and hardened concrete. This paper presents an overview of the work carried out on the chemical properties and use of fly ash as. High ash contents significantly reduce the energy output derived from a specific biomass source. Fly ash can be used as prime material in many cementbased products, such as poured concrete, concrete block, and brick. Berry, malhotra, lane and lee,, reported that fly ash with high loi value may affect the concrete properties.
It is a fine grey coloured powder having spherical glassy particles that rise with the flue gases. The burning conditions within a power plant can also affect the properties of the fly ash. Many countries have their own national standards and specifications regulating the use of fly ash in concrete. The permeability of concrete reduces on addition of fly ash to cement. What is fly ash, slag, and silica fume and why do we use.
Pdf fly ash is the finely divided mineral residue resulting from the combustion of coal in electric generating plants. Pdf contribution of fly ash to the properties of mortar and. Road construction projects using pcc can use a great deal of concrete, and substituting fly ash provides significant economic. This document provides basic technical information about the various uses of fly ash in highway construction. Characterization of fly ash and it effects on the compressive. What is fly ash, slag, and silica fume and why do we use them. Mix proportions and mechanical properties of concrete. The concrete incorporating the fly ashes is, therefore, considered stable. The calcium content of the fly ash is perhaps the best indicator of how the fly ash will behave in concrete thomas 1999, although other compounds such as the alkalis. All fly ashes exhibit cementitious properties to varying degrees depending on the chemical and physical properties of both the fly ash and cement. The chemical properties of fly ash are influenced to a great extent by those of the coal burned and the techniques used for handling and storage. The concrete properties such as compressive strength test, splitting tensile strength test and.
Standard guide for characterization of coal fly ash and clean. Indian standard specification for fly ash for use as pozzolana and admixture bureau of indian st gr 3 andards. Typical ranges for geotechnical properties of fly ash and bottom ash. The indian method uses a mix of fly ash, lime and gypsum that completely replaces the use of clay from the soil. Pdf contribution of fly ash to the properties of mortar. This video introduces fly ash, slag and silica fume and discusses their properties. Properties of fly ash products for use in portland cement concrete xiuping feng, boyd clark. The most widely used specification for fly ash in north america is astm c618 standard specification for coal fly ash and raw or. It can be used fro pozzolanic material for making ppc.
Precast producers like fly ash because it reduces material cost and results in stronger concrete. Filler in asphalt, flowable fill, and structural fills can accept fly ash with elevated carbon contents. Ash facts for highway engineers in 1986, the use of fly ash in highway construction has increased and new applications have been developed. Fly ash, slag, silica fume, and natural pozzolans, chapter 3. In lowdensity concrete, cenosphere can be used as fillers. Compared to cement and water, the chemical reaction between fly ash and calcium hydroxide typically is slower resulting in delayed hardening of the concrete. The third report of the series summarizes the effects of fly ash on the durability of concrete containing fly ash. Fly ash properties, types, mechanism and uses fly ash is a heterogeneous byproduct material produced in the combustion process of coal used in power stations. The pozzolanic material is in finely divided form and the material mainly used for making portland pozzolana cement is fly ash and calcined clay. Type c fly ash is produced from the combustion of lignite or sub bituminous coals, contains cao higher than 10 percent and possesses cementitious properties in addition to pozzolanic properties. Astm c 618 classifies fly ash based on the sum of its primary constituents sio2, al2o3, fe2o3.
Uses, benefits, and drawbacks of fly ash in construction. It is nowadays used in cement, concrete and other cement based applications in india. Type f fly ash is produced from the combustion of bituminous or an anthracite coal contains cao below 10 percent and possesses pozzolanic properties. Fly ash concrete is an ecofriendly construction material in which fly ash replaces a part of portland cement. This book draws together a large quantity of research that has been carried out on pulverised fuel ash pfa over the past 30 years. Table 1 lists ranges for some ofthe important geotechnical properties of fly ash and bottom ash. Similarly, as moisture content in the flue gas is increased, the fly ash resistivity decreased. To demonstrate the beneficial effect of application of fly ash on soil physical properties, soil fertility and crop yields, 3. Dec 04, 2017 this video introduces fly ash, slag and silica fume and discusses their properties. It can also be used in plastics and composite materials such as.
