QUALITY CONTROL OF

CONSTRUCTION MATERIALS(Acceptance criteria)

by

K. RAMESH

Research Officer,Engineering Materials Laboratory,

A.P. Engineering Research Laboratories,Himayatsagar, HYDERABAD-500030.

Acceptance criteria for designed concrete mix

Minimum frequency of sampling

S.No. Quantity of concrete in the work (in Cum.)

No. of samples

1. 1-5 1

2. 6-15 2

3. 16-30 3

4. 31-50 4

5. 51 & above 4 + 1 for each 50 cum. Or part there of

Note: At least one sample shall be taken from each shift.

Characteristic compressive strength compliance requirement

S.No. Specified grade

Mean of the group of 4 non-overlapping consecutive test results in N/mm2

Individual test results in N/mm2

1. M 15 ≥fck + 0.825 x established standard deviation (rounded to nearest 0.5 N/mm2)

Or

fck + 3 N/mm2, which ever is greater

≥ fck - 3 N/mm2

2. M 20 or above

≥fck + 0.825 x established standard deviation (rounded to nearest 0.5 N/mm2)

Or

fck + 4 N/mm2, which ever is greater

≥ fck - 4 N/mm2

Example

• Grade of concrete = M15• Quantity of concrete = 50 Cum.• No. of samples taken = 4• Their 28 days compressive strengths in N/mm2 =

12,15,16,18• Mean compressive strengths in N/mm2 = 15.25• Col. 3 value = Greater of (15 + 0.825 x 3.5 = 17.9,

15 + 3 = 18) = 18 > 15.25 , hence not satisfying.• Col.4 value = 15 – 3 = 12 is equal to 12, hence

satsifying,• In total not satisfying.