GPC needs higher temperature curing. Ambient  temperature cured GPC has quite lower strength and durability . The properties of GPC are highly depend on the casting curing condition( it is very sensitive to the moisture, temperature, pressure etc.). Also efflorescence is  also a big problem for GPC.

Geopolymer concrete to be known as a good alternative for OPC concrete. 

I think that cost of production, construction problems, mix design complexity and etc are reasons for not welcomed to this type of concretes, that will be resolved in time.

See on youtube "geopolymer africa" , there are examples of geopolymer production at industrial scale in South Africa

cost depends on fly ash or BFS availability

It depends on many factories including chemical and mineralogical composition uniformity in case of fly ash geopolymers, absence of long term durability data, requirement of extra chemists for alkaline liquids preparation for a producing company that leads more expences etc. Provis, van Deventer et al published 1 good paper on this problem in 2013. You may search it.

GPC needs higher temperature curing. Ambient  temperature cured GPC has quite lower strength and durability . The properties of GPC are highly depend on the casting curing condition( it is very sensitive to the moisture, temperature, pressure etc.). Also efflorescence is  also a big problem for GPC.

Dear Jadambaa Temuujin, would you please supply me the name of that publication?

Technical and commercial progress in the adoption of geopolymer cement,

Minerals Engineering 29 (2012) 89–104

Dr. Temuujin, Than you very much. The reference is very useful to me...

Geopolymer is polymeried under high temperature (more than 60 degree celcius) and activated solution is chemical admixture. It may be produced in factory. Production from geopolymer material is precast, repair material and  brick ,et al. 

Chemical composition and particle size distribution of fly ash procured are not consistently uniform. So, not able to predict  the strength. Curing problem also existing

The initial material, fly ash , bottom ash or rice husk ash, is more fine particle to be good activated  can produce  high performance geopolymer.

 standard mix design for gpc is not available.This is also a drawback.and also handling of alkaline solutions 

Geopolymer concrete requires special handling and it is difficult to create. It requires the use of alkalis, such as sodium hydroxide/ sodium silicate, that can be harmful to humans. GPC should be cured at 60-70 degrees celsius. For mass production of GPC, many tons of sodium silicates are needed which is difficult to produce using current technologies.

Lots of people are making comments about geopolymer binders and concrete without a detailed investigations. The types of source materials and activators and their proportions (proportions of fly ash, slag, sodium hydroxide and sodium silicate) in geopolymer binders can bring lots diversity in the characteristics of final products (geopolymer paste, mortar or concrete). I did a detailed study of engineering properties of geopolymer concrete of different grades (40, 50, 65 and 80 MPa) and workability levels; normal and self compacting concretes. In my study, two types of powder-activated geopolymer binders developed were used as binding materials. In these binders, solid alkali activators (combination of sodium silicate, sodium hydroxide and other alkalis), fly ash and ground granulated blast furnace slag were blended together to make one-part powder binders. Portland cement (type GP) was used to produce control concrete for comparison for each grade and workability levels. Best on my investigations, the limitations of geopolymer concrete are as follows.

The ineffectiveness of commercially available chemical admixtures to change the fresh concrete properties, such as water content, viscosity, cohesion and setting time are the major limitations of geopolymer concrete. Geopolymer concrete of normal strength grade (less than 50 MPa grade) required higher water/binder ratio which is responsible for lower early age strength. On the other hand, Geopolymer concrete of very high strength grade (above 80 MPa grade) is difficult to handle and place due to higher cohesion and significantly shorter setting time.

Geopolymer concretes of 20 MPa and 32 MPa strength grades are difficult to produce because of their  inability of setting and hardening due to higher water/binder ratio required (excess 0.55) and significantly lower binder content (less than 280 kg/m3).

The compressive strength development of normal strength grade (less than 50 MPa grade) geopolymer concretes in early age (1 to 3 days) at ambient curing condition is relatively lower than OPC concrete of same grade. This lower early age compressive strength can restrict the uses of geopolymer concrete in cast-in–situ structural concrete where early age strength is necessary for stripping of formwork and opening of traffic in case of concrete pavements.

Very high strength (80 MPa grade and above) geopolymer concrete is very cohesive and possesses very shorter initial setting time (less than 1 hour) due to lower water/binder ratio in concrete mix. Those limitations could be big issues in cast-in–situ concrete where distance between construction site and batching plant is more than 1 hours. In case of OPC concrete, those limitations can be effetely solved by using commercially available chemical admixtures. However, in geopolymer concrete, there is not any commercially available chemical admixture so far which can overcome these limitations.

