The following ingredients are necessary for obtaining good concrete in construction field. CEMENT The Cement grade and brand of cement should confirm IS 456: 2000 standards and is recommended by the respective project consultant. Each consignment of cement delivered to the project site must obtain Manufacturers test…
How to Make a Concrete? :
The following ingredients are necessary for obtaining good concrete in construction field.
Storing and stacking of cement :
CEMENT STACKING : Fig 1 and 2 : Right way of staking cement at 10 bags height below yellow line
Maintain proper records and see that “first come cement in and first out rule” while issuing cement bags.
Before issuing for work, ensure the cement is tested in-house for consistency, setting time, and strength.
AGGREGATE FOR CONCRETE :
Coarse Aggregates :
Fine Aggregates :
Tools required for Concreting :
How to make Concrete? Mixing of Concrete : IN-SITU MIXING (Mixing at site)
Concrete mixer :
Concrete mixer :
FIG 3: CONTROL ON WATER – CEMENT RATIO
Loading of concrete into the mixer :
Minimum cement content :
Minimum cement content required per cum of concrete is as per the following below :
Points to be remember for concreting :
RCC works :
Measuring boxes :
FIG 4 : CONCRETE MIXING IN PROCESS
USING MIXER WITH HOPPER
FIG 5 : RESIDENCE ROOF CONCRETING
RMC using Batching Plant
If we want go for Ready Mix Concrete (RMC) at project site, many factors are required to be considered, and the same thing will be explained in detail, shortly in coming articles.
QC Engineer should plan and decide the required quantity, and order to be placed well in advance, strategy should be worked out in such a way that at least 1 load of 6 cum for every 10 to 15 minutes duration so that concrete is delivered to the site without any hassle.
- Before exit transit mixer from project site, Check the empty vehicle for preset concrete in the drum. This will reduces the quantum of concrete received. Check always Concrete should be received with a DC and data cycle sheet clearly showing grade, quantity, water cement ratio, slump measured, and weightage of cement, date and time of manufacturing, quantity of additive added, weight of other ingredients of concrete.
- Caution: Do not accept concrete after lapse of 3 hours’ time from batching plant to project site including complete unloading of concrete. (Check the leaving time of truck from the batching plant in delivery challan).Do not alter the concrete mix by adding additive, water, and cement without prior permission from the QA/QC Engineer.
For Pumpable concrete, the Slump recommended for RMC mix is 100 mm to 125 mm and can go up to 150 mm in certain cases.
Concrete Pump, Pipe arrangement and maintenance:
- Concrete pump to be located on horizontal, hard and even surface, to see that easy flow of material to the required place of discharge.
- The horizontal section of pipe should be at least 6 meters before the vertical bend is put.
- The pipe to be reduced to the minimum length, to prevent frictional losses and over pressure exerted on the pump.
- Caution: Always keep in mind that, the pipeline should not be supported on shuttering beam sides, rather it should have its own vertical independent segment. If this is not taken care, the vibrations due to pumping will affect or displace shuttering works causes excessive damages.
- Before supplying actual concrete, always pump rich cement slurry, to lubricate the inner surface of the pipes.
Choking of pump:
- Due to practical problems, or any reason, In case of subsequent supply is not reaching project timely, keep the current transit mixer in running condition, till the next mixer arrives at site. This will avoid choking problem of pipeline, keeping in idle the pump, for long duration.
- Caution: Avoid reverse stroke to clear a choke in pump. The slurry gets flushed out and the problem gets compounded.
- Do not bend the flexible end pipe too much during concreting.
- In unconfined and congested areas, where pipe line is not possible to reach, do not unload directly from the pipe, all shuttering material gets spoiled and alignment may be disturbed. Use Pans and spades and do concrete manually.