Geopolymer Concrete - best eco-friendly concrete in future

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Today’s topic is Geopolymer Concrete. Many may hear this word, many will hear the first time.

So, if you go to Google and search for this word, you will see many articles related to geopolymer, but there it has been explained geopolymer very unmanageable and difficult way.

Now, this article is totally different from them.

Actually, I always try to be as simple as possible because I want my all article to be read and understand by all types of students. And in this article, I have followed the same rules.

I have covered this topic in a very simple way.

This article is must be recommended for those civil engineering students and freshers who want to work in the construction industry in the upcoming future.

But why am I saying?

You can understand the reason if you read this article completely.

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What is Geopolymer Concrete?

 

The term “Geopolymer” was coined by Professor Davidovits in 1978. Geopolymer is an inorganic alumina-silicate polymer, synthesized from mostly silicon and aluminium material such as fly ash. Also used alkaline solutions for inducing the silicon and aluminium atoms; in the source materials (fly ash), to dissolve to form a gel. The Geopolymer gel binds the loose coarse and fine aggregates to form geopolymer concrete. Geopolymer gel replaced the C-S-H gel in cement concrete. The chemical reaction period is very much fast and the required curing period may be within 24 to 48 hours.

 

Manufacturing Process:-

First of all, the process of manufacturing Geopolymer concrete is very complicated, so I will not go too deep. I will try to explain this topic as simply as possible.

 

First of all, you need to know, what raw materials take to manufacture the Geopolymer concrete.

1. Rich fly ash

2. Silica

3. Aluminium

4. Sodium Silicate

5. Sodium Hydroxide

6. Potassium Hydroxide

7. Potassium Silicate

8. Naphthalene

9. Aggregate (coarse & fine)

1st Step,   Sodium hydroxide in flake from Na(OH) with 98% purity and sodium silicate solutions were used as alkaline activators. To improve the workability of fresh concrete, a commercially available naphthalene based superplasticizer was used. Four types of aggregate mixed together.

2^nd Step, Aggregates and the fly ash was mixed dry in a pan mixer for 3 minutes. The alkaline solutions and the superplasticizer were mixed together, and then added to the solid particles and mixed for another 3 to 5 minutes. The fresh concrete had a stiff consistency and was glossy in appearance.

At the last some salient parameter affecting the compressive strength of Geopolymer concrete are listed below –

1. Silicon oxide (SiO₂) to aluminium oxide (Al₂O₃) ratio by mass in fly ash should preferably be in the range of 2.0 to 3.5 to make good concrete.

2. Activator liquid to source material (fly ash) ratio by mass

3. The concentration of sodium hydroxide NaOH liquid measured in term of Molarity (M) in the range of 8 to 16 M.

4. The curing temperature in the range of 30 to 90 C

5. Curing time in the range of 6 to 48 hours

6. Water content in the mixture.

    

   Why do we use Geopolymer concrete?

   There are many reasons to use Geopolymer Concrete, and it is increasing in day by day. But why are we choosing this Geopolymer Concrete instead of Portland Cement Concrete, the prime reason behind is tremendous environmental pollution.

   It is estimated that about 7% of greenhouse gas is being emitted into the atmosphere annually on account of the production of OPC alone.

   Therefore, it is necessary to reduce the emission of CO₂ into the atmosphere by reducing cement production and consumption.

   It is suggested that consumption of cement could be reduced by three ways –

   Through economical mix design

   By replacing cement with fly ash by adopting high volume fly ash concrete (HVFC) or by using other supplementary cementitious materials.

   By using alternate binding materials for concrete such as Bacterial concrete or Geopolymer concrete.

   So these are some of the reasons for using Geopolymer concrete. Moreover, the production cost is much lower than the OPC.

    

   Advantages and Disadvantages of Geopolymer Concrete:-

   Like all other concrete, Geopolymer also some advantages and disadvantages. So first I will discuss the advantages than the disadvantages.

   Advantages:

   High (both compressive & tensile) Strength – It has a high compressive and high tensile strength, then that of OPC. It is less brittle, more flexible. It also has rapid strength gain and cures very quickly.

   Low shrinkage, creep and bleeding – Shrinkage, creep and bleeding these three properties are bad for all types of concrete. And it has been found that these three properties are much less in Geopolymer concrete than in OPC.

   Resist Chemical Attack – Acids, toxic waste and saltwater will not have an effect on geopolymer concrete. 

   

    

   Protected from cold and heat –  Geopolymer concrete has the ability to stay stable at high temperature(2200 F). It is resistant to freezing. When temperature deep to below freezing that water freezes and then expands this will cause cracks to form.

   Eco-friendly – It is one of the most important advantages because pollution that caused by the emission of CO₂ during the production of OPC. But geopolymer concrete is totally eco friendly.

   Disadvantages:

   Difficult to Manufacture – Geopolymer concrete is very difficult to manufacture various chemicals required. It is very critical to make without experienced labour. Then the polymerization process is very sensitive. Also, uniformity is lacking.

   Ready-mix only –  So far geopolymer concrete is being used only as ready mix concrete.

   
   

   Used of Geopolymer Concrete:-

   Geopolymer concrete can be used for all the works for which Portland Cement Concrete is usually used. 

   

    

   It is mostly used in highway pavement construction, because of heat resistant pavement due to its thermal capacity. Geopolymer cement store less water from solution during particle reaction, and therefore, prevent aged dry shrinkage and strength degradation due to rapid water loss under extreme heat.

   Geopolymer is also being used to make precast sewage pipe because has been found that 40-45% of sewage pipe damage is caused by biogenous sulphuric acid attack. And Geopolymer concrete is able to prevent this better than PCC.

   Geopolymer concrete is used for casting of both column and beams. It has also been shown that it is much stronger and durable than Portland Cement Concrete and also has the ability to take more loads.

   And it has been also used to casting huge retaining walls, railway sleeper, foundation and marine structures.

    

   Conclusion:-  

   Geopolymer concrete is concrete made without using Portland cement and as such, it is environmentally friendly and energy-efficient construction material with enormous potential in many infrastructural applications. Geopolymer concrete shows significantly friendly but also possesses excellent mechanical properties. The limited trial result that geopolymer concrete undergoes very little drying shrinkage and moderately low creep, and possesses excellent resistance to sulphate attack.

   One thing can be said in the end, since it is an eco-friendly product, so we will see more use in the future.

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