Construction Materials

       CONSTRUCTION MATERIAL

                                         UNIT 01                                            

Geological Classification of Rocks

Rocks can be classified into three main types based on their formation process:

1. Igneous Rocks:

   • Formed from the solidification of molten magma or lava.
   • Classified into two subtypes:
     • Intrusive (Plutonic) Igneous Rocks: Formed beneath the Earth’s surface, with slow cooling. Examples include granite and diorite.
     • Extrusive (Volcanic) Igneous Rocks: Formed on the Earth’s surface, with rapid cooling. Examples include basalt and pumice.

2. Sedimentary Rocks:

   • Formed by the accumulation and compaction of sediments (particles of other rocks, minerals, or organic material).
   • Classified into three subtypes:
     • Clastic Sedimentary Rocks: Composed of fragments (clasts) of other rocks. Examples include sandstone, shale, and conglomerate.
     • Chemical Sedimentary Rocks: Formed from dissolved minerals that precipitate out of water. Examples include limestone and rock salt.
     • Organic Sedimentary Rocks: Derived from organic material (e.g., plant remains). Examples include coal and chalk.

3. Metamorphic Rocks:

   • Formed from the alteration of existing rocks due to heat, pressure, or chemical processes.
   • Classified based on their texture:
     • Foliated Metamorphic Rocks: Exhibit a layered or banded appearance due to alignment of mineral grains. Examples include slate, schist, and gneiss.
     • Non-foliated Metamorphic Rocks: Lack a layered structure. Examples include marble and quartzite.

Requirements of a Good Building Stone

When selecting a stone for construction purposes, certain qualities are essential:

1. Strength and Durability:

   • A good building stone should have sufficient strength to withstand loads and weathering.
   • Durability ensures that the stone remains intact over time.

2. Hardness:

   • Stones should be hard enough to resist abrasion, impact, and wear.
   • Hardness is measured using the Mohs scale (from 1 to 10).

3. Resistance to Weathering:

   • Stones exposed to the elements should resist weathering due to temperature changes, moisture, and chemical reactions.
   • Some stones, like limestone, are susceptible to weathering.

4. Appearance and Aesthetics:

   • Stones contribute to the visual appeal of a structure.
   • Factors include color, texture, and grain size.

5. Workability:

   • A good building stone should be easy to cut, shape, and dress.
   • Workability affects construction efficiency.

6. Availability and Cost:

   • Stones should be locally available to reduce transportation costs.
   • Cost-effectiveness is crucial.

General characteristics of stone

1. Texture: A good building stone should have a compact, fine crystalline structure that is free from cavities, cracks, or patches of soft or loose material. Stones with such texture tend to be strong and durable.

2. Durability: Durability is a critical factor. Various elements contribute to the durability of a stone:

   • Chemical Composition: The chemical composition of the stone affects its resistance to weathering and other influences.
   • Texture: The texture of the stone plays a role in its durability.
   • Resistance to Atmospheric Influences: Stones exposed to alternate conditions of heat and cold (due to temperature variations) and wetness and dryness (due to rain and sunshine) need to withstand these changes.
   • Location in Structure: The position of the stone within a structure also impacts its durability.

3. Density: Density refers to the weight of a stone relative to the density of water (1 gram per cubic centimeter). It affects the overall strength and stability of the stone.

4. Porosity: Porosity indicates the amount of open space between mineral grains in a stone. It generally dictates permeability—the ability of liquids to move through the stone. Stones with low porosity are less permeable and more durable².

5. Permeability: Permeability is crucial for assessing how liquids (such as water) can move through the stone. Stones with high permeability may be susceptible to water damage or staining.

6. Resistance to Fire and Electricity: While not always relevant for all applications, some stones exhibit better resistance to fire and electrical conductivity than others.

Quarrying of stones by wedging

1. What Is Wedging?

   • Wedging is a manual method used to split large stones or blocks from their natural bedrock or quarry face.
   • It involves creating a series of holes or channels in the stone using hand tools.
   • The principle behind wedging is to introduce a wedge (usually made of wood or metal) into these channels and then apply force to split the stone along its natural planes of weakness.

2. Steps in Wedging:

   • Drilling Holes: Quarry workers use handheld tools like chisels, picks, and hammers to drill holes into the stone. These holes are spaced evenly along the desired splitting line.
   • Inserting Wedges: Once the holes are drilled, wooden or metal wedges are inserted into them. The wedges are typically tapered to facilitate splitting.
   • Applying Force: Quarry workers then strike the wedges with hammers or mallets. The force applied causes the stone to crack along its natural cleavage planes.
   • Repeating the Process: The process is repeated, gradually widening the cracks until the stone splits into manageable pieces.

