Minimum Fly Ash Cement Replacement To Mitigate Alkali Silica Reaction

L. J. Malvar1, L. R. Lenke 2 1U.S. Navy, Naval Facilities Engineering Service Center, Port Hueneme, CA; 2University of New Mexico, Albuquerque, NM

Keywords: alkali silica reaction, ASR, concrete, durability, fly ash, calcium oxide. ABSTRACT

Alkali silica reaction (ASR) in concrete results in deleterious expansion and deterioration.

For a given aggregate and a given cement, the potential for deleterious expansion can be assessed using ASTM C 1260. While recent specifications already address ASR prevention using recycled products, such as fly ashes as cement replacement, the restrictions on the fly ashes may be too conservative and prevent further savings during the replacement process by preventing the use of local ashes that do not meet current requirements. If a local fly ash is available, whether or not it meets ASTM or CSA requirements, the current study details a method to determine how much cement replacement would be needed to prevent significant expansion.

Data from previous research studies were used to assess the effectiveness of various fly ashes in preventing ASR, based on their chemical composition, the composition of the cement, and the reactivity of the aggregates. A chemical index was derived to characterize the fly ash and cement based on their chemical constituents, which was optimized to maximize the correlation with the test data. For the fly ashes, this index, Cfa, correlated well with the ASTM C 618 and CSA A3001 classifications. This index was also used to assess the efficiency of other ashes that did not meet either specification.

For a given aggregate reactivity, a given cement, and a given ash, it was possible to derive the minimum cement replacement that is needed to insure a 90% confidence that the 14-day ASTM C 1260 expansion would remain below 0.08%.

INTRODUCTION

A recent state-of-the-art review resulted in the development of guidelines to prevent ASR (Malvar et al., 2002), which are now being used by the Tri-Services (U.S. Navy, Air Force, and Army) for airfield pavements, and are being exported into Department of Defense (DOD) unified facilities guide specifications dealing with concrete in general. However, these guidelines are

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2005 World of Coal Ash (WOCA), April 11-15, 2005, Lexington, Kentucky, USA http://www.flyash.info

somewhat conservative, and only allow the use of ASTM C 618 Class F fly ashes with additional restrictions. As a result, many ashes very close to, but not meeting that specification cannot be used, in some cases increasing concrete costs by requiring transporting better ashes from far away. The objective of this paper is to address and refine the fly ash requirements using the fly ash chemical composition, and to provide an alternate classification to ASTM C 618 that would allow the usage of ashes currently not meeting that specification. It is believed that this new classification will allow for increased use of fly ash in concrete.

RESEARCH SIGNIFICANCE

Public Law 106-398 (2001) directs the Secretary of Defense to explore available technologies capable of preventing, treating, or mitigating ASR. To date 32 DOD airfields have reported ASR problems. The costs are staggering. As an example the concrete apron at the Air National Guard Channel Islands Site was built in 1989, and was replaced in 2003 at a cost of about $14 million. While recent specifications now address ASR prevention using recycled products such as fly ashes as cement replacement, the restrictions on the ashes may be too conservative and prevent further savings during the replacement process.

BACKGROUND ASR and AAR

Alkali silica reaction (ASR) is the reaction between the alkali hydroxide in Portland

cement and certain siliceous rocks and minerals present in the aggregates, such as opal, chert, chalcedony, tridymite, cristobalite, strained quartz, etc. The products of this reaction often result in significant concrete expansion and cracking, and ultimately failure of the concrete structure, including significant potential for foreign object damage to aircraft (see Helmuth et al., 1993, or Thomas, 1996, for details on the chemical reactions). Alkali aggregate reaction (AAR) is the reaction between the cement hydroxides and mineral phases in the aggregates, which are usually of siliceous origin. In this paper no distinction is made between AAR and ASR. The ASR reaction needs several components to take place: alkali (supplied by the cement, although external sources can exist), water (or high moisture content or humidity), and a reactive aggregate.

ASR Mitigation Using Fly Ash There are 3 characteristics of a fly ash that determine its efficiency in preventing alkali-

silica reaction:

- Fineness – It has been shown that finer pozzolans are more efficient in reducing ASR expansion. For example, Malhotra and Ramezanianpour (1994) state: “fineness of fly ashes is one of the most important physical properties affecting pozzolanic activity.” Ravina (1980) and Bérubé et al. (1995) found a direct correlation between fineness and ASR mitigation. Ultra fine fly ash (UFFA), with particle sizes around 3 microns, has also

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proven to be very effective, in spite of a slightly higher CaO content around 11.8% (Obla et al., 2003). Finally, raw silica fume, with particle sizes around 0.1 micron, is also very effective in preventing ASR.

- Mineralogy – While ashes can be characterized by their basic chemical components, those components can be bound differently and react differently from ash to ash. For example, Mehta (1986a) showed the importance of mineralogy in mitigating sulfate attack.

- Chemistry – This approach has already been used with success (e.g., Shehata and Thomas, 2000; Thomas and Shehata, 2004), and constitutes one starting point of the current investigation (Malvar et al., 2003).

In general, for a given ash, the chemical composition is easily obtained, but not the

fineness (except for its compliance with ASTM C 618), or its mineralogy. While the correlation sought is mainly between the chemical composition and the ASTM C 1260 14-day expansion, if all ashes studied conform to ASTM C 618, the variation in fineness between them will be limited (except for a few exceptions such as UFFA), and this factor will be less important in the correlation. In the following correlations, each chemical constituent of the fly ash and cement is weighted based on their relative percentages (by weight) in the blend, and their molar equivalent. In addition, each chemical constituent, or group thereof, can be weighted using an additional factor (e.g., α and β below), which would also carry information on the reactivity of the constituent, or group thereof. This may explain why previous models based on chemical analysis have already provided some good correlations (e.g., Shehata and Thomas, 2000; Thomas and Shehata, 2004). This is the method used here to assess the effects of fly ash (and cement) chemical composition on ASR mitigation.

PREVIOUS TESTS Data was gathered from previous research addressing the use of fly ash in mitigating ASR. Data from 6 research studies were particularly examined, as summarized below. A general correlation was sought between the chemical composition of the ash and the cement, and the 14-day expansion following the ASTM C 1260 test method (also called the accelerated mortar bar test, or AMBT). For cementitious blends of cement and fly ash, ASTM C 1260 was typically modified to represent the blend (this is now addressed in ASTM C 1567). Fly ash and cement compositions for all 6 studies are shown in Tables 1 and 2, respectively. For the first 5 data sets, the 14-day expansions with the aggregates tested using cement alone are presented in Table 3, while the 14-day expansions with ash substitution are tabulated in Table 4. The expansion data for the sixth set (Rangaraju and Sompura, 2005) is shown in Tables 5a and 5b for cements C1 and C2, respectively. While data from the first 5 studies were used to calibrate the model (see Malvar and Lenke, 2005), the last data set (by Rangaraju and Sompura) was used to verify the developed predictive model.

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McKeen, Lenke, and Pallachulla (1998, 2000) McKeen, Lenke, and Pallachulla (1998), and McKeen, Lenke, Pallachulla, and Barringer (2000) tested 5 fly ashes with 4 reactive aggregates and a single lot of Type I/II low-alkali cement (0.55% Na2Oeq, where Na2Oeq = Na2O + 0.658 K2O). AASHTO T 303 (similar to ASTM C 1260 and CSA A23.2-25A) was used to determine the 14-day expansion. The calcium oxide content (CaO) for the five ashes studied varied from 3.6 to 24.5%. Shehata and Thomas (2000) Shehata and Thomas (2000) tested 18 ashes and 2 cements, although only one high alkali cement (1.02% Na2Oeq) was used in the AMBT. The aggregate was a reactive siliceous limestone known as Spratt. The CaO content of the ashes varied from 5.6 to 30%. Based on the Canadian specifications (CSA A3001, 2003) (formerly CSA A23.5), the ashes were classified as a low lime Type F ash (CaO ≤ 8%), a medium lime Type CI ash (8% < CaO ≤ 20%), and high lime Type CH ash (CaO > 20%). Touma et al. (2000, 2001)

Touma, et al. (2000, 2001) evaluated a Type F ash (CaO = 12.3%) and a Type C ash (CaO = 26.1%) with six reactive aggregates and one Type I/II high alkali cement (1.14% Na2Oeq). It is worth noting that the Type C ash would be classified as a Type CH ash using the Canadian fly ash specification because of the relatively high CaO content. Shon, Zollinger, and Sarkar (2004) Shon, Zollinger, and Sarkar (2004) studied one Type C fly ash (CaO = 25.9%) with a medium alkali cement (0.65% Na2Oeq) using a reactive siliceous sand. Detwiler (2003)

Detwiler (2003) cites developed data using the 14-day AMBT with low, medium, and high CaO fly ashes (5.7%, 18.6%, 25.7%, respectively) and a Type I low alkali cement (0.43% Na2Oeq) using a single reactive quartzite aggregate.

Rangaraju, P.R., Sompura, K.R. (2005) Rangaraju and Sempura used two cements, one with 0.64% Na2Oeq (C1), and one with 0.24% Na2Oeq (C2) to assess the ASR potential of 89 different sources of fine aggregate in Minnesota. They used one Class F ash and one Class C ash to study their effectiveness in

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mitigating ASR, using the modified ASTM C 1260. Cement replacement by fly ash was a constant 20% by weigh of total cementitious.

EFFECT OF EACH CONSTITUENT ON ASTM C 1260 EXPANSION

In the studies considered, straight replacements of cement with fly ash were completed, so that the total cementitious material content remained the same. To take into account the effect of the total cementitious content, for each constituent the total amount available from both the ash and the cement was used. To allow for direct comparisons, the ASTM C 1260 14-day expansion of the mix with a blend of cement and fly ash replacement, denoted E14b, was normalized by the control 14-day expansion of the mix with cement only, denoted E14c. Hence the plots show the normalized 14-day expansion E14b/E14c as a function of the cementitious constituent. For each aggregate the control expansion with cement only, E14c, is shown in Table 3, and the expansions of the various blends of cement and ash, E14b, are shown in Table 4 (for the first 5 data sets).

The chemical constituents are divided into 2 groups: those that increase expansion, such as CaO, Na2O, K2O, MgO, and SO3, and those that reduce it, such as SiO2, Al2O3, and Fe2O3. The following observations were completed for the first 5 data sets (Malvar and Lenke, 2005).

Calcium Oxide (CaO) The fly ash content of calcium oxide (or lime) has already been shown to have the most effect on the capacity of the ash in mitigating ASR (Malvar et al., 2002; McKeen et al., 2000; Shehata and Thomas, 2000), and high amounts of CaO can be very deleterious. Current DOD guidelines for pavements do not allow Class C fly ash and limit the CaO content of Class F fly ash to 10% (Malvar et al., 2002). The New Mexico State Highway and Transportation Department (2000) places a 10% restriction as well. As mentioned earlier, current Canadian guidelines even classify fly ashes based on CaO content (CSA A3001, 2003), a classification that had supporters in the U.S. as well (e.g., Mehta, 1986b; ACI 232.2R, 1996).

