2013-11-02 by wsdchemicalWhen the amount of cement and stearate aluminum , reconcile , began to form a slurry is a plastic , a workability . With the passage of time , gradually lose plasticity slurry into the close state can not flow , then gradually increases the intensity of the slurry , until finally can become a considerable strength of the stone -like solid . If the original is also mixed with a collection of materials such as sand , gravel , etc., will cement cemented them together into a solid whole, that is, we often say that the concrete . This whole process we call it the setting and hardening of cement . The physical , chemical point of view , setting and hardening is carried out continuously , a process can not completely separate the condensation is hardened base , hardening condensation continue. However, in order to ensure the construction quality construction , requiring the cement paste loses its plasticity must end before construction , so people according to the needs and characteristics of cement paste , the whole process of these artificially divided into two setting and hardening process . Condensing means into a cement paste from non- malleable plastic and has a very low intensity of the process ; hardened paste is gradually increased strength to resist external force in the process . In addition, further condensation process also artificially divided into initial and final setting , with the addition of water to represent the time commences . For example, the national standard : ordinary portland cement initial set no earlier than 45min, not later than the final setting of 12h. When used during the construction watering time must be earlier than 45min; into the final setting only after the removal of the template to begin the next cycle of production .