Methods for Evaluating Fly Ash for Use in Highway Concrete (2013)

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8Overview The research to evaluate new and existing test procedures involved five separate tasks that were performed as separate studies. These tasks are briefly described in this section; details are provided in the following sections of this chapter. Review of existing specification and testing environment. The literature pertaining to CFA specifications and testing protocols was reviewed to determine the current practices and where improvements may be needed. A survey of SHAs was also conducted to determine the types, characteristics, and ranges of fly ash content currently used in the United States and those likely to be used in the future. Characterization of coal fly ash. The results of the literature review and SHA survey were used to identify 30 CFA sources for use in this study. The sources were selected to broadly repre- sent the range of CFA currently used in highway construction. The CFA sources selected include Class C and Class F ashes per AASHTO M 295-07 and various beneficiated ashes. (AASHTO M 295-07 was used as the reference for this research; AASHTO M 295-11 was published after this work was completed.) A characterization protocol was then applied to establish baseline properties of each source. This protocol included all tests currently and commonly used to characterize CFA to provide a means for determining the strengths and weak- nesses of these test methods when applied to a wide range of CFA types. It also helped identify other characteristics for use in developing new tests. Characterization of strength activity. Chemical charac- terization is based on the bulk chemical composition, which indirectly infers if a fly ash is pozzolanic or has potential for hydraulic reactions in a concrete mixture. The current pozzo- lanic and strength activity tests were reported as not adequately predicting field performance and in some cases incorrectly identifying inert materials as being reactive (Schlorholtz, 2006). This research evaluated the existing test for pozzola- nic activity (i.e., strength activity index), considered potential modifications, and also evaluated a modification of the Keil hydraulic index test (Keil, 1952). Characterization of the effects of carbon on air entrain- ment. The residual carbon contained within fly ash can adversely affect air entrainment in concrete as carbon can adsorb the AEA, thereby reducing the effectiveness of the admixture for producing an adequate air-void system (Mehta and Monteiro, 2006). The current LOI test estimates the total residual car- bon, but does not determine the adsorption properties of the carbon. In this project, four different tests for measuring the effect of carbon on air entrainment were investigated for inclusion in a new specification. These tests are the foam index test and foam drainage test and modified versions of ASTM test methods: ASTM D4607-94(2006), Standard Test Method for Determination of Iodine Number of Activated Carbon, and ASTM D3860-98(2008), Standard Practice for Determination of Adsorptive Capacity of Activated Carbon by Aqueous Phase Isotherm Technique, which are used for characterizing pow- dered activated carbon (PAC) for water treatment. Assessing ASR mitigation. AASHTO M 295 does not ref- erence some tests that are currently available to evaluate the effectiveness of a specific CFA for mitigating ASR. Also, there was a need to identify quicker, more effective tests for assess- ing ASR mitigation. Therefore, existing test methods and a proposed rapid method for determining the effectiveness of a CFA for mitigating ASR in a concrete mixture were evalu- ated. The existing methods were ASTM C1567, Standard Test Method for Determining the Potential Alkali-Silica Reactivity of Combinations of Cementitious Materials and Aggregate (Accel- erated Mortar Bar Method), and ASTM C1293, Standard Test Method for Determination of Length Change of Concrete Due to Alkali-Silica Reaction. The proposed test method was the alkali leaching test (Shehata and Thomas, 2006). Results from the latter test were correlated to those of ASTM C1293 and ASTM C1567. Also, a number of standard tests were performed on different fly ash sources and the methods used are summarized in this C H A P T E R 3 Methodology

9 section. Additionally, a number of new tests were developed or evaluated; the process used to refine these tests and their method of application is also summarized. Additional information on the results and procedures is provided in Attachment C. Materials CFA Sources A first step in this research was identification of 30 sources of CFA representative of the broad range of CFA available for use in highway construction in the United States. These sources were identified through a survey of SHAs and contacts within the industry. Material certifications were acquired for CFA sources from over 100 coal combustors located in the United States and compared with a database of CFA properties assembled by the research team. The selected 30 CFA sources consisted of 17 sources of Class F fly ash and 13 sources of Class C fly ash. Details on these sources, producers’ certifi- cation data, and a property database are provided in Attach- ment C. The following is a summary of the range of properties of these sources, as obtained from producers’ plant certificates: • Sum of SiO2, Al2O3, and Fe2O3: 51.8% to 92.7% • CaO: 0.9% to 30.6% • Na2Oe: 0.3% to 7.9% • LOI: 0.1% to 5.6% • Fineness: 10% to 24.0% • Strength index (7-day test value): 75% to 112% • Strength index (28-day test value): 80% to 120% • Water requirement: 93% to 100% • Density: 2.1 to 2.8 g/cm3 The properties used as the basis for comparison and selection of the CFA sources included in this study are those com- monly collected by producers to meet the requirements of AASHTO M 295-07 specifications. However, other factors were considered such as the geographic distribution, types of coal, combustor, and pollution control measures used at the power plant. Although producers’ certifications were obtained for each identified source, a characterization study was undertaken to confirm the reported CFA properties and to identify CFA sources suitable for use in other portions of this research, and also to evaluate existing specifications and tests. Some of the 30 CFAs were suited for assessing the effects of CFA on air entrainment, evaluating protocols for ASR mitigation, or developing new approaches to measuring CFA strength activity. Based on the characterization study, suitable sources were identified and used where appropriate. The research team obtained additional CFA sources for use in developing the foam index, iodine number, and direct adsorption isotherm tests. Also, for developing these tests, it was necessary to blend ashes to achieve target values of LOI. The CFA sources blended were FA-ZF (LOI = 6.06% wt) and FA-ZE (LOI = 23.3% wt). The blending ratios used were 1:3, 1:1, and 3:1, respectively. A listing of all CFA sources used in the experiments conducted is presented in Table 3.1. Portland Cement Sources Three different sources of portland cement designated PC-1, PC-2, and PC-3 were used in the research; the nomi- nal properties provided on mill certifications are summa- rized in Attachment C. The chemical compositions of these cements were determined using x-ray fluorescence spectros- copy (XRF) and x-ray diffraction (XRD), and other tests were conducted to determine relevant physical properties. Also, for comparison, selected tests were performed using a fourth portland cement source (PC-4); results of these tests are dis- cussed in Attachment C. Air-Entraining Admixtures To evaluate new tests for assessing the effects of CFA on air entrainment, it was necessary to select a suite of AEAs that represent the range of AEAs used in highway concrete. The specifications provided by 24 SHAs identified 47 common AEA types. These AEAs were placed in the following five cate- gories identified in NCHRP Report 578 (Nagi et al., 2007): • Vinsol resin • Alpha olefin sulfonate • Resin/rosin and fatty acid • Benzene sulfonate • Combination Since this classification is based on chemical composition, it was expected that AEAs in the same category would exhibit similar adsorption characteristics. The most commonly used, pre-approved AEA in each category was chosen as the pri- mary AEA in experiments dealing with new tests for evaluat- ing the effects of CFA on air entrainment. The primary AEAs are listed in Table 3.2 as AEA-1 through AEA-5. In later steps, two AEAs were added (i.e., AEA-6 and AEA-9). AEA-6 was included because of its observed low adsorption capacity, and AEA-9 was included in selected tests to verify the results obtained with AEA-5. Other AEAs were included in limited tests for developing the direct adsorption isotherm test. CFA and Cement Sample Processing The multiple buckets for each CFA source were combined and homogenized in a rotating drum mixer and a 7 to 9 lb

