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Explanation:

Hardening of Lime under Water:

• Hydraulic lime consists of calcium oxide, magnesium oxide, calcium silicates, and aluminum silicates.
• On hydration, it forms hydroxides of calcium and magnesium.
• When sand is added to lime for the preparation of mortars, complicated chemical reactions take place.
• The chief reaction is the decomposition of complex aluminum-calcium silicate into hydrated calcium silicate and hydrated calcium aluminates.
• Also calcium hydrate is formed due to the hydration of free lime. To some extent, calcium oxide remains unslaked.
• All these reactions take place in the presence of water.
• Calcium silicates and calcium aluminates crystallize and form a hard substance that has great strength.
• The calcium hydrate formed is highly soluble in water, rises to the surface in the form of a solution, gets the free supply of carbon dioxide, and hardens in the same way as fat lime.
• It crystallizes to form calcium carbonate. Thus the setting of hydraulic lime depends upon water because reactions take place only when water is added.
• It is due to this reason that hydraulic lime is most suitable for use in structures underwater.
• Hardening of lime does not depend on air and therefore, should not be slaked immediately after burning. Water should be added just before use.

Concept:

Relationship Between e, w, G, s is given by,

\({\rm{e;}} = {\rm{;}}\frac{{{\rm{wG}}}}{{\rm{s}}}\)               …….

(i) Relationship between γt, G, s, γw, e is given by,  

\({{\rm{γ }}_{\rm{t}}}{\rm{;}} = {\rm{;}}\frac{{\left( {{\rm{G}} + {\rm{se}}} \right){{\rm{γ }}_{\rm{w}}}}}{{1 + {\rm{e}}}}\)     …….

(ii) Where,

e = void ratio, w = water content, G = Specific gravity of soil, s = Degree of saturation, γt = density of soil particles, γw = density of water

Calculation:

Given, w = 20% = 0.20, γt = 2 g/cm3, , and G = 2.6

Specific gravity of water = 1 .i.e. γw = 1 g/cm3

\({{\rm{γ }}_{\rm{t}}}; = ;\frac{{\left( {G + se} \right){{\rm{γ }}_{\rm{w}}}}}{{1 + e}}; = ;\frac{{\left( {G + wG} \right) \times \gamma_w}}{{1 + e}}\)

\({{\rm{γ }}_{\rm{t}}}; = ;\frac{{\left( {1 + w} \right) \times G\gamma_w}}{{1 + e}} = ;\frac{{\left( {1 + 0.2} \right) \times 2.6\ \times 1}}{{1 + e}}\)

⇒ 1 + e = 1.56

⇒ e = 0.56

From (i)

\(0.56{\rm{;}} = {\rm{;}}\frac{{0.2 \times 2.6}}{S}\)

S = 0.928

∴ Degree of saturation = 92.8%

Explanation:

Tie Line:

(i) If the distance of the point or detail from the chain line is very large, then long offsets need to be taken.

(ii) Tie lines are the lines that are run to locate details in order to avoid long offsets.

So line CD represented in the figure is a tie line.

Important Points

Base line: It is the long survey line which is run through the middle of the area to be surveyed. The frame work of triangles is built on the base line.

Here AB is the base line

Check line:

(i) These lines are run to check the accuracy of the traverse consisting of a frame work of triangles

(ii) Check lines are measured in the field during the survey process of the land.

(iii) It is also known as Proof lines.

Concept:

Load factor: The ratio of average load to the maximum demand during a given period is known as the load factor.

Load factor = average load/maximum demand

If the plant is in the operation for T hours

\(Load;factor = \frac{{Avearge;load \times T}}{{Maximum;demand \times T}}\)

\(= \frac{{Units;generated;in;T;hours}}{{Maximum;demand \times T}}\)

Important Points

• The load factor may be daily load factor, monthly or annually if the period considered is a day or month, or year.
• The load factor is always less than 1 because the average load is smaller than the maximum demand.
• It plays a key role in determining the overall cost per unit generated.
• The higher the load factor of the power station, the lesser will be the cost per unit generated, is because a higher load factor means lesser maximum demand.
• The station capacity is so selected that it must meet the maximum demand.
• Now, lower maximum demand means a lower capacity of the plant which reduces the cost of the plant.

To find the largest scale among given set of scale, Covert all the scale into its Representative fraction (RF).

I) For 1 cm = 100 m

\(RF = \frac{1}{{10000}} = 0.0001;\left( {Largest} \right)\)

ii) For 1:42000,

\(RF = \frac{1}{{42000}} = 0.00002381\)

iii) For 1 cm = 50 km

\(RF = \frac{1}{{5000000}} = 0.0000002\)

iv) For 1/500000

\(RF = \frac{1}{{500000}} = 0.000002\)

Explanation:

Polyvinyl chloride ((C2H3Cl)n):

• PVC stands for Polyvinyl chloride.
• It is widely used as a thermoplastic.
• It is a synthetic polymer made from the polymerization of vinyl chloride.
• It comes in two basic forms i.e rigid and flexible.
• Because of its hardness, it is used in a variety of applications in the building and construction, health care, automobiles, etc.

Explanation:

• Gypsum is composed of Calcium sulphate (CaSO4) and water (H2O). ​Its chemical name is calcium sulphate dihydrate (CaSO4. 2H2O).
• Gypsum slows down the setting time of cement.
• It is a crystalline mineral composed of calcium sulfate dihydrate.
• Gypsum helps in controlling the rate of hardening of the cement.
• It also prevents early hardening allowing long working time, hence we can say that it helps in the rapid setting of cement.

Concept:

Representative Fraction (R.F.):

• It is a ratio or fraction, that expresses the mathematical relationship between map and land.
• It is the ratio of the distance between any two fixed points on the map to the original distance on the land.

\(\rm{R.F. =\frac{Distance; on; Map}{Actual; corresponding; distance; on ;ground}}\)

Scale (S): It is a fixed ratio that every distance on the plan bears with the corresponding distance on the ground.

Calculation:

Given, scale is 1 cm =100 km

∴ \(R.F = \frac{{1;cm}}{{100;km}} = \frac{{1;cm}}{{10000000;cm}} = \frac{1}{{10000000}}\)

Concept:

A truss is used in architecture and structural engineering as a means of structural support. The simplest type of truss is a triangle truss.

Simple triangle trusses consist of a series of triangles arranged so that the weight being supported is distributed evenly for maximum support.

The basic triangle in a truss consists of three beams connected in the corners by three joints.

A triangle on its own could be considered a simple truss, but most trusses are comprised of many triangles, connected by a series of chords. An upper chord and lower chord will span the length of the truss, with at least two triangles along the chord.

Explanation: 

• An equivalent area is used when computing the strength requirements of a reinforced concrete section.
• The reinforcement is usually steel which has a much higher strength per cross-section area than concrete. So an equivalent area of concrete is used to make the calculations easier and simpler.
• The cross-sectional area of concrete is replaced by the equivalent area of steel with the same strength equivalence.
• The equivalent area concept is used to make sections homogeneous.
• Modular Ratio (m) is defined as the ratio of the modulus of Elasticity of Steel to the Modulus of Elasticity of Concrete,   \(m = \frac{E_{s}}{E_{c}}\)
• The equivalent area of the section = Area of concrete + m × Area of steel​

Equivalent area  \(A_{e}= A_{c}+mA_{t}\)

At = Area of steel bars, Ac = Area of concrete, m = Modular ratio

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