 Classification  Features in Influencing Concrete  Fine Aggregate-Sand  Coarse Aggregate-Gravel Aggregate

Fine Aggregate-Sand Definition Definition Definition Classification Classification Classification Requirements of Aggregate Requirements of Aggregate Requirements of Aggregate Requirements of Aggregate  Impurities  Particle shape and surface texture  Particle Size Gradation  Type of Particle Size Gradation

 It refers to the aggregate whose diameter is less than 5mm.  It must be in agreement with GB/T (JGJ52-92). Definition

Sand raw material Hill sand Sea sand River sand Natural sand Artificial sand Sand is the widely used in primary fine aggregate. Sand can be divided into natural sand and artificial sand by the sand origin. In natural sand, we have river sand, sea sand and hill sand. Classification

Ⅰ : Ⅰ : In the concrete the strength grade is more than C60; Ⅱ : Ⅱ : In the concrete the strength grade is between C30~C60; Sand technical requirement Ⅰ Ⅱ Ⅲ Ⅲ : Ⅲ : In the concrete the strength grade is less than C30. Ⅰ, Ⅱ and Ⅲ By quality, there are three types: Ⅰ, Ⅱ and Ⅲ Classification

 Impurities refer to those that hinder the hydration or cause harden cement paste corrosion, reduce the bond between cement paste and aggregate. Impurities Types Impurities Organic substance Silt Clay Mica Requirements of Sand

 Hinder the bond between paste and aggregate  Weaken the strength of concrete  Increase the quantity requirement of water  Increase the shrinkage of concrete  Bring corrosion to harden cement Damage

 W hen there is too many of impurities in the sand, we can wash it out until it accords with the requirement.  T he amount of impurities must be in agreement with GB/T (JGJ52- 92) listed in Tab Processing methods

Type Index ⅠⅡⅢ Clay content % < Clod content % < Mica % < Light matter% <1.0 Organic substance (colorimetry) Eligible Sulphide and sulphate% < 0.5 Chloride% < Tab Amounts of Impurities (GB/T )

Tab Particle Shape and Surface Texture Type Particle Shape Surface Texture FeasibilityStrength River sand Round or elliptical LubricityWellLow Sea sand Mountain sand PointedRoughBadHigh Particle Shape and Surface Texture Particle shape, surface texture and their influences in properties are listed in Tab4.2.2.

 It refers to the sand distribution with different diameters. Particle Size Gradation

Screen size mm Unit screening rate （ % ） Accumulated screening rate （ % ） 5a1a1 A 1 =a a2a2 A 2 =a 1 +a a3a3 A 3 =a 1 +a 2 +a a4a4 A 4 =a 1 +a 2 +a 3 +a a5a5 A 5 =a 1 +a 2 +a 3 +a 4 +a a6a6 A 6 =a 1 +a 2 +a 3 +a 4 +a 5 +a 6 Tab4.2.3 Particle Size Gradation Particle size gradation and grading region are listed in Tab4.2.3 and Tab4.2.4

grading region Accumulated Screening Rate % Screen sizeⅠⅡⅢ 10mm000 5mm 10 ～ 0 2.5mm35~525~015~0 1.25mm65~3550~1025~0 0.63mm85~7170~4140~ mm95~8092~7085~ mm 100 ～ 90 Tab Grading Region

Three grading regions are compartmentalized by accumulative total sieve residue percent of sieve size with 0.63mm. Compared with the numbers listed in the table, the accumulative total sieve residue percent of the sand can go beyond 5% of all the sand except 5mm and Grading region

Grading curve

Grading Region Grading Curve of Sand 0 40 Ⅲ Ⅱ Ⅰ

 The curve in the right bottom region towards I is thicker while it is thinner in the left upper towards Ⅲ. Curve Analyze

 The sand of region I is mainly made up of coarse sand, not for general concrete since it is easy to bleed and hard to come into dense form. It is used to make rich concrete.  The S P of region I should be raised to meet with the demands of Feasibility while that of region II should be reduced to guarantee the strength. Region I Curve Analyze

 The sand of region Ⅱ is mainly made up of medium sand.  It is for ordinary concrete.  The sand in region Ⅱ will be taken precedence over when we produce the concrete. Region Ⅱ Curve Analyze

 The sand of region III is mainly made up of fine sand.  The concrete mixture of it takes on high viscosity and good water retentivity, but it is easy to lead to dry shrinkage. Region Ⅲ Curve Analyze

It refers to the composite fineness of the sand with different diameters. Fineness Denotation method Denotation method It can be denoted by fineness modulus. It can be denoted by fineness modulus. Fineness Modulus

Tab4.2.5 Types of Fineness Types of Fineness ff coarse sand  f =3.1~3.7 medium sand  f =2.3~3.0 fine sand  f =1.6~2.2 super fine sand  f =0.7~1.5 According to fineness modulus, we can deicide the types of fineness referring to Tab4.2.5 Fineness

 T he coarse and fine sand is in appropriate quantity.  The voidage ratio is tiny.  The total surface area is small and the quantity of cement paste is low.  The Feasibility, density, strength and durability are high. Excellent Distribution