3. Factors Affecting Success:

   • Stone Properties: The success of wedging depends on the type of stone. Stones with natural planes of weakness (such as sedimentary rocks) are more amenable to this method.
   • Skill and Experience: Quarry workers need skill and experience to accurately place the holes and wedges for effective splitting.
   • Safety Measures: Safety precautions are essential to prevent accidents during the wedging process.

4. Advantages of Wedging:

   • Low Cost: Wedging is a cost-effective method compared to using explosives or machinery.
   • Precision: It allows precise control over the splitting process.
   • Environmentally Friendly: Unlike explosives, wedging does not cause vibrations or air pollution.

5. Limitations of Wedging:

• Time-Consuming: Wedging can be time-consuming, especially for large stones.
• Limited to Certain Stone Types: Not all stones can be effectively split using this method.
• Labor-Intensive: It requires manual labor and skilled workers.

Quarrying of stones by blasting

1. Drilling of Blast-Holes:

   • Quarry workers use specialized machinery to drill holes into the rock at specific intervals.
   • These blast-holes are strategically placed along the desired splitting lines within the rock mass.

2. Charging of Blast-Hole:

   • Explosives (such as dynamite) are carefully placed inside the drilled blast-holes.
   • The amount and type of explosive used depend on the rock type, size, and desired fragmentation.

3. Firing of the Shot:

   • Once the blast-holes are charged, the explosives are detonated.
   • The explosion fractures the rock along its natural planes of weakness, creating smaller, manageable pieces.
   • The broken stone resulting from the blast is typically of small size.

4. Advantages of Blasting:

   • Efficiency: Blasting allows for the rapid extraction of large quantities of stone.
   • Precision: Controlled blasting techniques minimize damage to the stone and surrounding environment.
   • Cost-Effectiveness: Blasting is often more cost-effective than manual methods.

5. Limitations of Blasting:

   • Safety Concerns: Quarrying operations involving explosives require strict safety protocols.
   • Environmental Impact: Blasting can cause vibrations and noise, affecting nearby areas.
   • Waste Management: Proper disposal of waste rock resulting from blasting is essential.

Deterioration of stones

Stone deterioration refers to the gradual changes that occur in natural or synthetic stone materials over time. These changes can result from various factors, leading to the weakening, loss of structural integrity, and altered appearance of the stone. Let’s explore some of the common causes of stone deterioration:

1. Weathering: Exposure to natural elements significantly affects stones. Elements such as wind, rain, and temperature fluctuations can cause physical and chemical breakdown of the stone surface.

2. Acid Rain: Acid rain can easily deteriorate the upper surface of the stone, leading to its degradation.

3. Biological Growth: The growth of biological elements like mosses, lichens, and other organic matter can penetrate the pores of the stone, causing structural damage.

4. Salt Damage: Salt crystallization and salt weathering can lead to the disintegration of the stone surface.

5. Freeze-Thaw Cycles: Repeated cycles of freezing and thawing cause the stone to expand and contract, resulting in cracking and weakening.

6. Pollution: Airborne sulfur dioxide and nitrogen oxides from pollution can accelerate stone deterioration.

7. Chemical Factors: Various chemicals used for cleaning stones can harm the upper surface of the stone.

8. Incorrect Cleaning Techniques: Improper cleaning methods, such as excessive pressure or abrasive cleaning, can physically damage the stone.

9. Poor Installation: Incorrect installation can create stress within the stone, affecting its durability.

10. Structural Settlement: When the foundation settles, it causes the stone to shift and crack.

11. Earthquakes: High-intensity earthquakes can break or crack stones.

12. Impact Damage: Physical impacts can also cause damage to the stone.

13. Vandalism: Deliberate acts of vandalism can harm stone surfaces.

14. Moisture Intrusion: Water infiltration can weaken the stone over time.

15. Corrosion of Metal Components: If stones are embedded with metal components (such as anchors or connectors), corrosion of these metals can affect the stone.

16. Differential Movement: Uneven settling or movement of adjacent materials can stress the stone.

17. Poor Maintenance: Neglecting proper maintenance can accelerate deterioration.

18. Aging: Over time, stones naturally age and may lose their original properties.

19. Atmospheric Deposition: Deposition of airborne particles (dust, pollutants) on the stone surface contributes to deterioration.

