Introduction to Philosophies

Contents

**Recall the following tests to determine the compressive strength: i. Cube Test ii. Cylinder Test** 1

**Describe the Characteristics strength of Concrete along with its acceptance criteria.** 2

**Recall the Tensile strength of Concrete** 3

**Describe design procedure for Concrete mix design as per IS:10262 Standard.** 3

**Recall the Stress-Strain curve for concrete.** 4

**Recall different Modulus of elasticities of concrete.** 5

**Store the significance of Creep in Concrete.** 6

**Recall different grades of steel used in RCC.** 7

**List basic properties of Steel.** 8

**List the relevant IS codes used for design and analysis of RCC.** 9

**State the Stripping time for various types of formwork.** 11

**Define the term RCC**

RCC stands for Reinforced Concrete Cement, which is a composite material consisting of concrete and reinforcement, usually in the form of steel bars or mesh. RCC is used in the construction of various structures such as buildings, bridges, dams, and others due to its strength, durability, and versatility. The combination of concrete and reinforcement provides a material that can resist both compressive and tensile forces, making it ideal for many different types of construction projects.

In summary, RCC is a construction material that combines concrete and reinforcement to provide strength and durability to various structures.

**Recall the following tests to determine the compressive strength: i. Cube Test ii. Cylinder Test**

The cube test and cylinder test are two standard methods used to evaluate the compressive strength of concrete.

i. Cube Test: The cube test is performed by casting cubes of concrete with specific dimensions and curing them for a specified period of time. The cubes are then subjected to compressive loads using a compression testing machine, and the maximum load the concrete can withstand is recorded. The compressive strength is calculated by dividing the maximum load by the cross-sectional area of the cube.

ii. Cylinder Test: The cylinder test is performed in a similar manner to the cube test, but instead of casting cubes, cylindrical specimens are cast and tested. The cylindrical specimens are also subjected to compressive loads using a compression testing machine, and the maximum load the concrete can withstand is recorded. The compressive strength is calculated by dividing the maximum load by the cross-sectional area of the cylinder.

In summary, the cube test and cylinder test are two standard methods used to determine the compressive strength of concrete. These tests are performed by casting concrete specimens, curing them, and then subjecting them to compressive loads to determine the maximum load they can withstand. The compressive strength is then calculated based on the maximum load and the cross-sectional area of the specimen.

**Describe the Characteristics strength of Concrete along with its acceptance criteria.**

Concrete is a composite material that has several important mechanical properties, including strength, durability, and workability. The strength of concrete is defined as its ability to resist various loads and stress. There are several factors that affect the strength of concrete, including the type of cement used, the mix proportions, the curing conditions, and the water-to-cement ratio.

The acceptance criteria for the strength of concrete are used to determine whether the concrete has achieved the desired strength for a specific application. These criteria vary depending on the type of structure, the load conditions, and the local building codes. Some common acceptance criteria for concrete strength include:

- Minimum compressive strength: This is the minimum strength required for a specific application, such as a building foundation or a bridge deck. The minimum compressive strength is typically specified in units of megapascals (MPa).
- Design strength: The design strength is the strength required to support the loads and stress that the structure is expected to experience over its service life. The design strength is typically specified as a fraction of the minimum compressive strength, such as 80% or 90%.
- Characteristic strength: The characteristic strength is the average strength of a set of concrete cubes or cylinders tested in accordance with a specific standard. The characteristic strength is typically used as a basis for determining the design strength.

fck=fav−1.65σ

In summary, the strength of concrete is a key mechanical property that affects its performance in various structures. The acceptance criteria for concrete strength vary depending on the type of structure and the loads it is expected to experience, and are typically specified as a minimum compressive strength, design strength, or characteristic strength.

**Recall the Tensile strength of Concrete**

Tensile strength refers to a material’s ability to resist forces that tend to pull it apart, or tensile forces. Concrete is a composite material that is strong in compression but weak in tension. This means that it is capable of resisting crushing forces, but is susceptible to cracking and breaking under tensile forces.

To overcome the weak tensile strength of concrete, reinforcement in the form of steel bars or mesh is added to the concrete. This reinforcement helps to transfer tensile forces from the concrete to the reinforcement, which has a much higher tensile strength.

The tensile strength of concrete is usually expressed as a ratio of its compressive strength. For example, a concrete mix with a compressive strength of 40 MPa might have a tensile strength of only 4 MPa, or 10% of its compressive strength.

In summary, the tensile strength of concrete refers to its ability to resist tensile forces. Concrete is strong in compression but weak in tension, and reinforcement is added to improve its tensile strength. The tensile strength of concrete is usually expressed as a ratio of its compressive strength.

