Sieve Analysis Concrete Mix Design Technician School
Terms and Definitions Aggregate. An inert filler material, such as crushed stone, gravel, and sand which is mixed with cement and water to make concrete. Coarse Aggregate. Generally aggregate larger than 1/2" in diameter, referred to as stone or gravel. Pg 173
Fine Aggregate A natural silica or manufactured aggregate smaller than 1/4" in diameter, normally referred to as sand. Sieve Analysis A process in which an aggregate is separated into its various sizes by passing it through screens of various size openings for the purpose of determining the distribution of the quantities separated. Gradation of an Aggregate The relative amounts of aggregate particles of consecutively larger and smaller sizes. Pg 174
Pg 175 Maximum Size of Aggregate The smallest sieve opening through which the entire amount of the aggregate is required to pass. Nominal Maximum Size of Aggregate The smallest sieve opening through which the entire amount of the aggregate is permitted to pass.
Standard Sieves Coarse Aggregate 6", 3", 1 1/2", 3/4", 3/8", and No.4 Fine Aggregate Nos. 4, 8, 16, 30, 50, and 100 Pg 17
Affect of Particle Size on Aggregate Surface Area. One 1- in cube of aggregate. Surface area = 6 x 1 x 1 = 6 sq in 27 1/3 - in cubes of aggregate. Surface area = 6 x 1/3 x 1/3 x 27 =18 sq in.
Sieve Analysis Procedure Take a representative sample. Reduce to proper size for testing.
Table 1005-1 North Carolina Department of Transportation Standard Specifications Coarse Aggregate Gradation Pg 24
Coarse Aggregate Gradation When tested during production the amount passing the No. 200 sieve may be no greater than 0.6% by weight. When tested at the job site prior to use , the amount of material passing the No. 200 sieve shall not be greater than 1.5% by weight. Pg 24
Coarse Aggregate Gradation If a stockpile at the job site is found to contain in excess of 1.5% passing the No.200 sieve prior to use, the engineer may approve its use provided the total % by weight passing the the no 200 sieve in the combined coarse and fine aggregate does not exceed 2%, & no increase in W/C ratio is required by the use of this aggregate.
Pg 25 Table 1005-2 Aggregate Gradation of Fine Aggregate
Fine Aggregate Gradation When tested during production the amount of material passing the No.200 sieve shall not be greater than 8%. When tested at the job site prior to use, the amount of material passing the No. 200 sieve shall not be greater than 10%. Pg 25
200 Sieve Washing Procedure Pg 26 • In a fine and coarse aggregate sieve analysis, the representative sample is washed over a No. 200 sieve. • The portion retained in the No. 200 sieve is dried and weighed. • The loss is then recorded in accordance with AASHTO T11.
No.200 Sieve Calculation Percent passing No. 200 sieve = Total dry wt – wt after washing x 100 Total dry wt Pg 27
Example 200 Sieve Problem Total dry wt 514.0 grams Wt after washing 504.9 grams Gram mat’l passing 200 9.1 grams 9.1 grams x 100 = 1.8% passing 514.0 grams Pg 28
Sieve Analysis Example Pg 29
Sieve Analysis Problem 1 Pg 33
Sieve Analysis Problem 2 Pg 34
Sieve Analysis Problem 3 Pg 35
Sieve Analysis Problem 4 Pg 36
Sieve Analysis Problem 5 Pg 37
Fineness Modulus Fine Modulus – An index to the coarseness or fineness of an aggregate. Fineness Modulus (FM) – Defined mathematically as the sum of the cumulative percentages retained on the standard sieves divided by 100. Pg 39
Fineness Modulus FM of fine aggregate should not be less than 2.30 or more than 3.10, nor vary by more than 0.20 from batch to batch. Coarse Sand 2.80 - 3.10 Medium 2.50 - 2.80 Fine Sand 2.30 - 2.50 Pg 39
The Standard Sieves 6 in 3 in 1 ½ in ¾ in 3/8 in #4 #8 #16 #30 #50 #100 Pg 39 Fine agg. range 3/8 - #100 Coarse agg. range 6 in - #8
Table 5.3.6 Pg 39 • Table 5.3.6 gives the volume of dry rodded coarse aggregate per unit volume of concrete for different fineness moduli of sand. • If the size of coarse aggregate and fineness modulus is known, the volume of dry rodded coarse aggregate can be obtained from the table.
Table 5.3.6 Pg 39 • The proportion of coarse and fine aggregate in a concrete mix depend upon the fineness modulus of the fine aggregate and the size of the coarse aggregate. • The volume of coarse aggregate increases or decreases to maintain a constant surface area or a constant water demand.
Table 5.3.6 Pg 40 • The variable is the fineness or coarseness (FM) of the sand.
TERMS I SHOULD KNOW? Fineness Modulus Nominal Maximum Size Sieve Analysis Water Reducing Agent Workability HOLD ON A MINUTE AND LET ME MARK THOSE IN THE BACK OF MY BOOK!!