10 grab sample was obtained for the characterization study. The remainder was placed in a watertight plastic drum, labeled, and placed in storage. The grab sample was further homog- enized by quickly mixing it in a plastic bag and then a 200 g sub-sample was extracted using a sampling tube. The port- land cement used in the study was all obtained from the same production lot. The complete process used for obtaining sam- ples of ash for the various tests is discussed in Attachment C. Other Materials Other materials used in this research were Pyrex® glass for ASR testing, calcium hydroxide for the available alkali tests, standard graded and 20-30 graded sand both meeting the requirements of ASTM C778-06, Standard Specification for Standard Sand, and various inert fillers used for the strength activity study. These materials were tested prior to use to deter- mine their basic chemical or physical properties and compli- ance with relevant specifications. All of these materials are covered by standards except the inert fillers. The reported properties of these inert filler materials are summarized in Attachment C. Characterization of Coal Fly Ash The following tests were performed on samples of the 30 identified CFA sources. The tests were conducted in accor- dance with ASTM C311-11a, Standard Test Methods for Sampling and Testing Fly Ash or Natural Pozzolans for Use in Portland Cement Concrete when applicable. However, some properties were measured using non-standard test methods (e.g., XRD and thermo-gravimetric analysis). The standard tests were generally conducted twice (i.e., tested on different CFA Source Test ID Class LOI (% wt) CaO (% wt) St re ng th & A SR M iti ga tio n Fo am D ra in ag e Fo am In de x Io di ne N um be r D ir ec t A ds or pt io n M ea su re m en t M or ta r V er ifi ca tio n of D ir ec t A ds or pt io n C on cr et e V er ifi ca tio n o f D ir ec t A ds or pt io n FA-A F 0.94 0.82 X X X X X FA-G F 2.32 1.45 X X X X FA-H F 0.25 3.46 X X X X X FA-J F 1.59 1.28 X X X X FA-M F 0.27 7.17 X FA-O F 1.43 10.2 X X X X X X FA-Q F 0.38 16.6 X FA-T F 0.45 13.6 X X X X FA-U C 0.54 21.9 X FA-X C 0.42 19.3 X FA-ZA C 0.27 27.3 X FA-ZC C 0.16 30.2 X FA-ZE F 23.30 – X X X X FA-ZF F 6.06 – X X X X FA-ZG C 1.22 – X X FA-ZJ F 21.34 – X X FA-ZM F 10.69 – X X X X FA-ZN F 3.41 – X X X X X 25-75 Blend* – 10.37 – X X X 50-50 Blend* – 14.68 – X X 75-25 Blend* – 18.99 – X X *FA-ZF/FA-ZE blends Table 3.1. CFA sources and tests. Table 3.2. AEAs used in assessing the effects of CFA on air entrainment. AEA ID Type of Admixture No. of SHAs with Pre-approval* AEA-1 Vinsol resin 20 AEA-2 Alpha olefin sulfonate 20 AEA-3 Combination 17 AEA-4 Resin/rosin and fatty acid 23 AEA-5 Benzene sulfonate 10 AEA-6 Resin/rosin and fatty acid 14 AEA-7 Resin/rosin and fatty acid 0 AEA-8 Alpha olefin sulfonate 7 AEA-9 Benzene sulfonate 9 AEA-10 Alpha olefin sulfonate 16 AEA-11 Vinsol resin 19 AEA-12 Resin/rosin and fatty acid 22 * Out of 24 SHAs

11 days) to provide an indication of precision. Cement PC-2 was used for the strength and pozzolanic activity indices, auto- clave expansion, and air content tests. Specific aspects of the test methods are noted in the following list: • Moisture content samples were dried overnight at a tem- perature of 105°C to 110°C. • LOI samples were ignited to a constant mass at 750°C ± 50°C. • Oxide samples were analyzed using XRF. The samples were fused using a lithium borate flux to produce a glass disk. Thirteen elements were quantified (Si, Al, Fe, Ca, Mg, Na, K, S, Ti, P, Mn, Sr, and Ba). When expressed as oxides, these elements typically account for over 99% of the bulk com- position (expressed on an LOI-free basis) of CFA. Specific samples were also pressed into pellets to better evaluate the sulfur content of the ashes. • Available alkali (i.e., soluble Na and K, expressed as oxides and sodium oxide equivalent) was determined in accor- dance with ASTM C311. • Density was determined using a helium pycnometer. • Fineness was determined by wet-washing on a 45 µm sieve (#325 mesh). • Soundness of CFA-cement pastes was determined by the autoclave expansion test. Mixtures containing 20% (by mass of cement) of each CFA were molded at normal consistency. • Air entrainment determined the amount of AEA-1 required to produce a mortar air content of 18%, in accordance with ASTM C311. • The strength activity index (SAI) with portland cement was determined using mortar mixtures containing 20% CFA (by mass of cement). The mortars were mixed in nine cube batches; the index values were calculated after 7, 28, and 90 days of standard curing (i.e., limewater cure at 23°C). Control mixtures containing only cement were also mixed on each day. The water requirement for each mortar mix- ture was determined by maintaining the flow of the mix- ture within ±5% of the flow of the control mixture. The precision of the test method was evaluated by making seven replicate mixtures containing CFA. In addition, two inert materials (INF-1 and INF-2) were included to check the specification limit for the test method. • Pozzolanic activity index (PAI) tests were conducted per ASTM C311 on mortar mixtures containing 35% CFA (by volume of cement). The mortars were mixed in six cube batches; the index values were calculated after 7 and 28 days of accelerated curing (i.e., water vapor at 38°C). A control mixture containing only cement was also mixed on each day. The results reflect the average of three tests at 7 and 28 days. The water requirement for each mortar mixture was evaluated by maintaining the flow of the test mixture between 100% and 115%. The precision of the test method was evaluated by making six replicate mixtures contain- ing CFA. In addition, two inert materials (INF-1 and INF-2) were used to check the specification limit for the test method. • Effectiveness in controlling ASR was determined for each CFA when tested with cement PC-3 in accordance with ASTM C441/C441M-11, Standard Test Method for the Effectiveness of Pozzolans or Ground Blast Furnace Slag in Preventing Excessive Expansion of Concrete Due to the Alkali- Silica Reaction, with the modifications described in ASTM C311. Test mixtures contained a 25% replacement (by mass of cement) of CFA for an equivalent amount of portland cement. Control mixtures containing only cement were also mixed on most days to accompany the mixtures containing CFA. At least three repetitions (individual batches mixed on different days) with each control cement (i.e., PC-1, PC-2, and PC-3) were made. In addition, a set of control specimens was made using a very-low-alkali cement that exhibited a nearly negligible expansion (i.e., <0.01% at 56 days) during the Pyrex mortar bar tests. Test results provided the average of tests on three specimens after 14, 28, and 56 days of accelerated curing (i.e., water vapor at 38°C). Selected specimens were monitored until 90 days. INF-2 was also included in the study to evaluate the effect of cement replacement. The precision of the test method was evaluated by testing six replicate mixtures. • XRD was conducted on samples ground to a fine powder in a micronizing mill. Test specimens were backpacked into a sample holder and then scanned from about 5 to 70 degrees two-theta using a copper x-ray tube and diffracted beam monochromator. Step-size and counting time were selected to produce reasonably smooth diffractograms. Glass con- tent was estimated using the diffuse scattering halo present in the diffractograms. In addition, quantitative x-ray diffraction (QXRD) and differential thermal analysis/thermal gravimetric analysis (DTA/TGA) tests were conducted on eight CFA samples (H, M, O, Q, U, X, ZA, and ZB) to more accurately describe the properties known to influence reactivity. The QXRD was performed to characterize the crystalline and glass constitu- ents of CFA. Both the relative intensity ratio method (RIR) and the Rietveld method were used to obtain estimates of phase and glass concentrations. The quantitative measure- ments were repeated multiple times to produce an estimate of the precision of the determinations. The DTA/TGA was performed to provide information on the moisture content and LOI of the bulk CFA, the combustion temperature of the residual coal particles present in the CFA, and the softening temperature of the CFA. In addition, the residue from the thermal analysis test was analyzed using XRD to determine the mineralogy of the devitrified glass.