**Describe design procedure for Concrete mix design as per IS:10262 Standard.**

The IS:10262 standard provides guidelines for the design of concrete mix proportions for specific applications. The mix design procedure involves several steps, including determining the required strength, selecting the appropriate type of cement, determining the water-to-cement ratio, selecting the appropriate aggregates, and determining the proportions of the various components of the mix.

The steps involved in the concrete mix design procedure as per the IS:10262 standard are:

- Determine the required strength: The first step in the mix design procedure is to determine the required strength of the concrete. This is usually specified as the minimum compressive strength that the concrete must achieve.
- Select the appropriate type of cement: The next step is to select the appropriate type of cement based on the type of structure, the environmental conditions, and the desired setting time.
- Determine the water-to-cement ratio: The water-to-cement ratio is an important factor in determining the strength and workability of the concrete. The IS:10262 standard provides guidelines for selecting the appropriate water-to-cement ratio based on the desired strength and workability.
- Select the appropriate aggregates: The next step is to select the appropriate aggregates based on the size, shape, and density of the aggregates and the type of structure.
- Determine the proportions of the various components of the mix: The final step is to determine the proportions of the various components of the mix, including the cement, water, aggregates, and any admixtures, based on the desired strength and workability.

In summary, the concrete mix design procedure as per the IS:10262 standard involves several steps, including determining the required strength, selecting the appropriate type of cement, determining the water-to-cement ratio, selecting the appropriate aggregates, and determining the proportions of the various components of the mix. These steps are followed to ensure that the concrete mix proportions are appropriate for a specific application and provide the desired strength and workability.

**Recall the Stress-Strain curve for concrete.**

A stress-strain curve is a graphical representation of the relationship between the stress applied to a material and the resulting strain. The stress-strain curve provides information about the material’s mechanical properties, such as its strength, stiffness, and ductility.

The stress-strain curve for concrete is a graph that shows the relationship between the compressive stress applied to a cylindrical or cubic concrete specimen and the resulting strain. The stress-strain curve for concrete is typically nonlinear, meaning that the strain does not increase proportionally with the applied stress.

The stress-strain curve for concrete can be divided into three distinct regions:

- Linear Elastic Region: In the linear elastic region, the concrete behaves in a linear and elastic manner. This means that the strain is proportional to the stress and the concrete returns to its original shape when the stress is removed.
- Plastic Region: In the plastic region, the concrete begins to deform irreversibly. This means that the concrete will not return to its original shape when the stress is removed. The slope of the stress-strain curve in the plastic region is less steep than in the linear elastic region, which indicates that the concrete is becoming less stiff and more ductile.
- Failure Region: In the failure region, the concrete has reached its maximum strength and has failed. This is indicated by a rapid increase in strain with no corresponding increase in stress. The point at which the concrete fails is known as the maximum compressive strength.

In summary, the stress-strain curve for concrete is a graphical representation of the relationship between the compressive stress applied to a concrete specimen and the resulting strain. The curve is typically nonlinear and can be divided into three distinct regions: the linear elastic region, the plastic region, and the failure region. The stress-strain curve provides important information about the concrete’s mechanical properties and helps engineers to design structures that can resist compressive forces.

**Recall different Modulus of elasticities of concrete.**

The modulus of elasticity (MOE) of a material is a measure of its stiffness. It is defined as the ratio of the applied stress to the resulting strain within the elastic limit of the material. In other words, it measures how much a material will deform under a given load. The higher the MOE, the stiffer the material and the less it will deform.

There are different modulus of elasticities of concrete, each representing a different aspect of its stiffness. These include:

- Young’s modulus of concrete: Young’s modulus is a measure of the longitudinal stiffness of a material. In the case of concrete, it measures the concrete’s ability to resist longitudinal (axial) compression.
- Shear modulus of concrete: Shear modulus is a measure of the transverse stiffness of a material. In the case of concrete, it measures the concrete’s ability to resist shear forces.
- Bulk modulus of concrete: Bulk modulus is a measure of the volumetric stiffness of a material. In the case of concrete, it measures the concrete’s ability to resist changes in its volume.

In summary, the different modulus of elasticities of concrete are measures of its stiffness. These include Young’s modulus, which measures longitudinal stiffness, shear modulus, which measures transverse stiffness, and bulk modulus, which measures volumetric stiffness. Understanding the modulus of elasticities of concrete is important for engineers when designing concrete structures, as it provides information about the material’s ability to resist different types of loads.

