Civil Engineering - Concrete Technology - Discussion

Cement mixtures.

Mixtures are always listed as parts Cement to Sand to Aggregate. Following are typical cement mixtures description:

Rich: 1 part cement, 2 parts sand, 3 parts coarse aggregate. A rich mix is used for concrete roads and waterproof structures.

Standard: 1 part cement, 2 parts sand, 4 parts coarse aggregate. A standard mix is used for reinforced work floors, roofs, columns, arches, tanks, sewers, conduits, etc.

Medium: 1 part cement, 2 1/2 parts sand, 5 parts coarse aggregate. A medium mix is used for foundations, walls, abutments, piers, etc.

Lean: 1 part cement, 3 parts sand, 6 parts coarse aggregate. A lean mix is used for all mass concrete work, large foundations, backing for stone masonry, etc.

A rich mixture contains a high proportion of cement. A lean mixture is a mixture of concrete or mortar with a relatively low cement content. A harsh mixture of concrete is one without mortar or aggregate fines, resulting in an undesirable consistency and workability.

Please read the question carefully option E is right because they ask incorrect statement and all option are correct actually, so the answer is option E i.e none of this.

For the same strength, the water content and cement will be less in rich mixes so chances of excessive water are more in lean concrete. Hence A is incorrect.

I think Option C should be applied because"if the water-cement ratio is less than 0.40 then it is not workable and causes honeycombed structure".

Rich mix concrete>15%cement contain.
Normal mix 10%<cement contain<15%.
Lean mix<10%cement contains.

I think the reason behind A as the answer is the word Excessive water. Because more the water less is strength.

Yes, option E is correct answer because the lean mix does not contain more strength as compared to rich mix.

Yes, the rich mix is stronger than a lean mix.

How can option A be incorrect?

Anyone describe it.

All the options are correct. Please check and rectify the correct answer.