A significant correlation is found between the normalized 14-day expansion and the CaO content of the mix with a coefficient of determination of R2 = 0.71 (Figure 1). In the ashes studied, the CaO content varied from about 3% for a Class F ash to 30% for a Class C ash (Table 1), and in the cements from about 63 to 65% (Table 2). Since the cement CaO content was fairly constant, the cementitious CaO variation is mostly due to the ash CaO content. Alkalis (Na2O and K2O) Sodium and potassium oxides have historically been grouped together and their content limited, both in the cement and the ashes. For reactive aggregates, it is recommended to use low-alkali cement (less than 0.6% content per ASTM C 150, 1997), and for the fly ashes, the available alkalis are often limited to 1.5% (Malvar et al., 2002; New Mexico, 2000). However, mixes with low-alkali cement and low-alkali ashes, and with large variation in the other constituents (such as CaO, SiO2, etc.) could be expected to show a low correlation between the

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alkali content and the ASTM C 1260 14-day expansion. In addition, this test has low sensitivity to alkalis in the mix, as indicated in the standard under the section on Significance and Use. This would explain, for example, how Thomas and Shehata (2004) found a good correlation between the parameter CaO/(SiO2)2 and mortar bar expansion independent of the alkali content. For the ashes studied herein, this insensitivity to the alkali content is also apparent in Figure 2, where there is no apparent correlation between the cementitious alkali content and the normalized expansion (R2 close to zero). Interestingly, the new ASTM C 618 (2003) no longer includes the 1.5% available alkali limit that was previously presented as a supplementary optional chemical requirement. However, for higher alkali content (e.g., two ashes in the data have more than 8% equivalent alkalis) a correlation might be apparent. Magnesium Oxide (MgO)

AASHTO M 295 (similar to ASTM C 618 and CSA A 23.5) used to require a 5% MgO limit in the fly ash to prevent deleterious expansion from the formation of magnesium hydroxide (ACAA, 1995) and this limit is still enforced, for example, by the New Mexico State Highway and Transportation Department (2000). This does not seem to be a problem for Class F fly ash, since the MgO content is typically very low (e.g., see Malhotra et al., 1994). Class C ashes are more likely to have a high MgO content (e.g., Malhotra et al., 1994; ACAA, 1995; Glauz et al., 1996). However, Mehta (1986b) indicated that the MgO in fly ash often occurs either in noncrystalline form, or in the form of nonexpansive melilite phase, so the correlation would be expected to be weak.

The correlation between the normalized 14-day expansion and the MgO content is shown in Figure 3. Since most ashes have a low MgO content (e.g., compared to the CaO content, see Table 1), the correlation is positive but very weak.

Sulfur Trioxide (SO3)

Sulfur trioxide is not often addressed when studying the effectiveness of an ash to mitigate ASR. SO3 is limited to a maximum of 5% in ASTM C 618 for both Class C and F ashes. Klieger and Gebler (1987) state that fly ashes inhibit ASR expansion with the most significant (inverse) correlations being those with MgO, SO3, and the ratio of CaO to SiO2. They further state that none of these are adequate predictors either by themselves or in combination. Figure 4 shows a moderate correlation (R2 = 0.50) between the normalized 14-day expansion and the cementitious SO3 content. Silicon Dioxide (SiO2) Silicon dioxide shows pozzolanic activity, i.e., forms a cementitious product by reaction with calcium hydroxide (Mehta, 1986b). Increased contents of SiO2 have proven to increase the effectiveness of ashes, and lower the expansion. Figure 5 shows a significant inverse correlation (R2 = 0.74) between the cementitious SiO2 content and the normalized 14-day expansion.

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Aluminum Trioxide (Al2O3)

Alumina can contribute to the pozzolanic effect of silica, and often the sum of SiO2 and Al2O3 has shown good correlation with pozzolanic activity (Malhotra and Ramezanianpour, 1994). Figure 6 shows a significant inverse correlation (R2 = 0.60) between the cementitious Al2O3 content and the normalized 14-day expansion. Iron Oxide (Fe2O3)

Malhotra and Ramezanianpour (1994) report that, in most ashes, most of the iron oxide is present as nonreactive hematite and magnetite, so a weak correlation would be expected. Some researchers have indicated that including the iron oxide together with the silicon and aluminum oxides did not improve the relationships (Malhotra and Ramezanianpour, 1994).

For the current data set, Figure 7 shows a very weak inverse correlation (R2 = 0.13) between the cementitious Fe2O3 content and the normalized 14-day expansion.

EFFECT OF CONSTITUENT COMBINATIONS ON EXPANSION Constituents Promoting Expansion

CaO has often been recognized as having the most deleterious effect on expansion, and expansion has often been correlated to CaO, or CaO/SiO2. Hence, other deleterious constituents, such as the alkalis, MgO, and SO3 were replaced by their CaO molar equivalents, yielding:

CaOeq = CaO + 0.905 Na2Oeq + 1.391 MgO + 0.700 SO3 (1)

If the alkalis are given separately, this would be equivalent to:

CaOeq = CaO + 0.905 Na2O + 0.595 K2O + 1.391 MgO + 0.700 SO3 (2)

The relation between normalized 14-day expansion and cementitious CaOeq is shown in Figure 8. The correlation (R2 = 0.78) is better than any previous correlation with a single constituent promoting expansion (Figures 1 to 4) or other combinations thereof (not shown here). Although there was no correlation between expansion and alkalis by themselves in the AMBT (Figure 2), including the alkalis as CaOeq does slightly improve the correlation in Figure 8, from R2 = 0.767 (not shown here) to 0.780. Constituents Reducing Expansion SiO2 is typically considered the most beneficial constituent in preventing expansion. Hence the Al2O3 and the Fe2O3 were replaced by their SiO2 equivalents:

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SiO2eq = SiO2 + 0.589 Al2O3 + 0.376 Fe2O3 (3)

Figure 9 shows a strong inverse correlation (R2 = 0.78) between expansion and cementitious SiO2eq, better than any previous correlation with a single component reducing expansion (Figures 5 to 7) or other combinations thereof (not shown here). Combination of All Constituents

Initially the normalized 14-day expansion was correlated to the ratio CaOeq/SiO2eq (using equations 1 and 3, or 2 and 3). This is shown in Figure 10, where the correlation (R2 = 0.83) is an improvement from the separate correlations with either CaOeq (Figure 8) or SiO2eq (Figure 9). In this figure the cementitious CaOeq/SiO2eq was normalized by the cement only CaOeq/SiO2eq to account for the various cements used.

In reality, the best fit would be nonlinear, perhaps trilinear, with two segments of almost zero slope at the beginning and end of the data (as shown in Thomas and Shehata, 2004). If a trilinear fit is used, with two short segments of zero slope where the normalized expansion is either 0 or 1, the fit in Figure 11 is obtained, with a correlation of R2 = 0.87. It should be noted that in the region where the normalized CaOeq/SiO2eq ratio tends to 1 (region of very low cement replacement levels), the normalized 14-day expansion E14b/E14c is approximated as constant and equal to 1, but it would be expected that actual test data would show some pessimums – in the first 5 data sets only one pessimum is apparent at a ratio of 0.75 and E14b/E14c = 1.06 (see also Table 4), but Rangaraju and Sompura’s data showed several pessimums in that region (Figure 13).

In order to account for different reactivity, each constituent should be weighted independently. In the current paper, this was simplified by including only 2 weight factors in the CaO and SiO2 equivalencies, and replacing the previous ratio CaOeq/SiO2eq with a so-called chemical index for the blend, Cb:

( )

)376.0589.0(700.0391.1595.0905.0

32322

322

2 OFeOAlSiOSOMgOOKONaCaO

SiOCaO

Cbeq

beqb ++

++++==

βα

β

α (4)

where α = 5.64 and β = 1.14 are optimal weighting factors for the constituents other than CaO or SiO2, based on the first 5 data sets.

Note that for a blend of for example 25% ash and 75% cement, the blend CaO content would be 0.25 times the CaO in the ash plus 0.75 times the CaO in the cement, or, in general W times the ash CaO plus (1-W) times the cement CaO, where W is the weight fraction of the ash constituent. For a blend with only cement (0% ash), the same chemical index can be defined, and is denoted Cc (Table 2), and similarly for a blend with only fly ash (100% ash), denoted Cfa (Table 6). For the Type I or II cements used in the studies, Cc shows little variation (Table 2).

In Figure 12, the normalized expansion is plotted as a function of the normalized cementitious chemical index, Cb/Cc, with the best correlation so far of R2 = 0.90. The values of the coefficients α and β were obtained by maximizing this coefficient of determination (R2) using the first 5 data sets.

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Fly Ash Chemical Index Table 6 classifies all the ashes studied by order of increasing chemical index, Cfa. It can be seen that, when compared to ASTM C 618 (2003), a value of Cfa < 1.3 usually represents a Class F ash, and values Cfa > 1.3 usually represent a Class C ash. When compared to the Canadian standard (CSA A3001, 2003), a value of Cfa < 0.5 usually represents a Canadian Class F ash, 0.5 < Cfa < 1.3 usually represents a Class CI ash, and values Cfa > 1.3 usually represent a Class CH ash. Hence the chemical index, Cfa, has a very good correlation with both standards. Comparison with Rangaraju and Sompura’s Tests

Figure 13 shows that this recent set of tests confirms the trend based on the first 5 sets. Although there is some scatter in the data points, they overlap previous results. In the future, this new set and other sets will be used to further optimize the coefficients α and β.

MINIMUM REQUIRED FLY ASH

For a given fly ash, a given cement, and a given aggregate reactivity, the objective is to determine the amount of fly ash for the mix to be non-reactive. This can be accomplished starting from Figure 12. The maximum ASTM C 1260 14-day expansion sought is 0.08% (Malvar et al., 2002), and if E14c is the AMBT expansion with cement only, then the maximum expansion sought in Figure 12 is 0.08/E14c. Entering 0.08/E14c on the y-axis gives a maximum value of Cb/Cc on the x-axis. Defining the inverse of the linear portion of Figure 12 as function “g” yields the following:

498.008.0439.008.0

1414

+⎟⎟⎠

⎞⎜⎜⎝

⎛=⎟⎟

⎠

⎞⎜⎜⎝

⎛=

ccc

b

EEg

CC (5)

However, from equation 4:

( ) ( )( ) ( )ceqfaeq

ceqfaeq

beq

beqb SiOWSiOW

CaOWCaOWSiOCaO

Cββ

αα

β

α

222 )1()1(

−+

−+== (6)

where W is the percent fly ash substitution by weight (expressed as a decimal), and

ceq

ceqc SiO

CaOC

β

α

2

= (7)

from which the required weight fraction of the ash can be derived as

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( )

( )cceq

faeq

ceq

faeq

c

EgSiOSiO

CaOCaO

EgW

142

2

14

/08.011

/08.01

⎟⎟⎠

⎞⎜⎜⎝

⎛−−⎟

⎟⎠

⎞⎜⎜⎝

⎛−

−=

β

β

α

α

(8)

This formula gives the minimum required fly ash substitution as a function of 5 inputs:

the ash chemistry (given by CaOeqαfa and SiO2eqβfa), the cement chemistry (given by CaOeqαc and SiO2eqβc), and the 14-day AMBT expansion with cement only (E14c). These 5 inputs can also be used to find the cement chemical index Cc using equation 7, and the fly ash chemical index Cfa, using equation 6 with W = 1. Once Cfa and Cc are calculated, and assuming that a single cement is used (Cc constant), W can be plotted as a function of E14c and Cfa. This is shown in Figure 13 for a cement with chemical index Cc = 4.

Figure 13 shows that the first 4 curves (0.0 ≤ Cfa ≤ 0.9) represent very good ASTM C 618 Class F ashes (Cfa = 0 represents a theoretical lower bound based on current data and data fit). A cement replacement of 25 to 40% (as recommended in Malvar et al., 2002) using these ashes could mitigate very reactive aggregates, with ASTM C 1260 14-day expansions of up to 0.9% (note that ASTM C 1260 indicates that expansions beyond 0.2% are deleterious, and between 0.1 and 0.2% possibly deleterious, see also BS 812-123, 1999). ASTM C 618 Class F ashes with 0.9 ≤ Cfa ≤ 1.3 could mitigate very reactive aggregates, but at replacements of up to 50%, depending on reactivity (i.e. E14c).

