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为预测混凝土强度标号,有人提出了以下经验公式: R_(28)=R_7+B/Ц(R_4-R_1)(1)式中H_(28)——标养28天混凝土强度计算值; R_1、R_4、R_7——标养1天、4天和7天的标准试件的强度。根据式(1)预测是可靠的:计算值与混凝土实际强度及与试验确定的强度精度是吻合的。但是,得到预测值需要7天时间,而这么长的时间是满足不了现代化施工要求的。要提高式(1)预测结果的可靠性,要求用混凝土7天强度的计算值代替试验确定
In order to predict the concrete strength index, the following empirical formulae have been proposed: R_(28)=R_7+B/Ц(R_4-R_1)(1) where H_(28)—the calculated value of the concrete strength for the 28-day standard; R_1, R_4, R_7 - Strength of standard test specimens for 1 day, 4 days and 7 days. The prediction based on equation (1) is reliable: the calculated value is consistent with the actual strength of the concrete and the strength accuracy determined by the test. However, it takes 7 days to obtain the forecast value, and such a long time cannot meet the requirements of modern construction. To improve the reliability of the prediction result of formula (1), it is required to use the calculated value of the concrete strength for 7 days instead of the experimental determination.