Pumice Pozzolan for Concrete Performance

MODERN PORTLAND CEMENT is fast-setting and widely useful. But it has an achilles heel: poor longivity. Almost as soon as standard concrete is placed, it begins to degrade. It’s a matter of chemistry. Studies suggest that only about 75% of the cement powder is converted to Calcium Silicate Hydrate (CSH), which is the chemical binder that makes concrete what it is. The other 25%? It is converted to a by-product compound known as Calcium Hydroxide (CH) that creates a host of problems that have a deleterious effect on the longivity and effective performance of concrete.

The solution? Add a pozzolan. Pozzolans are a class of supplemental cementitious materials that supercharge concrete performance. Pumice, in particular, is an excellent pozzolan. Used at a 15 to 20% replacement rate for Portland cement, the finely ground pumice pozzolan works to drastically reduce, even eliminate, by-product CH by coverting it to CSH. More CSH means more binder. That means more density in the concrete matrix, more long-term strength, less permeability (becomes highly resistant to chemical attacks and freeze-thaw-process damage), reduced heat of hydration cracking, and flatlined alkali silica reaction. All that adds up to high-performance concrete durability.

Extensive information about how pozzolans work, and in particular, how our natural pumice pozzolan works, is available at the HessPozz.com website. You’ll also find summaries of the quantifying research done on the performance of our pozz in concrete and mortar. A small selection of informative PDF documents are also attached below.