12 Characterization of Strength Activity Two different approaches were investigated to examine tests for measuring the effect of CFA on the strength of a cementitious mixture. One approach considered modifica- tions to the current SAI and another examined an approach based on the Keil hydraulic index (KHI). The CFA sources listed in Table 3.1 were included in this investigation. Mortar cubes for both the modified SAI and KHI tests were cast following ASTM C109/C109M-11a, Standard Test Method for Compressive Strength of Hydraulic Cement Mortars (Using 2-in. or [50-mm] Cube Specimens), except that the water to cementitious materials ratio was kept constant at 0.485 and the sand to cement ratio was 2.75 using graded sand meeting ASTM C778. Cubes were de-molded at 1 day of age and placed in saturated limewater tanks at 23°C as per ASTM C109. Three 2 in. mortar cubes were tested at each age and the strengths were averaged. A compressive testing machine of 100,000 lb capacity specifically fitted for testing mortar cubes was used for all tests. For the modified SAI tests, all eight CFA sources were tested with each of the three portland cements at 0% wt and 20% wt replacement with CFA. Four Class C ashes were also tested at a replacement level of 35% wt. The specimens with 0% and 20% replacement followed the current SAI test procedure, while the 35% replacement was similar to the PAI test. To evaluate the contribution of an inert filler to strength develop- ment, INF-1 was tested at 20% and 35% cement replacement. Another approach was to modify the KHI previously used for evaluating the reactivity of blast furnace slags (Keil, 1952; Lea, 1970; Hooton and Emery, 1983; Pal et al., 2003). The KHI is expressed by Equation 3.1. ( )= − − × 100 3.1Keil Hydraulic Index a c b c Where: a = the strength of 70% slag/30% portland cement at time t; b = the strength of 100 percent portland cement at time t; c = the strength of 70% ground quartz/30% portland cement at time t In this test, ground quartz filler with approximately the same fineness as the CFA was included. The difference between this method and other strength activity tests is the KHI test allows for separation of the pozzolanic and hydraulic effects from the physical filler effects. The KHI can range from 0% for an inert material to over 100% if the supplementary cementitious materials (SCM) develop more strength than the portland cement mixture. To evaluate this method, cement replacements of 20% and 35% (by mass of cement) were used in lieu of the specified 70% replacement for slag. Mortar cubes were tested at ages of 7, 28, and 56 days. The ground quartz specified in the original Keil method was replaced with inert fillers INF-1, INF-2, and INF-3 in an attempt to find an appropriate commercially available filler material for use in the test method. Using the same type of mortar cube specimens as for the SAI tests, all eight CFAs and INF-1 were tested in a full facto- rial design with each of the three portland cements (PC-1, PC-2, and PC-3) at 0% and 20% wt replacement of cement with CFA and inert filler. Additionally, four Class C fly ash sources were evaluated at a 35% wt replacement of cement with CFA and inert filler INF-1. Strength tests were con- ducted at 7, 28, and 56 days of age. Additional SAI and KHI tests were later conducted using a fourth portland cement source (PC-4) together with all eight CFA sources at 35% wt replacement. For the KHI tests, three inert fillers (INF-1, INF-2, and INF-3) were also tested at 35% wt replacement. These were the only tests conducted with PC-4 and were undertaken to verify results obtained with PC-3. The results of these tests are provided in Attachment C. Characterization of the Effects of Carbon on Air Entrainment Foam Drainage Test The objective of the foam drainage test is to assess inter- actions between cement, or combinations of cementitious materials, and AEA solutions. The procedure was evaluated to determine if differences in the potential for a CFA to affect air entrainment could be detected. These different procedures are reported in the literature: Gutmann (1988), Cross et al. (2000), and Taylor et al. (2006); differences between these procedures are discussed in Attachment C. The test methods by Cross et al. and Taylor et al. were selected for evaluation. These test procedures were modified by using only CFA as the cementi- tious material and were evaluated to determine if CFA and AEA interactions could be detected (further discussion of the methodology is provided in Attachment C). The test results indicated that, in most cases, the test does not adequately dis- tinguish the effects of CFAs with significantly different levels of LOI on air entrainment. Because the other tests evaluated in this research showed more promise (e.g., foam index, CFA iodine number, and direct adsorption isotherm tests), the foam drainage test was not further considered in this research. Foam Index Test Preliminary Screening of Published Test Methods Numerous procedures exist for the foam index test (see Attachment C). The foam index test is inherently subjective in determining what constitutes a “stable foam.” The various published versions include a range in test variables that must be considered (e.g., mass of CFA and cement in the slurry,

