Because cement, fly ash and admixture prices vary throughout the country, cost differences will also vary. Concrete without cement is possible by the use of fly ash. Porfotlng orgortla111tion n ortd a44reu center for transportation research the university of texas at austin austin, texas 787121075 technical report standard title page 3. Highvolume fly ash concrete university of wisconsin. The paste is typically made up of portland cement and water and may also contain supplementary cementing materials scms, such as fly ash or slag cement, and chemical admixtures figure 11. Coalbased thermal power plants all over the world facing serious problems of handling and disposal of. A comparison of the rate of strength development of the control and fly ash concretes is also provided. In this type of concrete, the water and cement astm type i contents are kept very low, about 115 and 155 gm 3, respectively, and the proportion of lowcalcium fly ash in the total cementitious materials content is about 56 percent. Fly ash is an byproduct of thermal power plant as its waste p. Wc maximum values for different concrete classes concrete class cement class concrete. The fineness of individual fly ash particle rage from 1 micron to 1 mm size. Fly ash used as a cement replacement must meet strict construction standards. Too much water dilutes cement paste binder, resulting in weak and porous concrete.
American concrete institute aci manual of concrete practice, section 211. Failures of fly ash settling ponds, like the 2008 tva spill, are extremely rare events, and in any case, only dry fly ash is used in concrete not wet material in settling ponds. When the watercement ratio law was proposed by abrams in 1918, the use of fly ash and silica fume as replacements. Therefore, fly ash and polycarboxylic acid superplasticizer can effectively promote the hydration of cement particles and improve the pore structure of concrete along with the bond between cement.
Wc maximum values for different concrete classes concrete class cement class concrete homogenous grade 32. Moreover, in construction, the use of fly ash would result in the reduction of the cost of. A supplementary cementitious material, when used in conjunction with portland cement, contributes to the properties of the hardened concrete through hydraulic or. It predicts a small shortage in the uk in 2016 and subsequent years, indicating that supply in the. From research, it has been observed that the use of 30% of fly ash and 70% of cement possess a superior performance. Fly ash is used as a supplementary cementitious material scm in the production of portland cement concrete. The fineness of fly ashparticles has a significant influence on its performance in cement concrete. Fly ash bricks competitive in comparison to the conventional clay bricks and provide enormous indirect benefits. Coal is a material thats full of harmful substances, and there are still some questions about whether heavy metals would be able to leach from concrete made with coal ash. Concrete is modest in its energy needs and generous in its payback. Strengthening of cement concrete using fly ash and.
Livingston 2 1 vitreous state laboratory, the catholic university of america, washington dc 20064. The effects of mix design technique, quantity of cement in the mix and the curing period on the strength development of fly ash concrete are also included. Durability of concrete using fly ash as a partial replacement of. The water cement ratio wc is established from the table 3 according to the concrete class, cement class, concrete homogenous grade and aggregate type. In a high percentage of situations, todays cementitious material content is made up of cement plus fly ash. Fly ash or flue ash, also known as pulverised fuel ash in the united kingdom, is a coal. Pdf effects of fly ash on mechanical properties of concrete. The objectives of this study are 1 to provide the reader with a good summary of the technical literature on fly ash, 2 to show both the adequact and the limitations of current test methods and specifications to assure predictable and improved performance of fly ash with cement in concrete, and 3 to identify research needs. If the fly ash or ggbfs is blended or interground with the cement, the cement shall comply with the specifications and the requirements stated in this procedure. The term concrete refers to a mixture of aggregates, usually sand, and either gravel or crushed stone, held together by a binder of cementitious paste. Fly ash concrete mix design and the watercement ratio law. Class f fly ash from mae moh power plant in the north of thailand, astm type i portland cement pc, and tap water were used in this study.
Inert filler material usually sand and stone or gravel make up between 60 to 80 percent of the. The use of fly ash in portland cement concrete pcc has many benefits and. As a part of this program, a new type of concrete known as highvolume fly ash concrete has been developed. Fly ash concrete is basically the same as regular concrete except some of the cement has been replaced with a material called fly ash.
