Silicates in cement and concrete primarily refer to materials containing silicon and oxygen, often in combination with other elements like aluminum and calcium. Common silicates used in concrete include natural minerals like feldspar and clays, as well as synthetic compounds like calcium silicate hydrate (C-S-H), which is a crucial product of the cement hydration process. These silicates contribute to the structural matrix of concrete through pozzolanic reactions where reactive silica from the silicates reacts with calcium hydroxide to form additional C-S-H. This process enhances the strength, durability, and density of concrete.