Discuss plasticizers and superplasticizers, indicating their purpose. Name some products and their dosage for use as plasticizers and superplasticizers.
PLASTICIZER :- Plasticizers is used mainly to fluidity the mix and improve the workability of concrete, mortar or grout. Plasticizers are high range water – reducers. When plasticizers are used they get absorbed on the cement particles and form a thin sheath. This thin sheath inhibits the surface hydration reaction between water and cement.
SUPERPLASTICIZERS:- They are high range water reducers used for producing self compacting self strength and high performance concrete.
Discuss the role of Gel-space ratio. How can it be determined? Calculate the gel-space ratio and theoretical strength of a sample of concrete made with 500gm of cement with 0.5 w/c ratio on full hydration and 40% partial hydration. Discuss the factors which influence creep in concrete?
Explain Kelly Ball to measure the workability of concrete. Mention the limitation of the test.
Give the physical characteristics of 53 grade OPC.
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