ACI 332-14 Residential Code Requirements for Structural Concrete (ACI 332-14) and Commentary. R5.2—Exposure categories and classes R5.2.1 For Exposure Category RF, Exposure Class RF0 should be assigned to interiors and to footings, foundations, and basement walls submerged in the ground. Concrete deteriorates when exposed to freezing-and-thawing cycles when any portion of the member is in a critically saturated condition during freezing weather. Basement and foundation walls that extend above grade less than 12 in. are unlikely to be saturated and could generally be assigned Exposure Class RF0. Exposure Class RF1 or RF2 should be assigned to vertical concrete members where excessive accumula- tion of ice and snow is not anticipated. Examples include above-grade footings, walls, and columns. Exposure Class RF2 should be assigned to elevated or on-grade horizontal concrete members that have a likelihood for prolonged contact with water to achieve a saturation state. Examples include concrete roofs, patios, or other slabs where it is anticipated that deicing chemicals will not be used. Expo- sure Class RF3 should be assigned to the same type of members as in Exposure Class RF2 but where the applica- tion of deicing chemicals is anticipated. Examples include driveways, curbs, steps, stairs, and porches. Exposure Category RS should be based on a measure- ment or knowledge of the concentration of soluble sulfates in soil or water that will be in contact with the relevant concrete member. The referenced standards should be used to measure the sulfate concentrations. Other methods can provide different results compared with the methods refer- enced. Where the predominant soil sulfates are in the form of gypsum, the measured sulfate content will be higher and these criteria will be conservative. In these cases, it is pref- erable that a test that has a history of successful use in the geographic area of the project be permitted and approved by the local building offcial. Even though concentration of soluble sulfates in seawater will be high, members exposed to seawater should be assigned to Exposure Class RS1. R6.2—Placement R6.2.1 Normally, concrete discharge is completed within 90 minutes after the introduction of water to cement. Expe- rience has shown that the 90-minute discharge time can be exceeded while maintaining the specifed concrete proper- ties during placing operations. ASTM C94/C94M allows for the one-time addition of water at the job site up to the allowable maximum w/cm. Alternatively, the addition of a high-range water-reducing admixture (HRWRA)...
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