Guide for Curing Portland Cement Concrete Pavements, II
Publication No. FHWA-HRT-05-038 August 2006
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FOREWORD
There has been a considerable amount of research over approximately the last 70 years on the theoretical aspects of curing portland cement concrete. Early work focused principally on portland cement hydration chemistry and the physics of developing microstructure. Later work incorporated features of pozzolanic reactions and other supplemental cementing materials. Because of this work, there is sufficient understanding of the theoretical aspects of the curing process for concretes of conventional proportions using conventional materials to develop effective practical application rules. The causes of when and where problems exist while curing portland cement concrete pavement may be because of changes in concrete technology that developed since the curing guidance was written or from some details of paving construction practice that differed from the types of concrete construction around which curing guidance was developed.
This report contains information on the current state of knowledge of curing hydraulic-cement concrete and on current curing practice, gathered by means of a literature review and a review of current standard guidance. A separate report (FHWA RD-02-099 Guide for Curing of Portland Cement Concrete Pavements, Volume. I) was published in January 2005 and captures the details of the recommended guidance.
Gary L. Henderson
Director, Office of Infrastructure
Research and Development
Notice
This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document. This report does not constitute a standard, specification, or regulation.
The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers' names appear in this report only because they are considered essential to the objective of the document.
Quality Assurance Statement
The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.
Technical Report Documentation Page
1. Report No.
FHWA-HRT-05-038 |
2. Government Accession No. |
3. Recipient's Catalog No. |
4. Title and Subtitle
Curing Portland Cement Concrete Pavements, Volume II |
5. Report Date
August 2006 |
6. Performing Organization Code:
CEERD-SC-A |
7. Author(s)
Toy S. Poole |
8. Performing Organization Report No.
ERDC-CMB 05-021 |
9. Performing Organization Name and Address
Structures Laboratory
USAE Research and Development Center (ERDC)
3909 Halls Ferry Road
Vicksburg, MS 39180-6199
|
10. Work Unit No. |
11. Contractor Grant No.
DTFH61-98-Y-50030 |
12. Sponsoring Agency Name and Address
Federal Highway Administration
6300 Georgetown Pike
McLean, VA 22101-2296 |
13. Type of Report and Period Covered |
14. Sponsoring Agency Code |
15. Supplementary Notes
Stephen Forster and Peter Kopac, Contracting Officer's Technical Representatives (COTR), HRDI-11 |
16. Abstract
Information on the current state of knowledge of curing hydraulic-cement concrete and on current curing practice was gathered by means of a literature review and a review of current standard guidance. From this information, a draft guide for curing hydraulic-cement concrete pavements was developed. Draft guidance was based around type of curing used (water added, water retention by sheet, or curing compound) and around temperature effects. As a result of review by the project technical advisory panel, additional information was gathered from existing sources on several subjects. Laboratory studies were conducted on topics for which information was needed but not currently available. The result of the investigation was a set of guidelines that focused particularly on attention to details of moisture retention and temperature immediately after placing (initial curing period) and on details of selection of materials for final curing and determining when to apply final curing. Test methods for evaluating application rate of curing compound and effectiveness of curing were also reported. A separate report (FHWA RD-02-099 Guide for Curing of Portland Cement Concrete Pavements, Volume I) has been written that captures the details of the recommended guidance. That report is intended to be the principal technology transfer medium. |
17. Key Words
Curing, Portland cement concrete paving, curing compound, evaporation reducers, initial set, final set, plastic shrinkage |
18. Distribution Statement
No restrictions. This document is available to the public through the National Technical Information Service, Springfield, Virginia 22161. |
19. Security Classif. (of this report)
Unclassified |
20. Security Classif. (of this Page)
Unclassified |
21. No of Pages
170 |
22. Price |
Form DOT F 1700.7 (8-72) Reproduction of completed page authorized
SI (Modern Metric) Conversion Factors
TABLE OF CONTENTS
LIST OF FIGURES
Figure 1. Canopy used to protect fresh concrete.
Figure 2. General layout of the draft guide.
Figure 3. Selection among moist-curing methods.
Figure 4. Decision criteria for curing-compound methods.
Figure 5. Decision criteria for water-added methods.
Figure 6. Decision criteria for water-retentive methods other than those using curing compounds.
Figure 7. Decision criteria for duration of curing.
Figure 8. Decision criteria for temperature management in hot weather.
Figure 9. Decision criteria for temperature management in cold weather.
Figure 10. Calculated versus measured evaporation rates. Wind directly on the free-water surface.
Figure 11. Comparison of total water lost, expected from the ACI 308 nomograph and bleed rate of a 0.45 water-cement concrete.
