Entrained Air-Void Systems for Durable Highway Concrete (2021) / Chapter Skim
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From page 11... ...
11 Experimental Program Research Scope and Approach To achieve the objectives of the project, the experimental program included the following steps: • Pavement sections with F-T related distress were identified across the U.S. and Canada.
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12 Entrained Air-Void Systems for Durable Highway Concrete Cement Fly Ash Natural PozzolanLA HA TIL FA 4 FA 5 SiO2 21.08 19.82 20.07 40.72 38.49 56.99 Al2O3 4.19 5.43 4.90 20.45 21.92 38.06 Fe2O3 3.27 2.07 3.43 6.08 6.04 1.73 SO3 2.95 3.80 3.28 1.02 1.04 0.02 CaO 64.27 63.36 65.50 21.61 22.43 0.05 MgO 2.42 3.00 0.94 4.35 4.17 0.11 K2O 0.53 1.05 0.69 0.63 0.60 0.25 Na2O 0.13 0.36 0.13 1.36 1.53 0.00 P2O5 0.06 0.28 0.16 0.83 1.10 0.19 TiO2 0.25 0.24 0.25 1.51 1.57 1.49 BaO 0.58 0.58 0.07 SrO 0.09 0.33 0.19 0.31 0.32 0.02 Mn2O3 0.07 0.10 0.28 0.04 0.05 0.00 LOI (%) 2.00 0.21 1.54 Moisture (%)
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Experimental Program 13 Supplementary Cementitious Materials Two sources of Class C fly ash were selected from the same supplier, one with a more elevated loss on ignition (LOI) than the other.
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14 Entrained Air-Void Systems for Durable Highway Concrete • Binder content = approximately 565 lb/yd3 • Temperature = 70°F Table 5 shows the test matrix used for the laboratory mixtures. The test matrix for the clustering study involved the preparation of 61 concrete mixtures prepared with different binary combinations of cements and fly ashes, different combinations of AEAs and WRAs, and two types of coarse aggregate.
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Experimental Program 15 • Target air content = 6% • Binder content = approximately 549 lb/yd3 • Mixing water temperature = 70°F or 90°F Table 6 shows the test matrix used for clustering mixtures. Test Procedures and Sample Preparation Investigating Air-Void Systems of Concrete in the Fresh State Using the Super Air Meter Data for fresh concrete were obtained by two operators using two different SAMs.
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16 Entrained Air-Void Systems for Durable Highway Concrete Flatbed Scanner The procedure for scanning hardened concrete samples was reported by Appropedia (2017) , Peterson (2010, 2015)
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Experimental Program 17 Source: Kozikowski et al.
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18 Entrained Air-Void Systems for Durable Highway Concrete The CDF-A variant investigated the impact of sample curing time on F-T performance in water. The CDF-B variant replaced the freezing fluid with standard deicer salts similar to ASTM C672 or RILEM Technical Committee (TC)
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Experimental Program 19 the pan was filled with limewater so that the level was 0.20 in.
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20 Entrained Air-Void Systems for Durable Highway Concrete Deicer Scaling. In addition to the standard and modified rapid F-T tests, deicer scaling was performed according to ASTM C672.
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Experimental Program 21 AASHTO T 161 test (40°F to 0°F) , the objective of both tests is to ensure complete freezing and complete thawing during each cycle.
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22 Entrained Air-Void Systems for Durable Highway Concrete Figure 11. Stainless steel tray used to hold coupling fluid and deicer pans.
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Experimental Program 23 Figure 13. ABS stand to support both the freezing pans and the concrete specimens.
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24 Entrained Air-Void Systems for Durable Highway Concrete between air-void system parameters and F-T performance to identify the key parameters and limits that can be used to predict performance. The research team made multiple requests to several state DOTs across the U.S.
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Experimental Program 25 system. A general overview of the pavement conditions and available mix design information gathered from each of the investigated locations follows.
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26 Entrained Air-Void Systems for Durable Highway Concrete Minnesota MnROAD Research Facility As part of the Strategic Highway Research Program (SHRP) , test sections were built at the MnROAD facility in 1992 to monitor long-term resistance of concrete to freezing and thawing (Janssen 2006)
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Experimental Program 27 but it was much less severe than that affecting the ON-417 cores. Test results provided by the Ontario Ministry of Transportation were used in the analyses.
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28 Entrained Air-Void Systems for Durable Highway Concrete Aside from the top surface, the concrete appeared to be in fairly good condition. The air-void content was 2.5%; some of the microcracking in the concrete may be attributed to F-T.
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Experimental Program 29 air entrained, but an estimated half of the air-void volume was attributed to small entrapped and possibly coalesced air voids. Also, air content appeared to be lower near the surface of the concrete than at greater depth, largely due to reduction in the coarser entrapped air voids.