20. Construction Activities: During construction or renovation, stones may be subject to mechanical stress or damage.

Preservation of stones 

1. Factors Causing Deterioration of Stones:

   • Water and Chemicals: Pores present in the stone can fill up with water or chemicals, leading to deterioration.
   • Industrial Towns: Using stones containing carbonate of lime in industrial areas can accelerate decay.
   • Proximity of Different Stone Types: Laying limestone, sandstone, magnesium limestone, and granular limestone close to each other can cause mutual decay.
   • Adverse Binding Materials: The use of binding materials that negatively affect a particular stone impacts its durability.
   • Plant Growth: Plants and trees growing on stone surfaces contribute to deterioration.

2. Methods of Preservation:

   • Surface Coating: Coating the dry stone surface with paraffin, linseed oil, or light paint helps preserve it. However, this treatment is not permanent.
   • Frequent Washing: Regularly washing the stone surface with water and steam removes deposited dirt and salts, ensuring preservation.
   • Use of Preservatives: Sodium silicate (or potash) and calcium chloride are effective preservatives for washing stones.
   • Other Preservatives: Lead paint, coal tar, and Barium hydrate solution (in industrial towns) are also used for preservation. However, some materials may alter the stone’s natural color.

3. Characteristics of an Effective Preservative:

   • Easily applicable and penetrates into stone pores.
   • Remains effective after drying.
   • Economical and non-corrosive.
   • Prevents moisture penetration.
   • Does not develop objectionable colors.

4. Commonly Used Preservatives:

   • Coal Tar: Although effective, it produces an objectionable appearance when coated on the stone surface.
   • Other Options: Silicones, siliconates, and synthetic organic polymers are also used for preservation.

Properties of sand and uses

1. Physical Properties of Sand:

   • Moisture Content: Sand can be used as soon as it is obtained from the source. It typically contains a binding content (5-20%), water (5-8%), and a significant amount of organic matter.
   • Finishing on Natural Sand Moulds: Sand is suitable for finishing on natural sand molds.
   • Cost-Effectiveness: It is generally cheaper than most other sands.
   • Refractoriness: Sand has less refractoriness compared to other materials.

2. Common Uses of Sand:

   • Concrete Production: Sand is a key component in concrete, providing strength and stability.
   • Paving: Sand is used for road construction and pavement.
   • Glassmaking: Silica sand (quartz) is a primary raw material for glass production.
   • Water Filtration: Sand is used in water purification processes.
   • Agriculture: It is mixed with soil to improve aeration and drainage.
   • Landscaping: Sand enhances soil quality in gardens and parks.
   • Recreational Purposes: Sand is essential for creating beaches, sandpits, and golf bunkers.
   • Abrasives: Sand is used for smoothing surfaces.

Classification of coarse aggregate according to size

1. Coarse Aggregate:

   • Coarse aggregate refers to the larger-sized particles used in concrete and construction.
   • It plays a crucial role in providing strength and stability to concrete structures.

2. Nominal Maximum Size:

   • The nominal maximum size of coarse aggregate is the largest sieve size through which most of the aggregate particles pass.
   • For example, if an aggregate has a nominal maximum size of 20 mm, it means that most of the particles can pass through a 20 mm sieve.

3. Grading:

   • Grading refers to the distribution of aggregate particle sizes.
   • Proper grading ensures optimal packing and workability of concrete.
   • Different grading curves are used for specific applications.

4. Common Sizes:

   • Coarse aggregates are commonly available in sizes such as 40 mm, 20 mm, 16 mm, and 12.5 mm.
   • These sizes correspond to the sieve openings through which the aggregate particles are graded.

Structure of timber

1. Macrostructure:

   • The macrostructure refers to the visible components of timber that can be observed with the naked eye or at low magnification.
   • In a cross-section of a tree, several distinct layers can be identified:
     • Pith or Medulla: The central core of the tree.
     • Heartwood: Located toward the center, heartwood is darker and composed of xylem cells that are no longer active in the tree’s life processes.
     • Sapwood: Surrounding the heartwood, sapwood contains living xylem cells responsible for water transport.
     • Cambium Layer: A thin layer between the sapwood and bark, where cell division occurs.
     • Medullary Rays: Radial structures that transport nutrients horizontally across the tree rings.
     • Bark: The outer protective layer of the tree.

