Pros and Cons of ready-mix concrete

Ready-mix concrete belongs to a concrete that is formed in a batch plant, on the basis of a predefined engineered mix design. Ready-mix concrete is generally supplied in two ways i.e. the barrel truck or in–transit mixers.

This type of truck supplies concrete in a plastic state to the site. And the volumetric concrete mixer. It supplies the ready mix in a dry state and then blendes the concrete on site.

Given below some pros and cons of ready-mix concrete :-

Pros of ready-mix concrete:

a. With Ready Mix Concrete (RMC), the construction process becomes fast with programmed delivery at site, automated operation with subsequent economy.

b. The costs of labor and site supervision are decreased significantly.

c. RMC maintains uniformity in quality with perfect & computerized control of sand aggregates and water according to mix designs.

d. Formation of RMC facilitates reducing cement wastage because of mass handling.

e. While producing RMC, no pollution occurs.

f. By using RMC in project, project time is curtailed significantly and it leads to huge savings in all phases.

g. Perfect control and economy in applying raw material leads to saving of natural resources.

Cons of Ready-Mix Concrete

Following are the cons of ready-mix concrete:

1. The materials are batched at a main plant, and the mixing starts at that very plant. So the transition time from the plant to the site covers longer distances and becomes complicated. Some sites locate at too remote distance, which may cause risk for ready mix concrete to be useless owing to setting.

2. It will create extra road traffic. Normally, Ready Mix Trucks are bigger in size and may take huge space in the road that will obstruct other traffic. Besides, access roads and site access should have the capacity to bear the heavier weight of the ready-mix truck plus load. (Green concrete is approx. 2.5 tonne per m³.) This issue can be resolved by using so-called ‘mini mix’ companies which employ smaller 4m³ capacity mixers to visit more-restricted sites.

3. Concrete’s constrained time span among mixing and curing signifies that ready-mix should be arranged within 210 minutes of batching at the plant. The time span can be rectified with modern admixtures perfectly, though, the amount and type of admixture that is included with the mix is very crucial.

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Published By

Rajib Dey

www.constructioncost.co

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How batching of concrete is done

Concrete is a multipurpose, long-lasting, eco-friendly, and inexpensive material as well as globally recognized construction material. To produce superior quality concrete, the components of concrete should be calculated properly and perfectly. Once mix design is set, the initial task should be batching materials.

Batching of concrete stands for the method of estimating and mixing necessary concrete ingredients both with weight or volume according to the mix design and implanting them into a mixture to form a consistent quality of concrete.

By perfectly computing all the material applied in the concrete formation, it becomes possible to maintain consistency of proportions in all consequent batches.

Why Batching of Concrete is Important?

Usually, following three types of batching are undertaken for concrete components:

01. Random Volumetric Batching: Batching devoid of any control on the size and shapes of applied containers leads to big errors and deviations like utilizing “ghamellas” i.e. – by tallying numbers of ghamellas. This method is totally unscientific, unrefined and should not be recommended even for a small project.

02. Volume Batching of Concrete: Volume batching of concrete is accomplished with the use of measurement boxes, locally named “farmas or gauge boxes”. Concrete components like aggregates ( Kapachi +Sand) and cement is calculated with farmas or gauge boxes and proper precaution should be maintained to ensure that the farmas or gauge boxes are filled excessively. To calculate the quantity of water, the water meter should be utilized when batching or use cans of water contain fixed volume.

03. Weigh Batching of Concrete: Weigh batching of concrete is accomplished with the use of a weigh batch or the weighing system on the batching plant. On big projects, automatic batching plants are set up to facilitate optimizing quality and uniformity.

Water is very vital material and therefore, maximum water should be used for batching. If the quantity of water is less, the functionality of concrete will be hampered whereas surplus water will minimize the strength of concrete. Water should be computed perfectly in litres.

The selection of batching method is based on the size of job, production rate and standards of batching performance.

Usually batching is performed with volume. Precision in batching is very crucial. It is better to perform weigh batching instead of volume batching. Volume batching is mostly effective where weigh batching is not possible. It is always recommended to incur additional cost for it, because in long term, it saves huge costs.

Note: The quantity of cement should also be calculated by maintaining the precision of ± 2 percent and the quantity of aggregates, admixtures and water should be calculated with a precision of ± 3 percent.

Article Source: gharpedia.com

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Published By

Rajib Dey

www.constructioncost.co

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Brief overview of workability of concrete

The strength & longevity as well as the cost of labor and look of the finished product is greatly impacted by the workability of concrete. The concrete can provide better functionality, if it is easily positioned and compacted consistently devoid of bleeding or Segregation.

The concrete that is not in good working condition should be supported with extra work and endeavor for being compacted in position, also honeycombs &/or pockets are also found in finished concrete.

Definition of Workability: Concrete workability defines how smoothly freshly mixed concrete is amalgamated, arranged, compacted and finished by keeping the conformity as it is. Workability refers to a property that directly affects strength, quality, appearance, as well as the cost of labor for placement and finishing operations.

The workability is impacted with the following factors :

1. Water content in the concrete mix
2. Amount of cement & its Properties
3. Aggregate Grading (Size Distribution)
4. Nature of Aggregate Particles (Shape, Surface Texture, Porosity etc.)
5. Temperature of the concrete mix
6. Humidity of the environment
7. Mode of compaction
8. Method of placement of concrete
9. Method of transmission of concrete

The workability of concrete can be improved in following ways :-

1. Raise the proportion of water/cement
2. Raise size of aggregate
3. Apply well-rounded and smooth aggregate rather than asymmetrical shape
4. Rise the mixing time
5. Enhance the mixing temperature
6. Employ non-porous and saturated aggregate
7. Include air-entraining mixtures

The most recognized method for measuring the workability of concrete is Slump Test.

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Published By

Rajib Dey

www.constructioncost.co

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