AWWA D115-17 pdf download.Tendon-Prestressed Concrete Water Tanks
2.1.1 General. Te quality of concrete is of great importance to a ten- don tank’s structural integrity and watertightness. Terefore, care shall be taken throughout the construction to maintain close quality control of the materials, proportions, forming, embedded items, placement, fnishing, curing, and other details of the work. In the context of watertightness, the aggregates used in con- crete are impermeable and the permeability coefcient of cement paste having a low water–cement ratio is about 10 –14 m/sec. Tis renders uncracked, properly placed concrete essentially impermeable.
2.1.2 Concrete and shotcrete materials. Concrete and shotcrete materials shall conform to the recommendations of ACI 350.5, ACI 350, and ACI 506.2, except as modifed herein. Te mix proportions shall be submitted to the pur- chaser and shall meet the strength and other requirements of the specifcations. Prestressed concrete, including aggregates and admixtures, and cement grout in contact with bonded tendons shall not contain water-soluble chloride ions in excess of 0.06 percent of the weight of the cement in the mix. Concrete or shotcrete sub- ject to freezing shall be air-entrained.
2.1.2.1 Concrete. Concrete shall be proportioned for a maximum water– cementitious materials ratio of 0.42 and other properties in accordance with ACI 350. Fly ash or other pozzolans that do not decrease durability are recommended for decreased permeability but are not required as a part of this standard. When pozzolans are part of the mixture, the water–cementitious materials ratio shall be 0.42 or less based on the cement plus pozzolans.
2.1.2.2 Shotcrete. Shotcrete in domes shall not contain more than four parts sand to one part cement plus pozzolans by weight. Either the wet-mix or dry- mix process referred to in ACI 506R may be used for shotcrete domes unless the specifcations require the use of a specifc process, except that dry-mix shotcrete shall not be used in domes subject to freezing and thawing cycles. Wet-mix shot- crete for domes in areas subjected to freezing and thawing shall be air-entrained with an in-place air content of 5 to 7 percent. Shotcrete shall be proportioned for a 28-day strength not less than 4,500 psi (31 MPa).AWWA D115-17 pdf download.