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Procedure of Concrete Compression Test

Concrete compression test is done to know the concrete compressive strength. It is one of two well known concrete test. Another one is slump test.

For this purpose, either concrete cube or cylinder specimens are tested in the laboratory.
3 concrete specimens are generally made and cured for 28 days at site and then sent to laboratory for testing.

Read More:
How to Make Concrete Cylinder Specimen
How to Make Concrete Cube for Compression Test?

In this post, I'll describe step by step procedures of concrete compression test at laboratory.

concrete compressive strength testing procedure

Required things:
You'll need following things for testing concrete compressive strength -

* Ruler
* Paper
* Pen/Pencil
* Calculator
* Measuring tape
* Safety goggles
* Gloves
* Testing machine, and ofcourse,
* Concrete specimens (Cylinder/Cube)

Procedure of Concrete Compression Test


Step1 - Preparation: Check all the things you need are ready. Check concrete compression machine is in working order.

Step2 - Safety: Wear hand gloves and safety goggles.

Step3 - Taking measurement: Take the measurement of concrete specimens (which are sent to laboratory for testing). Calculate the cross sectional area (unit should be on mm2) and put down on paper. Do the same for each specimen.

Step4 - Start machine: Turn on the machine. Place one concrete specimen in the centre of loading area.

Step5 - Lowering piston: Lower the piston against the top of concrete specimen by pushing the lever. Don't apply load just now. Just place the piston on top of concrete specimen so that it's touching that.

Step6 - Applying load: Now the piston is on top of specimen. It is the time to apply load. Pull the lever into holding position. Start the compression test by Pressing the zero button on the display board.

Step7 - Increasing pressure: By turning pressure increasing valve counter-clockwise, adjust the pressure on piston so that it matches concrete compression strength value. Apply the load gradually without shock.

Step8 - Test is complete: Observe the concrete specimen. When it begins to break stop applying load.

Step9 - recording: Record the ultimate load on paper displaying on machine's display screen.

Step10 - Clean the machine: When the piston is back into its position, clean the creaked concrete from the machine.

Step11 - Turning off machine: Match your record once again with the result on display screen. The result should still be on display screen. And then turn off the machine.

Step12 - Calculate concrete compressive strength: The result we got from testing machine is the ultimate load to break the concrete specimen. The load unit is generally in lb. We have to convert it in newton (N). Our purpose is, to know the concrete compressive strength.

We know, compressive strength is equal to ultimate load divided by cross sectional area of concrete specimen. We took the concrete specimen's measurement before starting the testing and calculated cross sectional area.

Now we got the ultimate load. So we can now calculate the concrete compressive strength. 
Compressive strength = Ultimate load (N) / cross sectional area (mm2).
The unit of compressive strength will be N/mm2.

Normally 3 sample of concrete specimens are tested and average result is taken into consideration. If any of the specimen compressive strength result varies by more than 15% of average result, that result is rejected.
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Responsibilities of a Construction Supervisor

In a simple sentence, a construction supervisor is an employee who supervises the overall construction project. But his responsibilities are not only limited to site supervising. He is an important person for a construction project and his responsibilities are huge from starting to finishing of a project.

Qualification of a supervisor varies employer to employer. The responsibilities imposed on him also vary depending on qualification. It can be high school passed or diploma holder or degree engineer. So, obviously, the responsibilities can't be same for both diploma holder and degree holder.

However, we can outline the responsibilities of a construction supervisor into following two categories -

construction supervisor responsibilities

Responsibilities of a Construction Supervisor

 
* Operational Responsibilities
* Managerial Responsibilities

Operational Responsibilities
It includes the following responsibilities:

Quality Control: Site supervisor is responsible for maintaining overall quality of a construction project. He will ensure the work is done as per standard construction procedures.

Implementing policies: Construction supervisor is responsible to implement company policies, government policies and other policies related to construction.

Maintaining construction schedule: Construction supervisor is responsible for timely-finish task according to schedule. He will distribute duties among stuffs. Review the schedule weekly or monthly and take necessary steps if target isn't acheived.

* Managerial Responsibilities
It includes the following responsibilities:

Managing staff members: Supervisor will evaluate staff members, train up them and ensure more output from them.

Reporting: He has to report timely to project manager about project progress.

Client handling: A supervisor will briefly describe about the project to client when he visits the project. He'll fulfill client's query.

