CIVIL ENGINEER

civil engineering, concrete, cement, bricks, sand, aggergate, stone, types of civil engineering, subject of civil engineering

LightBlog

Breaking

Showing posts with label concrete. Show all posts
Showing posts with label concrete. Show all posts

Sunday, 2 September 2018

CONCRETE AS CONSTRUCTION MATERIAL
September 02, 2018

CONCRETE AS CONSTRUCTION MATERIAL

CONCRETE AS CONSTRUCTION MATERIAL


concrete is the most widely used man-made construction material in the world and is second only to water as the most utilized substance on the planet. It is obtained by mixing cementing materials, water, and aggregates, and sometime admixtures, are filled by the smaller particles (fine aggregates) the voids of fine aggregate are filled cement water paste which in addition to filling the voids of fine aggregate, coats the surface of fine and coarse aggregates and binds them together as it cures, thereby cementing the particles of the aggregates together in a compact mass.
                                                                     The strength, durability and other characteristics of concrete depend upon the properties, of its ingredients, on the proportions of the mix, the method of compaction and other controls during placing, compaction, and curing. the popularity of the concrete is due to the fact heat from the common ingredients, it is possible to tailor the properties of concrete to meet the demands of any particular situation. The advances in concrete technology have paved the way to make the best use of locally available materials by judicious mix proportioning and proper workmanship, so as to produce concrete satisfying performance requirements.

The key to producing a strong a durable and uniform concrete. CONCRETE AS CONSTRUCTION MATERIAL is the following.

CONCRETE AS CONSTRUCTION MATERIAL


  •  CEMENT
  • AGGREGATE
  • STEEL
  • WATER

CEMENT

       Portland cement, the most widely used cementing ingredient in present-day concrete comprises phases that consist of compounds of calcium, silicon, aluminum, iron, and oxygen.  Cement is used as the binding material and acts as a binder for coarse and fine aggregates. Generally, ordinary portland, cement is used to form concrete. Initial setting time of good cement should not be less than 30 minutes and the final setting time should not exceed 10 hours.

 AGGREGATE

               There are primarily naturally occurring, ind=ert granular materials such as sand, gravel, or crushed stone. However, technology is broadening t include the use of recycles materials and synthetic products.
              The granular material generally inert chemical such as natural sand, gravel, crushed stones and air-cooled iron blast furnace slag are called aggregates. If only CEMENT is used for the construction, the concrete will result in shrinkage and ultimately cracks develop. So as to avoid these cracks, aggregates are used. These aggregates are bound together by means of cement. The aggregates are classified into two categories such as final and coarse aggregates. The material which is passed through sieve no 480 is called fine aggregates and which retained on sieve no 480 is called coarse aggregates. These aggregates should be clean. sharp, angular, well graded, hard, durable and free from foreign matters.

STEEL

           The Steel reinforcement is generally in the form of round bars of mild steel. The diameters of bars vary from 5 mm to 40 mm. Sometimes the square bars or twisted bars or ribbed-bars or ribbed-tor steel are used as steel reinforcement.
        Following are the reason as to why mild steel has been adopted as reinforcing material
         These are a proper band between CEMENT concrete and mild steel. Hence, it enables concrete to transmit its stresses to steel.
        The coefficient of linear expansion of steel is almost the same as that of concrete. Hence o internal stresses are set up within reinforced concrete members due to rise or fall in temperature.
        Deformed or twisted bars which are made of mild steel have considerably high yield stress, tensile strength, and bond strength.

 WATER

           The water to be used in making concrete should conform to the drinking water standard. It is less expensive but the most important ingredient of concrete. The water, which is used for making concrete should be free from acids, alkalies, salts, oil, grease and decayed vegetable matters. The amount of water should be of that, which will produce concrete of required quality.




0
By at No comments:
Labels:

Friday, 14 July 2017

Production of concrete
July 14, 2017

Production of concrete

Production of concrete

           The ingredients of good concrete and bad concrete are the same, the only difference is the care taken during the manufacture of concrete. It is necessary to take great care of each stage of the manufacture of concrete for producing good quality concrete. 
  • Batching 
  • Mixing
  • Transporting and Placing 
  • compacting
  • Curing
  • Finishing

Batching

           The measurement of material for making concrete is known as batching. There are two methods of batching
  • Volume Batching
  • Weight Batching

VOLUME BATCHING

           Volume Batching method, ingredients of concrete are batched by volume. It is not a good method. The weight of the volume of dry sand is more than the same volume of the moist sand. The amount of solid granular material in a cubic meter is an indefinite quantity. So as concrete materials are measured by weight. Cement is always measured by weight. It is never measured by weight. It is never measured in volume. The volume of one bag of cement is taken as thirty-five liters. Gauge boxes are used for measuring the fine and coarse aggregates. The volume of gauge box is made equal to the volume of one bag of cement.
           Water may be measured in KG or Liters as convenient. The quantity of water required is a product of one KG per liter. The quantity of water required is a product of the water-cement ratio and the weight of cement.

 WEIGHT BATCHING 

           It is the correct method of measuring the materials. For important concrete structures weigh batching system should be adopted. Different types of weight batchers are available.

MIXING

          The process of rolling, folding and spreading of particles is known as the mixing of concrete. The materials should be mixed thoroughly for the production of uniform concrete. It should also keep in mind that cement paste completely covers the surfaces of aggregates. There are two methods adopted for mixing concrete.
  • Hand Mixing
  • Machine Mixing

Hand mixing

            Hand mixing is done only for small works. In this method, 10 percent more cement is added, because of the mixing by hand cannot be done thorough and efficient. It should be done over and impervious concrete floor. Firstly fine and coarse aggregates are spread out in alternate layers. Now cement is poured on the top of it and mix them with a shovel. Now water is sprinkled over the mixture and simultaneously turned over. The operation is continued until a good uniform, homogeneous concrete is obtained.

Machine mixing

            In the case of large works, the mixing of concrete is done by a machine known as a mixer. It is efficient and economical when the quantity of concrete to be produced is large. 
           In machine mixing, all the materials of concrete including water, are collected in a revolving drum and the drum is rotated for a certain period. The resulting mix is then taken out from the drum.
            Machine mixing produces concrete of better quality. The water should enter the mixer at the same time or before the materials are placed. The concrete mixer should be thoroughly washed and cleaned after use. The concrete discharged by the mixer should be consumed within 30 minutes.

Transporting and Placing Of concrete

            The concrete, as it comes out from the mixer, it is ready for transportation and placed on them from work. These are various equipment, those are used for the transportation of concrete. The precaution to be taken while transporting concrete is that the homogeneity obtained at the time of mixing should be maintained while being transported to the final pale of deposition. For ordinary building works., the human ladder is formed and concrete is conveyed in pans from hand to hand. For important and large works various mechanical devices such as dumpers, trucks, mixers, buckets, chutes, belts, pumps, hoist etc. may be used.
          Transportation should be in such a manner so that there is no segregation of the aggregates. The concrete should be dropped vertically from a reasonable height. The stiff mix should be used in case of vertical laying of concrete otherwise bleeding will takes place.

CURING
1
By at 1 comment:
Labels: ,