EVALUTION OF SURFACE RESISTIVITY FOR CONCRETE QUALITY ASSURANCE IN MISSOURI

Transcription

1 TRB2016- Paper Kevern, Halmen, Hudson, and Trautman 1 EVALUTION OF SURFACE RESISTIVITY FOR CONCRETE QUALITY ASSURANCE IN MISSOURI John T. Kevern, Ph.D., PE Associate Professor of Civil Engineering University of Missouri-Kansas City 370A Flarsheim Hall 5110 Rockhill Rd. Kansas City, MO Office: Fax: kevernj@umkc.edu Ceki Halmen, Ph.D., PE Associate Professor of Civil Engineering University of Missouri-Kansas City 350J Flarsheim Hall 5110 Rockhill Rd. Kansas City, MO Office: Fax: halmenc@umkc.edu Dirk P. Hudson, EIT Project Engineer ESI Contracting Corp E 83 St. Kansas City, MO Mobile: dhudson@esi-cc.com Brett Trautman, PE Physical Laboratory Director Missouri Department of Transportation 1617 Missouri Blvd. Jefferson City, MO Brett.Trautman@modot.mo.gov Abstract 212 (250) Text 4019 Tables 4 (250) = 1000 Figures 7 (250) = 1750 Total 6981 (7500 max) November 15, 2015

2 TRB2016- Paper Kevern, Halmen, Hudson, and Trautman 2 ABSTRACT This research evaluated a series of Missouri DOT (MoDOT) concrete mixtures to verify existing relationships between surface resistivity (SR), rapid chloride penetrability (RCP), and the AASHTO penetrability classes. Eleven mixtures were produced in the lab which represent a range of currently allowable mixtures and several mixtures with potential for the future. Classes of concrete mixtures included paving, bridge deck, structural, and repair. Results showed excellent correlation between SR and RCP which matched existing relationships provided by AASHTO and other state DOTs. The structural mixture containing 50% Class F fly ash had the best performance with very low chloride ion penetrability at 90 days. A ternary paving mixture with 20% Class C fly ash and 30% slag replacement for cement also demonstrated low penetrability as well as high compressive strength with an average value of over 9,000 psi at 90 days. The two repair mixtures showed moderate to low penetrability readings and high early strength consistent with their desired purpose. The extensive amount of surface resistivity testing (>4500 tests) on 14 concrete mixtures at ages from 3 hours to 90 days using multiple labs, equipment, operators, and curing conditions has verified RCP. Surface resistivity presents an opportunity to improve MoDOT concrete mixtures and specifications to increase durability without adding significant additional testing costs.

3 TRB2016- Paper Kevern, Halmen, Hudson, and Trautman 3 INTRODUCTION Concrete permeability is arguably the most important factor affecting the long-term durability of both plain and reinforced concrete structures. As Departments of Transportation (DOTs) and Federal Highway Administration (FHWA) move towards end result and performance-based specifications, concrete permeability is becoming an increasingly important consideration and is being tested using the Rapid Chloride Penetrability (RCP) test as a surrogate. RCP test is a highly utilized method for evaluating and predicting concrete performance, however the equipment necessary to run the test is expensive and testing requires significant personnel training and time consuming sample preparation prior to testing. While RCP has been an excellent measure of future concrete performance, the cost for equipment, manpower required to perform testing and the duration of the testing limits the use of RCP testing for quality assurance (QA) in all but the most important projects. Researchers at the Florida DOT and later the Louisiana Transportation Research Center (LTRC) investigated surface resistivity testing as an alternative to rapid chloride penetrability testing (1-8). The state of Louisiana has recently accepted surface resistivity testing to be used as a quality control tool. LTRC researchers predicted over $1,500,000 in savings per year by using surface resistivity in place of rapid chloride penetrability testing (4, 5). Surface resistivity testing equipment is relatively inexpensive (<$5,000), does not require consumable items, requires little training, has been shown highly repeatable, and is non-destructive. Although the Missouri DOT currently performs little RCP testing, this study was initiated because of the potential for improved concrete performance and data for decision making without impacting cost. The objectives of this study were to 1) verify the existing test protocol to measure the surface resistivity (SR) of concrete, 2) verify that relationships reported in the literature represented the range of potential MoDOT mixtures, and 3) investigate the potential for using SR on rapid-setting repair mixtures. The results presented herein are a portion of the overall study and only include specimens produced in the laboratory. Additional testing was performed on fieldproduced specimens and on field core samples. Complete results of the study can be found in Kevern et al. (9). BACKGROUND AND MOTIVATION Concrete and soils are comprised of solid particles, liquid, and water vapor-filled pore spaces. When an electrical charge is passed through these materials, the resistance of the solid and pore spaces are significantly higher than the electrolyte (liquid in pores). Samples with more interconnected fluid-filled spaces pass a higher charge and result in lower resistivity (10). Resistivity testing is commonplace for soils to determine grounding capacity and corrosivity, with higher voltage resistivity systems able to provide subsurface layer mapping. Both bulk and surface resistivity testing have been used on concrete for a number of years but only after soil resistivity had been extensively researched (10, 11, 12). DOTs are using surface resistivity testing for QA and acceptance of newly-placed concrete, verification of in-place properties, and evaluating corrosion potential (primarily on bridge decks). The Florida DOT first standardized surface resistivity testing in 2005 with FM5-578 Florida Test Method for Concrete Resistivity as an Electrical Indicator of its Permeability (13). The Florida DOT, contractors, and producers gained enough confidence that by 2007 surface resistivity replaced RCP test in Florida acceptance specifications. Kessler reported a linear correlation between the log of surface resistivity and RCP results for concrete with water-to-cement ratios (w/cm) varying from 0.28 to 0.49, cementitious materials contents varying from 564 to 900 pounds