**Store the significance of Creep in Concrete.**

Creep is the slow and gradual deformation of a material under a sustained load. In the case of concrete, creep refers to the time-dependent deformation of concrete under a sustained compressive load. This can result in a reduction of the concrete’s compressive strength over time.

The significance of creep in concrete is that it affects the long-term performance and durability of concrete structures. When a concrete structure is subjected to a sustained load, the creep deformation of the concrete can cause the structure to deform or even fail over time. This can result in cracking, spalling, and other forms of degradation that can compromise the safety and performance of the structure.

In order to minimise the effects of creep in concrete structures, engineers must take into account the creep properties of concrete when designing the structure. This may involve using higher-strength concrete, reducing the size of concrete members, or increasing the reinforcement in the structure.

In summary, creep is the slow and gradual deformation of concrete under a sustained load. The significance of creep in concrete is that it affects the long-term performance and durability of concrete structures. Engineers must take into account the creep properties of concrete when designing concrete structures in order to minimise the effects of creep.

**Recall different grades of steel used in RCC.**

Steel is a key component of RCC and is used to reinforce the concrete and increase its strength and stiffness. There are several different grades of steel used in RCC, each with different properties and characteristics.

The most common grades of steel used in RCC include:

- Mild Steel: Mild steel is a low-carbon steel with a carbon content of 0.15% to 0.3%. It is the most commonly used steel in RCC due to its low cost and high ductility.
- High Yield Strength Deformed Bars (HYSD): HYSD bars are high-strength reinforcing bars with a yield strength greater than mild steel. They are commonly used in RCC due to their higher strength and lower ductility.
- TMT Bars: TMT bars are high-strength reinforcing bars that are thermally treated to improve their strength and toughness. They are commonly used in RCC due to their high strength, high ductility, and corrosion resistance.
- Stainless Steel: Stainless steel is a high-alloy steel that is resistant to corrosion. It is used in RCC for structures that require high levels of corrosion resistance, such as bridges, marine structures, and chemical plants.

In summary, there are several different grades of steel used in RCC, including mild steel, high yield strength deformed bars (HYSD), TMT bars, and stainless steel. The choice of steel grade depends on the specific requirements of the RCC structure, including its strength, ductility, and corrosion resistance requirements.

**List basic properties of Steel.**

Steel is a key component of Reinforced Cement Concrete (RCC) and is used to reinforce the concrete and increase its strength and stiffness. The basic properties of steel include:

- Strength: Steel is a strong and durable material that is capable of withstanding high stress and tension.
- Ductility: Steel has high ductility, which means it can be bent and stretched without breaking. This allows steel to deform under stress and distribute the load evenly throughout the structure.
- Toughness: Steel is a tough material that can withstand high impact loads without breaking.
- Hardness: Steel is a hard material that can withstand wear and tear.
- Elasticity: Steel has high elasticity, which means it can return to its original shape after deformation.
- Fatigue resistance: Steel has high fatigue resistance, which means it can withstand repeated stress without failure.
- Corrosion resistance: Steel can be treated to resist corrosion, making it an ideal material for use in harsh environments.

In summary, the basic properties of steel include strength, ductility, toughness, hardness, elasticity, fatigue resistance, and corrosion resistance. These properties make steel an ideal material for use in Reinforced Cement Concrete (RCC) structures.

**Describe the following methods of RCC members: i. Working Stress method ii. Ultimate Load method iii. Limit State method**

Working Stress Method:

- The Working Stress Method is an old method used to design reinforced concrete structures. This method assumes that the concrete and reinforcing steel both have a linear relationship with stress and strain, and that the structure will fail when either the concrete or the steel reaches its maximum allowable stress. The maximum allowable stress for concrete is based on its compressive strength, and for steel, it is based on its yield strength. The design of a structure using the Working Stress Method is based on the concept that the stress in the concrete and steel is kept below their maximum allowable stress levels at all times, even during the service load.

Ultimate Load Method:

- The Ultimate Load Method is a method used to design reinforced concrete structures where the structure is designed to resist the ultimate load, i.e., the maximum load it can carry before failure. The method assumes that the concrete and reinforcing steel both have a non-linear relationship with stress and strain, and that the structure will fail when either the concrete or the steel reaches its maximum strength. The design of a structure using the Ultimate Load Method is based on the concept that the stress in the concrete and steel will increase until they reach their maximum strength, at which point the structure will fail.

