Various types of scales in surveying

This construction article sheds light on various types of scales employed in Surveying…

The scales are categorized as follows:

1. Plain Scale
2. Diagonal Scale
3. Vernier Scale
4. Scale of chords



Plain Scale

On Plain Scale, it is reasonable to calculate two dimensions only. As for instance, measurements like units and lengths, metres and decimetres etc.

The engineers, Architects and Surveyors generally employ six different plain scales in metric.

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Diagonal Scale

On diagonal scale, it is reasonable to calculate three dimensions like metres, decimetres and centimetres, units , tens and hundreds; yards, feet and inches etc.
A short length is seperated into number of parts by applying the principle of equivalent triangle in which sides are proportional.

1-1 represent 1/10 PQ
2-2 represent 2/10 PQ
9-9 represent 9/10 PQ



Vernier Scale

It is an effective tool for measuring the fractional part of one of the smallest divisions of a graduated scale.

It generally contains a small auxiliary scale that slides side by side of the main scale.

Least count of the vernier = the variation among smallest division on the main division and smallest division on the vernier scale.

Scale of Chords

With scale of chords, it is possible to estimate an angle and is marked on either on rectangular protractor or an ordinary box wood scale.

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Different types of surveying process

In this construction video tutorial, Ms.C.S.Suganya, the renowned assistance professor in civil engineering department, has briefly explains surveying and it’s different categories.

The surveying is primarily segregated in two parts :-

Geodetic Surveying

Geodetic surveying refers to the survey under which the curvature of the earth is considered and superior degree of perfection in linear and angular observations is gained. The geodetic surveys spread over big areas and lines relating any two points on the surface of the earth are taken as arcs. To workout their predictable distances on the plans or maps, the rectification for the earth’s curvature is employed to the calculated distances. The angles among the curved lines are considered as spherical angles. A knowledge of spherical trigonometry is required for creating measurements for the geodetic surveys. The area remains at 250 kilometer square.


Plane Surveying

Plane surveys are mostly recognized process of surveying and here, the earth is taken as a flat or "plane" surface. It is useful for small-scale surveys in restricted areas, the curvature of the earth does not provide any impact on the results, consequently, the calculations and results can be referenced to a plane or flat surface. The surveying is done for less than 250 kilometer square.


Secondarily, the surveying is segregated into the following parts :-



Land Surveying
A land survey, or simply survey, stands for the scientific process of calculating the dimensions of a specific area of the earth's surface, along with its horizontal distances, directions, angles, and elevations.

Hydrographical Surveying
Hydrographical survey belongs to the science of measurement and explanation of features which impact maritime navigation, marine construction, dredging, offshore oil exploration/offshore oil drilling and relevant activities.
Astronomical Surveying

An astronomical survey refers to a general map or image of a area of the sky which requires a definite observational target. On the other hand, an astronomical survey may contain a set of various images or spectra of objects which contribute to a common type or feature.

To get more detailed information, watch the following video tutorial.

Some useful tips on concrete curing

Curing concrete is a complicated method that entails preservation of exact temperature, humidity, circulation, and other aspects. If Cracks occur, the strength of cement is impacted because of insufficient arrangements for these controls. Crystals form with reaction of water with Portland cement.

Curing makes sure that the concrete gains its optimal strength. The strength of concrete is influenced by crystal growth inside the concrete matrix. These crystals develop because of the hydration i.e. the reaction among the water and Portland cement. If water is insufficient, the crystals fail to develop and for this reason the concrete can’t gain the optimal strength. The existence of water allows the crystal development that enfolds the gravel and sand mix, inducing interweaving with each other.



Controls During Curing

Keeping exact curing temperature is vital so that the hydration reaction remains unaffected. If the concrete is very hot, the hydration reaction will be so fast for a proper crystal growth. Therefore, concrete fails to gain accurate strength. If the reaction becomes exothermic, variance in temperature will be produced inside the concrete and it may lead to cracks. Rough surface and a porous concrete structure may be formed because of Inappropriate hydration on the concrete surface. Such porous concrete structures will allow calcium hydroxide to contact the concrete surface that leads to efflorescence. Besides, the concrete structure becomes feeble. Other significant points to be considered throughout the curing are perfect humidity, circulation, insulation, and time control.

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Autogenous Shrinkage

Autogenous shrinkage takes place if the shape of the cement paste is lost because of insufficient water for hydration. Autogenous shrinkage occurs when the volume of the hydrated cement products is under the volume of the cement and water mix prior to starting of hydration. It does not occur for external factors like loss of moisture or temperature variations. Autogenous shrinkage is generally not important in concrete with a water-cement ratio of more than about 0.4. Though, as this ratio is reduced under that limit, autogenous shrinkage is expected to be raised. There will not be sufficient water in the concrete for curing if amalgamated with a water cement ratio below 0.40. In the initial phase, when the tensile strength is low, and concrete is below the effects of high temperature divergence, concrete may crack due to occurrence of autogenous shrinkage.



Improved Curing

The particular controls of temperature, humidity, and time which are vital throughout the process of curing can’t be achieved precisely and for this reason perfect concrete strength and other characteristics are impacted. Self-curing technologies becomes popular as it applies substances for internal curing. Proper materials are used to the wet concrete surface to reduce the loss of water from the concrete. The materials produced are emulsions of paraffins which are dispersed on to the surface. A superior concrete is generated with minor permeability that has superior strength and longevity.

Article Source : http://www.brighthubengineering.com

Glass Fiber Reinforced Concrete (GFRC) – Definition and various advantages

Glass fiber reinforced concrete belongs to an engineered material that comprises of cement, polymers, and glass fibers. These materials are implanted in the cementious matrix. The GFRC properties are impacted by the glass contents, mix design, and production process. GFRC is mostly suitable for outside applications.

