natural pumice stone from the Hess Pumice deposit
concrete batch plant
performance-enhanced concrete
pumping pumice-enhanced concrete
precast concrete products can benefit from a pozzolanic boost of pumice powder
pumice aggregate and pumice pozzolan are ideal for cast concrete stone veneer

Pumice and Concrete: Applications and Benefits of Pumice-Enhanced Concrete

Pumice and cement enjoy a very dynamic relationship—a relationship Roman engineers and builders relied on completely. A relationship that worked so well that much of their empire of concrete endures to this day—some 2000 years later. Fact is, the hydrated lime cement they used made a poor concrete by itself. It was only after they added fine-grained pumice [01] (what they called pozzolana), did their concrete achieve its impressive millennia-spanning chemistry. They also employed pumice aggregate when they wanted a lightweight concrete—for example, in the dome of the Pantheon [02]. Even today, in an industry dominated by modern quick-setting Portland cement, pumice still plays a key role in high-performance concretes.


Today’s standard concretes simply aren’t as good as they could be: almost as soon as standard Portland cement concrete is placed, the process of degradation begins. Adding a high-purity natural pumice pozzolan to the concrete formulation mitigates or completely eliminates the problems inherent in standard concrete. ASTM-standards research has shown natural pumice pozzolan provides significant performance increases in terms of appearance, impermeability, longevity, thermal cracking, resistivity to chemical attacks, and compressive strength. [ MORE ]


Alkali-Silica Reaction (ASR) is a relentless infrastructure assassin—there is no way to stop it once such chemically-flawed concrete has been placed. ASR must be mitigated in the concrete mix design by specifying a consistent, quantifiable supplementary cementitious material (SCM) that flatlines the reaction. Clean, naturally calcined pumice from the massive Hess deposit in southeast Idaho USA is ideal: this carefully refined pumice not only delivers proven ASR mitigation in the presence of even highly reactive aggregates, it does so as a percentage of cement replacement while contributing additional durability benefits to the concrete. [ MORE ]

And that’s just the pozzolanic application. Pumice is an ideal lightweight aggregate for specialized form-placed concrete applications that call for less weight and/or insulative qualities.


Pumice concrete has several advantages over conventional concrete in many construction applications—first, and perhaps most significantly, its unique lightweight quality. This trait contributes to a decrease in structural steel costs and, consequently, job costs. Larger volumes of concrete can be handled by lighter equipment with less wear and tear on that equipment. There is also a significant reduction of dead weight on supports and formwork. Second, pumice concrete has superior resistance to harsh weather conditions like freezing and thawing and an R-value some 4-times that of ordinary concrete—making pumice concrete suitable for colder climates and places that experience dramatic changes in the weather. [ MORE ]

PROPERTIES OF HESS PUMICE AGGREGATES—tables with ASTM tests, specifications.

PUMICE CONCRETE MIX DESIGNS— for using pumice concrete as a contentional concrete alternative.

PLACING PUMICE CONCRETE— instructions for mixing and placing pumice concrete.


Pumice-Crete® is a low density, lightweight, low-rise structural concrete using 3/8 pumice aggregate, Portland cement, and water. The honeycomb-like walls are formed and poured at a typical thickness of 18-24 inches, with no additional structural reinforcement [03] or insulation needed. Wall surfaces are finished inside and out with plaster (a pozzolan lime plaster is ideal), further improving the thermal performance of the structure. [ MORE ]


When precast concrete products need to be both lightweight and strong, pumice fits the spec—in the form of aggregate and sand (lightweight) and pozzolan powder (strength and durable density). [ MORE ]


CEMENTITIOUS GROUT—Cement and pumice-blended ultrafine injection grouts are used to economically stabilize and strengthen soils and seal microfractures in rock and concrete structures against inflow or leachate. [ MORE ]

POZZOLAN LIME PLASTER—This simple formulation of water + lime + pumice pozzolan not only out-performs modern plaster equivalents, it stands as an environmentally sound alternative to synthetic stucco and other Portland cement-based products.
[ MORE ]

GLASS FIBER REINFORCED CONCRETE (GFRC) PANELS—With GFRC surfacing panels, the balance between weight, strength, and durability is a delicate one—bright, hard, lightweight Hess pumice aggregate and Hess UltraPozz (superfine pumice pozzolan) make it all work to impressive advantage. [ MORE ]


01—Deep underground, in the fiery heart of a volcano, water mixes with molten rock, pressure builds...finally finding a violent, spectacular release. The trapped water in the viscous, super-heated rock flashes to steam, blasting the magma into a frothy stone that cools, hardens, and falls to the earth as pumice…a foamed-glass stone that is hard yet friable, non-crystalline in structure, and naturally calcined—a combination of characteristics that make pumice powders and aggregates incredibly useful to a variety of industries. [ MORE ABOUT PUMICE ]

02—A little history and a listing of web articles on roman concrete. [ MORE ABOUT ROMAN CONCRETE ]

03—Check with local building codes and consult with a structural engineer.