Limit State Method:

- The Limit State Method is a modern method used to design reinforced concrete structures. This method considers the safety and serviceability of the structure under different loads and environmental conditions. The Limit State Method takes into account both the ultimate load capacity and the serviceability limit state of the structure. The design of a structure using the Limit State Method is based on the concept of limiting the maximum stress in the concrete and steel, as well as ensuring that the structure has adequate deformation capacity and stability. The Limit State Method provides a more comprehensive evaluation of the structural behavior of a reinforced concrete structure compared to the Working Stress Method and the Ultimate Load Method.

**List the relevant IS codes used for design and analysis of RCC.**

The Indian Standards (IS) codes are the codes used for the design and analysis of Reinforced Concrete (RCC) structures in India. The relevant IS codes for RCC design and analysis are:

- IS 456:2000 – Code of Practice for Plain and Reinforced Concrete. This code provides the basic principles, procedures, and provisions for the design and construction of RCC structures, including the design of beams, slabs, columns, and footings.
- IS 13920:1993 – Ductile Detailing of Reinforced Concrete Structures subjected to Seismic Forces. This code provides guidelines for the detailing of RCC structures to ensure that they have adequate ductility, energy dissipation capacity, and seismic resistance.
- IS 13827:1993 – Guidelines for Earthquake Resistant Design of Structures. This code provides guidelines for the earthquake-resistant design of RCC structures, taking into account site-specific seismic hazard information, soil-structure interaction, and other relevant factors.
- IS 14688:2014 – Guidelines for Design and Construction of Earthquake-resistant Buildings. This code provides guidelines for the design and construction of earthquake-resistant RCC buildings, taking into account site-specific seismic hazard information, soil-structure interaction, and other relevant factors.
- IS 800:2007 – Code of Practice for General Construction in Steel. This code provides guidelines for the design and construction of steel structures, including the design of steel members and connections, and the design of composite structures using steel and concrete.

These IS codes provide a comprehensive framework for the design and analysis of RCC structures, taking into account safety, serviceability, and the various loads and environmental conditions that the structures may be subjected to.

**Describe the IS Guidelines for the following: i. Size of Aggregates ii. Use of water iii. Concrete on Seawater**

I. Size of Aggregates:

The size of aggregates used in concrete plays a crucial role in determining the final properties of the hardened concrete. The IS Guidelines for size of aggregates in concrete specify the maximum and minimum size limits for coarse and fine aggregates. Coarse aggregates should have a maximum size of 40mm and a minimum size of 4.75mm. On the other hand, fine aggregates should have a maximum size of 4.75mm and a minimum size of 150 microns.

II. Use of Water:

Water is an essential ingredient in the making of concrete. The IS Guidelines for the use of water in concrete specify the maximum amount of water that can be added to the concrete mix. This maximum limit is determined based on the type of cement used, the size and shape of aggregates, and the intended use of the concrete. In general, the maximum water-cement ratio should not exceed 0.5. This helps ensure that the concrete attains the desired strength and durability.

III. Concrete on Seawater:

The use of seawater as mixing water in concrete can have detrimental effects on the concrete’s strength and durability. The IS Guidelines for concrete on seawater specify that seawater should not be used as mixing water unless it is properly treated to remove the salt and other impurities. If seawater is used, the concrete should be designed to withstand the corrosive effects of salt, and special admixtures should be used to mitigate these effects. In general, the use of fresh water is recommended for making concrete.

**State the Stripping time for various types of formwork.**

Stripping time refers to the time elapsed between the completion of concrete placement and the removal of formwork. The stripping time is an important factor that affects the quality of the concrete surface and the overall strength of the structure. The IS Guidelines specify different stripping times for different types of formwork.

I. Timber formwork:

For timber formwork, the stripping time is usually between 18 to 24 hours. This is because timber formwork is relatively soft and flexible, and can cause surface distortions if removed too soon. It is important to wait until the concrete has gained enough strength to support itself before removing the formwork.

II. Steel formwork:

For steel formwork, the stripping time is usually between 6 to 12 hours. Steel formwork is rigid and can provide a smooth surface for the concrete, but it should still be removed before the concrete sets completely. If the formwork is removed too late, the concrete may start to shrink and crack, which can affect the overall strength of the structure.

III. Plastic formwork:

For plastic formwork, the stripping time is usually between 8 to 12 hours. Plastic formwork is lightweight and easy to remove, but it should still be left in place for a sufficient amount of time to allow the concrete to set. If the formwork is removed too soon, the concrete surface may be distorted, and the overall strength of the structure may be reduced.

In conclusion, the stripping time for different types of formwork depends on the type of material used, the size and shape of the concrete structure, and the desired quality of the concrete surface. The IS Guidelines provide general guidelines for stripping time, but the actual time may vary based on the specific conditions and requirements of each project.