GENERAL ENGINEERING-CIVIL ENGINEERING NOTES

JHARKHAND MINING INSPECTOR GENERAL ENGINEERING-CIVIL ENGINEERING NOTES

Building Materials

Physical and Chemical properties

Physical properties of building material are the qualities that can be assessed without applying any external force. They include:

- Bulk density: The mass-to-volume ratio of a material in its natural state, including voids and pores. It affects the strength, heat conductivity, and durability of the material. For example, the bulk density of bricks is  500 -  800 kg/m3.

- Porosity: The proportion of pore volume to material volume. It influences the heat conductivity, strength, bulk density, and durability of the material. For example, granite has a low porosity and high strength.

- Durability: The ability of a material to withstand the combined action of atmospheric and other conditions. It determines the life span and maintenance cost of the material. For example, steel is durable but prone to corrosion.

- Density: The mass-to-volume ratio of a material in its homogeneous state. It affects almost all the physical properties of the material. For example, steel has a high density of 7850 kg/m3¹.

- Fire resistance: The ability of a material to resist fire or high temperatures without losing its structural integrity. It depends on the chemical composition and thermal conductivity of the material. For example, concrete is fire resistant but wood is not.

- Frost resistance: The ability of a material to resist freezing and thawing cycles without cracking or deteriorating. It depends on the water absorption and porosity of the material. For example, bricks are frost resistant but asphalt is not.

- Weathering resistance: The ability of a material to resist natural agents such as rain, wind, sun, etc. without losing its appearance or quality. It depends on the chemical stability and surface protection of the material. For example, stone is weather resistant but timber is not.

- Spalling resistance: The ability of a material to resist breaking or cracking due to thermal stress or mechanical shock. It depends on the thermal expansion and elasticity of the material. For example, glass is spalling resistant but concrete is not.

- Water absorption: The amount of water that a material can absorb when immersed or exposed to moisture. It affects the porosity, durability, and frost resistance of the material. For example, sand has a high water absorption but steel has a low water absorption.

- Water permeability: The rate at which water can pass through a material under a pressure gradient. It affects the durability and corrosion resistance of the material. For example, concrete has a low water permeability but wood has a high water permeability.

- Hygroscopicity: The ability of a material to absorb or release moisture from the air depending on the relative humidity. It affects the dimensional stability and strength of the material. For example, timber is hygroscopic but steel is not.

- Coefficient of softening: The ratio of compressive strength of a material before and after soaking in water for a specified time. It indicates the loss of strength due to water absorption. For example, lime has a low coefficient of softening but cement has a high coefficient of softening.

- Refractoriness: The ability of a material to withstand high temperatures without melting or deforming. It depends on the melting point and atomic bonding of the material. For example, fire clay has a high refractoriness but asphalt has a low refractoriness.

Chemical properties of building material are the qualities that depend on the chemical composition and reactions of the material with other substances. They include:

- Atomic bonding: The type and strength of connections that hold the atoms of the material together. It affects the melting point, boiling point, thermal conductivity, and electrical conductivity of the material. For example, metallic bonding in steel gives it high thermal and electrical conductivity.

- Corrosion resistance: The ability of a material to resist chemical or electrochemical attack by the environment on its surface or interior. It depends on the reactivity and protective coating of the material. For example, stainless steel is corrosion resistant but iron is not.

- Acidity or alkalinity: The measure of hydrogen ion concentration in a solution formed by dissolving a material in water. It affects the compatibility and reaction rate of the material with other substances. For example, cement is alkaline but lime is acidic.

- Oxidation: The process of losing electrons by a material when exposed to oxygen or other oxidizing agents. It affects the color, strength, and corrosion resistance of the material. For example, iron oxide (rust) forms when iron oxidizes and loses its strength and resistance.

- Hydration: The process of combining water molecules with a material to form a new compound. It affects the setting, hardening, and strength of the material. For example, cement hydrates when mixed with water and forms a hard and strong mass.

- Carbonation: The process of reacting carbon dioxide with a material to form a carbonate compound. It affects the pH, durability, and corrosion resistance of the material. For example, concrete carbonates when exposed to air and loses its alkalinity and protection for steel reinforcement.

