Classification and Properties of Building Materials

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Useful for students of B.E. or B. Tech. Second Year. This ppt includes comprehensive info on properties, classification and selection criteria of Building materials

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BUILDING MATERIALS & CONSTRUCTION Unit -1: Classification of materials, their performance and economics: 

BUILDING MATERIALS & CONSTRUCTION Unit -1: Classification of materials, their performance and economics By Nauras Saiyed Asst. Professor Department of Civil Engineering

Civil Engineering : 

Civil Engineering Civil Engineering consists of Design Construction Maintenance Inspection Management of characteristically different/diverse public work projects from rail, roads, bridges to high rise buildings to sewage treatment plants, etc.

PowerPoint Presentation: 

At the core of civil engineering rests the investigation of materials and methods that can facilitate construction. In order to choose the most appropriate and economic material, an engineer must have comprehensive knowledge of properties and manufacturing processes of various engineering materials

Material: 

Material A material is defined as a substance or thing from which something else can be made. The materials which are used for the construction purpose are called building materials Natural : clay, rocks, sand, wood, etc. Man made: Concrete, glass, bricks, plastic, etc.

Others:: 

Others: Thermal Acoustic Optical Magnetic Electrical three major headings: Physical Mechanical Chemical Properties of Materials:

Physical Properties: 

Physical Properties Density Bulk Density Chemical Resistance Coefficient of softening Density Index Durability Fire Resistance Frost Resistance Hygroscopicity Porosity Refractoriness Spalling Resistance Specific heat Thermal Capacity Thermal Conductivity Water Absorption Water Permeability Weathering Resistance

PowerPoint Presentation: 

The next few slides discuss a few of the physical properties listed in the previous slide.

Density: 

Density Take a look at the two boxes below. Each box has the same volume. If each ball has the same mass, which box would weigh more? Why?

PowerPoint Presentation: 

The box that has more balls has more mass per unit of volume. This property of matter is called density. The density of a material helps to distinguish it from other materials. Since mass is usually expressed in grams and volume in cubic centimeters, density is expressed in grams/cubic centimeter.

Bulk Density: 

Bulk Density Bulk density is a property of powders, granules and other "divided" solids Especially used in reference to soil and gravel It is defined as the mass of many particles of the material divided by the total volume they occupy. The total volume includes particle volume, inter-particle void volume and internal pore volume. Bulk density is not an intrinsic property of a material; it can change depending on how the material is handled

PowerPoint Presentation: 

For example, a powder poured in to a cylinder will have a particular bulk density; if the cylinder is disturbed, the powder particles will move and usually settle closer together, resulting in a higher bulk density. For this reason, the bulk density of powders is usually reported both as "freely settled" (or "poured" density) and "tapped" density (where the tapped density refers to the bulk density of the powder after a specified compaction process, usually involving vibration of the container.)

Eg. Bulk Density of Soil : 

Eg . Bulk Density of Soil Soil weight is most often expressed on a soil volume basis rather than on a particle basis. Bulk density is defined as the dry weight of soil per unit volume of soil. Bulk density considers both the solids and the pore space; whereas, particle density considers only the mineral solids.

Illustration of bulk density and particle density: 

Illustration of bulk density and particle density

Density Index: 

Density Index The ratio of bulk density of a material to its density is known as its density index. It denotes the degree to which its volume is filled up with solid matter. As there are practically no dense substances in nature, the density index of most of the building materials is less than unity.

Hygroscopicity: 

Hygroscopicity Hygroscopy is the ability of a substance to attract and hold water molecules from the surrounding environment. This is achieved through either absorption or adsorption with the absorbing or adsorbing material becoming physically 'changed' somewhat, by an increase in volume, stickiness, or other physical characteristic of the material, as water molecules become 'suspended' between the material's molecules in the process.

Problems in construction due to Hygroscopicity: 

Nitrate and chloride salts (usually found in building structures) are hygroscopic, causing them to retain moisture and absorb additional moisture at times of high humidity. Nitrate and chloride salts most commonly originate in the ground. Their presence in plasterwork is usually an indication of rising damp, lateral penetrating damp or flood damage. Coastal properties may suffer from chloride salt contamination due to the salt water carried in the air Problems in construction due to Hygroscopicity

Problems in construction due to Hygroscopicity: 

Problems in construction due to Hygroscopicity It is important when re-plastering a wall affected by salts that careful consideration is given to the type of plaster used. The water content of new plaster encourages salts to migrate from the underlying wall structure to the new plaster resulting in further problems. Chemicals are available to neutralize problematic salts before re-plastering work is undertaken.

