Health preservation is the maintenance of cement products. The characteristic of cement is that the more it solidifies in water, the greater its strength. Maybe you've had this experience. Accidentally, the cement was rained or soaked in water, forming a cement block. This cement block is harder than the cement in our building, without cracks, like a stone. Cement that is really completely soaked in water and solidified is the hardest. Therefore, cement products, such as cement pavement and concrete floor, are often watered to keep moist after molding, and covered with straw or blanket to slow down the evaporation of water and make cement solidify in water as much as possible. This is health preservation.