Portland Cement Association, Publication No. Ash from start-up or shut-down phases of operation. Class C fly ash has self-cementing properties as well as pozzolanic properties. endstream endobj 75 0 obj<> endobj 76 0 obj<> endobj 77 0 obj<>stream Q$@rx9y_sifc OEn qfnd45"J0^(0a(D8}nqb3v8U:6r&H&[5HaBUO2) Federal Highway Administration endstream endobj 214 0 obj<>stream Class C fly ash is usually substituted at a 1:1 ratio. Most specifying agencies refer to ASTM C618(2) when citing acceptance criteria for the use of fly ash in concrete. U.S. Bureau of Mines, Information Circular No. "Standard Specification for Fly Ash and Raw or Calcined Natural Pozzolan For Use as Mineral Admixture in Portland Cement Concrete," American Society for Testing and Materials, Annual Book of ASTM Standards, Volume 04.02, West Conshohocken, Pennsylvania, 1994. s*>MGJO3[xEG6KzI?0eL7-:KG^H"`w9d8P#24\/Ai^OP{py YFW. \"Tr9(l 0 Strength Development: Previous studies of fly ash concrete mixes have generally confirmed that most mixes that contain Class F fly ash that replaces Portland cement at a 1:1 (equal weight) ratio gain compressive strength, as well as tensile strength, more slowly than conventional concrete mixes for up to as long as 60 to 90 days. As a consequence of the Clean Air Act, many coal-fired power plants are being equipped with low NOx burners. #-Ce%f#Lp_LOT$Hv77x/x^MWuaamsD;kD,4:"+7=>, 46-oQLqopVq>tjDJH Z5Bsr&e4DG A_8LnU}h8LG)},'j{WQ)O j@

However, the American Concrete Institute (ACI) recommends that Class F fly ash replace from 15 to 25 percent of the Portland cement and Class C fly ash replace from 20 to 35 percent.(10). endstream endobj 230 0 obj<>/W[1 1 1]/Type/XRef/Index[168 27]>>stream startxref Ash from plants not operating at a "steady state.". As the fineness increases, the pozzolanic activity can be expected to increase. Ash that is handled and stored using a wet system. 0000011895 00000 n (13) Class C fly ashes should be individually tested before use in a sulfate environment. When fly ash is used, the absolute volume of cement plus fly ash usually exceeds that of cement in conventional concrete mixes. Once fly ash concrete has developed adequate strength, no significant differences in concrete durability have usually been observed. When using a blended cement, the water demand will probably be somewhat reduced because of the presence of the fly ash in the blended cement. A number of states also did not permit the use of fly ash in white concrete items, such as curbs, sidewalks, and median barriers, and two states (Arkansas and New Mexico) reported questionable performance experience: Arkansas had temporarily discontinued the use of fly ash in bridge deck concrete, and New Mexico had a temporary moratorium on the use of Class C fly ash in concrete, pending further investigation. Special attention must be given to attaining the proper amount of entrained air and air void distribution. Fineness: Fineness is the primary physical characteristic of fly ash that relates to pozzolanic activity. 4{((Pb0gf MQLf`,20pfd`ar 1P~f zT Structural design procedures for concrete pavements containing fly ash are no different than design procedures for conventional concrete pavements. 0000009260 00000 n 0000007213 00000 n Beyond 60 to 90 days, Class F fly ash concrete mixes will ultimately exceed the strength of conventional PCC mixes. The blended cement can be used in the mix design process in essentially the same way as a Type I Portland cement. Pozzolanic Activity (Chemical Composition and Mineralogy):Pozzolanic activity refers to the ability of the silica and alumina components of fly ash to react with available calcium and/or magnesium from the hydration products of Portland cement. }")E` L? endstream endobj The proper application of a curing compound should retain moisture in the concrete for a sufficient period of time to permit strength development. 0000001037 00000 n Hn@E)=#aV vA National Ready-Mix Concrete Association, Publication No. pA*~Jv0s:Lv2}|m|6@Mkw.XuHM(UE(B%(B*K:;|\/HIdmgG"[ Ash from plants burning different coals or blends of coal. (11) Some Class C fly ashes may improve sulfate resistance, while others may actually reduce sulfate resistance(12) and accelerate deterioration. Halstead, Woodrow J. endstream endobj 196 0 obj<> endobj 198 0 obj<>/Font<>>>/DA(/Helv 0 Tf 0 g )>> endobj 199 0 obj<> endobj 200 0 obj<> endobj 201 0 obj<>/ProcSet[/PDF/Text]/ExtGState<>>> endobj 202 0 obj<> endobj 203 0 obj<> endobj 204 0 obj<> endobj 205 0 obj<> endobj 206 0 obj<> endobj 207 0 obj<> endobj 208 0 obj<> endobj 209 0 obj<>stream 1 0 obj Ash from plants burning other fuels (wood chips, tires, trash) blended with coal. Class F fly ash is pozzolanic, with little or no cementing value alone. 199. 0000002453 00000 n 202-366-4000, Federal Highway Administration Research and TechnologyCoordinating, Developing, and Delivering Highway Transportation Innovations. ASTM C618 specifies a maximum of 34 percent retained on a 0.045 mm (No. 0000002125 00000 n Recycling and Use of Waste Materials and By-Products in Highway Construction - Volume 2. H|Mk@+ABVz&\*48Ac{Gu}! _wWo!lGpaoEy2TdfQ b^eQ'9-S#Sly`j-JENa9FLvdVrMo< :YbTJpq't. ASTM C595-92a. 163, Silver Spring, Maryland, April, 1981. xZYo8~7/ @qlvI!vi9VIIlv7:b.zu{zu|zi{qXuy[=\^2Y+.$[//?2[m5+^/44x(o j[qyq!w';mS1r`8DH J3S55Lo)K^Zp%66sKv1c]c}|H+&pEyv|%I:s:>n)>Az0o|$7+ 3`.

