Design concrete mixes of M30 to suit the following data per IS:10262-1982 :
Characteristic cube strength = M-30, type of cement - ordinary Portland, fine aggregate natural river sand conforming to grading zone II of table-4 of IS:383-1970 coarse aggregate-crushed (angular) coarse aggregate of 20 mm maximum size conforming to IS:383 code requirements, specific gravities of cement, sand and coarse aggregate are 3·14, 2·63 and 2·61 respectively. Type of exposure - mild, Degree of quality control - very good. Degree of workability = 0·08. use IS:10262-1982.
Grade = M 30
F.A. = grade zone II
C.A. = 20 mm.
Sp. Gr. Of cement = 3.14
Sp. Gr. Of sand = 2.63
Sp. Gr. Of C.A.= 2.61
Expose condition – mild;
Degree of quality control – very good;
Workability = 0.08 = 80mm;
Use code IS: 10262 – 2009 and IS: 456 – 2000;
From IS: 10262 – 2009:- f’ck = fck + 1.65 S
= 30 + 1.65 x 5 = 38.25 N/mm2
S = 5 [ from table 1 of IS: 10262 – 2009].
Selection of W/C ratio:- from table 5 of IS: 456 – 2000 maximum W/C ratio = 0.45
For trial 1 adopt W/C ratio as 0.40;
0.4 < 0.45; hence ok.
Selection of water content:- from table 2 maximum water content for 20 mm aggregate = 186 lit. [ for25 to 50 mm slump range.
Here 80 mm slump;
As per 4.2 of code the required water content may be increased by 3% for every additional 25 mm slump. = 186 + (3/100) x 186 = 192 lit.
Calculation of cement content :- W/C = 0.4
Cement content = 192 / 0.4 = 480 kg/m3.
From table 5 of IS 456, minimum cement content for mild exposure condition = 300 kg/m3.
480 kg/m3 > 300 kg/m3.
Proportion of volume of C.A. and F.A. content:- from table 3 volume of coarse aggregate corresponding to 20 mm size agg. And F.A. (zone II) for W/C ratio of 0.5 = 0.62.
In the present case W/C ratio is 0.4. as the w/c ratio is lowered by 0.1, the prop. Of volume of coarse agg. Is increased by 0.02, .i.e. ( -/+ 0.01 for every +/- 0.05 change in w/c ratio).
Proportion of C.A. for w/c ratio of 0.4 = 0.62+0.02 = 0.64
For pumpable concrete this values are reduced by 10%.
Volume of C.A. = 0.64 x 0.9 = 0.58
Volume of F.A. = 1-0.58 = 0.42
Mix calculation:-
Volume of cement = (mass of cement/sp.gr. of cement) x(1/1000)
= 0.153 m3
Volume of water = (mass of water/sp. Gr. Of water)x (1/1000)
= 0.192 m3
Mix proportion:- cement = 480 kg/m3.
water = 192 lit.
F.A= 729 kg/m3.
C.A=999.11 kg /m3.
w/c ratio = 0.4
proportion:- 1 : 0.4 : 1.52 : 2.08
two more trials with w/c ratio 0.35 and 0.45 are done.
What are flaky and elongated aggregates? How can the shape of aggregate influence strength of concrete? Following is the result of a sieve analysis of 500 gm aggregate:
| IS sieve size | 10 mm | 4.75 mm | 2·36 mm | 1·18 mm | 600 micron | 300 micron | 150 micron | lower than 150 micron |
| Weight retained in gm | 0 | 10 | 50 | 50 | 95 | 175 | 85 | 35 |
Find out the 'Fineness Modulus' of the sample
Short notes on :
How does land use affect surface runoff?
What Is Mixed Cropping?
What is river meandering?
What are the common materials used for constructing headworks?
What is working stress method ?
Short notes on :
How does land reclamation affect soil fertility?