4 TRB2016- Paper Kevern, Halmen, Hudson, and Trautman 4 per cubic yard (pcy) containing binary combinations of fly ash, slag, metakaolin, silica fume, and ultrafine fly ash (13). Various factors are known to affect resistivity measurements in concrete with the most significant factor being temperature and moisture content (14). A complete ruggedness study was performed which evaluated the effects of aggregate type, aggregate size, calcium nitrate, lime water curing, segregation, air content, temperature, surface moisture, age, probe spacing, and number of data points collected (6). Temperature and moisture have been discovered as two variables that greatly affect surface resistivity readings. If the temperature of the testing environment or cylinder is much higher than room temperature, the surface resistivity reading will be much lower than expected (10). In terms of moisture, if the concrete cylinder is too dry, the resistivity reading will be higher than expected as well (6). For a single mixture tested under the same environmental conditions, sample age and aggregate type (gravel versus limestone) were the only significant factors for surface resistivity, which were also significant for RCP. The correlation between RCP and surface resistivity obtained in this ruggedness study matched the relationship observed in the Louisiana DOT study (4-6). Many of the previously mentioned studies report precision and bias of the sample data. Reported precision and bias statements in the literature for within lab repeatability and between lab reproducibility are within acceptable limits for the American Society for Testing and Materials (ASTM) standard (15). MATERIALS AND METHODS The mixture proportions for the conventional concrete mixtures are shown in Table 1 and represent a cross section of current and potential mixtures for MoDOT (16). The naming designations start with a letter either P denoting paving, B2 denoting a bridge deck mixture, or S for a structural mixture. The bridge deck category included a B2L designation for the lightweight fine aggregate mixture and MB2 denoting a modified B2 mixture which contained less total cementitious materials. The number series listed after the usage letter indicates the cementitious materials shown as a percentage by weight of cement (C), class C fly ash (A), class F fly ash (F), or blast furnace slag (S). Two mixtures shown in the study are currently outside of MoDOT specifications, the ternary paving mixture and the high replacement class F fly ash mixture. These mixtures have SCM contents higher than allowable but with potential for future application. Internal curing using prewetted lightweight aggregate has been used in Missouri on a very limited basis and B2L would also be novel for MoDOT usage. The fly ashes met ASTM C618 (17) and the slag was grade 120 meeting ASTM C989 (18). The cement is marketed as a Type I/II and meets requirements for both Type I and Type II cements per ASTM C150 (19). The coarse aggregate was a low-absorption limestone from the Cedar Valley ledge in Randolph, MO with a one-inch nominal gradation. The coarse aggregate had a bulk specific gravity of 2.69 and absorption of 0.20% as determined by ASTM C127 (20). The fine aggregate was Kansas River sand meeting ASTM C33 for gradation and with a bulk specific gravity of 2.61 and absorption of 0.4% per ASTM C128 (21). The lightweight fine aggregate was expanded shale from New Market, MO with a gradation meeting No. 4-0 and absorption of 19% per ASTM C1761 (22). When the Bentz equation is used to determine the optimum dosage of lightweight fine aggregate for internal curing based on satisfying chemical shrinkage, the MB2 mixtures would require 241 pcy (143 kg/m 3 ) (23). Since roughly half of the optimum amount of lightweight aggregate was used in this study, additional benefits may be realized with a higher dosage. All mixtures used a vinsol resin air-entraining agent meeting ASTM C260 and a

