GATE Civil Engineering (CE) 2019 Shift 2 Solved Paper

Question : 16 of 65

Marks: +1, -0

The characteristic compressive strength of concrete required in a project is

25 {MPa}

and standard deviation in the observed compressive strength expected at site is

4 {MPa}

. The average compressive strength of cubes tested at different water-cement (w/c) ratios using the same material as is used for the project is given in the table.

w/c(%)	45	50	55	60
Average compressive strength of cubes (MPa)	35	25	20	15

The water-cement ratio (in percent, round off to the lower integer) to be used in the mix is________

Your Answer:

Validate

Solution:

{f}_{ {ck}}=25 ; σ=4 {MPa}

{f}_{ {m}}= {f}_{ {ck}}+1.65 σ=31.6 {MPa}

Using interpolation

{w} {/} {c}

req.

=50-\;{(50-45)}/{(35-25)} ×(31.6-25)

=46.7

(Rounded off to the lowest integer).

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