Characteristics, management and environmental issues. Contribution of fly ash to the properties of mortar and concrete. Fly ash can be transferred using air slides, bucket conveyors and screw conveyors, or it can be pneumatically conveyed through pipelines under positive or negative pressure conditions fly ash is transported to markets in bulk tanker trucks, rail cars and bargesships fly ash can be packaged in super sacks or smaller bags for. It is easily proportioned to suit almost any application and uses conventional materials found in almost every. Concrete production, as a substitute material for portland cement, sand. Fly ash booklet for pdf federal highway administration. Fly ash slightly improves the resistance of concrete to sulphate attack. Cenosphere properties, benefits, uses of cenospheres. Coal ash uses include approximately in order of decreasing importance.
Widely used in the uk to increase the strength of concrete, fly ash is also used to improve workability of fresh concrete and reduce water demand, shrinkage and permeability of the finished product. Heres where the importance of fly ash in concrete becomes clear. For production of good quality fly ash bricks the quality of fly ash should be as follows. Beneficial reuse of coal ash from dominion energy coal ash. In some states, fly ash is specified for all concrete structures. Fly ash, slag, silica fume, and natural pozzolans fly ash, ground granulated blastfurnace slag, silica fume, and natural pozzolans, such as calcined shale, calcined clay or metakaolin, are materials that, when used in conjunction with portland or blended cement, contribute to the properties of the hardened concrete through hydraulic or. Part 1 covering use of fly ash as a pozzolana, part 2 covering use of fly ash as an admixture for concrete, and part 3 covering use of fly ash as fine aggregate for mortar and concrete.
The properties of fly ash and bottom ash make them useful for a variety of construction applica tions. Some of them are being put to use already, or being considered in south africa, are described below, as well as emerging potential uses. More than 75% of all concrete is made with fly ash. A pozzolan is a siliceousaluminous material that, when mixed with lime and water, forms a cementitious compound. There are basically four types, or ranks, of coal, each of which varies in terms of its heating value, its chemical composition, ash content, and geological origin.
Fly ash is the finely divided mineral residue resulting from the combustion of coal in electric generating plants. In this paper, efforts has been made to study the behavior of fly ash bricks by taking different proportions of fly ash, cement, lime, gypsum and sand. Those cements were made near the small italian town of pozzuoli which later gave its name to the term pozzolan. Fuel ash and fly ash are produced as waste from burining coal or waste materials and have many uses within the construction industry such as in concrete land reclamation, treating oil and sewage wastes, bricks and blocks and grouting voids in the. The two properties that have the most influence on ash resistivity are temperature and humidity. Properties and use of coal fly ash ice virtual library. One of the most common uses of fly ash is in portland cement concrete pavement or pcc pavement. Effect of palm oil fuel ash pofa on strength properties of concrete. Fly ash properties, analysis and performance ebook. Pdf indian standard specification for fly ash for use as. Fuel ash and fly ash are produced as waste from burining coal or waste materials and have many uses within the construction industry such as in concrete land reclamation, treating oil and sewage wastes, bricks and blocks and grouting voids in the ground. Caol based thermal power plants in india account for more than 65% of installed capacity and 70% of. Fly ash properties and uses monolithic dome institute.
Three types of fly ash bricks in the different percentage of cement such as 3%, 5% and without cement are designed and then various tests such as compressive strength test, water. Portland pozzolana cement ppcdefinition, properties. Beneficial reuse of coal ash from dominion energy coal ash sites feasibility assessment november 30, 2017 dr. Ash that falls to the bottom of the boilers combustion chamber commonly called a firebox is called bottom ash. Fly ash bricks are hitech wellimproved quality bricks used for construction of brick masonry structures. Fly ash consists primarily of oxides of silicon, aluminum iron and. Currently, fly ash is used in more than 50% of all ready mixed concrete placed in the united states, yet many design professionals continue to remain overly restrictive. The advantage of fly ash is that it has already been mined and only needs to be transported to the site of use. Fly ash for controlled density fill controlled density fill cdf, also known as flowable fill, is an engineered, controlled fill material which is selfplacing, selfleveling, selfcompacting and nonsettling.
