grout — a mixture of cement, sand, and water used to fill gaps between tiles

a skilled tile worker carefully applies white grout mixture into the spaces between freshly installed ceramic tiles using a rubber float tool. The worker moves the float diagonally across the tile surface, pressing the thick paste deep into each gap. Before the application, empty dark lines separated each tile, but now those spaces fill with smooth white material. The worker's assistant kneels nearby, mixing more grout in a bucket and wiping excess material from completed sections. the mixture of cement, sand, and water being used to fill gaps between tiles