Mechanical properties of building materials

All the building structures are developed with various types of materials. These materials are either known as building materials or materials of construction. The cost of material in a building varies from 30 to 50 percent of entire building cost.

Given below, the detail mechanical properties of materials :-

Strength:

a. Strength is defined as the strength of material to resist the load.
b. Strength of materials – Capacity to resist an applied stress devoid of failure.
c. Compressive strength – Capacity to resist axially directed pushing forces.
d. Tensile strength – Highest stress at the time of being expanded or dragged prior to necking.
e. Shear strength – The capacity to resist shearing.
f. Elasticity – In a material if exterior load is employed it experiences deformation and on elimination of the load, it gets back to it’s actual shape.

Plasticity: If a material fails to retrieve it’s actual shape while eliminating the exterior load, it is defined as plastic materials.

Ductility: When a material experiences a significant deformation devoid of rupture, it is known as ductile materials.

It experiences a large deformation throughout tensile test. It is considered as the most perfect material for tension member. Steel, copper, wrought iron, aluminum alloys belong to ductile materials.

Elongation is in excess of 15%

Brittleness:

a. If a material can’t experience any deformation if some external force functions on it and it collapses with rupture.
b. Brittleness means powerful in compression and poorer in tension.
c. Brittleness is found in C.I, glass, concrete, bricks etc.
d. Elongation remains under 5%

Malleability: Malleability is the capability of a material to distort under pressure (compressive stress). After being malleable, a material is flattened into thin sheets through hammering or rolling. Several metals with high malleability also contain high ductility.

Malleable materials are gold, silver, copper, aluminum, tin, lead steel etc.

Toughness: Toughness means the capability of a material to consume energy prior to rupture is known as toughness.

Toughness is found in mild steel, wrought iron etc.

Hardness: Hardness means the resistance of materials against abrasion, indentation, wear and scratches.

C.I is stronger material.

Stiffness: Stiffness refers to force that is necessary to create unit deformation in a material.

Creep: Creep means inelastic deformation because of sustained load.

Physical properties of materials

Bulk density = ρ = M/V
Water absorption
Permeability
Stability

Specific gravity (G): Mass of solids of specified volume / Mass of equal volume distilled water

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Published By
Rajib Dey
www.constructioncost.co
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Method of constructing post tension RCC slab

In this construction video tutorial, you will learn how post tension RCC slabs are built up as well as how post tensioning is performed and benefits of post tensioning process.

POST TENSION SLAB: It refers to the slab that is tensioned as soon as the slab is developed. Reinforcement is arranged to avoid the compression.

In Post tension slab, cables or steel tendons are utilized to substitute the reinforcement. Post-tensioning offers a solution to get rid of the natural weakness of concrete in tension as well as optimize its strength in compression.

In concrete structures, this is obtained by arranging high-tensile steel tendons/cables in the element prior to start the casting. If the concrete attains the required strength, the tendons are pulled with special hydraulic jacks and retained in tension with specially designed anchorages which are attached at each end of the tendon.

It creates compression at the edge of the structural member that increases the strength of the concrete for resisting tension stresses.

If tendons are correctly curved to a specific profile, they will exert, other than compression at the perimeter, a useful ascendant set of forces (load balancing forces) that will neutralize applied loads, alleviating the structure from a portion of gravity effects.

In this type of concrete slab, cables are affixed in place of reinforcement. In Steel reinforcement the gapping among bars is 4inch to 6inch while in Post tension slab the gapping is in excess of 2m.

Go through the following video tutorial, to get more details on post tension slab.

Video Source: F&U-FORYOU

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Published By
Rajib Dey
www.constructioncost.co
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How soil cement is used in earthfill dams & embankments

Now-a-days soil cement as a facing material for earthfill dams is considered very cost-effective where proper riprap is unavailable near the site.

A fairly rigid foundation is suitable in order that deformation after disposition of soil-cement is not vital; however, no uncommon design features should be integrated into the embankment.

Normal embankment construction methods are followed, with perhaps proper precaution to make sure a minimum of embankment consolidation and foundation settlement once the construction is completed.

The soil-cement is normally arranged and compacted in stair-step horizontal layers. It provides greater construction efficiency and operational potency. With standard embankment slopes of 2:1 and 4:1, a horizontal layer with 8 feet width will set least protective thicknesses of about 2 and 3l/2 feet correspondingly, measured normal to the slope.

It starts at the lowest layer of soil-cement, each subsequent layer is stepped back a distance equivalent to the product of the compacted layer thickness in feet times the embankment slope.

As for instance, if the compacted thickness is 6 inches and the slope is 2:1, the step back is = 0.5(2) = 1 foot. The normal compacted layer thickness is 6 inches. Soil-cement layers of this dimension is positioned efficiently and compressed with standard highway equipment.

A plating system that develops a single soil-cement layer parallel to the slope is often applied in less critical areas for slope protection. If the soil-cement facing does not start at natural ground level, the lower part of the embankment should remain on a flatter slope than the part safeguarded by the soil-cement; or a beam is arranged at the lowest elevation of the facing. It is necessary that the soil-cement expand underneath the minimum water level and over the maximum water level.

The top of the facing should contain a freeboard allowance of minimum 1.2 times the projected maximum wave height, or 5 feet, whichever is higher. The edges of the finished soil-cement layers should not be cropped since the rounded starstep effect allows retard wave runup. Soil-cement is produced with different types of soils.

The main standard for finding out the soil type is gradation. Coarse sandy or gravelly soils having about 10 to 25 percent material passing the No.200 sieve are perfect (American Society for Testing and Materials Standard Sieve Series). These soils are sufficiently stabilized with from 3 to 5 sacks of cement per cubic yard of compacted soil cement.

Standard compaction and placement control for soil-cement is recommended. If the amount of material smaller than the No.200 sieve surpasses 35 percent, some effort to determine a coarse material is appropriate from a processing cost standpoint. Soils with 50 percent or more material passing the No.200 sieve are not suggested for being applied in their natural state.

To get more details, go through the following link aboutcivil.org



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Published By
Rajib Dey
www.constructioncost.co
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