Curing and Finishing Concrete

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Questions and Answers

What is the purpose of brooming or tining in concrete?

To reduce the volume stability of concrete

To accelerate the curing process

To improve the strength of concrete

To produce a slip-resistant surface (correct)

What is the primary goal of curing concrete?

To allow hydration of cement to continue (correct)

To reduce the cost of concrete

To improve the appearance of concrete

To increase the permeability of concrete

What is the benefit of curing concrete in terms of durability?

It reduces the durability of concrete

It increases the durability of concrete (correct)

It has no effect on the durability of concrete

It only affects the abrasion resistance of concrete

What is the purpose of sealing in the mix water during curing?

To reduce the loss of mixing water from the surface Signup and view all the answers

What is the method of curing that involves supplying heat and additional moisture?

Accelerated curing Signup and view all the answers

What is the suitable method for curing horizontal surfaces such as pavements and floors?

Ponding and immersion Signup and view all the answers

What is the result of not curing concrete properly?

Reduced strength and durability Signup and view all the answers

What is the benefit of curing concrete in terms of volume stability?

It improves the volume stability of concrete Signup and view all the answers

What is the name of the test that is commonly used to measure the consistency of concrete?

Slump Test Signup and view all the answers

What is the limitation of Slump Test?

It does not measure all factors contributing to workability Signup and view all the answers

What is the internal dimension of the bottom diameter of the metallic mould used in Slump Test?

20 cm Signup and view all the answers

What is the name of the slump type where the concrete collapses completely?

Collapse Slump Signup and view all the answers

What is the indication of a collapse slump?

The mix is too wet or it is a high workability mix Signup and view all the answers

What is the name of the test that is used to measure workability of concrete?

All of the above Signup and view all the answers

What is the shape of the metallic mould used in Slump Test?

Frustum of a cone Signup and view all the answers

What happens in a shear slump?

The top portion of the concrete shears off and slips sideways Signup and view all the answers

What is the maximum temperature difference between the curing water and the concrete to prevent thermal stresses?

11°C (20°F) Signup and view all the answers

What is the primary purpose of fogging and sprinkling in concrete curing?

To reduce evaporation of moisture Signup and view all the answers

What is the minimum relative humidity required at the concrete surface for proper curing?

80% Signup and view all the answers

What is the minimum duration of the curing period for concrete slabs on ground and structural concrete above 5°C?

7 days Signup and view all the answers

What type of materials are used in liquid membrane-forming compounds for concrete curing?

Waxes, resins, chlorinated rubber, and other materials Signup and view all the answers

Why is it important to protect concrete from freezing temperatures?

To prevent damage from ice formation Signup and view all the answers

What factors influence the duration of the curing period for concrete?

All of the above, plus required strength and concrete member size Signup and view all the answers

What is the purpose of using impervious paper, plastic sheets, and membrane-forming compounds in concrete curing?

To prevent moisture loss and retain humidity Signup and view all the answers

What is the purpose of the hammer in the workability test?

To measure the depth of the hammer penetration Signup and view all the answers

What is the result of segregation in concrete?

Weaker and less durable Signup and view all the answers

What is the ideal condition of the concrete to avoid segregation?

Neither too wet nor too dry Signup and view all the answers

How long should the concrete be mixed in a transit mixer?

At least two minutes Signup and view all the answers

What is the type of slump that occurs when a cone of concrete slides down an inclined plane?

Shear slump Signup and view all the answers

Why should the concrete be placed as soon as possible?

To avoid segregation Signup and view all the answers

Why is it necessary to repeat the slump test?

If a shear or collapse slump is achieved Signup and view all the answers

How should the concrete be poured when placing it straight from a truck?

Vertically Signup and view all the answers

What is the cause of a shear slump or collapse slump?

Both A and B Signup and view all the answers

What is the maximum height from which the concrete should be allowed to fall?

One-and-a-half meters Signup and view all the answers

What is the purpose of compacting the concrete with a poker vibrator?

To remove air pockets from the concrete Signup and view all the answers

What is the purpose of the slump test?

To ensure uniformity of concrete batches under field conditions Signup and view all the answers

What happens when the pin is removed from the hemisphere hammer?

The hammer will sink into the concrete Signup and view all the answers

What is the significance of an increase in slump?

The moisture content of aggregate has increased Signup and view all the answers

What is the term for the separation of the constituent materials of concrete?

Segregation Signup and view all the answers

What is the advantage of the slump test on site?

It checks for day-to-day variation in materials Signup and view all the answers

What is the only type of slump used in various tests?

True slump Signup and view all the answers

What is the consequence of a shear slump or collapse slump?

The mix lacks cohesion Signup and view all the answers

Study Notes

Curing Concrete

Curing is the process of maintaining a satisfactory moisture content and temperature in concrete to develop desired properties.
Proper curing improves strength, volume stability, permeability resistance, and durability of concrete.
Curing methods include:
Supplying additional moisture through ponding, spraying, or fogging
Sealing in the mix water using impervious paper or plastic sheets, or applying membrane-forming curing compounds
Accelerated curing using heat and additional moisture

Curing Period and Temperature

The curing period depends on factors such as cement type, mixture proportions, required strength, and ambient conditions.
For concrete slabs on ground and structural concrete, the minimum curing period is 7 days for ambient temperatures above 5°C.

Measuring Workability

Slump test is a commonly used method to measure consistency of concrete, but it has limitations.
Types of slump include collapse slump, shear slump, and true slump.
True slump is the only slump used in various tests and indicates the consistency of concrete.

Slump Test

The slump test apparatus consists of a metallic mold, scale, and tamping rod.
The test is used to ensure uniformity of different batches of similar concrete and to ascertain the effects of plasticizers.

Segregation

Segregation is the separation of constituent materials of concrete, leading to weaker, less durable concrete with a poor surface finish.
To avoid segregation, it is essential to maintain the correct consistency, mix properly, and handle the concrete carefully during transportation and placement.

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Description

This quiz covers the processes of curing and finishing concrete, including brooming and tining, to achieve a slip-resistant surface and desired properties.