5 TRB2016- Paper Kevern, Halmen, Hudson, and Trautman 5 polycarboxylate water reducer meeting ASTM C494 Type A and Type F requirements (24, 25). Amounts shown in Table 1 represent percent by mass of the cementitious materials. This study used surface resistivity equipment with a Wenner four pin array with 1.5 inch (38mm) spacing. Testing was performed according to the Standard Test Method for Surface Resistivity Indication of Concrete s Ability to Resist Chloride Ion Penetration, AASHTO TP (26). Following TP95, all surface resistivity data represents an average of eight tests performed at four locations on each cylinder. RCP testing was performed according to ASTM C1202 and AASHTO T277 (27, 28). Compressive strength was performed according to ASTM C39 using 60 durometer neoprene end caps conforming to ASTM C1231 (29, 30). All reported data represents average results for three cylinders. RCP test specimens were all removed from individual cylinders. TABLE 1. Mixture Proportions for the Conventional Concrete P: P: P: B2: B2L: Material 100C 80C-20A 50C-20A-30S 85C-15A 85C-15A MB2: 85C-15A S: 80C-20A S: 50C-50F (pcy) (pcy) (pcy) (pcy) (pcy) (pcy) (pcy) (pcy) Cement Class C Fly Ash Class F Fly Ash Slag Coarse Agg Fine Agg LW Fine Agg Water AEA 0.10% 0.10% 0.10% 0.10% 0.10% 0.10% 0.10% 0.10% HRWR 0.38% 0.25% 0.25% 0.38% 0.25% 0.25% 0.19% 0.25% P=Paving; B=Bridge Deck; S=Structural *1 pcy = kg/m 3 Two additional mixtures were included in this study which represent rapid-setting repair mixtures as shown in Table 2. Mixture R1 contained 50% calcium sulfoaluminate cement (CSA) and mixture R2 ordinary Portland cement, but with a large amount of non-chloride accelerator. Currently the literature lacks information on resistivity behavior of CSA concrete. There is also conflicting information in the literature regarding calcium nitrate accelerators. Some report the additional calcium increases the conductivity of the pore solution and decreases resistivity (13, 26), while others report no difference (6). The mixtures used the same air-entraining and waterreducing admixtures as the conventional concrete. The CSA mixture used citric acid as a retarder and the R2 mixture used a calcium nitrate accelerator meeting ASTM C494 Type C (25).

6 TRB2016- Paper Kevern, Halmen, Hudson, and Trautman 6 TABLE 2. Mixture Proportions for the Repair Mixtures R1:50C-50CSA R2:100C Material (pcy) (pcy) CSA Cement Cedar Valley CA Riversand FA Water AEA 0.10% 0.20% HRWR 1.00% 1.66% Citric Acid Retarder 0.40% - Accelerator % RESULTS and DISCUSSION Sample Testing Condition Verification The current AASHTO standard for surface resistivity TP95 does not provide guidance for the amount of time a cylinder may be out of the curing environment before significantly impacting results. Figure 1 shows the results of a set of control cylinders cured in lime water, removed and blotted off, and then left exposed to standard lab conditions of 70 F (32 C) and 50% relative humidity. As expected resistivity increases with concrete age. Also as expected is the increase in resistivity as the samples dry. Over the course of 30 minutes the resistivity value increases approximately one kohm*cm. Data sets were then compared using t-tests at each amount of exposed time compared to the reference as tested directly after removing from lime water to determine when the increase was significantly different than the reference. For all samples and mixtures cured 14 days or less the tests performed at 5 minutes were not statistically different than the control, but the tests performed at 10 minutes were different. For all samples and mixtures cured 28, 56, or 90 days there was no difference at the 10 minute test time, but the tests performed at 15 minutes were different. To be consistent for all mixtures and ages, it has been recommended that samples be tested within 5 minutes of removing from curing.