The same figure shows that ASTM C 618 Class C ashes (Cfa > 1.3) can only mitigate very low reactivity, and that higher replacements are needed. For example, a 40% cement replacement with a Class C ash with Cfa = 1.80 could only address a reactivity of up to E14c = 0.2%. On the other hand, this is a great benefit in that this chart would allow the use of some Class C ashes for the case of low reactivity. This also concurs with the practice of using Class C ash with innocuous aggregates (e.g., New Mexico, 2000).

The minimum replacement from Figure 13 is based on using the best fit to the data in Figure 12 (i.e. with a 50% confidence level). Instead of using this best fit, it is recommended to use the 90% confidence level, which, in Figure 13, is represented by a line parallel to the best fit and to the left of it, and intersecting the x-axis at Cb/Cc = 0.44. If this line is used, Figure 14 is obtained, which gives the minimum required replacement with a confidence of 90% that the expansion will be less than the stipulated 0.08%. Although this figure was developed for a typical cement with Cc = 4, other cements in this study did not vary much from this value (Cc varied from 3.72 to 4.25 as shown in Table 2). Hence Figure 14 could be used as a good approximation for determining the minimum percent replacement for typical cements (for a more accurate determination a new figure would need to be drawn for each cement).

It should be kept in mind, that although this method can be used to calculate minimum amounts of fly ash cement replacement to mitigate ASR, in general it would be advisable to use absolute minimum replacements depending on the application, whether or not the aggregates are reactive. For example the U.S. Navy requires a minimum of 25% Class F fly ash in pavements independently of reactivity (Malvar et al., 2002), the New Mexico State Highway and Transportation Department (2000) requires 20% Class F minimum, or 25% Class C minimum if the aggregate is innocuous, and similar absolute minimums are proposed elsewhere, depending on the application (e.g., 20 to 30% Class F fly ash in Canada for general concrete in warm weather, see Cheung and Foo, 1999). The concept behind these absolute minimums, even with innocuous aggregates, is that the resulting concrete will, in general, be cheaper and more durable.

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CLASSIFICATION USING THE CHEMICAL INDEX

As indicated earlier, the fly ash chemical index Cfa has a good correlation with ASTM C 1260. Table 6 shows that only ashes DM and BDII appear reversed compared to the ASTM classification. However, it can be seen from Table 1 that BDII has 8.45% Na2Oeq compared to 2.25% for DM.

When compared to the Canadian standard, the chemical index shows good agreement as well, with a couple of exceptions (Table 6). For example ash MN is a CI but appears within the Canadian Type F ashes: this ash has SiO2+Al2O3+Fe2O3 = 86.3% and almost no SO3 and no alkalis – it is a very good ash, and arguably should be an F ash. The Canadian standard (CSA A3001, 2003) actually allows classifying it as an F ash, since its CaO content of 8.68% can be considered less than 8±2% (the standard states: “For the purpose of classification the tolerance shall be ±2% on the CaO limits”). Fly ashes BR and TB appear within the CH ashes in Table 6 but are classified only as CI: this is due to their high contents of MgO and SO3, and very high alkalis (in excess of 8.4%), in addition to a borderline CaO content very close to the 20% threshold for CH. Hence, in spite of their CI classification, they are even less efficient in mitigating expansion than several CH ashes. The Canadian standard (CSA A3001, 2003) would actually allow classifying BR as a CH ash (since its CaO content of 18.85% can be considered more than 20±2%).

The chemical index can also be used to assess additional ashes that do not meet typical standards. For example, in Hawaii, cement is imported and is very expensive – if local ashes could be used to replace cement, this would provide considerable savings in addition to higher durability. Unfortunately the available ash at Barbers Point is neither a Type F nor a Type C per ASTM C 618, and is only a Type CI by the Canadian standard (see its composition in Table 7). For this ash the chemical index is 1.03, which makes it equivalent to an F ash in Table 6. From Figure 13, it can be seen that at a replacement of 40% this ash could mitigate even high reactivity, although for designing a mix, Figure 14 should be used, and, at that replacement level, it would be advisable to use it only on low to moderately reactive aggregates (e.g., E14c < 0.4). At a 25% replacement level, it could be used with aggregates of low reactivity (e.g., E14c < 0.15 in Figure 14). Another interesting ash is UFFA (Obla, et al., 2003), also shown in Table 7. While the most important characteristic of UFFA is its fineness, which is well below ASTM C 1260 requirements, its chemical composition includes 11.8% CaO, which makes it a CI ash in Canada, and would prevent its usage in some cases. Table 7 shows that its chemical index is 0.53, so that it has the equivalent chemistry of a good Class F fly ash for ASR mitigation (Table 6 also shows it would fall just between Canadian Types F and CI), in addition to the benefits of its fineness. In terms of updating current guidelines, Table 7 also shows an example of a theoretical threshold ash, that is, the worst ash that would be acceptable under current DOD guide specifications (Malvar et al., 2002). Its chemical index comes out to be 1.29, which is close to the 1.3 threshold between F and C ashes (see Table 6). This value could be used as a threshold to limit the usable ashes, however, it is recommended to use Figure 15 instead, which would allow even more ashes to be used with aggregates of low reactivity (as measured by ASTM C 1567).

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CONCLUSIONS Data from previous research studies were used to assess the effectiveness of fly ashes in preventing ASR, based on their chemical composition, the composition of the cement, and the reactivity of the aggregates. A chemical index was derived based on the fly ash (or cement) constituents, which was optimized to maximize the correlation with the test data. For the fly ashes, this index, Cfa, correlated well with the ASTM C 618 and CSA A3001 fly ash classifications. This index was also used to assess the efficiency of other ashes that did not meet either specification. This methodology should allow for the safe use of many additional ashes, while further reducing concrete costs. For a given aggregate reactivity, a given cement, and a given ash, it was possible to derive the minimum cement replacement that is needed to insure a 90% confidence that the 14-day AMBT expansion would remain below 0.08%.

ACKNOWLEDGMENTS The first author was supported by the Naval Facilities Engineering Command mission

funding for the Technical Center of Expertise for Pavement Design. The second author was supported by the Office of Naval Research and the American Society for Engineering Education (ONR-ASEE) Summer Faculty Fellowship Program during his stay at the Naval Facilities Engineering Service Center.

REFERENCES AASHTO M 295 (2000), “Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in Concrete,” Standard Specifications for Transportation Materials and Methods of Sampling and Testing: Part I – Specifications, American Association of State Highway and Transportation Officials.

AASHTO T 303 (2000), “Accelerated Detection of Potentially Deleterious Expansion of Mortar Bars Due to Alkali-Silica Reaction,” Standard Specifications for Transportation Materials and Methods of Sampling and Testing: Part II – Tests, American Association of State Highway and Transportation Officials.

ACAA (1995), “Fly Ash Facts for Highway Engineers,” Federal Highway Administration Report FHWA-SA-94-081, American Coal Ash Association, Washington, D.C.

ACI 232.2R (1996), Use of Fly Ash in Concrete, American Concrete Institute, Farmington Hills, MI.

12

ASTM C 150 (1997), “Standard Specification for Portland Cement,” American Society for Testing and Materials.

ASTM C 618 (2003), “Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in Concrete,” American Society for Testing and Materials.

ASTM C 1260 (2001), “Standard Test Method for Potential Alkali Reactivity of Aggregates (Mortar-Bar Method),” American Society for Testing and Materials.

ASTM C 1567 (2004), “Standard Test Method for Determining the Potential Alkali-Silica Reactivity of Combinations of Cementitious Materials and Aggregate (Accelerated Mortar-Bar Method),” American Society for Testing and Materials.

Bérubé, M.A., Carles, A., Duchesne, J., Naproux, P. (1995), “Influence of Particle Size Distribution on the Effectiveness of Type-F Fly Ash in Suppressing Expansion Due to Alkali-Silica Reactivity” Fifth CANMET/ACI International Conference on Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, Milwaukee, USA, ACI SP-153, pp. 177-192.

BS 812-123 (1999), “Testing Aggregates – Method for Determination of Alkali-Silica Reactivity, Concrete Prism Method,” British Standards Institution.

Cheung, M., Foo, S. (1999), “Use of Fly Ash or Slag in Concrete: Proposed PWGSC Guidelines,” CANMET/ACI International Symposium on Concrete Technology for Sustainable Development, Vancouver, British Columbia, Canada.

CSA A23.2-25A (2000), “Test Method for Detection of Alkali Silica Reactive Aggregate by Accelerated Expansion of Mortar Bars,” Canadian Standards Association, Toronto, Ontario, CA.

CSA A3001 (2003), “Cementitious Materials for Use in Concrete,” Canadian Standards Association, CSA International, Toronto, Ontario, CA.

Detwiler, R.J. (2003), “PCA’s Guide Specification for Concrete Subjected to Alkali-Silica Reactions: Mitigation Measures,” PCA R&D Serial No. 2407, Portland Cement Association, Skokie, IL.

Glauz, D.L., Roberts, D., Jain, V., Moussavi, H., Llewellen, R., Lenz, B. (1996), “Evaluate the Use of Mineral Admixtures in Concrete to Mitigate Alkali-Silica Reactivity,” Report FHWA/CA/OR-97-01, Office of Materials Engineering and Testing Services, California Department of Transportation.

Helmuth, R., Stark, D., Diamond, S., Moranville-Regourd, M. (1993), “Alkali-Silica Reactivity: An Overview of Research,” SHRP-C-342, Strategic Highway Research Program, National Research Council, Washington, D.C.

Klieger, P., and Gebler, S., “Fly Ash and Concrete Durability,” Concrete Durability: Katharine and Bryant Mather International Conference, SP100-56, J.M. Scanlon, ed., American Concrete Institute, Detroit, MI, pp. 1043-1069.

Malhotra, V.M., Ramezanianpour, A.A. (1994), “Fly Ash in Concrete,” MSL 94-45(IR), CANMET, Canada Center for Mineral and Energy Technology, Natural Resources Canada, Ottawa, Ontario, Canada.

13

Malvar, L.J., Cline, G.D., Burke, D.F., Rollings, R., Sherman, T.W., Greene, J. (2002), “Alkali Silica Reaction Mitigation: State-of-the-Art and Recommendations,” ACI Materials Journal, Vol. 99, No. 5, pp. 480-489.

Malvar, L.J., Cline, G.D., Burke, D.F., Rollings, R., Sherman, T.W., Greene, J. (2003), Closure to the Discussion of “Alkali Silica Reaction Mitigation: State-of-the-Art and Recommendations,” ACI Materials Journal, Vol. 100, No. 4, pp. 346-350.

Malvar, L.J., Lenke, L.R. (2005), “Efficiency of Fly Ash in Mitigating Alkali Silica Reaction Based on Chemical Composition,” submitted to ACI Materials Journal.

McKeen, R.G., Lenke, L.R., Pallachulla, K.K. (1998), “Mitigation of Alkali Silica Reactivity in New Mexico,” ATR Institute, Materials Research Center, University of New Mexico, Albuquerque, NM.

McKeen, R. G., Lenke, L. R., Pallachulla, K. K., Barringer, W. L. (2000), “Mitigation of Alkali-Silica Reactivity in New Mexico,” Transportation Research Record, No. 1698, pp. 9-16.

Mehta, P.K. (1986a), “Effect of Fly Ash Composition on Sulfate Resistance of Cement,” ACI Journal, Vol. 83, No. 6, November/December, pages 994-1000.