Glass fiber reinforced concrete is mainly a concrete material that employs glass fibers for the reinforcement, as an alternative to steel. Generally, the glass fibers have resistance capacity against alkali. Alkali resistant glass fiber is very useful because it provides a greater resistant to the ecological effects. GFRC is formed by amalgamating cement, glass fibers, and polymers. It is usually casted in thin sections. As the fibers are free from rust like steel, safeguarding concrete coat is not essential for controlling rust. The weight of thin and hollow products formed with GFRC is significantly lighter as compared to the usual pre-cast concrete. The material characteristics are impacted with the concrete reinforcement spacing, and the concrete reinforcement mesh.

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Benefits of using GFRC

• GFRC is made of minerals and it can’t be burnt easily. If it is uncovered to a flame, the concrete acts as a thermal regulator. It safeguards the materials set with it from the flame heat.
• These materials are reasonably lighter as compared to the traditional materials. Therefore, the process is quick and easy for installing them. Concrete may be formed in thin sections.
• Casting for GFRC can be done into any shape of columns, wall panels, domes, moldings, and fireplace surrounds.
• High strength is gained with GFRC as it is strong and resistant to cracking. It contains a high ratio of strength-to-weight. Therefore, the GFRC products are long-lasting and light. Due to light weight, the transportation costs are considerably less.
• GFRC is examined in the laboratory and also in the actual installations, and predicted to endure as long as pre-cast concrete. In several ecological conditions, like when uncovered to salts or moisture, GFRC is expected to function in a superior manner because of the non existence of steel reinforcement that may decay.
• GFRC is thin and tough, with weight being 75% to 90% less in contrast to solid concrete. Less weight reduces the load functional on the structure. The light weight and tough material facilitates suppleness in design, and minimizes the effect on environment.
• Superior strength improves the capability to undergo seismic loads.
• GFRC is less susceptible to weather effects and more defiant to freeze thaw than the normal concrete.
• Evaluation of GFRC to Precast Concrete.

The elasticity and compactness of the GFRC is better as compared to precast concrete. The proportion of cement to sand for GFRC is roughly 1:1, whereas for precast concrete it is 1:6. The glass fibers contained to reinforce the concrete creates significantly superior impact strength and reduces permeability to water and air as compared precast concrete. GFRC appears as a natural stone and allows the designer to have greater flexibility in form, color, and texture.

Article Source : http://www.brighthubengineering.com

Pros and Cons of Flat Slab In Concrete Construction

A flat slab belongs to a two-way reinforced concrete slab that comes with without beams and girders. The loads are delivered directly to the supporting concrete columns

Benefits of Flat Slab

Flat Slabs provide huge benefits to the engineers as compared to other reinforced concrete floor system and so they are mostly recognized to be utilized in several buildings. Given below, the benefits of flat slab.

Adaptability in room layout

Partition walls are arranged in anywhere.
Different types of room layouts are accessible to the owner.
Get rid of using false ceilings.



Easy arrangement for Reinforcement

Flat slab can be easily arranged because of  easy to follow reinforcement detailing.
Simple Framework installation.
Large table framework can be utilized in flat slab



Building height can be minimized

• Floor height is minimized as there is not beam and as a result the building height will also be decreased.
• Roughly 10% of the vertical member could be saved.
• Foundation load will also be decreased.

Flat Slab Design

Less construction time

As big table framework is utilized, the construction time is minimized significantly.

Prefabricated welded mesh

• Standard sizes
• Fewer installation time
• Superior quality control

Smooth Auto sprinkler

Cons of Flat Slab

There are also some disadvantages for flat slab which are described below:-

• Span length is medium - In flat plate system, span can’t be increased.
• Not recommended for supporting brittle (masonry) partitions
• Application of drop panels may hinder with bigger mechanical ducting
• Complicated middle strip deflection - In flat slabs, the middle strip deflection is very complicated.
• Greater slab thickness - Relating to standard reinforced concrete two way slab system, the density of flat plate slabs are high.

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Definition of stretcher bond and header bond in brickwork

Given below various types of bonds generally found in brick work.

• Stretcher bond
• Header bond
• Facing bond
• English bond
• Flemish bond
• Dutch bond
• English cross bond
• Brick on edge bond
• Raking bond
• Zigzag bond
• Garden wall bond

Definition of a Stretcher Bond

To develop stretcher bond, bricks are placed horizontally like stretchers on the faces of walls. The length of the bricks remains along the horizontal direction of the wall.
If it is required to build up the walls with half brick thickness, stretcher bond becomes very effective. The normal size of the brick is 9cmx9cmx18cm. If the wall having thickness 9cm is to be built up, then stretcher bond will be ideal for that.

Different types of wall constructions are accomplished with this type of bond.

• Sleeper walls
• Partition walls
• Division walls (internal dividers)
• Chimney stacks

It should be kept in mind that this bond will be effective for the walls having less thickness and the bond will not be suitable when the thickness of the walls is in excess of half of the length of the brick.

Definition of Header Bond

The square face of the brick with dimension (9cm x 9cm x 9cm) is known as “header”.

When all the bricks are arranged as headers on the faces of the walls, the bond that is developed is described as “Header Bond”.

Header bond is applicable for developing the walls with full brick thickness which estimates 18cm.
Header bond is defined as heading bond. The overlap is retained the same as half width of the brick. To attain this, three quarter brick bats are applied in alternate courses as quoins.

Since header bonds do not contain enough strength in delivering pressure along the length of the wall, it is not recommended to employ this type of bond for load bearing walls.

Header bond is ideal when the design calls for curved surfaces to be built up. In such cases, stretcher bond should not be applied. In addition to utilize it for curved surface, it is also very useful for the brickwork in foundations.

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