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23 Testing of Volume Change petrographic examination of hardened concrete (ASTM C 856). These techniques would not be routinely applied to Two tests that can be used to assess volume change in EOT concrete because of the rigor and expense of the test- hardened concrete are the determination of the CTE ing, but they should be considered when a better understand- (AASHTO TP 60-00) and the restrained drying shrinkage ing of EOT concrete performance is desired, especially when test ring (AASHTO PP 34-99). Neither test is adaptable to unexpected deterioration has occurred. It has been found that field applications, and thus they are of little value for moni- an adequate air-void system can be difficult to achieve in EOT toring construction. However, they may be useful for mate- concrete, even when the air content of the fresh concrete was rial selection and establishing mixture design parameters. satisfactory. Thus, if durability problems have been observed For example, measuring the CTE of the EOT concrete mix- in EOT concrete repairs, an agency should consider measur- ture will help assess the mixture's thermal compatibility with ing the air-void system parameters of the concrete. The only the existing pavement concrete. accepted method to determine the characteristics of the air- In the laboratory phase of this recent study, it was observed void system is ASTM C 457, which requires manual obser- that the CTE results were in general highly repeatable, but vation with a stereo optical microscope. Automated methods the results from the restrained shrinkage ring test were highly based on digital image analysis currently under development variable. Also, the relevance of the results of the restrained are expected to significantly shorten the time needed to con- shrinkage concrete to the performance of EOT concrete has duct this test, thus making it more suitable for routine use. yet to be established. In some instances, full petrographic analysis in accordance with ASTM C 856 might be warranted. The unique charac- Freeze-Thaw Testing teristics of EOT concrete make it more susceptible to vari- ous kinds of material-related distress (e.g., alkali-aggregate The durability of EOT concrete in a freeze-thaw environ- reactivity and sulfate attack). When durability-related dis- ment can be assessed by testing the resistance of concrete to tress in EOT concrete repairs is observed, it would be pru- freezing and thawing (AASHTO T 161) and the exposure to dent to conduct a thorough investigation of the cause of dete- deicers (ASTM C 672). These tests are long term and can be rioration using ASTM C 856 to avoid similar distress in future used only on hardened concrete and therefore are not appli- applications. cable for construction monitoring. Further, because of the rel- atively long period of testing and the complexity of the test procedure, these tests likely will be used only when evaluat- 5.2 TESTING RECOMMENDATIONS ing EOT concrete mixtures to establish mixture design param- eters (e.g., to investigate failures and qualify new materi- There are three reasons for testing EOT concrete: to design als). Most agencies in freeze-thaw climatic zones conduct a mixture for a specific application, to monitor the mixture some version of AASHTO T 161 and possibly ASTM C 672 during construction, and to conduct generalized investiga- as part of the material approval process for paving concrete. It tions to improve specifications. The type and extent of test- is recommended that these agencies use their test procedures for evaluating the proposed EOT concrete mixture designs. ing depends on the purpose for which the testing is being done. For each purpose, the suggested testing is divided into rec- ommended and optional. Absorption/Permeability Testing Absorption/permeability can be assessed by testing the spe- 5.2.1 Mixture Testing Recommendations cific gravity, absorption, and voids (ASTM C 642) or sorp- tivity (proposed ASTM test). Both tests are conducted on Table 8 shows the recommended and optional testing for hardened concrete and are thus not suitable for use in con- the mixture design process. struction monitoring. Another commonly accepted method to measure permeability is the rapid chloride permeability test (AASHTO T 277), although this test can be difficult to 5.2.2 Construction Monitoring apply to EOT concrete containing certain admixtures. Other rapid chloride permeability tests may be appropriate, but Table 9 shows the recommended and optional testing for standards need to be established before these techniques can construction monitoring. be employed for EOT concrete. Microstructural Characterization 5.2.3 Investigations and Research The final type of testing is microstructural characterization Table 10 shows the recommended and optional testing for of the concrete, such as air-void analysis (ASTM C 457) and investigations and research.
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24 TABLE 8 Recommended and optional testing for the mixture design process Test Method Property Assessed Performance Characteristic Recommended Testing AASHTO T 119 Slump Workability AASHTO T 152 or 196 Air Content of Fresh Freeze-Thaw Durability Concrete ASTM C 1074 Maturity Strength Gain AASHTO T 22 or Compressive or Flexural Strength Criterion AASHTO T 97 Strength AASHTO TP 60-00 Coefficient of Thermal Thermal Stress Expansion ASTM C 642 Specific Gravity, Absorption Absorption, and Voids Optional Testing ASTM C 457 Air-Void System Freeze-Thaw Durability Characteristics AVA (non-standard) Air-Void System Freeze-Thaw Durability Characteristics TABLE 9 Recommended and optional testing for construction monitoring Test Method Property Assessed Performance Characteristic Recommended Testing AASHTO T 119 Slump Workability AASHTO T 152 or 196 Air Content of Fresh Freeze-Thaw Durability Concrete ASTM C 1074 Maturity Strength Gain AASHTO T 22 or Compressive or Flexural Strength Criterion AASHTO T 97 Strength Optional Testing AASHTO T 131 Time of Setting Early Set TABLE 10 Recommended and optional testing for investigations and research Test Method Property Assessed Performance Characteristic Recommended Testing AASHTO T 119 Slump Workability AASHTO T 152 or 196 Air Content of Fresh Freeze-Thaw Durability Concrete ASTM C 1074 Maturity Strength Gain AASHTO T 22 or Compressive or Flexural Strength Criterion AASHTO T 97 Strength AASHTO TP 60-00 Coefficient of Thermal Thermal Stress Expansion ASTM C 642 Specific Gravity, Absorption Absorption, and Voids ASTM C 457 Air-Void System Freeze-Thaw Durability Characteristics AVA (non-standard) Air-Void System Freeze-Thaw Durability Characteristics AASHTO T 161 Resistance to Freezing and Damage Due to Cyclic Thawing Freezing and Thawing ASTM C 672 Resistance to Deicer Scaling Resistance Scaling Optional Testing AASHTO PP 34-99 Restrained Shrinkage Resistance to Drying Shrinkage Cracking ASTM C 856 Concrete Microstructure General Appearance at Microscopic Level