混凝土强度保证率计算方法

混凝土强度保证率P（%）计算方法1、同标号（强度等级）试块组数n≥30时，混凝土试件强度应分别计算混凝土强度保证率和离差系数。离差系数计算方法：Cv=Sn/Rn当混凝土抗压强度＜20MPa时Cv＜0.18为优良；Cv＜0.22为合格。当混凝土抗压强度≥20MPa时Cv＜0.14为优良；Cv＜0.18为合格。混凝土强度保证率P（%）可按表1混凝土强度保证率t—P对照表直接查得，t=(Rn-R标)/Sn。表1混凝土强度保证率t～P对照表tP（%）tP（%）tP（%）tP（%）0.0050.001.0084.132.0097.723.0099.870.0551.991.0585.312.0597.983.0599.890.1053.981.1086.432.1098.213.1099.900.1555.961.1587.492.1598.423.1599.920.2057.931.2088.492.2098.613.2099.930.2559.871.2589.442.2598.783.2599.940.3061.791.3090.322.3098.933.3099.950.3563.681.3591.152.3599.063.3599.960.4065.541.4091.922.4099.183.4099.970.4567.361.4592.652.4599.293.4599.970.5069.151.5093.322.5099.383.5099.980.5570.881.5593.942.5599.463.5599.980.6072.571.6094.522.6099.533.6099.980.6574.221.6595.052.6599.603.6599.990.7075.801.7095.542.7099.653.7099.990.7577.341.7595.992.7599.703.7599.990.8078.811.8096.412.8099.743.8099.990.8580.231.8596.782.8599.783.8599.990.9081.591.9097.132.9099.813.90100.000.9582.891.9597.442.9599.843.95100.002、同标号（强度等级）试块组数30＞n≥5时，混凝土试件强度同时应满足下列两式，该统计单位的混凝土强度应判为合格。Rn-0.7Sn＞R标（2－1）Rn-1.60Sn≥0.83R标（当R标≥20）（2－2）≥0.80R标（当R标＜20）式中，Sn—n组试件强度的标准差，按下式计算：当（R标≥20MPa）统计得到的Sn小于2.0MPa时，应取Sn=2.0MPa；当（R标＜20MPa）统计得到的Sn小于1.5MPa时，应取Sn=1.5MPa。试中：Rn—n组试件强度的平均值MPa；Ri—单组试件强度MPa；R标—设计28天龄期抗压强度值MPa；n—样本容量。3、同标号（强度等级）试块组数5＞n≥2组时，混凝土试块强度应同时满足下列两式，该统计单位的混凝土强度应判为合格。Rn≥1.15R标（3－1）Rmin≥0.95R标（3－2）试中：Rn—n组试件强度的平均值（MPa）；R标—设计28天龄期抗压强度值，（MPa）；Rmin—n组试块中抗压强度最小一组值。4、同标号（强度等级）混凝土试块28天龄期抗压强度的组数只有1组时，混凝土试块强度应满足下式要求：R≥1.15R标1)(12nRRSninin