Types and Uses of Bulldozers in Construction

Most construction projects need moving of a large amount of earth, soil, sand, rubble, and debris all the time, especially at the beginning of the project. For this purpose, bulldozers come in very handy in land-based construction projects. Today we will see what these powerful machines are and how they are used in the construction industry.

The phrase "bulldozer" comes from an amalgamation of the words 'bull' and 'dose'. The first word implies power, while the latter indicates a will to force something to happen. The first proper bulldozer in history was produced in 1923 by farmer James Cummings and draftsman J. E. Mcleod. But this was used for farming purposes only. Bulldozers saw construction uses by the 1940’s.

What are Bulldozers?

Bulldozers, or dozers, in short, are essentially tractors with a large blade mounted in front of them. The tractor helps push the blade around the ground. Perpendicular to the ground, the blade is a thick plate of metal, wider than the tractor behind it and sometimes even half as tall. Sometimes the dozers come equipped with a claw-like device attached in the rear called a ripper to loosen up the ground before pushing it around.

Mobility

The vehicles are generally mounted on tracks, which gives them excellent ground traction and mobility on rough unstable terrain. Some versions of bulldozers come with extra-wide "swamp tracks" to handle soft ground. Though in uneven terrain, the use of wheeled bulldozers is common too. These dozers are mounted on four articulated hydraulics-operated large rubber wheels, which gives the vehicle the ability to work on uneven terrain and also much better speed than the tracked versions.

The engines of bulldozers need to be very high-powered since they need to create a huge amount of energy to push heavy objects. Also, the same engine needs to power the often-used hydraulics system. Depending on tasks the engines of dozers can vary from 70 to 1000 horsepower.

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Published By
Rajib Dey
www.constructioncost.co
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How to analyze rate for brick masonry work

While analyzing the rate of brickwork, it is essential to ascertain the quantities of materials (bricks and mortar) and labors. There are different types of ratios for mortar which range from 1:2, 1:4, 1:6, 1:8 etc. Go through the following like to determine the quantity of mortar.

Estimating the quantity of bricks is necessary for the rate analysis.

Quantity Estimation for Brick Masonry - To analyze the rate of brick masonry, 1m3 of brick masonry is taken:

1. Number of bricks for 1 cubic meter of brick masonry:
For 1m3 of brick masonry, the number of typical size of bricks must be 494.

2. Quantity of mortar for 1m3 of brick masonry:

For 1m3 of brickwork, the quantity of the mortar should be 25 – 30%, i.e. 0.25m3 – 0.3m3 of cement masonry. For this purpose, cement mortar is selected as 0.3m3 .

Labor Estimation for Brick Masonry:
Labors which are essential for brick masonry belong to mason for brick work, labours for transmitting materials (sand, cement, bricks, and water), mixing and transporting mortar.

The quantity of labor is provided as requirement of labour in longer period for 1m3 of brick masonry.

1. Mason: The quantity of mason necessary for 1m3 of brickwork is provided as 0.94 days.
2. Labor: The quantity of labor for different types of works like carriage of materials, blending of mortar, carrying of mortar etc. are amassed. The labour necessary for 1m3 of brick masonry is for 1.57 days.

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Published By
Rajib Dey
www.constructioncost.co
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How to prevent segregation of concrete

Definition of Segregation of Concrete?
Major components of concrete are cement, sand, aggregate, and water. Normally, a coating is made to concrete aggregate with cement and sand for developing the consistent mass disjointing of these constituent materials of concrete from each other. It is known as segregation of concrete.

Type of segregation:

1. Partition of course aggregate from the paste.
2. Partition of course agreement paste from the concrete.
3. Partition of water from the cement mix which is also known as bleeding.

The segregation contains unwanted properties in the hardened concrete. It also leads to honeycombing in concrete. Segregation also adversely impacts on stability, compressive strength and all other characteristics of concrete. It also results in forming cavities in the concrete surface.

Reasons for segregation:

The segregation mainly occurs due to the variation in specific gravity and size of its constituent material. Specific gravity of water is 1. Specific gravity of cement is approx 3.15 whereas that of aggregate is 2.6 to 2.7. Because of the variation in specific gravity, lighter particle goes upwards and heavier particle goes downwards and consequently the segregation of concrete occurs.

Other reasons range from greater water cement ratio in concrete. Besides, when excessive water is added at the time of mixing concrete, it results in segregation. Improper vibration for a long period on wet mix of concrete also causes heavy material to setting down and lighter cement sand paste to move upwards. Imperfectly proportioned mix and inappropriate placing on site may also lead to segregation.

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Published By
Rajib Dey
www.constructioncost.co
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How to measure the volume of silt content in sand

In this civil engineering video tutorial, you will learn some vital tips to work out silt percentage in sand or course sand to ensure that whether the sand is eligible to be used in concrete or not. It is recommended that the percentage of silt content of sand in concrete should be over 6%.

The silt stands for a very fine particle and the size of it is under 150 Microns. Silt content can be shrinked and inflated because of the weather condition. Therefore, it can impact the strength of the structure.

Impacts of Silt:

1. Crack will be created on concrete. (some cracks are found in the wall)
2. Silt content includes evaporated matters and salts. (mortar will be exposed at the time of plastering)
3. It engrosses more water. (broadened & shrink owing to the weather condition.

