Common use of PWL Determination for Air Voids Clause in Contracts

PWL Determination for Air Voids. 1. Air Voids of four random samples taken from Lot A. A-1 5.00 A-2 3.74 A-3 2.30 A-4 3.25 2. Calculate the average air voids for the lot. X = (x1 + x2 + x3 . . n) / n X = (5.00 + 3.74 + 2.30 + 3.25) / 4 X = 3.57 percent 3. Calculate the standard deviation Sn for the lot. Sn = [((3.57 - 5.00)2 + (3.57 - 3.74)2 + (3.57 - 2.30)2 + (3.57 -3.25)2) / (4 - 1)]1/2 Sn = [(2.04 + 0.03 + 1.62 + 0.10 ) / 3]1/2 Sn = 1.12 4. Calculate the Lower Quality Index QL for the lot. (L = 2.0) QL = (X - L) Sn QL = (3.57 - 2.00) / 1.12 QL = 1.3992 5. Determine PL by entering Table 1 with QL = 1.40 and n = 4. PL = 97 6. Calculate the Upper Quality Index QU for the lot. (U= 5.0) QU = (U - X) / Sn QU = (5.00 - 3.57) / 1.12 QU = 1.2702 7. Determine PU by entering Table 1 with QU = 1.27 and n = 4. PU = 93 8. Calculate Air Voids PWL PWL = (PL + PU) – 100 PWL = (97 + 93) - 100 = 90 TABLE 1. TABLE FOR ESTIMATING PERCENT OF LOT WITHIN LIMITS (PWL) Percent Within Limits (PL and PU) Positive Values of Q (QL and QU) n=3 n=4 n=5 n=6 n=7 n=8 99 1.1541 1.4700 1.6714 1.8008 1.8888 1.9520

PWL Determination for Air Voids. 1. Air Voids of four random samples taken from Lot A. A-1 5.00 A-2 3.74 A-3 2.30 A-4 3.25 2. Calculate the average air voids for the lot. X = (x1 + x2 + x3 . . n) / n X = (5.00 + 3.74 + 2.30 + 3.25) / 4 X = 3.57 percent 3. Calculate the standard deviation Sn for the lot. Sn = [((3.57 - 5.00)2 + (3.57 - 3.74)2 + (3.57 - 2.30)2 + (3.57 -3.25)2) / (4 - 1)]1/2 Sn = [(2.04 + 0.03 + 1.62 + 0.10 ) / 3]1/2 Sn = 1.12 4. Calculate the Lower Quality Index QL for the lot. (L = 2.0) QL = (X - L) Sn QL = (3.57 - 2.00) / 1.12 QL = 1.3992 5. Determine PL by entering Table 1 with QL = 1.40 and n = 4. PL = 97 6. Calculate the Upper Quality Index QU for the lot. (U= 5.0) QU = (U - X) / Sn QU = (5.00 - 3.57) / 1.12 QU = 1.2702 7. Determine PU by entering Table 1 with QU = 1.27 and n = 4. PU = 93 8. Calculate Air Voids PWL PWL = (PL + PU) – 100 PWL = (97 + 93) - 100 = 90 TABLE 1. TABLE FOR ESTIMATING PERCENT OF LOT WITHIN LIMITS (PWL) Percent Within Limits (PL and PU) Positive Values of Q (QL and QU) n=3 n=4 n=5 n=6 n=7 n=8 99 1.1541 1.4700 1.6714 1.8008 1.8888 1.9520