Question

- Which one is NOT the normal component of plain concrete?

Cement

Gravel

Sand

Air

Steel Rods

- What is the possible range of strength of concrete that you normally use in residential construction?

500-1000 psi

3000-5000 psi

30,000-50,000 psi

300,000-500,000 psi

- Which of the following statements about coarse aggregate in concrete is NOT true?

Aggregates should be relatively free from flat and elongated particles

Uniform size (same size) coarse aggregates are good for making concrete.

Well graded coarse aggregate is best for making concrete.

Heavily porous coarse aggregate is not good for making concrete.

Answer 1

Answer 1 :

Steel Rod is not the normal component of plain concrete.

Explanation :

Plain cement comprises mainly cement,fine aggregate (cement),coarse aggregate (gravel) with some air also which is being entraped in the voids avaolable.So the normal component of plain cement concrete does not contail steel rods.

Answer 2 :

The most appropriate answer is option B.

Explanation :

The compressive strength of concrete used for residential construction should not be less than 2500 psi.So the concrete compressive strength requirements can vary from 2500 psi (17MPa) to 4000 psi (28MPa) for residential construction work.The given range is applicable when weathering probability is being ignored.

Answer 3 :

   Answer is B. i.e uniform size coarse aggregates are good for making concrete,so this statement is false.

Explanation :

     1) For a good strength concrete ,the coarse aggregates should be relatively free from flat and elongated concrete,so that we may get the desired trength and workability,so the given statement is true.

2) Well graded aggregate contains all size of aggregate,thus imparting the desired properties to cement,thats why well graded coarse aggregates are the best for making concrete.

3) If the coarse aggregate is heavily porous,it will allow water to flow through it,which will destory concrete strength ,so heavily porous coarse aggregate is not good for making concrete.