Mehta, P.K. (1986b), “Standard Specifications for Mineral Admixtures – An Overview,” 2nd CANMET/ACI International Conference on Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, Madrid, Spain, ACI SP-91, pp. 637-658.

New Mexico State Highway and Transportation Department (2000), Specifications for Portland Cement Concrete, Section 510, Standard Specifications for Highway and Bridge Construction, State Construction Bureau, Santa Fe, NM.

Obla, K.H., Hill, R.L., Thomas, M.D.A., Shashiprakash, S.G., and Perebatova, O. (2003), “Properties of Concrete Containing Ultra Fine Fly Ash”, ACI Materials Journal, Vol. 100, No. 5, pp. 426-433.

Ravina, D. (1980), “Optimized Determination of PFA (fly ash) fineness with reference to pozzolanic activity,” Cement and Concrete Research, Vol. 10, pp. 573-580.

Rangaraju, P.R., Sompura, K.R. (2005), “A Study on Influence of Alkali Content of Cement on Expansions Observed in the Standard and Modified ASTM C 1260 Procedures,” Transportation Research Board 84th Annual Meeting, Washington, D.C.

Shehata, M.H., Thomas, M.D.A. (2000), "The Effect of Fly Ash Composition on the Expansion of Concrete due to Alkali Silica Reaction," Cement and Concrete Research, Vol. 30, pp. 1063-1072.

Shon, C.-S., Zollinger, D. G., Sarkar, S. L. (2004), “Evaluation of ASR Resistance of Fly Ash-Slag Combinations Using the Modified ASTM C 1260 Test Method,” Eighth CANMET/ACI International Conference on Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, SP-221, V.M. Malhotra, ed., American Concrete Institute, Farmington Hills, MI, pp. 249-264.

Thomas, M.D.A. (1996), “Review of the Effect of Fly Ash and Slag on Alkali-Aggregate Reaction in Concrete,” BRE Report 314, British Research Establishment, London, U.K.

14

Thomas, M.D.A., Shehata, M.H. (2004), "Use of Blended Cements to Control Expansion of Concrete due to Alkali Silica Reaction," Eight CANMET/ACI International Conference on Flyash, Silica Fume, Slag, and Natural Pozzolans, Supplementary Papers, Las Vegas, NV, pp. 591-607.

Touma, W.E., Suh, C., Fowler, D.W., Carrasquillo, R.L., Folliard, K.J. (2000), “Alkali Silica Reaction in Portland Cement Concrete: Testing Procedures and Mitigation Methods,” 11th International Conference on Alkali Aggregate Reaction, Québec City, Canada, pp. 513-522.

Touma, W.E., Fowler, D.W., Carrasquillo, R.L. (2001), “Alkali Silica Reaction in Portland Cement Concrete: Testing Methods and Mitigation Alternatives,” Research Report ICAR 301-1F, International Center for Aggregates Research, 520 pp.

15

Table 1. Fly ash composition

Fly Ash Study a Type SiO2 Al2O3 Fe2O3 CaO SO3 MgO Na2Oeq Cfa

LG S&T F 41.96 19.64 20.07 5.57 0.95 1.19 2.30 0.48FM S&T F 47.34 22.34 15.08 6.38 1.43 0.82 1.41 0.37MN S&T F 61.50 20.52 4.29 8.68 0.19 1.70 0.56 0.33

BD II S&T F 45.66 21.42 5.53 12.34 0.84 2.76 8.45 1.29SD I S&T F 50.92 23.64 4.62 13.63 0.23 0.86 3.77 0.59SD II S&T F 51.56 22.90 4.58 15.15 0.28 1.16 2.80 0.58TB S&T C 40.68 21.19 4.50 15.87 2.18 3.54 8.46 1.68C1 S&T F 44.29 20.96 5.23 17.51 2.13 4.21 1.68 1.11

WM S&T C 39.77 21.46 5.69 18.46 1.86 3.77 4.14 1.35BR S&T C 32.71 19.02 5.76 18.85 4.81 4.30 8.73 2.42PI S&T C 38.42 20.57 5.64 20.50 1.76 4.39 3.05 1.42C2 S&T C 39.83 19.56 5.54 21.53 2.14 4.62 1.94 1.38EW S&T C 38.22 18.43 5.72 24.61 1.55 4.72 1.68 1.44PP S&T C 35.20 18.72 6.06 26.61 2.49 5.12 1.83 1.71IN S&T C 36.12 18.64 6.07 26.62 1.80 5.41 1.60 1.65

OK I S&T C 34.60 16.45 7.13 27.71 2.71 5.89 1.65 1.91OK II S&T C 31.65 16.65 7.28 29.10 3.17 6.57 1.85 2.23

CC S&T C 41.12 11.24 5.93 30.00 2.13 4.40 2.26 1.654-Corners (4F) NM F 62.56 25.10 4.68 2.81 0.00 0.81 2.40 0.26Coronado (CF NM F 63.37 22.26 5.34 3.60 0.02 1.06 2.53 0.31Escalante (EF) NM F 61.34 25.11 4.42 4.94 0.08 1.09 1.25 0.25Esc/Tolk (ET) b NM F 50.19 22.25 4.68 14.73 0.59 3.23 1.67 0.76

Tolk (TC) NM C 39.04 19.39 4.94 24.51 1.10 5.36 2.08 1.50Low CaO (DL) Detwiler F 44.80 23.54 16.98 5.66 1.22 1.26 2.07 0.46Med CaO (DM) Detwiler C 41.00 21.50 6.03 18.62 1.10 4.62 2.25 1.22High CaO (DH) Detwiler C 34.68 19.51 5.81 25.74 1.94 6.00 2.35 1.84

F-Ash (IF) Touma F 56.50 19.30 4.70 12.30 1.50 2.30 0.30 0.53C-Ash (IC) Touma C 34.99 20.55 6.24 26.12 1.74 4.65 1.18 1.47C-Ash (SC) Shon C 35.20 21.60 5.40 25.90 1.40 4.80 1.20 1.45

F-Ash Rangaraju F 43.53 20.94 9.68 8.36 1.37 1.79 0.85 0.52C-Ash Rangaraju C 36.11 17.25 6.53 22.47 1.44 5.62 1.42 1.57

a S&T: Shehata and Thomas (2000); NM: McKeen, et al. (2000); Detwiler: Detwiler (2003); Touma: Touma, et al. (2001); Shon: Shon, et al. (2004); Rangaraju: Rangaraju et al. (2005).

b 50/50 blend of two ashes: Escalante Type F and Tolk Type C.

16

Table 2. Portland cement composition and chemical index Cc

Cement Type Study a SiO2 Al2O3 Fe2O3 CaO SO3 MgO Na2Oeq Cc

High Alkali S&T 20.83 5.11 2.01 62.98 3.25 2.43 1.02 3.98 Low Alkali NM 21.10 4.30 3.20 63.90 3.00 2.00 0.55 3.72 Low Alkali Detwiler 20.87 4.53 2.28 63.99 2.34 3.86 0.43 4.25 High Alkali Touma 20.90 4.43 3.01 62.65 3.06 2.97 1.14 4.13 Med Alkali Shon 19.12 5.07 3.40 64.73 3.13 0.64 0.65 3.56

Med Alkali C1 Rangaraju 19.91 5.35 2.47 62.78 3.27 2.71 0.64 4.08 Low Alkali C2 Rangaraju 20.75 3.72 3.86 65.50 2.87 0.92 0.24 3.42 a S&T: Shehata & Thomas (2000); NM: McKeen, et al. (2000); Detwiler: Detwiler (2003);

Touma: Touma, et al. (2001); Shon: Shon, et al. (2004); Rangaraju: Rangaraju et al. (2005).

17

Table 3. Aggregate sources and AMBT control expansion, first 5 data sets.

Aggregate Name

Aggregate Code

Study a Control Expansion E14c (%) b

Spratt SP S&T 0.3710 Albuquerque AL c NM 0.8013 Albuquerque AL c NM 0.7993 d

Placitas PL NM 0.8060 Placitas PL NM 0.7850 d

Mimbres MI NM 0.4923 Mimbres MI NM 0.4947 d

Santa Ana SA NM 0.5343 Santa Ana SA NM 0.4173 d

Quartzite DET Detwiler 0.2500 New Mexico NM c Touma 0.9100

Idaho ID Touma 0.7900 Iowa IA Touma 0.4200

Wyoming WY Touma 0.2900 South Dakota SD Touma 0.1700

Virginia VA Touma 0.1500 Siliceous Sand SH Shon 0.2450

a S&T: Shehata & Thomas (2000); NM: McKeen, et al. (2000); Detwiler: Detwiler (2003); Touma: Touma, et al. (2001); Shon: Shon, et al. (2004).

b Control expansion using Portland cement only. c Same source: Albuquerque (Shakespeare).

18

Table 4. AMBT expansion data for blends, E14b, and controls, E14c, first 5 sets. Ash (%) AMBT

Exp. (%) Ash (%) AMBT Exp. (%) Ash (%) AMBT

Exp. (%) Ash (%) AMBT Exp. (%)

SP-Agg. 0.3710 a SD I (15) 0.1450 WM (40) 0.1150 IN (15) 0.3370 LG (25) 0.1030 SD I (20) 0.1110 WM (50) 0.0370 IN (25) 0.2380 FM (15) 0.1830 SD I (25) 0.0770 BR (25) 0.2760 OK I (30) 0.2890 FM (20) 0.1680 SD II (15) 0.0710 PI (25) 0.0690 OK I (45) 0.1660 MN (15) 0.0650 SD II (25) 0.0240 C2 (25) 0.2830 OK I (60) 0.0760 MN (25) 0.0220 TB (25) 0.2010 EW (30) 0.2170 OK II (25) 0.2920

BD II (20) 0.2020 C1 (25) 0.1540 EW (40) 0.1530 CC (25) 0.2400 BD II (30) 0.1480 WM (20) 0.1520 EW (50) 0.1020 --- --- BD II (40) 0.0890 WM (30) 0.1310 PP (15) 0.3230 --- --- NM-Agg. 0.9100 a ID-Agg. 0.7900 a IA-Agg. 0.4200 a WY-Agg. 0.2900 a

IF (15) 0.3200 IF (15) 0.2900 IF (15) 0.2500 IF (15) 0.1800 IF (25) 0.1200 IF (25) 0.1000 IF (25) 0.0500 IF (25) 0.0500 IC (20) 0.4900 IC (20) 0.4100 IC (20) 0.3600 IC (20) 0.2400

IC (27½) 0.2900 IC (27½) 0.2200 IC (27½) 0.2200 IC (27½) 0.1600 IC (35) 0.2000 IC (35) 0.1400 IC (35) 0.1100 IC (35) 0.1000

SD-Agg. 0.1700 a VA-Agg. 0.1500 a SH-Agg. 0.2450 a DET-Agg. 0.2500 aIF (15) 0.1300 IF (15) 0.0700 SC (15) 0.1890 DL (15) 0.0900 IF (25) 0.0400 IF (25) 0.0300 SC (20) 0.1430 DL (25) 0.0300 IC (20) 0.1800 c IC (20) 0.1400 SC (25) 0.1310 DM (15) 0.1700

IC (27½) 0.1000 IC (27½) 0.0800 SC (30) 0.0760 DM (25) 0.1600 IC (35) 0.0700 IC (35) 0.0600 SC (35) 0.0420 DH (15) 0.2000

--- --- --- --- SC (50) 0.0360 DH (25) 0.1800 --- --- --- --- SC (70) 0.0080 --- ---

AL-Agg. 0.8013 a PL-Agg. 0.8060 a MI-Agg. 0.4923 a SA-Agg. 0.5343 aAL-Agg. 0.7993 a, b PL-Agg. 0.7850 a, b MI-Agg. 0.4947 a, b SA-Agg. 0.4173 a, b

