Brief explanation of Cement Hydration Process

This construction video tutorial provides useful information for the students who will appear in SSC and JE exam. The video is presented by the renowned civil engineer Mr. Parag Pal and it sheds light on cement hydration process. Mr. Pal briefly explains the term rate of heat liberation throughout pouring of concrete.

Before delve into the video, first learn the definition of hydration :-

When series of unchangeable exothermic chemical reactions occur among cement and water, it is defined as hydration.

With existence of water, the silicates and aluminates develop the products of hydration which in due course form a rigid (solid) and hard mass i.e. the hydrated cement paste.

Production of hydration products ultimately results in stiffening (loss of adaptability), setting (consolidation), hardening (strength gain).

Hydration process is ceaseless still the heat and moisture exist in the cement.

To gather sufficient knowledge on the fundamentals of hydration is very important for the following reason :-

Assure the strength and longevity of concrete.

Identify and alleviate the stresses to resist cracking.

Recognize the significance of superior curing and construction practices.

Go through the following video tutorial to learn the detail hydration process.

Read more

~~~~~~~~~~~~~~~~~~~~~~~~

Published By

Rajib Dey

www.constructioncost.co

~~~~~~~~~~~~~~~~~~~~~~~~

Calculation of Cement and Sand Quantity for Plastering

The ratio and all calculations given below are according to the requirement of 12mm thick plastering.

Plastering, as we all know, removes imperfection of external walls along with maintaining the line level and the alignment. Generally, plastering is defined as a protective surface for walls. It can be many a type depending on the materials it uses such as cement plaster, gypsum plaster and lime plaster. These are the common types of plastering that are required for home construction.

Cement plaster has two main materials in its core – cement and sand. The right proportion is required to get the best outcome you expected. This plaster removes imperfections from both inner and outer walls of the construction. Knowing the right proportion is an important factor in the making the paste or mortar perfect for the walls.

The list below contains the ratio between cement and sand that you need to maintain as per the application.

• Cement mortar ratio 1:3 - this mortar mix is not used in general applications. It can be used as a repair mortar when they are combined with a waterproofing or bonding agent.
• 1:4 – for ceiling and external plaster.
• 1:5 – the ratio proved to be good as brickwork mortar. It is also good for internal plaster.
• 1:6 – this ratio can be maintained for internal plaster.

 Calculate Cement and Sand Requirement for Cement Plastering:

Calculating the quantities of cement, sand and water depends on a few parameters. These bring out the logic why you need to maintain the ratio.

• Volume of plaster requirement: the volume of plaster can be calculated by multiplying the area of the plaster and the thickness of the plastering (in this case – 12mm)
• Mix Ratio of plaster: deciding the Mix Ratio of plastering contains complex calculation. It indicated the ratio of the volume of cement to sand. Mix ratio of plaster 1:4 means that the mixture has one part cement and 4 parts sand.

For calculating quantity, generally two methods have been applied –DLDB method and Empirical method. These two processes include steps required for a logical distribution of the materials. The calculations and measurements used in this methods based on the quantity of the materials.

For further discussion, read www.onlinecivilforum.com

Read more

~~~~~~~~~~~~~~~~~~~~~~

Published By

Rajib Dey

www.constructioncost.co

~~~~~~~~~~~~~~~~~~~~~~

Setting Process of Cement

The reaction of cement starts immediately when the water is mixed. In it’s pure and finely ground form, it is extremely sensitive to water. Out of the three main compounds of cement, i.e. C3A, C3S, C2S, reacts quickly with water. They produce a jelly-like mixture that starts solidifying. This changing action from fluid to solid is called ‘Setting’ (not ‘hardening’).

In the next stage of hydration, cement paste starts hardening itself to the reaction of C3S and C2S with water. After that it become more harden and dominant. Once initial stiffing has taken place, it should be hardened or gain strength as soon as possible so the risk of frost damage in frozen climate is minimized. The exact timing should always be followed.

“Initial setting time” is defined the period elapsing between the times when water is added to the cement and the required section fails to pierce the test block to a depth from the bottom of the mould.

“The final setting time” is defined as the period elapsing between the time when water is added to cement and the time at which the needle of certain section with required attachment makes an impressive on the test block.

The compressive strength test is based on two functions to fulfill. 1. Final check on the quality of the cement. 2. In case of any doubt, it also helps to classify the cements according to their strength.

The difference between setting and hardening cement is: cement is said to harden when the paste further reacts with water into action. Hardening is associated with the development of strength.

Source: theconstructor.org

~~~~~~~~~~~~~~~~~~~~~~~~

Published By

Rajib Dey

www.constructioncost.co

~~~~~~~~~~~~~~~~~~~~~~~~