About 95% of all co 2 emissions from a cubic yard of concrete are from cement manufacturing. Item p501 refers to the portland cement associations pca manual for mix design. The fhwa indicated that the replacement of cement with fly ash of the order of 10% to 25% can be made giving equal or better concrete strength and durability. Portland cement consists essentially of compounds of lime calcium oxide, cao mixed with silica silicon dioxide, sio2 and alumina aluminum oxide, al2o3. Th e objective was to achieve 28day strength equivalent to a portland cement concrete mixture with. The pozzocrete brand is reserved only for those grades. Creep and shrinkage properties in concrete containing fly ash. Strength development in concrete with wood ash blended. The heat of hydration in concrete using fly ash as a partial replacement of cement is influenced by many parameters, such as the ambient temperature in the curing climate, the amount of cement, the amount of fly ash, and the chemical composition and fineness of the cement and fly ash 9. Enhanced research on the use of fly ash as a goodquality alternative to pozzolana led to its first application as a concrete admixture in the late1940.
Opc was replaced with rha by weight at 5%, 10% and 15%. If the fly ash or ggbfs is blended or interground with the cement, the cement shall comply with the specifications and the requirements stated in this. Many materials that would end up in landfills can be used instead to make concrete. Effect of partial replacement of cement by fly ash, rice husk ash with using steel fiber in concrete r. Another potential application of bottom ash is for internal curing of highvolume fly ash hvfa concrete concrete with at least 50% of the portland cement replaced with fly ash. To deal with both of those problems, the construction industry had the clever idea to start formulating concrete out of fly ash, substituting fly ash for portland cement the primary ingredient in most concrete. Historically, fly ash has been used in concrete at levels ranging from 15% to 25% by mass of the cementitious material component. Surprisingly, fly ash has several characteristics that make it a perfect ingredient for concrete. Fly ash a 95 125 45 45 series a2 b 35 5 60 5 6o 8o s2 c 60 150 75 170 80 120 fly ash concrete concluding remarks in a lean concrete mixture with cement content 350 ibyd3 210 kgm3, it was possible to replace 40 to 50% cement by weight with astm class f or class c fly ashes, and meet the. Effect of fly ash and nano titanium dioxide on compressive. The future of fly ash use in concrete national precast. Bottom ash, cement, coarse aggregate, concrete, sands, strengths. This paper investigates the effect of fineness and replacement levels of fly ash on the fluidity of cement paste, mortar. This paper represents the effect on compressive strength of concrete by partially replacing a cement with fly ash 0%, 10%, 20%, 30% and nano titanium dioxide 0%.
As a cement replacement, fly ash plays the role of an artificial pozzolan, where its silicon dioxide content reacts with the calcium hydroxide from the cement hydration process to form. It is important to reduce co 2 emissions through the greater use of substitute to ordinary portland cement opc such as fly ash, clay and others geobased material. It also reduces the energy intensive manufacturing of portland cement. In the fly ash addition method, fly ash is added to the regular amount of cement. This increases strength and reduces permeability 1 objective of this study to tests and analysis on fly ash concrete prepared by fly ash optimum replacement with cement. Pdf cement is a common and widespread building material over the world. For the study, six different proportion of concrete mixes wa replacement of 5%, 10%, 15%, 18% and 20% by weight of cement including the control mixture were prepared with water to binder ratio of 0. Concrete quality varies widely, depending on the characteristics of its ingredients and the proportion of the mix. This coal powder is blown into the power plants boiler, the carbon is consumed leaving molten particles rich in silica, alumina. Two fly ash finenesses, an original fly ash ofa with the median particle size of 19. There is often confusion citation needed between the meanings of the terms geopolymer cement and geopolymer concrete.