I need rough data on  production cost of   one ton of GP based  concrete vs.  one ton  OPC based concrete.

I need rough data on  production cost of   one ton of GP based  concrete vs.  one ton  OPC based concrete.

Cost of geopolymer is not hard and fast. Generally, the source material fly ash and slag are much cheaper than Portland cement as they are the industrial by product. However, cost of activator is much higher. In average the cost of geopolymer binder is around 10 to 20% higher than Portland cement. In terms of concrete, around 30% less geopolymer binder is required for the same strength level to OPC concrete. So, there will be similarity in concrete price.

Thanks Kamal for your useful information.  Is there examples where this technology has been commercialised?.

It has been commercialised in Australia. Brisbane Airport has been made by GPs. I need to add some information regarding the geopolzmers cured at ambient temperature. As it was mentioned above, some researchers claim that GPs should be cured at elavated TEM to gain a high compressive strength, which might bring some difficulties to use this composition in reality! As a way to tackle this problem you might use another binder such as GGBS besides Fly ash, then you will ease this problem.

Also, the characteristices of FA should be considred as an important factor to improve the geopolymerization and decrease the activator to binder ratio. There are other important factores, such as water content, water glass to NaOH ratio, Na2O content, etc.

@Mohammed Ali Yazdi, noted.

Geopolymer has already been established candidate for the static structural  component. However question remains whether it can be applicable as the matrix for high temperature fiber reinforced composites. Fracture toughness is the key issue in that application. Fly ash based geopolymers show more strength than metakaolin based ones because of the structural in-homogeneity and presence of silica as un-reacted particles. 

I published a paper in composite A, which shows systematic curing process for geopolymer for fiber reinforced composite application-http://www.sciencedirect.com/science/article/pii/S1359835X16300069

Also look at my PhD Dissertation-https://dspace.library.colostate.edu/bitstream/handle/10217/167242/Rahman_colostate_0053A_13225.pdf?sequence=1

http://www.sciencedirect.com/science/article/pii/S1359835X16300069

https://dspace.library.colostate.edu/bitstream/handle/10217/167242/Rahman_colostate_0053A_13225.pdf?sequence=1

Low Calcium content (Less than 10%, preferably within 2%) "ASTM Class F" Flyash based GPC only needs higher temperature curing(60 - 80 deg C). If we could able to optimize  calcium content such that creating atmosphere of both gel formations(C-S-H & Si-O-Al-O) ambient cured GPC with high strength possible. 

this field of study has been proven inconclusive and extremely volatile. Uniformity is lacking.

I think that this topic is good only for scientific speculation and not for real application. I mean that the researchers usually change something in the composition and are able to write papers about this topic and that is all. I think that there are many limitations, one is in the mechanical properties, and also in the presence of alkaline activators that are not so eco-friendly.

As the research head of Geopolymer, the key driver is the usage of proper alkali in the polymeric reaction. Using pre analysed standard fly ash, ground slag, metakaolin is equally important to standardise the mix proportions. We have developed suitable user friendly alkali (no separate addition of hydroxide needed) for ambient temperature curing which will meet most of the concrete requirements. Very high quality of precast and structural elements have been made and tested. Using of laying roads with geopolymer concrete will be an ideal large volume application.

What kind of friendly alkali do you developed? Can you recommend something ?

Thank you!

Hi

i would like know as what is the present status on utilisation of LD and BF Slag?

Thus is gives benefit over existing or natural polymers if any? 

What other applications can be the probability of using these stuff??

@ Ramani Ramaratnam: Sir, Could you please provide an insight on the user-friendly alkali you developed?

There are many research papers available to disign the GPC. The strength of GPC is depends on many factors mainly the si/Al ratio in source material the higher strength is achieved by increasing molarity of sodium hydroxide. The key need is to get higher strength at ambient conditions. However use of GPC in precast concrete construction helps in speedy construction work and also reduces the CO2 emissions due to cement production. The cost of activators may be reduced by mass production.

Now, my formulation doesn't require any additions of Sodium hydroxide (a hazardous chemical) with a catalyst which works well at ambient temperature, more ideal for precast products, shotcreting and 3D printing.

