Fly Ash & OPC Chemical Compound and i will do one attachment for your good Reference , its From NTPC 

Chemical Compound        Fly Ash(Type- F)            Portland Cement

SiO2                                      54.9                                      22.6

Al2O3                                    25.8                                        4.3

Fe2O3                                    6.90                                       2.4

CaO                                       8.70                                      64.4

MgO                                       1.80                                        2.1

SO3                                        0.60                                        2.3

Na2O & K2O                          0.60                                        0.60

Dr. Ilango

Thanks for your reply. The fly ash you mentioned is more like type F fly ash. It is common to use this type of fly ash in ECC. It seems that amount of one of these components has critical role in getting good results from ECC that I am not aware of. Several companies produces type F fly ash but not all of them are suitable for ECC because of amount of that critical component.

Dear Farshid Hosseini , 

Please go through My  "Attachment"  $ "fly-ash-cement-concrete .pdf " you will have more nice idea .

Class F fly ash - This fly ash is pozzolanic in nature, and contains less than 20% lime (CaO) and having pozzolanic properties

Class C fly ash - Class C fly ash hardens and gets stronger over time. Class C fly ash generally contains more than 20% lime (CaO). Unlike Class F, self-cementing Class C fly ash does not require an activator. Alkali and sulfate (SO4) contents are generally higher in Class C fly ashes.

The benefits that you can achieve with flyash in ECC is its contributions in pozzolanic reaction and a denser gel formation due to its very small particle size. With the dense gel formation the binding strength of the fibers will increase. The denser the gel the stronger the bond of the fibers. In ECC, the fibers come into play only when the concrete/mortar cracks. Once the crack develops the tensile stresses are transferred to to fibers which resists those stresses. Since most the PVA fibers available in the market are very strong in tensile strength, the weakest link is its bond with the cementitious gel within the mortar/concrete. Thus, the denser your gel is the more tensile stress your ECC would be able to resist. If you are using fly ash use the smallest available particle size.  

Dear Mr. Roychand

According to literature, PVA fibers tend to have strong chemical bond with cementitious material which is one of the concerns in getting high tensile hardening behavior in ECC. Using oil coated PVA fibers is one of the methods to reduce this chemical bonding. Also, it seems that using high fraction of fly ash in mix matrix is in benefit of reducing this chemical bond.

Denser gel might have impact on increasing the friction resistance between fibers and the matrix which has important role in getting hardening behavior and multiple cracking and also, as you mentioned, on increasing tensile strength.

Thanks  for your answer, it enlightened some points in ECC's mix properties.

Hi Farshid,

The key thing with ECCs is the interphase between the matrix and the fibre - as you rightly note, "oiling" is used to control the amount of bonding between the fibre and the matrix.  What is not yet well understood is the longevity of this coating and hence how long the balance will be maintained - ECCs typically have a higher cement cotent than e.g. concretes and all cementitious materials continue to harden over time.  You might these two papers of interest;

http://link.springer.com/article/10.1007/s10853-014-8649-6

http://www.tandfonline.com/doi/full/10.1080/15583724.2012.710288

Dr. Jesson

I have noticed that other type of fibers like PE  don't show that strong bonding and it is easier to get strain-hardening behavior. Based on best of my knowledge, PVA fibers show chemical bonding with contentious material and since CaO is mainly responsible for getting strength in cement, using low CaO content cement or fly ash might help.

I also appreciate if you have any comment regarding effect of silica sand size in interphase properties.

Also in your first paper you mentioned that higher porosity leads to better ductility in ECC, so you don't recommend using shaker in preparing the specimens?

Unfortunately I don't have access to your second paper, I would appreciate if you send it to me.

Dear Farshid Hosseini , 

Please go through My  "Attachment"  $ "fly-ash-cement-concrete .pdf " you will have more nice idea .

Dear Farshid Hosseini , 

Please go through My  "Attachment"  $ "fly-ash-cement-concrete .pdf " you will have more nice idea .