Pumice is a natural pozzolan for improving concrete in critical infrastructure applications. It forms when an underwater volcano spurts molten rock and the lava rushes out into the water column quickly cooling, filling with gas and hardens. The lightweight bubbly rock that rises to the surface is called pumice. 

SCMs improve the density and quality of the concrete matrix by amplifying the production of calcium silicate hydrate (CSH), the cementitious binder that makes concrete, and by consuming deleterious compounds produced by the cement water hydration reaction and otherwise alter OPC chemistry so as to contribute to the concrete’s ability to resist sulfate, chloride, and alkali-silica attacks, heat-of-hydration cracking, freeze-thaw damage.

Application and Uses

As a SCM, pumice pozzolan can mitigate Alkali-Silica Reaction (ASR) in concrete. In its powdered form, pumice can replace up to 50% of Portland cement making it an affordable material and an environmentally friendly alternative to traditional cement and other SCM's including fly ash.  

The Romans discovered the unique characteristics and properties of Pumice in concrete, including longevitiy and durability, evident in their still-standing concrete structures!