13 AEA solution strength and addition rate, the agitation time, and the overall test time). Another minor yet significant vari- able is the dimensions of the test container. Because of the extensive number of published tests and the multiple varia- tions of the test, it was decided to evaluate these tests for subjec- tivity, reproducibility, and ease of use (additional discussion of the test evaluation is presented in Attachment C). The evalua- tion found the test proposed by Harris et al. (2008a, 2008b, 2008c) presents the best combination of precision, analysis time, and simplicity of approach and was therefore consid- ered for a proposed standard test method. However, a num- ber of modifications were considered. Standardized Shaking The process of evaluating the various foam index tests also considered ways of modifying and improving each test with regards to accuracy, reproducibility, or ease of performance. One common concern with all tests was the reproducibil- ity of the agitation process. It was clear that a technician could affect the test results by the vigor with which the agi- tation (i.e., shaking of the container) was performed. Dif- ferent technicians could be linked to differences in results. Therefore, it seemed necessary to standardize the agitation process. A very common piece of laboratory apparatus employed was an automated shaker such as the apparatus shown in Figure 3.1. The automated shaker performs similar to a human hand shaking a bottle, ensures repeatable results, and allows a technician to perform multiple tests simultane- ously. Because of the bottle type, the Harris procedure lends itself to use of an automated shaker. The time of the shake cycle could be varied to allow the user to select the desired time period. Standardizing the agitation of the solution should mini- mize variance due to different agitation methods. To illus- trate, four separate Harris procedure foam index tests were performed using FA-ZG (1.22% LOI). Each test consisted of seven foam index determinations. Two sets of tests were per- formed manually and two used an automated shaker. A sum- mary of the test results is presented in Table 3.3. The use of the automated shaker improved the consistency of the results and greatly reduced the tedium of the test procedure. Another advantage of the automated shaker was the ability to perform multiple tests simultaneously. However, it was deter- mined that, for the operator to have sufficient time to monitor and add AEA to the test specimens during the rest period, a maximum of four concurrent tests could be performed. Optimum Test Duration Another variable in the foam index test is the equilibrium state of the CFA and the AEA solution. Some researchers state Figure 3.1. Harris test using automated shaker. Repetition Shake by Hand Automated Shaker Test 1 Test 2 Test 3 Test 4 1 0.12 0.10 0.10 0.11 2 0.14 0.08 0.10 0.13 3 0.10 0.10 0.10 0.11 4 0.12 0.08 0.10 0.13 5 0.10 0.10 0.12 0.14 6 0.10 0.10 0.12 0.13 7 0.10 0.10 0.10 0.13 Average 0.11 0.09 0.11 0.13 Min 0.10 0.08 0.10 0.11 Max 0.14 0.10 0.12 0.14 Standard Dev. 0.02 0.01 0.01 0.01 Coefficient of Variance (%) 14.12 10.35 9.23 9.02 Table 3.3. Foam index test results using manual agitation and an automated shaker.

14 the test is dynamic and is not based on achieving equilibrium (Külaots et al., 2003); other researchers indicate adsorption equilibrium between surfactants such as AEAs and CFA may take hours (Yu et al., 2000); and others note that equilibrium may be achieved in minutes, depending on the carbon char- acteristics in the CFA (Baltrus and LaCount, 2001). Achieving equilibrium is strongly affected by the combination of materi- als, the drop-wise addition of AEA solution that causes a con- stant change in solution concentration, and the inconsistent waiting period for judging the foam stability after addition of AEA solution to the mixture. Based on the results of numerous foam index tests using dif- ferent procedures, it was determined that a reasonable time to conduct the test and expect the system to be near equilibrium would be between 10 and 20 min. However, to further support this observation, a series of tests was performed using fly ash FA-ZF (6.06% LOI) and AEA-1 to determine an optimal test duration. The tests were performed following the Harris pro- cedure but the solution concentration was varied to achieve different test durations. For each solution concentration, the test was performed with six replicates (i.e., seven individual determinations of the foam index). The coefficient of vari- ance of the foam index value was used to gauge the reproduc- ibility. This statistic, along with the average test duration for each solution concentration, is presented in Table 3.4. Based on these results, 15 ± 3 min was adopted as the target time for completing a test. Researchers have noted the need for adjusting solution concentrations depending on the AEA and CFA being tested (Meininger, 1981; Gebler and Klieger, 1983; Dodson, 1990; Freeman et al., 1997; Külaots et al., 1998, 2003, 2004; Separation Technologies, 2000; Zacarias, 2000; Baltrus and LeCount, 2001; Gurupira, 2005; FHWA, 2006; Grace Construction Pro ducts, 2006; Harris et al., 2008a, 2008b, 2008c; Stencel et al., 2009). Adjusting the solution concentration to match the adsorption characteristics of the ash improves the test in areas other than reproducibility because using a relatively low concentration solution with a highly adsorbent CFA requires numerous additions of AEA, which increases human error and lengthens the testing time. Also, using relatively higher concentrations leads to shorter testing times, but when only a few drops are needed to achieve an endpoint, a single drop may cause a huge variation in the results. Standard Solution Concentrations Identifying standard solution concentrations that satisfy all combinations of fly ash and AEAs would be a desirable provi- sion in a standard foam index test. A numerical analysis was conducted to determine solution strengths using the variables of absolute volume of AEA required to produce a stable foam, initial solution concentration of AEA, and the time to test ter- mination (details are provided in Attachment C). This analy- sis showed that solution concentrations of 2%, 6%, 10%, and 15% AEA by volume provided a range of test solutions that would allow for completion of the test in 12 to 18 min for most CFA sources. Recommended Foam Index Test Procedure For all tests performed using the recommended proce- dure, a 0.02 mL drop size was used for each AEA incremen- tal addition with solution strengths of 2%, 6%, 10%, and 15% by volume. A procedure is proposed for determining the correct solution strength to complete a foam index test in 15 ± 3 min. This procedure is presented schematically in Figure 3.2. As shown in Figure 3.2, the technician performs a foam index test with an initial concentration, for example, 6%. If it is determined that the test will require more than 18 min to achieve a stable foam, the technician increases the concen- tration and restarts the test with a new sample of CFA and cement. Likewise, if the test results in a stable foam in less than 12 min, the technician will decrease the concentration and repeat the test as described. The proposed standard test method is provided in Attachment B. Foam Index Test Application Use of the foam index test was demonstrated with AEA-1 through AEA-6 and a series of CFAs ranging in LOI from 0.25 to 22.3% wt. The CFA sources used are summarized in Table 3.1. For these tests, PC-1 was also used. For the comparison to LOI values, each combination of CFA and AEA was analyzed once with one replicate (i.e., a total of two tests). The results of these tests were averaged to obtain the foam index number for each combination. All foam index Table 3.4. Mean test times and coefficient of variance (CV%) for foam index tests. AEA Concentration 12% 8% 4% 3% 2% Mean Test Time (min) 5.9 10.0 15.0 24.5 31.8 Coefficient of Variance (%) 10.4 7.6 4.6 6.3 7.1

15 tests reported were performed using the proposed procedure and each test was completed within 12 to 18 min. In addition, the results of the foam index test were corre- lated with the results of the CFA iodine number and also the direct adsorption isotherm test. The results of these correla- tions are presented in Chapter 4. CFA Iodine Number Test The iodine number test expresses the adsorption capacity of an activated carbon based on the mass of iodine adsorbed per gram of carbon. Unlike other CFA adsorption capacity indicators such as the foam index test, the CFA iodine number test provides a quantitative measurement for the adsorption capacity of fly ash and can be used directly to characterize and specify CFA for use in portland cement concrete. A signifi- cantly modified version of ASTM D4607-94(2006), Standard Test Method for Determination of Iodine Number of Activated Carbon, was developed in this project. ASTM D4607 is intended for use with activated carbon, which is highly adsorbent relative to carbon in CFA. Because of the sulfur content, lime content, and the low adsorption capacity of CFA, this ASTM method should not be used. To address these issues, a new CFA iodine number test was developed that is very different from the current ASTM test although it is based on the same fundamental principle of measuring the adsorption capacity of CFA (i.e., the mass of iodine adsorbed per gram of ash). Figure 3.2. Proposed protocol for determining the optimum AEA concentration.