Sub-contractor handling: By evaluating sub-contractors, a supervisor will select sub-contractor and assign tasks. He will continually monitor sub-contractors performance and make them understand company policy and operating procedure.

Cost controlling: Identifying variances and reducing wastage by effective management, a supervisor will controll the cost of a project and thus meet the project budget.

Maintaining work environment: By following and enforcing standard procedures and regulations, he'll keep the work environment secure, safe and healthy.
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6 Steps Preparation Before Pouring Concrete

There are lots of works involved before pouring concrete. Many workers work for many hours for making a platform for concreting. They spend many hours for making concrete formwork, many hours for placing reinforcement, finally they make a platform for pouring concrete. But a little mistake will throw all the efforts in vain. So, it is very important to have well preparation before concreting.
 

concrete preparation, pouring concrete 6 steps preparation before pouring concrete


Step-1: Planning
Well planned task is half done before doing. So, planning is very important. When it comes to concreting, even better planning is required. The following plannings are required before you decide to pour concrete-

* Source of concrete- machine mixing or readymix.

If you plan to "prepare concrete by mixture machine" then measure the required quantity of "concrete ingredients". Collect and stack them in a easy to access yard which should be near to mixing place as far as possible.

If you plan to pour concrete by readymix then measure the required concrete volume and place an order to readymix supplier. Request them to supply in specified time and date. Don't forget to tell them required slump and desired concrete strength.

Step-2: Tools and machinaries
You will need-
* Concrete mixture machine (if you plan to mix by machine)

* vibrator (fuel powered or electric powered) - keep two numbers of vibrator nozzle. Because one can be damaged accidently.

* Generator - if there is a possibility of power failure.

* Water pump

* Plastic drum for water reserving.

* Bucket

* Levelling patta

* Hand shovel

* Trowel

* Polythene sheet (if there is possibility of rain).

Check all are in working order.

Step-3: Manpower
If you planned to mix concrete by mixture machine then you need more worker than doing concrete by readymix. For concreting with mixture machine you will need five more workers, one for mixture machine operating, four workers for carrying concrete ingredients. Other than these, you will need labors and masons for carrying mixed concrete, operating vibrator,  levelling and finishing concrete. So, arrange them before concreting.

Step-4: Safety
Ensure safety before concreting. If you are casting a building's slab then hang polythene sheet all around the slab. Because, if there is any building near to your concreting place than that building's wall paint can be spoiled. Arrange gumboots and hand-gloves for workers before starting concrete work.
Make your concreting place easy to access.

Step-5: Services
We often forget about these. Even, during writing this article, I also forgot. But don't forget to check these before concreting. Check all electrical conduits and sanitary and plumbing pipes have been put.

Step-6: Reinforcement and formwork
Check reinforcement once again that those are not displaced.

Finally check formwork. If there are any gap/holes, rectify them. Check supports are intact.

If everything are set you can pour concrete without any tension. The above steps are very important because without proper preparation, concreting work can be delayed. And any delay can hamper you concrete quality and thus the durabity of your the structure. Ultimately, lack of preparation can also increases construction cost.


Over to you...In this post, I described everything about preparation before concreting. What do yo think? Did I miss anything? Please share in comments.
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17 Technical Terms about Reinforcement a Construction Supervisor Should Know


The responsibility of construction supervisor is huge. Quality of work mostly depend on the performance of site-supervisor. So, his role is very important for the quality of a project.

A supervisor must have enough technical knowledge about construction for ensuring quality of construction.

In this post I'll share 17 technical terms about reinforcement in RCC.

17 Technical Terms about Reinforcement a Construction Supervisor Should Know


reinforcement, construction supervisor,

Reinforcement cover
We generally call it clear cover. Clear cover is the distance between reinforcement and outer face of RCC member. This distance varies depending on the RCC member size and location. Common clear cover value of different RCC members are given below:

1. Pile:- 3" (75 mm)

Pile cap:- 3" (75 mm)

Footing:- 3" (75 mm)

Column below ground: 2.5" (62 mm),

Column above ground: 1.5" (37 mm)

Shear wall below ground: 2.5" (62 mm)

Shear wall above ground: 1.5" (37 mm)

Beam below ground: 2.5" (62 mm),

Beam above ground: 1.5" (37 mm)

Slab below ground: 2" (50 mm)

Slab above ground:- 0.75" (20 mm)

Stair: 0.75" (20 mm)

Retaining wall's earth face: 1.5" (37 mm), opposite face: 1" (25 mm).

