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96 Introduction In Step 1, the performance requirements are selected, and a battery of tests to evaluate that performance is identified. In Step 2, locally available raw materials that are expected to pro- duce durable concretes are selected, and in Step 3 specific combinations of those materials are selected to form a statis- tically based experimental design. The objective of Step 4 is the generation of performance data for the selected combinations of materials as laid out in the experimental design matrix. Thus, in Step 4, the actual concrete is made and evaluated. Test Program Considerations The quality of the predictions made by the methodology is related to the quality of the data collected. Therefore, the tests must be conducted so that they are consistent from mixture to mixture and in such a way that the test conditions permit prediction of actual in-place exposure performance as closely as possible. Also, the laboratory personnel conducting the testing are expected to be familiar with the test methods and to follow these methods closely. Although users of this methodology are expected to be experienced in trial batching concrete mixtures, the follow- ing suggestions are presented for emphasis: ⢠Keep constant all properties that are not tested directly. Certain properties of the concrete influence other perform- ance. While those properties may be included in the analy- sis, if feasible, they should be held as constant as possible. For example, the air content of the concrete has a significant influence on the strength, elastic modulus, and freezing and thawing resistance, and the slump may have an effect on the permeability. Both of these properties likely affect the fin- ishability and can be controlled by admixture dosage. A tar- get value with a tight range of acceptability on these values should be selected during trial batching to allow direct com- parisons of performance or durability properties. ⢠Use trial batches to determine admixture contents. Trial batches can be used to determine the admixture dosages required to keep non-investigated properties of the con- crete that may influence performance in other tests within a small range. Because the response of concretes contain- ing SCMs to chemical admixtures varies, multiple trial batches will be required to achieve the desired range of fresh properties of each of the concrete mixtures. ⢠Ensure consistency of materials. Consistency of cementi- tious materials may vary over the length of time required to batch the various mixtures and perform this test program. Therefore, sufficient materials to complete the work should be collected at the beginning of the test program. Also, be- cause the water content of the concrete can have a profound effect on the concrete performance, the moisture content of the aggregates should be determined throughout the test program and compensated for during batching. In addition, consistency should be maintained in terms of test personnel if possible, particularly for those methods where some sub- jective evaluation is necessary (i.e., scaling testing) or where slight changes in the method may influence the results. ⢠Follow a consistent mixing process that simulates actual batching procedures. ASTM C 192, Standard Practice for Making and Curing Concrete Tests Specimens in the Lab- oratory, provides a basis for producing the specimens for testing. The order of admixture addition should be the same as anticipated for actual production. The objective of the test program must be considered. For example, for test- ing heat of hydration, preconditioning of materials at similar temperatures is essential to obtain meaningful data. Example from Hypothetical Case Study The test program outlined in Step 1 (listed in the com- pleted Worksheet S1.1 [Table S1.8]) was conducted on the mixtures selected in Step 3 and listed in Table S3.8 for the hypothetical case study. S T E P 4 Perform Testing
