Target GATE & ESE 2022 (Building Materials)

 Do you Know?

👉Blaine's Air Permeability apparatus is used to test fineness of cement.

                                        

                                                    Fig 1. Blaine Air Permeability apparatus

👉Vicat's needle is used to determine the setting time of cement.

                                                               Fig 2. Vicat's Apparatus

👉Soundness of cement is determined by Le-Chatelier apparatus.

 

Fig 3. Le-Chatelier Apparatus

👉According to IS 4031 Part 5, the initial setting time is conducted on cement by gauging the cement with 0.85 times the water required to give a paste of standard consistency.

👉Low heat portland cement can be used for mass concreting in very large structure while rapid hardening portland cement is unsuitable for it.

👉Gypsum is used in the cement grouts for retarding the setting time.

👉According to IS code for an ordinary portland cement (OPC), the initial setting time should not be less than 30 minutes and the final setting time should not be more than 10 hours (600 minutes)

👉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.)

👉The temperature range in a cement kiln is 1300 to 1500 degree centigrade.

👉Specific gravity of cement is determined by using Le Chatelier's flask.

👉In OPC following are the proportion of oxides

                 Cao  ----------  63%

                SiO2 ----------- 20%

                Al2O3----------- 6.3%

               Fe2O3------------- 3.60%

               MgO-------------- 2.40%

👉 Following is the compound composition in OPC

             Compound                                  Wt %

     Tricalcium silicate, C3S(Alite)        45-60

     Dicalcium silicate,C2S (Belite)      15-30

    Tricalcium aluminate, C3A              6-12

Tetracalcium aluminoferrite, C4AF      6-8

                                                     

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