To determine the percentage of silt conent, the following items will be required :-

a. 250 ml, measuring cylinder
b. Course or fine sand
c. Water
d. Sand

The calculation is done as follow - Initially, it is required to area of cylinder as the cross sectional area from top to bottom will be same for the cylinder.

Area of cylinder = πr2 x Height

Suppose, the cylinder is filled with sand up to 100 ml, then water is added up to 50 ml. So, total volume will be 150 ml. Then, shake the bottle and wait for 2 hours. Now, it is found that the percentage of silt content in the sand is 5 ml. You can check the percentage of silt content in the following way :-

= Volume of silt (taken as V2) / Volume of sample (sand or course sand; taken as V1) x 100
= 5 / 100 x 100 = 5%

To get more information, watch the following video tutorial.

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Benefits of compressive strength of concrete & factors impacting compressive strength

Concrete becomes leading usable material as soon as water is added to it. The strength of concrete is mainly dependent on aggregates, while cement and sand are responsible for the characteristic of binding and workability together with flowability to concrete.

Compressive strength means the capability of the material or structure to provide resistance against compression. The Compressive strength of a material is based on the capability of the material to withstand failure that appears as cracks and fissure.

With compressive test, the push force enforced on the both faces of concrete specimen and the maximum compression borne by concrete devoid of failure is recorded.

The purpose of concrete testing is to deal with the Compressive strength of concrete as it facilitates to measure the concrete strength to protect gainst Compressive stresses among structures while other stresses like axial stresses and tensile stresses are developed with reinforcement and other means.

In technical term, Compressive Strength of concrete is explained as the Characteristic strength of 150mm size concrete cubes @28 days.

Compressive strength of Concrete and its advantages:-

Concrete is formed by mixing sand, cement, and aggregate. The strength of the concrete is based on several factors which range from individual compressive strength of its materials (Cement, Sand, aggregate), quality of materials applied, air entrainment mix proportions, water-cement ratio, curing methods and temperature effects.

With Compressive strength, the entire strength of the concrete as well as information on the above mentioned factors can be obtained. By initiating this test, it is possible to analyze the concrete strength psi and quality of concrete formed.

The compressive strength of concrete is influenced by the factors given below:-

Coarse aggregate: Concrete becomes uniform by blending aggregates, cement, sand, water and different other admixtures. In spite of perfect mixing, some micro cracks may occur because of variations in thermal and mechanical properties of coarse aggregates and cement matrix, which results in collapsing of concrete structures.

In concrete, the size of aggregate is a key factor for compressive strength. When the size of aggregate is raised, then the compressive strength will also be increased.

But later on, it is discovered that bigger size of aggregates can raise strength in preliminary stage but the strength is decreased greatly. It happens because of the abridged surface area for bond strength among cement matrix and aggregates and lower transition zone.

Air-entrainment: Air entrainment in concrete is a useful feature to avoid damages because of freezing and thawing. Later on, multidimensional benefits of air entrainment lead to improve the workability of concrete at lower water/cement ratio.

When the required workability is attained at lower water content, the concrete contains superior compressive strength which consecutively results in creating light concrete with superior compressive strength.

Water/Cement ratio: Excessive water is injurious to the strength of concrete. Cement is considered as the major binding material in concrete that requires water for hydration process, but the water quantity is constrained to about (0.20 to 0.25) % of cement content. The excess water is useful in case of workability and finishing of concrete.

When the water in the concrete matrix gets dried, it departs large interstitial spaces between aggregate and cement grains. This interstitial space in turn creates primary cracks throughout compressive strength testing of concrete.

Go through the following article, to get more details civilread.com



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Published By
Rajib Dey
www.constructioncost.co
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Different categories of sands and their applications

The sand is mainly applied for rock particles which mainly vary in grain size among 2 mm and 1/16 mm. In composition, they are primarily an oxide of silica SiO2.

Mineralogically, they mostly include broken grains of mineral Quartz (SiO2) that is formed due to the crashing of sandstones and equivalent rocks.

Categorization of Sands: Sands are classified variously on the basis of their Based on the mode of origin, composition, and grain size, the sands are differently categorized.

The mode of origin: With adherence to the mode of origin, there are three types of sands like pit sands, stream sands and marine sands..

The pit sands are generally sharp and angular in outline. Winds generally deposited them and develop accumulations in soils covered by clays. Good quality mortars can be produced from these sands by purifying and cleansing them properly.

The river sands come about large accumulations along the base and banks of all the rivers in plains and semi-hilly areas. The shape of the sand grains in river sands appear almost round (because of significant movement in river waters).

These do not contain clay, salt encrustations, and organic impurities. So, these are frequently utilized to produce mortars, plasters, and concrete.

The marine sands are found on beaches and along the seashores. Similar to river sands, they comprise of rounded grains of quartz. There are some problems with these sands as their grains are mostly wrapped with coatings of salts from sea water.

These salts can’t be separated easily. So, if these salts are utilized with mortars or concrete, a reaction occurs with the binding materials and produce lots of difficulties. Beside, the salt encrustations are often hygroscopic, it means they consume moisture from the atmosphere.

It also leads to delayed setting, dampness. Besides, efflorescence may also happen in mortar or concrete that is formed with these sands. Therefore, the quality of marine sands is substandard and should not be recommended. But, in case of requirements, marine sands should be cleansed perfectly prior to utilize them.

In order to learn how sand is categorized on the basis of composition and grain size, go through the following construction article.

Source: civilseek.com

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Published By

Rajib Dey

www.constructioncost.co

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