Door-window lintel: 0.75" (20 mm)

Sunshade: 0.75" (20 mm)


Hook and bend2. Stirrup's hook angle: 135 degree.

3. Stirrup hook length: 9D or, not below  3" (75 mm), (D= dia of bar),

4. End hook of beam reinforcement: 12D

5. End hook of slab top reinforcement: 12D

6. L bend for vertical reinforcement of column: not below 18" (450 mm).

7. Main steel anchorage length for cantilever is 69D.


8. Weight of steel
8 mm dia bar: 0.12 kg/rft,

10 mm dia bar: 0.19 kg/rft,

12 mm dia bar: 0.27 kg/rft,

16 mm dia bar: 0.48 kg/rft,

20 mm dia bar: 0.75 kg/rft,

25 mm dia bar: 1.25 kg/rft,

9. Standard steel bar length: 40 rft.

10. Weight of steel bars can be calculated by this formula, d2/162, result will be in kg/meter, where d is diameter of bar in millimeter.


Reinforcement placing
11. 1st stirrup of beam should be placed within 2" (50 mm) distance from support.

12. Steel bar larger than 36 mm shouldn't be lapped.

13. More than 50% of bars shouldn't be lapped in one place.

14. No lapping shouldn't be placed in tension zone.

15. For one ton steel bars 8 kg binding wire is required.

16. A square column should have minimum 4 numbers of bars and a round column should have minimum 6 numbers of bar.

17. Steel bar size for chair shouldn't be less than 12 mm diameter.


Over to you...
Can you point out anything else about reinforcement which a construction supervisor should know...

 
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7 Preliminary Works to Do Before Starting Construction Project

Plot is selected. Architectural drawings are ready and approved. Structural drawings are ready and approved. All the paper works have been completed properly with government agencies. All the agreements with land owner, contractors and stack holders are completed. Now it's time to start construction.

Before starting construction we have to do some preliminary works which are sometimes called mobilization. These works are very important to smoothly run the future stages of construction.

I pointed out 7 preliminary works to do before starting a construction project.

7 preliminary works to do before starting construction

 
Cleaning: Remove jungle from plot area. If there is any tree in the buildup area, un-rooted them completely. And remove from the plot area.

Levelling: Throughly level the ground. If there is any hole in the ground fill up that properly. Remove excess soil from the plot or fill up the plot by imported soil to take the ground to desired level, if required.

Fencing: Now plot area is cleaned and levelled. It is time to secure the plot area. It can be done by making permanent boundary wall or temporary fencing around plot. Temporary fencing is the more common way. Builder logo or company logo can be setup with fencing for branding. Also, safety signboard can be attached with fence.

Site office: Site office can be temporary or fixed depending on situation. If there is any driver's waiting room or visitor's waiting room or guest waiting room to build later then build that first to use as site office. But that is exceptional. The common practice in this case is temporary site office. You can make it with CI sheet and bamboo or you can use porta cabin as a temporary site office. You should make a toilet which is separated from labour's toilet as you will have many vip clients and visitors during construction period.

Store: The most essential thing in any construction site is store. To keep safe various building materials from un-wanted damage or stolen, make a store before starting construction. Make a separate store for cement because that are huge quantities and that are quickly affected by weathering impact. So the cement store should be protected from weather effect, specially from water.

Labour shed: It is common practice for bangladesh and india that, workers, who work in the construction project stay at site. For them a shed should be made at site with essential facilities like water and power supply and sanitation. Some construction companies have permanent labour accomodation, so they don't need to make shed at site.

Utility connection: As civil construction needs continuous power and water supply, so ensure them first. For water supply, you can connect to city's water supply line, or you can install a deep tubewell. For electricity connection, connect to city's power supply line, or you can keep a generator at site.

One thing should be remembered during placing toilet. Footing of structure often extend beyond floor area. So, during placing toilet, consider footing location so that you don't have to face problem during footing work.

We always facing problem with site office placement due to plot area shortage.

How do you select place for site office? Please share in comment section.
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Concrete Ingredients

Concrete doesn't need any introduction. Because, whereever we go, we see many concrete structures around us. Concrete is a composite material with changeable properties. The ingredients mixing ratio of concrete is variable and depends on the properties of ingredients and mix design. Popular measuring method of concrete ingredients during mixing, is by volume. But the weight measuring method is more accurate. However, concrete is prepared by mixing three basic ingredients.

