某试验室欲配制强度等级为C40的混凝土，采用实测强度为57.5MPa的普通硅酸水泥；细度模数为2.7的河砂；碎石最大粒径为20mm且连续级配；坍落度为70～90mm。
请根据上述条件，回答下列问题。
若按该配合比拌制混凝土，检查试件强度数理统计分析：强度平均值为46.0MPa，标准差为3.0MPa。请问该混凝土的强度保证率是多少该混凝土是否满足标准要求如果不满足应怎样调整
参考答案：按正态分布计算：t=(46-40)/3=2。
查表7-3得保证率P=97.7%。
因为大体积混凝土要求的强度保证率是P=95%。而P=97.6＞95.0，因此该批混凝土满足规范要求。如果不满足则应该提高其配制强度。
表7-3 保证率和概率度系数的关系
填空题
| 用所给短语的适当形式填空。 | | chat with stay up be interested in pay attention to give up |
1. You'd better _______ your pronunciation and do more practice.
2. He's _______ smoking, for it's not good for health.
3. David _______ till 12:00 p.m. last night, because he had too much homework to do.
4. My father used to collect coins, but now he _______ collecting stamps.
5. Mary often _______ her friends on the phone for a long time. |
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