EF (12) 0.3990 EF (12) 0.4193 EF (12) 0.2380 EF (12) 0.1603 EF (24) 0.1127 EF (24) 0.1207 EF (12) b 0.2753 EF (24) 0.0370 EF (36) 0.0290 EF (24) b 0.1327 EF (24) 0.0613 EF (36) 0.0033 CF (12) 0.3433 EF (36) 0.0113 EF (36) 0.0177 CF (12) 0.1823 CF (24) 0.1073 CF (12) 0.4423 CF (12) 0.1883 CF (12) b 0.1957 CF (36) 0.0330 CF (24) 0.2080 CF (24) 0.0980 CF (24) 0.0487 4F (12) 0.3470 CF (36) 0.0393 CF (36) 0.0147 CF (36) 0.0063 4F (24) 0.0513 4F (12) 0.3610 4F (12) 0.1923 4F (12) 0.1393 4F (36) 0.0001 4F (24) 0.0837 4F (24) 0.0590 4F (24) 0.0143 TC (12) 0.7217 4F (24) b 0.0817 4F (36) 0.0287 4F (36) 0.0190 TC (24) 0.4960 4F (36) 0.0120 TC (12) 0.4587 TC (12) 0.3973 TC (36) 0.3563 TC (12) 0.6227 TC (24) 0.3043 TC (24) 0.3200 ET (12) 0.6973 TC (24) 0.5537 TC (36) 0.1627 TC (36) 0.1507 ET (24) 0.2360 TC (36) 0.3580 ET (12) 0.3237 ET (12) 0.3547 ET (36) 0.0997 TC (36) b 0.2870 ET (24) 0.1510 ET (24) 0.1225

--- --- TC (36) b 0.2923 ET (36) 0.0630 ET (36) 0.0400 --- --- ET (12) 0.5490 --- --- --- --- --- --- ET (24) 0.3203 --- --- --- --- --- --- ET (36) 0.0973 --- --- --- ---

a Control expansion with cement only, E14c; b Replicates; c Pessimum expansion

19

Table 5a. AMBT expansion for blends, E14b, and controls, E14c, Rangaraju et al. 2005 (C1). Cementitious

Material* 14-Day Exp (%)

CementitiousMaterial*

14-Day Exp (%)

CementitiousMaterial*

14-Day Exp (%)

CementitiousMaterial*

14-Day Exp (%)

CementitiousMaterial*

14-Day Exp (%)

CementitiousMaterial*

14-Day Exp (%)

Control #1 0.026 Control #16 0.120 Control #31 0.146 Control #46 0.173 Control #61 0.208 Control #76 0.231 #1 w-FA-F 0.027 #16 w-FA-F 0.024 #31 w-FA-F 0.076 #46 w-FA-F 0.062 #61 w-FA-F 0.060 #76 w-FA-F 0.033 #1 w-FA-C 0.035 #16 w-FA-C 0.087 #31 w-FA-C 0.112 #46 w-FA-C 0.134 #61 w-FA-C 0.167 #76 w-FA-C 0.184 Control #2 0.077 Control #17 0.125 Control #32 0.147 Control #47 0.174 Control #62 0.208 Control #77 0.232 #2 w-FA-F 0.041 #17 w-FA-F 0.074 #32 w-FA-F 0.072 #47 w-FA-F 0.085 #62 w-FA-F 0.070 #77 w-FA-F 0.059 #2 w-FA-C 0.078 #17 w-FA-C 0.120 #32 w-FA-C 0.132 #47 w-FA-C 0.126 #62 w-FA-C 0.157 #77 w-FA-C 0.248 Control #3 0.088 Control #18 0.127 Control #33 0.148 Control #48 0.180 Control #63 0.210 Control #78 0.237 #3 w-FA-F 0.060 #18 w-FA-F 0.051 #33 w-FA-F 0.058 #48 w-FA-F 0.088 #63 w-FA-F 0.043 #78 w-FA-F 0.096 #3 w-FA-C 0.072 #18 w-FA-C 0.087 #33 w-FA-C 0.131 #48 w-FA-C 0.126 #63 w-FA-C 0.160 #78 w-FA-C 0.184 Control #4 0.102 Control #19 0.127 Control #34 0.149 Control #49 0.182 Control #64 0.211 Control #79 0.243 #4 w-FA-F 0.046 #19 w-FA-F 0.059 #34 w-FA-F 0.071 #49 w-FA-F 0.076 #64 w-FA-F 0.033 #79 w-FA-F 0.083 #4 w-FA-C 0.086 #19 w-FA-C 0.106 #34 w-FA-C 0.120 #49 w-FA-C 0.164 #64 w-FA-C 0.163 #79 w-FA-C 0.171 Control #5 0.103 Control #20 0.128 Control #35 0.150 Control #50 0.182 Control #65 0.212 Control #80 0.243 #5 w-FA-F 0.058 #20 w-FA-F 0.060 #35 w-FA-F 0.047 #50 w-FA-F 0.054 #65 w-FA-F 0.060 #80 w-FA-F 0.063 #5 w-FA-C 0.088 #20 w-FA-C 0.104 #35 w-FA-C 0.169 #50 w-FA-C 0.157 #65 w-FA-C 0.158 #80 w-FA-C 0.169 Control #6 0.104 Control #21 0.133 Control #36 0.158 Control #51 0.184 Control #66 0.212 Control #81 0.247 #6 w-FA-F 0.049 #21 w-FA-F 0.056 #36 w-FA-F 0.046 #51 w-FA-F 0.064 #66 w-FA-F 0.080 #81 w-FA-F 0.087 #6 w-FA-C 0.088 #21 w-FA-C 0.116 #36 w-FA-C 0.126 #51 w-FA-C 0.141 #66 w-FA-C 0.169 #81 w-FA-C 0.188 Control #7 0.106 Control #22 0.137 Control #37 0.158 Control #52 0.185 Control #67 0.214 Control #82 0.249 #7 w-FA-F 0.055 #22 w-FA-F 0.075 #37 w-FA-F 0.068 #52 w-FA-F 0.055 #67 w-FA-F 0.082 #82 w-FA-F 0.080 #7 w-FA-C 0.093 #22 w-FA-C 0.127 #37 w-FA-C 0.117 #52 w-FA-C 0.139 #67 w-FA-C 0.218 #82 w-FA-C 0.197 Control #8 0.106 Control #23 0.137 Control #38 0.158 Control #53 0.186 Control #68 0.216 Control #83 0.261 #8 w-FA-F 0.055 #23 w-FA-F 0.020 #38 w-FA-F 0.063 #53 w-FA-F 0.067 #68 w-FA-F 0.074 #83 w-FA-F 0.032 #8 w-FA-C 0.093 #23 w-FA-C 0.116 #38 w-FA-C 0.153 #53 w-FA-C 0.146 #68 w-FA-C 0.163 #83 w-FA-C 0.245 Control #9 0.107 Control #24 0.137 Control #39 0.161 Control #54 0.190 Control #69 0.216 Control #84 0.263 #9 w-FA-F 0.062 #24 w-FA-F 0.047 #39 w-FA-F 0.054 #54 w-FA-F 0.076 #69 w-FA-F 0.085 #84 w-FA-F 0.080 #9 w-FA-C 0.087 #24 w-FA-C 0.109 #39 w-FA-C 0.138 #54 w-FA-C 0.157 #69 w-FA-C 0.172 #84 w-FA-C 0.224 Control #10 0.110 Control #25 0.138 Control #40 0.161 Control #55 0.193 Control #70 0.217 Control #85 0.263 #10 w-FA-F 0.056 #25 w-FA-F 0.069 #40 w-FA-F 0.073 #55 w-FA-F 0.054 #70 w-FA-F 0.075 #85 w-FA-F 0.019 #10 w-FA-C 0.100 #25 w-FA-C 0.126 #40 w-FA-C 0.128 #55 w-FA-C 0.158 #70 w-FA-C 0.158 #85 w-FA-C 0.244 Control #11 0.111 Control #26 0.140 Control #41 0.163 Control #56 0.198 Control #71 0.217 Control #86 0.268 #11 w-FA-F 0.018 #26 w-FA-F 0.079 #41 w-FA-F 0.084 #56 w-FA-F 0.080 #71 w-FA-F 0.083 #86 w-FA-F 0.086 #11 w-FA-C 0.095 #26 w-FA-C 0.117 #41 w-FA-C 0.138 #56 w-FA-C 0.154 #71 w-FA-C 0.176 #86 w-FA-C 0.207 Control #12 0.113 Control #27 0.141 Control #42 0.164 Control #57 0.199 Control #72 0.218 Control #87 0.270 #12 w-FA-F 0.066 #27 w-FA-F 0.059 #42 w-FA-F 0.062 #57 w-FA-F 0.072 #72 w-FA-F 0.066 #87 w-FA-F 0.074 #12 w-FA-C 0.096 #27 w-FA-C 0.143 #42 w-FA-C 0.141 #57 w-FA-C 0.141 #72 w-FA-C 0.148 #87 w-FA-C 0.235 Control #13 0.115 Control #28 0.144 Control #43 0.164 Control #58 0.199 Control #73 0.218 Control #88 0.273 #13 w-FA-F 0.081 #28 w-FA-F 0.035 #43 w-FA-F 0.068 #58 w-FA-F 0.060 #73 w-FA-F 0.053 #88 w-FA-F 0.089 #13 w-FA-C 0.107 #28 w-FA-C 0.149 #43 w-FA-C 0.122 #58 w-FA-C 0.161 #73 w-FA-C 0.232 #88 w-FA-C 0.275 Control #14 0.118 Control #29 0.145 Control #44 0.164 Control #59 0.202 Control #74 0.218 Control #89 0.308 #14 w-FA-F 0.069 #29 w-FA-F 0.058 #44 w-FA-F 0.065 #59 w-FA-F 0.070 #74 w-FA-F 0.016 #89 w-FA-F 0.058 #14 w-FA-C 0.103 #29 w-FA-C 0.127 #44 w-FA-C 0.133 #59 w-FA-C 0.178 #74 w-FA-C 0.161 #89 w-FA-C 0.305 Control #15 0.118 Control #30 0.146 Control #45 0.167 Control #60 0.204 Control #75 0.219 #15 w-FA-F 0.040 #30 w-FA-F 0.035 #45 w-FA-F 0.067 #60 w-FA-F 0.029 #75 w-FA-F 0.096 #15 w-FA-C 0.101 #30 w-FA-C 0.121 #45 w-FA-C 0.121 #60 w-FA-C 0.284 #75 w-FA-C 0.164 * Controls have no replacement, others have 20% replacement with either F or C ash.