2. Microstructure:

   • The microstructure of wood involves examining its cellular composition at a microscopic level.
   • Wood forms around a central core (pith) in concentric layers called growth rings.
   • These growth rings consist of xylem cells, which play a vital role in water and nutrient transport.
   • Heartwood and sapwood are part of this intricate microstructure.

Timber’s unique structure contributes to its strength, durability, and versatility in construction. Whether it’s the visible macrostructure or the hidden microstructure, wood remains a remarkable material! 

General properties and uses of good timber

Certainly! Let’s explore the properties of good timber and its various uses:

1. Properties of Timber:

   • Colour: The color of timber varies from species to species. Light-colored timber may indicate weaker wood, while darker shades often signify stronger wood. For example, freshly cut teak has a golden yellow hue, deodar appears whitish, and walnut has a dark brown shade.
   • Appearance: Some timbers have characteristic aromas, which can help identify them. Freshly cut timbers often emit pleasant smells, such as the resinous scent from pine.
   • Hardness: Hardness is essential for resistance to damage.
   • Specific Gravity: Timber’s specific gravity ranges from 0.3 to 0.9. Light materials have a specific gravity less than water (less than 1), while compact woods with minimal pores can be heavier (specific gravity up to 1.5).
   • Moisture Content: Timbers are hygroscopic and absorb water from the atmosphere. High moisture content indicates lower timber quality and increases the risk of fungal attack.
   • Grain: The arrangement of vascular tissue (xylem and phloem) affects timber quality. Straight grain, where vascular tissue grows parallel to the timber’s length, is desirable.
   • Shrinkage and Swelling: Timber expands and contracts due to changes in moisture content.
   • Strength: Timber’s strength is crucial for its structural applications.
   • Density: Timber density varies based on its internal pores.
   • Toughness: Tough timber can withstand impact and wear.
   • Elasticity: Elasticity allows timber to bend without breaking.
   • Warping: Warping refers to deformation due to uneven drying or exposure to moisture.
   • Durability: Durable timber resists decay and insect attack.
   • Defectless: High-quality timber should be free from defects.
   • Workability: Timber should be easy to work with during construction.
   • Soundness: Sound timber is free from internal flaws.
   • Free of Abrasion: Timber surfaces should be smooth and free from abrasions.

2. Uses of Timber:

   • Construction: Timber is widely used in building structures, including framing, flooring, and roofing.
   • Furniture: Timber is a popular choice for making furniture.
   • Interior Finishing: Its warm texture and attractive appearance make it suitable for internal finishing.
   • Thermal Insulation: Timber provides good thermal insulation properties.
   • Engineering Applications: Timber’s tubular cell structure makes it useful for sound, electrical, and heat insulation.
   • Aesthetic Appeal: Timber is valued for its natural beauty and aesthetic appeal.
   • Sustainable Choice: Timber is renewable and can be replenished through proper forest management.

Different methods of seasoning for preservation of timber

1. Natural (Air) Seasoning:

   • In natural seasoning, timber is stacked in the open air.
   • The stacked timber allows free circulation of air around each part.
   • The process relies on evaporation to gradually reduce the moisture content.
   • Air seasoning is commonly used for softwoods and some hardwoods.
   • The duration of air seasoning depends on environmental conditions; favorable conditions may lead to weeks of seasoning, while unfavorable conditions may require a year or more.

2. Artificial (Kiln) Drying:

   • Kiln drying involves using specialized kilns or chambers to accelerate the drying process.
   • Timber is placed inside the kiln, and controlled heat and airflow are applied.
   • Kiln drying allows precise control over moisture removal.
   • It is faster than air seasoning and ensures uniform drying.
   • Kiln-dried timber is commonly used in construction, furniture making, and other applications.

 List various Defects in timber

Certainly! Timber, being a natural material, can exhibit various defects that affect its quality and suitability for different purposes. Let’s explore some common defects in timber:

1. Knots:

   • Description: Knots are the most common defects caused by natural forces during a tree’s growth. They occur when branches close to the ground or lower branches die, leaving their bases embedded in the tree.
   • Types:
     • Dead Knots: These are the remains of damaged branches that have dried out and become loose, eventually falling out.
     • Live Knots: Live knots are sound and firm. If small, they may not significantly affect the timber’s strength.
   • Impact: Knots decrease the strength of wood, especially when the load is perpendicular to the grain.

2. Twist:

   • Description: Twist in timber occurs when the ends of the timber rotate in opposite directions. It results from the twisting of trees due to strong winds during growth.
   • Impact: Twisted timber can be challenging to work with and affects its appearance.

