Target GATE & ESE 2022 (Building Materials)

 👉Fine grinding leads to high early strength.

👉 The finer the cement the higher is the rate of hydration which results in early development of strength.

👉Decreasing the lime cement increases the proportion of C2S (Belite) and reduces that of C3S (Alite) and hence leads to slow setting low heat cement.

👉Burning at higher temperature increases the proportion of Alite (C3S) in cement and hence leads to high early strength.

👉Increasing the quantity of gypsum retards setting of cement.

👉Before testing setting time of cement, test for consistency (Normal Consistency) is done to know the water required for preparation of standard paste of normal consistency. Amount of water (0.85 times water used in consistency) is used for preparation of cement paste in setting time test.

👉Low heat cement has a high percentage of dicalcium silicate (C2S) and low percentage of tricalcium silicate (C3S)

👉High early strength portland cement has high percentage of C3S and lower percentage of C2S

👉Specific gravity of cement (G = 3.14) is determined by Le Chatelier's Flask.

                                                                 Le Chatelier's Flask

👉For checking the soundness( Soundness test is done on cement to determine the expansion of cement due to the presence of free lime and magnesia in the cement) of cement Autoclave test is done.

    

👉The fineness of cement is determined by Blaine's Air Permeability apparatus.

👉Superplasticizers increases the workability by dispersion of cement particles. It can remove air bubbles . It can also be used to retard setting.

👉Blast furnace slag cement is more resistant to sulphate attack and is specified for marine work or pipe carrying water containing chemicals or sewage.

👉  Different Phase of cement                          Temperature ( in Degree Celsius)

      Formation of C3S                                                               > 1250 

   

       Formation of C2S                                                               900-1200

      Formation of C3A and C4AF                                              Cooling Stage

      Decarbonation of CaCO3                                                     < 900

👉LSF(Lime saturation factor) is a used quality parameter to limit the amount of free lime (CaO)

👉LSF is used a quality parameter to limit the Unsoundness of the cement.         

👉 Crystal Structure of different phases

             C3S ------------------  Irregular Structures, several polymorphs.

         

             C2S--------------------Rounded structures, several polymorphs

             C3A ------------------Cubic in pure form

             C4AF-----------------Series of solid solutions

👉 The decreasing order of heat of hydration of pure cement compounds are:

                 C3A > C3S > C4AF > C2S