Composition of Portland Cement before Hydration [closed]








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I recently came across a question-



> 
> Which of following chemicals is NOT found in Portland Cement?
> 
> 
> A. Di-calcium silicate
> 
> 
> B. Tri-calcium silicate
> 
> 
> C. $\ce{CaSiO3}$
> 
> 
> D. $\ce{Ca3(PO4)2}$
> 
> 
> 


I answered D. $\ce{Ca3(PO4)2}$. But according to the examiner the answer is C. $\ce{CaSiO3}$


I strongly doubt that. Any pointers to credible sources/books settling this please!!




According to Ullmann’s Encyclopedia of Industrial Chemistry (sixth edition), Portland cement consists mainly of tricalcium silicate, dicalcium silicate, tricalcium aluminate, and calcium aluminoferrite.


$$
\textbf{Phase composition of Portland cement clinker} \\
\begin{array}{llll}
\hline
\text{Constituent} & \text{Formula} & \text{Content in wt %} \\
& & \text{Range} & \text{Average}\\
\hline
\text{Tricalcium silicate} & \ce{3CaO.SiO2} & 46{-}79 & 61 \\
\text{Dicalcium silicate} & \ce{2CaO.SiO2} & 5{-}30 & 15 \\
\text{Calcium aluminoferrite} & \ce{2CaO.(Al2O3,Fe2O3)} & 4{-}16 & \phantom{0}8 \\
\text{Tricalcium aluminate} & \ce{3CaO.Al2O3} & 6{-}18 & 12 \\
\text{Free calcium oxide} & \ce{CaO} & 0.1{-}4 \\
\text{Free magnesium oxide} & \ce{MgO} & 0.7{-}1.5 & \phantom{0}1.5 \\
\hline
\end{array}$$


Büchel, Moretto, Woditsch *Industrial Inorganic Chemistry* (second edition) lists the same six constituents as important clinker phases. This reference also includes a diagram for the three component system $\ce{CaO}$–$\ce{SiO2}$–$\ce{Al2O3}$ with composition ranges for various cement types, which shows that calcium monosilicate (CS) is not necessarily within the typical range for Portland cement.


![Three component system CaO–SiO2–Al2O3 with composition ranges for the hydraulic bonding agents](https://i.stack.imgur.com/aXXQt.png)


Furthermore, this reference includes a table with a typical chemical analysis of a Portland cement, which shows that the $\ce{CaO}$–$\ce{SiO2}$ ratio is too high for calcium monosilicate and also indicates that small amounts of phosphate could be present:


$$
\textbf{Typical chemical composition of a Portland cement clinker} \\
\begin{array}{ll}
\hline
\ce{CaO} & 58{-}67\ \% \\
\ce{SiO2} & 16{-}26\ \% \\
\ce{Al2O3} & \phantom{0}4{-}8\ \% \\
\ce{Fe2O3} & \phantom{0}2{-}5\ \% \\
\ce{MgO} & \phantom{0}1{-}5\ \% \\
\ce{SO3} & \phantom{0}0.1{-}2.5\ \% \\
\ce{Mn2O3} & \phantom{0}0{-}3\ \% \\
\ce{P2O5} & \phantom{0}0{-}1.5\ \% \\
\ce{TiO2} & \phantom{0}0{-}0.5\ \% \\
\hline
\end{array}$$


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