The individual variation between test strength of sample should not be more than
A. ±5% of average
B. ±10% of average
C. ±15% of average
D. ±20% of average
Answer: Option C
This Question Belongs to Civil Engineering >> Concrete Technology And Design Of Concrete Structures
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In symmetrically reinforced sections, shrinkage stresses in concrete and steel are respectively
A. Compressive and tensile
B. Tensile and compressive
C. Both compressive
D. Both tensile
Critical section for shear in case of flat slabs is (adopting standard notations)
A. At a distance of effective depth of slab from periphery of column/drop panel
B. At a distance of $$\frac{{\text{d}}}{2}$$ from periphery of column/capital/drop panel
C. At the drop panel of slab
D. At the periphery of column
A. depends on as, only
B. depends on aCbC only
C. depends on both crst and acbc
D. is independant of both ast and acbc where d is the effective depth, ast is per-missible stress in steel in tension and ocbc is permissible stress in concrete in bending compression.
The diameter of ties in a column should be
A. More than or equal to one fourth of diameter of main bar
B. More than or equal to 5 mm
C. More than 5 mm but less than one-fourth of diameter of main bar
D. More than 5 mm and also more than one-fourth of diameter of main bar
Concept:
The smaller the size of the cube, the closer to its parent geometry.
Explanation:
For cube test, two types of specimens either cubes of 15 cm × 15 cm × 15 cm or 10 cm × 10 cm × 10 cm depending upon the size of aggregate are used.
For most of the works cubical moulds of size, 15 cm × 15 cm × 15 cm are commonly used.
This concrete is poured into the mould and tempered properly so as not to have any voids.
After 24 hours these moulds are removed and test specimens are put in water for curing.
The top surface of these specimen should be made even and smooth.
This is done by putting cement paste and spreading smoothly on the whole area of the specimen.
As per Clause 15.4 of IS 456-2000, the test results of the sample shall be the average of the strength of three specimens. The individual variation should not be more ± 15% of average than of the average. If more, the test results of the sample are invalid.