Placement and handling of fly ash concrete is in most respects similar to that of normal concrete. 0000005299 00000 n Fly ash to be used in concrete should be monitored by a quality assurance/quality control (QA/QC) program that complies with the recommended procedures in ASTM C311. 195 0 obj <> endobj However, because some fly ashes (including some Class C fly ashes) may have appreciable amounts of soluble alkalis, it is necessary to test materials to be used in the field to ensure that expansion due to alkali-silica reactivity will be reduced to safe levels.(8). 0000011766 00000 n The ACI mix proportioning guidelines recommend a separate trial mix for each 5-percent increment in the replacement of Portland cement by fly ash. xb```f``e`a``b`@ r4@"%xZ~?uO;um)[{d_aA`&Gq0Jtppe,&>@Z `O1fS6/&D?3003YU00@{K1"h` *30 (5) Normal procedures for screeding, finishing, edging, and jointing of conventional PCC are also applicable to fly ash concrete. (8), Bleeding: Bleeding is usually reduced because of the greater volume of fines and lower required water content for a given degree of workability. Mid-Atlantic Regional Technical Committee of the National Ready-Mix Concrete Association, Silver Spring, Maryland, 1993. Fly ash can also be interground with cement clinker or blended with Portland cement to produce blended cements. ACI 211.4R-93. ]5 @!4@(&ePi% AT1 0000012109 00000 n 4f!IT`ZB/K!,oF_."OXT~vrFA QXx kPS|yy^w{O'F--uW1_/ ;w|Gyl1/]'qQ]tYzimG{.F$be.GV8$SXo8G6; "Use of High-Volume Class F Fly Ash for Structural-Grade Concrete,". Resistance to Freeze-Thaw: As with all concretes, the resistance of fly ash concrete to damage from freezing and thawing depends on the adequacy of the air void system, as well as other factors, such as strength development, climate, and the use of deicer salts. 2 0 obj When fly ash is used as a separately batched material, trial mixes should be made using a water-cement plus fly ash (w/c+f) ratio, sometimes referred to as the water-cementitious ratio, instead of the conventional w/c ratio.(16). Certain fly ashes will reduce the effectiveness of air entraining agents, requiring a higher dosage to meet specifications. Ash from plants using oil as a supplementary fuel. (8) Class F fly ashes are generally more effective than Class C fly ashes in reducing the heat of hydration. (3), At the time of this survey, at least eight states did not permit the use of fly ash in either bridge deck or structural concrete.

