Dear Dr. Saleh,

The deleterious reactions of sulfate become from this reason:

We know that gypsum was added to the clinker during grinding in the manufacturing of cement to prevent flash setting, So If gypsum exhausted before C3A The remaining C3A begins in hydration:

C3A + 6H → C3AH6

C3AH6 is stable –cubical crystals- with high sulfate resistance.

Calcium aluminate hydrate : Be at many forms before transforming to the stable state (C3AH6). It is probably forming hexagonal crystals (C4AH8, C4AH10, C4AH12) before the cubical crystals.

When the hexagonal crystals expose to sulfates (inside concrete from sand or external from soil or ground water) → react with it forming calcium sulfoaluminate → with increase in volume, depending on the amount of remaining aluminates and the concentration of sulfates → crack and deteriorate of the hardened concrete.

The transformation of calcium aluminates hydrate from the metastable hexagonal form to the stable cubical form is accompanied with – change in the density and size of the crystals – leading to decrease in the late ages strength of the cement paste due to

– lose the adhesion and cohesion in the microstructure

–increase the porosity of the hardened cement paste.

For a chloride effect I have attached you file I hope it is useful to you

Best Wishes

Dear Dr.Saleh

I recommend Doha's Answer

Best regards

I completely agree with Dr. Doha M Al Saffar

The deleterious reactions of sulfate become from this reason:

We know that gypsum was added to the clinker during grinding in the manufacturing of cement to prevent flash setting, So If gypsum exhausted beforeC3A The remaining C3A begins in hydration:

C3A + 6H → C3AH6

C3AH6 is stable –cubical crystals- with high sulfate resistance.

Calcium aluminate hydrate : Be at many forms before transforming to the stable state (C3AH6). It is probably forming hexagonal crystals (C4AH8, C4AH10, C4AH12) before the cubical crystals.

When the hexagonal crystals expose to sulfates (inside concrete from sand orexternal from soil or ground water) → react with it forming calcium sulfoaluminate → with increase in volume, depending on the amount of remaining aluminates and the concentration of sulfates → crack and deteriorate of the hardened concrete.

The transformation of calcium aluminates hydrate from the metastable hexagonal form to the stable cubical form is accompanied with – change in the density and size of the crystals – leading to decrease in the late ages strength of the cement paste due to

– lose the adhesion and cohesion in the microstructure

–increase the porosity of the hardened cement paste.

The chemical attack of seawater on cement constituents is the reactions between sulphates, as well as chlorides, which are the most aggressive ions with cement constituents, because certain constituents of cement can enter into deleterious reactions with SO42- and Cl-, leading to the dissolution of Ca(OH)2 and the formation of sulphoaluminate and chloroaluminate hydrates, which cause expansion and softening of concrete, respectively.

Dear Dr. El-Awney,

I mentioned some of reactions in the other question. You may find them here:

https://www.researchgate.net/post/What_are_the_most_aggressive_ions_in_sea_water_for_cement_concrete

Regards,

The most deleterious effect is the formation of ettringite which leads to expansive reaction . This may significantly accelerate the crack initiation in the concrete members.

Dear Dr. Alireza Joshaghani, Thank you so much for your interesting and valuable comments. For necessary please send me your E-mail as soon as possible.

All the best Regards

Sincerely Yours,

Prof. Dr. Saleh Abd El-Aleem Mohammed

(Applied and Engineering Inorganic Chemistry)

Vice-Dean Faculty of Science, Fayoum University, Fayoum, Egypt

[email protected]

If gypsum exhausted beforeC3A The remaining C3A begins in hydration:

C3A + 6H → C3AH6

C3AH6 is stable –cubical crystals- with high sulfate resistance.

Calcium aluminate hydrate : Be at many forms before transforming to the stable state (C3AH6). It is probably forming hexagonal crystals (C4AH8, C4AH10, C4AH12) before the cubical crystals.

Dear Dr.Saleh

I recommend Doha's Answer

Best regards

Doha M Al Saffar answered the question sufficiently