1. Binding material - cement,
2. Aggregate, and
3. Water.
Concrete ingredient, concrete basic

Binding material: Most commonly used binding material for concrete is portland cement. Other binding materials used for this purpose, are lime, fly ash, silica fume etc. The selection of cement for concrete is depend on the "cement properties".

You can Read more about cement:
* Cement ingredients and their functions
* Types of cement

Aggregate: Two types of aggregates are used in concrete. Coarse aggregate and Fine aggregate.

Coarse aggregate: Big sizes aggregates in concrete are coarse aggregates. The size of it varies between 1/2" to 1.5" depending on concrete mix design. Generally, crushed stone or brick chips are used as coarse aggregate.

Fine aggregate: The smaller size aggregates in concrete are Fine aggregates. The FM (Fineness Modulas) of fine aggregates can be between 1.2 to 2.5 depending on mix design. We use sand as fine aggregate in concrete.

Also Read:
* Properties of aggregate

Water: The most important concrete ingredient is water. Water can decrease and increase the concrete strength depending on its using. Water just starts and continues the chemical reaction of cement. High water content in concrete mix increases the workability of concrete but decreases the strength. On the contrary, low water content increase the concrete strength but makes concrete less workable.

Other than these, there are some other ingredients are used in concrete mix such as Admixture. Those are secondary ingredients and added to give concrete a certain property.

See:
* Admixture and purposes of their using in concrete.

Dear readers, I try my best to keep my articles as informative as possible. And I spend hours to research. So, if this article helps you a little please share with your friends as giving me a thank.
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Types of Concrete

Concrete, a widely used building material in the world. I can't imagine any civil construction without concrete. There are many types of concrete are used in the sector.

  • Normal-strength concrete
  • Light-weight concrete
  • Air entrained concrete
  • High-Strength concrete
  • High performance concrete
  • Self-consolidated concrete
  • Shotcrete
  • Pervious concrete

types of concrete, concrete typesa


Normal-strength concrete
This type of concrete is produced by mixing basic concrete ingredients. Strength of it varies between 10 MPa to 40 MPa. The initial setting-time is 30 to 90 minutes depending on "cement properties" and weather condition.

Light-weight concrete
The unit weight of this type of concrete is less than the concrete made of basic ingredients. Normally unit weight varies from 240 kg/m3 to 1850 kg/m3. The strength of light-weight is 7 MPa to 40 MPa.
 
Air entrained concrete
Air entrained concrete is the fabulous invention in concrete technology. It is produced by mixing air entraining admixture with normal concrete. The strength of this concrete type is lower than normal concrete.

High-Strength concrete
This type of concrete is produced by selecting high quality aggregate, lowering w/c ratio and mixing admixture to concrete. The strength of this, is about 6000 psi.

High performance concrete
This special type of concrete strength can be 10000 psi to 15000 psi. That mean, it is super high strength. And it's also high durable.

Self-consolidated concrete
Its name describe about it. This doesn't need any vibration for compacting. It's compacted by its own weight. That's why it's also called self-compacting concrete. It has the high workability which is measured 650-750 mm on a flow table. That's the reason for its another name, flowing concrete.

Shotcrete concrete
This concrete is applied onto structure or into frame by shooting with a nozzle. This technology uses compressed air to shoot. In this concrete application, placing and compaction undergo at same time due to air force.

Pervious concrete
This concrete contains 15% to 20% voids of its volume when set. These voids allow water to pass through it.

Concrete can be various types depending on mixing process, application methods, mixing compositions, chaseatesistic, performance etc. But the types of concrete, I discussed in this article, isn't based on any specific purpose. Those are the common types of concrete.
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6 Requirements of Good Quality Bricks

For good quality construction works, as constant supervision is required so is required good quality building materials. Thus, for good quality masonry works both "supervision" and quality bricks are required. We'll discuss the requirements of good quality bricks in this post.

brick, construction, civil engineering

6 Requirements of good quality bricks


Followings are the six requirements of good quality bricks -

Size: We commonly use 9.5 x 4.5 x 2.75 inch size of bricks. Whatever brick size you use, they should be regular and uniform. Good quality bricks shouldn't exceed the following tolerances in size -
In length they shouldn't exceed 3mm and in width and height 1.5 mm.

Shape: Shape should be uniform of quality bricks. Edges of them should be sharp, straight and right angle.

