try using Masratan Sodiumy (SNF-A): in my parer SOLID FUELS MADE FROM PULVERIZED MAGHARA COAL USING DIFFERENT ADHESIVE Fig.1 and table 2 , show the stress strain diagram in such paper to show the huge strength achieved by such blended material. it may be help you to increase strenght.

Dear Tan,

first you have to decide what you want to produce.

If you want to realise simple alkali activation, don‘t speak about geopolymer product. These technologies are very different and alkali activated material and geopolymer material aren’t sinonims.

So if you want to do geopolymer concretes, please , use the correct terminology. Silicates aren’t activators but hardeners or reagents ; what is really reactive are your alumina silicates precursors .

You must know your precursors not only about chemistry that gives you incomplete informations , but mineralogy, temperature of calcining , type (about fly ash class F is good to use, with class C you CANNOT obtain geopolymerization, only simple alkali activation ) and granulometry.

From these data you will find where you are wrong.

Geopolymer binders are possible to obtain only following precise rules (see on geopolymer.org , site of Geopolymer Institute , about teachings of my friend Prof. Davidovits ) . No gypsum (it’s crystalline can’t be useful for net forming ) , no sludge (same reason and mineral composition isn‘t stable ), no other strange raw material are present in geopolymer binders. Probably your mix design is wrong and for sure if you add raw materials that can’t support geopolymerization , you definitely can’t increase performances.

What about condensation time of your concrete , curing temperature and quality of aggregates?

Last question did you use solid salts and water as only liquid part, or liquid silicates ?

Molar ratio is an important parameter not every pH can permit that reaction occurs.

Best regards

Alex Reggiani

Dear Alex Reggiani ,

Thanks for your answer.

First, I want to produce mortar without using any OPC. Previously I have produce good mortar without OPC, and the formula is FA/GGBS blended, activated by sodium carbonate and sodium silicate. After that, this formula cannot work because of changing source of GGBS, I obtained it from other supplier.

From XRD results, the previous GGBS stock (that gives me good result) contain some gypsum, and this current stock doesn''t have, that's why I added gypsum after that. The calcium content for current GGBS stock is around 35%, and it majorly consist of amorphous phase. The Fly ash I used is high calcium fly ash (class C).

To answer your question : My concrete I moist cured for 7 days and then only I tested the strength. The curing temperature is room temperature. The aggregate I used was river sand. The sodium silicate I used was liquid sodium silicate. No other solid @salt was added..

May I know what your molar ratio refer to ..??

Sincerely

Tan Leng Ee