20

Table 5b. AMBT expansion for blends, E14b, and controls, E14c, Rangaraju et al. 2005 (C2). Cementitious

Material* 14-Day Exp (%)

CementitiousMaterial*

14-Day Exp (%)

CementitiousMaterial*

14-Day Exp (%)

CementitiousMaterial*

14-Day Exp (%)

CementitiousMaterial*

14-Day Exp (%)

CementitiousMaterial*

14-Day Exp (%)

Control #1 0.036 Control #16 0.148 Control #31 0.185 Control #46 0.198 Control #61 0.226 Control #76 0.233 #1 w-FA-F 0.024 #16 w-FA-F 0.014 #31 w-FA-F 0.049 #46 w-FA-F 0.040 #61 w-FA-F 0.029 #76 w-FA-F 0.028 #1 w-FA-C 0.039 #16 w-FA-C 0.106 #31 w-FA-C 0.146 #46 w-FA-C 0.158 #61 w-FA-C 0.178 #76 w-FA-C 0.199 Control #2 0.075 Control #17 0.172 Control #32 0.181 Control #47 0.204 Control #62 0.256 Control #77 0.266 #2 w-FA-F 0.032 #17 w-FA-F 0.038 #32 w-FA-F 0.038 #47 w-FA-F 0.046 #62 w-FA-F 0.080 #77 w-FA-F 0.040 #2 w-FA-C 0.074 #17 w-FA-C 0.131 #32 w-FA-C 0.151 #47 w-FA-C 0.151 #62 w-FA-C 0.185 #77 w-FA-C 0.237 Control #3 0.090 Control #18 0.149 Control #33 0.236 Control #48 0.226 Control #63 0.218 Control #78 0.241 #3 w-FA-F 0.035 #18 w-FA-F 0.021 #33 w-FA-F 0.040 #48 w-FA-F 0.047 #63 w-FA-F 0.026 #78 w-FA-F 0.045 #3 w-FA-C 0.085 #18 w-FA-C 0.116 #33 w-FA-C 0.196 #48 w-FA-C 0.169 #63 w-FA-C 0.158 #78 w-FA-C 0.166 Control #4 0.148 Control #19 0.181 Control #34 0.153 Control #49 0.230 Control #64 0.239 Control #79 0.242 #4 w-FA-F 0.030 #19 w-FA-F 0.029 #34 w-FA-F 0.031 #49 w-FA-F 0.068 #64 w-FA-F 0.051 #79 w-FA-F 0.032 #4 w-FA-C 0.117 #19 w-FA-C 0.108 #34 w-FA-C 0.134 #49 w-FA-C 0.155 #64 w-FA-C 0.178 #79 w-FA-C 0.205 Control #5 0.118 Control #20 0.158 Control #35 0.171 Control #50 0.204 Control #65 0.208 Control #80 0.264 #5 w-FA-F 0.038 #20 w-FA-F 0.041 #35 w-FA-F 0.038 #50 w-FA-F 0.035 #65 w-FA-F 0.030 #80 w-FA-F 0.051 #5 w-FA-C 0.092 #20 w-FA-C 0.113 #35 w-FA-C 0.162 #50 w-FA-C 0.152 #65 w-FA-C 0.158 #80 w-FA-C 0.160 Control #6 0.138 Control #21 0.187 Control #36 0.174 Control #51 0.175 Control #66 0.246 Control #81 0.244 #6 w-FA-F 0.034 #21 w-FA-F 0.022 #36 w-FA-F 0.024 #51 w-FA-F 0.040 #66 w-FA-F 0.038 #81 w-FA-F 0.043 #6 w-FA-C 0.110 #21 w-FA-C 0.119 #36 w-FA-C 0.146 #51 w-FA-C 0.135 #66 w-FA-C 0.181 #81 w-FA-C 0.178 Control #7 0.136 Control #22 0.178 Control #37 0.169 Control #52 0.223 Control #67 0.241 Control #82 0.288 #7 w-FA-F 0.032 #22 w-FA-F 0.036 #37 w-FA-F 0.030 #52 w-FA-F 0.027 #67 w-FA-F 0.032 #82 w-FA-F 0.036 #7 w-FA-C 0.114 #22 w-FA-C 0.148 #37 w-FA-C 0.133 #52 w-FA-C 0.154 #67 w-FA-C 0.205 #82 w-FA-C 0.187 Control #8 0.136 Control #23 0.138 Control #38 0.171 Control #53 0.221 Control #68 0.219 Control #83 0.354 #8 w-FA-F 0.032 #23 w-FA-F 0.034 #38 w-FA-F 0.034 #53 w-FA-F 0.044 #68 w-FA-F 0.038 #83 w-FA-F 0.027 #8 w-FA-C 0.114 #23 w-FA-C 0.131 #38 w-FA-C 0.169 #53 w-FA-C 0.167 #68 w-FA-C 0.165 #83 w-FA-C 0.297 Control #9 0.122 Control #24 0.130 Control #39 0.229 Control #54 0.236 Control #69 0.239 Control #84 0.276 #9 w-FA-F 0.036 #24 w-FA-F 0.034 #39 w-FA-F 0.039 #54 w-FA-F 0.042 #69 w-FA-F 0.035 #84 w-FA-F 0.030 #9 w-FA-C 0.099 #24 w-FA-C 0.128 #39 w-FA-C 0.182 #54 w-FA-C 0.161 #69 w-FA-C 0.182 #84 w-FA-C 0.228 Control #10 0.142 Control #25 0.196 Control #40 0.176 Control #55 0.199 Control #70 0.233 Control #85 0.352 #10 w-FA-F 0.022 #25 w-FA-F 0.027 #40 w-FA-F 0.052 #55 w-FA-F 0.042 #70 w-FA-F 0.048 #85 w-FA-F 0.008 #10 w-FA-C 0.116 #25 w-FA-C 0.170 #40 w-FA-C 0.157 #55 w-FA-C 0.163 #70 w-FA-C 0.170 #85 w-FA-C 0.347 Control #11 0.161 Control #26 0.170 Control #41 0.217 Control #56 0.211 Control #71 0.227 Control #86 0.268 #11 w-FA-F 0.009 #26 w-FA-F 0.038 #41 w-FA-F 0.029 #56 w-FA-F 0.046 #71 w-FA-F 0.035 #86 w-FA-F 0.037 #11 w-FA-C 0.126 #26 w-FA-C 0.143 #41 w-FA-C 0.152 #56 w-FA-C 0.164 #71 w-FA-C 0.184 #86 w-FA-C 0.193 Control #12 0.125 Control #27 0.143 Control #42 0.194 Control #57 0.230 Control #72 0.218 Control #87 0.296 #12 w-FA-F 0.038 #27 w-FA-F 0.034 #42 w-FA-F 0.028 #57 w-FA-F 0.041 #72 w-FA-F 0.028 #87 w-FA-F 0.031 #12 w-FA-C 0.112 #27 w-FA-C 0.119 #42 w-FA-C 0.148 #57 w-FA-C 0.175 #72 w-FA-C 0.141 #87 w-FA-C 0.185 Control #13 0.157 Control #28 0.185 Control #43 0.208 Control #58 0.206 Control #73 0.271 Control #88 0.273 #13 w-FA-F 0.032 #28 w-FA-F 0.021 #43 w-FA-F 0.032 #58 w-FA-F 0.028 #73 w-FA-F 0.027 #88 w-FA-F 0.046 #13 w-FA-C 0.134 #28 w-FA-C 0.138 #43 w-FA-C 0.153 #58 w-FA-C 0.141 #73 w-FA-C 0.201 #88 w-FA-C 0.216 Control #14 0.141 Control #29 0.151 Control #44 0.207 Control #59 0.255 Control #74 0.227 Control #89 0.302 #14 w-FA-F 0.038 #29 w-FA-F 0.029 #44 w-FA-F 0.031 #59 w-FA-F 0.028 #74 w-FA-F 0.040 #89 w-FA-F 0.036 #14 w-FA-C 0.125 #29 w-FA-C 0.134 #44 w-FA-C 0.142 #59 w-FA-C 0.191 #74 w-FA-C 0.162 #89 w-FA-C 0.291 Control #15 0.137 Control #30 0.214 Control #45 0.208 Control #60 0.287 Control #75 0.245 #15 w-FA-F 0.028 #30 w-FA-F 0.031 #45 w-FA-F 0.046 #60 w-FA-F 0.048 #75 w-FA-F 0.065 #15 w-FA-C 0.147 #30 w-FA-C 0.166 #45 w-FA-C 0.138 #60 w-FA-C 0.231 #75 w-FA-C 0.194 * Controls have no replacement, others have 20% replacement with either F or C ash.

21

Table 6. Fly ash type and chemical index Cfa

Fly Ash Name Study a Chemical Index, of Fly Ash, Cfa

Ash Type (ASTM)

Ash Type (CSA)

Escalante F (EF) NM 0.25 F F Four Corners F (4F) NM 0.26 F F

Coronado F (CF) NM 0.31 F F MN S&T 0.33 F CI FM S&T 0.37 F F

Detwiler Low CaO (DL) Detwiler 0.46 F F LG S&T 0.48 F F

Rangaraju F-Ash Rangaraju 0.52 F CI Touma F (IF) Touma 0.53 F CI

SD II S&T 0.58 F CI SD I S&T 0.59 F CI

Escalante F/Tolk C (ET)b NM 0.76 F CI C1 S&T 1.11 F CI

Detwiler Med CaO (DM) Detwiler 1.22 C CI BD II S&T 1.29 F CI WM S&T 1.35 C CI C2 S&T 1.38 C CH PI S&T 1.42 C CH

EW S&T 1.44 C CH Shon C (SC) Shon 1.45 C CH

Touma C (IC) Touma 1.47 C CH Tolk C (TC) NM 1.50 C CH

Rangaraju C-Ash Rangaraju 1.57 C CH IN S&T 1.65 C CH CC S&T 1.65 C CH TB S&T 1.68 C CI PP S&T 1.71 C CH

Detwiler High CaO (DH) Detwiler 1.84 C CH OK I S&T 1.91 C CH OK II S&T 2.23 C CH

BR S&T 2.42 C CI a S&T: Shehata & Thomas (2000); NM: McKeen, et al. (2000); Detwiler: Detwiler (2003);

Touma: Touma, et al. (2001); Shon: Shon, et al. (2004); Rangaraju: Rangaraju et al. (2005). b 50/50 blend of two ashes.

22

Table 7. Composition of example fly ashes

Fly Ash Name

SiO2 Al2O3 Fe2O3 CaO SO3 MgO Na2Oeq Cfa

Barbers Point 43.47 18.42 6.30 15.72 6.56 1.45 1.40 1.03 UFFA 50.66 27.24 3.06 11.80 1.03 2.51 0.35 0.53

Threshold F 40.0 20.0 10.0 8.0 5.0 5.0 1.5 1.29

23

y = 0.0447x - 1.9070R2 = 0.7143

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 10 20 30 40 50 60 7Cementitious CaO (%)

0

Figure 1 – Effect of cementitious CaO content on 14-day AMBT expansion.

y = -0.1018x + 0.5604R2 = 0.0251

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5Cementitious Na2Oeq (%)

Figure 2 – Effect of cementitious alkali content on 14-day AMBT expansion.

24

y = 0.1008x + 0.1948R2 = 0.0552

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0Cementitious MgO (%)

Figure 3 – Effect of cementitious MgO content on 14-day AMBT expansion.

y = 0.6472x - 1.2287R2 = 0.5000

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.0 1.0 2.0 3.0 4.0Cementitious SO3 (%)

Figure 4 – Effect of cementitious SO3 content on 14-day AMBT expansion.

25

y = -0.0679x + 2.2718R2 = 0.7409

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 10 20 30 4Cementitious SiO2 (%)

0

Figure 5 – Effect of cementitious SiO2 content on 14-day AMBT expansion.

Figure 6 – Effect of cementitious Al2O3 content on 14-day AMBT expansion.

y = -0.1115x + 1.3806R2 = 0.6038

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 5 10 15 20Cementitious Al2O3 (%)

Nor

mal

ized

Exp

ansi

on

26

y = -0.1986x + 1.1472R2 = 0.1313

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.0 2.0 4.0 6.0 8.0Cementitious Fe2O3 (%)

Figure 7 – Effect of cementitious Fe2O3 content on 14-day AMBT expansion.

y = 0.0457x - 2.2502R2 = 0.7799

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 20 40 60 8Cementitious CaOeq (%)

0

Figure 8 – Effect of equivalent CaO content on 14-day AMBT expansion.