7 Surface Resistivity (kohm-cm) TRB2016- Paper Kevern, Halmen, Hudson, and Trautman day 14-day 28-day 56-day 90-day Time (seconds) FIGURE 1. Allowable Time to Test After Removing from Curing (P:100C) In certain conditions, either intentional or accidentally, samples are left in sealed in molds for the duration of curing. Figure 2 shows results of samples left in molds for the duration of curing, stripped, and then placed in lime water for varying times before SR testing. Resaturation was only performed on the ordinary Portland cement paving mixture (P:100C) and results may be different for different mixtures. The trends of increased resistivity with time and increased resistivity compared with the moist samples shown in Figure 1 were expected. Also, it was expected that resistivity would decrease with saturation time. The sets of testing data were again statistically compared to the initial test values shown in Figure 1 to determine when the test result for the resaturated specimens were not statistically different than the initial test values for the samples cured continuously in lime water. The early age specimens reached steady state sooner than the older specimens reflecting refinement of the hydrated pores and densification of the hydration products. All specimens showed a large decrease in resistivity from the dry/sealed condition to the first saturated test time of 15 minutes. After 15 minutes there was a much smaller decrease in resistivity. At the test times of 30 minutes and above there was no statistical difference between the samples cured in the sealed molds and the samples cured in lime water.

8 Surface Resistivity (Kohm-cm) TRB2016- Paper Kevern, Halmen, Hudson, and Trautman day 14 day 28 day 56 day 90 day Time (minutes) FIGURE 2. Required Saturation Time when Cured in Molds (P:100C) Laboratory Mix Results The compressive strength results for the various mixtures are shown in Table 3 also including the data for samples presented in Figure 2. Coefficient of variation is shown as a percentage. All mixtures met or exceeded requirements for the various applications. The highest strength paving mixture was the ternary mixture. The highest strength bridge deck mixture was the modified B2 which had the lower cementitious content. The mixture containing prewetted lightweight aggregate had similar strength at all ages to the conventional mixture with all river sand. The structural mixture designed for low heat generation contained 50% replacement for cement with class F fly ash and had the greatest strength gain from 7 days to 90 days. The repair mixture strength gain reflected the individual cementitious/admixture chemistries. The requirement for the repair mixtures was 4,000 psi at 12 hours. The mixture containing CSA had very rapid strength gain at three hours. The accelerated Portland cement mixture had the greatest strength gain from 6 to 12 hours. Ultimately both mixtures produced strength greater than 10,000 psi. TABLE 3. Compressive Strength Results for the Laboratory-Produced Mixtures Average Compressive Strength, psi (COV %) Mixture 3 hours 6 hours 12 hours 1 day 7 day 14 day 28 day 56 day 90 day P:100C (11.1) (4.3) (3.6) P:100C in Molds (5.9) (5.0) (4.2) P:80C-20A (8.7) (3.3) (3.3) P:50C-20A-30S (0.7) (6.5) (3.7) B2:85C-15A (1.2) (1.5) (3.4) B2L:85C-15A (4.3) (7.1) (4.7) MB2:85C-15A (4.4) (3.0) (3.2) S:80C-20A (2.9) (3.7) (3.8) S:50C-50F (7.5) (2.1) (2.0) R1:50C-50CSA 3460(3.1) 4010(1.8) 4400(6.3) 4720(2.3) 5450(3.0) 57800(0.9) 5710(3.2) 8310(1.3) 10430(1.5) R2:100C 120(8.7) 1390(6.4) 4580(0.6) 6380(2.8) 9160(0.5) 10100(1.9) 11170(1.1) 11690(4.4) 12420(1.8)

9 TRB2016- Paper Kevern, Halmen, Hudson, and Trautman 9 The surface resistivity results for the paving category mixtures are shown in Figure 3. At 90 days the Portland cement and binary mixtures had the same resistivity with the binary mixture containing fly ash showing a continuing trend of densification. The ternary mixture containing 50% replacement of Portland cement with blast furnace slag and fly ash had substantially better performance with the second highest resistivity of all the mixtures tested. FIGURE 3. Surface Resistivity Results for Paving Mixtures Figure 4 shows the surface resistivity results for the bridge deck mixtures. All were classified as moderate resistance to chloride ion penetration at 90 days. There was no difference between the B2 mixture containing 705 pcy (417 kg/m 3 ) of total cementitious and the MB2 mixture containing the same SCM percentage of 15% class C fly ash, but with 600 pcy (355 kg/m 3 ) of total cementitious. Interestingly the B2 mixture containing 135 pcy (80 kg/m 3 ) of prewetted lightweight fine aggregate as a replacement for the conventional sand, had a 20% increase in SR from 16.4 to 20.0 kohm*cm. It is well-understood that prewetted lightweight aggregates release additional water not part of the original mixing water back into the hydrating paste. This internally-supplied water improves the degree of hydration, reducing shrinkage, and creating a denser microstructure (31-34). Although B2L had the same strength as B2, the internal curing created a mixture more resistant to chloride ion penetration.