Color of bricks: Well brunt brick always have uniform color. That means, good quality bricks should have uniform color. Over burned and less burned bricks lost its uniformity of color on its surface and its strength. So, a good quality brick should have uniform color throughout. It can be red, cherry or copper-colored. Well burned bricks gives metallic ringing sound when struck with one another.

Surface finish: Good quality brick surface should be free from cracks, flaws, air holes and any defect or impurities. Broken surface of good quality bricks should show uniform, compact and fine structure.

Strength: Crushing strength of good quality bricks shouldn't be less than 3.5 N/mm2. Crushing strength is tested in laboratory. We can also test its strength on field.

Quality bricks left no mark when scratched with thumb-nail. In this way, we can guess its hardness.

Good quality bricks shouldn't break when dropped on ground from about two feet height on their flat face in a saturated condition. In this way we can be assured about its strength.

Water absorption: Good quality bricks doesn't absorb water more than 20% of its dry weight when soaked 24 hours in cold fresh water.

As we discussed beginning of this post, quality brick work doesn't depend only good quality bricks. It also need proper supervision. You should read the "quality checklist for good brick works".
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Considering points During Placing Beam Reinforcement

Placing beam reinforcement need some practical knowledge and some theoretical knowledge. A designer designs the beam perfectly. As a construction professional we need to be cautious during beam reinforcement placement. It needs some technical knowledge.

Technorati claim:  DU3JDYKBBYFS

Followings are the considerations during placing beam reinforcement -
Outside beam reinforcement should be within column reinforcement. Beams which are in periphery of slab, should be applied this rule on. See the image below-
beam, reinforcement, building, construction
Lap location: Top bar lapping of beam should be on middle half of beam. Bottom bar lapping should be within "L/4" length of beam from support. But try to avoid lapping as far as possible.

Beam stirrups: During placing beam reinforcement, there is a possibility of displacing stirrups of beam. So, after placing beam reinforcement in position, make sure the stirrups are straight.

Beam and column junction: It is always suggested by structural engineers to put column stirrups within beam and column junction. So, place those before downing the beam reinforcement. Because it's almost impossible to provide column ring after completing beam reinforcement.

These are the most important points (most of us often forget these in time) to remember during placing beam reinforcement.

To know furthermore about beam reinforcement head over to "How to Place Beam Reinforcement". You can also subscribe via "RSS" to get latest update.
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How to Place Reinforcement in Bottom Slab of "UGWT"

Before, we discussed here "considering things during earth excavation of UGWT". After that we wrote about "how to make UGWT's bottom slab". In that post, we discussed general procedure of making UGWT's bottom slab. We didn't show how to place reinforcement in UGWT's bottom slab. In today's post we will discuss about that.

How to Place reinforcement in UGWT's bottom slab


We have a drawing which shows the size and spacing of steel bars for UGWT. But it's not showing how to place steel. See the image below.
under ground water tank
Did you face this problem before? If you faced, this post will give you a solution. If you not faced, yet you should read this post to learn.

Now the core question is - which steel bar should go bottom and in which direction?

Anatomy of drawing: In the above image (that is our drawing), we have 10 mm dia bar @ 6" c/c and 8mm dia bar @ 6" c/c. Obviously 10 mm dia bar is the main bar and 8 mm dia bar is the binder. We know the size of our water tank that is 30'x7'. The water tank section doesn't make any sense that which is placed in short direction of water tank and which is long direction.

In this situation follow the rule discussed below:

As we know the main steel goes along short direction. So we can say the above section of water tank is the short section.

Now lets start placing steel bars. First place 10 dia bars along short direction and place 8mm dia bars on 10 mm dia bar along long direction as specified spacing in the drawing. Now fix the bars with binding wire. Make “L” bend (in construction we call it mutum) in both side of steel bar. After this process we have just finished one net. But our slab reinforcement is double net. So we have to make another net by following same procedure above. But this net is reverse of 1st net.

For making 2nd net, place 8 mm dia bars along long direction and place 10mm dia bars on 8mm dia bars along short direction. Give “L” bend in both ends of bars. As our bottom slab thickness is 10" and clear cover is 3" so “L” bend length should be below 4".

Our bottom slab reinforcement is ready but we have to place vertical wall reinforcement before casting the bottom slab.

Place vertical wall reinforcement as specified dia and spacing. Don't forget to make dowel in the wall's vertical bar. Also place the chamber reinforcement which is 8 mm dia bar shown in the drawing.

Now our UGWT's bottom slab is ready for casting.



If this post helped you a little please share with your friends to help them also to say thanks to me.
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