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30 Entrained Air-Void Systems for Durable Highway Concrete Minnesota US-52 MnDOT staff provided the following mixture design information: • Cement: Type I cement, 493 lb/yd3 • SCM: Class C fly ash 87 lb/yd3 • Water: 244 lb/yd3 • Coarse aggregate over 3⁄4 in.: 1,123 lb/yd3, specific gravity of 2.66, and water absorption of 1.6% • Coarse aggregate under 3⁄4 in.: 746 lb/yd3, specific gravity of 2.65, and water absorption of 1.7% • Fine aggregate: 1,200 lb/yd3, specific gravity of 2.62, and water absorption of 0.8% • W/cm ratio: 0.42 • Design fresh air (%) : 5.5 The data obtained from testing the air-void systems of the core specimens are listed in Table 13.
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Experimental Program 31 Core # Pavement Distress Coring Location Air (%)
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32 Entrained Air-Void Systems for Durable Highway Concrete Michigan The available mixture design information provided by Michigan DOT staff is summarized as follows: • Cement: Type I cement, 526 lb/yd3 • SCM: N/A • Water: 236 lb/yd3 • Coarse aggregate: 1,692 lb/yd3, 3⁄4 in. maximum aggregate size, and specific gravity of 2.63 • Fine aggregate: 1,338 lb/yd3, specific gravity of 2.71, and fineness modulus of 2.65 • W/cm ratio: 0.45 • Design fresh air (%)
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Experimental Program 33 The data obtained from testing the air-void systems of the core specimens are listed in Table 17. Ohio The hardened air-void system of the concrete was investigated for all cores.
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34 Entrained Air-Void Systems for Durable Highway Concrete Core # Pavement Distress Coring Location Air (%)
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Experimental Program 35 Core # Pavement Distress Coring Location Air (%)
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36 Entrained Air-Void Systems for Durable Highway Concrete Geographic Location Core # Type of Distress Scaling Rating (ASTM C672) Overall Performance M ic hi ga n 1 F-T, Potential Oxychloride NA Poor Joints 2 Scaling 2 Good 7 Scaling 2 Good 8 Scaling 2 Good M an ito ba , C an ad a 1 F-T, Scaling, Potential Oxychloride 5 Poor 2 F-T, Scaling, Potential Oxychloride 5 Poor 3 F-T, Scaling, Potential Oxychloride 5 Poor 5 F-T, Scaling, Potential Oxychloride 5 Poor O hi o 1 Spalling NA Poor Joints 2 No Distress 0 Good 3 Spalling NA Poor Joints 4 No Distress NA Good 5 No Distress 0 Good 6 No Distress 0 Good 7 No Distress NA Good 8 No Distress 0 Good 9 Surface Crack NA Good 10 No Distress 0 Good 11 Spalling NA Good 12 No Distress 0 Good 13 Surface Crack NA Poor Joints 14 No Distress 0 Good 15 No Distress 0 Good M in ne so ta U S52 1 F-T, Potential Oxychloride NA Poor Joints 2 Scaling 2 Good 3 Scaling 1–2 Good 4 Scaling 1 Good 5 Scaling 1–2 Good 6 Scaling 1–2 Good 8 Scaling 1 Good 9 Scaling 1 Good 10 F-T, Potential Oxychloride NA Poor Joints 11 Scaling 2 Good 2 Scaling 1 Good 3 Scaling 1 Good 4 Scaling 1 Good 6 Scaling 1 Good 7 Scaling 1 Good So ut h D ak ot a 2 F-T, Potential Oxychloride NA Poor Joints 3 Scaling 2 Good 5 F-T, D-Cracking, Scaling 2 Good 6 Scaling 2 Good 8 Scaling 2 Good M in ne so ta M nR O A D Table 22.
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Experimental Program 37 The air content, spacing factor, and specific surface data were categorized into three levels -- good, marginal, and poor -- based on proposed limits: • Hardened air content – Good: greater than 5.0% – Marginal: 3.5 to: 5.0% – Poor: less than 3.5% • Spacing factor – Good: less than 0.008 in. – Marginal: 0.008 to 0.0108 in.
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38 Entrained Air-Void Systems for Durable Highway Concrete Note: MB-CA = Manitoba, Canada; MI = Michigan; MNROAD = MnROAD; MN- US52 = Minnesota US-52; MO = Missouri; NV = Nevada; NY = New York; OH = Ohio; ON-CA = Ontario, Canada; PA = Pennsylvania; SD = South Dakota; SF = spacing factor. Figure 18.
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From page 39... ...
Experimental Program 39 Note: MI = Michigan; MNROAD = MnROAD; MN-US52 = Minnesota US-52; MO = Missouri; NV = Nevada; NY = New York; OH = Ohio; ON-CA = Ontario, Canada; PA = Pennsylvania; SD = South Dakota. Figure 21.
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40 Entrained Air-Void Systems for Durable Highway Concrete In Figure 21, most of the data points for samples exhibiting acceptable durability fall in the right-bottom corner, corresponding to a spacing factor lower than 0.014 in. and hardened air content higher than 2.2%.
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Experimental Program 41 A test matrix of 144 concrete mixtures was used for evaluation in this study (details are provided in Appendix A)
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42 Entrained Air-Void Systems for Durable Highway Concrete Figure 24 presents the histogram of the variation in fresh air content measured using two different SAMs for the data obtained for the 144 concrete mixtures.