10 TRB2016- Paper Kevern, Halmen, Hudson, and Trautman 10 FIGURE 4. Surface Resistivity Results for Bridge Deck Mixtures Results for the two structural mixtures are shown in Figure 5. The mixture containing 20% class C fly ash was classified with low penetrability at 90 days and the mixture containing 50% class F fly ash, very low. Assuming a continued linear trend for both at 1 year, the 20% fly ash mixture would achieve 78 kohm*cm and the 50% fly ash mixture over 300 kohm*cm, putting both mixtures well into the very low category. FIGURE 5. Surface Resistivity Results for Structural Mixtures The surface resistivity results for the repair mixtures is shown in Figure 6. The mixture containing calcium nitrate accelerator followed an expected trend of increased resistivity with time

11 TRB2016- Paper Kevern, Halmen, Hudson, and Trautman 11 corresponding well with strength gain. The literature is generally lacking discussion of the resistivity of CSA systems. The primary structure for strength development is ettringite formation which is complete at around 10 hours, afterwards monosulfate is formed (35). Since the repair mixture used in this study also contained Portland cement, the microstructure also contains conventional hydration products. The SR results with time for the repair mixture were unexpected and contrary to the conventional trend. SR first peaked at 33 kohm*cm at 12 hours and fell to around 17 kohm*cm through 28 days. However, between 28 and 56 days and continued through 90 days the resistivity increased substantially. If the literature supports that a majority of CSA hydration occurs in the first 24 hours (35, 36), the resulting gain in resistivity cannot be explained solely from the continued hydration of the Portland cement phase. Since SR and RCP are used to estimate penetrability for corrosion protection and since CSA mixtures are not typically used in applications requiring reinforcing steel, this trend may not be immediately of concern. However, before CSA repair mixtures become prevalent in application such as continuously reinforced concrete pavements (CRCP), additional research will be required to determine if SR and RCP of CSA mixtures correlates to actual corrosion rates. FIGURE 6. Surface Resistivity Results for Repair Mixtures Figure 7 shows the MoDOT surface resistivity data plotted for all mixtures and ages. The relationship between RCP and SR previously published by the Louisiana Transportation Research Center (LTRC) is plotted along with the best fit relationship for the current data. This research verifies the relationship presented by LTRC and is consistent with the AASHTO penetrability class relationship.

12 TRB2016- Paper Kevern, Halmen, Hudson, and Trautman 12 FIGURE 7. Rapid Chloride Penetrability versus Surface Resistivity Results Plotted Alongside LTRC and AASHTO Reference Data CONCLUSIONS Surface resistivity (SR) has shown promise for replacing rapid chloride penetrability testing (RCP) for evaluation of concrete. This research program evaluated a series of current and potential Missouri Department of Transportation (MoDOT) mixtures to verify published relationships and to determine additional needed variability to implement as a quality control/assurance method. From this study, the following conclusions have been drawn: A good correlation was observed and verified with previous research studies in terms of SR to RCP test results. Surface resistivity testing is faster and lower cost than RCP to perform. The cost estimate for this project is shown in Table 4 and was based off of values provided by Rupnow and Icenogle (4). TABLE 4. Cost Estimate of SR and RCP for This Study Test Method Number of Lots Number of Testing Hours Required Hourly Wage/Cost per Test ($) Tech. Cost/Test Cost ($) Total Cost ($) Cost Per Sample ($) RCP 147 1,176 $ $73,500 $73,500 $ SR $23.38 $5,046 $7,846 $11.99

