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Since last few decades, cement consumption is increasing day by day and hence the production of cement is also increasing. Last year in India, 65% cement is used by housing and real estate, where 20% cement is used for public infrastructure and 15% cement is used for industrial development.
Cement is the building materials which impacts strength and durability of the structure. It is responsible for the properties of concrete/mortar masonry. It is compressive strength of concrete that ensures the higher life of construction and therefore it depends on the quality of cement.
Most people gets confused while using an old cement or cement which is stored for long. As it feels hard or when they touch it hence the next question that arise in a curious mind is how the moisture effects the cement.
Before we discuss the effect of moisture on cement, let us understand the chemistry of strength gain due to cement. Cement when mixed with water, undergoes a chemical reaction called hydration, due to which it hardens and acquire strength. The finer the cement, the more it hydrates (i.e. mixed with water) and more strength. Hence or when stored or not in use, even the atmospheric moisture reacts with cement and hence it will start to harden. Thus, moisture is very dangerous for cement.
Manufacturing of cement includes numbers of raw materials like limestone, sand, shale, iron, etc. There are two methods used to manufacture the cement. Whether it is wet process of manufacturing cement or dry process of manufacturing cement, in both cases, before and after packaging, moisture plays a key role. During the manufacturing of cement, if we do not control moisture and temperature, the produced cement will be of low quality. Same way, after packaging, if cement gets moist, it results into the lumps and use of such cement may result into the poor quality of concrete/mortar and ultimately it reduces the life of the building or house.
Cement like sugar is a hygroscopic (Tending to absorb moisture from the air) material which reacts with water (either in liquid or even in vapour form). Cement must be kept away from both wetness (actual water such as leaks, flooding, etc. which can be seen with the naked eyes) and dampness (Moisture in the air which cannot be seen, but which is always present to some extent). Moisture is a great enemy of the cement.
When water vapour passes through the multi-layer paper/ jute / polyethylene sacks, cement gets hardened to forms lumps and damage the quality of the stored cement. Hence, cement should be stored in such a manner that no moisture or dampness is allowed to reach cement either from the ground or from the environment. Extra precautions should be taken both at site and at a warehouse while storing the cement. The godown and warehouse should be leakage proof and built at a higher elevation so that it will not get affected by the moisture.
When water is added, cement sets. Initial setting takes place in 30 minutes.
Cement thus plays a key role, it binds the dry ingredients of concrete/mortar when water is mixed. Cement and water react with each other and generates the heat of hydration. This process of generating heat is also known as hydration of cement. Due to the initial set of cement, the concrete/mortar mix start to harden within the initial setting time. To know more, read setting time of cement.
After the initial setting, cement hardens which makes it non-reusable. Same way, if stored cement bags get affected by the moisture, they react with moisture and hardens in the form of lumps. Such cement bags will render a poor performance if it is used for the construction.
Hence like food, it is therefore advisable not to store cement bags for long periods or use it as early as possible after manufacturing. It is recommended that newly manufactured fresh cement should be used within the first three month and it will definitely ensure good quality of concrete. If the cement has been stored for more than three months, it should be first tested for its quality and then only it should be used for construction.
Thus, storage of cement is very important. To know more about storing period of cement, read the period of storing of cement from date of manufacture. We have also discussed points which needs to check on a cement bags before buying it and how to check the quality of cement at site.
In conclusion, the strength and durability of the structure mainly depends on the strength of cement. It is therefore very important to use fresh and good quality of cement. The quality of cement remains good only, if the effect of moisture on cement bags is minimum or negligible. Hence like food always use it as fresh as fresh possible.