Mechanical Properties : 

Mechanical Properties Abrasion Creep Elasticity Fatigue Hardness Impact Strength Plasticity & brittleness Strength Wear

Mechanical properties of a few building materials: 

Mechanical properties of a few building materials Hardness of diamond Ductility of copper Elastic behaviour of rubber Cement and bricks – strong in compression Wood and steel – strong in tension

Chemical Properties: 

Chemical Properties The chemical properties suggest the tendency of a material to combine with other substances, its reactivity, solubility and effects like corrosion, chemical composition, acidity, alkalinity, etc.

Pictures showing rusting/corrosion : 

Pictures showing rusting/corrosion

Thermal Properties: 

Thermal Properties These represent the behaviour of a material under heat and temperature. Eg .: coefficient of thermal expansion of concrete is fundamental in assessing the expansion potential of concrete slabs.

Thermal Expansion of railroad track due to excessive heating.: 

Thermal Expansion of railroad track due to excessive heating.

Typical expansion joint on a steel span bridge.: 

Typical expansion joint on a steel span bridge.

Acoustical Properties: 

Acoustical Properties Architectural acoustics deals with the construction of enclosed areas so as to enhance the hearing of speech or music. Properties such as sound transmission and sound reflection are critical in choosing materials that should offer sound resistance.

Noise S.T.O.P Acoustic-Board: 

Noise S.T.O.P Acoustic-Board Characteristic features Sound Deadening Sound Absorbing Insulating Low Cost

Acoustic Panel Foam: 

Acoustic Panel Foam Characteristic features High Performance Absorber Increased Absorptive Surface Area Fiber Free Class A Fire Retardant

Absorptive/Noise Barrier Quilted Curtains : 

Absorptive/Noise Barrier Quilted Curtains Characteristic features Cost Effective Room Dividers Water & Chemical Resistant Exterior Applications

Doubly-ruled surfaces : 

Doubly-ruled surfaces The acoustic performance of a surface can be modified through geometry of material Such materials have sound scattering / sound diffusive acoustic properties

Optical Properties: 

Optical Properties When light strikes any material, it interacts with its atoms and causes various types of effects. The light may be either reflected, refracted, scattered or absorbed. The study of light in materials and how to use this behavior to control the various light effects is called OPTICS. Optical properties such as color, light transmission and light reflection are considered while selection for construction purposes.

Skylights and domes: 

Skylights and domes

Glass Block Shower Window with Colored Glass Blocks: 

Glass Block Shower Window with Colored Glass Blocks

Skylight Shade Covers and tint reduce heat & glare: 

Skylight Shade Covers and tint reduce heat & glare

Classification of Building materials: 

Classification of Building materials Broadly classified in the following three groups: Cement Materials Eg .: Lime, cement, mortar, etc. Protective Materials Eg .: Paints, varnishes, plaster, etc. Solid Materials Stones, bricks, iron, timber, etc.

Selection of materials: 

Selection of materials The selection criteria are: Strength Durability Appearance Availability and Manufacturability Economic /Cost effective Environment friendly

Strength: 

Strength The material should be able to carry the design loads. It should have adequate strength to resist failure under the action of stresses caused by load

Strength: 

Strength Examples Concrete used as foundation slab should be able to carry the load from the superstructure and pass it on to the ground below safely and without causing settlement. A wooden beam supporting timber floor should be strong enough to transfer the floor loads to the supporting walls

Strength is a generic term: 

Strength is a generic term It means different things in different applications. Timber used as a floor joist must command high bending strength. But when used as a pile it must have significant compressive strength.

PowerPoint Presentation: 

Timber floor joists require high bending strength

PowerPoint Presentation: 

Timber acting in compression when used as piles in foundation

Durability: 

Durability The material should satisfy serviceability requirements such as Deformation limits Durability aspects Constraints on performance Adaptability Serviceability implies satisfactory performance at all times Recorded data on past performance, laboratory test results and established practices will help assess the serviceability of materials

Serviceability example: 

Serviceability example A material whose surface is slick and slippery when moist is a poor choice for paving roads A road surface needs materials that show little movement under the impact of loads, are water resistant and are easy to repair.

Appearance: 

Appearance Most nonstructural materials such as floor coverings, paints, doors, windows, etc. are chosen based on aesthetic considerations. The same is considered for some structural materials as well. A concrete wall may be given different finishes depending on aesthetic appeal. The masonry of buildings can be chosen to suitably match the ambient architecture

PowerPoint Presentation: 

Different Concrete finishes Broom Finish Wooden Trowel Finish Exposed aggregate /Stone Finish Sand Blast Finish

PowerPoint Presentation: 

Different masonry finishes Brick masonry Architectural Bricks Walkway Brick Clad Panels Brick Veneer Rock Veneer

Availability/Manufacturability: 

Availability/Manufacturability Availability and manufacturability requirements are often unseen limiting factors in materials selection. The importance of a material being available is obvious. Materials which are not available cannot be used. The importance of processibility is not always so obvious. Any other desirable qualities are useless if a material cannot be processed into the shape required to perform its function. Most engineering materials in use today have well known substitutes which would perform better and often at lower cost but processes for forming, cutting, machining, joining, etc. are not available or commercially viable. There is often a period of time after a new material is introduced during which its application is severely limited while processing techniques are developed which facilitate its use.