13 TRB2016- Paper Kevern, Halmen, Hudson, and Trautman 13 Precision and bias analysis determined that the sample must be tested within five minutes of taking the concrete specimen from the curing environment. Most of the mixtures, including all of the bridge deck mixtures, had high penetrability at 28 days and only moderate penetrability at 90 days according to the SR and RCP results. MoDOT mixtures had relatively poor performance in terms of average surface resistivity values (and penetrability classification) when compared to other studies. The ternary mixture out-performed a majority of the MoDOT specified mixtures. The Class F fly ash mixture produced the best results related to SR. Additionally, the two repair mixes performed better than most of the other mixtures determined using the MoDOT specification guide. SR testing presents an opportunity to improve concrete mixtures and specifications to increase durability without adding significant additional testing costs. ACKNOWLEDGMENTS The research results presented herein were developed as part of a MoDOT project TR The views and findings expressed in this document are those of the authors and may or may not reflect those of the sponsoring agency. The authors would like to thank Jonathan Varner and Jennifer Harper at MoDOT for their help with sample preparation and testing and project coordination. The assistance from Pat O Bannon, the engineering research technician, at UMKC is also much appreciated. Materials used in this study were donated by various entities and the authors would like to thank Ashgrove Cement Company, Hunt Martin Materials, BASF, and Western Materials for material contributions and technical assistance. REFERENCES (1) Chini, A., Muszynski, L., and Hicks, J. (2003) Determination of Acceptance Permeability Characteristics for Performance-Related Specifications for Portland Cement Concrete, Florida DOT Final Report, July (2) Liu, Y., Suares, A., and Presuel-Moreno, F. (2010) Characterization of New and Old Concrete Structures Using Surface Resistivity Measurements, Florida Department of Transportation Research Center Final Report FAU-OE-CMM-08-3, Tallahassee, FL, 279 pgs. (3) Florida Department of Transportation (2004) Florida Method of Test for Concrete Resistivity as an Electrical Indicator of its Permeability, FM (4) Rupnow, T. and Icenogle, P. (2011) Surface Resistivity Measurements Evaluated as Alternative to the Rapid Chloride Permeability Test for Quality Assurance and Acceptance. Final Report, Report No. FHWA/LA.11/479, July, (5) Rupnow, T. and Icenogle, P. (2012) Evaluation of Surface Resistivity Measurements as an Alternative to the Rapid Chloride Permeability Test for Quality Assurance and Acceptance. Transportation Research Record: Journal of the Transportation Research Board, Vol. 2290/2012 Concrete Materials, 8 pgs. (6) Rupnow, T. and Icenogle, P. (2013) Investigation of Factors Affecting PCC Surface Resistivity through Ruggedness Testing, ASTM Journal of Testing and Evaluation, Vol. 42, No. 2, 8 pgs. (7) Icenogle, P. and Rupnow, T. (2012) Development of Precision Statement for Concrete Surface Resistivity, Transportation Research Record: Journal of the Transportation Research Board, Vol. 2290/2012 Concrete Materials, 6 pgs.