16 The CFA iodine number test is determined from a four- point isotherm. That is, four pre-specified masses of treated CFA are equilibrated with an iodine-water solution and the reduction in iodine liquid-phase concentration is represented as capacity using the Freundlich isotherm equation. The CFA iodine number is defined as the capacity of CFA for iodine at an equilibrium concentration of 0.01 N. Details on developing the test are provided in Attachment C. Recommended CFA Iodine Number Test Procedure The recommended CFA iodine number test procedure is provided in Attachment B. A summary of key points is provided below. CFA Treatment. To treat each CFA, the sample is boiled for 5 min in a solution of 5% wt HCl. The total mass of boil- ing solution should be at least four times that of the CFA to be treated to ensure the availability of enough HCl to remove all sulfur and acidify the fly ash. The CFA is then filtered using Grade 1 90 mm diameter, cellulose, qualitative filter paper and dried at 103°C to a constant weight. Mass of Coal Fly Ash Used. In most cases, masses of 80, 40, 20, and 10 g each of CFA were found to be sufficient to produce a suitable and measurable reduction in iodine con- centration for CFA with low and medium carbon content. For ash with a high carbon content, 80, 40, or even 20 g may adsorb all the iodine from the solution and result in an unus- able isotherm point. In this case, CFA dosages of 10, 5, and 2.5 g or even less can be used. Iodine Concentration Measurement. The aqueous phase iodine concentration is measured using the proce- dure presented in Standard Methods for the Examination of Water and Wastewater (Method 4500-CI) (Eaton et al., 2005). The solid phase iodine concentration, or CFA capacity, is determined using a mass balance on the isotherm point as described in Equation 3.2. ( )× = × + × 3.2o o f f CFA CFAV C V C q M Where: Vo = initial iodine solution volume, L Co = initial iodine solution concentration, mg/L Vf = final iodine solution volume, L Cf = final iodine solution concentration, mg/L qCFA = solid phase iodine concentration (capacity), mgiodine/gCFA MCFA = mass of fly ash, g Iodine Number Determination. The four isotherm points are plotted on a log-log scale and a power fit results in the parameters for the Freundlich isotherm equation (Crit- tenden et al., 2005): ( )= ×K 3.31q C n Where: q = mass of adsorbate adsorbed per unit mass of adsor- bent, mg/g K = Freundlich isotherm capacity parameter, (mg/g) (L/mg)1/n C = solution concentration, mg/L 1/n = Freundlich isotherm intensity parameter, dimensionless In the case of the iodine number test, the Freundlich iso- therm equation is used to describe the correlation between the iodine solution concentration and the solid phase iodine concentration, or CFA capacity (i.e., mgiodine/gCFA). After deter- mining the Freundlich isotherm parameters, the CFA iodine number can be determined by using 0.01 N (1,270 mg/L) as the iodine aqueous phase concentration in Equation 3.3. CFA Iodine Number Application Use of the CFA iodine number test was demonstrated using 14 CFA sources; the results are presented in Chapter 4. Direct Adsorption Isotherm Test The fundamental tool for understanding adsorption capacity of organic chemicals onto carbon is the adsorption isotherm. An adsorption isotherm can be used to quantify the adsorption capacity of an adsorbent (i.e., carbon in CFA) and describe the equilibrium relationship between an adsorbent and an adsor- bate (i.e., AEA or iodine). The test can be easily performed using conventional laboratory equipment (e.g., flasks, beakers, stir plates). To perform an adsorption isotherm, a mass of adsor- bent (i.e., grams of CFA) is mixed with a solution of adsorbate (e.g., milliliters of AEA per liter of solution) for a prescribed period of time sufficient for adsorption to occur. After the pre- scribed time, the reduction in solution concentration of adsor- bate is determined. This process is repeated using a different quantity of adsorbent for additional isotherm data points. An alternative approach is to use the same mass of adsorbent for each isotherm point and vary the solution concentration. The results of the tests for each isotherm data point are plotted on a log-log scale and the data are fit with a power line fit; the slope and intercept of which determine the constants for the Freun- dlich equation (Equation 3.3) except that q (i.e., capacity) is expressed as milligrams of AEA per gram of CFA. Once the constants K and 1/n in Equation 3.3 are determined for a given adsorbent and adsorbate, the relationship can be

17 used to determine the amount of adsorbate removed for any adsorbate solution concentration. The test method presented here is based on ASTM D3860-98(2008), Standard Practice for Determination of Adsorptive Capacity of Activated Carbon by Aqueous Phase Isotherm Technique, with modifications made to allow its use with CFA. Measurement of AEA Solution Concentration Measuring AEA concentration is problematic since AEAs are mixtures of complex organics. Spectroscopic methods have been used by many researchers to describe the concentra- tion of AEAs. However, the results were always characterized with low accuracy due to the dilution of the sample and the instability of AEA compounds. Several attempts to use total organic carbon measured by the ultraviolet (UV)/chemical (persulfate) oxidation for determining AEA concentration have been unsuccessful. Preliminary tests conducted in this research showed that UV/chemical (persulfate) is a relatively weak oxidant and fails to fully oxidize the complex organic polymers in an AEA mixture. The chemical oxygen demand (COD) test is often used to measure the dissolved organics in water. The COD test uses extreme oxidation conditions through a strong oxidizing agent [potassium dichromate (K2Cr2O7)], strong acid [sul- furic acid (H2SO4)], and high temperature (150°C). Nearly all organic compounds are oxidized to CO2 and measured as milligrams of oxygen consumed per liter of water. To evaluate this approach, serial dilutions of AEA-1, AEA-2, and AEA-5 were made and tested with the commercially available HACH COD kit (TNT821 and TNT822) and DR5000 UV-Vis spec- trophotometer. Based on the findings of these tests, this approach was adopted and the terms “AEA concentration” and “COD concentration” are used synonymously. Quantifying the adsorption behavior of CFA requires an understanding of the behavior of AEA with each component that makes up the concrete system. Mixtures of AEA solutions and gravel, sand, cement, and different CFAs were investigated to determine the effect of each material on the AEA concen- tration and how AEA partitions in these mixtures. Sorption of AEA onto these materials was divided into chemisorption due to the ionic nature of the material and the AEA, and physical adsorption due to the presence of adsorptive material such as carbon. Details are provided in Attachment C. AEA Interaction with Cement Because cement minerals have an ionic nature, AEAs inter- act strongly and rapidly with cement. AEA molecules bond to the cement particles via electrochemical bonding (i.e., ionic or covalent), removing the AEA molecules from the solution to the particle surfaces. The sorption process, called “chemi- sorption,” is stronger than physical adsorption and is irre- versible under normal conditions. Figure 3.3 illustrates the partitioning of AEA in the case of an AEA solution being equilibrated with various masses of cement. With the addition of only a few grams of cement, the initial AEA solution concentration (C0) for all AEAs tested decreased to a final solution concentration of less than half of C0 (i.e., C/Co < 0.5). After adding approximately 10 g of cement, AEA solution concentrations reached a steady level and remained constant regardless of the addition of more cement. This behavior indicates part of the AEA chemisorbs on cement particles early, removing that portion of the AEA from the solution. As the cement content was increased, no more chemisorption occurred even though more active adsorption sites were added (i.e., more cement). The AEA left in the solution is designed by the AEA manufacturers to stay in the solution and participate in stabilizing the air bubbles. The AEA left in the solution after chemisorption is called the “aqueous phase AEA,” designated as C. The ratio of the equi- librium aqueous phase AEA concentration to the initial AEA solution concentration is referred to as the “partitioning coef- ficient,” shown as C/C0 in Figure 3.3. To use ASTM D3860 with CFA, understanding and correct- ing for the partitioning of AEA was a necessary modification. Details of these modifications are provided in Attachment C. AEA Interaction with Aggregate Equilibration of 0.4% vol. AEA-1 and 0.4% vol. AEA-2 with sand and gravel showed no significant change in the AEA concentrations, suggesting no interaction between AEAs and aggregate. Based on this finding, aggregate was excluded from the isotherm system. 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0 50 100 150 200 A EA C /C 0 Mass of Cement (g) AEA-1 AEA-2 AEA-3 AEA-4 AEA-5 AEA-6 AEA-7 AEA-8 AEA-12 Figure 3.3. AEAs concentration change versus mass of cement.

