Step 1: Select slump and required concrete strength—Recommended values for concrete slump are given in Table 6.1. Although high-strength concrete with HRWRA has been produced successfully without a measurable initial slump, an initial starting slump of 1 to 2 in. before adding HRWRA is recommended. This will ensure an adequate amount of water is available for mixing and hydration and allows the HRWRA to be effective. Slump values after addi- tion of HRWRA of at least 2 in. are recommended because concrete with a slump less than 2 in. is difficult to consolidate. For high-strength concrete made without HRWRA, a recommended slump range of 2 to 4 in. may be chosen according to the type of work to be done. A minimum value of 2 in. of slump is recommended for concrete without HRWRA. HRWRA dosage should be adequate for both the anticipated contribution to strength and the desired workability. Slump after adding HRWRA should be enough for proper placement and consolidation, but not so much as to cause segregation.
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