METAKAOLIN

 INTRODUCTION

Concrete is consumed on the large scale each day over the globe. Cement is a key ingredient of concrete. But study says for each tonne of cement, there is approx 0.8 to 1 tonne of carbon dioxide emitted [Rubenstein, 2012].Taking into consideration the current scenario, minimizing the impact on environment and looking after energy requirements is an important factor for sustainable development in concrete production. Using alternative materials, or their mixes with cement, can be efficient way to use the industrial waste products.

Metakaolin (a calcined clay) comes out to be an effective solution for this problem. In this blog we will explore the use of Metakaolin as partial substitute of cement in concrete, mortor.

WHAT EXACTLY IS METAKAOLIN?

Metakaolin(METAKAOLIN) is basically calcinated, or dehydrated kaolin clay in simple terms. Kaolinite is a clay mineral, also called as kaolin clay or china clay, chemical formula [Si4]Al4O10(OH)8.nH2O (n=0 or 4). It is majorly produced in countries such as the USA, Brazil, Turkey, UK, etc. 

Kaolin clay is heated, calcinated at a high temperature, about 600-800°C. The layered structure of kaolin is damaged due to dehydration to form a transient phase with poor crystallinity which forms the powder called Metakaolin.

Dehyroxylation of kaolin clay gives METAKAOLIN:

          Al2O3⋅2SiO2⋅2H2O → Al2O3⋅2SiO2 + 2H2O↑

C

Metakaolin, Al2O3.2SiO2 amorphous alumina-silicate, is not a naturally occurring product. It requires energy to be produced, though which is much less compared to that required for cement. 

What makes metakaolin most interesting is it’s pozzolanic activity. Pozzolanic activity, in simple terms, is the ability of METAKAOLIN to react, in the presence of water, with calcium hydroxide(Ca(OH)2) to form hydrated silicate gel hydrate products possessing cementitious properties. Fly ash, silica fume, ground granulated blast furnace slag are some examples of pozzolanic materials. Market size of usage of Metakaolin sees a steady rise over the years.

Mechanical Properties of Metakaolin 

1. Compressive Strength 

Metakaolin being a Pozzolanic material, when added in Concrete enhances the compressive strength of concrete. As the Metakaolin content increases the compressive strength of Concrete increases. But this is upto 15% replacement, addition of Metakaolin further decreases strength slightly. 

2. Split Tensile Strength

The split tensile strength of concrete is increased when cement is replaced with Metakaolin. The split tensile strength is maximum at 15% of replacement.

3. Flexible Strength

The flexure strength of concrete is increased when cement is replaced with Metakaolin. The flexure strength is maximum at 15% of replacement.

WHY TO GO FOR METAKAOLIN

When used to replace cement at levels of 5% to 10 % by weight, the concrete produced is generally more cohesive and less likely to bleed. As a result pumping process requires less effort. The compressive strength of hardened concrete is also increased at this level of replacement. This results in improvements to resistance of the hardened concrete to attack by sulphates, chlorides ions and other aggressive substances, such as mineral and organic acids.

 ADVANTAGES OF METAKAOLIN IN CONCRETE 

1. Increased compressive and flexural strengths.

2. Reduced permeability ( including chloride permeability).

3. Increased resistance to chemical attack.

4. Increased durability.

5. Enhanced workability and finishing of concrete.

6. Reduced shrinkage, due to “particle packing” making concrete denser.

Metakaolin in concrete thus can be used to build strong precast compound walls, partition walls, compound walls as also low cost housing. Metakaolin is thus an economical alternative to cement, better in many aspects. Market size of usage of Metakaolin sees a steady rise over the years.

Metakaolin is certainly a material of the future, it should be used smartly.

CREDITS:

Vardhan Mundada (112103091) FY Computer Engineering

Aarya Kulkarni(112107001) FY Electronics and Telecommunication Engineering.

RESOURCES:

https://www.researchgate.net/publication/283298809 Properties of Metakaolin Concrete - A Review by Farzad Mohgaddam, Rasiah Sri Ravindrarajah and Vute Sirivivatnanon

Paper on Metakaolin by Jamal Khatlb, Oussama Baalbakl and Adel Elkordi

Partial Replacement of Cement with Metakaolin in high strength concrete by Durga Jagarrapu

NOTE:

This blog is meant for educational purposes only. We do not own any Copyrights related to images and information, all the rights go to their respective owners. The sole purpose of this blog is to Educate, Inspire, Empower, and create awareness in the viewers. The usage is non-commercial(Not For Profit) and we do not make any money from it.

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