Hydraulic cements are a type of cement that hardens when mixed with water and can set even under water. They are made from materials like limestone and clay, which are heated in a kiln to create a fine powder. This powder reacts with water to form a strong, durable bond, making hydraulic cements ideal for construction projects. Commonly used in concrete and mortar, hydraulic cements are essential for building structures such as bridges, dams, and foundations. Their ability to cure in wet conditions makes them versatile and reliable for various applications in the construction industry.