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細度模數用為砂的粗細程度的指標,已有三十餘年的歷史;尤其是在混凝土的配合上,砂的細度模數如有變化,含砂率和加水量也要加以相應的調整,才能維持混凝土的稠度(以陷度代表)不變。但是細度模數有兩大缺點,一個是模數的物理意義不明,另一個是模數不能表示出砂的級配來。蘇聯斯克拉姆塔耶夫教授於1943年提出砂的平均粒徑(d_(cp))來,以為砂的細度指標;雖然平均粒徑仍不包含級配的意義,但是有了比較明確的物理意義,並且可以用毫米來度量,這是一種新的發展。不過砂的細度問題還不能由平均粒徑而得到解决,且平均粒徑計算式中的五項,僅首三項有效,1.2和2.5毫米以上的兩級粗砂在計算式中不生作用,以致影響了它的實用效果。本文對於平均粒徑計算式的創立方法加以追尋和推演,發現其基本假設及物理意義,又設例演算,以考察其變化的規律性;認為細度模數還有其一定的實用價值,不能為平均粒徑所代替。至於補救細度模數缺點的方法,本文試由模數本身中去尋找;將模數的計算式加以理論上的補充後,不但能分析出模數的物理意義,並且還發現模數有細度和粗度之別。根據累計篩餘計算出來的F.M.應稱為“粗度模數”,根據通過量計算出來的才是“細度模數”。假定兩隣篩间的顆粒是兩篩篩孔的幾何平均值,以代替數學平均值(即斯氏平均?
Fineness modulus is used as an index of the thickness of sand. It has been more than 30 years old; especially in the mix of concrete, if the fineness modulus of sand is changed, the sand content and the amount of water must be correspondingly Adjustments can be made to maintain the consistency of the concrete (represented by the degree of depression). However, the fineness modulus has two major drawbacks. One is that the physical meaning of the modulus is unknown, and the other is that the modulus cannot represent the gradation of sand. In 1943, Professor Skramtayev of the Soviet Union proposed the sand’s average particle size (d_(cp)) as the sand’s fineness index; although the average grain size still does not include the meaning of grading, it has relatively clear Physical meaning, and can be measured in millimeters, this is a new development. However, the fineness of sand cannot be solved by the average particle size, and only five of the five items in the average particle size calculation formula are valid, and two grades of coarse sand of 1.2 and 2.5 mm are not used in the formula. , Which affects its practical effect. In this paper, the method of establishing the average particle size calculation formula is pursued and deduced, and its basic assumptions and physical meanings are found. Case calculations are also set up to examine the regularity of the changes; the fineness modulus is also considered to have certain practical value and cannot be The average particle size is replaced. As for the method to remedy the shortcomings of fineness modulus, this paper tries to find the modulus itself; after theoretically adding the formula of modulus, it can not only analyze the physical meaning of the modulus, but also find that the modulus is small Difference between degree and roughness. The F.M. calculated based on the accumulated sieves should be referred to as the “coarse modulus” and the “fineness modulus” calculated from the throughput. Assume that the particles between two neighboring sieves are the geometric mean of the two sieve meshes instead of the mathematical average (ie, the Stirling average).