And the concrete industry is only one of the important entities using this abundant waste material. Characterization of fly ash and it effects on the compressive strength properties of portland cement ozlem celik a, erdem damc. An indication of fuel cenosphere combustion taken place using the open burning of heavy liquid fuels and fuel droplets such as a thermoplastic material or asphalt which causes bubbling as they get burned and the impact of the bursting of the bubbles has created airborne droplets of fuel. The sectional committee responsible for the formulation of thisstandard subsequently felt that the performance of fly ash as a pozzolana or an admixture. Chapter 1 fly ash an engineering material fly ash facts. Fly ash has been used in roadways and interstate highways since the early 1950s. Fly ash normally produced from burning anthracite or bituminous coal f that meets the applicable requirements for this class as given herein. Strength fly ash can increase strength strength gain happens slower with a pozzolanic class f vs. Fly ash utilization survey data, acknowledged as incomplete, are published annually by the american coal ash association.
Effect of palm oil fuel ash pofa on strength properties. Fly ash consists of inorganic, incombustible matter present in the coal that has. High loi fly ash absorbed more water and chemical admixtures, such as ae agent and sp, resulted in increasing the slump loss, decreasing the airentraining effect and bleeding, and decreasing the strength of concrete. Fineness of fly ash is most closely related to the operating condition of the coal crushers and the grindability of the coal itself. Fly ash or flue ash, also known as pulverised fuel ash in the united kingdom, is a coal combustion product that is composed of the particulates fine particles of burned fuel that are driven out of coalfired boilers together with the flue gases.
They are used as replacement for normal clay bricks and has better properties than it. Flue gas properties also affect fly ash resistivity. The second report summari zes the effect of fly ash on concrete used for highway applications. Fly ash pellets which can replace normal aggregate in concrete mixture. Fly ash bricks and comparison with clay bricks composition. Fly ash historically comprised approximately 75% of the coal ash generated annually in the us.
In the united states, astm c 6181, standard specification for coal fly ash and. In thermal power plants, burning coal produces fly ash which has ceramic particles largely made of alumina and silica. Fly ash used to increase strength of concrete cemex uk. Standard guide for characterization of coal fly ash and. Because modern coalfired power plants produce a number of other products besides ash, fly ash currently only represents about 40% of the total ccps generated in the us other ccps include non ash products such as fgd materials, defined below. Fly ash a fine powdery material that flies up during the coal combustion process and.
Caol based thermal power plants in india account for. High volume fly ash concrete is a concrete where a replacement of about 35% or more of cement is made with the usage of fly ash. Fly ash closely resembles volcanic ashes used in production of the earliest known hydraulic cements about 2,300 years ago. Fly ash is the fine ash produced at coalfired power plants that develops cementitious properties when mixed with cement and water. Evaluation of the physical and chemical properties of fly ash.
The effect of fly ash chemical composition on the degradation of pvc composites was studied by comparing the thermal properties of composites containing. Fly ash bricks competitive in comparison to the conventional clay bricks and provide enormous indirect benefits. Portland pozzolana cement ppcdefinition, properties, uses. To improve the socio economic status of farming community by applying the cheap source of nutrient material and the technology. Currently, fly ash is used in more than 50% of all ready mixed concrete placed in the united states, yet many design professionals continue to remain overly restrictive when it comes to using fly ash in concrete. This book provides new research on the characteristics, uses and performance of fly ash. The calcined clay has low carbon content and it can reduce carbon content to 30 percent when comparing to the production of ordinary portland cement.