Hello,

There is potential and some benefits associated with using fly ash lime mixture as a binder. However, there are problems with the performance of such mixture at high temperature that need to be tackled.

A number of researchers have investigated the subject. I would point you to the following:

http://sparc.nfu.edu.tw/~ijeti/download/V4-no1-30-37.pdf

Best wishes with your research

Thanks a lot Dear Saidani, for your kind response.

Fly ash is a pozzolan which requires lime as a starter for the hydration reaction process to form CSH. Lime on the other hand gains strength by carbonation to form calcium carbonate (CaCo3). Surely a fly ash-lime mixture will provide a binder for such purposes as mortars for building, bricks and blocks etc. We have established that fly ash lime mixtures can be used for bricks and blocks for low cost housing in Tanzania. 

Fly ash has been used as binding materials in many applications. However, one important aspect about utilization of fly ash is their lime content. If it is Class-F then you probably have to add more amount of lime. The overall performance has also been found to be satisfactory. I have also worked on class-F fly ash and I have increased the performance of the fly ash by slightly adding GGBS. In this way, the amount of lime has been drastically reduced.

As rightly pointed out by Dr. Sharma, Fly ash have tremendous scope due to its cementitious property. You need to first understand that flyash itself contains lime. Usually class F contains lime less than 20% (even less than 10%) whereas class C contains more than 20% lime. It is the amount of silicate, aluminate etc. in fly ash which reacts with lime and converts into CSH gel. When hydration of cement takes place, liberation of lime along with formation of CSH gel takes place. This liberated lime further reacts with aluminate, silicates of   flyash and forms CSH gel which imparts improvement in further strength.

However you need to consider many points which choosing the replacement of cement with Flyash and lime such as:

1. Degree of strength you want to achieve with cement replacement with lime and fly ash

2. The time duration for target strength which becomes a crucial factor in most of the cases as pozzolonic reaction are significantly slower than usual cement hydration

3. You need to look into the ratio in which you want to mix fly ash and lime to get optimal result

4.  The selection of type of fly ash with its chemical analysis based upon its constituent components along with the type and age of lime as their degree of reactivity will largely depend upon it

5. You need to first and foremost look into the application for which you need to replace cement with fly ash and lime and its suitability.

and many more thing you need to look into.

You may look for various other options such as High Volume flyash concrete, Geopolymer concrete etc. which may provide further understanding in this regard.