在混凝土拌合料中,砂子的粗细程度及颗粒级配的好坏,对混凝土的技术性能及工程造价都有很大影响。砂子的粗细程度工程中常用细度模数F.M来表示。通常有粗砂(F.M=3.7～3.1);中砂(F.M=3.0～2.3):细砂(F.M=2.2～1.67);特细砂(F.M=1.5～0.7)之分。在相同情况下,若砂子过粗则拌出来的混凝土粘聚性差,易产生离析,有泌水现象;若砂子过细,砂子的比表面积增大,则拌出来的混凝土粘聚性增大,虽不易离析、泌 In the concrete mix, the thickness of sand and particle size distribution of good or bad, the technical performance of concrete and engineering costs have a great impact. The degree of sand thickness engineering commonly used fineness modulus F. M to represent. Usually there is coarse sand (F.M = 3.7 ~ 3.1); medium sand (F.M = 3.0 ~ 2.3): fine sand (F.M = 2.2 ~ 1.67); Under the same circumstances, if the sand is too coarse, the concrete mixed out is poor, easy to produce segregation, there is bleeding phenomenon; if the sand is too small, the specific surface area of ​​the sand increases, then mix out concrete increased cohesion, though Not easy to segregation, secretion