27

y = -0.0546x + 2.2548R2 = 0.7834

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 10 20 30 40 5Cementitious SiO2eq (%)

0

Figure 9 – Effect of equivalent SiO2 content on 14-day AMBT expansion.

y = 1.7309x - 0.6879R2 = 0.8287

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.00 0.20 0.40 0.60 0.80 1.00Normalized Cementitious CaOeq/SiO2eq

Figure 10 – Effect of normalized CaOeq/SiO2eq ratio on 14-day AMBT expansion.

28

y = 2.1216x - 0.9389

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.00 0.20 0.40 0.60 0.80 1.00Normalized Cementitious CaOeq/SiO2eq

Cementitious (Linear Portion)

Cementitious (Zero-Slope Portion)

R2 = 0.8671 (thru all data)

Figure 11 – Effect of normalized CaOeq/SiO2eq ratio on 14-day AMBT expansion.

y = 2.2788x - 1.1343

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.00 0.20 0.40 0.60 0.80 1.00Cb/Cc

Cementitious (Linear Portion)Cementitious (Zero-Slope Portion)

R2 = 0.9026 (thru all data)

Figure 12 – Effect of Cb/Cc ratio on 14-day AMBT expansion.

29

All Data14-Day A.M.B.T. vs. Cementitious Composition

(CaO)eq : Calculated Equivalent (SO3 , MgO, (Na2O)eq)(SiO2)eq : Calculated Equivalent (Al2O3, Fe2O3)

α = 5.64, β = 1.14

y = 2.2788x - 1.1343R2 = 0.7767

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00Cb/Cc

14-D

ay N

orm

aliz

ed E

xpan

sion

, % Cementitious (Linear Portion)Cementitious (Non-Linear Portion)Rangaraju DataLinear (Cementitious (Linear Portion))

R2 = 0.9026(Malvar & Lenke data)

90% Conf. Bandy = 2.2788x - 1.0027

F-as

h /

HA

PC-C

1

F-as

h /

LA

PC-C

2

C-a

sh /

HA

PC-C

1

C-a

sh /

LA

PC-C

2

F-ash /HAPC-C1Control

F-ash /LAPC-C2Control

C-ash /HAPC-C1Control

C-ash /LAPC-C2Control

Figure 13 – Comparison with Rangaraju and Sompura’s data.

30

0

10

20

30

40

50

60

70

80

0.0 0.2 0.4 0.6 0.8 1.0E14c (cement only, Cc = 4) (%)

Min

imum

Fly

Ash

Rep

lace

men

t (%

) .

2.41.81.30.90.50.20.0

Fly AshChemical Index Cfa

Figure 14 – Minimum fly ash replacement to prevent ASR expansion.

31

0

10

20

30

40

50

60

70

80

0.0 0.2 0.4 0.6 0.8 1.0

E14c (cement only, Cc = 4) (%)

Min

imum

Fly

Ash

Rep

lace

men

t (%

) .

2.41.81.30.90.50.20.0

Fly AshChemical Index Cfa

Figure 15 – Minimum fly ash replacement to prevent ASR expansion with 90% confidence.

32

MINIMUM FLY ASH CEMENT REPLACEMENT TO MITIGATE

ALKALI SILICA REACTION

World of Coal Ash11-15 April 2005Lexington, KY

L. Javier Malvar, Ph.D., P.E.U.S. Navy, NFESC

Lary R. Lenke, M.S., P.E.University of New Mexico

2

Problem:Airfield Damage

from ASRNAS Point Mugu

PA-7 replacement cost: $13M

3

ASR Damage Channel Islands ANG

12 years old in pictures $14M to rebuilt (built in 1989)

Photos courtesy of ANG

4

ASR Damage Channel Islands ANG

Localized damage to drainage structures

Extruded joint seal

5

ASR Damage Channel Islands ANG

6

ASR in Department of Defense Airfields

Airfields already identified as having ASR problems:• 23 Air Force airfields

– Air Combat Command: Seymour-Johnson AFB, NC, Langley AFB, VA, Offut AFB, NC, Holloman AFB, Cannon AFB, NM, Beale AFB, CA, Tonopah Test Range, NV

– Pacific Air Force : Osan AB, Korea – Air Force Material Command: Plant 42, CA, Kirtland AFB, NM, Wright-

Patterson AFB, OH, Edwards AFB, CA, Tinker AFB, OK– Air Mobility Command: Andrews AFB, MD, Travis AFB, CA, Dover, DE– Air Force Space Command: Warren AFB, WY– U.S. Air Force Europe: Torrejon AB, Spain, Aviano AB, Italy– Air National Guard: Pease AFB, NH, Channel Islands ANG Site, CA– Air Education and Training: Little Rock AFB, AK, Vance AFB, OK

• 3 Army airfields– Biggs, TX, Ft Bliss, TX, Ft Campbell, KY

• 8 Navy airfields– NAS Point Mugu, CA, NAS Fallon, NV, NOLF San Nicolas Island, CA,

MCAS Iwakuni, Japan, MCAS Beaufort, SC, MCAS Cherry Point, NC, NAS Whidbey Island, WA, MCAF Quantico, VA

7

Other Problems:Matilija Dam, Ojai

Photos courtesy of Francis Omoregie, USA COE

8

Other Problems

Photos courtesy of Gene Gutierrez, USA COE

9

Previous Work: Tri-Service State-of-the-Art Report

• Use of low alkali cement (less than 0.6% available alkalis) required but not sufficient

• Many beneficial admixtures or supplementary cementitious materials (SCMs) are known to mitigate ASR – Fly Ash Classes F, C– Class N natural pozzolan, Calcined Clays– GGBFS– Lithium – Silica Fume– Entrained Air

• Beneficial admixtures must be used within certain ranges otherwise they may result in worse ASR

http://www.nfesc.navy.mil/shore/files/ACIasr.pdfThis report was summarized in a paper:

(ACI Materials Journal, Vol. 99, No. 5, Sept-Oct 2002, pp. 480-489 – see also ACI Materials Journal, Vol. 100, No. 4, July-Aug 2003, pp. 346-350)

10

Previous Work: Tri-Service State-of-the-Art ReportRestrictions on Class F Fly Ash (and Class N Natural Pozzolans)

• Recommendations:– Insure enough SiO2: require Class F fly ash– Limit CaO: Class F fly ash (or Class N pozzolan) with

CaO < 8% should be used at minimum replacements of 25% (for CaO < 10% use minimum replacement of 30%)

– Limit Na2Oe: maximum available alkalies < than 1.5% (ASTM C 618)

– Limit LOI: loss on ignition < 6% (3% better)– Limit MgO: require Class F fly ash

• Although Class N pozzolan has been less used than Class F fly ash, a CALTRANS study shows that it can perform equally well in reducing expansion

• Class C is currently not recommended for ASR mitigation due to its high CaO content

11

Previous Work: Tri-Service State-of-the-Art ReportOther Benefits of Class F Fly Ashes

Reduced construction costs. Savings in Portland cement production (~ $2B/year) Reduced heat of hydration and reduced permeability.Enhanced durability of waterfront structures. Higher long term strengths.Reduction in CO2 generation (40% of Kyoto Protocol) Higher fly ash recycling.Conformity with Resource Conservation and Recovery Act (RCRA) affirmative procurement regulations and DoD affirmative procurement policy. Increased resistance to high temperatures from jet blast.

Natural pozzolans and slag also offer similar benefits

12

Summary of Previous Work

• Completed initial ASR detection at some bases• Completed state-of-the-art report for ASR mitigation• To mitigate ASR concrete should have 25-40% Class F fly

ash (or Class N natural pozzolan), or 40-50% GGBFS– Also LOI < 6%, available alkalies <1.5%, CaO < 8%– Allow 8% < CaO < 10% for Class F fly ash > 30%

• UFGS are being updated to include recommendations– Required for Navy pavements– Required for Air Force/Army pavements if aggregates

show some reactivity, recommended otherwise• Guidelines already applied at several locations

13

Applications: Simulated Carrier Deck, NAS Point Mugu

In the main runway, a continuously reinforced concrete section 756 feet long, 80 feet wide, and 14 inches thick was completed.

The mix included 30% Class F fly ash (with 8.6% CaO). Ratio of water to total cementitious materials was 0.4.

14

Motivation for Enhancing Existing Guidelines:Unanswered Questions

• Could we use Class C fly ash to prevent ASR?• Could we use an ash that is neither Class F nor C?• If we have 2 Class F fly ashes, which one is better to

prevent ASR?• For a given cement, a given aggregate reactivity, and a

given fly ash, what amount of cement replacement would be necessary to prevent ASR?

15

New Developments: ASR Mitigation using Fly Ash

There are 3 characteristics of a fly ash that determine its efficiency in preventing alkali-silica reaction:

• Fineness– Finer pozzolans are more efficient in mitigating ASR, e.g., Malhotra

et al. (1994) state: “fineness of fly ashes is one of the most important physical properties affecting pozzolanic activity.” Others found a direct correlation between fineness and ASR mitigation.

– But since all fly ashes meet the same fineness requirement, fineness would be similar for most and could not be used to differentiate them

• Mineralogy– While ashes can be characterized by their basic chemical

components, those components can be bound differently and react differently from ash to ash, e.g., Mehta (1986) showed the importance of mineralogy in mitigating sulfate attack.

• Chemistry – This approach has already been used with success (e.g. Shehata and

Thomas), and is one starting point of the current work– If there is a relationship between chemistry and mineralogy,

classifying ashes by chemical composition might address both

16

New Developments: Fly Ash Constituents and their Effect on ASTM C 1260 Expansion

Deleterious Constituents (promote expansion)

CaO (calcium oxide)Na2O and K2O (alkalis)

MgO (magnesium oxide)SO3 (sulfur trioxide)

Beneficial Constituents (reduce expansion)

SiO2 (silicon dioxide)Al2O3 (aluminum trioxide)

Fe2O3 (iron oxide)

17

ASTM C 1260 and ASTM C 1567

• ASTM C 1260 (AMBT)– Potential alkali reactivity of aggregates– Cement alkali not a significant factor affecting expansion

in this test– Used in modified form (with actual mix) to assess effect

of supplementary cementitious materials such as fly ash

• ASTM C 1567– Potential alkali-silica reactivity of combinations of

cementitious materials and aggregate– Similar to ASTM C 1260 modified

18

Data Analyzed

Effect of various constituents was correlated to ASTM C 1260 14-day expansion in previous data reported in the literature:

• McKeen, Lenke, and Pallachulla (1998, 2000) – 5 fly ashes, 4 reactive aggregates, Type I/II cement (0.55% Na2Oeq)

• Shehata and Thomas (2000) – 18 ashes and 1 cement (1.02% Na2Oeq) were used in the AMBT

• Touma et al. (2000, 2001) – Type F ash (12.3% CaO), Type C ash (26.1% CaO), 6 reactive aggregates, and one Type I/II high alkali cement (1.14% Na2Oeq).

• Shon, Zollinger, and Sarkar (2004) – Type C fly ash (25.9% CaO) with a medium alkali cement (0.65% Na2Oeq) and a reactive siliceous sand

• Detwiler (2003) – low, medium, and high CaO fly ashes (5.7%, 18.6%, 25.7%, respectively) , Type I cement, 1 reactive aggregate

In addition this data set was used to check the model:• Rangaraju and Sompura (2005) – Used 2 ashes (F and C), 2 cements

(0.64% and 0.24% Na2Oeq) and 89 fine aggregates. Cement replacement was always 20%.