18 Adsorption Isotherms The solid phase capacity as well as the initial concentration of the adsorbate governs the amount adsorbed on the solid phase and hence, by difference, the amount of adsorbate remaining in the aqueous phase. The results of the isotherms describe this two-phase equilibrium relationship and can be used to determine the partitioning of the adsorbate between the solid and aqueous phases. For a concrete system, only cement and CFA affect adsorption of AEA. Slag cement was evaluated in this research and performed the same as portland cement with respect to adsorption; results are provided in Attachment C. Two methods of performing adsorption isotherms were evalu- ated. In one method, cement and CFA isotherms are performed separately and, in the other method, isotherms are performed on a combination of cement and CFA. It was determined that an adsorption isotherm based upon a combination of CFA and cement was required to accurately assess adsorption capacity of CFA. Additional discussion of this approach is provided in Attachment C. Recommended Procedure for the Direct Adsorption Isotherm Test Overview. Direct adsorption isotherms are based on equi- librating mixtures of cement, CFA, and AEA solutions to deter- mine the reduction in AEA aqueous phase concentration due to adsorption by the carbon portion of the CFA. Cement is included in the isotherm to quantify the chemisorbable por- tion of the AEA. An AEA chemisorption isotherm on cement is used as a blank sample to determine the aqueous phase con- centration available for adsorption by the CFA. The aqueous phase concentration of the blank is considered to be the initial aqueous phase concentration for determining the CFA iso- therm. The reduction in this concentration that results from adding CFA to the system is then used to determine the mass of AEA adsorbed by CFA. CFA capacity is expressed as the ratio of AEA volume adsorbed by CFA to the mass of CFA tested. The process described above results in one isotherm point. Other isotherm points are obtained by varying the concen- tration of the AEA solution. Multiple isotherm points can be analyzed using the Freundlich isotherm model that describes the correlation between solid phase (i.e., CFA) capacity and the final AEA aqueous phase concentration. A COD test is used to determine the concentration of AEA in the solution. AEA solutions were prepared on a volume basis. A recommended test procedure for performing the direct adsorption isotherm test is provided in Attachment B; key points are provided in the following paragraphs. COD Measurements. COD analyses are performed according to Standard Methods for the Examination of Water and Wastewater (Eaton et al., 2005) Method 5220C (closed reflux titrimetric method) or Method 5220D (closed reflux colorimetric method). Use of commercially available kits for performing these tests reduces human error. AEA Solution Concentrations. Three AEA solution concentrations are used to obtain a three-point isotherm for a constant mass of adsorbent and fly ash. Although any three concentrations in the range of practical interest are appro- priate, three AEA aqueous phase concentrations distributed between 300 and 1,300 mg/L COD are preferred for the COD test used. Since most of the AEA mass is chemisorbed into cement particles, it is important to perform a trial blank test that contains 20 g of cement and 200 mL of a known concen- tration of the AEA solution. The ratio of initial solution COD concentration to the final COD concentration, after equili- bration with cement, is used to estimate the three initial con- centrations that will be used with cement and CFA to yield equilibrium concentrations between 300 and 1,300 mg/L. Isotherm Point Setup. To determine all isotherm points, the CFA samples are equilibrated in a 250 mL Erlenmeyer flask at 20°C for 1 h. The AEA solution volume is measured using a 200 mL volumetric flask prior to its addition to the isotherm bottle. A magnetic stirrer is used to keep the contents of the isotherm flask mixed for the entire equilibration time. The solution is filtered using 11 µm filter paper in a vacuum apparatus. The filtrate volume is measured with a 200 mL graduated cylinder. Chemical Oxygen Demand of Solid Materials. To deter- mine the contribution of the CFA to the total COD of the isotherm point solution, 200 mL of distilled water is added to 80 g of CFA in a 250 mL flask. The solution is stirred using a magnetic stirrer for 60 min then filtered using 11 µm filter paper in a vacuum apparatus. COD measurements of the fil- trate provide the concentration of COD released from CFA. The total mass of COD released from CFA in the 200 mL flask can be determined by multiplying the COD concentration by the volume of the solution in the flask. The COD contribu- tion of the cement is compensated for by using 20 g of cement in the blank sample and 20 g of cement in the isotherm data point samples (i.e., the COD contribution of the cement can- cels out in this process). Blanks. A blank sample that contains only cement is required for each initial concentration of AEA utilized. The purpose of the blank sample is to determine the concentration of AEA retained in the solution (i.e., aqueous phase AEA) after chemisorption. Upon introducing CFA to the system, any reduction of this aqueous phase AEA concentration is attrib- uted to the adsorption by the CFA material.

