Question

discuss this please

1. The relationship between the fineness of cement and the resistance to concrete compression.,
2. The maternal heat rate of five types of Portland cement.
3. The development of resistance to pure compounds paste in cement
4, the rate of maternal heat rate, originally, types of Portland cement

Answer 1

Q1).

The 28-day compressive strength of concrete, with or without entrained air, increases with an increase in cement fineness. The difference in compressive strength due to difference in fineness of cement is considerably less at 1 year's age.

Source :- researchgate.net

Q). 2

TYPE 1 (Ordinary Portland) :- 90-120 Cal/gm at 28 days

TYPE S (Slag Cement) :- 75-90 Cal/gm at 28 days

TYPE 3 (Rapid Hardening) :- 100-135 Cal/gm at 28 days

TYPE 4 (Low Heat) :- Not more than 75 Cal/gm at 28 days

TYPE 5 (Sulfate Resisting) :- 75-90 cal /gm at 28 days

Q3.

To simplify the hydration process, chemical reactions between the various compounds in Portland cement and water are described in five stages.

Stage (1): Initial reactions

several dissolution and hydration reactions

reactions of C3A with gypsum

duration 10 – 20 minutes after addition of water

Stage (2): Induction phase

low reaction rates

Ettringite hinders C3A reaction

duration 2 – 4 hours at 20 °C

transporting, casting and finishing of concrete

setting begins at the end of this phase

Stage (3): Accelerating phase

increasing reaction rate

Beginning of C3S hydration

Compressive strength growth begins

Duration from 5 – 10 hours after addition of water

Stage (4): Decelerating phase

Products generated during hydration of C3A are attached onto cement particles

Hydration products are larger than clinker mineral particles  

water space around particles is filled up

reaction rate decreases

C3A reaction peak noticed after gypsum is consumed

Ettringite begins to decompose to monosulfate

Stage (5): Steady state (can continue for years) l

Belite (C2S) dissolves and reacts more slowly than alite (C3S).  

Belite reactions also produce C-S-H and CH, forming a solid

The longer the cement in concrete hydrates (that is, belites and any remaining alites react with water), the greater the concrete’s strength and the lower the permeability.

Q4.

source :- researchgate.net

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