ssc je paper 2



        1.       Name of the different types of raw materials used for the manufacture cement ? What is the         hydration of cement and heat of hydration ? How is the is the aggregate classified according to size ,    shape ? write down the function of admixtures in concrete?                                        5+10+15+15

Answer :
1)      Name of the different types of raw materials used for the manufacture of cement consists mainly lime , silica , alumina and iron oxide .

2)      Hydration of cement :  The chemical reaction that take place between cement and water is referred as hydration of cement.

Heat of hydration : The reaction of cement with water is exothermic. The reaction liberates a considerable quantity of heat . This liberation of heat is called heat of hydration .

3)      Classification of aggregate according to size are –
                                                                                                                                                                                               I.            Fine aggregate
                                                                                                                                                                                             II.            Coarse aggregate
                                                                                                                                                                                           III.            All – in – aggregate
                                                                                                                                                                                          IV.            Single size aggregate

                    Classification of aggregater according to shape
                                                                                                                                                                                                  I.            Rounded aggregate
                                                                                                                                                                                                II.            Irregular aggregate
                                                                                                                                                                                              III.            Angular aggregate
                                                                                                                                                                                              IV.            Flaky and Elongate                                              aggregate
4)      Functions of admixture :

                                             I.            To accelerate the initial set of concrete .
                                           II.            To retard the initial set of concrete.
                                         III.            To enhance the workability .
                                        IV.            To improve the penetration and pumpability of concrete .
                                          V.            To reduce the segregation in grout and concrete mixtures.
                                        VI.            To increase the strength of concrete.
                                       VII.            To increase the resistance of chemical attack.
                                     VIII.            To reduced the heat of hydration .
                                         IX.            To produced non-skid wearing surfaces.
                                           X.            To increase the bond between old and new concrete surfaces .

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