The fine aggregates used for building mortar include natural sand and artificial sand. Natural sand refers to the rock particles with a nominal particle size less than 5. 00mm formed under the natural conditions, and is divided into river sand, sea sand and mountain sand according to different sources. Artificial sand refers to the rock particles with a nominal particle size less than 5.00mm formed from mining, mechanical crushing and screening of rock.

River sand is long washed under running water and the particles are round, so it is mostly used for general engineering. Sea sand is long washed by sea water, and the particles are round, smooth and relatively clean, but usually mixed with shells and fragments as well as high in the chloride content, so it is not used under normal circumstances. Mountain sand exists in the valley or the old riverbed, and its particles are mostly angular, with rough surface and a high crusher dust content.

Artificial sand is made by crushing natural stone materials, so it has rough, not smooth surface, more edges and corners and greater powder content.