42 Questions
What is the purpose of brooming or tining in concrete?
To produce a slip-resistant surface
What is the primary goal of curing concrete?
To allow hydration of cement to continue
What is the benefit of curing concrete in terms of durability?
It increases the durability of concrete
What is the purpose of sealing in the mix water during curing?
To reduce the loss of mixing water from the surface
What is the method of curing that involves supplying heat and additional moisture?
Accelerated curing
What is the suitable method for curing horizontal surfaces such as pavements and floors?
Ponding and immersion
What is the result of not curing concrete properly?
Reduced strength and durability
What is the benefit of curing concrete in terms of volume stability?
It improves the volume stability of concrete
What is the name of the test that is commonly used to measure the consistency of concrete?
Slump Test
What is the limitation of Slump Test?
It does not measure all factors contributing to workability
What is the internal dimension of the bottom diameter of the metallic mould used in Slump Test?
20 cm
What is the name of the slump type where the concrete collapses completely?
Collapse Slump
What is the indication of a collapse slump?
The mix is too wet or it is a high workability mix
What is the name of the test that is used to measure workability of concrete?
All of the above
What is the shape of the metallic mould used in Slump Test?
Frustum of a cone
What happens in a shear slump?
The top portion of the concrete shears off and slips sideways
What is the maximum temperature difference between the curing water and the concrete to prevent thermal stresses?
11°C (20°F)
What is the primary purpose of fogging and sprinkling in concrete curing?
To reduce evaporation of moisture
What is the minimum relative humidity required at the concrete surface for proper curing?
80%
What is the minimum duration of the curing period for concrete slabs on ground and structural concrete above 5°C?
7 days
What type of materials are used in liquid membrane-forming compounds for concrete curing?
Waxes, resins, chlorinated rubber, and other materials
Why is it important to protect concrete from freezing temperatures?
To prevent damage from ice formation
What factors influence the duration of the curing period for concrete?
All of the above, plus required strength and concrete member size
What is the purpose of using impervious paper, plastic sheets, and membrane-forming compounds in concrete curing?
To prevent moisture loss and retain humidity
What is the purpose of the hammer in the workability test?
To measure the depth of the hammer penetration
What is the result of segregation in concrete?
Weaker and less durable
What is the ideal condition of the concrete to avoid segregation?
Neither too wet nor too dry
How long should the concrete be mixed in a transit mixer?
At least two minutes
What is the type of slump that occurs when a cone of concrete slides down an inclined plane?
Shear slump
Why should the concrete be placed as soon as possible?
To avoid segregation
Why is it necessary to repeat the slump test?
If a shear or collapse slump is achieved
How should the concrete be poured when placing it straight from a truck?
Vertically
What is the cause of a shear slump or collapse slump?
Both A and B
What is the maximum height from which the concrete should be allowed to fall?
One-and-a-half meters
What is the purpose of compacting the concrete with a poker vibrator?
To remove air pockets from the concrete
What is the purpose of the slump test?
To ensure uniformity of concrete batches under field conditions
What happens when the pin is removed from the hemisphere hammer?
The hammer will sink into the concrete
What is the significance of an increase in slump?
The moisture content of aggregate has increased
What is the term for the separation of the constituent materials of concrete?
Segregation
What is the advantage of the slump test on site?
It checks for day-to-day variation in materials
What is the only type of slump used in various tests?
True slump
What is the consequence of a shear slump or collapse slump?
The mix lacks cohesion
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.
This quiz covers the processes of curing and finishing concrete, including brooming and tining, to achieve a slip-resistant surface and desired properties.
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