Reviewer 5 Flashcards
Concrete contains (i)Siliceous aggregates, having higher coefficient of expansion (ii)Igneous aggregates, having intermediate coefficient of expansion (iii)Lime stones, having lowest coefficient of expansion
[ A ] i and iii [ B ] ii and iii [ C ] i and ii [ D ] i, ii and iii
D
Select the incorrect statement
[ A ] R.C.C has better fire resistance than steel
[ B ] R.C.C. structure is economical than steel structure
[ C ] Strength of concrete decreases as age increases
[ D ] R.C.C can be used for under water and marine structures
Strength of concrete decreases as age increases
Water cement ratio is the ratio of [ A ] Water to cement by weight [ B ] Water to cement by volume [ C ] Cement to water by weight [ D ] Cement to water by volume
A. Water to cement by weight
Concrete is [ A ] Weak in tension [ B ] Strong in tension [ C ] Strong in both tension and compression [ D ] Weak in compression
A] Weak in tension
The entrained air in concrete [ A ] Increases the strength [ B ] Decreases the resistance to weathering [ C ] Increases the workability [ D ] Decreases the workability
C. Increases the workability
Concrete is unsuitable for compaction by vibration if it is [ A ] Semi –plastic [ B ] Plastic [ C ] Earth moist [ D ] Dry
B. Plastic
The strength and quality of concrete depends upon (i)Grading of aggregates (ii)Shape of aggregates (iii)Surface area of aggregates (iv)Surface texture of aggregates [ A ] i, ii and iv [ B ] ii, iii and iv [ C ] i, iii and iv [ D ] i, ii, iii and iv
D
In order to avoid segregation, fresh concrete should be dropped from a height of
Less than one meter
The process of hardening of concrete in the presence of water is called
Hydration
The process of keeping the concrete structure moist is called
Curing
The separation of water or water cement mixture from the freshly laid concrete is known as
Bleeding
The continuous strain, which the concrete undergoes due to application of external loads is called
Creep
The process of conversion of plastic concrete to solid stage is called
Setting
At 28 days of curing concrete attains a strength of
90 to 95%
In a mass concrete, the aggregates occupy a space of
75%
The coarse aggregate which possess the property of good interlocking are
angular shape
While placing of concrete the thickness of each layer for R.C.C. is
150 to 300 mm
In a two way slab flexural bending develops
In Mutually perpendicular directions
Slabs which are supported in such a way that the corners are prevented from lifting are referred to as;
Restrained slabs
The size of the mesh at each corner meant for torsion reinforcement in a rectangular slab of size (Lx ´ Ly) is Lx = shorter span Lx = Longer span
0.2 Lx x 0.2 Lx
The span/over all depth ratio for a simply supported two-way slab according to IS : 456-2000 is given by
28
According to IS: 456-2000, the span/overall depth ratio for a continuous two-way slab in order to control deflection is given by
32
Reinforced concrete slab supported only on columns is said to be
Flat slab
According to IS: 456-2000 the ultimate moment of resistance of a slab for Fe - 415 HYSD bars is
Mu = 0.138 fck bd2
In a limit state method of design, when shear reinforcement is not provided, the calculated shear stress at the critical section of a slab shall not exceed
Ks 0.25 v fck
The moments developed in the slab are influenced by the following factors i.Short span ii.Long span iii.Type of supporting edge. iv.Magnitude and type of load on slab
i, ii , iii and iv
Minimum reinforcement in slabs, when High yield strength deformed bars
0.12% of gross cross sectional area
Permissible width of crack at the surface of concrete for „moderate‟ environmental conditions according to IS : 456-2000 is
0.2 mm
Limiting moment of resistance of a singly reinforced section for mild steel is
Mu = 0.148 fck bd2
In slabs the Maximum horizontal distance between parallel main reinforcement should not exceed i.Three times effective depth ii Five times effective depth iii 300mm iv 450 mm
i and iii
Slenderness ratio of the column is the ratio of
the effective length to least lateral design
A Column is said to be short, when the slenderness ratio is
Less than 12