19 Isotherm Points. For each isotherm point, 40 g of CFA is added to the system. The isotherm point is determined using 20 g of cement, 40 g of fly ash, and 200 mL of AEA solution. Upon adding the solution to the CFA and cement in a 250 mL flask, the mixture is stirred using a magnetic stirrer for 60 min then filtered using 11 µm filter paper in a vacuum apparatus. Then COD measurements for the filtrate are taken. Mortar and Concrete Mixtures to Evaluate Developed Tests To evaluate the applicability of the direct adsorption iso- therm test for measuring the effects of CFA on air entrainment, a series of mortar and concrete experiments were conducted. For these experiments, control mixtures were prepared using cement only and a dosage of AEA predetermined to achieve a target air content. Test mixtures were prepared with cement, a 25% substitution of CFA (by mass of cement), and admix- ture dosages intended to achieve air contents similar to those of the controls. The test mixture AEA dosages were deter- mined both by trial and error and by estimating the dosage from the results of the direct adsorption isotherm test using Equation 3.4. AEA Dosage = Capacity WT AEA Dosage 3.4 CFA CFA Baseline ( ) ( ) × + Where: CapacityCFA = AEA capacity from adsorption iso- therm, mLAEA/gCFA WTCFA = weight CFA in mortar mixture, g AEA DosageBaseline = AEA dosage for cement-only mixture, mL All mortar mixtures were prepared in accordance with pro- cedures in ASTM C109 and the air content of the mixtures was determined using the procedure described in ASTM C185-08, Standard Test Method for Air Content of Hydraulic Cement Mortar. Mortars and concrete were prepared using PC-1 and PC-3 separately. No difference was detected in the performance of the AEAs with either cement; therefore, only the results from PC-1 will be presented. Control Mortar Mixtures The control mortar mixtures were prepared with the following: • Sand – 2,905 g • Cement – 838.9 g • Water-cementitious material ratio (w/cm) – 0.45 • Paste/aggregate volume ratio – 1.70 The paste/aggregate ratio was determined on an air-free basis. The fine aggregate used was a washed, natural, siliceous gla- cial sand. Seven AEAs from Table 3.2 were used to make seven separate control mixtures: AEA-1 through AEA-6, and AEA-9. A limited number of mixtures were prepared using AEA-9 to confirm results obtained with AEA-5. It was impossible to achieve similar air contents in all control mixtures without having very significant differ- ences in the AEA dosage level for each AEA. In some cases, the required AEA dosage would need to exceed the manu- facturers recommendations by an order of magnitude. The midpoint of the manufacturer’s recommended dosage range was used to prepare the control mixtures and the resulting average air content was used as the target air content for that mixture design. Because the purpose of the mortar tests was to evaluate the applicability of the direct adsorption isotherm test for estimating AEA dosage, it was not necessary to have the same air content in each control mixture. The plastic air content for each batch of mortar was mea- sured with two replicates and the average of these three mea- surements was used as the air content for that batch. A total of 17 batches was prepared for each control mixture providing 17 average air content values, the averages of which are presented in Table 3.5 together with the AEA dosages used. For each batch, 4 in. by 2 in. cylinder specimens were prepared, wet-cured for Air Entrainer Manufacturer Recommended (oz/cwt) Control Mixture Dosage (oz/cwt) Resulting Average Target Air Content (% vol.) AEA-1 0.2–4 2.1 8.9 AEA-2 0.12–1.5 0.8 5.3 AEA-3 0.2–1 0.6 5.6 AEA-4 0.5–3 1.8 7.2 AEA-5 0.5–1 1.8* 6.7 AEA-6 0.2–3 1.5 6.6 * AEA-5 required twice the manufacturer’s maximum recommended dosage to achieve the minimum air content. Further discussion is provided in Chapter 4. Table 3.5. Control mortar mixtures AEA dosages for each air entrainer.

20 28 days, and then processed for hardened air determination using a modified version of ASTM C457/C457M-11, Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete. The measurements were performed using a flatbed scanner (Sutter, 2007). Mixtures with Coal Fly Ash Table 3.1 lists the sources of CFA used in preparing the mortar test mixtures. Although the CFA was substituted for cement on a weight basis, it was important to ensure the total paste volume for the control mixtures and the CFA mixtures remained the same. Therefore, the total weight of cementi- tious material and water added for the CFA mortar mix- tures was less than used in the control mixtures because of the lower specific gravity of the fly ash relative to portland cement. However, the CFA remained at 25% of the portland cement by mass and the w/cm remained at 0.45. Table 3.6 presents the total cement, fly ash, and water used in the CFA mortar test mixtures, and the specific gravity of each ash. To determine the AEA required to achieve the target air content for the CFA test mixtures, a trial-and-error approach was used. First, the CFA mixture was prepared using the con- trol mixture dosage. Then, six additional batches were pre- pared with an incremental change in the AEA dosage for each batch, resulting in mortars with air contents above and below the target air content. The measured air content was consid- ered to match that of the control mixture air content if it was within ± 0.5% vol. air. Once a test mixture with the target air content was established, that mixture design was repeated to validate the mixture proportions. For each batch, 4 in. by 8 in. cylinder specimens were made, wet-cured for 28 days, and later used for hardened air determination. A second set of mortar test specimens with 25% replace- ment of cement with CFA was prepared with an AEA dos- age estimated using the direct adsorption isotherm method. In this method, the AEA adsorbed by the mass of CFA was calculated, and the AEA dosage of the control mixture was increased by this amount. Control Concrete Mixtures The control concrete mixtures were prepared with the following: • Cement – 564 lb/yd3 • w/cm – 0.44 • Coarse/fine aggregate weight ratio – 60/40 • Aggregate/Paste volume ratio – 2.1 The fine aggregate was washed, natural, siliceous glacial sand meeting the specifications of ASTM C33/C33M-11a, Standard Specification for Concrete Aggregates. The coarse aggregate was a crushed siliceous glacial gravel meeting the requirements of ASTM C33 #67 grading. AEA-1, AEA-2, and AEA-6 (from Table 3.2) were used to make three separate control mixtures with dosages of 1.9, 1.7, and 2.1 oz/cwt cement, respectively. The dosages were estab- lished by trial and error to attain a total air content of 6.5% ± 1.5%. Air contents of the fresh concrete were determined using ASTM C231/C231M-10, Standard Test Method for Air Content of Freshly Mixed Concrete by the Pressure Method. Mixtures with Coal Fly Ash A 25% by weight substitution of CFA for cement (i.e., 141 lb/yd3) was used. The paste to aggregate ratio was held constant when the CFA was introduced to the mixture by adjusting the volume of aggregate used in each mixture. All mixtures were prepared in duplicate. Three CFA sources were evaluated (see Table 3.1). Two sets of concrete test mixtures with CFA were pre- pared. One set was used to show how the mortar mixture designs with CFA relate to the concrete mixture designs with CFA. For these test mixtures, the AEA dosage used was based on the results for mortars that used the same combination of AEA and CFA. For example, if a mortar mixture with a particular CFA-AEA combination required a 50% increase in AEA dosage, then the AEA dosage for the concrete mix- tures of the same combination was increased by 50%. The second set of mixtures was used to evaluate the efficacy of the direct adsorption isotherm test for predicting AEA dos- ages in concrete. In this method, the AEA adsorbed by the mass of CFA in the concrete mixtures was calculated, and the AEA dosage of the control mixture was increased by this amount. Air Determination for Mortars To determine air-void system parameters, slabs were cut from samples of hardened mortar, ground, and lapped. Lapped slabs from 11 of the mortars were analyzed following ASTM C457 Method B to establish data for calibration of the Table 3.6. Mixture design for the CFA mortar test mixtures. ID Cement (g) CFA (g) Sand (g) Water (g) CFA Specific Gravity FA-H 597.4 199.1 2,905 379.9 2.08 FA-T 612.1 204.0 2,905 388.7 2.48 FA-A 605.6 201.9 2,905 384.9 2.19 FA-O 609.8 203.3 2,905 387.4 2.41 FA-J 612.7 204.2 2,905 389.1 2.50 FA-G 606.4 202.1 2,905 385.3 2.31 FA-ZN 606.7 202.2 2,905 385.5 2.32 FA-ZM 606.7 202.2 2,905 385.5 2.32