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Experimental Program 43 SAM# -- Measurement 1 SA M # -- M ea su re m en t 2 Figure 25. Repeatability of SAM number measurements using two different meters.
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44 Entrained Air-Void Systems for Durable Highway Concrete SAM Number Versus Fresh Air Content: Effect of Concrete Mixture Properties Data obtained from this study reveal that correlations between air content and SAM number can vary depending on the mixture chemistry. Figure 27 through Figure 29 present the correlation between the average SAM number and average air content measurements that were obtained for the mixtures prepared with LA cement.
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From page 45... ...
Experimental Program 45 For all mixtures, a linear correlation was observed between the SAM number and air content for concrete in the fresh state, and the correlations were similar for the mixtures prepared with stable or unstable AEA for each SCM type. When using LA cement regardless of SCM type and AEA stability, an air content of 6.5% to 7% in the fresh concrete can result in a SAM number of 0.20 or less, which is considered an acceptable SAM number.
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46 Entrained Air-Void Systems for Durable Highway Concrete Air Content. The data from the optical microscopy tests were compared with those from the SAM tests conducted on the fresh concrete.
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Experimental Program 47 Figure 31. Correlation between average fresh air content obtained using SAM test and average hardened air content obtained with fixed-focus optical microscope.
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48 Entrained Air-Void Systems for Durable Highway Concrete Figure 33. Correlation between SAM number and spacing factor.
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Experimental Program 49 Shifting the limit for a good SAM number from 0.2 to a higher value (e.g., 0.40) lowers the probability of obtaining false negatives from the SAM test, while increasing the probability of observing false positives.
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50 Entrained Air-Void Systems for Durable Highway Concrete Air Content. In general, good agreement was observed between the hardened air content measurements obtained from the scanner and the automatic microscope test methods, as shown in Figure 36.
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Experimental Program 51 Figure 37. Comparison between the spacing factor values measured by flatbed scanner and fixed-focus optical microscope.
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52 Entrained Air-Void Systems for Durable Highway Concrete • Increase in temperature of the mixing water from 70°F to 90°F regardless of the fly ash quality, admixture stability, or retempering; • Use of an unstable AEA; and • Use of limestone aggregate. The changes in compressive strength values were compared with changes in clustering ratings obtained for concrete mixtures prepared with the same cementitious materials, aggregates, and admixtures, but with different temperatures of the mixing water.
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From page 53... ...
Experimental Program 53 The relationship established in the laboratory between spacing factor and specific surface, previously discussed, is in good agreement with these observations. For a spacing factor of 0.0114 in., the obtained trend line yields a specific surface of 458 in.–1.
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54 Entrained Air-Void Systems for Durable Highway Concrete • Strong correlations exist between the air content and spacing factor data obtained from the flatbed scanner and those from the fixed-focus optical microscope. • The type of cement is a primary factor in governing the extent of clustering for mixtures not exposed to retempering.
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From page 55... ...
Experimental Program 55 of concrete samples with varying levels and qualities of air systems as determined in this project for selected test parameters. The test plan was designed to explore F-T testing conditions and determine air-void parameter aspects that define F-T performance.
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56 Entrained Air-Void Systems for Durable Highway Concrete In only two cases (Mixtures 14 and 29 retempered) , the SAM number predicted good F-T performance.
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Experimental Program 57 achieved a durability factor > 90% until 240 cycles. In general, the mixtures performed as predicted or better, except for Mixture 29R, which performed worse than predicted probably due to the form of the air-void system induced by the retempering.
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58 Entrained Air-Void Systems for Durable Highway Concrete 60% 65% 70% 75% 80% 85% 90% 95% 100% 105% 0 10 20 30 40 50 R el at iv e D yn am ic M od ul us (% ) Cycles Mix 2 -- FT 1 (7d)
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Experimental Program 59 60% 65% 70% 75% 80% 85% 90% 95% 100% 105% 0 10 20 30 40 50 R el at iv e D yn am ic M od ul us (% ) Cycles 2 (A, S, N)
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60 Entrained Air-Void Systems for Durable Highway Concrete The F-T techniques altered freezing fluid, method of fluid exposure, timing of F-T cycles, and conditioning techniques. Table 27 shows a summary of the F-T results.
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Experimental Program 61 Note: A = acceptable air content in fresh state, S = stable AEA, N = no significant effect due to SCM use, M = marginal air content in fresh state, NS = unstable AEA. 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 0 5 10 15 20 25 30 35 40 45 50 Sc al in g Se ve ri ty R at in g Cycles Mix 2 (A, S, N)
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From page 62... ...
62 Entrained Air-Void Systems for Durable Highway Concrete The extended CDF-A:FT1 test and AASHTO T 161 "A" yielded comparable performance predictions, matching anticipated performance from air system parameters. Observations showed that retempering improved the air system for Mixture 29, and measured air system parameters did not adequately predict performance, as good performance was anticipated and marginal performance was observed.
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