TOS -6 Assignment -5 Solution to Theory

Q.1 Write short notes on:

1. Water-cement-ratio in concrete
What is water cement ratio ? It is the ratio of the mass of water to the mass of cement added to concrete. The
water cement ratio formula directly affects the strength & durability of the concrete. The typical water-cement ratio
varies between 0.40 - 0.60 for different grades of concrete mix.

Table 5 of IS 456 gives maximum water cement ratio for various environmental conditions

2. Workability of concrete
3. Formwork of concrete

Concrete achieves minimum strength as per the following :

Therefore, the formwork can be removed after minimum period as specified in IS 456 as follows:
4. Compaction of concrete

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5. Curing of concrete
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6. Ready mix concrete

7. Admixtures of concrete - mineral admixtures and chemical admixtures
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8. Creep of concrete
9. Shrinkage of concrete

Concrete shrinkage is the decrease in length or volume of a concrete caused by changes in moisture
content or chemical reactions. All concrete undergoes shrinkage, and there are four categories of
shrinkage seen in concrete:

 Drying Shrinkage,
 Chemical Shrinkage,
 Plastic Shrinkage, and
 Autogenous Shrinkage.

Drying shrinkage is the significant shrinkage mechanism in most concrete. Moisture lost during
drying shrinkage is evaporated into the environment as the concrete dries out, and if not properly
managed, it can lead to wide joint openings, cracking from internal stresses, and slab curling.
 The amount of drying shrinkage that occurs in concrete structures depends on the constituent
materials, mixture proportions, curing, drying environment, and restraint.

10.High strength concrete

11.Constituents of cement

 Cement consists essentially of compounds of lime (calcium oxide, CaO) 60 -65% mixed with silica (silicon dioxide,
SiO2 ) and alumina (aluminium oxide, Al2O3 ).

 The lime is obtained from a calcareous (lime-containing) raw material such as including shale, chalk, and
limestone and silica derived from an argillaceous (clayey) material along with other oxides of aluminium, iron
and magnesium.

 Gypsum ( Ca SO 4 ) is added in small percentage(up to 3%) to regulate the setting rate of cement

 These ingredients are heated in a rotary kiln at 1500 degree Celsius and then ground in fine powder. Due to
heating process constituents of cement form bouge’s compounds such as C3S, C2S, C3A and C4AF that further
react with water to form cement paste.

12.Special cements
Q.2 Explain flat slab design
Q.3 Explain rectangular grid and diagrid design
Grid floor can be designed using following methods:
 Q.4 Explain precast concrete

Precast concrete is made by pouring concrete into a mould in a factory or plant, instead of directly
pouring it at the construction site. The cured concrete product is then transported to the
construction site and installed as a finished material.

Precast concrete is a durable and sustainable material that can withstand harsh weather conditions
and is fully recyclable at the end of its life cycle. It provides faster construction timelines and lower
labour costs to greater design flexibility and customization

1. Precast concrete walls

These are large concrete panels that can be used to create exterior or interior walls. They are typically
manufactured in large, rectangular panels that can be connected and installed quickly at the
construction site.

2. Precast concrete beams and columns

They are designed to provide structural support to buildings or bridges, and are manufactured in
different shapes and sizes depending on specific load requirements.

3. Precast concrete slabs and planks

These are flat panels that can be used as floors or roofs in buildings. They are typically manufactured
in long, thin sections that can be easily transported and installed at the construction site.

4. Precast concrete stairs

These are pre-manufactured elements that can be utilised to construct staircases in buildings. They
come with pre-installed treads and risers and can be customised to meet specific building design
requirements.

5. Precast concrete retaining walls

These are elements that are used to retain soil or other materials. They are typically manufactured
with interlocking edges that can be connected to create a continuous wall, and can be designed to
meet specific load requirements.

Advantages of precast concrete

The usage of precast concrete has several advantages in construction projects. Here are some of the
key benefits :
 It ensures consistent quality and uniformity, as it is manufactured in a controlled environment.

This reduces defects and improves the finished product's overall quality.
  Since it is manufactured off-site it allows for faster on-site construction, reducing overall

construction time and increasing project efficiency.

 It is a durable material that can withstand harsh weather and heavy loads, while also being

resistant to fire, rot, and insects, making it a long-lasting choice.

 With the ability to be manufactured in various shapes, sizes, and finishes, it offers greater

design flexibility and customization to suit specific requirements.

 It is a sustainable construction material that can be made from recycled materials and is fully

recyclable at the end of its life cycle.

Overall, precast concrete can provide significant advantages in terms of speed, quality, cost, and
sustainability compared to traditional construction methods.

Pre-finished surfaces :

It can be cast with a variety of finishes, including smooth, textured, and polished surfaces,
which can be further enhanced with a range of colour options.

Ornamental features :

It can be used to create a variety of decorative features, including cornices, mouldings, and
medallions, that can be customised to suit specific design requirements.

Sculptures and statues :

It can be used to create large-scale sculptures and statues that can be placed in public spaces or
used as decorative elements in buildings.

Landscaping features :

It can be used to create landscaping features such as benches, planters, and retaining walls,
which can be designed to complement the surrounding environment.

Signage and wayfinding :

It can be used to create signage and wayfinding elements such as monuments, directional
markers, and identification signs, which can be customised to match the surrounding
architecture.

Precast concrete is an attractive choice for many construction projects due to its numerous
advantages. One of the primary benefits is its ability to reduce construction time and labour
costs due to off-site manufacturing.

Additionally, it is very durable and can withstand harsh weather conditions and heavy loads,
making it a long-lasting material choice. It also offers design flexibility, with various shapes,
sizes, and finishes available to suit specific design requirements. Moreover,. It is also a
sustainable material choice, made from recycled materials and fully recyclable at the end of its
life cycle.

Overall, precast concrete is a cost-effective and efficient material choice that can help to reduce
construction time, labour costs, and increase durability, making it a popular choice for a wide
range of construction projects.

Q.5 Explain difference between one way and two way slabs

Q.6 Explain concept of under reinforced, balanced and over reinforced beam

Q.7 Explain difference between singly and doubly reinforced beam

Q.8 Explain basics of limit state method of design and partial safety factors
Q.9 Explain slenderness ratio and difference between short and long columns
Q.10 Explain methodology of shear design of beam
 If then minimum shear stirrups to be provided.
Else, shear stirrups need to be designed for size and spacing to provide addition shear strength as per
shear force diagram for the beam.

Types of shear stirrups are:

 Vertical stirrups
 Inclined stirrups
 Bent up bars
Q.11 Explain design of circular column
This gives spacing criteria as follows:
Q.12 Explain design of doglegged staircase

Slab spanning longitudinally: