Concrete Technology (General Engineering) (SSC JE)

Total Questions: 53

41. The minimum time before striking the formwork for columns as per IS 456 is : [RRB S.S.E. (Secunderabad) 01.09.2015 (Shift-I)]

Correct Answer: (d) 16 –24 hr.
Solution:

The minimum time before striking the formwork for columns as per IS 456 is 16-24 hr.

42. The minimum time before striking the props to arches (less than 6 m) as per IS 456 is : [RRB S.S.E. 01.09.2015 (Shift-II)]

Correct Answer: (a) 14-day
Solution:

43. Concrete in a member represented by a core test shall be considered acceptable, if the average equivalent cube strength of the cores is equal to at least X% of the corresponding cube strength. What is the value of X? [RRB S.S.E. 03.09.2015 (Shift-II)]

Correct Answer: (d) 85
Solution:

Concrete is the member represented by a core test shall be considered acceptable, if the average equivalent cube strength of the cores is equal to at least 85 percent of the cube strength of the grade of concrete specified for the corresponding age and no individual core has a strength less than 75 percent.

44. Which of the following is not used in the design of concrete mixes as per the relevant Indian standard? [RRB S.S.E. 01.09.2015 (Shift-III)]

Correct Answer: (d) Bulk density of cement
Solution:

Factors affecting the choice of mix proportioning.
• Compressive strength
• Workability
• Maximum nominal size of aggregate
• Grading and type of aggregate.

45. Strength of commonly used concrete, for constructing low rise residential building is: [RRB S.S.E (Bilaspur/Secunderabad) 21.12.2014]

Correct Answer: (c) 15000 psi
Solution:

Strength of commonly used concrete, for constructing low rise residential building is 15000 psi.

46. The activity of batching in production of concrete refers to: [RRB S.S.E (Bilaspur/Secunderabad) 21.12.2014 ]

Correct Answer: (a) Weighing of all ingredients within the acceptable tolerances for all batches
Solution:

The activity of batching in production of concrete refers to weighing of all ingredients within the acceptable tolerances for all batches.

Batching–It refers to controlling the quantity of each material required for making a concrete mix in each batch.

Aggregate, admixture & water measured with accuracy of ±3% batch quantity & cement has ±2% of batch quantity.
There are two types of batching–
 1. Weight batching
2. Volume batching

47. The grade M25 of concrete would approx, refer to the mix [RRB JE (Bilaspur/Guwahati/Patna) 14.12.2014 ]

Correct Answer: (c) 1 : 1 : 2
Solution:

48. The function of sand in concrete is [BPSC AE (GEN. ENGG.) 07.08.2019]

Correct Answer: (a) To reduce shrinkage
Solution:

Sand is used in concrete as an inert material.
Property of sand in concrete mix–
(i) Function of sand in concrete to reduce shrinkage.
(ii) It increases the volume of mortar and makes mortar more economical.
(iii) It renders structure more resistant against atmospheric agencies.
(iv) Well graded type sand adds to the density of mortar.

49. Rounded aggregate in concrete [BPSC AE (GEN. ENGG.)-2001]

Correct Answer: (d) Leads to poor development of bond
Solution:

Rounded aggregate– It require least water cement ratio while angular aggregate requires highest water cement ratio.

Angular aggregate– It have voids ratio ranging 38 to 45%. In case of angular aggregate interlocking between the particles is good and development of bond is also better than rounded aggregate.

Flaky aggregate– These types of aggregates least dimension in less than 3/5 of mean dimension.

50. Which of the following is not a physical property of materials? [JSSC JE (GEN. ENGG.)- 03.07.202]

Correct Answer: (a) Abrasion
Solution:

Abrasion is not a physical property of materials.
• Swelling, water adsorption and bulk density are physical property of materials.