19

Deleterious Constituents: Cementitious CaO

• Normalized expansion = cementitious blend expansion / cement only expansion (using ASTM C 1260 at 14 days of exposure)

• Cementitious CaO = CaO of cementitious blend• Strong correlation

y = 0.0447x - 1.9070R2 = 0.7143

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 10 20 30 40 50 60 70Cementitious CaO (%)

20

Deleterious Constituents: Cementitious Alkalis

• Coefficient of determination R2 ≈ 0• ASTM C 1260 (sect. 3.2): in this test alkali is not a

significant factor affecting expansion

y = -0.1018x + 0.5604R2 = 0.0251

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5Cementitious Na2Oeq (%)

21

Deleterious Constituents: Cementitious MgO

y = 0.1008x + 0.1948R2 = 0.0552

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0Cementitious MgO (%)

• Very low correlation

22

Deleterious Constituents: Cementitious SO3

y = 0.6472x - 1.2287R2 = 0.5000

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.0 1.0 2.0 3.0 4.0Cementitious SO3 (%)

• Significant correlation

23

Beneficial Constituents: Cementitious SiO2

y = -0.0679x + 2.2718R2 = 0.7409

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 10 20 30 40Cementitious SiO2 (%)

• Strong inverse correlation

24

Beneficial Constituents: Cementitious Al2O3

• Strong inverse correlation

y = -0.1115x + 1.3806R2 = 0.6038

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 5 10 15 20Cementitious Al2O3 (%)

Nor

mal

ized

Exp

ansi

on

25

Beneficial Constituents: Cementitious Fe2O3

y = -0.1986x + 1.1472R2 = 0.1313

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.0 2.0 4.0 6.0 8.0Cementitious Fe2O3 (%)

• Weak inverse correlation

26

Combination of all Deleterious Constituents

• Combine all constituents promoting expansion (molar equivalents)CaOeq = CaO + 0.905 Na2Oeq + 1.391 MgO + 0.700 SO3 or CaOeq = CaO + 0.905 Na2O + 0.595 K2O + 1.391 MgO + 0.700 SO3

• Better correlation than any single deleterious constituent

y = 0.0457x - 2.2502R2 = 0.7799

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 20 40 60 80Cementitious CaOeq (%)

27

Combination of all Beneficial Constituents

y = -0.0546x + 2.2548R2 = 0.7834

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 10 20 30 40 50Cementitious SiO2eq (%)

• Combine all constituents promoting expansion (molar equivalents)SiO2eq = SiO2 + 0.589 Al2O3 + 0.376 Fe2O3

• Better correlation than any single deleterious constituent

28

Combination of Deleterious and Beneficial Constituents

• Correlate normalized expansion to ratio deleterious/beneficial• Divide CaOeq/SiO2eq of mix by CaOeq/SiO2eq of cement only• Best correlation yet

y = 1.7309x - 0.6879R2 = 0.8287

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.00 0.20 0.40 0.60 0.80 1.00Normalized Cementitious CaOeq/SiO2eq

29

Combination of Deleterious and Beneficial Constituents: Tri-Linear Fit

y = 2.1216x - 0.9389

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.00 0.20 0.40 0.60 0.80 1.00Normalized Cementitious CaOeq/SiO2eq

Cementitious (Linear Portion)

Cementitious (Zero-Slope Portion)

R2 = 0.8671 (thru all data)

• Best fit is non-linear: try tri-linear fit for simplicity• Best R2 so far

30

Combination of Deleterious and Beneficial Constituents: Tri-Linear Fit using Weights

Uses 2 weights for additional constituents: α = 5.64, β = 1.14 (best fit) (probably sufficient, e.g. alkali cannot be better evaluated with this test)

y = 2.2788x - 1.1343

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.00 0.20 0.40 0.60 0.80 1.00Cb/Cc

Cementitious (Linear Portion)Cementitious (Zero-Slope Portion)

R2 = 0.9026 (thru all data)

( ))376.0589.0(

700.0391.1595.0905.0

32322

322

2 OFeOAlSiOSOMgOOKONaCaO

SiOCaO

Cbeq

beqb ++

++++==

βα

β

α

31

90% Confidence Level andComparison to Rangaraju and Sompura’s data

All Data14-Day A.M.B.T. vs. Cementitious Composition

(CaO)eq : Calculated Equivalent (SO3 , MgO, (Na2O)eq)(SiO2)eq : Calculated Equivalent (Al2O3, Fe2O3)

α = 5.64, β = 1.14

y = 2.2788x - 1.1343R2 = 0.7767

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00Cb/Cc

14-D

ay N

orm

aliz

ed E

xpan

sion

, % Cementitious (Linear Portion)Cementitious (Non-Linear Portion)Rangaraju DataLinear (Cementitious (Linear Portion))

R2 = 0.9026(Malvar & Lenke data)

90% Conf. Bandy = 2.2788x - 1.0027

F-as

h /

HA

PC-C

1

F-as

h /

LA

PC-C

2

C-a

sh /

HA

PC-C

1

C-a

sh /

LA

PC-C

2

F-ash /HAPC-C1Control

F-ash /LAPC-C2Control

C-ash /HAPC-C1Control

C-ash /LAPC-C2Control

• Data includes 2 cements and 2 fly ashes at 20% replacement

32

Cfa: Fly Ash Chemical Index

• Cfa ≈ 1.30 matches limit between F, C (ASTM C 618), or CI and CH (Canada CSA A3001)

• Cfa ≈ 0.50 matches limit between F, CI (Canada)

• DM sum = 68.53 ≈ 70%BDII has 8.45% alkali

• MN ash shown as CI: very low SO3 and alkalis, actually CaO 8.68% → could be F

• BR and TB ashes shown as CI but almost CH: high alkali, MgO, SO3, not efficient

Chemical Index may improve previous

classifications

Fly Ash Name Study Chemical Index, of Fly Ash, Cfa

Ash Type (ASTM)

Ash Type (CSA)

Escalante F (EF) NM 0.25 F F FourCorners F (4F) NM 0.26 F F Coronado F (CF) NM 0.31 F F

MN S&T 0.33 F CI FM S&T 0.37 F F

Low CaO (DL) Detwiler 0.46 F F LG S&T 0.48 F F

Touma F (IF) Touma 0.53 F CI SD II S&T 0.58 F CI SD I S&T 0.59 F CI

Esc. F/Tolk C (ET) NM 0.76 F CI C1 S&T 1.11 F CI

Med CaO (DM) Detwiler 1.22 C CI BD II S&T 1.29 F CI WM S&T 1.35 C CI C2 S&T 1.38 C CH PI S&T 1.42 C CH

EW S&T 1.44 C CH Shon C (SC) Shon 1.45 C CH

Touma C (IC) Touma 1.47 C CH Tolk C (TC) NM 1.50 C CH

IN S&T 1.65 C CH CC S&T 1.65 C CH TB S&T 1.68 C CI PP S&T 1.71 C CH

High CaO (DH) Detwiler 1.84 C CH OK I S&T 1.91 C CH OK II S&T 2.23 C CH

BR S&T 2.42 C CI

33

Classification of Ashes Not MeetingASTM or Canadian Standards

Ultra fine fly ash (UFFA)• UFFA has CaO = 11.8% which makes it CI in

Canada, and not usable in some specifications• However, its Cfa = 0.53 which makes it

equivalent to a good F ash (ASTM), or a good borderline F/CI (Canada)

• UFFA has the additional advantage of being very fine → it is a very good ash

Fly Ash SiO2 Al2O3 Fe2O3 CaO SO3 MgO Na2Oeq Cfa Barbers Point 43.47 18.42 6.30 15.72 6.56 1.45 1.40 1.03

UFFA 50.66 27.24 3.06 11.80 1.03 2.51 0.35 0.53

Chemical Index allows

classification of ashes not meeting ASTM or Canadian

StandardsBarbers Point ash• Not F nor C by ASTM (sum = 68.19%, SO3 > 5%)• Cfa = 1.03 equivalent to an acceptable F ash (ASTM)

34

Derivation of Minimum Fly Ash Cement Replacement To Insure ASR Mitigation ( 0.08% @ 14 days)

from which the required W can be derived as:

498.008.0439.008.0

1414

+⎟⎟⎠

⎞⎜⎜⎝

⎛=⎟⎟

⎠

⎞⎜⎜⎝

⎛=

ccc

b

EEg

CC

( ))376.0589.0(

700.0391.1595.0905.0

32322

322

2 OFeOAlSiOSOMgOOKONaCaO

SiOCaO

beq

beq

++++++

=β

α

β

α

( ) ( )( ) ( )ceqfaeq

ceqfaeq

beq

beqb SiOWSiOW

CaOWCaOWSiOCaO

Cββ

αα

β

α

222 )1()1(

−+

−+==

ceq

ceqc SiO

CaOC

β

α

2

=

( )

( )cceq

faeq

ceq

faeq

c

EgSiOSiO

CaOCaO

EgW

142

2

14

/08.011

/08.01

⎟⎟⎠

⎞⎜⎜⎝

⎛−−⎟

⎟⎠

⎞⎜⎜⎝

⎛−

−=

β

β

α

α

where W is the percent fly ash substitution by weight (expressed as a decimal) and

y = 2.2788x - 1.1343

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.00 0.20 0.40 0.60 0.80 1.00Cb/Cc

Cementitious (Linear Portion)Cementitious (Zero-Slope Portion)

R2 = 0.9026 (thru all data)

From the graph:

where

Function of data used (g) and:• Chemistry of cement• Chemistry of ash• Aggregate reactivity (E14c)

35

Minimum Fly Ash Cement Replacement To Insure ASR Mitigation ( 0.08% @ 14 days)

• Graph valid for 1 cement type (Cc=4)

• Minimum to insure ASTM C 1260 exp.

0.08% @ 14 days• Can be redrawn if

lower limits are desired (e.g. 0.06%)

• Curves valid within C 1260 limitations (e.g. effect of alkalis)

• Curves based on limited data

• Based on best estimates

• 25% minimum is a good rule of thumb for many aggregates

0

10

20

30

40

50

60

70

80

0.0 0.2 0.4 0.6 0.8 1.0E14c (cement only, Cc = 4) (%)

Min

imum

Fly

Ash

Rep

lace

men

t (%

)

2.41.81.30.90.50.20.0

Fly AshChemical Index Cfa

36

Minimum Fly Ash Cement Replacement To Insure ASR Mitigation ( 0.08% @ 14 days) with 90% Confidence

• Same limitations as before

• 90% confidence• 25% minimum is

a good rule of thumb for many aggregates

0

10

20

30

40

50

60

70

80

0.0 0.2 0.4 0.6 0.8 1.0

E14c (cement only, Cc = 4) (%)

Min

imum

Fly

Ash

Rep

lace

men

t (%

)

2.41.81.30.90.50.20.0

Fly AshChemical Index Cfa

y = 2.2788x - 1.1343

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.00 0.20 0.40 0.60 0.80 1.00Cb/Cc

Cementitious (Linear Portion)Cementitious (Zero-Slope Portion)

R2 = 0.9026 (thru all data)

37

Conclusions

• Data from previous research studies were used to assess the effectiveness of fly ashes in preventing ASR, based on their chemical composition, the composition of the cement, and the reactivity of the aggregates.

• A chemical index, Cfa, was derived based on the fly ash (or cement) constituents, which was optimized to maximize the correlation with the test data.

• Cfa correlated well with ASTM C 618 and CSA A3001 fly ash classifications. This index was also used to assess the efficiency of other ashes not meeting either specification.

• For a given aggregate reactivity, a given cement, and a given ash, it was possible to derive the minimum cement replacement that is needed to insure a 90% confidence that the 14-day AMBT expansion would remain below 0.08%.

• 25% Class F ash minimum replacement is a good rule of thumb for many aggregates