Concrete holds a high place in today's construction industry due to its many strengths and durability.

Here we discuss concrete, uses of concrete, properties of concrete, compaction of concrete, curing of concrete, mixing of concrete, proportioning of concrete, etc.

The construction industry underwent a major transformation when it was discovered that concrete could be used for any shape at any place, free from the confines of stone and iron.

Concrete is a must for building materials, as well as for architectural standards, which can be created by mixing bonding materials, fine aggregates and coarse aggregates with water at a proper rate.

When used alone, concrete is called Plain Concrete. Also, when steel bars are systematically reinforced into concrete, it is reinforced cement concrete (R.C.C).

Read more; Precast Concrete Construction Technology...

Concrete Compaction | Properties of Concrete

Content...

• Properties of Concrete
• Compaction of Concrete
• Curing of Concrete
• Mixing of Concrete
• Proportioning of Concrete

What are the Grades in Concrete?

In simply, Grades is the ratio of concrete. The concrete ready mix plant is set up to supply the concrete requirement's of the workplace (construction site), most of the ready mix plant is owned by the construction companies in our country.

When ordering concrete to the construction sites, it is sufficient to state the value of grade and volume (meter cubes).

The site manager or the storekeeper can be done a concrete order process manually in the construction site. The higher the grade of the concrete, the greater the amount of cement required for that concrete mix.
(That is, more than 3 grams of 20 grades of concrete will cost 30 grams of concrete.

Column base of the building, Column, Lintel, Beam, and Slab are the main types of concrete structures. The construction of a house in our country often does not fall into the side of industrial construction,

these are often used in mixing ratios as a 1: 2: 4 (cement: sand: metal).

This mixture is also known as G.20. This means that in 28 days the concrete will have a minimum compressive strength of 20N / mm². However, in domestic construction, this mixture is used as 1: 2: 4 (cement : sand: metal) in our country.

The concrete used for the floor of a house is called Bed Concrete, and the bottom of the foundation of the apartment is called Screed Concrete. G.15 states that in 28 days, such a concrete will achieve a compressive strength of 15N / mm². So it takes 28 days for Concrete to get its full strength.

screed concrete

Grades 10 ⇨ 1 : 4: 8
Grades 15 ⇨ 1 : 3: 6
Grades 20 ⇨ 1 : 2: 4
Grades 25 ⇨ 1: 1 1/2 : 3
Grades 30 ⇨ 1: 1: 2
Grades 40 ⇨ 1 : 1 : 2 + Admixture

Normally, add a variety of admixtures for making concrete blends with grades 40 or higher. Admixture and mixing ratios can vary from place to place. I'll get an article on Admixture the other day, so if there's anything to ask comment.

concrete work

For example,
we will look out how to find the volume of 'grade 30' concrete requirement for one concrete footing in working site,
Its length, width, and height are 2000mm, 2000mm, and 300mm respectively.

Volume= 2000mm x 2000mm x 300mm
=2m x 2m x 0.3m
=1.2m³
=1.2 meter cube//

This is how the scene happens in the workplace in practically. Normally, we do not use 'feet' in calculation purposes. This king off work is the quantity surveyor job in the workplace. But sometimes, the calculations process is done by the site supervisor, but both of these profession's need to be done in already, I think

(Because the site manager is asking both of them, in that the time you can not say "sir I don't know")

There are several different tests related to concrete in construction. They are,

1. Concrete Slump test
2. Concrete Cube test... etc. As a quantity surveyor or any profession, you must know about these two tests.

There are different types of concrete tests such as; slump test, cube test, etc.

Normally, the cube test is ready to mix plants Before the plant arrives at the plant and inside the workplace, the test cube is inserted before the workplace.

After testing the test Cube cubes between the two locations the results should be the same.

The molding length of the mold is 10cm x 10cm x 10cm or 15cm x 15cm x 15cm.

But the 15cm x 15cm x 15cm mold is now widely used.

Test cube is not corroded for lesser-known concrete work like G.15.

Below are a few test cube cubes that were sent to the laboratory for the compression strength test.

test cube

The quality of any concrete mixture depends on the following factors,

• Qualities of raw materials
• Classification of affiliations
• Mixed ratio
• The amount of water collected
• The ability to work

Properties of concrete

• Hard
• Strength
• Durability
• Density
• Non-porous
• Fire resistance
• Economical
• Water resistance

Concrete Compaction

The entire concrete used in the work shall be bid gently (not thrown) in layers not exceeding 150 mm. It should be deposited nearly as practicable in its final position and without segregation in one continuous operation up to the movement or construction joints.

