The Maximization of the Use of the Local Wast Materials may always offers you the best solution in order to Produce Cost-Effective Geopolymer Concrete.

Thank you dear Nima

So the first solution: Use of the Local Waste Materials as a binder

Dear Mohammad Hossein Dalvand

The first solution is : the use of local materials rich in silica, namely: dune sand (for example the Algerian desert occupies a very large area of the total area, this may reduce the cost price of this type of concrete).

Dear Mohammad Hossein Dalvand

The second solution is the reuse of wastes rich in silica , namely: glass waste; marble waste ... etc.

In suggest to look for some natural renewable resources having affinity with concrete preferably waste.

Dear Mohammad,

I’m working about Geopolymer technology from more than 5 years and I can say that the reasons of still low diffusion of these materials are several , but not for the cost that trust me can be lower than Portland concrete , if using local sources obviously, as reminded by Nima.

Mainly there are other more important reasons :

1. Knowledge. The biggest limit is the wrong thinking that Geopolymers are the same products of Alkali Activated Materials (AAM). It’s completely different reaction GP are non hydraulic while AAM are hydraulic and GP can be made in acidic medium with no problem (not for concrete applications because phosphate acid costs about 16€ /kg so isn’t convenient, but is tremendously competitive for dental application and more hi-tech fields). AAM aren‘t stable in water , but have been studied as alternative to Portland that is very hydrophilic . GP ,that Davidovits created and explained well we’re thought for hi-tech applications (automotive, composites , refractories and so on) , can also be used for more base field like concrete.

2. Raw materials selection. GP CAN’T be made using ,as precursor , all silicon aluminates minerals but only amorphous powders with correct mineralogy. I’m sorry Cherif but dune sand isn’t good as precursor (it’s composed by almost 50:50 Silica and carbonate) because is crystalline but could be used as very fine part of aggregate charge. While marble is carbonate rock so really useless for both part, because reduces also durability of concrete if used as mineral charge (not good for acid attack, totally micro crystalline and not reactive for GP).

There are cheap materials not only from waste that can be used , for example glass isn’t useful because hasn’t Alumina inside , but is amorphous so can substitute at 100% quartz fillers as fine aggregate (coarse glass isn‘t good). All volcanic rocks (granite, ossidiana ,basalt, Mica) or volcanic ashes (tuffs, most of zeolites , lapillo) can be used to save money. Of course is mandatory to know the mineralogy and the structure of these materials, for example granites are crystalline so are better for aggregate part , but if you use alterated ones are more rich on amorphous minerals, while basalt are effusive rocks so contains glass phases and so on.

3. Mix design. GP can’t be done in continuous like Portland cement concrete, because geopolymerization isn’t hydraulic process so even mixing must follow precise procedure. Check at the video on geopolymer.org about Geopolymer Camp 2019 videos. I have patented an automatic system of mixing that respect all steps to obtain Geopolymer materials. With GeoMITS we are selling these mixing machines, completely automatic, self dosing , self washing suitable even for newcomers about GP technology. You have only to charge a recipe on touch screen monitor and wait for the production .

Only at this point , for me there are costs. But the most big mistake made until now has been to compare GP binder with Portland cement. GP is 2 component while OPC is one component , because water is obviously 0 cost (in Italy industrial water costs 2€/m3 , but ok it’s almost for free). How to save money?

Target price first . If I need to realize standard 30 MPa (M30) concrete , I don’t need clear raw materials, because usually OPC for cheap concrete is grey , so fly ash type F, but also Ferrosialate GP (made using red metakaolin , very cheap) or other unconventional raw materials, can be used. Of course also liquid part, that about GP terminology is called hardener ,not activator (that is used for AAM, where really pH is higher and corrosive because there is same reaction , so needs more power ) because in GP what is super reactive is the amorphous powdered precursor, I will use sodium base silicate solution , with specific molar ratio user friendly, not corrosive.

About aggregate charge there is the best saving, using secondary sands from wastes of other industrial productions (foundry sand, recycled minerals and so on) . GP Concrete doesn‘t need organic additives (like cellulose ether, redispersible polymer powder ,superplasticizers , retarders , accelerants or other special admixtures) the only rheology modifier is little amount of water , but not necessarily tap water or sweet water, because Geopolymerization occurs even using sea water, recycled water, industrial water , dirty water .

For UHGPC that can arrive at 120-130 MPa after 28 days, room temperature curing (water and air both), without fibers, target price is higher so is possible to use potassium silicate and clear precursors usually more expensive. But even in this case the costs are lower than OPC UHPC because of additives incidence and fibers .

These are roughly the bigger problems that obstacle this technology. In next future all raw materials for realizing Geopolymer will reduce costs while OPC will be more expensive (in Italy this trend is already started 3 years ago and now

we are really competitive).

It’s also true that concrete applications are not the best field where start using Geopolymers because of Portland cement lobbies , but this is other topic.

I’m sorry for the long speech but I would like to do some clarifications , specially for newcomers, to avoid misunderstanding and wrong ideas about .

All the best to all

Alex Reggiani

CTO GeoMITS (Italy)

CTO Renca Rus (Russian Federation)

Dear Alex,

Thank you for the useful information

Dear Elijah,

using sodium carbonate you can do principally Alkali Activated Materials, maybe also one component, but not Geopolymer products . Also performances are very different specially when compared after room temperature and more also after water curing .

Sodium carbonate is also a promoter of efflorescences . I know already how to produce liquid silicates quite cheap using a new way of industrial production, but because my NDA I can’t explain better. Costs are reduced a lot.

Mechanical properties and costs aren’t a problem using liquid user friendly silicates sodium or potassium based.

I think that an important parameter is target prices to respect , because every concrete has different cost depending on type of consistency and final application. But we must compare the complete production process (the amount and type of additives that are necessary for ordinary concrete while useless for Geopolymer concrete), not only the cost of Portland cement compared to the cost of Geopolymer binders . I mean that is important to know what are the frequency and the cost about maintenance of that concrete , that are indirect costs to be considered seriously.

Each country has different incidence but durability of Geopolymer materials must be well explained to promote this technology.

I’m saying this because I have clients that are already using my Geopolymer binder to realize several types of concrete (from lightweight,to normal concrete and till to more fine type as UHPGPC ,with or without fibers) and, at the end, they said that their costs are comparable because Geopolymer binder is more efficient than Portland cement , so they can use less and without any additional admixture.

And in Italy we haven’t fly ash F so I need to use other precursors ...

Best regards

Alex Reggiani

In my view, the cost of production of geopolymer concrete is mainly driven by the choice of alkaline activators. So, if we adopt the agricultural waste-derived silicate solution, then the total cost will be much lower.

Thank you.