Environment Friendly: 

Environment Friendly Building materials typically considered to be 'green' include rapidly renewable plant materials like bamboo and straw, dimension stone, recycled stone, recycled metal, other products that are non-toxic, reusable, renewable, and/or recyclable e.g., sheep wool, panels made from paper flakes, compressed earth block, baked earth, rammed earth, clay, cork, coconut, wood fibre plates, calcium sand stone, concrete (high and ultra high performance, roman self-healing concrete

Environment Friendly Building Materials: 

Environment Friendly Building Materials Strawbale house Bamboo shed

Environment Friendly Building Materials: 

Environment Friendly Building Materials ADOBE is a very practical and resource efficient building method for dry hot climates Climates where the passive cooling traits of adobe can be most beneficial. Adobe is a natural building material made from sand, clay, water, and some kind of fibrous or organic material (sticks, straw, and/or manure), which the builders shape into bricks using frames and dry in the sun. Adobe buildings are similar to cob and mudbrick buildings.

Environment Friendly Building Materials: 

Environment Friendly Building Materials Cob is a very old method of building with earth and straw or other fibers.

Environment Friendly Building Materials: 

Environment Friendly Building Materials It may be hard to believe that a paver this extraordinary is recycled, but it is. Recycled granite pavers provide a durable and beautiful alternative to concrete or asphalt for patios, walkways, driveways, fountains...even streets.

Environment Friendly Building Materials: 

Environment Friendly Building Materials Dimension stone is any type of natural rock material that is quarried in order to make blocks or slabs of rock that are cut to specific sizes (width, length, and thickness) and shapes. Dimension stone is used because it is durable, strong and attractive. Portland block stone

Cost: 

Cost Cost/economic restraint is one of the key factors governing the choice of material. For example, Timber construction is cheaper in United States but prohibitively expensive in many other countries.

Cost: 

Cost A material’s cost is also generally a limiting factor. While cost is universally recognized and perhaps the easiest of all properties to understand there are specific cost considerations for materials selection. Just as materials and their processing go hand in hand so do material costs and processing costs. Understanding the entire processing sequence is critical to accurately evaluating the true cost of a material.

Standardization: 

Standardization When we use a construction material in any civil engg . Project, a number of questions come up: For Example: If we are designing a concrete footing to anchor, the questions may include: What is concrete? What are the proportions of concrete ingredients? What type of aggregate should be used? How much water should be added while mixing? What procedures should be followed after placing the concrete?

Standardization: 

Standardization For knowing answers one should be proficient in all aspects of concrete construction: Understanding of cement chemistry Hydration process Geology Concrete behaviour Thermal effects

Standardization: 

Standardization But the even then there are chances of failure due to : Bad quality of cement Weak aggregates Contaminated sand To guarantee satisfactory performance from materials they should manufactured to satisfy minimum quality and product standards.

Standardization: 

Standardization To guarantee satisfactory performance from materials they should manufactured to satisfy minimum quality and product standards. In addition, the methods of use or construction should follow standard procedures Thus, standardization is necessary to improve quality and establish uniformity. For this purpose various standards have been established for materials, testing and inspection.

THANKS: 

THANKS

Breathability / Vapor Permeability: 

Breathability / Vapor Permeability Vapor permeability (often called breathability) is a material’s ability to allow water vapors to pass through. Vapor permeability is important because wall cavities do get wet, roofs leak, rain water can infiltrate behind the exterior cladding, condensation occurs, plumbing leaks, construction materials are often installed wet or can get wet during construction, etc. Regardless of how it happens, moisture intrusion does occur and requires a way to dry out; vapor permeable layers will allow moisture to dry out through water vapor diffusion. When a wall can’t dry or drying rates are too slow, it becomes vulnerable to moisture-induced damage including mold, corrosion and rot. The ability of wall assemblies to dry is vitally important in the design and construction of durable walls. The fibrous structure of vapour permeable underlays is sufficiently dense to prevent liquid water from penetrating; while allowing water vapour to diffuse.

Permeability : 

Permeability Breathability in buildings is not really about air. It is about water: water as a gas and water as a liquid; water inside the building, water outside the building, and water in the walls, floors and roofs themselves (though not about water in pipes!). It is not only about how water moves through structures (water vapour permeability), but also about the ability of materials to absorb and release water as vapour ( hygroscopicity ) and about the ability of materials to absorb and release water as liquid (capillarity). Breathability is the key to Building Performance