That is great innovation sir .This will help to use GPC in regular construction practice.

The important issue here is the preparation of alkali activated solution for GP. Mainly, the Molarity of NaOH solution, higher the molarity more the strength it is. Moreover, the polymeric gel in GP such as N-A-S-H (Sodium Alumino Silicate Hydrates), as like C-S-H in OPC, has not been studied in GP.

In addition, as like the models developed for the Inter-facial Transition Zone in OPC concrete (i.e the zone between aggregates and C-S-H gel), none of the studies are there in literature for the case of GP.

After studying the above said properties, one can probably design the GP concrete mix.

The biggest limitation of geopolymer as an alternative binder is the lack of enough precursor material such as fly ash and slag or metakaolin to meet the demand for cement. The global consumption of cement is about 4-5 times that of generation of industrial wastes like fly ash and slag, While the former continues to increase year on year, the latter is likely to decrease due to adoption of renewable energy. Strategically geopolymer will always be a material for niche applications such as acid resistant sewer pipes or precast panels etc. While it has a long history of successful application in former Soviet Union (particularly Ukraine) dating back several decades, the only successful industrial scale application currently can be found in Australia. How ever, it is an important area of research given its potential particularly if pond ash and ash in mine filing can be proven to be viable precursors and all the other bottlenecks of mix design, processing and performance assurance etc can be overcome.

Geopolymer should never be looked at as a replacement for cement. Instead use it applications where cement can not meet the requirement. I am successfully using/ implementing in Coastal protection armours, Roads, Security and Fire resistant applications - chimneys, furnaces and in sewerage treatment/ handling. Shotcreting of mines/ tunnels, 3D printing and precast portable homes are few areas under exploration. We have also perfected the technology of using Redmud in our mix design making copolymers affordable. We look for channel partners in Gulf and Africa where we can supply our binder and have generated interest. [email protected]

Limitations for large scale application is the organisation of the supply chain.

Think about building with OPC. You go to local supplier and buy a bag. That's it.

Geopolymer requires for the moment higher know-how on site.

Geopolymer is a decentralized production with local knowledge, compared to cement production where you have centralized production and embeded knowledge in the bag (you just need to add water afterward).

Hello dear

This question seems a little too general ! First we need to understand what is the application then we will manage the requested properties from the material and finally we will identify the shortcomings of "geopolymers".

Geoplymers have been shown to be suitable for prefabrication of structural and non-structural elements. This is due to the fact that to the best of my knowledge no practical approach has been presented to obtain equivalent properties to conventional concrete by ambient curing conditions.

Also, when shrinkage of geopolymers is under control, using this material as repair material is a smart choice due to the fast setting properties and proper adhesion.

A big limitation is the use of strong chemical mediums or so called "chemical activators". I suggest you to read the papers which have claimed when strong mediums are used in geopolymers, this material is even less environmental than OPC!

It is however very important to bear in mind that the main interest in use of geopolymer as replacement of opc-based mixtures is environmental interest. This mean that in many cases we have to close our eyes on additional costs required to involve geopolymers in projects which are using a lot of opc.

Finally, I think its important to mention that there is repelling environment which exists among the building material developers. I personally once posed this question from on R&D fellow working in SIKA that why don't you consider geopolymers and he replied the shrinkage is a problem !! so what ? why not working on that ?? Unfortunately in construction business developers have traditional type of thinking ...

I guess it all depends on the application. For precast industry it seems to be a perfect option. And there are cases in Australia where it has been extensively used, please refer to attached link.

I think, its just that it takes time to come out of traditional thinking.

There is no doubt that the amount of research gone in cement concrete is vast, particularly performance based tests, experiments, and field studies. I guess geopolymer concrete needs more research on performance based approach, with emphasis being given on field studies, experiments, and long term performance.

I think geopolymer may be applied in precast units and constant conditions because of sensitivity of geopolymer toward composition and curing conditions. this application will allow curing at elevated temperatures.

if in my country the price for making it is quite expensive. how to make it is not as practical as ordinary concrete.

My suggestion would be is not to compare with PCC, particularly cost. There are many application where Geopolymer concrete are better and advantageous. You should be careful in selecting the products in the initial stage. Of course you can follow the testing procedure of PCC for comparison of performance. We have made number applications which are cost comparable, sometimes cheaper