What characteristic helps uncoated concrete cisterns retain water effectively?

Uncoated concrete cisterns are effective at retaining water primarily due to their porous nature. This characteristic allows some retention of water within the tiny pores and voids present in the concrete material. As water seeps into these pores, it can remain trapped, which prevents immediate drainage and helps the cistern maintain a certain level of water.

The design of uncoated concrete structures intentionally retains some moisture, which can aid in preventing rapid evaporation and assists with the overall water storage capability. While the chemical composition, aggregate size, and density of concrete influence its structural integrity and durability, they are not as critical in the context of water retention as the porosity of the material itself. Thus, the combination of the inherent porosity of the concrete and its ability to hold water makes this characteristic particularly significant for uncoated cisterns in practical applications.