- Sulfate attack: The process of reacting sulfate ions with a material to form a sulfate compound. It affects the volume, strength, and durability of the material. For example, concrete suffers from sulfate attack when exposed to seawater or soil and expands and cracks.

- Efflorescence: The process of depositing salt crystals on the surface of a material when water evaporates. It affects the appearance, porosity, and durability of the material. For example, brickwork shows efflorescence when soluble salts are present in the bricks or mortar.

 Classification

Classification of building material is the process of grouping materials based on their source, composition, sustainability, or use. It helps to understand the properties, applications, and availability of different materials for construction purposes. The following are some common criteria for classification of building material:

- Classification based on source: This criterion divides materials into natural or synthetic based on their origin. Natural materials are those that are obtained from nature with little or no processing, such as wood, stone, sand, etc. Synthetic materials are those that are manufactured from raw materials through physical or chemical processes, such as steel, cement, plastic, etc.

- Classification based on composition: This criterion divides materials into organic or inorganic based on their chemical components. Organic materials are those that contain carbon and hydrogen atoms, such as wood, paper, rubber, etc. Inorganic materials are those that do not contain carbon and hydrogen atoms, such as metals, ceramics, glass, etc.

- Classification based on sustainability: This criterion divides materials into eco-friendly or non-eco-friendly based on their environmental impact. Eco-friendly materials are those that are renewable, biodegradable, recyclable, or have low carbon footprint, such as bamboo, straw, hempcrete, etc. Non-eco-friendly materials are those that are non-renewable, non-biodegradable, non-recyclable, or have high carbon footprint, such as concrete, plastic, asbestos, etc.

- Classification based on use: This criterion divides materials into functional or structural based on their role in construction. Functional materials are those that provide specific functions such as insulation, waterproofing, fire resistance, etc., such as paint, varnish, bitumen, etc. Structural materials are those that provide strength and stability to the structure such as beams, columns, slabs, etc., such as steel, concrete, brick, etc.

standard tests

Standard tests of building material are the procedures used to determine the properties and quality of different materials used in construction. They are based on certain codes and standards developed by various organizations such as ASTM, BIS, RDSO, etc. They help to ensure the safety, durability, and performance of the materials and the structures built with them. The following are some common standard tests of building material:

- Tests for aggregates: Aggregates are granular materials such as sand, gravel, crushed stone, etc., that are used as filler or reinforcement in concrete and other construction materials. Some of the standard tests for aggregates are:

  - Aggregate crushing value (ACV): This test measures the resistance of aggregate to crushing under a gradually applied compressive load. It is expressed as a percentage of the crushed material to the total weight of the aggregate. The lower the ACV, the stronger the aggregate. The test is done as per IS 2386 - Part 4 and IS 383.

  - Aggregate impact value (AIV): This test measures the resistance of aggregate to sudden impact or shock. It is expressed as a percentage of the broken material to the total weight of the aggregate. The lower the AIV, the tougher the aggregate. The test is done as per IS 2386 - Part 4.

  - Aggregate abrasion value (AAV): This test measures the resistance of aggregate to wear and tear due to friction or rubbing. It is expressed as a percentage of the weight loss of the aggregate to its original weight. The lower the AAV, the more durable the aggregate. The test is done as per IS 2386 - Part 4.

  - Flakiness index (FI): This test measures the percentage of flat or elongated particles in an aggregate sample. It is calculated by passing the aggregate through a set of sieves with specified dimensions and counting the number of particles retained on each sieve. The higher the FI, the more flaky the aggregate. The test is done as per IS 2386 - Part  .

  - Elongation index (EI): This test measures the percentage of elongated particles in an aggregate sample. It is calculated by passing the aggregate through a set of sieves with specified dimensions and counting the number of particles retained on each sieve. The higher the EI, the more elongated the aggregate. The test is done as per IS 2386 - Part  .

