Civil Engineering - Building Materials - Discussion

OPC's initial setting time is 30 MIN.

And final setting time is 600 MIN.

The correct answer is 120 minutes.

Lime-Pozzolana (120 minutes): This mixture has a slower chemical reaction compared to standard Portland cement. As per standards like IS 4098, the initial setting time is generally specified as two hours (120 minutes) to allow the slow pozzolanic reaction between lime and silica to begin.

30 minutes: This is the minimum initial setting time for Ordinary Portland Cement (OPC) and Portland Pozzolana Cement (PPC).
60 minutes: This is typically the minimum initial setting time for Low Heat Cement.
90 minutes: While some specific masonry cements or asbestos cement products might have a 90-minute requirement, it is not the standard for general lime-pozzolana mixtures.

Answer: The initial setting time of lime-pozzolana is 120 minutes because the reaction between lime and pozzolanic materials is relatively slow compared to standard cement hydration.

I am not getting it, Give me the explanation.

Pozzolana material particles size is less than 90micron, it does not have any cementing property but shows when it contact with water due to overgrinding (i.e less than 90micron) its rate of hydration increases but less heat of hydration so it shows large initial setting time but in question lime-pozzolana (it means it is a gauged cement) lime also show setting property also some time addition of water.

Aluminum has a quick setting quality when mixed as raw material then how high alumina cement has more setting time as compared to opc, Even the aluminum amount is high.

What is the setting time of Rapid hardening cement?

The calcium hydroxide reacts with the carbon dioxide in the atmosphere to give calcium carbonate that gains cementing properties (Carbonation) as their is low CO2 in air thats why it takes Longer time to Set than OPC which uses water for Setting ! And probably that is why Lime Cement is not used in Under water Structures due to Absence of C02.

What is the initial and final setting time of RHC?

Initial setting time should be less than 70 mins.

Why it's initial setting time more than to opc?