What is the best replacement for cement in concrete. Portland cement hydration the key reaction in the development of strength in concrete is the hydration of portland cement which represented by its main compo nent, tricalcium silicate with formula. The improved workability is a result of the ball bearing action of the spherical fly ash particles. The use of highvolume fly ash hvfa concretes has recently gained popularity as a resourceefficient, durable, costeffective, sustainable option for many types of portland cement concrete pcc applications. Strength and hydration heat of concrete using fly ash as a. Concrete is an ideal medium for recycling waste or industrial byproducts. Effective use of ash in cementconcrete technology overview 1.
Properties of highvolume fly ash concrete made with high. Partial replacement of cement with fly ash in concrete and. And lastly, the epa has not indicated any desire to restrict fly ash use in concrete. Sio 2, or c 3 s in cement notation yields excess ca. The grade of concrete is m40, cube and beam specimens are casted and cured for 28 and 56 days. Class n fly ashes are raw or calcined natural pozzolans.
But if fly ash is used as a filler to replace sand in concrete production. The use of fly ash, a recovered resource, reduces the depletion of natural resources. Use of recycled concrete aggregate in flyash concrete. Sep 20, 2017 the report models supply and demand for fly ash and granulated blast furnace slag up to 2030. It has great strength and durability although were still waiting to see how it. Yijin et al 2004 investigated the effect of fineness and replacement levels of fly ash on the fluidity of cement paste, mortar, and concrete. A figure of merit for fly ash replacement of portland cement. Fly ash improves the grading in the mixture by smoothing out the fine particle size. Replacing cement with the same amount of fly ash can reduce the heat of hydration of concrete. Introduction to concrete portland cement association. Each type of cement will produce concrete with different properties. The 30% replacement of cement with fly ash ultimate compressive strength of concrete decreases.
Strengthening of cement concrete using fly ash and metakoline. The green alternative to use of cement is fly ash which has same properties as that of cement both physically and chemically. Structural applications of 100 percent fly ash concrete. The effect of fly ash on the fluidity of cement paste, mortar. A cement is a binder, whereas concrete is the composite material resulting from the mixing and hardening of cement with water or an alkaline solution in the case of geopolymer cement, and stone aggregates. Effect of fly ash fineness on compressive strength and pore. Fly ash bricks are hitech wellimproved quality bricks used for construction of brick masonry structures. Fly ash in concrete part ii concrete construction magazine. The pozzocrete fly ash range is an artificial pozzolan, specially designed to achieve optimum performance on most cement and concreteapplications. The cementitious content of the mix is thus increased, and usually the mix is adjusted by reducing the fine aggregate content. Depending on the strength requirements of the concrete, the proximity of the ash source and comparative local cement and ash prices, the cost savings for cementitious. The concrete incorporating the fly ashes is, therefore, considered stable.
This paper investigates the effect of fineness and replacement levels of fly ash on the fluidity of cement paste, mortar, and concrete. Research has been conducted on utilizing fly ash in the cement sector as an alternative for pozzolana. The effect of fly ash on the fluidity of cement paste. Any concrete containing a fly ash content that is greater than 50 percent by mass of the total cementitious materials is considered hvfa. Fly ash in cement concrete ordinary portland cement opc is a product of four principal mineralogical phases. More than 12 million tons of coal fly ash are used in concrete products each year. The objectives of this study are 1 to provide the reader with a good summary of the technical literature on fly ash, 2 to show both the adequact and the limitations of current test methods and specifications to assure predictable and improved performance of fly ash with cement in.
The report models supply and demand for fly ash and granulated blast furnace slag up to 2030. Administration encouraged the use of fly ash in concrete pavement with its notice n 5080. They are used as replacement for normal clay bricks and has better properties than it. Geopolymer concrete by using fly ash in construction. Introduction 1 india produces approximately more than 100 million tonnes of coal ash annually.
This reduction in the heat of hydration does not sacrifice longterm strength gain or durability. Al 2 o 3 and tetracalcium aluminoferrite c 4 af4cao. Chapter 3 fly ash in portland cement concrete fly ash. The average 28 day unconfined compressive strength of the mixtures was 32 mpa 4700 psi. Fly ash is a byproduct and therefore less expensive than portland cement. The fineness of particles is measured by measuring specific surface area of fly ash by blaines specific area technique.
