FAQs |
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| 1. |
What will happen if shape of aggregates used in concrete is not rounded/cubical? |
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If the shape of aggregates used in concrete is not rounded (or) cubical the interlocking of aggregate in concrete will not be proper and strength of concrete will decrease. If the aggregates are elongated (or) flaky the strength of concrete will be seriously affected and concrete will become porous..In UltraTech Concrete the 20 mm & 10 mm aggregates are properly checked for elongation or flakiness and their quantity is restricted within the limits of BIS standards, to get cohesive & durable concrete. |
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2. |
What is workability of concrete? |
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The ease of placing, compacting and finishing of concrete in desired manner is called workability. Normally the workability is measured through slump. More the slump, higher the workability. Low slump leads to difficulties in placing of concrete. Therefore it is required to decide the workability based on experience and site conditions. |
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3. |
How will you ensure that the ingredients of concrete are proper? |
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The right proportion of aggregate, sand, cement, water in concrete are ensured by experience in volumetric proportion. However, in UltraTech Concrete, the mix proportions are designed in a scientific method and proportions are fixed by weighment. Mixing is generally done through high efficiency pan mixers(machine mixing). The number of rotations of the shaft is very important in proper mixing and should be monitored strictly. The material may segregate in case the raw mix is over mixed. Improper mixing may lead to reduced strength. UltraTech Concrete is equipped with computerized batching and mixing plants, to strictly monitor the quality of concrete. The recipe of raw mix design (Cement: Sand: Coarse aggregate: water: admixture) is stored in the computer and the quantities of raw materials are weighed automatically as per the design mix. The water-cement ratio for a particular mix is fixed as per the design, which is kept constant throughout and hence consistency in quality is maintained. |
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4. |
What is the importance of water-cement (w/c) ratio? |
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W/c ratio is very important in making concrete to satisfy the strength & durability criteria of concrete. If w/c ratio is more, the strength of concrete will be reduced due to void formations in concrete. In UltraTech Concrete, w/c ratio is pre-designed through scientific mix design as per BIS specification. The effect of w/c ratio on compressive strength of concrete is as shown in the table below: |
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| Water Cement (w/c) |
0.40 |
0.50 |
0.60 |
0.70 |
0.80 |
| Probable Compressive Strength (%) |
100 |
87 |
70 |
55 |
44 |
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Importance of Water-Cement Ratio: |
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| Factors |
Low w/c ratio |
High w/c ratio |
| Compressive strength |
High |
Low |
| Water permeability |
Low |
High |
| Shrinkage |
Low |
High |
| Water Bleeding |
Low |
High |
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5. |
What is the importance of mixing in concrete ? |
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The mixing of concrete may be compared with Dosa mix. If the ingredients of Dosa are measured & ground properly, the Dosa will be soft, thin, of good taste and non sticky. In the same way, if the ingredients of concrete are properly proportioned and mixed, the quality of concrete will be uniform, cohesive and consistent. In UltraTech Concrete, the mixing is done through turbo mixer, which ensures uniform and consistent quality of concrete. |
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6. |
What is the segregation of Concrete? |
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Segregation is the separation of coarse aggregate from cement paste. It mainly occurs due to excess water in concrete and non-cohesiveness of concrete. In UltraTech Concrete, the well-designed concrete is pumped from the delivery truck to the location where it is being placed through concrete pumps with horizontal and vertical pipelines. The flexible hose pipe attached at the end of pipe line makes the pouring convenient at the point of placing, thus reducing shoveling / dragging and avoiding segregation. |
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7. |
What is bleeding of concrete? |
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Bleeding is the emergence of water to the surface from freshly placed concrete which results in deposition of solids to the bottom during compaction. It can be avoided by proper control of w/c ratio and desired level of compaction. |
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8. |
Why concrete has to be cured? |
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Curing is unfortunately neglected at the construction site. In case of roof slabs, quick drying of surface will lead to plastic shrinkage cracks. Apart from this, if timely curing is not done, the top surface dries to such an extent that hydration process almost stops at the top surface making it weak and porous. Therefore, it is emphasized that curing is the essence of good concrete. |
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9. |
What is plastic shrinkage crack in concrete? |
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During the hydration of cement paste in concrete heat of hydration is produced. This heat dissipates from the surface of concrete leading to formation of cracks on surface of concrete. These cracks are called plastic (or) drying shrinkage cracks. These can be reduced to a great extent by early curing. |
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10. |
What is the importance of testing concrete? |
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The concrete has to be tested to know the strength of concrete at 28 days for each desired grade. Usually the concrete at site is not tested for its strength, workability, yield and other factors that ensure the performance of concrete over a period of time. However in UltraTech Concrete, the samples of concrete are tested for every batch to ensure consistent quality and supply of durable concrete. |
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