What is the purpose of adding gypsum to cement?

<p>Cement is manufactured by heating limestone (calcium carbonate) with small amounts of other materials, such as clay, to a high temperature in a kiln in a process known as calcination, which produces clinker. The clinker is then cooled and ground into a fine powder that we know as cement.</p> <p>However, the clinker is highly reactive, and when mixed with water, it would harden immediately. This would not be practical in a construction setting because it doesn&#39;t allow enough time for the cement mix to be poured, shaped, or smoothed out.</p> <p>Gypsum ($\mathrm{CaSO}_4 \cdot 2 \mathrm{H}_2 \mathrm{O}$) is added to this clinker before it&#39;s ground into cement. The role of gypsum is to extend the time it takes for the cement to set, giving the workers enough time to work with the cement before it hardens.</p> <p>The gypsum reacts with the clinker during the final grinding process, controlling the rate at which the cement will set. If no gypsum was added, the cement would set as soon as water is added, making it almost impossible to use in construction.</p>