The results shown that strength of partially replaced cement by activated fly ash in concrete enhanced strength is observed and it is slow but. There are, however, m any variations of this procedure and a few are listed below. Concrete basics a guide to concrete practice cement industries. The addition of ultrafine fly ash ufa to cement paste, mortar and concrete can improve their fluidity, but some coarse fly ash cant reduce water. Proportioning fly ash as cementitious material in airfield pavement concrete mixtures. Blended cements contain portland cement and more than 5% of either fly ash, ground slag, silica fume, or a combination of these. Strength development of fly ash concretes springerlink. What is the highest percentage of fly ash that can be used in readymixed. Compressive strength of low cementhigh fly ash concrete. Fly ash concrete mix design and the watercement ratio law authors. Optimizing the use of fly ash in concrete portland cement.
Effect of fly ash fineness on compressive strength and. The watercement ratio wc is established from the table 3 according to the concrete class, cement class, concrete homogenous grade and aggregate type. A figure of merit for fly ash replacement of portland cement walairat bumrongjaroen 1 and richard a. Pdf effect of class f fly ash on the durability properties of concrete. F fly ash, slag cement, silica fume, and metakaolin a type of class n fly ash. The compressive strength of concrete was checked by replacing different proportions of cement with suitable quantities of fly ash and the results have been found most effective and applicable. The reduced heat of hydration lessens heat rise problems in mass concrete placements. In addition, in january 1983, the environmental protection agency published federal comprehensive procurement guidelines for cement and concrete containing fly ash to encourage the utilization of fly ash and establish compliance deadlines. The american concrete institute aci manual of concrete.
This reduction in energy leads to less emissions of greenhouse gases. The most common types of cement are type gp and type gb. Before coal is consumed in a power plant, it is first ground into a fine powder. The only energy intensive demand is in the manufacture of portland cement, typically a 1015% component of concrete. The 10% and 20% replacement of cement with fly ash shows good compressive strength for 28 days. At this dosage rate, the lime had nominal influence on the compressive strength of the concrete, but it did improve its finishability.
Strength development in concrete with wood ash blended cement. Uses of bottom ash in the replacement of fine aggregate. The incorporation of ultrafine fly ash may increase. Every 1 ton of concrete leads to co 2 emissions which vary between 0. This trend is primarily due to the lack of information available to the resident engineer concerning curing conditions. When compared with sf concrete at the same level of replacement, mk concrete showed a faster strength development at early ages, but had similar strength after 28 days 4. Essentially the fly ash has replaced fine aggregate rather than cement and this generally produces increased strength in concrete at all. This study investigates the applicability of abrams law to concrete mixes containing fly ash. Compressive strength developed by concretes containing fly ash up to 80% of the cementitious fraction is presented. In the ancient period, construction work was mostly carried out with help of mudstone from industry. Innovative pavement research foundation research report for. In the production of pozzocrete 40, 60, 63, and 83 high quality pfa were selected and industrially processed in order to obtain maximum performance as a cement replacement product. In many ways, fly ash concrete does look like a winner, but there are still some lingering concerns about the safety of surrounding ourselves with too much fly ash. In the flyashaddition method, fly ash is added to the regular amount of cement.
Since the early 1960s, concrete mix compositions have changed, and cement is no longer the only cementitious material in concrete mixes. Fly ash, pozzolanic, alkaliactivated, re placement factor, figure of merit. The actual amount used varies widely depending on the application, the properties. The effect of replacing 35 to 50 percent of cement by fly ash, on the compressive strength of lean concrete mixtures 350 lbsyd 3. Chapter 3 fly ash in portland cement concrete fly ash facts for.
1521 553 212 881 1429 1322 348 418 1109 1436 1251 3 1437 493 1275 969 1219 223 352 140 734 676 152 638 1501 965 100 741 361 464 182 417 805 1045 647 710 1064 736 1414 686 1366 1089