21 automated method. These 11 slabs were then inked with black marker to render the solid constituents black. A white powder (ground wollastonite) was packed into the voids, and the pre- pared slabs were scanned on a flatbed scanner ( Sutter, 2007). The scanned images were analyzed using a system based on ASTM C457 Method B to develop calibration constants for use in the remainder of the analyses. Slabs from mortars prepared with FA-G, FA-H, and FA-J were polished, treated, and scanned. The mortars having air contents approximating that of the control mortars were ana- lyzed. Slabs from the hardened control mortars were also pre- pared, scanned, and analyzed. All six AEAs were evaluated for each of the mortars in a total of 36 individual analyses (i.e., 18 control mortars and 18 mortars containing fly ash). Assessment of ASR Mitigation The purpose of this study was to evaluate different approaches for determining the effectiveness of a CFA for mitigating ASR and to evaluate new procedures for assess- ing this important property of CFA used in portland cement concrete. Currently AASHTO M 295 stipulates mortar bar expansion limits based on ASTM C441 (as modified in ASTM C311). In the ASTM C441 procedure (also known as the Pyrex mortar bar test), mortar bars are made with high-alkali cement (0.95% to 1.05% Na2Oe) and different replacement levels of CFA and stored at 38°C, and the percentage reduc- tion in expansion due to the pozzolan or slag is calculated. AASHTO M 295 requires the expansion of the CFA mixture to be not greater than that of a control mixture contain- ing low-alkali cement. However, laboratory programs typi- cally test a fixed 20% by mass CFA replacement to rank CFA sources in terms of their relative ability to reduce expansion, not to determine a required level of fly ash. A better approach, which is allowed in ASTM C311, would be to test a CFA at dif- ferent cement replacement levels to determine the minimum attainable level of expansion. To investigate if the ASTM C1567-11 rapid mortar bar test provides better guidance than ASTM C441, tests were con- ducted on concrete prisms according to ASTM C1293-08b, to provide a reference. Also, use of the alkali leaching test as an alternative approach to either the ASTM C441 or ASTM C1567 tests was investigated. Procedure for Evaluating ASTM C1567 and C1293 The specimens for ASTM C1567 and ASTM C1293 tests were made using cement PC-3 because it meets the require- ments of both tests. The alkali-silica reactive aggregate used was crushed gravel from Sudbury, Ontario, containing reac- tive argillites and greywacke. The eight CFA sources listed in Table 3.1 were used (and also used in the strength activity tests). Concrete Prism Tests. For the ASTM C1293 tests, 707 lb/ yd3 of cementitious material that combines PC-3 with CFA replacement levels of 0%, 20%, 30%, and 40% was used. Reagent NaOH was added to the mix water to obtain an alkali equivalence of 1.25% by mass of cement and the alkali load- ing of the concrete of 8.8 lb/yd3 for the 100% cement control mixture. Although the mill certification noted the Na2Oe to be 0.86%, it was later determined to be 1.06%, causing an overdose of alkalis in all the concrete mixtures (i.e., the con- trol actually had 10.3 lb/yd3 of Na2Oe). This higher alkali con- tent will result in higher expansions than should be obtained from the standard ASTM C1293 test. The levels of CFA replacement used were selected to cover the range required by the AASHTO PP 65-11, Standard Prac- tice for Determining the Reactivity of Concrete Aggregates and Selecting Appropriate Measures for Preventing Deleterious Expansion in New Concrete Construction. According to this practice, the Sudbury aggregate would be considered as mod- erately reactive (R1). Therefore, the required CFA replacement levels required for ASR mitigation of pavements exposed to de-icer salts (i.e., Level 4 and Class S3) would be prevention level Y. For CFA with CaO contents of less than 18% and alkali contents of less than 3%, the required level of cement replacement would be 25%. For CFA with alkali contents of up to 4.5%, the required level of cement replacement would be 30%. Calcium and alkali levels for the eight fly ashes are shown in Table 3.7. According to Table 6 of AASHTO PP 65, the required cement replacements would be 30% for FA-M and 25% for FA-H, FA-O, and FA-Q. However, because the other four Class C fly ashes have CaO contents greater than 18%, this table cannot be used. Concrete mixtures were prepared and consolidated into molds with the aid of a vibrating table. Three prisms were Table 3.7. Cement replacement levels based on AASHTO PP 65. CFA Source FA-H FA-M FA-O FA-Q FA-U FA-X FA-ZA FA-ZC CaO (%) 3.46 7.17 10.2 16.6 21.9 19.3 27.3 30.2 Na2Oe (%) 2.27 4.23 2.04 1.63 2.15 6.85 3.97 2.50 min. % Fly Ash 25 30 25 25 X X X X Note: An X indicates that Table 6 of AASHTO PP 65 cannot be used.

22 cast with studs for length change measurements, and a fourth prism was cast for potential petrographic analysis. After cast- ing, the molds were covered with wet burlap and plastic to reduce surface drying. The prisms were de-molded after 24 h, initial length measurements were taken, and then sealed inside 5 gal plastic pails above water with moist filter paper around the sides (per ASTM C1293). The prisms were never soaked in water to avoid leaching alkalis from the hardened concrete. However, this does mean that some of the early length change can be from moisture absorption and not ASR-related expan- sion. For this reason, the 7-day reading rather than the initial 1-day reading was used as the datum reference reading. At 1 day of age, the pails containing the concrete prisms were placed in a curing room controlled at 38°C, removed from the curing room the day prior to measurements and cooled to 23°C, and returned to the curing room after length change measurements were completed. Length changes were measured at the intervals required in ASTM C1293 and averaged for the three prisms. Accelerated Mortar Bar Tests. Accelerated mortar bar tests were conducted in accordance with ASTM C1567. All eight CFA sources were tested using a full factorial design with portland cement PC-3 replacement at 0%, 20%, 30%, and 40% wt. In addition, FA-H was tested at 10% and FA-X and FA-ZA were tested at 50% wt replacement. The mortar bars (1 in. by 1 in. by 11.25 in.) were cast for each mixture. For the first 24 h after mixing, the molds were placed in sealed containers above water to maintain a humid environment. The bars were then de-molded and immersed in water, in sealed containers, and placed in an oven at 80°C. Initial length measurements were made at 2 days in accor- dance with ASTM C1567. The bars were then immersed in NaOH solutions preheated to 80°C, and length change was measured at 14 and 28 days, and other intermediate ages. Alkali Leaching Tests. The alkali leaching test (Shehata and Thomas, 2006) was evaluated as a possible test for deter- mining if a cement-CFA combination is effective in mitigating ASR. In this test, cement paste samples are ground to a powder and then immersed in 0.25 mol/L OH- solution using equal concentrations of NaOH and KOH. The solutions are measured for Na+, K+ and OH- after 7 and 28 days of leaching. The change in concentration of the solution is calculated to determine the quantities bound to or released from the cement paste. Details of the alkali leaching test are provided in Attachment C.