ACI 332.1R-18 Guide to Residential Concrete Construction

ACI 332.1R-18 Guide to Residential Concrete Construction. 3.2.7.10 Shrinkage reducing admixtures―Although not often used in residential construction, shrinkage-reducing admixtures (SRAs) can be used to reduce drying shrinkage that mainly results from surface tension developed in the small pores of the cement paste of concrete. The SRA reduces shrinkage by reducing the surface tension of water in the pores. Normal dosage rates range from 0.5 to 1.5 gal./ yd 3 (2.5 to 7.4 L/m 3 ). The applicable standard for SRAs is ASTM C494/C494M Type S. For more information, refer to ACI 360R. 3.2.8 Fibers 3.2.8.1 Synthetic fbers—Synthetic fbers are man-made fbers manufactured by the petrochemical and textile indus- tries. The largest use of synthetic fbers (acrylic, aramid, carbon, nylon, polyester, polyethylene, and polypropylene) is in slab-on-ground construction. Table 3.2.8.1 provides a description of fber properties and use. Further informa- tion on synthetic fbers can be found in ACI 544.1R, ASTM C1116/C1116M, NRMCA CIP 24, and PCA EB001. 3.2.8.2 Steel fbers—Steel fbers are seeing increased usage in slabs-on-ground. Table 3.2.8.1 provides a descrip- tion of fber properties and use. Further discussion of the benefts of steel fbers can be found in ACI 544.1R. The applicable standard and classifcation for steel fbers is found in ASTM A820/A820M. 3.2.9 Mineral pigments—Mineral pigments meeting ASTM C979/C979M requirements can be added to color the concrete. 3.3.1.1 Slump—One measure of concrete consistency or workability (fowability) is called slump. A slump test (ASTM C143/C143M) measures the consistency of the concrete for slumps up to 9 in. (200 mm), and a modifed slump-fow test (ASTM C1611/C1611M) for self-consol- idating concrete (SCC) measures a mixture with greater fuidity. The slump test is performed by flling a truncated cone (Fig. 3.3.1.1a) with concrete and measuring how much the concrete subsides, or slumps, when the cone is lifted. Residential concrete is generally placed with a slump of 4 to 6 in. (100 to 150 mm). A higher slump of 6 to 9 in. (150 to 200 mm) (Fig. 3.3.1.1b) indicates that the concrete is more workable than a lower slump of 1 to 3 in. (25 to 75 mm) (Fig. 3.3.1.1c). Lower-slump concrete is stifer and more dif- cult to place into formwork, consolidate, and fnish. High slumps, if achieved by only adding water, will result in lower compressive strengths, greater shrinkage characteristics, and freezing-and-thawing resistance problems if the total amount of water added exceeds the maximum w/cm designed for the...