Technical above mentioned components of the cement . This melting and reacting of the raw material is also called point of incipient fusion . The raw material fuses to form the different components depending upon the temperature and heat absorbed . When the mixture of the raw materials is poured into the kiln , the outer or peripheral particles of the mixture are subjected to maximum temperature and energy , so bigger molecular components ( like C 4AF ) are formed after fusion reaction by absorbing greater amount of energy . Similarly , the core of the mixture is subjected to a comparatively lesser energy and temperature , so smaller molecular components ( like C 2S ) is formed by absorbing comparatively lesser amount of energy .
When the fusion reaction is completed , the final product is gradually cooled to avoid the absorption of water molecules from atmosphere so that it maintains its amorphous form . After cooling , around 3 % of CaSO 4 is added to the cement to avoid instant setting or flash setting of cement paste .
to form H 2SO 4 and CaO , which makes the water acidic . Initially a colloidal or suspended solution of cement ( dark liquid ) is formed due to this acidic environment . Because of this C 4AF and C 3A are unable to react with water instantly and so the energy and plasticity of the solution remains for a small duration called initial setting time . During this small duration , the traces of alkalis present in the cement neutralise the acidic environment . After this initial setting time , a neutral environment is formed , which is suitable for the reaction between the components of cement & water . Thus the reaction starts with water and this reaction is termed as Hydration of cement .
In the above graph , the reaction with water of the different components of cement with the
Properties of Cement Components
From the above paragraphs , it is clear that , the bigger molecules have formed with higher energy and so they have higher affinity to water and they react as well as solidifies faster as compared to smaller sized molecules . So if there is no CaSO 4 , then on the addition of water to cement , C 4AF will be first to react and solidify within a fraction of second , releasing the energy it had absorbed to get fused , C 3A will be the second , C 3S will be third and C 2S will be the last .
But due to the presence of CaSO 4 , the above reaction is delayed . When water is added to cement , CaSO 4 reacts with water immediately passage of time is shown . Theoretically , the component shall start reacting after initial setting time ( when a neutral environment , suitable for reaction is formed ) and should set instantly without any delay but due to the following reason the reaction or hydration