14 TRB2016- Paper Kevern, Halmen, Hudson, and Trautman 14 (8) LA DOTD TR 233: Test Method for Surface Resistivity Indication of Concrete s Ability to Resist Chloride Ion Penetration. Louisiana Department of Transportation and Development, Baton Rouge, LA, (9) Kevern, J.T., Halmen, C., and Hudson, D. Evaluation of Resistivity Meters for Concrete Quality Assurance, Final Report for Missouri Department of Transportation, Project TR201414, Report cmr , July 2015, 181 pgs. (10) Spragg, R. P., Castro, J., Nantung, T., Paredes, M., and Weiss, J. (2012) Variability Analysis of the Bulk Resistivity Measured Using Concrete Cylinders, Advances in Civil Engineering Materials, Vol. 1, Issue 1, pp (11) Morris, W., Moreno, E. I., and Sagues, A. A. (1996) Practical Evaluation of Resistivity of Concrete in Test Cylinders Using a Wenner Array Probe, Cement and Concrete Research, Vol. 26, No. 12, 1996, pp (12) Sengul, O. and Gjorv, O. (2008) Electrical Resistivity Measurements for Quality Control during Concrete Construction. ACI Materials Journal, 105(6), (13) Kessler, R., Powers, R., Vivas, E., Paredes, M. and Virmani, Y. (2008) Surface Resistivity as an Indicator of Concrete Chloride Penetration Resistance, Concrete Bridge Conference, St. Louis, MO, May 4-7. (14) Gowers, K. and Millard, S. (1991) The Effect of Steel Reinforcement bars on the Measurement of Concrete Resistivity, British Journal of NDT, Vol. 32, p (15) Paredes, M., Jackson, N., El Safty, A., Dryden, J., Joson, J., Lerma, H., and Hersey, J. (2012) Precision Statements for the Surface Resistivity of Water Cured Concrete Cylinders in the Laboratory, Advances in Civil Engineering Materials, Vol. 1, Issue 1., pp (16) MoDOT Section 501. (2014) Concrete, Missouri Department of Transportation Specifications and Engineering Policy Guide. (17) ASTM C618-05, Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete, Annual Book of ASTM Standards, Vol , ASTM International, West Conshohocken, PA, (18) ASTM C989-06, Standard Specification for Ground Granulated Blast-Furnace Slag for Use in Concrete, Annual Book of ASTM Standards, Vol , ASTM International, West Conshohocken, PA, (19) ASTM C150-07, Standard Specification for Portland Cement, Annual Book of ASTM Standards, Vol , ASTM International, West Conshohocken, PA, (20) ASTM C127-07, Standard Test Method for Density, Relative Density (Specific Gravity), and Absorption of Coarse Aggregate, Annual Book of ASTM Standards, Vol , ASTM International, West Conshohocken, PA, (21) ASTM C128-07a, Standard Test Method for Density, Relative Density (Specific Gravity), and Absorption of Fine Aggregate, Annual Book of ASTM Standards, Vol , ASTM International, West Conshohocken, PA, (22) ASTM C , Standard Specification for Lightweight Aggregate for Internal Curing of Concrete, Annual Book of ASTM Standards, Vol , ASTM International, West Conshohocken, PA, (23) Bentz, D., Lura, P., and Roberts, J. (2005) Mixture Proportioning for Internal Curing, Concrete International, 27 (2), (24) ASTM C260/C260M-10a, Standard Specification for Air-Entraining Admixtures for Concrete, Vol , ASTM International, West Conshohocken, PA, 2010.

15 TRB2016- Paper Kevern, Halmen, Hudson, and Trautman 15 (25) ASTM C494/C494M-11, Standard Specification for Chemical Admixtures for Concrete, Annual Book of ASTM Standards, Vol , ASTM International, West Conshohocken, PA, (26) AASHTO TP95-11, Standard Method of Test for Surface Resistivity Indication of Concrete s Ability to Resist Chloride Ion Penetration, AASHTO Provisional Standards, 2011 ed., American Association of State Highway and Transportation Officials, Washington, D.C., (27) ASTM C , Standard Test Method for Electrical Indication of Concrete's Ability to Resist Chloride Ion Penetration, Annual Book of ASTM Standards, Vol , ASTM International, West Conshohocken, PA, 2013 (28) AASHTO T277: Standard Method of Test for Electrical Indication of Concrete s Ability to Resist Chloride Ion Penetration (29) ASTM C39/C39M-05 ε1, Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens, Annual Book of ASTM Standards, Vol , ASTM International, West Conshohocken, PA, (30) ASTM C1231 (31) Bentz, D.P., and Weiss, W.J., Internal Curing: A 2010 State-of-the-Art Review, NISTIR 7765, U.S. Department of Commerce, February (32) Jensen, O.M. and Hansen, P.F., Water-entrained cement-based materials I. Principles and theoretical background, Cement Concrete Research, 31 (4) (2001) (33) Henkensiefken, R, Bentz, D. P., Nantung, T. E., and Weiss, W. J., "Volume Change and Cracking in Internally Cured Mixtures with Saturated Lightweight Aggregate Under Sealed and Drying Conditions", Cement and Concrete Composites, 31(7) (2009) (34) Cao, Q. and Kevern, J.T. Using Drinking Water Treatment Waste as a Low Cost Internal Curing Agent for Concrete, ACI Materials Journal, V. 112, No. 1, Jan-Feb 2015, pp (35) Winnefeld, F. and Lothenbach, B. (2010) Hydration of Calcium Sulfoaluminate Cements- Experimental Findings and Thermodynamic Modelling, Cement and Concrete Research, Vol. 40, pp (36) Liao, Y., Wei, X., and Li, G. (2011) Early Hydration of Calcium Sulfoaluminate Cement Through Electrical Resistivity Measurement and Microstructure Investigations, Construction and Building Materials, Vol. 25, pp