Figure 12. Evaporation of water from a 0.37 water-cement specimen compared with the rate expected from the ACI 308 nomograph. Surface temperature changes approximately track evaporation rates.
Figure 13. Bleeding pattern of a 0.45 water-cement ratio concrete.
Figure 14. Bleeding rate per unit thickness of concrete (cm) versus water-cement ratio.
Figure 15. Development of spall as a result of early application of curing compound.
Figure 16. Cracked curing membrane resulting from application before cessation of bleeding.
Figure 17. Rebound number of concrete surface versus water loss in final curing period (7 days).
Figure 18. Surface water absorption versus water loss during the final curing period (7 days).
Figure 19. Water loss at 72 h versus application rate of curing compound. The more conventional representation of application rate (m2/L) is annotated by each point.
Figure 20. Surface water absorption versus application rate of curing compound.
Figure 21. Rebound number versus application rate of curing compound.
Figure 22. Comparison of calculated versus measured drying times for six curing compounds under a range of drying conditions.
Figure 23. Effect of curing compound application on concrete surface temperature.
Figure 24. Fresh mortar specimens with variable applications of white pigmented curing compound. The top four specimens contained 15.2, 7.9, 5.4, 3.2 m2/L (L to R). The bottom 3 specimens were treated as unknowns (see table 12).
Figure 25. Black construction-paper specimens with variable applications of white pigmented curing compound. The top four specimens contained 10.1, 7.5, 5.9, 4.5 m2/L (L to R). The bottom 3 specimens were treated as unknowns (see table 13).
Figure 26. Reflectance versus application rate for white pigmented curing compound applied to fresh mortar at different rates. Data points represented by open symbols were treated as unknowns.
Figure 27. Reflectance versus application rate for white pigmented curing compound applied to black-paper specimens at different rates. Data points represented by open symbols were treated as unknowns.
Figure 28. Effect of curing quality on development of rebound number at early ages. Specimens cured at 38 °C.
Figure 29. Effect of curing condition on rebound number of top surface of specimens at 7 days.
Figure 30. Correlation between rebound number and surface water absorption.
Figure 31. Surface water absorption versus depth for concrete cured with different methods.
Figure 32. Relationship between shrinkage of near-surface zone of concrete and water absorption after 11 days of exposure to drying conditions.
Figure 33. Relationship between maximum temperature gradient between concrete surface and 50 mm depth versus initial evaporation rate calculated form the ACI nomograph.
Figure 34. Temperature gradient in a 50-mm thick specimen starting at 44 °C, air temperature of 22 °C, RH of 29 percent, and windspeed of 4.6 m/s.
LIST OF TABLES
- Table 1. Time of setting data, predicted and observed conditions
- Table 2. Curing time to capillary discontinuity
- Table 3. Evaporation rates (kg/m2/h) from hardened mortar (C 109).(82)
- Table 4. Effect of evaporation reducers on evaporation of bleed water from mortar specimens
- Table 5. Curing compound information
- Table 6. Summary of Experimental Series 9 with CC 010150, polyalphamethyl styrene
- Table 7. Summary of Experimental Series 12 with CC 000182, resin
- Table 8. Summary of Experimental Series 13 with several curing compounds
- Table 9. Summary of Experimental Series 17 with no curing compound
- Table 10. Summary of Experimental Series 23 with CC 000182, resin. These specimens were cast onto a bed of sand to simulate effects of bleed water draining off
- Table 11. Summary of Experimental Series 24 with CC 010150, resin. These specimens were cast onto a bed of sand to simulate effects of bleed water draining off
- Table 12. Comparison of actual and visually estimated curing compound application on fresh mortar specimens
- Table 13. Comparison of actual and visually estimated curing compound application on black construction paper
- Table 14. Comparison of actual and reflectance-estimated curing compound application on fresh mortar, using the power equation in figure 26
- Table 15. Comparison of actual and reflectance-estimated curing compound application on black paper, using the power equation in figure 27
- Table 16 summarizes various prescriptive curing requirements
- Table 17. Comparison of Ultrasonic Pulse Velocity (m/s) among curing conditions
- Table 18. Reproduction of table 6.8 of ACI 306R-88(13). Duration of recommended protection for percentage of standard-cured 28-day (d) strength
- Table 19. Reproduction of table 6.1 of BS 8110, Part 1(39), Section 6 on minimum periods of curing and protection
- Table 20. Reproduction of Table d.10 on minimum duration of curing in days for T>10 °C, exposure classes 2a; 2b; 4a and 5a, according to Table d.1 cement CE I
- Table 21. Minimum curing period for EN 206 exposure classes other than XO and XC1
- Table 22. Reproduction of RTA specification requirements from Ho and Chirgwin (1996)
- Table 23. Curing time to capillary discontinuity