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  (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 . 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  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.
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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 ]