Some of the properties of fly ash-concrete mixes that are of particular interest include mix workability, time of setting, bleeding, pumpability, strength development, heat of hydration, permeability, resistance to freeze-thaw, sulfate resistance, and alkali-silica reactivity. Moisture Content: ASTM C618 specifies a maximum allowable moisture content of 3.0 percent. "Standard Specification for Blended Hydraulic Cements," American Society for Testing and Materials, Annual Book of ASTM Standards, Volume 04.02, West Conshohocken, Pennsylvania, 1994. Permeability: Fly ash reacting with available lime and alkalies generates additional cementitious compounds that act to block bleed channels, filling pore space and reducing the permeability of the hardened concrete. xbbd``b`:$f $M@+HA% 3Hbx4&H/#n?c/ : <> American Society for Testing and Materials, Annual Book of ASTM Standards, Volume 04.02, West Conshohocken, Pennsylvania, 1994. Coal fly ash has been successfully used in Portland cement concrete (PCC) as a mineral admixture, and more recently as a component of blended cement, for nearly 60 years. Some of the engineering properties of fly ash that are of particular interest when fly ash is used as an admixture or a cement addition to PCC mixes include fineness, LOI, chemical composition, moisture content, and pozzolanic activity. Slump testing of fly ash concrete can be done at the same frequency as for normal PCC mixes. The coal ash industry is developing comparative information on the characteristics and engineering properties of ASTM C618 sources of fly ash before and after installation of low NOx burners. Some fly ash sources do not have acceptable LOI values once low NOx burners have been installed and put into operation. %%EOF In theory, the reaction between the very small particles of amorphous silica glass in the fly ash and the alkalis in the Portland cement, as well as the fly ash, ties up the alkalis in a nonexpansive calcium-alkali-silica gel, preventing them from reacting with silica in aggregates, which can result in expansive reactions. Thus, the temperature rise in large masses of concrete (such as dams) can be significantly reduced if fly ash is substituted for cement, since more of the heat can be dissipated as it develops. (5), The main precautions usually associated with the use of fly ash in concrete include somewhat slower early strength development, extended initial setting time, possible difficulty in controlling air content, seasonal limitations during winter months, and quality control of fly ash sources.(5). endstream endobj 211 0 obj<>stream Procedures for proportioning fly ash concrete mixes differ slightly from those for conventional concrete mixes. 0000008336 00000 n When a Type IP (Portland-pozzolan) or Type I-PM blended cement is used in a concrete mix, fly ash is already a part of the cementing material. Sulfate Resistance: Class F fly ash will generally improve the sulfate resistance of any concrete mixture in which it is included. 0000002282 00000 n (9) Both Class F and Class C fly ashes are beneficial in the production of high-strength concrete. %PDF-1.3 (12), Alkali-Silica Reactivity: Class F fly ash has been effective in inhibiting or reducing expansive reactions resulting from the alkali-silica reaction. Collins, Robert J. and Stanley K. Ciesielski. "Guide for Selecting Properties for High-Strength Concrete with Portland Cement and Fly Ash," ACI Manual of Concrete Practice, Part 1. Furthermore, consistent LOI values are almost as important as low LOI values to ready-mix producers, who are most concerned with consistent and predictable quality. HdSM0W1JPj7U=Pp6T PpMC?S,$n~. 5xJOhP`>h$s^xRH)WAJk2"y^nweBIuF Dunstan, E. R., Jr. "A Possible Method for Identifying Fly Ashes That Will Improve Sulfate Resistance of Concrete," Cement, Concrete and Aggregates, Volume 2, No. 197 0 obj<>stream When fly ash is used as a mineral admixture, the ready-mix producer typically handles fly ash in the same manner as Portland cement, except that fly ash must be stored in a separate silo from the Portland cement. Not only is the risk of thermal cracking reduced, but greater ultimate strength is attained in concrete with fly ash because of the pozzolanic reaction. endobj (10), Mix design procedures for normal, as well as high-strength, concrete involve a determination of the total weight of cementitious materials (cement plus fly ash) for each trial mixture that is being investigated in the laboratory. ASTM C39. The air content of the concrete must be carefully checked and adjusted during production to ensure that it remains within those limits. A. In a concrete mix design, the water-cement (w/c) ratio is a key design parameter, with a typical range being from 0.37 to 0.50. (19) Trial usage of high percentage fly ash concrete mixes is needed in order to be able to evaluate the field performance of these mixes. To ensure the quality of fly ash for use in PCC, the following sources of ash should be avoided: The net result of all these restrictions is that only a relatively low percentage (25 to 30 percent, at most) of all the coal fly ash produced annually is even potentially suitable for use in PCC. Fly ash, especially Class F fly ash, is effective in three ways in substantially reducing alkali-silica expansion: 1) it produces a denser, less permeable concrete; 2) when used as a cement replacement it reduces total alkali content by reducing the Portland cement; and 3) alkalis react with fly ash instead of reactive silica aggregates. Users of Class C fly ash are cautioned to carefully evaluate the long-term volume stability of concrete mixes in the laboratory prior to field use, with ASTM C441(15) as a suggested method of test. xUmO0+4u~I Uj)IU$*>J~>NH|\r4BXBx Lb8c4Y\5%zT&7\V\kd: u>RrGPmy]-^]{uLI}4aoqwm%9Ng|+uYmr\cCxZzJR2-uO&YR8b x4N~dzF1k3fx80p@g6F&}IsNU5"_u!