3. Shakes:

   • Description: Shakes are cracks or splits in the wood that occur around the annual or growth rings of timber.
   • Types:
     • Star Shakes: These propagate from the bark toward the sapwood (and sometimes heartwood) along the lines of medullary rays. Extreme heat or frost during tree growth and rapid or uneven seasoning cause star shakes.
     • Cup and Ring Shakes: Cup shakes follow the annual growth ring and can partially or completely separate the rings. When the crack fully separates the annual ring, it’s called a ring shake.
   • Impact: Shakes may or may not be a structural problem but can affect aesthetics, especially where appearance matters.

4. Cross Grain:

   • Description: Cross grain occurs when the fibers of wood run diagonally across the grain direction. It weakens the timber.
   • Impact: Cross-grained timber is less stable and prone to splitting.

5. Crookedness:

   • Description: Crooked timber has irregular or bent shapes due to the tree’s growth pattern.
   • Impact: Crooked timber is challenging to use in construction and affects aesthetics.

6. Rind Galls:

   • Description: Rind galls are irregular swellings or distortions on the tree’s bark.
   • Impact: They don’t directly affect the timber’s strength but can indicate internal defects.

7. Burr:

   • Description: Burr results from abnormal growths on the tree, often near the roots or branches.
   • Impact: Burr wood is highly figured and prized for decorative purposes but can be difficult to work with.

8. Curl:

   • Description: Curl refers to the wavy or twisted grain pattern in timber.
   • Impact: Curly timber is valued for its appearance in fine woodworking and veneers.

Use of bamboo in construction

1. Structural Frameworks:

   • Bamboo is often used in structural frameworks for walls, partitions, posts, trusses, and beams.
   • It provides a lightweight yet strong alternative to traditional materials like wood or steel.
   • Bamboo’s high strength-to-weight ratio makes it suitable for supporting loads in low-rise houses and other structures.

2. Flooring and Ceilings:

   • Bamboo flooring is commonly used in modern construction.
   • It offers durability, aesthetics, and environmental sustainability.
   • Bamboo can also be found in ceilings, adding a natural touch to interior spaces.

3. Bridges and Footbridges:

   • Bamboo is used to build footbridges in various regions.
   • Its flexibility and strength allow for the construction of sturdy and cost-effective pedestrian bridges.
   • These bridges are especially common in rural areas where bamboo is abundant.

4. Temporary Structures:

   • Bamboo is ideal for creating temporary structures such as shelters, pavilions, and event spaces.
   • Its rapid growth and renewability make it a sustainable choice for short-term projects.

5. Decorative Elements:

   • In Japanese architecture, bamboo is used decoratively in elements like fencing, fountains, grates, and gutters.
   • Its ready availability and aesthetic appeal contribute to its use in these applications.

6. Scaffolding:

   • Bamboo scaffolding has been historically used in construction.
   • While banned in China for buildings over six stories, it is still widely used in Hong Kong for skyscrapers.
   • Bamboo scaffolding can reach impressive heights and provides a safe working platform for construction workers.

Asphalt-properties and uses 

1. Properties of Asphalt:

   • Composition: Asphalt is a black or brown petroleum-like material composed of compounds of hydrogen and carbon, with minor proportions of nitrogen, sulfur, and oxygen.
   • Consistency: It varies from a viscous liquid to a glassy solid.
   • Sources: Asphalt can be obtained as a residue from petroleum distillation or from natural deposits.
   • Characteristics: It softens when heated and is elastic under certain conditions.
   • Mechanical Properties: While its mechanical properties are of little significance, asphalt serves as a binder or adhesive in various applications.

2. Uses of Asphalt:

   • Road Surfacing: The principal application of asphalt is in road surfacing. It provides a durable, flexible, and wear-resistant pavement.
   • Roofs: Asphalt is used for roofing materials, providing waterproofing and protection.
   • Sidewalks and Parking Lots: It is commonly used for sidewalks, parking lots, and other paved areas.
   • Canal and Reservoir Linings: Asphalt lines canals, reservoirs, and dam facings.
   • Harbour and Sea Works: Thinner asphalt membranes protect against weathering, while thicker surfaces may include crushed rock (riprap).
   • Building Construction: Asphalt is used for coatings, floor tiles, soundproofing, and waterproofing.
   • Industrial Products: It finds applications in batteries and other industrial products.
   • Emulsions: Asphaltic emulsions, where fine globules of asphalt are suspended in water, are also prepared for specific uses.