  - Specific gravity and water absorption: These tests measure the ratio of weight of aggregate to weight of water and the percentage of water absorbed by aggregate when immersed in water for a specified time respectively. They indicate the density and porosity of aggregate. The higher the specific gravity, the denser the aggregate. The lower the water absorption, the less porous the aggregate. The tests are done as per IS 2386 - Part 3.

- Tests for cement: Cement is a binding material that sets and hardens when mixed with water and other ingredients. It is used in concrete and mortar for various construction purposes. Some of the standard tests for cement are:

  - Fineness: This test measures the particle size distribution of cement by sieving it through a standard sieve. It indicates the surface area and hydration rate of cement. The finer the cement, the higher its surface area and hydration rate. The test is done as per IS 403  (Part  ) -  996.

  - Consistency: This test measures the amount of water required to form a paste of standard consistency with cement. It indicates the workability and setting time of cement paste. The higher

the consistency, the more water required and vice versa. The test is done as per IS 403  (Part 4) -  988.

  - Setting time: This test measures the time required for cement paste to lose its plasticity and gain strength when mixed with water. It indicates the hardening rate and workability period of cement paste. The setting time consists of two stages: initial setting time and final setting time. The initial setting time is when the paste starts to stiffen and lose its shape retention ability. The final setting time is when the paste becomes rigid and can resist certain pressure without deformation. The test is done as per IS 403  (Part 5) -  988.

  - Soundness: This test measures the ability of cement to retain its volume after setting and hardening. It indicates the presence of free lime or magnesia in cement, which can cause expansion and cracking of cement paste. The soundness of cement is tested by two methods: Le-Chatelier method and autoclave method. The Le-Chatelier method uses a small mould with two indicators to measure the expansion of cement paste when immersed in water. The autoclave method uses a high-pressure steam chamber to measure the expansion of cement paste when subjected to high temperature and pressure. The test is done as per IS 403  (Part 3) -  988.

  - Compressive strength: This test measures the resistance of cement paste or mortar to crushing under a gradually applied compressive load. It indicates the quality and strength of cement. The compressive strength of cement is tested by two methods: cube method and cylinder method. The cube method uses a standard cube mould of 70.6 mm size to prepare and test the specimens. The cylinder method uses a standard cylinder mould of  50 mm diameter and 300 mm height to prepare and test the specimens. The test is done as per IS 403  (Part 6) -  988.

  - Slump test: This test measures the workability or consistency of fresh concrete by measuring the vertical settlement of a cone-shaped mould filled with concrete when lifted. It indicates the ease of placing, compacting, and finishing of concrete. The higher the slump, the more workable the concrete. The test is done as per IS   99 -  959.

  - Compaction factor test: This test measures the workability or consistency of fresh concrete by measuring the ratio of weight of partially compacted concrete to weight of fully compacted concrete in a standard apparatus. It indicates the degree of compaction required for concrete. The higher the compaction factor, the less workable the concrete. The test is done as per IS   99 -  959.

  - Vee-bee consistometer test: This test measures the workability or consistency of fresh concrete by measuring the time required for a vibrating table to remould a cone-shaped mass of concrete into a cylindrical shape. It indicates the cohesiveness and mobility of concrete. The lower the vee-bee time, the more workable the concrete. The test is done as per IS   99 -  959.

  - Compressive strength test: This test measures the resistance of hardened concrete to crushing under a gradually applied compressive load. It indicates the quality and strength of concrete. The compressive strength of concrete is tested by using standard cube or cylinder specimens cured for different periods and loaded in a compression testing machine. The test is done as per IS 5 6 -  959.

  - Flexural strength test: This test measures the resistance of hardened concrete to bending under a gradually applied load. It indicates the modulus of rupture or tensile strength of concrete. The flexural strength of concrete is tested by using standard prism specimens cured for different periods and loaded in a flexure testing machine. The test is done as per IS 5 6 -  959.

  - Split tensile strength test: This test measures the resistance of hardened concrete to splitting under a gradually applied compressive load along its diameter. It indicates the tensile strength or cracking resistance of concrete. The split tensile strength of concrete is tested by using standard cylinder specimens cured for different periods and loaded in a compression testing machine with two strips along its length. The test is done as per IS 58 6 -  999.

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