It shall be adequately compacted by means of vibrators till air bubbles cease to appear on the upper surface and a dense concrete is obtained. The vibrator will be operated in a near-vertical position. and the duration of vibration limited to that necessary to produce satisfactory consolidation without causing objectionable segregation.

The officer-in-charge may however at his discretion, permit hand compaction for certain items depending upon the thickness of the members and feasibility for vibrating the same. Hand compaction shall be done with the help of tamping rods so that the concrete is thoroughly compacted and completely worked into the corners of the formwork.

The layers of concrete shall be so placed that the bottom layer does not finally set before the top layer is placed. Compaction shall be completed before the initial setting starts Le within 30 minutes of addition of water to the dry mixture. Retempering of concrete shall not be permitted.

honeycomb in a concrete column

Curing of Concrete

After the concrete has begun to harden - i.e about 24 hours after its laying, the curing shall be done by keeping the concrete damp with moist gunny bags, wet straw, sand, or any method except water under pressure, approved by the officer-in-charge. Curing shall be done for a minimum of 7 days. after which period masonry and flooring work over the lime-concrete foundation or base concrete may be started.

Proportioning of concrete

There are two types, proportioning also know as batching of concrete
Proportioning by Volume

Proportioning by Weight

The strength of concrete can be improved by using proper mixing and quality materials. Therefore, when we selecting materials for concrete, always we care about the quality of the material and its important thing about concrete construction work. Before the mixing process of concrete, either the working site or batching plant, the materials are batching accordingly their mixing proportion. Normally, the concrete batching process is done by the volume of the material and the weight of the material. Volume batching is used for small scale construction work and the weight batching is used in the large scale concrete construction work, also concrete batching plants use the weight of materials for their batching process. This process is known as batching.

When we measure material quantity accordingly to their volume, the gauge box we used to select materials in accordance with the ICTAD standard.

What is the standard size of a cement or aggregate measuring box? Size : 300 mm x 300 mm x 400 mm. can measure sand & aggregate. Dimensions of A Standard measuring box : 12″ X 12″ x 15″ = 1'X 1'X 1'3"

concrete gauge box dimensions

Don't forget, concrete batching are two types,

Volume Batched and Weight Batched,

and

Concrete mixing are two types,

Hand Mixing

Machine Mixing

Mixing of Concrete

Hand Mixing

When permitted for Volume Batched mixes, this shall be done on a smooth, clean, and watertight platform of suitable size and in the following manner.

The measured quantity of sand shall be spread evenly.

The cement shall be dumped on the sand and then distributed evenly.

The sand and cement shall be mixed intimately with shovels, turning the mixture over and over again until it is of even color throughout and free from streaks.

The measured quantity of coarse aggregate shall be spread out and the sand cement mixture shall be on top.

This shall be mixed at least three times dry, by shoveling and turning over from center to side then back to the center and again to the sides.

A depression shall be made in the middle of the mixed pile to receive the water.

Three-quarters of the total quantity of water required shall be added while the material is turned in towards the center with shovels. The remaining water shall be added by a water-can fitted with a rose-head, while slowly turning the whole mixture over and over again at least three times until a uniform color and consistency is obtained throughout the pile.

The mixing platform shall be washed and clean at the end of the day.

Machine Mixing

The mixer drum shall be free of hardened mortar adhering to its inner surface. Before mixing commence the drum shall be primed by stashing with rich cement grout. A measured quantity of dry coarse aggregate shall be first placed in the hopper. This shall be followed with the measured quantity of fine aggregate and then cement. The skip shall be raised and the dry materials slipped into the drum. The dry materials shall be mixed for at least four turns of the drum after which the correct quantity of water shall be added gradually while the drum is in motion, to ensure even distribution of the materials. The total quantity of water for mixing shall be introduced before 25% of the mixing time has elapsed and shall be regulated to achieve the specified water-cement ratio. The complete contents of the mixer shall be emptied before recharging.

When the mixer is closed down for the day or for any period, exceeding 20 minutes, the drum shall be flushed clean.

Mixing Time

The materials shall be mixed for a period of not less than 2 minutes and until a uniform color and consistency are obtained. The time shall be counted from the moment all the materials have been put into the drum.

Common concrete mix proportion and their application

1 : 1: 2 --- For machine foundation, footings for steel columns and concrete underwater.

1: 1 1/2 : 3 --- Water tanks, shells and folded plates, for other water retaining structures.


1: 2: 4 --- Commonly used for reinforced concrete works like beams, slabs, tunnel lining, bridges

1 : 3: 6 --- Screed Concrete, Piers, abutments, concrete walls, the sill of windows, floors.

1 : 4: 8 --- Mass concretes like a dam, a foundation course for walls, for making concrete blocks.