(tL; |XyMV-URfpAW_wQ"3g,iWMN0GCQY]lw:{.".SCv5[=|nL>cL?d~>">Vr0$v8qm]qHW8!tx0=%lnMWr9I*Vq^&-#' IB7m? To ensure that such is the case, air content testing of fly ash concrete mixes may initially need to be done at a greater frequency than with normal PCC mixes. <> As an admixture, fly ash functions as either a partial replacement for, or an addition to, Portland cement and is added directly into ready-mix concrete at the batch plant. Heat of Hydration: The initial impetus for using fly ash in concrete stemmed from the fact that the more slowly reacting fly ash generates less heat per unit of time than the hydration of the faster reacting Portland cement. Many state transportation agencies, through their own program of sampling and testing, have been able to prequalify sources of fly ash within their own state (or from nearby states) for acceptance in ready-mixed concrete. Collins, Robert J. and Stanley K. Ciesielski. Recycling and Use of Waste Materials and By-Products in Highway Construction, National Cooperative Highway Research Program Synthesis of Highway Practice No. xref <> 4 0 obj 199, Transportation Research Board, Washington, DC, 1994. 0000006481 00000 n The most important quality control consideration concerning the use of fly ash in PCC mixes is to ensure that the air content of the freshly mixed concrete is within specified limits and does not fluctuate to any greater extent than a normal PCC mix. 0000012026 00000 n ASTM C441. Rather than relying on a cut-off date, the percentage of fly ash could be reduced during colder weather, or other measures (such as additional Portland cement, or the possible use of high-early strength cement, or a chemical accelerator) could be taken to maintain or improve strength development under low temperature conditions. SP040.01T, Skokie, Illinois, 1987. ] )$ZRdKFC&fCfH?3e,&~:xJ)$9.

(8) The increased volume of fines and reduced water content also play a role. 0000008734 00000 n Normal construction practices for cold weather concreting (such as heated aggregates and mixing water, reducing the slump of the concrete, covering the poured concrete with insulation material, and using space heaters for inside pours) are also applicable for concrete containing some fly ash.(18). endobj x@,g 5PHII"llwXRDFaL PLi iFbh(AT208P' A)u@ZMi3100L-w8,=%Td ##\3 1>=5~ ASTM C204. 95 0 obj<>stream Cold-Weather Concreting.

H|TM0W=JT%V]{ 6mJ!cg4 KdoJR W@{tSZ~o4G.8lfD-p@m P^jQ@ys)JM@E\Hc,"1CFI/ e@S*t9]~{W6"--H.4lB@j:7#/o+fnmwze (4g+aKy)jd0&|}Do~z}w'wGJEFd6Vti=_[ooeMb^O\Gw`_05 a2fQe ~`L[ Ni9K;ItR/]o Ses|65Uuwzp=8s x There is no need to add more fly ash to a concrete mix in which blended cement is being used, and it is recommended that no fly ash be added in such cases. "Fly Ash in Roadway Construction," Proceedings of the First Ash Utilization Symposium. HtTNA+8#w"AdoQYG)TDd=0g}fLkL0LW. Loss on Ignition: Many state transportation departments specify a maximum LOI value that does not exceed 3 or 4 percent, even though the ASTM criteria is a maximum LOI content of 6percent. As a result, finishing operations may have to be delayed, possibly by 1 to 2 hours, depending on the temperature. Concrete mixes are designed by selecting the proportions of the mix components that will develop the required strength, produce a workable consistency concrete that can be handled and placed easily, attain sufficient durability under exposure to in-service environmental conditions, and be economical. The increased ratio of solids volume to water volume produces a paste with improved plasticity and more cohesiveness. However, some Class C fly ashes may have little effect on, or possibly even decrease, the time of setting. The use of Class F fly ash usually results in slower early strength development, but the use of Class C fly ash does not and may even enhance early strength development. 0000007888 00000 n "Standard Methods of Sampling and Testing Fly Ash or Natural Pozzolans for Use as a Mineral Admixture in Portland Cement Concrete." Normal curing practices should be adequate for concrete containing Class F fly ash. Portland Cement Association, Publication No. endobj Some states, such as Wisconsin, have a construction cut-off date beyond which fly ash is not permitted to be used in concrete until the following spring. % 195 36 Current specifications include a requirement for the maximum allowable percentage retained on a 0.045 mm (No. A 1992 survey of all 50 state transportation agencies indicated that 40 states have had experience in the use of fly ash as a mineral admixture in concrete, usually as a partial replacement for Portland cement, although a number of states have also used blended Portland-pozzolan cement. 127, Transportation Research Board, Washington, DC, 1986.

