What is an air entraining agents? Give some examples. What is efflorescence in concrete structure?
Air entraining concrete is made by mixing a small quantity of air entraining agent or by using air entraining cement. These air entraining agents incorporate millions of non-coalescing air bubbles, which will act as flexible ball bearing and will modify the properties of plastic concrete regarding workability, segregation, bleeding and finishing quality of concrete. It also modifies the properties of hardened concrete regarding its resistance to frost action and permeability.
The following types of air entraining agents are used for making air entrained concrete:
Efflorescence:- Efflorescence is caused when soluble salts and other water dispersible materials come to the surface of concrete and mortars. Its induced by low temp. moist conditions, condensation, rain, dew and water added to the surface of fresh concrete to assist troweling.
How standard consistency test is done on cement? Explain the procedure briefly.
What are flaky and elongated aggregates? How can the shape of aggregate influence strength of concrete? Following is the result of a sieve analysis of 500 gm aggregate:
IS sieve size | 10 mm | 4.75 mm | 2·36 mm | 1·18 mm | 600 micron | 300 micron | 150 micron | lower than 150 micron |
Weight retained in gm | 0 | 10 | 50 | 50 | 95 | 175 | 85 | 35 |
Find out the 'Fineness Modulus' of the sample
How can permeable foundations affect the stability of weirs?
What are the Classification of irrigation projects.
What is groundwater hydrology and its significance?
How does sediment accumulation affect the performance of headworks?
Describe different types of canal lining materials.
What do you understand by the term "Duty" ?
What is the hydrologic cycle?
What is reinforced concrete?