Dosage: Typical air entrainment ranges from 5% to 8% of the volume of concrete. Water reducers have become so important in concrete, that they could be considered the "fifth" ingredient. They can be used to: (1) increase slump, (2) lower the water-cement ratio, or (3) reduce cement content.

What is the ratio of admixture in concrete?

The percentages of Sikament-163, which are added in concrete mixture, are 0 % (normal concrete), 0.75 %, 1 %, 1.25 %, 1.5 %, 1.75 %, 2 % and 2.5 % by cement weight. The research is conducted using nine test specimens for each percentage of Sikament-163 with the same slump.

How is concrete admixture percentage calculated?

Calculation of Sand & Coarse Aggregate Quantities:

Admixture = 1.2 % by weight of cement = 5.064 kg.

What is the maximum percentage of admixture in concrete?

From Figure 3, we can observe that maximum or optimum dosage for the admixtures is 1.0% i.e, 1000 ml/100kg of cement which is obtained from specimen S4. The compressive strength is decreasing if the dosage of SP is fluctuating i.e, higher or lower from this limit.

What is admixture used in concrete?

Admixtures are additions to a concrete mix that can help control the set time and other aspects of fresh concrete. Common admixtures include accelerating admixtures, retarding admixtures, fly ash, air entraining admixtures, and water-reducing admixtures.

Admixture used in concrete | Civil Engineering interview questions

Why is pozzolana added to cement?

What does a pozzolan do in the concrete? A. ... Pozzolans reduce bleeding because of fineness; reduce the maximum rise in temperature when used in large amounts (more than 15% by mass of cementitious material) because of the slower rate of chemical reactions; which reduce the rise in temperature.

What are the four main properties of concrete?

• Mechanical strength, in particular compressive strength. The strength of normal concrete varies between 25 and 40 MPa. ...
• Durability. ...
• Porosity and density. ...
• Fire resistance.
• Thermal and acoustic insulation properties.
• Impact resistance.

Is concrete a code?

IS: 456 – code of practice for plain and reinforced concrete. IS: 383 – specifications for fine and coarse aggregate from natural sources for concrete. IS: 2430 – methods of sampling. IS: 4082 – specifications for storage of materials.

What is meant by no fine concrete?

No-fines concrete is obtained by eliminating the fine material sand, from the normal concrete mix. The single-sized coarse aggregates are surrounded and held together by a thin layer of cement paste giving strength of concrete. The advantages of this type of concrete are: Lower density.

What are the test for admixture?

Test for Compressive Strength: At least three specimens shall be tested for each type of concrete and each age of testing. Compressive strength shall be determined as given in IS 516. Test for Flexural Strength: At least three specimens shall be tested for each type of concrete and each age of testing.

Why is admixture used?

Producers use admixtures primarily to reduce the cost of concrete construction; to modify the properties of hardened concrete; to ensure the quality of concrete during mixing, transporting, placing, and curing; and to overcome certain emergencies during concrete operations.

What happens if concrete slump is too high?

As you increase the amount of water in a mix, you also increase the porosity of the hardened concrete. ... Excessive slump also can result from accidentally adding too much water-reducing admixtures or super-plasticizers to a mix. This can result in aggregate segregation and a serious loss of strength.

What is the ratio of water in concrete?

Typically, a mix is about 10 to 15 percent cement, 60 to 75 percent aggregate and 15 to 20 percent water. Entrained air in many concrete mixes may also take up another 5 to 8 percent.

What are the factors affecting mix properties?

• Compressive strength.
• Workability.
• Durability.
• Maximum nominal size of aggregate.
• Grading and type of aggregate.
• Quality Control.

What is meant by workability of concrete?

Workability of Concrete is a broad and subjective term describing how easily freshly mixed concrete can be mixed, placed, consolidated, and finished with minimal loss of homogeneity.

Where is no fine concrete used?

The principal applications of no-fines concrete are for load-bearing cast-in-place external walls of single story and multistory housing, small retaining walls and as a dampproofing subbase material for concrete floors cast on grade.

Which of the following is no fine concrete?

Concrete Technology Questions and Answers – No Fines Concrete, High Density Concrete. This set of Concrete Technology test focuses on “No Fines Concrete, High Density Concrete”. Explanation: No fines concrete is one type of light weight concrete.

What is a fine concrete mix?

It includes gravel, crushed stone, sand, slag, recycled concrete and geosynthetic aggregates. ... - Fine aggregates are usually sand or crushed stone that are less than 9.55mm in diameter. • Typically the most common size of aggregate used in construction is 20mm. A larger size, 40mm, is more common in mass concrete.

What is the code for concrete?

The ACI 318, “Building Code Requirements for Structural Concrete and Commentary,” is the document that presents the code requirements for design and construction of structural concrete that are necessary to ensure public safety.

What are the grade of cement?

• Ordinary Portland Cement 33 Grade. ...
• Ordinary Portland Cement 43 Grade. ...
• Ordinary Portland Cement 53 Grade. ...
• Portland Slag Cement (PSC) ...
• Coloured Cement: White. ...
• Portland Pozzolana Cement (PPC)

Is code 53 a grade of cement?

For 53 grade cement, IS code used to be IS 12269.

What is the most important property of concrete?

The compressive strength of concrete is considered one of the most important structural properties it has. As an industrial standard, concrete is classified by different grades. These grades are based on the compressive strength of the material when a specimen of it is made into a cube or a cylinder.

What are the disadvantages of concrete?

• Compared to other binding materials, the tensile strength of concrete is relatively low.
• Concrete is less ductile.
• The weight of compared is high compared to its strength.
• Concrete may contains soluble salts. Soluble salts cause efflorescence.

Is concrete waterproof?

Concrete is inherently water-resistant, so it is an ideal construction material for structures such as basements and bridges. ... With a higher water/cement ratio, the concrete will become more porous.