As with any concrete, excessive vibration should be avoided because it may reduce the air content of the in-place concrete.(5). 0000011978 00000 n Guide to Alkali-Aggregate Reactivity. One mix design approach commonly used in proportioning fly ash concrete mixes is to use a mix design with all Portland cement, remove some of the Portland cement, and then add fly ash to compensate for the cement that is removed. An improved means of classifying and specifying fly ash sources for use as a mineral admixture in PCC is needed. <<11afc172887ded458feca726ca04124f>]>> Workability: At a given water-cement ratio, the spherical shape of most fly ash particles permits greater workability than with conventional concrete mixes. If fly ash is to replace Portland cement on an equal weight (1:1) basis, the total weight of cementitious material in each trial mix will remain the same. (6) These procedures establish standards for methods of sampling and frequency of performing tests for fineness, loss on ignition (LOI), specific gravity, and pozzolanic activity such that the consistency of a fly ash source can be certified. xb```b`` a`e``vcc@ >'E&B4^TQ^ofoRaai>O73wG}:`e^5&Ik5;(8eTGOEBmsJKn*]zGb@iXtH^0$2o,qur6 YX{SS4Nm.0qE3 XqeTr+S4zJ,(dJ!15`x 0000005869 00000 n 0000005539 00000 n Some Class C fly ashes are as effective as Portland cement in developing 28-day strength.

)3jJi| %1(!,Xub (U)S%:;8}6Xe:]GF:C(UE(BN~0 Fly ashes must have a low enough LOI (usually less than 3.0 percent) to satisfy ready-mix concrete producers, who are concerned about product quality and the control of air-entraining admixtures. Use of Fly Ash in Concrete. 1200 New Jersey Avenue, SEWashington, DC 20590 Delays in setting time will probably be more pronounced, compared with conventional concrete mixes, during the cooler or colder months. endstream endobj 212 0 obj<>stream (14) Class F fly ashes are probably more effective than Class C fly ashes because of their higher silica content, which can react with alkalis. endstream endobj 78 0 obj<>stream 0000005053 00000 n (5) There are some states that require that fly ash be added in certain mixes with no reduction in cement content. 87 0 obj<]/Info 73 0 R/Filter/FlateDecode/W[1 2 1]/Index[74 22]/DecodeParms<>/Size 96/Prev 132005/Type/XRef>>stream 8VSXNILaV;ZX%h"$HF.@eMX4nf5!j.U$|]vH64L2Y uM GYIgMYjZb}+)cHg)PyjlI L A2)IIijVs]z,~x>Y3f6$UA= 74 0 obj <> endobj x]%5r}8/^3J~,m2nq)I[sPRz+%~|qyhIb=zvQ]WE/9_EY}Ucw(q>8uYeQpYLj~.4\GT]Sme7(y4*mFW#GJh_~{Kkh_5EMUOTjn]9g\9kWt,Uq=`i(s9$uHTE;j>f2G/2b@MeyVu15SGr`jn$}#epT?R:??fSS]>%{7|2t;W$ZNv_"ua$3Bzew]=ve_kQfo%J QWh5u~|h^v[0[S5>V?1pXB5>C!a3^xDS0xnesx'&/{[kje uZmat_B_pOy%.0* &Rj~Yur: Hester, J. The mix design procedures stipulated in ACI 211.1 provide detailed, step-by-step directions regarding trial mix proportioning of the water, cement (or cement plus fly ash), and aggregate materials. Therefore, the concrete producer must ensure that the proper amount of air entraining admixture is added during mixing, so that the air content of the concrete is within specified limits. Naik, Tarun R., Vasanthy Sivasunduram, and Shiw S. Singh. For structural concrete, the design strength is usually the unconfined compressive strength as determined by ASTM C39. IS154.06T, Skokie, Illinois, 1980, Page Owner: Office of Research, Development, and Technology, Office of Safety, RDT, TRT Terms: Waste products as road materials--Handbooks, manuals, etc, Pavements, Asphalt concrete--Design and construction--Handbooks, manuals, etc, Pavements, Concrete--Design and construction--Handbooks, manuals, etc, Pavements--Additives--Handbooks, manuals, etc, Fills (Earthwork)--Design and construction--Handbooks, manuals, etc, Roads--Base courses--Design and construction--Handbooks, manuals, etc, Wastes, Environmental impacts, Recycling, Coordinating, Developing, and Delivering Highway Transportation Innovations, User Guidelines for Waste and Byproduct Materials in Pavement Construction. The slower strength development of concrete containing Class F fly ash may require that the moisture be retained in the concrete for a longer period of time than what is normally required for conventional concrete.